We report on a method for controlling the polarity of gallium nitride (GaN) using an E-beam evaporated aluminum (Al) layer on a sapphire substrate. A high-temperature nitridation process was designed to enable the amorphous Al layer to serve as a nucleation layer for single-crystal Ga-polar GaN growth. The Al layer also acts as a mask that prevents N-polar GaN growth. As a result, Ga-polar and N-polar

This Joint Issue of Optics Express and Optical Materials Express features 15 articles written by authors who participated in the international online conference Advanced Solid State Lasers held 13–16 October, 2020. This review provides a summary of the conference and these articles from the conference which sample the spectrum of solid state laser theory and experiment, from materials research to sources

We report on the output performances of a fiber-coupled diode pumped Nd:LGSB laser passively Q-switched by a Cr4+:YAG saturable absorber (SA), with emissions at 1.06-μm near-infrared wavelength, as well as at 0.53-μm visible green spectrum through the self-frequency doubling process. The 2.3-at.% Nd:LGSB crystal delivered 1.43 W continuous-wave power at 1.06 μm with an overall optical-to-optical efficiency

We report on the spectroscopic characterization, absorption saturation, and excited-state dynamics of GR1 centers in synthetic diamonds. The non-linear optical measurements reveal an efficient bleaching of the GR1 center’s ground level under ns-pulsed 633 nm excitation. The maxima of absorption and emission cross sections were estimated to be 4.5 × 10−17 cm2 and 9 × 10−17 cm2 at 630 nm and 780 nm,

We present a microwave experimental setup emulating tight-binding systems that is now widely used in the realm of topological photonics. A thorough description of the experimental building blocks is presented, showing the advantages and the limits of this platform. Various experimental realizations are then described, ranging from the selective enhancement of a defect state in a non-Hermitian Su-Schrieffer-Heeger

We review our attempt to tackle topological photonics based on an experimental platform operating in the microwave frequency range. The latter is based on a resonant metamaterial consisting in a dense collection of finite-length resonant metallic wires, known as the wire medium. Inside, the wave propagation is accurately described by a polariton, which exhibits subwavelength propagating modes as well

A large mode-area (LMA) chalcogenide multicore fiber (MCF) with 13 hexagonally arranged cores has been designed and fabricated for mid-infrared (MIR) high power laser delivery. The dependence of mode distributions, bending loss and dispersion characteristics on the fiber structure parameters has been investigated by the method of finite element analysis at a wavelength range from 3 to 5 μm. An ultra-large

In a previous study, we compared experiments on drawing of axisymmetric tubular optical fibres to a mathematical model of this process. The model and experiments generally agreed closely. However, for some preforms and operational conditions, the internal channel of the drawn fibre was larger than predicted by the model. We have further investigated this phenomenon of an oversized channel with to determine

Cr4+:Y2SiO5 crystal fiber was grown by the laser-heated pedestal growth method. Severe spinodal decomposition domains were observed at low growth speed. At a growth rate of 30 mm/min, the spinodal decomposition area ratio was reduced to 0.4%. Using borosilicate as the cladding, 0.85 mW of broadband emission with a 3-dB bandwidth of 246 nm centered at 1257 nm was generated. The near-infrared light source

We report a systematical investigation on the mid-infrared nonlinear performances of Ge-Sb-S glasses. Laser damage threshold (Ith) of Ge-Sb-S glasses was measured under femtosecond pulsed laser incidence ranging between 1.55-3.6 μm. It is found that the Ith has the maximum value at stoichiometric composition. Moreover, the relationship between the refractive index refractive (n0) and nonlinear refractive

The argon content of titanium dioxide doped tantalum pentoxide thin films was quantified in a spatially resolved way using high angle annular dark field (HAADF) images and DualEELS (a form of electron energy loss spectroscopy (EELS) that takes two spectra in quick succession from the highs and low-loss region). Films annealed at 300 °C, 400 °C, and 600 °C were investigated to see if there was a relationship

Deep-ultraviolet (DUV) light sources are critical owing to their high photon energies and small diffraction limits, and synthetic quartz glass (SQ) is suitable for the Faraday rotators of DUV light. The Verdet constant in SQ was evaluated within the wavelength range of 190–300 nm. In addition to a high Verdet constant over the DUV region, this material exhibits a high transmittance without transitional

A terahertz (THz) dielectric property characterization method based on a unified single oscillator model has been developed and applied to a variety of multi-component silicate oxide glasses. The experimental values of dielectric constant determined by THz time-domain spectroscopy (TDS) in the sub-THz region have been confirmed to agree well with the values calculated by the single oscillator model

We investigate the nanoscale damage precursors that will cause laser damage initiation on fused silica surface during KOH-based wet etching. Some nanoscale damage precursors, like impurity contamination and chemical structure defects on different etched surface with a KOH solution, are explored through a variety of testing methods at nanoscale spatial resolution. The etched surface roughness and photothermal

A multi-position disordered Er3+:Gd2SrAl2O7 single crystal was grown by the Czochralski method. Room temperature polarized spectral properties of the crystal were investigated in detail. The Judd–Ofelt theory was applied to analyze the polarized absorption spectra. The peak stimulated emission cross-sections of the 4I13/2→4I15/2 transition reach 0.79 ×10−20 and 1.25×10−20 cm2 for σ and π polarizations

In the recent two decades, Cr2+:ZnSe crystals have been widely used as a gain media for 2∼3 μm mid-infrared lasers. However, it still remains a huge challenge for researchers to meet more and more requirements on the crystals with high qualities and large sizes. In this work, one Cr2+:ZnSe single crystal with a diameter of about 15 mm was successfully grown by chemical vapor transporting (CVT) with

Al2O3 coating is chemically unstable in hot water and transforms into a porous structure with a broadband anti-reflection (AR) property. We investigate the influences of treatment time on the AR property and structure morphology of the Al2O3 coating deposited by electron beam evaporation. Al2O3 coating treated for 7 minutes is found to possess the best AR property with an average reflectance of approximately

To produce a deep green (530 nm–570 nm) LED, the suitable indium (In) composition in the InxGa1-xN/GaN multi-quantum well (MQW) structure is crucial because a lower indium composition will shift the wavelength of emission towards the ultraviolet region. In this paper, we clarify the effects of an indium-rich layer to suppress such blue shifting, especially after the annealing process. According to

In this study, we use a time-resolved pump-probe shadowgraph technique to investigate the evolution characteristics of filamentary damage in bulk fused silica induced by a nanosecond pulse at 532 nm. The pump laser focuses on the front surface of sample and filamentary damage appears independently in the middle of sample. The whole damage process can be divided into single filament (SF), double filaments

Multiphoton lithography allows the high resolution, free-form 3D printing of structures such as micro-optical elements and 3D scaffolds for Tissue Engineering. A major obstacle in its application in these fields is material and structure autofluorescence. Existing photoresists promise near zero fluorescence at the expense of poor mechanical properties, and low printing efficiency. Sudan Black B is

Here, single-mode waveguides are written in silica glass by femtosecond (fs) laser. The waveguides exhibit a low propagation loss of 0.15 dB/cm and a symmetrical mode field. The loss performance and the mode field symmetry are demonstrated to strongly depend on the pulse repetition and polarization of fs laser, respectively. Raman and photoluminescence properties indicate that an increase of refractive

The development of optical systems operating in the far ultraviolet range (FUV, λ=100-200 nm) is limited by the efficiency of passivated aluminum (Al) mirrors. Although it is presently possible to obtain high-reflectivity FUV mirrors through physical vapor deposition, the process involves deposition with substrates at high temperatures, which is technically challenging for large optical elements. A

A nonvolatile silicon photonic switch constructed by a hybrid integration of a back-gate flash-memory unit with a silicon waveguide is proposed. It can persistently maintain the switching state without continuous supplies due to the memory function of the flash unit, which makes it attractive to reduce the static power consumption. The single-gate control configuration is replaced by dual electrodes

Heterogeneous integration of materials with a negative thermo-optic coefficient is a simple and efficient way to compensate the strong detrimental thermal dependence of silicon-on-insulator devices. Yet, the list of materials that are both amenable for photonics fabrication and exhibit a negative TOC is very short and often requires sacrificing loss performance. In this work, we demonstrate that As20S80

The Airy beam possesses some unusual properties, which are non-diffraction, self-healing, and a unique self-bending behavior. Previous works about metasurfaces have used geometric phase or plasma resonance to produce the Airy beam. However, the former requires a circular polarized light incident, while the latter has a large optical loss. In this paper, a polarization insensitive metasuface is designed

We demonstrate volume holographic recording at a wavelength of 640 nm in a photopolymerizable nanoparticle-polymer composite (NPC) film dispersed with ultrahigh refractive index hyperbranched-polymer (HBP) organic nanoparticles. We employ a new photosensitizer-initiator system consisting of cyanine dye, triazine compound and borate salt for efficient radical generation in the red. We investigate the

We report for the first time nonlinear frequency conversion—specifically optical parametric oscillation—in OP-GaP layers grown by hydride vapor-phase epitaxy on 3-inch OP-GaAs templates. Continuous tuning with wavelength coverage from 3.9–12 µm was achieved by using stepped and fan-out gratings having periods from 18.0–35.2 µm, which propagated 150 µm of a 1.2-mm-thick layer before overgrowth. Anti-reflection-coated

Partially deuterated potassium dihydrogen phosphate (DKDP) allows for the optical parametric chirped-pulse amplification of high-energy broadband optical pulses to generate ultrashort, high-peak-power pulses. Modeling and experimental optimization of the noncollinear interaction geometry require the combination of a model for the deuteration-dependent optical indices and knowledge of the deuteration

Materials with biomolecule-compatible functional groups are desirable for the fabrication of microdisk lasers used in bio-sensing applications. In this study, a microdisk laser was fabricated using a low-viscosity hyper branched polymer FC-V-50 using ink-jet printing, and was surface-modified at room temperature within a relatively short time compared to conventional methods. The carboxyl functional

In this work, photoluminescence (PL), quantum efficiency and carrier dynamics are investigated in indium arsenide (InAs) nanowires (NWs) with various surface treatments, including a molecular beam epitaxy (MBE)-grown semiconductor shell passivation, sulfur-passivation, alumina (Al2O3) coating by atomic layer deposition (ALD) and polydimethylsiloxane (PDMS) spin-coating. The ALD-dielectric layer-coated

In this work, the scattering mechanism by nano-patterned sapphire substrate (NPSS) for flip-chip AlGaN-based deep ultraviolet light-emitting diodes (DUV LEDs) has been investigated systematically via three-dimensional finite-difference time-domain (3D FDTD) method. It is found that for the conventional DUV LED with a thick p-GaN layer, the NPSS structure can enhance the light extraction efficiency

SrTiO3 is the model perovskite compound and has demonstrated technological relevance from being the foundation of oxide electronics to a promising candidate as a high-temperature hydrogen sensor. Here, we fully investigate the temperature-dependent UV-Vis optical constants of pristine and doped SrTiO3 in the spectral range 0.73-5.90 eV using spectroscopic ellipsometry and first-principles. The oscillator

A GaAs quantum-well laser diode was directly grown on silicon (001) substrate by a hybrid technique comprising AlAs nucleation and thermal cycle annealing. The hybrid technique provided the advantages of superior surface roughness, high quantum efficiency, and low threading dislocation density (TDD) of a thin buffer. The TDD was quantitatively characterized through the electron channeling contrast

We measured the isopiestic specific heat (CP) of Y3Al5O12 (YAG) by the differential scanning calorimetry aiming to obtain thermal parameters under cryogenic and room-temperature (RT) conditions. It was also found that the applicable temperature range of our numerical model for CP of YAG was updated to the range between 129 K and 573 K with below 3% error. Obtained parameters were verified by the comparative

We present spectroscopic properties of the low-maximum-phonon energy host material, barium fluoride (BaF2) doped with Er3+ ions. Following optical excitation at 800 nm, Er3+:BaF2 exhibited broad mid-IR emission bands centered at ∼2.75, ∼3.5, and ∼4.5 µm, corresponding to the 4I11/2 → 4I13/2, 4F9/2 → 4I9/2 and 4I9/2 → 4I11/2 transitions, respectively. Temperature-dependent fluorescence spectra and decay

High pressure chemical vapor deposition (HPCVD) has shown to be a promising method for producing Cr2+:ZnSe and Fe2+:ZnSe mid-IR optical fiber lasers. The oxidation state of the dopants and their spatial homogeneity are critical for the characterization of effective fiber laser performance; however, this is challenging for small fiber cores and small doping concentrations. We demonstrate using synchrotron

Hollow-core fiber (HCF) is a promising candidate for optofluidic applications because it can act as a gas-cell, permitting intense fluid-light interaction over extended lengths with low optical loss and inherent flexibility. Such a platform could pave the way for an all-fiberized, compact, robust and practical system for sensing applications. To facilitate this, we report a high-precision and repeatable

In this work, we report the fabrication of an all-polymer multimaterial optical fiber based on two different grades of cyclo-olefin polymers (known as Zeonex) and the high-performance thermoplastic polysulfone (PSU) with glass transition temperature (Tg) of 189°C. The core/cladding structure using the Zeonex polymers (E48R/480R, respectively) was developed using a co-extrusion method followed by a

Polycrystalline infrared (PIR) fibers are used for numerous applications, one of those being power delivery for CO2 −lasers. However, the fiber tip surface’s transmittance cannot be increased with conventional antireflection coatings due to the surface unevenness. Antireflection microstructures (ARMs) offer an alternative way of increasing transmittance. In this work, ARMs were fabricated on the fiber

Hybrid-material optical fibers enhance the capabilities of fiber-optics technologies, extending current functionalities to several emerging application areas. Such platforms rely on the integration of novel materials into the fiber core or cladding, thereby supporting hybrid modes with new characteristics. Here we present experiments that reveal hybrid mode interactions within a doped-core silica fiber

We design cylindrical multilayer structures characterized by anisotropy and topological features. This provides a new approach to tailor electromagnetic fields into desired patterns with orbital angular momentum in cylindrical geometries as ring resonators and fibers. We use transformation optics to deal with anisotropic circular structures, and rigorously define the edge states. The resulting topologically

Topological photonics provides a novel route for designing and realizing optical devices with unprecedented functionalities. Topological edge states, which are supported at the boundary of two photonic systems with different band topologies, enable robust light transport immune to structural imperfections and/or sharp bends in waveguides. Furthermore, the topological edge states are expected to revolutionize

Topological protection is a promising way to deal with the decoherence issue in quantum systems. To induce topological excitations in Josephson junction arrays (JJA), we propose a scheme where only Josephson critical currents are tuned in JJA on honeycomb lattice, which is easily achieved by changing potential barriers or lengths of insulators between superconducting islands. In the present system

We theoretically investigate quantum phase transitions from topologically non-trivial to trivial states in three-dimensional hybridized topological insulator (TI) ultra-thin films. The interplay between the hybridization of the top and bottom surface states (SSs) and Zeeman energy gives rise to topological and normal insulating phases. By tuning the Zeeman energy, we can drive phase transition between

In this paper, a four open channel dual-core photonic crystal fiber (OC-DC-PCF) refractive index (RI) sensor is numerically investigated by finite element method (FEM) based software for the detection of unknown biomolecules. To create the surface plasmon resonance (SPR) effect, novel plasmonic material gold (Au) is externally deposited to the selected slotted region which makes this design cost-effective

To address the challenge of appropriate cementitious materials that can support future optical fibre sensors with reduced strains for smart city infrastructure, reducing structural heterogeneity by integrating diatomous earth is proposed. A series of samples made up of commercial grade instant mortar and an increased percentage of diatomous earth are fabricated and characterised. Mindful of the growing

In this paper, we explored a rapid and ultra-sensitive detection method of fucoxanthin in algae by surface-enhanced Raman scattering. Gold nanoparticles (Au NPs) were prepared by the reduction of chloroauric acid with citric acid. An effective Raman indicator molecule, Rhodamine 6G(R6G) dye molecule, was used to characterize Au NPs that were used in SERS analysis to detect fucoxanthin. It was found

Core-shell Bi2SiO5 nanosystem with uniform morphology and narrow size distribution has been successfully synthesized via a facile template-assisted route. With the introduction of Eu3+, detailed studies are performed to evaluate its promise as Eu3+-based phosphor host. The yielded Bi2SiO5:Eu3+ nanospheres are proven to be pure tetragonal phase via X-ray diffraction and Rietveld refinement. Moreover

The light yield, spatial resolution, and image quality of inorganic scintillators (CsI:Tl (CsI), Gd3Al2Ga3O12: Ce (GAGG), Lu3Al5O12: Ce (LuAG), CdWO4 (CWO), Y3Al5O12: Ce (YAG), Bi4Ge3O12 (BGO), and Gd2O2S: Tb (GOS)) were investigated using monochromated synchrotron radiation. For quantitative analysis, the same imaging system composed of a relay lens system and a camera was used for all scintillators

All-glass, micro-groove arrays were etched into a glass light guide plate surface, transforming edge-lit incident light into uniform area output from its surface. All micro-grooves in the array shared similar shape and extraction efficiency. They were spray etched into Corning alkali-borosilicate glass (Iris) effectively controlling the degree of light extraction uniformity along the array’s normal

We reveal a new luminescent center with a narrow emission line at 0.681 eV in iron-doped ZnSe at low temperatures. In addition to the main emission line, a satellite peak with a maximum at 0.683 eV and a vibronic band characteristic of intracenter transitions were clearly observed. The spatial distribution of the luminescence signal near 0.681 eV is correlated with the well-known (5T2 → 5E) iron-related

We present spectroscopic measurements focusing on a detailed investigation of temperature dependence of absorption, emission and gain in the uniaxial Yb:YLF laser gain medium. Measurements are carried out in the 78–300 K range, but we especially targeted our attention to the 78–150 K interval, which is the desired working range of liquid nitrogen cooled cryogenic Yb:YLF lasers/amplifiers. A tunable

As a binary oxide, β-Ga2O3 is a promising host material with high thermal conductivity compared with the traditional laser materials. In this work, Co2+-doped β-Ga2O3 single crystal was successfully grown by the edge-defined film-fed growth (EFG) method and firstly designed as a near-infrared (NIR) optical modulator by doping with cobalt. The doping concentration of Co2+ ions was determined to be 0

The interaction between a metal surface and multiple pulses was investigated to achieve optimal focusing conditions during ultrashort laser ablation. We report a simple theoretical expression of morphological changes in the ablated channel and demonstrate its advantage in positioning the interactive surface at the focus in real time during multiple-pulse laser ablation of a metallic material. Experimental

We investigated material properties of terbium aluminum garnet (TAG) ceramics and its characteristics as a material for a Faraday isolator for high-average power lasers. We measured the transmittance, absorption coefficient, and temperature dependencies of Verdet constant and thermal conductivity. Consequently, our model analysis shows that TAG ceramic isolators can be operated over 3 kW average laser

Terahertz waves have attracted considerable attention in recent years because of their potential applications in different fields. The appearance of a digital metasurface simplifies the design of functional devices and manipulates the terahertz wave in a convenient way with a specific array of digital particles. Metal resonators are mostly used in traditional structures, and the ohmic loss of metal

Solid solution AgInS2-ZnS nanostructures were prepared by reacting (Z)-1- (octadec-9-enyl)-3-phenylthiourea and 1-dodecanethiol with the corresponding metal linoleates. The combination of sulfur sources in modified ratios, which individually do not lead to significant results, resulted in the successful formation of nanorod-shaped heterostructures. The effect of sulfur source ratios on the structure

Optical properties of mid-infrared, Li-based nonlinear crystals (NLC) are estimated under realistic experimental conditions for high power lasers using the thermal imaging method. The study focuses on crystals with relatively large apertures for high energy and power applications that are transparent in a broad spectral range (6–16 µm). For this purpose, a high average power Yb:YAG laser amplifier

Here, few-layered W2C nanosheets and microfiber-based few-layered W2C-SA are fabricated by the magnetron sputtering deposition method. The third-order nonlinear optical responses of the prepared 2D W2C nanosheets are investigated by the Z-scan method with βeff and n2 determined to be −88.2 cm/MW and −1.112×10−13 m2/W, respectively, revealing its excellent nonlinear saturable absorption properties and

This research examines the thermally-induced nonlinear optical properties of Ti-Al-oxide nano-films. The Ti-Al nano-layer system was sequentially evaporated on glass and c-Si(100) substrates at room temperature. The Ti layers were spontaneously oxidized by the residual oxygen of the background vacuum in the deposition chamber. The Al layer, on the other hand, was partially oxidized and contained metallic