Ultra-compact multichannel optical waveguide crossings are designed by a particle swarm optimized inverse-design method. The 2 × 2 TE (TM) device has an ultra-small footprint of 2 ×2μm2 and exhibits a high transmission efficiency of 69.1% (89.7%) and low crosstalk of −34.4 dB (−84.8 dB) at 1550 nm. The devices can work within a large range of pixel size and waveguide width, suggesting high process

The authors theoretically demonstrated a tunable- and switchable-metamaterial absorber at the terahertz (THz) frequency. The proposed absorber comprising Bulk Dirac semimetal (BDS) metamaterials and vanadium dioxide (VO2) continuous film, which can be switched between a traditional and coherent absorber by tailoring the conductivity of VO2 film. When VO2 is in its metallic state, the proposed absorber

A novel method enabling the production of an ultrabroad dual-triangular filter (DTF) is proposed and numerically demonstrated, which is realized by using an optimized phase-modulated helical long-period fibre grating (PM-HLPG) operated especially at wavelengths near the dispersion-turning-point (DTP) of cladding-mode LP1,10. As a typical design example, four linearly spectral regions, each with dynamic

Metal-based nanoparticles are limited in their applications due to their inherent loss. Here, we propose all dielectric nanoparticles to enhance forward scattering efficiency. Firstly, all dielectric nanoparticles composed of lossless nanodisks are created. By changing the geometric size of the nanoparticles, 2π phase coverage can be achieved. We further coded these all-dielectric nanoparticles to

Deep learning has shown the high potential for the use of resolution enhancement in microscopic imaging. However, a large amount of paired datasets are usually required for training the networks. Data preparation is costly from the microscopic experiment. In this paper, the cycle generative adversarial network, trained by only a small amount of unpaired experimental microscopic images, is used to generate

Laser speckle rheology is a powerful method to measure viscoelasticity of biological fluids. To date, the in vivo assessment of viscoelastic properties of biofluids has been limited by several reasons such as combined speckle fluctuation and insufficient detection depth. In order to avoid these shortcomings, in particular, the problems associated with detection depth during in vivo viscoelastic testing

This paper proposes a numerical simulation of an optical frequency comb scheme at 1550 nm based on a dual-frequency laser pump in the AlGaAs-on-insulator waveguide. Optical frequency comb with a 5 dB spectral bandwidth of approximately 125 nm is obtained within a 0.08-m normal-dispersion AlGaAs waveguide based on pulse compression, self-phase modulation, and optical wave breaking. The influences of

The structure optimization for a binary reconfigurable true time delay lines (RTTDL) based on the Mach–Zehnder interferometer (MZI) switches is proposed. Firstly, the number of the variable optical attenuator (VOA), which is generally used to make up for the imperfectness of the MZI switch and improves the RTTDL ’s flatness of broadband amplitude response and the delay accuracy, is minimized. Meanwhile

A transmitted optical fiber sensing system based on orthogonal demodulation algorithm is used for hydrogen detection in this paper. WO3/Pt fabricated by sol–gel method was used as sensing material. WO3 film reacts with hydrogen by the catalysis of Pt and refractive index of the sensing film changed, by measuring the transmitted optical power the concentration of hydrogen can be detected. Orthogonal

A novel diffusion double-ended bonded structure (DEBS) consisting of F2 glass, Er3+/Yb3+: glass and Co2+:MgAl2O4 was reported, for human eye-safety micro-ranging lasers. Compared with single-ended bonding structure (SEBS) and single glass structure (SGS) by the thermal analysis, its thermal focal length increased by 53.8% over the latter two. It was noted that the DEBS could effectively reduce the

A highly tunable design for obtaining double resonance enhanced surface-enhanced Raman spectroscopy (SERS) substrates with ultrasmall vertical nanogaps is proposed by utilizing the plasmonic Fano resonances resulted from the strong coupling between the broad gap plasmon mode of the Au nanocavity and the narrow surface plasmons polaritons. A sandwiched plasmonic nanocavity of Au nanostrip grating upon

We demonstrate the temperature distribution and 2.79 μm laser performance in a high-quality Er:YSGG single crystal fiber (SCF) with size of Φ 0.85×8 mm3 for the first time. Compared with 2×2×8 mm3 Er:YSGG bulk crystal, the simulation results show that the center maximum temperature of Er:YSGG SCF is much lower, and the temperature rising and total thermal deformation are evidently reduced, indicating

We have developed a sensing platform using a long-period fiber grating (LPFG) integrated black phosphorus (BP) thin film from the numerical simulation analysis and experimental process verification. Due to the high optical absorption of BP, the attenuated depth of the cladding mode in the BP coated LPFG (named BP-LPFG) sensor can be varied by the change of external environment. Benefited from the BP

A novel method to realize single-transverse-mode emission by incorporating a built-in index guide is employed on vertical-cavity surface-emitting lasers (VCSELs) with a large oxide aperture. The etched index guide provides modal loss discrimination for mode selection and transverse optical field confinement for light propagating in the longitudinal direction. A single-transverse-mode VCSEL with side-mode

A novel optical fiber integrated optoelectrode was proposed and miniatured photoelectrochemical (PEC) sensor was realized. In the structure, transparent conductive oxide indium-tin-oxide (ITO) film and photocatalytic material are coated outside of one end of the optical fiber. This tiny optoelectrode first simultaneously realizes the light-guiding ability and the microelectrode function of electroanalysis

Metasurfaces exhibit promising capacities in the manipulation of electromagnetic (EM) waves, as to diverse dimensions like amplitude, phase, and polarization. Despite many methods have been used to improve regulatory capabilities of EM waves, the efficiency and working bandwidth has yet to be developed. In this paper, an ultra-wideband and high-efficiency reflective polarization converter metasurface

Conventionally, the behavior of light transmission in optical devices is based on total internal reflection or photonic bandgaps. The Dirac mode is regarded as another guiding mechanism that relies on the zero-density of radiation states around the Dirac point to avoid power leakage and thus achieves field confinement. Unlike conventional light guiding mechanisms, the Dirac mode features a unique algebraic

2.79 μm-band pulsed laser has important application prospects in medicine, military, etc. In this paper, the pulse operation of Er, Cr: YSGG laser Q-switched by piezoelectric crystal La3Ga5SIO14(LGS) is realized, and high-energy output under nanosecond pulse is obtained. In the experiment, LGS crystal was used as the de-voltage Q-switching element. At a repetition frequency of 10 Hz, the obtained pulse

In this paper, a new saturable absorber (SA) based on Lanthanum Hexaboride (LaB6) is used to produce Q-switched and mode-locked laser pulses. In constructing the SA, the prepared LaB6 powder is dispersed in polyvinyl alcohol (PVA) solution before the mixture is dried to form a thin film. A small piece of the film is placed between two fiber ferrules to form a LaB6 PVA SA and added to a laser cavity

A tilted fiber Bragg grating (TFBG) hydrogen sensor based on Pd/Au composite nanofilms was proposed. Pd and Au films with thickness of 25 nm and 35 nm were deposited on the surface of TFBG by magnetron sputtering method. Pd is a face centered cubic structure, which is capable of adsorbing hydrogen atoms. Accordingly, the effective refractive index of Pd/Au composite film changes with the variations

We propose a method for designing the multilayer diffractive optical elements (MLDOEs) to improve the polychromatic integral diffraction efficiency (PIDE) in wide angle of incidence. By comparing and analyzing the characteristic angle weighted PIDE (CAW-PIDE) in the whole angles of incidence, the optimal microstructure height combination of the MLDOE can be obtained. The optimization process and simulation

In this paper, we report a high-power single-frequency all-fiber amplifier at 1064 nm based on cascaded hybrid active fibers. The cascaded gain fiber design, where a piece of active fiber with lower dopant concentration is spliced before the highly doped gain fiber, is proposed to effectively alleviate the thermal loads of high-power amplifier. By virtue of hybrid pump at 976 nm and 915 nm to increase

Based on Rotational Doppler Effect of light beam carrying orbital angular momentum, the lateral rotational velocity of the target is able to be measured. However, most of current researches about rotational velocity measurement only focus on the case of constant rotational velocity. Here, a novel method of non-constant rotational velocity measurement is proposed. This method uses the signal processing

A volume Bragg grating-based external cavity diode laser array produced more than 100 W output power for metastable argon atoms pumping centered at 811.53 nm with a 0.15 nm spectral linewidth (FWHM). The device has only 4.6 % loss compared to the free-running case operating at full power and a spectral contrast of 40 dB. The emission spectrum can be precisely tuned to 811.53 nm and has an over 200

This paper proposes a theoretical scheme to synthesize white laser source based on the cascaded sum frequency generation (CSFG) model with stimulated Raman adiabatic passage (STIRAP). In the CSFG model, the signal laser, intermediate laser and output laser correspond to red, green and blue (RGB) lasers respectively. The results show that in general the red laser is completely converted to the blue

In this paper, a dynamically switchable dual-band absorber based on electromagnetically induced reflection (EIR) in metal-graphene hybrid metamaterial is proposed. The unit cell of metamaterial absorber has three layers. The top layer consists of two split-ring resonators (SRRs) and two orthogonal cut-wires (CWs) with different lengths. Due to the low reflection dips in EIR structure and good absorption

In this paper, a refractive index biosensor is proposed which employs Si photonic nanorings coupled to ring-shaped plasmonic nanohole arrays (PNA) on a hybrid substrate to facilitate sensing of different glucose concentrations in water solution. The proposed structure can be used as a single-mode refractive index biosensor with a high sensitivity of 1278 nm/RIU, a figure of merit (FoM) of 168.1 RIU−1

As a new proposed spectrometer, the filter-based spectrometer uses a group of filters with known transmittance to modulate the spectrum of an incident light beam. After employing a post-processing algorithm, the spectrum of the beam can be reconstructed. For such spectrometers, the transmittance curve characteristics of the filters have a crucial impact on the spectrum reconstruction results. To better

Studies on the changes in biomechanical properties of the gingiva are significant, since they are closely related to the pathological process of gingivitis and periodontitis. Although some research has been conducted, the currently used techniques are not feasible for in vivo and clinical measurements due to their disadvantages, such as the invasive nature and the requirement of thin sectioning. In

The non-negative least squares algorithm is widely used in dynamic light scattering, however, it suffers the shortcomings of sparse solutions and poor anti-noise performance. It is found that the construction of the kernel matrix of the algorithm is of great significance to the accuracy of the final results. In this paper, we propose an adaptive strategy to find the optimal step-size to construct the

An all-optical off-beam quartz-enhanced photoacoustic spectroscopy (QEPAS) sensor employing double-pass acoustic microresonators was proposed and experimentally investigated. An optical fiber Fabry–Perot interferometric sensor with quadrature point self-stabilization was employed for the detection of quartz prong vibration. A commercial quartz tuning fork with a resonant frequency of 30.72 kHz was

As the size of research objects reaches the nanometer level, there is an increasing desire to trap and detect nanoparticles. However, the means to trap and study individual nanoparticles is not mature. Here, we propose and demonstrate a method for trapping a single nanoparticle stably and moving it in a three-dimensional space using a single-mode optical fiber probe based on a strong convergent LP11

A fiber optic temperature sensor utilizing a thin polarization maintaining fiber (PMF) based Sagnac loop is proposed and experimentally demonstrated. A Sagnac loop consisting of a thin PMF has a large fringe visibility of up to 46.16 dB. Except polarization eigen modes, cladding modes are excited owing to fiber mismatch to enhance the temperature sensitivity. The resonant dips of the wavelength spectrum

Quarter-wave plate (QWP) is one of the most important components of dynamic interferometer and its retardation can influence the measurement accuracy, which is usually manifested as periodic ripple error in the measurement results. Based on Jones matrix, the error formula is deduced in this paper, and the error correction method by rotating the half-wave plate (HWP) to change the intensity distribution

Active transverse electric and transverse magnetic pass polarizers with lengths of only 1.92 μm and 5.95 μm based on silicon waveguides and phase change material VO2 films are theoretically demonstrated. The optical characteristics of the polarizers are simulated by using finite difference mode simulation. By controlling the phase state of VO2 film, the polarizers can realize the regulation of TE and

Dengue fever is one of the most common diseases in tropical and sub-tropical regions of the world, and has a variety of unpleasant and painful symptoms, including fever, bleeding, and even death. Thus, effective methods for its early-stage detection and diagnosis are urgently required. Accordingly, the present study proposes a method for detecting dengue virus through an inspection of the anisotropic

Conventional metasurfaces cannot adjust the electromagnetic responses once the structures are determined. In this paper, we numerically demonstrate a thermally switchable bifunctional metasurface based on the phase change material vanadium dioxide (VO2) applied to the mid-infrared band. The dual-layer ring resonator consists of an Ag split ring and a VO2 ring, which can achieve ultra-broadband polarization

A novel photonic analog-to-digital conversion (ADC) scheme based on time-to-frequency mapping is proposed and experimentally demonstrated. In the approach, the amplitude of the input analog signal is firstly converted into a time-varying signal by pulse position modulation, then the time variation is mapped into the optical spectrum with the help of time-to-frequency mapping offered by the chirped

Speckle modulation in the laser beam projection scenarios such as adaptive optics, remote sensing, and active imaging has been a long-standing challenge that causes intensity fluctuation and further degrades the performance of the system. Speckle statistical characteristics coupled with the feature of the laser beam intensity distribution can be obtained by analyzing the speckle variation through a

The characteristics of the filaments generated by propagating a femtosecond Gaussian beam in a 2 m long gas cell with continuously varying pressures at different focal distances are numerically investigated. The simulated results indicate that the onset distance and the length of the filaments depend sensitively on the variation of pressure. These effects are enhanced with the increase of the focal

We demonstrate a tunable optical tapped delay line (OTDL) using delays based on orbital angular momentum (OAM) modes to perform data correlation and equalization for a quadrature phase-shift-keyed (QPSK) signal. The system: (i) creates N signal replicas as N taps on different OAM modes through mode multicasting, (ii) tunes the complex tap weights (i.e., amplitude and phase of the modes), (iii) applies

The design and experimental demonstration of a large, ultrahigh-quality (Q) factor, and single-mode operation silicon ring resonator based on a strip silicon photonic waveguide are presented. The ring resonator comprises multimode straight strip waveguides (MMWG), single-mode strip waveguides (SMWG), 90° Bezier bends, and linear tapers. The SMWG are used in the coupling region to achieve mode coupling

In the field of microscopic imaging, the double-helix point spread function (DH-PSF) based on the Fresnel zones is often used to locate the three-dimensional position of particles. The lower transfer function efficiency makes it difficult to track the trajectory of moving particles in real-time, especially when the particles are far from the initial focal plane. We proposed a method based on the iterative

Propagation of ultrashort pulses at least a few tens of optical cycles in duration through a negative index material is investigated theoretically based on the generalized nonlinear Schrödinger equation with pseudo-quintic nonlinearity and self-steepening effect. Novel periodic waves of different forms are shown to exist in the system in the presence of higher-order effects. It is found that such periodic

We report the measurement of one-body loss rates for magnetically trapped metastable europium atoms and the study of their loss mechanism. The loss of atoms observed in a magneto-optical trap is not fully understood because of the indivisibility of the loss regarding optical pumpings due to the presence of cooling laser beams. We magnetically trapped the atoms by directly loading from the magneto-optical

Low-cost tunable lasers have broad application prospects in optoelectronics. In this paper, a laser device based on fingerprint-textured cholesteric liquid crystal (CLC) was designed and fabricated, in which a narrow linewidth single-mode laser output on the side of the device was realized. The planar helical structure of the “fingerprint-texture” of CLC was obtained by the combined effect of externally

We demonstrate a multicompartment, power-scalable beam-line design in which sub-40-fs, terawatt field waveforms are tailored in space and time for downstream pulse compression to few-cycle pulse widths attained right at the site where the intense laser field interacts with a target. An accurate field-waveform characterization performed at multiple locations along the beam path shows that, despite all

In this paper, a polarization-insensitive reverse-ridge AlGaAs waveguide is designed for the supercontinuum generation. In the considered wavelength range from 3.4 to 8 μm, the dispersion profiles, nonlinear coefficients, and effective mode field areas for the quasi-TE and quasi-TM modes coincide well. The simulation results show that when pump pulse with wavelength of 4.2 μm, peak power of 4.8 kW

Based on the geometrical phase principle, we design an all-dielectric transmission coded metasurface in the near-infrared band. The all-dielectric unit cell is composed of silicon nanopillars and silicon dioxide substrate. We can encode design unit structures to build coded metasurface. We introduce the addition principle of encoding metasurface sequence into geometric phase metasurface. A new encoding

Amplification of single channel and three Wavelength division multiplexing (WDM) channels with 16 and 64QAM modulated signals is demonstrated using an SOA with holding beam in the non-transparency wavelength to minimize phase distortion. We demonstrate an optical gain of 10 dB for single channel and for each channel in WDM operation. We also show that, the performance with holding beam can provide

A method for the generation of tunable multi-degree-of-freedom rotations of vector beams on demand along a propagation direction is theoretically proposed. This generation can be achieved by a suitable vector superposition of three monochromatic non-coplanar beams, including a plane wave with elliptical polarization and two Bessel–Hermite–Gauss (BHG) beams with orthogonal polarization, the parameters

A seven-core fiber torsion sensor with microcavity structure based on intensity measurement is proposed. It is composed of a seven-core fiber (SCF) and two multi-mode fibers (MMF). The first end of the SCF has a microcavity structure. Because the mode fields between the MMF and SCF do not match at the splicing point, the phenomenon of mode interference will be formed between cladding modes and core

Combined laser–mechanical rock breaking drilling is an emerging technology that uses laser-assisted mechanical rock breaking to efficiently drill wells. A physical model of rectangular and circular laser spot scanning rock breaking is developed using the energy conservation theorem and heat transfer related theories, and the reasonableness of the model is analyzed through a combination of experiments

Based on the Huygens–Fresnelintegral and second-order intensity moments, analytical expressions for paraxial propagation, and the beam propagation factor (M2) of a circular cosine hyperbolic-Gaussian beam (CiChGB) have been derived. The propagation properties of a CiChGB in free-space including the beam width and M2 factor, and the beam focusing by a thin lens are numerically demonstrated. It is found

Parallax observations from adjacent CCDs have been applied to detect satellite jitter, and the highest detectable jitter frequency reaches up to half CCDs image line frequency, among which, however, not all frequencies’ jitter could be detected accurately. Jitter error mainly comes from the noise in offset data. In this research, it’s found that at some frequencies the noise is amplified significantly

In this paper, an asymmetric directional coupler (DC) based on a GaAs–CaF2 hybrid plasmonic waveguide (HPW) and a GaAs nanowire (NW) is designed for the mid-infrared polarization beam splitter (PBS). The mode characteristics of the GaAs–CaF2 HPW and GaAs NW-based PBS are simulated by using the finite element method (FEM). With the appropriate widths of the HPW and NW, the TE polarization mode in the

A three-dimensional measurement method based on frequency-carrier computer-generated moiré fringe is proposed. By projecting two sinusoidal gratings with π phase difference each other onto the measured object respectively and capturing the corresponding deformed patterns, the AC component of the deformed pattern can be extracted. When this AC component is respectively multiplied by actively designed

The typical defect detection method is based on the use of conventional cameras with limited dynamic range and image processing algorithm. Their identification efficiency is low particularly for industrial application because the light intensity from some highly reflective surfaces can easily exceed the maximum intensity limit of the sensor. In this paper, we take advantage of the fast spatial light

A tunable ultra-narrow band-stop filter based on metal–insulator–metal (MIM) plasmonic waveguide with square resonator is proposed and numerically investigated using Finite-Difference Time-Domain (FDTD) simulations. Different from straight waveguides with the same width, the proposed waveguide is composed of straight waveguides and ring waveguides with different widths. It is demonstrated that the

In this paper, low-loss Y-branch splitters up to 128 splitting ratio are designed, simulated, and optimized by using 2D beam propagation method in OptiBPM tool by Optiwave. For an optical waveguide, a silica-on-silicon material platform is used. The splitters were designed as a planar structure for a telecommunication operating wavelength of 1.55 μm. According to the minimum insertion loss and minimum