Visible wavelength light-emitting diodes (LEDs) and laser diodes (LDs) enabled optical wireless communication (OWC) is an emerging technology for realizing high-confidentiality and high-speed point-to-point (PtP), vehicle-to-vehicle, and white-lighting data access links in indoor/outdoor free-space and underwater environments. Notably, OWC facilitates users to access more transmission bandwidth and capacity with physical-layer security and electromagnetic-immunity features by utilizing unlicensed visible optical carriers bands covering from 400 to 800 THz as compared to the commonly employed radio-frequency bands. Hence, a large amount of heavy data exchanging, routing, and streaming traffics can be realized in the current wireless networks. This also reinforces the realistic fusion of optical fiber wireline, radio-frequency wireless, and visible lighting communication networks in the new big-data era. In this paper, developing progress as well as the current trend of visible LED and LD based OWC networks for PtP, white-lighting and underwater applications are overviewed in detail. The performance parameters and figures-of-merits of previously reported OWC systems are summarized for comparison and discussion. Three main scenarios including visible LED based lighting OWC, visible LD enabled PtP communication, and LD based white-light fidelity (“Li-Fi”) are individually discussed and summarized with their allowable data rate, transmission distance, and lighting color temperature and rendering index for comparison. At first, the transmission performances of LED based PtP and white-lighting OWC system with the use of novel data formats, such as pulse amplitude modulation and quadrature amplitude modulation-orthogonal frequency division multiplexing, are surveyed to understand the increasing trend on transmission capacity of LED based OWC system. Owing to the limited bandwidth and data rate of LED based OWC system, the LD has gradually been regarded as a competitive alternative candidate transmitter due to their significantly broadened bandwidth and enhanced data capacity. By taking the aforementioned advantages, studies on the blue/violet LD based white-lighting OWC have recently emerged to demonstrate the substitutability of this technology. The impacts of LD based OWC technology with its state-of-the-art implementation are comprehensively discussed together with prospects for future developments. Undoubtedly, the blue/violet LDs are also a promising transmitter for underwater PtP transmission owing to its extremely low power extinction in water, which has recently emerged as the most intriguing source for undersea exploration and sensing applications.

Electromagnetic (EM) metamaterials are artificially engineered media composed of subwavelength unit cells, which achieve exotic EM properties beyond the limits of natural materials and provide great freedom to manipulate EM waves. Here, we review the recent progress on metamaterials in terms of three aspects: effective medium metamaterials, plasmonic metamaterials, and information metamaterials, respectively. In the first section for the effective medium metamaterials, we summarize the fundamental physics and typical applications such as invisibility cloaks, lenses, antennas, and other passive devices. Tunable, reconfigurable, and active metamaterials are also introduced. In the second section, we review the research progress of single plasmons at optical frequencies, and then present highly efficient excitation methods of spoof surface plasmon polaritons (SPPs) and introduce typical passive and active SPP devices such as waveguides, beam splitters, filters, directional couplers, amplifiers, and second harmonic generators. SPP on-chip components and circuits are also investigated with the remarkable advantages in crosstalk reduction to solve the signal-integrity problem, which has challenged to the microwave devices and integrated circuit technologies for many years. Subsequently, spoof localized surface plasmons (LSPs) having novel resonant modes and potential application in high sensitivity sensors are illustrated. In the third section, we first give a brief introduction of EM metasurfaces as well as their applications in generation of optical vortex beams, holograms, and metalenses, and then give a comprehensive review on the recently proposed information metamaterials, including digital coding metamaterials and field-programmable metamaterials, by taking account of the physical principles and their new functions in real-time manipulation of the EM waves such as anomalous reflections or refractions, radar cross section (RCS) reductions, and beam scanning. We further demonstrate the applications of programmable metamaterials in programmable radar, imaging, wireless communication, and hologram systems. Finally, an outlook of the future directions of metamaterials is offered.

Recent advances in the development of quantum dots (QDs) have offered new possibilities for the exploration of sensors, bio imaging, batteries, electrochemical water splitting and optoelectronic applications because of their intriguing optical, electrical, catalytic and electrochemical properties. Among QDs, atomically thin two-dimensional quantum dots (2D QDs) derived from graphene sheets, transition metal dichalcogenide (TMD) layers and phosphorene have been of considerable interest for the past few years. There have been several intensive studies of carbon QDs, but TMD QDs and heterostructures based on 2D QDs are rapidly advancing. Herein, the synthesis and properties of 2D QDs, particularly carbon and TMD QDs, are reviewed for the recent progress in their application toward electrochemical water splitting, photocatalytic wastewater treatment, supercapacitors, batteries and photodetectors. Moreover, the assembly of such 2D QDs to achieve industrial-scale production and boost their performance in widespread applications is emphasized.

This paper reviews the field of microwave photonics instantaneous frequency measurements (IFM). It aims to consolidate the literature, explains the key implementations and reviews the recent developments. Current photonic IFMs are capable of operating over a wide bandwidth with good resolution. However, their implementations are often based on discrete components and exhibit limited dynamic range and efficiency. Photonic integration and improvements of dynamic range and efficiency are thus necessary, and they are anticipated as future research directions and developments.

The development of the HgCdTe alloy as the most important intrinsic semiconductor for infrared (IR) technology is well established and recognized. In spite of the achievements in material and device quality, the drawbacks still exist due to bulk and surface instability, lower yields and higher costs particularly in fabrication of long wavelength infrared arrays. The difficulties with this material encouraged to research on other compounds to improve device performance. Since the first paper published by Sakaki and Esaki in 1978 it is well known that InAs and GaSb constitute a nearly lattice-matched material system offering great flexibility in the design of IR optoelectronic devices. After four decades, the III-V type-II superlattice (T2SL) detector technology is under strong development as a possible alternative to HgCdTe. The novel ideas coming in design of detectors have enhanced the position of T2SLs in IR materials detector technology. It appears that T2SLs are especially helpful in the design of unipolar barriers. In this paper fundamental physical properties of two material systems, HgCdTe and T2SLs, are compared together with their influence on detector performance: dark current density, RA product, quantum efficiency, and noise equivalent different temperature. In comparison with HgCdTe, fundamental properties of T2SLs are inferior. On the other hand, T2SL and barrier detectors have several advantages to include lower tunnelling and surface leakage currents, and suppressed Auger recombination mechanism. Up to date, the promise of superior performance of these detectors has not been realized yet. In the paper we present that the performance of T2SL detectors (dark current, current responsivity, and noise equivalent difference temperature) is lower than bulk HgCdTe photodiodes. Due to stronger, less ionic chemical bonding of III-V semiconductors, these materials are attractive due to manufacturability and stability. It is also predicted that the interband T2SL quantum cascade devices will outperform the performance of the high operating temperature HgCdTe detectors.

Cr Colquiriite laser materials (Cr:LiCAF, Cr:LiSAF, Cr:LiSGaF) own broad absorption bands in the visible region that allow direct-diode pumping by well-developed low-cost red diodes. Moreover, they possess broad emission bands in the near infrared that enable widely tunable laser operation (720-1110 nm), and generation of sub-10-fs light pulses via mode-locking. Furthermore, Cr: Colquiriite crystals can be grown with a very low loss level of 0.2%/cm, which enables the construction of high-Q-cavities, resulting in lasing thresholds below 1 mW, and slope efficiencies above 50%. High-Q-cavities constructed with Cr: Colquiriites could store large amount of intracavity laser powers which is off great interest: (i) for increasing the efficiency of intracavity nonlinear processes such as intracavity frequency-doubling, and (ii) for minimizing laser noise such as timing jitter noise in femtosecond operation. However, thermally and mechanically Cr: Colquiriites have glass like properties. Hence, average power scaling has been challenging in the cw and femtosecond Cr: Colquiriite lasers, as well as in their amplifiers. In this paper, we will review research efforts over the last decades, in developing robust, low-cost, highly-efficient, and tunable cw and femtosecond laser sources based on diode-pumped Cr:Colquiriite gain media. Challenges for future progress have also been discussed.

Development of Si photonic integrated circuits (PICs) has been impeded due to lack of efficient Si-based light-emitting sources. Because of their indirect bandgap, bulk Ge and Si are very inefficient at emitting light. Therefore, direct-bandgap III-V semiconductors have been extensively exploited for the active region of the lasers for PICs. Heterogeneous and monolithic integration of III-V semiconductor components on Si platforms have been considered as promising solutions to achieve practical on-chip light-emitting sources for Si photonics. This paper reviews the latest developments on telecommunication wavelength III-V lasers integrated on Si substrates, in terms of integration methods and laser performance.

The optical microresonators reviewed in this paper are called bottle microresonators because their profile often resembles an elongated spheroid or a microscopic bottle. These resonators are commonly fabricated from an optical fiber by variation of its radius. Generally, variation of the bottle microresonator (BMR) radius along the fiber axis can be quite complex presenting, e.g., a series of coupled BMRs positioned along the fiber. Similar to optical spherical and toroidal microresonators, BMRs support whispering gallery modes (WGMs) which are localized inside the resonator due to the effect of total internal reflection. The elongation of BMRs along the fiber axis enables their several important properties and applications not possible to realize with other optical microresonators. The paper starts with the review of the BMR theory, which includes their spectral properties, slow WGM propagation along BMRs, theory of Surface Nanoscale Axial Photonics (SNAP) BMRs, theory of resonant transmission of light through BMR microresonators coupled to transverse waveguides (microfibers), theory of nonstationary WGMs in BMRs, and theory of nonlinear BMRs. Next, the fabrication methods of BMRs including melting of optical fibers, fiber annealing in SNAP technology, rolling of semiconductor bilayers, solidifying of a UV-curable adhesive, and others are reviewed. Finally, the applications of BMRs which either have been demonstrated or feasible in the nearest future are considered. These applications include miniature BMR delay lines, BMR lasers, nonlinear BMRs, optomechanical BMRs, BMR for quantum processing, and BMR sensors.

Plasmons, the electromagnetic excitations coupled with electron waves, possess the intrinsic ability of manipulating light at subwavelength scales down to picometer. This ability not only helps uncovering the fascinating quantum behaviors that strengthen the basic understanding of quantum science, but also enables the inventions of various quantum optoelectronic devices, triggering the birth of quantum plasmonic technology. The past decade has witnessed the flourishing of this technology. In this review, we first focus on fundamental investigations into quantum behaviors for both “isolated” plasmonic nanostructures and “coupled” plasmon-emitter systems, emphasizing new theoretical frameworks and experimental advances. Leveraging on these fundamentals, the progress in exploring and applying quantum plasmonic devices is discussed, such as quantum plasmonic circuits, nanolasers, biochemistry, and spin-orbit interaction devices. Upon summarizing the past and present developments, the future research directions and promising applications are highlighted.

The applications of light absorbers concern photodetectors, optical filters, solar applications or flexible electronics. In this review, we will detail the application of such light absorbers and we will develop the main demonstrations of the use of metallic nanoparticles embedded within a host matrix to fabricate coatings aiming at harvesting light. We will explain how chemically synthetized silver nanoparticles of various shapes (spheres, cubes, …) and sizes allow controlling the optical properties of heterogeneous thin film layers. By coupling the optical characterizations with computer modeling, we will describe how the nanoparticles behave both individually and collectively. To control reflected and absorbed light by thin film layers containing nanoparticles several points have to be addressed: the relation between the shape of the nanoparticle and the absorptance of the layer, the interaction of light between nanoparticles and the collective behavior of aggregates.

In this review, we describe dielectric properties of biological tissues and liquids in the context of terahertz (THz) biophotonics. We discuss a model of the THz dielectric permittivity of water and water-containing media, which yields analysis of the relaxation and damped resonant molecules modes. We briefly describe modern techniques of THz spectroscopy and imaging employed in biophotonics with a strong emphasize on a THz time-domain spectroscopy. Furthermore, we consider the methods of sub-wavelength resolution THz imaging and the problem of THz wave delivery to hard to access tissues and internal organs. We consider the THz dielectric properties of biological solutions and liquids. Although strong absorption by water molecules prevents THz-waves from penetration of hydrated tissues and probing biological molecules in aqueous solutions, we discuss approaches for overcoming these drawbacks – novel techniques of freezing and temporal dehydration by application of hyperosmotic agents which have a potential for cancer detection. We review recent applications of THz technology in diagnosis of malignancies and aiding histology paying particular attention to the origin of contrast observed between healthy and pathological tissues. We consider recent applications of THz reflectometry in sensing the thinning dynamics of human pre-corneal tear film. Modern modalities of THz imaging, which relies on the concepts of multi-spectral and multi-temporal domains and employing the principles of color vision, phase analysis and tomography are discussed. Novel methods of THz spectra analysis based on machine learning, pattern recognition, chemical imaging and the revealing of the spatial distribution of various substances in a tissue, are analyzed. Advanced thermal model describing biological object irradiated by THz waves and phantoms mimicking the optical properties of tissues at THz frequencies are presented. Finally, application of the high-resolution THz spectroscopy in analytic chemistry, biology and medicine are described.

Since the first observation of stimulated emission from colloidal quantum dots (CQDs) in year 2000, tremendous progress has been made in developing solution-processed lasers from colloidal semiconductor nanostructures in terms of both understanding the fundamental physics and improving the device performance. In this review paper, we will start with a brief introduction about the fabrication of CQDs and the corresponding electronic structures. The emphasis will be put on the discussion about the optical gain and lasing from colloidal nanostructures including the gain mechanism, the main hurdles against optical gain and lasing as well as strategies to optimize the lasing performance. Afterwards, the recent advances in CQD lasers, exemplified by the achievement of continuous wave lasing, will be presented. Finally, the challenges and a perspective of the future development of lasers based on the colloidal semiconductor nanostructures will be presented.

Intriguing intrinsic properties of light quanta and related topics are reviewed by emphasizing the self-consistency of light-matter interactions and open nano-systems dynamics. It is pointed out that there still remain fundamental and challenging issues related to quantization of a finite nano-system interacting with a massive (i.e., localized) photon field,as well as with a hierarchical or structured phonon field. By using theoretical frameworks developed for an infinite system, some of quantum nature of a finite nano-system are revealed, and it is theoretically shown that dynamic phonon environments and the interplay of coherent and incoherent phonons play an important role in quantum coherent dynamics of electron-hole pairs interacting with massive photon fields.

Ideal integrated light emitters for optical interconnects should be compact in size, high in modulation bandwidth, efficient in energy consumption and tunable in frequency. Nanolasers are excellent candidates for such an application. In this article, we review and offer further in-depth analyses in three key aspects of recent nanolaser research, including second order intensity correlation, g2(τ), characterizations, direct modulation and electromagnetic isolation in a dual nanolaser system. For coherence characterization, we review a technique exploiting not only the photon bunching peak, but also the g2(τ) pulse width to determine the spontaneous emission (SE), amplified SE and lasing regimes of a nanolaser with a high SE factor, β. We show that this technique is applicable for lasers with β′s ranging from 10−5 to unity. Additionally, we demonstrate the first direct current modulation of an electrically pumped metallo-dielectric nanolaser (MDNL) at 30 MHz. Considering the viability of nanolasers for dense integration, we then review the electromagnetic coupling between two closely spaced MDNLs and identify two practical methods to eliminate such coupling. Lastly, we review the state-of-the-art development in and offer future perspectives on three other important areas of nanolaser research ― integration with silicon photonics, wide-range frequency tuning and dual nanolaser dynamics.

Combustion is one of the most dominant energy conversion processes used in all areas of human life, but global concerns over exhaust gas pollution and greenhouse gas emission have stimulated further development of the process. Lean combustion and exhaust gas recirculation are approaches to improve the efficiency and to reduce pollutant emissions; however, such measures impede reliable ignition when applied to conventional ignition systems. Therefore, alternative ignition systems are a focus of scientific research. Amongst others, laser induced ignition seems an attractive method to improve the combustion process. In comparison with conventional ignition by electric spark plugs, laser ignition offers a number of potential benefits. Those most often discussed are: no quenching of the combustion flame kernel; the ability to deliver (laser) energy to any location of interest in the combustion chamber; the possibility of delivering the beam simultaneously to different positions, and the temporal control of ignition. If these advantages can be exploited in practice, the engine efficiency may be improved and reliable operation at lean air-fuel mixtures can be achieved, making feasible savings in fuel consumption and reduction in emission of exhaust gasses. Therefore, laser ignition can enable important new approaches to address global concerns about the environmental impact of continued use of reciprocating engines in vehicles and power plants, with the aim of diminishing pollutant levels in the atmosphere. The technology can also support increased use of electrification in powered transport, through its application to ignition of hybrid (electric-gas) engines, and the efficient combustion of advanced fuels. In this work, we review the progress made over the last years in laser ignition research, in particular that aimed towards realizing laser sources (or laser spark plugs) with dimensions and properties suitable for operating directly on an engine. The main envisaged solutions for positioning of the laser spark plug, i.e. placing it apart from or directly on the engine, are introduced. The path taken from the first solution proposed, to build a compact laser suitable for ignition, to the practical realization of a laser spark plug is described. Results obtained by ignition of automobile test engines, with laser devices that resemble classical spark plugs, are specifically discussed. It is emphasized that technological advances have brought this method of laser ignition close to the application and installation in automobiles powered by gasoline engines. Achievements made in the laser ignition of natural gas engines are outlined, as well as the utilization of laser ignition in other applications. Scientific and technical advances have allowed realization of laser devices with multiple (up to four) beam outputs, but many other important aspects (such as integration, thermal endurance or vibration strength) are still to be solved. Recent results of multi-beam ignition of a single-cylinder engine in a test bench set-up are encouraging and have led to increased research interest in this direction. A fundamental understanding of the processes involved in laser ignition is crucial in order to exploit the technology's full potential. Therefore, several measurement techniques, primarily optical types, used to characterize the laser ignition process are reviewed in this work.

GaN is a great material for making optoelectronic devices in the blue, blue-violet and green bands. Vertical-cavity surface-emitting lasers (VCSELs) have many advantages including small footprint, circular symmetry of output beam, two-dimensional scalability and/or addressability, surface-mount packaging, good price-performance ratio, and simple optics/alignment for output coupling. In this paper, we would like to (1) Review the design and fabrication of GaN-based VCSELs including some technology challenges, (2) Discuss the design and metalorganic chemical vapor deposition (MOCVD) growth of electrically pumped blue VCSELs and (3) Demonstrate world first green VCSEL using quantum dots (QDs) active region to overcome the 'green gap'.

For over half a century, laser technology has undergone a technological revolution. These technologies, particularly semiconductor lasers, are employed in a myriad of fields. Optical medical diagnostics, one of the emerging areas of laser application, are on the forefront of application around the world. Optical methods of non- or minimally invasive bio-tissue investigation offer significant advantages over alternative methods, including rapid real-time measurement, non-invasiveness and high resolution (guaranteeing the safety of a patient). These advantages demonstrate the growing success of such techniques. In this review, we will outline the recent status of laser technology applied in the biomedical field, focusing on the various available approaches, particularly utilising compact semiconductor lasers. We will further consider the advancement and integration of several complimentary biophotonic techniques into single multimodal devices, the potential impact of such devices and their future applications. Based on our own studies, we will also cover the simultaneous collection of physiological data with the aid a multifunctional diagnostics system, concentrating on the optimisation of the new technology towards a clinical application. Such data is invaluable for developing algorithms capable of delivering consistent, reliable and meaningful diagnostic information, which can ultimately be employed for the early diagnosis of disease conditions in individuals from around the world.

Optical Coherent Multidimensional Spectroscopy (CMDS) has been developed to probe the electronic states of a diverse range of complex systems. The great advantage of CMDS over linear spectroscopy is the ability to separate and quantify different types of interactions. To do this, multiple carefully controlled femtosecond laser pulses drive a non-linear response in the sample. A specific component of this non-linear response is selected and its amplitude and phase measured. There are many challenges for the experimental realization of optical CMDS, yet there have been several different approaches developed, each with their own advantages and limitations. Identifying the best approach then becomes dependent on the sample and the information being sought. Here we review the various experimental considerations and different approaches that have been developed. We consider the advantages and limitations of each of these, specifically in the context of experiments on solid state systems such as semiconductor nanostructures and 2D atomically thin materials. Two important considerations that are difficult to compare independently of other extraneous factors are the stability and sensitivity of the system. Here, we describe the experimental implementation of two different approaches that experience otherwise identical conditions and present an unbiased comparison of the stability and sensitivity. Furthermore, we demonstrate that by merging these two approaches we are able to combine the advantages of both into a single experiment.

We review recent research on nonlinear optical interactions in optical-fiber nanowires (OFNs) with sub-micron transverse dimensions. Such OFNs, which are fabricated from standard optical fibers, offer numerous beneficial optical and mechanical properties, including strong evanescent fields, high flexibility and configurability, a small mass, and low-loss interconnection to other optical fibers and fiberized components. In particular, the strong confinement of light enables a large enhancement of nonlinear interactions and group-velocity dispersion engineering. The combination of these properties makes OFNs ideal for many nonlinear optical applications, including harmonic generation, Brillouin scattering, four-wave mixing, supercontinuum generation, and optomechanics. With the incorporation of new materials, OFNs should be ideally suited for a host of nonlinear optical interactions and devices and offer great potential in miniature fiber devices for optical telecommunications and optical sensor applications.

The topological phase of matter, originally proposed and first demonstrated in fermionic electronic systems, has drawn considerable research attention in the past decades due to its robust transport of edge states and its potential with respect to future quantum information, communication, and computation. Recently, searching for such a unique material phase in bosonic systems has become a hot research topic worldwide. So far, many bosonic topological models and methods for realizing them have been discovered in photonic systems, acoustic systems, mechanical systems, etc. These discoveries have certainly yielded vast opportunities in designing material phases and related properties in the topological domain. In this review, we first focus on some of the representative photonic topological models and employ the underlying Dirac model to analyze the edge states and geometric phase. On the basis of these models, three common types of two-dimensional topological photonic systems are discussed: 1) photonic quantum Hall effect with broken time-reversal symmetry; 2) photonic topological insulator and the associated pseudo-time-reversal symmetry-protected mechanism; 3) time/space periodically modulated photonic Floquet topological insulator. Finally, we provide a summary and extension of this emerging field, including a brief introduction to the Weyl point in three-dimensional systems.

This article reviews recent progress in theoretical studies of dressed photons. For providing concrete physical images of dressed photons, several experimental studies are demonstrated. They are applications of dressed photons to novel optical functional devices, nano-fabrication technologies, energy conversion technologies, and photon breeding devices. After these experimental demonstrations, as the main part of this review, quantum-field theoretical formulation of dressed photons is attempted in use of the newly introduced Clebsch-dual variable of electromagnetic field. The reason for introducing the new formulation will be explained in the final section from the viewpoint to exhibit the contrast between free and interacting quantum fields in regard to their energy-momentum supports which are seldom touched upon (or forgotten) in the common physical discussions about quantum fields.

The lack of wireless spectrum in the radio frequency bands has led to a rapid growth in research in wireless networking using light, known as LiFi (light fidelity). In this paper an overview of the subsystems, challenges and techniques required to achieve this is presented.

For over 55 years, laser technology has expanded from laboratory research to widespread fields, for example telecommunication and data storage amongst others. Recently application of lasers in biology and medicine presents itself as one of the emerging areas. In this review, we will outline the recent advances in using lasers for the generation of singlet oxygen, traditionally used to kill tumour cells or induce thrombotic stroke model due to damage vascular effects. Over the last two decade, completely new results on cerebrovascular effects of singlet oxygen generated during photodynamic therapy (PDT) have been shown alongside promising applications for delivery of drugs and nanoparticles into the brain for therapy of brain cancer. Furthermore, a “gold key” has been found to overcome the limitations of PDT, such as low light penetration and high toxicity of photosensitizers, by direct generation of singlet oxygen using quantum-dot laser diodes emitting in the near infrared (NIR) spectral range. It is our motivation to highlight these pioneering results in this review, to improve understanding of the biological role of singlet oxygen and to provide new perspectives for improving clinical application of laser based therapy in further research.

The distributed quantum network, in which nodes comprising small but well-controlled quantum states are entangled via photonic channels, has in recent years emerged as a strategy for delivering a range of quantum technologies including secure communications, enhanced sensing and scalable quantum computing. Colour centres in diamond are amongst the most promising candidates for nodes fabricated in the solid-state, offering potential for large scale production and for chip-scale integrated devices. In this review we consider the progress made and the remaining challenges in developing diamond-based nodes for quantum networks. We focus on the nitrogen-vacancy and silicon-vacancy colour centres, which have demonstrated many of the necessary attributes for these applications. We focus in particular on the use of waveguides and other photonic microstructures for increasing the efficiency with which photons emitted from these colour centres can be coupled into a network, and the use of microcavities for increasing the fraction of photons emitted that are suitable for generating entanglement between nodes.

Interaction between light and materials is essential in the physics underlying all optical devices, including light emitting devices such as light emitting diodes and lasers, photo-voltaic devices, and photo-synthesis systems. The demand for higher light utilization efficiency is becoming increasingly important for advanced optical devices. This is because, when feature size is smaller than the incident light wavelength, photons cannot couple with devices efficiently. In this paper, we review recent progress regarding a unique phenomenon at the nano scale and its applications. First, we summarize the development of light–matter interactions at the nano-scale. Second, we review recent theoretical works focusing on optical near fields in which unique phenomena arise from non-uniform optical fields. We then review several recent developments based on the near-field effect, including artificial photosynthesis and near-field etching for realization of angstrom-scale fattened surfaces. Finally, we discuss the future outlook for these technologies.

Quantum optics is the study of the intrinsically quantum properties of light. During the second part of the 20th century experimental and theoretical progress developed together; nowadays quantum optics provides a testbed of many fundamental aspects of quantum mechanics such as coherence and quantum entanglement. Quantum optics helped trigger, both directly and indirectly, the birth of quantum technologies, whose aim is to harness non-classical quantum effects in applications from quantum key distribution to quantum computing. Quantum light remains at the heart of many of the most promising and potentially transformative quantum technologies. In this review, we celebrate the work of Sir Peter Knight and present an overview of the development of quantum optics and its impact on quantum technologies research. We describe the core theoretical tools developed to express and study the quantum properties of light, the key experimental approaches used to control, manipulate and measure such properties and their application in quantum simulation, and quantum computing.

Sir Peter Knight is a pioneer in quantum optics which has now grown to an important branch of modern physics to study the foundations and applications of quantum physics. He is leading an effort to develop new technologies from quantum mechanics. In this collection of essays, we recall the time we were working with him as a postdoc or a PhD student and look at how the time with him has influenced our research.

Perovskite solar cell research has been attracting increasing attention in recent years. In this review paper, we will provide an overview of the recent developments in terms of material composition, deposition techniques, and the device architecture (the choice of charge transport layers and electrodes). Then, we will critically discuss some of the major problems, namely device stability, hysteresis, environmental implications due to the presence of a toxic metal (lead), and difficulties in fabrication of large area and/or flexible devices. In addition, we will also discuss tandem cells and modules, as well as the application of perovskites in other devices and the integration of perovskite solar cells with other devices. Finally, we discuss future outlook and important issues which need to be addressed for the wide scale applications of these devices. Lifetime and stability are identified as the key issue to be addressed for wide scale applications, and the majority of environmental impact is due to the use of organic solvents or other components in the device, not the lead-containing perovskite absorber. The standardisation of the testing conditions and more studies involving outdoor testing are needed for convincing demonstrations of good stability as opposed to dark storage testing. Another key issue is upscaling and reproducibility of the film preparation, which can be problematic due to high sensitivity of the perovskite film to the processing conditions. To overcome these obstacles multilaboratory collaborative efforts would be highly desirable.

The essential functionality of photonic and electronic devices is contained in thin surface layers leaving the substrate often to play primarily a mechanical role. Layer transfer of optimised devices or materials and their heterogeneous integration is thus a very attractive strategy to realise high performance, low-cost circuits for a wide variety of new applications. Additionally, new device configurations can be achieved that could not otherwise be realised. A range of layer transfer methods have been developed over the years including epitaxial lift-off and wafer bonding with substrate removal. Recently, a new technique called transfer printing has been introduced which allows manipulation of small and thin materials along with devices on a massively parallel scale with micron scale placement accuracies to a wide choice of substrates such as silicon, glass, ceramic, metal and polymer. Thus, the co-integration of electronics with photonic devices made from compound semiconductors, silicon, polymer and new 2D materials is now achievable in a practical and scalable method. This is leading to exciting possibilities in microassembly. We review some of the recent developments in layer transfer and particularly the use of the transfer print technology for enabling active photonic devices on rigid and flexible foreign substrates.

This paper will review the coupling by stimulated Raman scattering between two laser fields and its dependence on the spectral properties of those fields. We describe the coupling in terms of an effective Raman gain that depends on the fields’ linewidths, the material dispersion, and specific experimental conditions. The aim is to provide an intuitive understanding of this behaviour, by presenting analytic and numerical results in both the time- and frequency-domains. We review some recent experimental results using crystalline Raman materials, to highlight why spectral effects must be taken into consideration to push crystalline Raman lasers to new extremes of performance.

Adhesion is a critical cellular process that contributes to migration, apoptosis, differentiation, and division. It is followed by the redistribution of cellular materials at the cell membrane or at the cell-surface interface for cells interacting with surfaces, such as basement membranes. Dynamic and quantitative tracking of changes in cell adhesion mass redistribution is challenging because cells are rapidly moving, inhomogeneous, and nonequilibrium objects, whose physical and mechanical properties are difficult to measure or predict. Here, we report a novel biosensor based microscopy approach termed Photonic Crystal Enhanced Microscopy (PCEM) that enables the movement of cellular materials at the plasma membrane of individual live cells to be dynamically monitored and quantitatively imaged. PCEM utilizes a photonic crystal biosensor surface, which can be coated with arbitrary extracellular matrix materials to facilitate cellular interactions, within a modified brightfield microscope with a low intensity non-coherent light source. Benefiting from the high sensitivity, narrow resonance peak, and tight spatial confinement of the evanescent field atop the photonic crystal biosensor, PCEM enables label-free live cell imaging with high sensitivity and high lateral and axial spatial-resolution, thereby allowing dynamic adhesion phenotyping of single cells without the use of fluorescent tags or stains. We apply PCEM to investigate adhesion and the early stage migration of different types of stem cells and cancer cells. By applying image processing algorithms to analyze the complex spatiotemporal information generated by PCEM, we offer insight into how the plasma membrane of anchorage dependent cells is dynamically organized during cell adhesion. The imaging and analysis results presented here provide a new tool for biologists to gain a deeper understanding of the fundamental mechanisms involved with cell adhesion and concurrent or subsequent migration events.

Photon management is essential in improving the performances of optoelectronic devices including light emitting diodes, solar cells and photo detectors. Beyond the advances in material growth and device structure design, photon management via nanoscaled phenomena have also been demonstrated as a promising way for further modifying/improving the device performance. The accomplishments achieved by photon management via nanoscaled phenomena include strain-induced polarization field management, crystal quality improvement, light extraction/harvesting enhancement, radiation pattern control, and spectrum management. In this review, we summarize recent development, challenges and underlying physics of photon management in GaN-based light emitting diodes and solar cells.

The interest in Infrared and Ultraviolet detectors has increased immensely due to the emergence of important applications over a wide range of activities. Detectors based on free carrier absorption known as Hetero-junction Interfacial Workfunction Internal Photoemission (HEIWIP) detectors and variations of these heterojunction structures to be used as intervalence band detectors for a wide wavelength region are presented. Although this internal photoemission concept is valid for all semiconductor materials systems, using a well-studied III–V system of GaAs/Alx Ga1-xAs to cover a wide wavelength range from UV to far-infrared (THz) is an important development in detector technology. Using the intervalence band (heavy hole, light hole and split off) transitions for high operating temperature detection of mid Infrared radiation is also discussed. A promising new way to extend the detection wavelength threshold beyond the standard threshold connected with the energy gap in a GaAs/Alx Ga1-xAs system is also presented. Superlattice detector technology, which is another promising detector architecture, can be optimized using both Type I and Type II heterostructures. Here the focus will be on Type II Strained Layer (T2SL) Superlattice detectors. T2SL Superlattices based on InAs/(In,GA)Sb have made significant improvements demonstrating focal plane arrays operating around 80 K and with multiple band detection capability. A novel spectroscopic method to evaluate the band offsets of both heterojunction and superlattice detectors is also discussed.

In the last decade, new strategies to achieve high-operating temperature (HOT) detectors have been proposed, including barrier structures such as nBn devices, unipolar barrier photodiodes, and multistage (cascade) infrared detectors. The ability to tune the positions of the conduction and valence band edges independently in a broken-gap type-II superlattices is especially helpful in the design of unipolar barriers. This idea has been also implemented in HgCdTe ternary material system. However, the implementation of this detector structure in HgCdTe material system is not straightforward due to the existence of a valence band discontinuity (barrier) at the absorber–barrier interface. In this paper we present status of HgCdTe barrier detectors with emphasis on technological progress in fabrication of MOCVD-grown HgCdTe barrier detectors achieved recently at the Institute of Applied Physics, Military University of Technology. Their performance is comparable with state-of-the-art of HgCdTe photodiodes. From the perspective of device fabrication their important technological advantage results from less stringent surface passivation requirements and tolerance to threading dislocations.

The field of optically pumped planar waveguide lasers has seen a rapid development over the last two decades driven by the requirements of a range of applications. This sustained research effort has led to the demonstration of a large variety of miniature highly efficient laser sources by combining different gain media and resonator geometries. One of the most attractive features of waveguide lasers is the broad range of regimes that they can operate, spanning from continuous wave and single frequency through to the generation of femtosecond pulses. Furthermore, their technology has experienced considerable advances to provide increased output power levels, deriving benefits from the relative immunity from the heat generated in the gain medium during laser operation and the use of cladding-pumped architectures. This second part of the review on optically pumped planar waveguide lasers provides a snapshot of the state-of-the-art research in this field in terms of gain materials, laser system designs, and as well as a perspective on the status of their application as real devices in various research areas.

Optical signal processing has long been recognized as a promising route to a new class of fast and energy efficient devices. The former parameter, the speed, has indeed been addressed in a number of different signal processing roles, confirming the superiority of optical signal processing devices with respect to their electronic counterpart. After gaining some maturity, the field has now advanced to reducing the energy consumption. In this regard, new efforts are directed toward designing an efficient photon interaction mediator, expected to provide both fast and energy efficient devices. The key topic of this review is the progress in longitudinal silica fiber dispersion engineering enabling efficient, non-reciprocal parametric mixers. We present how longitudinal dispersion fluctuations, once considered detrimental, can now be exploited to alter the phase matching condition, and thus, enable fast control of a high power beam by few photons. The potential of such a functionality in high-speed optical signal processing and sensing is discussed.

Group-III nitride nanowire structures, including GaN, InN, AlN and their alloys, have been intensively studied in the past decade. Unique to this material system is that its energy bandgap can be tuned from the deep ultraviolet (~6.2 eV for AlN) to the near infrared (~0.65 eV for InN). In this article, we provide an overview on the recent progress made in III-nitride nanowire optoelectronic devices, including light emitting diodes, lasers, photodetectors, single photon sources, intraband devices, solar cells, and artificial photosynthesis. The present challenges and future prospects of III-nitride nanowire optoelectronic devices are also discussed.

Recent developments in laser sources operating in the mid-IR (3–8μm ) have been motivated by the numerous possibilities for both fundamental and applied research. One example is the ability to unambiguously detect pollutants and carcinogens due to the much larger oscillator strengths of their absorption features in the mid-IR spectral region compared with the visible. Broadband sources are of particular interest for spectroscopic applications since they remove the need for arduous scanning or several lasers and allow simultaneous use of multiple absorption features thus increasing the confidence level of detection. In addition, sources capable of producing ultrashort and intense mid-IR radiation are gaining relevance in attoscience and strong-field physics due to wavelength scaling of re-collision based processes. In this paper we review the state-of-the-art in sources of coherent, pulsed mid-IR radiation. First we discuss semi-conductor based sources which are compact and turnkey, but typically do not yield short pulse duration. Mid-IR laser gain material based approaches will be discussed, either for direct broadband mid-IR lasers or as narrowband pump lasers for parametric amplification in nonlinear crystals. The main part will focus on mid-IR generation and amplification based on parametric frequency conversion, enabling highest mid-IR peak power pulses. Lastly we close with an overview of nonlinear post-compression techniques, for decreasing pulse duration to the sub-2-optical-cycle regime.

Tunable single mode pulsed dye lasers are capable of generating optical radiations in the visible range having very small bandwidths (transform limited), high average power (a few kW) at a high pulse repetition rate (a few tens of kHz), small beam divergence and relatively higher efficiencies. These dye lasers are generally utilized laser dyes dissolved in solvents such as water, heavy water, ethanol, methanol, etc. to provide a rapidly flowing gain medium. The dye laser is a versatile tool, which can lase either in the continuous wave (CW) or in the pulsed mode with pulse duration as small as a few tens of femtoseconds. In this review, we have examined the several cavity designs, various types of gain mediums and numerous types of dye cell geometries for obtaining the single longitudinal mode pulsed dye laser. Different types of cavity configuration, such as very short cavity, short cavity with frequency selective element and relatively longer cavity with multiple frequency selective elements were reviewed. These single mode lasers have been pumped by all kinds of pumping sources such as flash lamps, Excimer, Nitrogen, Ruby, Nd:YAG, Copper Bromide and Copper Vapor Lasers. The single mode dye lasers are either pumped transversely or longitudinally to the resonator axis. The pulse repletion rate of these pump lasers were ranging from a few Hz to a few tens of kHz. Physics technology and engineering aspects of tuning mechanism, mode hop free scanning and dye cell designs are also presented in this review. Tuning of a single mode dye laser with a resolution of a few MHz per step is a technologically challenging task, which is discussed here.

The development of parametric devices down-converting the laser frequency to the mid-infrared (3–30 µm) based on non-oxide nonlinear optical crystals is reviewed. Such devices, pumped by solid-state laser systems operating in the near-infrared, fill in this spectral gap where no such lasers exist, on practically all time scales, from continuous-wave to femtosecond regime. All important results obtained so far with difference-frequency generation, optical parametric oscillation, generation and amplification are presented in a comparative manner, illustrating examples of recent achievements are given in more detail, and some special issues such as continuum and frequency comb generation or pulse shaping are also discussed. The vital element in any frequency-conversion process is the nonlinear optical crystal and this represents one of the major limitations for achieving high energies and average powers in the mid-infrared although the broad spectral tunability seems not to be a problem. Hence, an overview of the available non-oxide nonlinear optical materials, emphasizing new developments such as wide band-gap, engineered (mixed), and quasi-phase-matched crystals, is also included.

A review of authors’ contributions to dye-doped cholesteric liquid crystal (CLC) lasers started from the pioneer authors’ paper of 1980 in which the experimental realization of the first CLC laser is presented. Both distributed feedback (DFB) and photonics band edge lasing models are discussed for different experimental conditions. A detailed study and analysis of basic characteristics of steroidal CLC lasers with low liquid crystal optical birefringence is considered with respect to the DFB model. The manifestation of a planar texture quality and mutual orientations of directors on the substrates influencing on the lasing characteristics in steroidal CLCs have been shown and described. The reversible phototuning of the CLC laser wavelength by trans–cis transitions of photoactive components is realized. Reasons for two theoretical models׳ coexistence for the description of dye-doped CLC lasing is considered.

Controlling light interactions with matter on the nanometer scale provides for compelling opportunities for modern technology and stretches our understanding and exploitation of applied physics, electronics, and fabrication science. The smallest size to which light can be confined using standard optical elements such as lenses and mirrors is limited by diffraction. Plasmonic nanostructures have the extraordinary capability to control light beyond the diffraction limit through an unique phenomenon called the localized plasmon resonance. This remarkable capability enables unique prospects for the design, fabrication and characterization of highly integrated photonic signal-processing systems, nanoresolution optical imaging techniques and nanoscale electronic circuits. This paper summarizes the basic principles and the main achievements in the practical utilization of plasmonic effects in nanoparticles. Specifically, the paper aims at highlighting the major contributions of nanoparticles to nanoscale temperature monitoring, modern “drug free” medicine and the application of nanomaterials to a new generation of opto-electronics integrated circuits.

This review aims at providing a comprehensive and updated picture of the field of hyperbolic metamaterials, from the foundations to the most recent progresses and future perspectives. The topics discussed embrace theoretical aspects, practical realization and key challenges for applications such as imaging, spontaneous emission engineering, thermal, active and tunable hyperbolic media.

Plasmonic quasicrystals consisting of quasi-periodic metal–dielectric patterns offer several advantages compared to the periodic patterns or plasmonic crystals. This paper reviews the present status in theoretical design, modeling, fabrication and basic and applied results on plasmonic quasicrystals. In addition to the current status, possible future prospects of plasmonic quasicrystals are also discussed.

Spectrum-splitting photovoltaics is an alternative to multi-junction tandem cells which has been the subject of renewed interest in recent years as researchers try to push the limits of efficiency and cost-reduction for solar energy production. A myriad of solutions have been proposed for the spectrum-splitting optics, yet the basic cell technologies for these systems have received comparatively little attention. This paper reports on and reviews the most recent progress on a fundamentally different approach to cell design and fabrication: that of Monolithically-Integrated Laterally-Arrayed Multi-Band gap (MILAMB) solar cells. The essence of this concept is to fabricate multiple cells simultaneously on a single substrate using composition-graded semiconductor alloy nanowires to simplify the process, cut costs, and eventually achieve high efficiencies. After a brief introduction and overview of the existing approaches to spectrum-splitting photovoltaics, we present results of theoretical design and numerical studies using two candidate materials, CdPbS and InGaN. These design studies show that the MILAMB cells are capable of similar efficiency levels to those of multi-junction tandem cells, with potentially much reduced cost. Proof-of-concept two-subcell devices fabricated simultaneously on a single substrate using CdSSe nanowire ensembles are reviewed. Their performance is compared to similar thin-film cells to illustrate the current limits and potential benefits of this new approach. Finally, future challenges and possible directions for developing a practical MILAMB system are outlined.

The advances in lasers, electronic and photonic integrated circuits (EPIC), optical interconnects as well as the modulation techniques allow the present day society to embrace the convenience of broadband, high speed internet and mobile network connectivity. However, the steep increase in energy demand and bandwidth requirement calls for further innovation in ultra-compact EPIC technologies. In the optical domain, advancement in the laser technologies beyond the current quantum well (Qwell) based laser technologies are already taking place and presenting very promising results. Homogeneously grown quantum dot (Qdot) lasers and optical amplifiers, can serve in the future energy saving information and communication technologies (ICT) as the work-horse for transmitting and amplifying information through optical fiber. The encouraging results in the zero-dimensional (0D) structures emitting at 980 nm, in the form of vertical cavity surface emitting laser (VCSEL), are already operational at low threshold current density and capable of 40 Gbps error-free transmission at 108 fJ/bit. Subsequent achievements for lasers and amplifiers operating in the O-, C-, L-, U-bands, and beyond will eventually lay the foundation for green ICT. On the hand, the inhomogeneously grown quasi 0D quantum dash (Qdash) lasers are brilliant solutions for potential broadband connectivity in server farms or access network. A single broadband Qdash laser operating in the stimulated emission mode can replace tens of discrete narrow-band lasers in dense wavelength division multiplexing (DWDM) transmission thereby further saving energy, cost and footprint. We herein reviewed the1 progress of both Qdots and Qdash devices, based on the InAs/InGaAlAs/InP and InAs/InGaAsP/InP material systems, from the angles of growth and device performance. In particular, we discussed the progress in lasers, semiconductor optical amplifiers (SOA), mode locked lasers, and superluminescent diodes, which are the building blocks of EPIC and ICT. Alternatively, these optical sources are potential candidates for other multi-disciplinary field applications.

Mid-infrared (mid-IR) supercontinuum (SC) sources have recently gained much interest, as a key technology for such applications as spectral molecular fingerprinting, laser surgery, and infrared counter measures. However, one of the challenges facing this technology is how to obtain high power and broadband light covering a spectral band of at least 2–5 µm, especially with a very efficient output power distribution towards the mid-IR region. This directly affects their usage in the practical applications mentioned above. Typically, an SC is generated by pumping a piece of nonlinear fibre with high-intensity femtosecond pulses provided by mode-locked lasers. Although this approach can lead to wide continuum generation, the output power is limited only to the milliWatt level. Therefore, to achieve high-power SC light, other laser systems need to be employed as pump sources. This paper briefly reviews SC sources, restricted to those with an average output power of over 0.4 W and simultaneously with a long-wavelength edge of the continuum spectrum of over 2.4 µm. Firstly, the concepts of SC generation, including the nonlinear phenomena governing this process and the most relevant mid-IR fibre materials, are presented. Following this study, a review of the main results on SC generation in silica and soft-glass fibres, also including my experimental results, is presented. Emphasis is given to high-power SC generation with the use of different pump schemes, providing an efficient power distribution towards longer wavelengths. Some discussion and prospective predictions are proposed at the end of the paper.

We report on recent progress in the generation of non-diffracting (Bessel) beams from semiconductor light sources including both edge-emitting and surface-emitting semiconductor lasers as well as light-emitting diodes (LEDs). Bessel beams at the power level of Watts with central lobe diameters of a few to tens of micrometers were achieved from compact and highly efficient lasers. The practicality of reducing the central lobe size of the Bessel beam generated with high-power broad-stripe semiconductor lasers and LEDs to a level unachievable by means of traditional focusing has been demonstrated. We also discuss an approach to exceed the limit of power density for the focusing of radiation with high beam propagation parameter M2. Finally, we consider the potential of the semiconductor lasers for applications in optical trapping/tweezing and the perspectives to replace their gas and solid-state laser counterparts for a range of implementations in optical manipulation towards lab-on-chip configurations.

Ripples are formed on the surface of solid materials after interaction with laser pulses of high intensity/irradiance. When ultra-short sub-1 ps laser pulses are used, the observed morphology of ripples on surfaces becomes much more complex as compared with ripples formed by long laser pulses. Uniquely for the short laser pulses, ripples can be formed in the bulk. A better understanding of the fundamentals of light-matter interaction in ripples formation is strongly required. Experimentally observed ripples and dependence of their parameters on laser fabrication conditions and material properties are summarized first. Then, a critical review of relevant ripple formation mechanisms is presented, discussed, and formation conjectures are presented. It is shown that formation of plasma at sub-critical or critical densities (i.e., solid state or breakdown plasmas) on the surface and in the bulk specific to the high-intensity ultra-short laser pulses has to be considered to account for the experimental observations. Surface and bulk ripples formed on/in dielectrics can be explained by the same model where electron–hole (solid state) plasma is formed at the very threshold of ripples formation. Ripple patterns have a strong application potential from sensing to light harvesting and (photo)catalysis mainly due to nanoscale features and self-replication of pattern over large macroscopic areas. Several emerging applications are shown.

Nematic liquid crystals possess large and versatile optical nonlinearities suitable for photonics applications spanning the femtoseconds to milliseconds time scales, and across a wide spectral window. We present a comprehensive review of the physical properties and mechanisms that underlie these multiple time scales nonlinearities, delving into individual molecular electronic responses as well as collective ordered-phase dynamical processes. Several exemplary theoretical formalisms and feasibility demonstrations of ultrafast all-optical transmission switching and tunable metamaterials and plasmonic photonic structures where the liquid crystal constituents play the critical role of enabling the processes are discussed. Emphasis is placed on all-optical processes, but we have also highlighted cases where electro-optical means could provide additional control, flexibility and enhancement possibility. We also point out how another phase of chiral nematic, namely, Blue-Phase liquid crystals could circumvent some of the limitations of nematic and present new possibilities.

In contrast to a conventional symmetric Lorentzian resonance, Fano resonance is predominantly used to describe asymmetric-shaped resonances, which arise from the constructive and destructive interference of discrete resonance states with broadband continuum states. This phenomenon and the underlying mechanisms, being common and ubiquitous in many realms of physical sciences, can be found in a wide variety of nanophotonic structures and quantum systems, such as quantum dots, photonic crystals, plasmonics, and metamaterials. The asymmetric and steep dispersion of the Fano resonance profile promises applications for a wide range of photonic devices, such as optical filters, switches, sensors, broadband reflectors, lasers, detectors, slow-light and non-linear devices, etc. With advances in nanotechnology, impressive progress has been made in the emerging field of nanophotonic structures. One of the most attractive nanophotonic structures for integrated photonics is the two-dimensional photonic crystal slab (2D PCS), which can be integrated into a wide range of photonic devices. The objective of this manuscript is to provide an in depth review of the progress made in the general area of Fano resonance photonics, focusing on the photonic devices based on 2D PCS structures. General discussions are provided on the origins and characteristics of Fano resonances in 2D PCSs. A nanomembrane transfer printing fabrication technique is also reviewed, which is critical for the heterogeneous integrated Fano resonance photonics. The majority of the remaining sections review progress made on various photonic devices and structures, such as high quality factor filters, membrane reflectors, membrane lasers, detectors and sensors, as well as structures and phenomena related to Fano resonance slow light effect, nonlinearity, and optical forces in coupled PCSs. It is expected that further advances in the field will lead to more significant advances towards 3D integrated photonics, flat optics, and flexible optoelectronics, with lasting impact in areas ranging from computing, communications, to sensing and imaging systems.

Optics originally developed for tunable organic dye lasers have found applications in other areas of optics, laser optics, and quantum optics. Here, the salient aspects of the physics related to the cavity linewidth equation and the effects of intracavity beam expansion and intracavity dispersion on this equation are reviewed. Additionally, the generalized multiple-prism dispersion equation is applied to direct-vision prisms, also known as Amici prisms, to calculate dispersion configurations of practical interest. Then, the higher derivatives of the multiple-prism dispersion equation applicable to laser pulse compression are considered. From this perspective, a new compact and generalized equation for higher-order phase derivatives is introduced for the first time. Furthermore, it is shown how the N-slit interferometric equation, derived from quantum principles using Dirac's notation, gives rise to generalized versions of the diffraction grating equation and the law of refraction. The nexus between the N-slit interferometric equation and the cavity linewidth equation is also illustrated. Finally, various optical and quantum optical applications that have benefited from these developments are highlighted.

Over the last decade, significant advances have been made toward the development of practical, tunable solid state dye lasers, which resulted in improved lasing efficiency with reduced dye photodegradation. To achieve this goal, a “chemical” approach was followed, where attention was focused onto the particular dye/host interaction and compatibility, specifically choosing already existing hosts for a given dye, synthesizing new dyes and/or matrices, or chemically modifying existing ones. Nevertheless, this approach was limited by a single fact learnt from the experience: there is no universal matrix which optimizes the efficiency and photostability of all dyes. This limitation could be overcome by following a “physical” approach, where the emission properties of the active medium are tailored by means of physical and structural modifications of the dye host. Following this approach, in this paper recent theoretical and experimental work is reviewed where it is demonstrated that following a simultaneous “physical” and “chemical” approach to tailor the emission properties of the host materials for solid state dye lasers, may lead, under specific circumstances, to the improvement of both the laser efficiency and photostability. In particular, it is demonstrated that optical scattering is not always detrimental either to conventional bulk lasers (laser rods or colloidal suspensions) or to integrated devices, but may give place, on the contrary, to dramatic improvements in the laser operation of organic (hybrid) laser rods, and to alternative ways of obtaining laser light from integrated devices based on the phenomenon of coherent random lasing, where feedback is provided by light scattering in an appropriate medium, without the need to manufacture complex periodic structures in the substrate. The processing and pumping flexibility of these materials, together with their low cost and capability of efficient emission across the whole visible spectrum makes them very attractive for the fabrication and development of coherent light sources suitable for integration in optoelectronic and disposable spectroscopic and sensing devices.

This review encompasses ultrafast laser interaction with matter in a broad range of intensities ~1010–1015 W/cm2. We consider the material transformation processes successively with increase of the absorbed laser intensity. We start with the subtle atomic displacements and excitation of phonons, and further analyze the phase transitions, ablation, transformation into plasma, and interaction of laser radiation with plasma up to the relativistic limit. The laser pulse is considered as of ultra-short duration if it is shorter the time scale of major energy relaxation processes such as the electron-to-lattice energy transfer, heat diffusion, and hydrodynamic motion. We describe the material response from the first principles, aiming to establish analytical scaling relations, which link the laser pulse characteristics with the properties of the material. Special section is dedicated to the possibility of creating super-high pressure and temperature with an ultrashort tabletop laser. The influence of the laser polarisation on the material ionisation is discussed. We consider theoretical and experimental aspects of a newly emerging topic of interaction of the ultrashort vortex beams and sculptured beams possessing complicated spatial and temporal distribution of intensity, polarisation, and the geometrical Berry-phase with matter. In conclusion, we discuss future directions related to the lasers and diagnostic tools on the attosecond time scale and with the photons energy in the x-ray range.

This paper describes and discusses visible fiber lasers that are excited by GaN laser diodes. One of the attractive points of visible light is that the human eye is sensitive to it between 400 and 700 nm, and therefore we can see applications in display technology. Of course, many other applications exist. First, we briefly review previously developed visible lasers in the gas, liquid, and solid-state phases and describe the history of primary solid-state visible laser research by focusing on rare-earth doped fluoride media, including glasses and crystals, to clarify the differences and the merits of primary solid-state visible lasers. We also demonstrate over 1 W operation of a Pr:WPFG fiber laser due to high-power GaN laser diodes and low-loss optical fibers (0.1 dB/m) made by waterproof fluoride glasses. This new optical fiber glass is based on an AlF3 system fluoride glass, and its waterproof property is much better than the well known fluoride glass of ZBLAN. The configuration of primary visible fiber lasers promises highly efficient, cost-effective, and simple laser systems and will realize visible lasers with photon beam quality and quantity, such as high-power CW or tunable laser systems, compact ultraviolet lasers, and low-cost ultra-short pulse laser systems. We believe that primary visible fiber lasers, especially those excited by GaN laser diodes, will be effective tools for creating the next generation of research and light sources.

The progression of carrier confinement from quantum wells to quantum dots has received considerable interests because of the potential to improve the semiconductor laser performance at the underlying physics level and to explore quantum optical phenomena in semiconductors. Associated with the transition from quantum wells to quantum dots is a switch from a solid-state-like quasi-continuous density of states to an atom-like system with discrete states. As discussed in this paper, the transition changes the role of the carrier interaction processes that directly influence optical properties. Our goals in this review are two-fold. One is to identify and describe the physics that allows new applications and determines intrinsic limitations for applications in light emitters. We will analyze the use of quantum dots in conventional laser devices and in microcavity emitters, where cavity quantum electrodynamics can alter spontaneous emission and generate nonclassical light for applications in quantum information technologies. A second goal is to promote a new connection between physics and technology. This paper demonstrates how a first-principles theory may be applied to guide important technological decisions by predicting the performances of various active materials under a broad set of experimental conditions.

For a number of years, the scientific community has been paying growing attention to the monitoring and enhancement of public health and the quality of life through the detection of all dangerous agents for the human body, including gases, proteins, virus, and bacterial agents. When these agents are detected through label-free biochemical sensors, the molecules are not modified structurally or functionally by adding fluorescent or radioactive dyes. This work focuses on label-free optical ring resonator-based configurations suited for bio-chemical sensing, highlighting their physical aspects and specific applications. Resonant wavelength shift and the modal splitting occurring when the analyte interacts with microresonant structures are the two major physical aspects analyzed in this paper. Competitive optical platforms proposed in the literature are also illustrated together with their properties and performance.

This paper reviews and compares the different optofluidic techniques for enhancing the retrieved Raman signal in liquids with a focus on aqueous solutions. Recent progress in characterizing different nanostructures and biological molecules utilizing optofluidic fibers such as photonic crystal fibers (PCFs) in Raman spectroscopy are discussed. Techniques and applications to combine surface enhanced Raman spectroscopy (SERS) with optofluidic-assisted Raman spectroscopy are further reviewed. Finally, challenges and future opportunities to advance Raman spectroscopy combined with optofluidics are presented.

This paper presents recent results in the development of novel ultrafast technologies based on the generation and application of extremely chirped optical pulses. Linearly frequency-swept mode-locked optical pulses of ns durations are generated, at the infrared telecommunications wavelength of 1.55 μm, by using chirped fiber Bragg gratings. The swept pulses appear as continuous wave signals, which completely fill the mode-locked pulse period which enables the implementation of semiconductor optical amplifying systems that completely circumvent the conventional limitation imposed by short pulse gain saturation. The use of these technologies is exemplified in a laser radar application that exploits the two characteristic coherent lengths in a chirped-pulse mode-locked laser, corresponding to the linewidth and the full lasing bandwidth, resulting in sub-mm resolution at the horizon. Finally, we show how stretched pulses can be used in a pulse shaping scheme to avoid detrimental nonlinearities associated with high power, optical pulse generation.