We demonstrate that periodic self-imaging of light patterns with certain input periods can be effectively realized in one-dimensional and two-dimensional helical waveguide arrays. The band structure is drastically dependent on the helix radius and period, and the complete collapse of quasi-energy bands occurs for a certain helix radius and period, which strongly affects the intensity carpet and the

We present new, to the best of our knowledge, large-scale, high-quality spectral filters operating in the long-wave infrared (LWIR) spectral region. We employ high-spatial resolution nanofabrication techniques to achieve large-area (${12}\;{{\rm mm}} \times 12\;{{\rm mm}}$) spectrally tunable notch filters. Filter operation is based on the guided-mode resonance effect. The device structure consists

Stimulated Brillouin scattering has great potential for wide-wavelength-range optical carrier recovery, as it can act as a parametrically defined narrowband gain filter. However, due to the dispersion of the Brillouin frequency shift, prior demonstrations have been limited in wavelength range. Here, we demonstrate that frequency modulating the pump light for a gain filter based on stimulated Brillouin

We report the first, to the best of our knowledge, observation of cross-phase modulational instability (XPMI) of circularly polarized helical Bloch modes carrying optical vortices in a twisted photonic crystal fiber with a three-fold symmetric core, formed by spinning the fiber preform during the draw. When the fiber is pumped by a superposition of left-circular polarization (LCP) and right-circular

We demonstrate a novel method to optically tune the pulse advancement and delay based on stimulated Raman gain in hydrogen. With a frequency-chirped pump, the generated signal pulse is selectively amplified at the leading or trailing edge of the pump pulse, depending on whether the frequency difference between the pump and the signal beam is blue or red detuned from the Raman transition, which results

Heavily ${{\rm Tm}^{3 +}}$-doped glass fibers are urgently desired for ${\sim}{2}\;\unicode{x00B5}{\rm m}$ single-frequency fiber lasers and high-repetition-rate mode-locked fiber lasers. Here the structure of glass networks was tuned through controlling the numbers of non-bridging oxygens and bridging oxygens by adjusting the composition of the glasses, hence increasing the ${{\rm Tm}^{3 +}}$ doping

The dependence of the Shannon entropy (SE) of a speckle pattern on the degree of polarization (DoP) of the pattern is investigated both experimentally and numerically. The superposition of two uncorrelated speckle patterns with polarization diversity is utilized to control the DoP of the superposed speckle pattern, and the SE of the pattern is estimated from the determined probability density function

Coherent diffractive imaging (CDI) is widely used to characterize structured samples from measurements of diffracting intensity patterns. We introduce a numerical framework to quantify the precision that can be achieved when estimating any given set of parameters characterizing the sample from measured data. The approach, based on the calculation of the Fisher information matrix, provides a clear benchmark

We show that in the interference of two partially correlated scalar light beams, the fields can be divided into parts that are mutually completely correlated (coherent) and parts that are fully uncorrelated with the correlated parts and with each other. Such correlated and uncorrelated parts cannot, in general, be unambiguously specified, but with a certain additional constraint, the partition becomes

Optical resolution photoacoustic microscopy (ORPAM) has demonstrated both high resolution and rich contrast imaging of optical chromophores in biologic tissues. To date, sensitivity remains a major challenge for ORPAM, which limits the capability of resolving biologic microvascular networks. In this study, we propose and evaluate a new ORPAM modality termed as optical resolution photoacoustic computed

An ultra-compact and broadband transverse magnetic (TM)-pass polarizer is experimentally demonstrated using a photonic crystal nanohole structure. By engineering the period of the circular holes, the fundamental transverse electric mode is suppressed due to the bandgap of the nanohole array, while the ${{\rm TM}_0}$ mode propagates with a negligible insertion loss. Simulation results predict that the

In this Letter, the broadband operation in wavelengths from 520 nm to 980 nm is demonstrated on silicon nitride nanophotonic phased arrays. The widest beam steering angle of 65° on a silicon nitride phased array is achieved. The optical radiation efficiency of the main grating lobe in a broad wavelength range is measured and analyzed theoretically. The optical spots radiated from the phased array chip

Micro/nano optoelectronic devices are widely studied as basic building blocks for on-chip integrated microsystem and multichannel logic units with excellent optoelectronic properties that are especially important part for interconnection route construction. Here, based on anisotropic waveguides, an optical switch with an on/off ratio of 2.14 is built up in a 2D CdS branched nanowire array. Because

One-dimensional polarization-independent grating couplers are demonstrated with the aid of the adaptive genetic algorithm optimization. By adjusting the relative weight between the coupling efficiency and the bandwidth of the polarization-dependent loss (PDL), we control the evolution direction and customize the final performance of the device. Two specific designs are generated by giving more weight

Multiple-quantum well (MQW) III-nitride diodes can both emit and detect light. In particular, a III-nitride diode can absorb shorter-wavelength photons generated from another III-nitride diode that shares an identical MQW structure because of the spectral overlap between the emission and detection spectra of the III-nitride diode, which establishes a wireless visible light communication system using

We demonstrate a C-band wavelength-tunable microlaser with an ${{\rm Er}^{3 +}}$-doped high quality (${\sim}{1.8} \times {{10}^6}$) lithium niobate microdisk resonator. With a 976 nm continuous-wave pump laser, lasing action can be observed at a pump power threshold lower than 400 µW at room temperature. Furthermore, the microdisk laser wavelength can be tuned by varying the pump laser power, showing

A cost-efficient and low-complexity optical input/output (I/O) packaging solution is a substantial challenge for volume production of photonic integrated circuits. To address this, metamaterial fiber couplers are an attractive solution for integrated photonic devices especially for optical I/O, interfacing standard optical fibers to photonic chips. They offer the advantages of refractive index engineering

An integrated optical chip that minimizes the size of the energy-tuning single-resonance-mode x-ray monochromator system into a $3\;{\rm{cm}} \times 5\;{\rm{cm}}$ silicon wafer is proposed. A Fabry–Perot x-ray resonator and two back-reflecting Si mirrors are employed on the wafer as the optical components, where Si(12 4 0) back reflection is used for both Fabry–Perot resonance and re-diffraction of

We report intracavity Bragg scattering induced by the photorefractive (PR) effect in high-$Q$ lithium niobate ring resonators at cryogenic temperatures. We show that when a cavity mode is strongly excited, the PR effect imprints a long-lived periodic space-charge field. This residual field in turn creates a refractive index modulation pattern that dramatically enhances the back scattering of an incoming

In this Letter, we present a new hybrid broadband-crossbar switching network that can switch multiple wavelengths on demand and can also multicast. This switch fabric is an improvement over our previous design in both switch footprint and power consumption, as it reduces the number of switching elements by approximately 50%. We compare the switch loss and crosstalk with that of a multiwavelength selective

We introduce a proof of concept for multimode random laser (RL) emission with fresh whole blood (WB) as the active medium. The experimental principle is adapted from RL emission using rhodamine 6G (R6G). We achieved conditions for fresh WB to fluoresce with stochastic amplification of stimulated emission of radiation. The random conditions are placed with ${{\rm SiO}_2}$ particles, suspended in isotonic

We report on micromilling cavities into fused silica by a 1030 nm femtosecond laser using 2.17 GHz bursts. The milled cavities show an increased depth per layer for a higher number of pulses per burst while the ablation efficiency is also increased. The maximum ablation efficiency for the optimum fluence achieved in our experiments is $3.05\;{{\rm mm}^3}/{\rm min}/{\rm W}$ for a burst number of 10

An increase in the radiation power of terahertz (THz) sources requires the development of new optics working with it. The laser-assisted replication technique is proposed to fabricate the diamond cylindrical diffractive lens with a continuous profile for the THz range. The procedure involves the inverted structuring of a silicon substrate by laser ablation for its further replication to the diamond

In this Letter, we demonstrate a method to combine a molecular iodine absolute frequency reference with a high-finesse optical cavity in a single laser to take advantage of the frequency stability properties of both systems at different time scales. The result is a laser exhibiting the long-term and short-term stability levels of the iodine frequency reference and optical cavity, respectively. The

We reported an all-polarization-maintaining single-frequency ytterbium-doped bidirectional fiber laser for the first time, to the best of our knowledge. Single-frequency operation was achieved by a stable dynamic grating in the active fiber of a proper length owing to the bidirectional operation of the laser. The fiber laser possesses a linewidth of 7.43 kHz, a slope efficiency of 47.9%, and a great

We demonstrate a 17 W single-frequency, low-intensity-noise green source at 532 nm, by single-pass second-harmonic generation of a 50 W continuous-wave fiber laser in a 30 mm MgO-doped periodically-poled stoichiometric lithium tantalate crystal. The maximum conversion efficiency is about 37%. A nearly Gaussian beam (${{\rm M}^2} \lt 1.15$ at 15 W) and low wavefront distortion are obtained. The system

The realization of bound states in the continuum (BICs) in optical systems has been relying mainly on symmetry breaking. In contrast, another mechanism, known as resonance-trapped (or Friedrich–Wintgen) scenario, has been reported in the limited scope of dielectric resonant inclusions or at off-$\Gamma$ points. In this Letter, we demonstrate that the coupling coefficient between two coplanar metallic

All-dielectric metamaterials conforming to an optical reflectionless potential (ORP) offer broadband, omni-directional suppression of reflection. Though they are predicted to possess broadband negative group velocity dispersion (GVD), ultrashort pulse propagation through such materials has not been studied so far, to the best of our knowledge. In this work, we demonstrate negative GVD and group delay

This work presents the design and fabrication of polymeric, structural optical filters that simultaneously focus light. These filters represent a novel, to the best of our knowledge, design at the boundary between diffractive optics and metasurfaces that may provide significant advantages for both digital and hyperspectral imaging. Filters for visible and near-infrared wavelengths were designed using

The effective fifth-order susceptibility, ${\chi}_{\rm eff}^{(5)}$, of two-dimensional (2D) semiconducting layered transition metal dichalcogenide (LTMD) molybdenum disulfide (${\rm MoS}_2$) is reported here for the first time, to the best of our knowledge. Using the $ Z $-scan technique with a laser operating at 800 nm, 1 kHz, 100 fs, we investigated the nonlinear behavior of ${\rm MoS}_2$ suspended

We report on high-quality high-throughput laser milling of silicon with a sub-ps laser delivering more than 1 kW of average laser power on the workpiece. In order to avoid heat accumulation effects, the processing strategy for high-quality laser milling was adapted to the available average power by using five-pulse bursts, a large beam diameter of 372 µm to limit the peak fluence per pulse to approximately

Motion contrast optical coherence tomography angiography (OCTA) entails a precise identification of dynamic flow signals from the static background, but an intermediate region with voxels exhibiting a mixed distribution of dynamic and static scatterers is almost inevitable in practice, which degrades the vascular contrast and connectivity. In this work, the static-dynamic intermediate region was pre-defined

Fast time-gated single-photon detectors demonstrated high depth sensitivity in the detection of localized absorption perturbations inside scattering media, but their use for in vivo clinical applications—such as functional imaging of brain activation—was impaired by their small (${\lt}{0.04}\;{\rm{mm}}^2$) active area. Here, we demonstrate, both on phantoms and in vivo, the performance of a fast-gated

We present a novel, to the best of our knowledge, form of polarization microscopy capable of producing quantitative optic-axis and phase retardation maps of transparent and anisotropic materials. The proposed method operates on differential phase-contrast (DPC) microscopy that produces a phase image of a thin specimen using multi-axis intensity measurements. For polarization-sensitive imaging, patterned

Orbital angular momentum (OAM) light, combined with the nonlinear process to expand the frequency range, has drawn increasing research interest in recent years. Here, we implement the first, to the best of our knowledge, experimental fourth-harmonic generation of OAM light with two cascaded quasi-phase-matching crystals. A Laguerre–Gaussian beam was transmitted through a duplet crystals system and

Manipulation of the nonlinear optical response of materials plays a significant role in photonics applications; however, it may be irreversible, untunable, and uncontrollable, which makes it difficult. In this Letter, we present a mechanical-hydrodynamical approach through a microchannel to tune the nonlinear absorption response of graphene oxide liquid crystals. In this material, the optical properties

Quantum frequency conversion (QFC) between the visible and telecom is a key to connect quantum memories in fiber-based quantum networks. Current methods for linking such widely separated frequencies, such as sum/difference frequency generation and four-wave mixing Bragg scattering, are prone to broadband noise generated by the pump laser(s). To address this issue, we propose to use third-order sum/difference

We investigated the performance of electric-field-induced second-harmonic generation (E-FISHG) by spectroscopic measurement using high-intensity femtosecond laser pulses. The second-harmonic intensity increased quadratically versus the applied electric field, as expected from the theory, up to 15 kV/cm with the laser energy up to 2.5 mJ, which is ${\sim}{5}$ times higher than the observable optical

Optical frequency conversion in semiconductor nanophotonic devices usually imposes stringent requirements on fabrication accuracy and etch surface roughness. Here, we adopt the concept of bound-state-in-continuum (BIC) for waveguide frequency converter design, which obviates the limitations in nonlinear material nano-fabrication and requires to pattern only a low-refractive-index strip on the nonlinear

The coherent propagation and amplification of high-power laser radiation in a multicore fiber consisting of a square array of weakly bound cores are studied. Exact stable analytical solutions are found for the out-of-phase mode, which describes the coherent propagation of wave beams in such fibers. The analytical results are confirmed by direct numerical simulation of the wave equation. The stability

We report phase and amplitude measurements of large coherent structures originating from the noise-induced modulation instability in optical fibers. By using a specifically designed time-lens system (SEAHORSE) in which aberrations are compensated, the complex field is recorded in single-shot over long durations of 200 ps with sub-picosecond resolution. Signatures of Akhmediev breather-like patterns

Cavity nonlinear optics enables intriguing physical phenomena to occur at micro- or nano-scales with modest input powers. While this enhances capabilities in applications such as comb generation, frequency conversion, and quantum optics, undesired nonlinear effects including photorefraction and thermal bistability are exacerbated. In this Letter, we propose and demonstrate a highly effective method

We report on efficient midinfrared difference-frequency generation (DFG) in orientation-patterned GaAs by intracavity mixing the signal and idler pulses of a narrowband nanosecond optical parametric oscillator based on periodically poled ${\rm{LiNb}}{{\rm{O}}_3}$. The maximum average DFG output power reached 215 mW at 8.15 µm for a repetition rate of 35 kHz. The temperature tuning range spanned over

We propose a ${2} \times {2}$ thermo-optic switch with high switching performance. The switch is based on multimode interferometer (MMI) couplers and a Mach–Zehnder interferometer (MZI) structure, where the phase arms are designed as laterally supported suspended ridge waveguides (LSSRWs) with a metallic heater placed on the slab. It is experimentally demonstrated that this switch has a power consumption

We report on a compact, ultrahigh-vacuum compatible optical assembly to create large-scale, two-dimensional optical lattices for use in experiments with ultracold atoms. The assembly consists of an octagon-shaped spacer made from ultra-low-expansion glass, to which we optically contact four fused silica cavity mirrors, making it highly mechanically and thermally stable. The mirror surfaces are nearly

We experimentally demonstrate, to the best of our knowledge, the first microdisk-based silicon-photonic mode-division (de)multiplexer circuit, which is compatible with wavelength-division multiplexing for high aggregate bandwidth on-chip optical communications. This circuit uses waveguide-wrapped microdisk resonators, featuring low levels of intermodal crosstalk and insertion loss within an ultracompact

The use of phase masks is necessary for wavefront coding, and these are often based on optical path differences. However, the optical dispersion constrains the resulting device to operate within a restricted spectral bandwidth. Here we propose to remove this constraint due to sub-wavelength structuration of the surface. The use of spatial and spectral co-localization properties of these structures

One of the defining characteristics of excitability is the existence of an excitable threshold: the minimum perturbation amplitude necessary to produce an excitable response. We analyze an optically injected dual state quantum dot laser, previously shown to display a dual state stochastic excitable dynamic. We show that deterministic triggering of this dynamic can be achieved via optical phase perturbations

This Letter reports a demonstration of integrating a tiny GaN-based photonic chip with a PDMS microfluidics system. The photonic chip containing InGaN/GaN quantum wells is responsible for light emission and photodetection and fabricated through standard microfabrication techniques. The PDMS-enclosed chip is formed adjacent to the fluidic channel and operates in reflection mode, enabling the optical

Time-domain analysis (TDA) is useful for measuring optical devices along with a link and for diagnosing a long device. In this Letter, an optical vector analyzer with TDA capability is proposed and experimentally demonstrated. The key to realizing TDA is a low-coherence optical carrier, which is achieved by modulating an electrical broadband signal on a continuous-wave light via acousto-optic modulation

Spectroscopic chemical detection requires knowledge or determination of an optical path for accurate quantification of path-integrated concentration of species. Continuous-wave-laser-based spectroscopic systems operating in an open integrated-path remote sensing configuration are usually not equipped for optical path determination. Here we demonstrate a measurement technique capable of simultaneous

We report on a short-cavity polarization beat-frequency distributed Bragg reflector (DBR) fiber laser that can operate in an unprecedentedly wide range of temperatures from ${-}{{200}}^\circ {\rm{C}}$ to 500°C. The beat-frequency signal inherited by the intrinsic fiber birefringence enables implementation of the laser as an eligible temperature or hydrostatic pressure sensor. Furthermore, type-IIa

A frequency-modulated continuous-wave laser ranging method using low-duty-cycle linear-frequency-modulated (LFM) signals is proposed. A spectrum consisting of a dense Kronecker comb is obtained so that the frequency of the beat signal can be measured with finer resolution. Since the dense comb is provided, super-resolved laser ranging can be achieved using a single-parametric frequency estimation method

A blended FC-V-50 and TZ-001 polymer-based microdisk laser was fabricated by the ink-jet printing method and used for biosensing applications. The FC-V-50 polymer has a negative charge due to the presence of carboxyl functional groups, and the TZ-001 polymer has a positive charge due to the tertiary amine group at a pH of seven. In biosensing applications, non-specific adsorption due to opposite charges

We carry out a very early theoretical study on surface waveguide modes excited in a long-period fiber grating (LPFG) coated with gold–silicon thin films for refractive index sensing. The surface waveguide modes originate from the intermode transition of EH cladding modes and present a very strong evanescent field penetrating into the surrounding medium, which makes them ultrasensitive to external changes

A passive correlated fiber loop ringdown (FLRD) system based on an amplified spontaneous emission (ASE) source is proposed and experimentally demonstrated for macro-bending measurement. Due to the randomness of spontaneous emission, the autocorrelation coefficient of ASE has an extremely narrow FWHM (0.114 ns), which allows shorter fiber loop and higher sensitivity. The experimental results show that

A full polymeric optofluidic Fabry–Perot (FP) resonator with a high quality factor (Q) is proposed and tested. The device is based on multilayer optical polymeric films that act as high reflectivity interference mirrors. The all-polymeric laminated structure avoids any deposition or etching process, simplifying the fabrication procedure while retaining a high quality optical surface. The measured quality

The frequency stability of lasers is limited by thermal noise in state-of-the-art frequency references. Further improvement requires operation at cryogenic temperature. In this context, we investigate a fiber-based ring resonator. Our system exhibits a first-order temperature-insensitive point around $3.55\,\,{\rm K}$, much lower than that of crystalline silicon. The observed low sensitivity with respect

In this Letter, we present Fourier-transform-limited, nanosecond scale optical pulses from a vertical cavity surface emitting laser (VCSEL) using injection locking with a narrow-band seed laser. We examine two different injection-locking architectures and show that we can achieve an effective injection-locking range of over 8 GHz with an extinction ratio of 20,000:1. These results indicate that injection-locked

In this Letter, we report optical confinement in the near-ultraviolet (near-UV) range in ${{\rm Ga}_2}{{\rm O}_3}$ nanowires (NWs) by distributed Bragg reflector (DBR) nanopatterned cavities. High-contrast DBRs, which act as the end mirrors of the cavities of the desired length, are designed and fabricated by focused ion beam etching. The resonant modes of the cavities are analyzed by micro-photoluminescence