A novel clustering-analysis approach is proposed in this work. This approach addresses the fringe-activity range-detection issue often encountered in vertical-scanning wideband interferometry. The proposed approach exploits the fact that the fringe signal formed by a wideband light source, which is composed of deterministic signals and a random noise signal. As a result, the number of clusters in the

We report a real-time and highly sensitive liquid level sensor based on multimode interference to acquire the level measurement of high-RI liquids, e.g. oil, which probably poses promising applications in the motor-dom. The level sensor is fabricated by fusion splicing a short section of NCF between two SMFs. Level measurement with both low-RI and high-RI liquids have been studied; it is found that

In view of the current situation that the target optical remote sensing imaging simulation (ORSIS) is cumbersome and cannot be finely modeled, a method for obtaining the Spatially Varying Bidirectional Reflection Factor (SVBRF) of the target based on the hyper-spectral image sequence is proposed. Based on the characteristics of target surface illumination model, the bidirectional reflection factor

Dynamic phase demodulation techniques based on phase-sensitive optical time-domain reflectometry (ϕ-OTDR), including passive 3 × 3 coupler demodulation, offer significant potential in applications involving acoustic sensing and imaging. However, the main challenge to overcome in a ϕ-OTDR system based on a 3 × 3 coupler including eliminating the effect of the three output signals of the 3 × 3 coupler

Understanding spatter and melt pool dynamics during laser drilling remains a topic of considerable importance to determine the quality of processed materials. Due to metallic materials’ opacity to visible radiation, we studied the spatter dynamics outside of holes during laser drilling using shadow mapping. A 2D transient model for simulating laser material processing was implemented using COMSOL commercial

Here we analyze the propagation of Dyakonov surface waves(DSWs) at the interface between isotropic dielectric material and graphene-hBN hyperstructure (GhH) whose physical properties and optical topological transition regions can be controlled by varying the Fermi energy level of graphene sheets via electrostatic biasing. Various properties of the DSWs supported at the interface have been theoretically

Optical coherent burst-mode transmission can offer not only flexibility but also efficiency of the network resource utilization in elastic optical networks. We propose a new digital signal processing (DSP) scheme of coherent burst reception with a training sequence (TS) to solve the convergence problem of equalization caused by the interaction between fast-changing transient frequency offset (TFO)

A priori, all beams or pulses are subject to progressive spatial spreading along their propagation even in homogeneous media: Such an effect (diffraction) is always a limitation when the beam is desired to maintain its transverse shape. However, there are wave groups that can withstand diffraction; they are called Localized Waves or Nondiffracting Waves and, because of this property, their applications

Multi-photon scanning light-sheet microscope, which combines the advantages of light-sheet illumination and multi-photon excitation, has high axial resolution, low photobleaching, and a large field of view. However, as the light sheet goes deeper into the biological tissue, biological optical aberrations caused by the uneven refractive index inside the organism become non-negligible factors that dramatically

We propose a new local-binary ghost imaging by using point-by-point method. This method can compensate the degradation of imaging quality due to the loss of information during binarization process. The numerical and experimental results show that the target details can be reconstructed well by this method when compared with traditional ghost imaging. By comparing the differences of the speckle patterns

In this paper, we present an optical encryption system which uses the principle of unequal modulus decomposition and polarization vortex optical holography to implement encoding and decoding. Firstly, the original image is decomposed into two complex amplitude images by unequal modulus decomposition method, then their polarization states are changed by vortex beams irradiation, and finally they are

The absorption properties of one-dimensional quasi-periodic (Fibonacci and Thue Morse sequences) systems composed of Dirac semimetal are investigated. Numerical results show that nearly perfect broadband or narrowband absorption in mid-infrared range can be obtained using the same constituents with different sequences. For the Fibonacci sequence, a 90% absorption band with a relative bandwidth over

Plasmonic nanolasers (PNLs) have attracted much attention in recent years due to their light-trapping capabilities beyond the diffraction limit. However, the physics that underpins the lasing action in such devices has not received sufficient treatment in the literature. The contribution of plasmons in PNLs needs to be understood at a granular level for designing enhanced nanoscopic lasers. In this

When imaging through fog using Geiger mode avalanche photon diode (Gm-APD) ladar, strong backscattering photons make it difficult to effectively extract an accurate target signal via the traditional peak-select algorithm. Single-parameter estimation (SPEA) is proposed in this paper to solve this problem. First, the physical properties of the gamma distribution model’s characteristics are analyzed,

In this work, a waveband tunable and switchable multi-line ring-cavity fiber laser is presented. Here, the losses of the cavity are controlled by means of a variable optical attenuator (VOA) and a thermal sensitive interferometric filter, which was formed by a stack of 3 layers at the tip of an optical fiber and a long thermal sensitive sleeve. Thus, the laser can emit single–, dual–, triple–, quadruple–

We theoretically investigate and propose a promising 8-mm-long cascade planar waveguide made of Si3N4 and As2Se3 glass system for mid-infrared supercontinuum generation by employing a commercially available femtosecond pump source operating at 1550 nm wavelength. A rigorous numerical investigation has been performed considering three different dispersion regions of the optimized cascade waveguide for

In this work, the method of etching the metal-ion-implanted dielectric via a patterned electron beam (EB) resist mask was used to fabricate the metal/glass nanocomposite arrays with prospective applications. Following the method, the Au/SiO2 nanocomposite arrays with an expected square grid of 600 nm periodicity (50% in the duty cycle) were fabricated. Experimental results revealed that the fabricated

Fluorescent optical fiber temperature sensors require high-performance silicon-based single photon detectors with large-scale on-chip integration capabilities to improve the detection accuracy of the system. Therefore, this paper proposes a gate-controlled single photon avalanche diode (GC-SPAD) with high photon-detection-probability (PDP). In order to verify the high photon-detection-probability,

In the 10 GSymbol/s/λ coherent PON downlink system with I- and Q-axis mapping for different optical node units (ONUs), an extra power transmission happens because of the transmission difference between the ONUs. An adaptive IQ imbalance modulation with optimum IQ power loading for two ONUs is introduced at the transmitter-side digital signal processing (DSP). For scaling of the IQ power ratio setting

Enhancing and engineering the Goos–Hänchen (GH) shift of two dimensional layered materials provides a powerful way to realize the novel optoelectric devices. Here we report an enhanced and controlled GH shift in the hybrid structure consisting of monolayer graphene and multilayer photonic crystals grating structure by using the rigorous coupled-wave analysis and stationary phase method, whose value

In this letter, by incorporating hybrid structure of no-core fiber (NCF)-graded index multimode fiber (GIMF) as the saturable absorber (SA) and spectral filter simultaneously, not only the switchable noise-like pulses (NLPs) but also the tunable single- and dual-wavelength dissipative solitons (DSs) are obtained from a net normal dispersion Yb-doped mode-locked fiber laser. The NCF-GIMF device plays

We report a photonic crystal (PhC) sensor array consisting of six nanocavities which are side-coupled to a linear PhC waveguide. The design approach to cavities is based on rotating functional holes and changing their radius. Based on traditional linear waveguide, we also design a PhC waveguide with enhanced bandwidth by adjusting the holes on both sides of the central linear defect to weaken the Bragg

In this paper, we propose and numerically investigate a new non-reciprocal optical device enabling enhanced optical TE mode isolation at telecom wavelength, compatible with applications. The principle is based on magnetoplasmonic interaction between a garnet waveguide and a side-coupled gold grating. Grating nanoslits host Fabry–Perot resonances that couple to Surface Plasmon Polaritons excited at

We propose a methodology for producing twin equal-intensity optical vortices with the same topological charge along the propagation direction by combining m-bonacci sequence with the spiral zone plates in the squared radial coordinate. Based on the Fresnel diffraction theory, the focusing property of such optics was analyzed and experimental demonstration was performed to verify its effectiveness.

The canonical boundary-value problem for the propagation of compound plasmon-polariton (CPP) waves, guided by a symmetric structure comprising a metal film embedded in a uniaxial dielectric material, was formulated and solved. In addition to unexceptional CPP waves whose field strength, in the dielectric material, decays exponentially with distance from the nearest dielectric/metal interface, this

A novel fiber bending sensor is proposed based on a home-made seven-core fiber (SCF). The sensing head is formed by splicing a piece of a SCF between two sections of single-mode fibers(SMFs). Two super modes with most of mode energy in the central fiber core and in the six outsider fiber cores are exited in the SCF, which ensures the Mach–Zehnder interferometer (MZI) structure of the proposed sensor

Fused silica has been widely used as optical components in radiation environment. Some optical components used in these applications are frequently exposed to X-rays and other ionizing radiation, leading to the increase of optical absorption and decrease of laser-induced damage threshold, thus undermining their optical properties and operational lifetime. As on-line heating is difficult to achieve

In this paper, we investigate double slot waveguide configuration to explore the actively tunable electromagnetically induced transparency (EIT) effect in the terahertz regime. One of the slot structures is filled with a dielectric material of certain refractive index which causes a slight shift in the its resonance frequency as compared to the unfilled slot. The two frequencies say, ω1 and ω2 from

We proposed and demonstrated an optoelectronic oscillator (OEO) based temperature sensor with high sensitivity and precision. The sensor is realized using a silicon-on-insulator-based microring resonator (MRR) and a dual-loop structure. The MRR, which acts as a sensing probe, is optimized and designed to have an ultra-high Q factor and high sensitivity to temperature variations simultaneously. The

Broadband control of polarization state is essential for terahertz applications ranging from non-destructive testing to imaging in medicine and wireless communications. We present a single-layered terahertz anisotropic metasurface quarter-wave plate consisting of hybrid metallic wire grating arrays, which enables broadband linear to pure circular polarization conversion with an ellipticity over 0.99

A temporal phase-truncated double random phase encoding cryptosystem is proposed to be improved by replacing the temporal Fourier transformers (TFTs) of the dispersion-time lens-dispersion structure with temporal skew Fourier transformers (TSFTs). A TSFT is similar to a TFT except for the time lens (TL) replaced by a skew time lens (STL). A STL is a temporal analog of a spatial cylindrical lens with

For a high-speed infrared guided missile, the supersonic mixing layer over the optic window causes the aero-optical transmission effects such as target image blurring, jittering, and offsetting. The large eddy simulation is used to simulate flow of the supersonic mixing layer and the ray tracing is used to compute transmission path of the beam passing through a vortex, and three parameters are proposed

As an anti-reconnaissance method, infrared stealth technology has been paid more and more attention. With low infrared emissivity and high reflectivity in the infrared band, aluminum (Al) with face centered cubic crystal structure is widely used in the research of infrared stealth materials. However, due to the similarly high reflectivity of metal Al in the visible band, the compatibility between infrared

A new approach for generating sub wavelength scale one dimensional chain of magnetic spot, hole, flattop and bubble profiled segments using tightly focused phase modulated azimuthal and radial variant vector (ARVV) beam is proposed and investigated numerically using vector diffraction theory. Numerical result shows that by using a well optimized single Complex Phase Filter (CPF), one can generated

A method suitable for recording radial-shearing holograms is proposed. By inserting a phase-shifting Theon-ladder zone plate at the Fourier plane of Kepler telescope, perfectly matched interferogram can be obtained with high contrast and good quality. Good image quality should meet not only theoretical resolution, but also good interference contrast. Interference pattern generated by the multicopies

A new multiplexed system based on double imaging Mach–Zehnder interferometry is proposed in this study for the simultaneous measurement of out-of-plane deformation and its first derivative. A modified Mach–Zehnder interferometer is used in the proposed system as shearing device, which has two pairs of imaging lenses and apertures placed on its arms. Therefore, carrier frequency and shearing amount

In digital holographic 3D display, the limited size of the spatial light modulator (SLM) restricts the viewing angle of reconstructed images. Tiling multiple SLMs can improve the viewing angle but this method brings much increased cost and takes up large space. In this paper, we propose using boundary folding mirrors to expand the viewing angle of holographic display system. The size of the SLM is

We study the quantum effects of entanglement between continuous-mode photon and phonon fields in waveguide channels that are coupled to an optomechanical resonator structure with two optical modes. We show that such optomechanical resonator–waveguide system can drastically enhance the efficiency for generating entangled traveling photon–phonon single pairs, and can serve to implement controllable continuous-mode

In the present work, we demonstrated a mode-locked polarization-maintaining (PM) Yb-doped fiber laser based on the figure-of-nine configuration to generate ∼100 fs pulses at 1μm. For the dispersion management, a pair of gratings was inserted into the laser resonator to compensate the group delay dispersion (GDD). The stable, self-started passive mode-locking operation was realized with a pulse duration

We theoretically demonstrate a transversely polarized ultra-long optical needle with lateral width beyond diffraction limit generated by tight focusing of a cylindrical polarized circular Airy Gaussian vortex beam (CAiGVB). According to the calculation expression derived through the Richard-Wolf diffraction theory, the properties of optical needles are investigated in simulation in detail. The analysis

Previous studies on non-uniformly correlated (NUC) beams mainly focus on beams with Gaussian amplitude profiles. In this paper we research a new class of non-uniformly correlated flat-topped beams, which are called convex partially coherent flat-topped (CPCFT) beams. Using wave optics simulation (WOS), we investigate the propagation properties of such beams in vertical atmospheric turbulent paths in

In this work, a 1.9μm Tm:YLF high-order vortex laser output is realized for the first time based on LD off-axis pumping technology. By adjusting the off-axis displacement of the output coupling mirror accurately, the maximum topological charge up to m=20 for stable Hermite–Gaussian (HGm,0) mode is achieved. The conversion of high-order HGm,0 to Laguerre–Gauss (LGm,0) modes are further realized by a

The adaptive optics system (AOS) has been used to eliminate the effect of atmospheric turbulence for free-space optical communications. The AOSs are designed based on the statistical average performance of the turbulence. In reality, the amplitude of turbulence changes drastically, and the AOS cannot always detect and correct the aberrations appropriately. To prevent the amplitude of turbulence from

In this communication we demonstrate a new characterization technique combining Fourier transform (FT) spectroscopy and second harmonic generation (SHG) that enables high spectral resolution with broadband femtosecond laser pulses. The strong and narrow exciton resonances of the wide band gap semiconductor ZnO were chosen for demonstrating the capabilities of the method. FT-SHG offers high reproducibility

Miniaturized ultraviolet spectrometer is promising for on-site accurate detections. In this work, a high-resolution on-chip ultraviolet spectrometer is designed and analyzed. MgF2 and Al2O3 are selected as the substrate and core material of the waveguide, respectively, resulting in a low bending loss of 1.5 dB/cm at a radius of 3 μm and wavelength of 278 nm. The spectrometer is designed as a cascaded

Trivalent Sm3+ doped multi-component borate glasses 10ZnO -20PbO-10Na2O-(60-x) B2O3-xSm2O3 (where x=0.25, 0.5, 0.75, 1, 1.5, 2 mol %) were made and assessed for their applications in the field of lasers and photonic devices. Various techniques were undertaken and the spectra (XRD, FTIR, UV–Vis–NIR, PL and CIE chromaticity coordinates) were recorded to study the relevant properties of prepared glasses

During laser manufacturing, the inevitably generated thermal stress may lead to cracks and defects, thus resulting in work-piece damages. In order to optimize laser manufacturing to inhibit the stress, detailed analysis on the time-varying stress field is necessary. Compared to experimental stress measurement requiring expensive setups and complicated procedures, numerical stress calculation techniques

We demonstrate dual-comb time-of-flight absolute distance measurement with a free-running dual-wavelength dual-comb mode-locked Er-fiber laser. An anodized aluminum plate with 1.6-μm RMS roughness that locates at a distance of ∼3.46 m serves as a scattering target. The echo has been collected non-coaxially with a 5-inch aperture telescope. The target time-of-flight is acquired by linear optical sampling

A secure, robust, and blind watermarking method based on computational ghost imaging (CGI) in the discrete wavelet transform domain is proposed. In this method, an original watermark is firstly encrypted by the CGI system with chaotic key, then the sequences of the ciphertext are quantified into two levels and hidden in the wavelet coefficients of a host image. The quantization on the ciphertext compresses

When working with the method of projected fringes outside the optical laboratory one often encounters the problem of uncontrollable ambient light. This might cause saturation of the camera which in turn results in clipping of the fringes. Since standard theories describing phase-shifting techniques assume the projected fringes to be purely sinusoidal, such clipping will result in measurement error

An acousto-optic modulator (AOM) was used in combination with two-beam multipoint laser Doppler velocimetry (MLDV) to achieve advanced blood flow observation for simultaneous determination of the magnitude and direction of the blood flow velocity. To measure the shear stress around the blood vessel wall, especially in regions near obstructions, the shear rate (velocity gradient) in a pulsatile blood

The formula of refractive index n, which is derived recently from the electromagnetic induction refraction mechanism, contains a parameter V, i.e., the equivalent volume of electron cloud. Dozens of calculated n results by using this formula in previous researches are in good agreement with the measured ones. V determines some properties of materials, such as refractive index and band gap. It is not

We demonstrate a laser far field scattering method to detect droplets efficiently. The scattering from droplet include transmission and reflection patterns, and the relation between the intensity distributions of scattering and the surface tension, refractive index of the liquid droplet were derived out theoretically. In our experiment, the stable transmission and reflection patterns from droplets

In this article, a panda-like silicon core based photonics crystal fiber was proposed and applied onto a polarization filter. Au film coating surrounding the air holes acted as a plasmonic active metal. Using the Finite element method, the quality of the proposed fiber was investigated, including confinement loss and extinction ratio. By adjusting the length of the proposed fiber, the applicable operating

There is presently an increased research activity in understanding the nature of optical force when ultrashort pulsed excitation is used to trap and manipulate objects with sizes ranging from micrometers down to nanometers. Such a nonlinear laser tweezer is peculiarly promising because the nature of the force can be dramatically tuned owing to optical nonlinearity. However, accurate measurement of

Due to the speckle effect in the laser self-mixing interference (SMI), the signal amplitude will fluctuate greatly, which will affect the measurement accuracy and range. The angle measurement method based on speckle affected SMI signal is presented. The high frequency and low frequency noises in SMI signal can be filtered out simultaneously by variable mode decomposition. The envelope of SMI signal

We numerically studied the spin-dependent optical torque on a 2D chiral plasmonic nanomotor excited by circularly polarized lights. An interesting phenomenon of so-called negative optical torque is demonstrated on condition that the scattering optical torque is opposite to and larger than absorption optical torque under a plasmonic resonance of dipolar mode. Moreover, the calculated optical torque

A novel primary colors filter (RGB filter) is designed with ultra-compact size by using the inverse design method. The core size of filter goes to 0.5μm×0.55μm, and then the chip integration being high enhanced. The transmission characteristics of RGB filtering are simulated by FDTD algorithm. A high performance and high compact coupling region can be obtained by using inverse design method to search

In this paper, we propose an arc-shaped metasurface carpet cloak based on generalized sheet transition conditions. The main idea behind this invisibility is phase compensation through local phase modulation, in which the front of the reflected wave is reshaped just as the incident wave hits the flat mirror. Secondly, we have implemented an arc-shaped metasurface carpet cloak based on a cavity structure

In this paper, a highly accurate correction method for errors caused by spherical aberrations in long focal length measurements based on divergent light and Talbot interferometry is presented. Simulations and analysis indicate that spherical aberrations are key factors affecting the precision of moiré fringe angles, which are ignored in most methods yet. Moiré fringes are transformed into frequency