Light beams with helical phase-fronts are attractive for many optical applications, such as optical tweezers, particle manipulation, and other optical applications. A superoscillatory metalens has been designed for an azimuthally polarized wave at a wavelength λ = 632.8 nm. Numerical simulation demonstrates that a superoscillation hollow dark spot is generated. The transverse inner FWHM is 0.358λ overcoming

High-speed laser shadowgraphy is crucial in range testing. We report the design, development, and application of a dual-sequence large-scale high-speed laser retroreflective shadowgraph system (DLH-LRSS) to monitor large-scale transient phenomena on a field-test range. The DLH-LRSS is based on the retroreflective technique. The narrow pulse width laser can effectively freeze ultrahigh-speed processes

Antireflection (AR) coatings allow increased substrate transmission and reduce surface reflection over a specific wavelength range. We proposed a blue-blocking (BB) AR coating that allows maximal visible-light transmittance while minimizing the transmittance of blue light, owing to selective absorption. Admittance diagrams of BB Cr2O3 / SiO2 coatings and traditional AR Ta2O5 / SiO2 coatings were shown

An ultracompact transverse electric (TE)-pass/transverse magnetic (TM)-stop power divider using subwavelength gratings (SWGs) and hybrid plasmonic waveguides (HPWs) for 1.55 / 2 μm is proposed and analyzed, where SWGs are, respectively, embedded in a partially etched taper within the input waveguide to form an SWG transition and input taper/output inverse tapers in the bottom layer to construct an

To serve the changing needs of road traffic control, the road space and road structure surrounding an intersection have evolved into complex forms. The redesign of the trajectories, though complex, can be accomplished by the application of methods for navigation, guidance, and combination of expert knowledge of road traffic control of vehicles, using a concept of request/response in a two-way-to-way

The problems of low-contrast, blurred images, and low-edge details are encountered in infrared images. These undesirable features affect infrared imaging applications in military, science, medicine, and other fields. Therefore, a method of edge detection based on heat conduction matrix (HCM) has been proposed to show or sharpen the edges of objects in infrared images. First, the heat conduction formula

We demonstrate a technique for fabricating microstrip patch antennas using femtosecond laser patterning followed by ultraviolet beam and chemical treatment. Initially, we design the physical parameters of both single-slot and double-slot microstrip patch antennas and simulate them using high-frequency structure simulator for optimization. Simulation results exhibit a return loss of −26 dB at the resonant

The stokes vector (SV) has been known since Stokes used it to represent the state of polarization (SOP) of light. While the polarization of light has been represented in the form of a SV since 1852, it has more recently found many applications in polarization management in optical communication. Our review begins with the mathematical representation of the SV. The system capacity in the optical transmission

This guest editorial introduces the Special Section on Active Spectroscopy.

Mid-infrared (MIR) laser spectroscopy measurements coupled with multivariate analysis (MVA) routines were applied to detection and classification of high explosives (HEs) deposited on aluminum and acrylonitrile butadiene styrene substrates. An MIR quantum cascade laser (QCL) was optically coupled to a grazing angle probe (QCL-GAP) mount to operate in diffuse reflectance mode at an incidence angle of

Trace chemical detection and classification in stand-off reflection-based spectroscopic data is challenging due to the variability of measured data and the lack of physics-based models that can accurately predict spectra. Most available models assume that the chemical takes the form of spherical particles or uniform thin films. A more realistic chemical presentation that could be encountered is that

Pupil densification is a technique to improve contrast in a direct imaging interferometer. By enlarging the size of each aperture in a sparse array, the fraction of energy contained in the central point spread function peak can be increased. However, the effective field of view is reduced as the contrast improves. Our work investigates the optimal strategy for pupil densification in the context of

We propose a logic optical projection tomography (LOPT) method to realize full-view, three-dimensional (3-D) shape parameters measurement and visualization for opaque objects. The main innovation of LOPT is use of a logic process to obtain high-contrast and homogeneous boundary projection signals. According to the reconstructed 2-D cross-section images, the structure characteristic points in each slice

A digital method is proposed whereby spatial speckles created when an optically rough surface is illuminated by a diffuse coherent laser beam are used to generate slope contour fringes. This is done by photographing the speckles contained in a parallel plane in front of the plate before and after deformation. The resulting photographs are then fast Fourier transformed twice and numerically compared

Spatial interpolation using radial basis functions (RBFs) is compared with standard natural neighbor interpolation for the purpose of populating dead zones in optical path difference (OPD) wavefront data collected through aero-optics turbulence. Both methods, and some other commonly used basis functions, are described in detail. These candidates are applied to experimental subscale turbulent wind tunnel

The single collimating lens-based dual-beam exposure system is a holographic exposure system that is suitable for fabricating long-period gratings. The interference wavefront aberration in this system requires optimization. We analyzed the coma of a single collimating lens-based dual-beam exposure system, and the linear relationships between the coma and the positions of the pinholes and substrate

We present an optical set up that significantly reduces the ghost images appearing due to multiple reflections on both surfaces of the combiner (typically the windshield) of head-up display (HUD) systems. The method is based on an optimized polarization correcting optics attached to the HUD projector. For the quantitative investigation of the ghost images, we calculate the ghost image suppression ratio

High powered optical amplifiers (HPOAs) are a key subassembly in free-space optical communication systems. As these free-space optical communications systems are being introduced into space applications, it is critical to assess the impact of the radiation environment present in space on the reliability of these systems. One key component in HPOAs is multimode laser diodes, which are used to pump gain

We present a design for a unit magnification imaging relay that is compact. The design uses two mirrors, and one is used by light twice for a three-reflection system. The mirrors are specified with freeform surfaces. There are several tradeoffs of performance depending on field of view, F / #, and wavelength range. One example provides a 30-mm circular field of view at F / 2.8, and another example

Terahertz time-domain spectroscopy (THz-TDS) is one of the main research platforms for terahertz (THz) science and technology. However, a traditional system is not only bulky but also has some limitations in detecting micro and liquid samples because of the large THz beam spot dimensions and the strong THz-wave absorption by water. We have developed a THz-TDS measurement chip by directly fabricating

We propose an all-fiber configuration of tunable bandpass filter (TBPF), consisting of a mode selective coupler (MSC) and an acoustically induced fiber grating (AIFG). Either the MSC or the AIFG can act as high-order mode converters in a few-mode fiber. The working wavelengths of the MSC and the AIFG are chosen to achieve complete conversion cycle between the core-mode linearly polarized (LP01) mode

A two-sectioned InAs/InP quantum dash laser structure is proposed and investigated as a monolithic broadband multimodal tunable laser with an integrated semiconductor optical amplifier. The optical power-injection current and spectral characteristics of the device at different operating conditions demonstrated a total wavelength tunability of ∼15.8 nm in the extended-L-band (∼1615 to ∼1630.8 nm) window

The photoresponse mechanism of graphene/InSb heterojunction middle-wavelength infrared (MWIR) photodetectors was investigated. The devices comprised a graphene/InSb heterojunction as a carrier-injection region and an insulator region of graphene on tetraethyl orthosilicate (TEOS) for photogating. The MWIR photoresponse was significantly amplified with an increase in the graphene/TEOS cross-sectional

We report a simple refractive index (RI) sensor based on a twin-hole fiber (THF). The THF is fused with the single-mode fiber to realize sensing by the multimode interference. The mode transmission characteristics in the THF are numerically investigated. In the sensing experiment, when the surrounding RI changes, the wavelength shift of the transmission spectrum shows approximate linearity in the low

Based on chaotic biological cryptography and computer-generated holography, a symmetric–asymmetric hybrid encryption and decryption system was proposed. This method has multiple keys, in which two decryption keys are different from the encryption keys. The encryption and decryption system possesses both symmetric and asymmetric key cryptography features. The biometric code is unique and unchangeable

The vehicle LIDAR has been widely used in the fields of three-dimensional city modeling, terrain mapping, the agroforestry ecosystem, military detection, and unmanned driving for its advantages of high resolution, strong anti-interference ability, small volume, and light weight. The measurement accuracy of vehicle LIDARs is influenced by the internal heat source of the system and the external ambient

Scattering of light from a surface depends on its microroughness. In general, total integrated scattering of a surface is expressed in terms of root-mean-square microroughness (σrms) using empirical relations. These empirical relations assume that the σrms is measured over the spatial scales ranging from 0 to surface length/diameter (L). In reality, σrms will be measured over finite spatial lengths/scales

With the increase in digital image correlation (DIC) applications, it is an important task to realize the fully automatic measurement and provide an automatic deformation measurement sensor. Keeping this in mind, we propose an automatic speckle region selection method for DIC. This method can be divided into three main steps: initial contour selection, active contour computation, and morphological

As optical distribution frames (ODFs) carry increasing amounts of data, issues relating to their port management are becoming crucial. Image backhaul inspection has been widely accepted as an effective technology to monitor the occupancy status of ODF ports. However, the massive amount of on-site images requires a large team of off-site technologists to manually identify the occupancy status of each

A multirod solar side-pumping concept is proposed to study the feasibility of multirod/multibeam laser systems in large-sized solar furnaces. This scheme was based on the one-megawatt solar furnace (MWSF) in Odeillo, France, which collected and concentrated solar rays into an input face of a solar homogenizer placed at the focal zone. At its output face, 12 laser heads were positioned, each of which

Fiber optic microstructure turbulence sensors (FOMTS) with fiber Bragg gratings can measure the rate of tangential velocity change caused by ocean turbulence. The theoretical principles of the FOMTS and demodulation were verified by a prototype. The demodulation system resolution reached 0.001 pm / Hz, the sensitivity was 4.37 × 10 − 16 m2 s2 / kg, and its natural frequency in air was 595 Hz, similar

Holographic search algorithms such as direct search (DS) and simulated annealing allow high-quality holograms to be generated at the expense of long execution times. This is due to single iteration computational costs of O ( NxNy ) and number of required iterations of order O ( NxNy ) , where Nx and Ny are the image dimensions. This gives a combined performance of order O(Nx2Ny2). We use a technique

Currently, the highest power quantum cascade lasers (QCLs) include (i) an efficient active region design, which minimizes the energy fraction transferred into heat, (ii) a relatively large number (40) of cascades, which increases the mode confinement factor, Γ, and (iii) narrow buried-heterostructure waveguides, which efficiently cool the active region through efficient lateral heat flow. This combination

Our paper presents the design, fabrication, and characterization of metamaterial absorber-based microwave imaging detector that is operating in industrial, scientific, and medical (ISM) band. The results reveal that the structure has almost perfect absorption at 2.39 GHz in the simulation and 2.51 GHz in the experimental measurement. For energy-harvesting applications, Schottky diodes have been used

Hyperspectral cameras capture images where every pixel contains spectral information of the corresponding small area of the depicted scene. Spatial misregistration—differences in spatial sampling between different spectral channels—is one of the key quality parameters of these cameras, because it may have a large impact on the accuracy of the captured spectra. Spatial misregistration unifies various

Traceable, highly accurate calibration of wavefront sensors such as Shack–Hartmann sensors is a challenging task and an active field of research. We have developed a measurement system for the traceable calibration of wavefront sensors employing spherical wavefronts and a point light source in combination with a three-axis linear stage. We obtain an absolute calibration of sensor errors, including

A photonic crystal fiber (PCF) made up of a spider-web such as cladding and an octagonal core is proposed for sensing applications. Three widely used industrial liquids and/or by-products, namely, water, acetic acid, and glycerol, have been investigated using the full vector finite element method. Extremely high sensitivities of 99.5%, 99.7%, and 99.9% were achieved at 4.5 THz for water, acetic acid

This erratum corrects an error in Eq. 1.

Four different methods for calculating the radial profile of the Fourier transform of a circularly symmetric function are discussed and evaluated. Applications to optics, in which the circularly symmetric function represents the distribution of field across a circular aperture, are many. The four approaches include: (1) numerical integration of the zero-order Hankel transform equation (using the Gauss–Kronrod

We present five-splitting equal-intensity laser output based on a T-shaped reflection grating under normal incidence, which is aimed to reduce polarization loss. Although five-splitting has been reported by a single-layer grating, a set of parameters can only be effective for either TE or TM polarization. Both TE and TM polarizations can be operated simultaneously by T-shaped arrays. For only one set

Editor-in-Chief Michael Eismann reflects on the responsibilities of mentorship.

This guest editorial introduces the Special Section on Atmospheric Propagation.

We advance the benefits of previously reported four-dimensional (4-D) weather cubes toward the creation of high-fidelity cloud-free line-of-sight (CFLOS) beam propagation for realistic assessment of autotracked/dynamically routed free-space optical (FSO) communication datalink concepts. The weather cubes accrue parameterization of optical effects and custom atmospheric resolution through implementation

Performance metrics such as mean-bit-error rate and probability of fade for free-space optical communication (FSOC) applications using intensity-modulation direct detection are theoretically calculated based on probability density functions (PDFs) describing irradiance fluctuations. Theoretical calculations using common PDF models can result in significant errors in prediction of performance metrics

Simulating atmospheric turbulence is an essential task for evaluating turbulence mitigation algorithms and training learning-based methods. Advanced numerical simulators for atmospheric turbulence are available, but they require evaluating wave propagation, which is computationally expensive. We present a propagation-free method for simulating imaging through turbulence with applications in ground-to-ground

Underwater imaging has been increasingly employed in vision-based marine research. However, the inappropriate installation of a light source and the complex underwater environment will result in the uneven illumination and overexposure on the captured images. To address these issues, an underwater image enhancement framework for autonomous underwater vehicles platform is proposed, which consists of

We present a solution to the problem of light scattering by spherical particles, adapted for interpreting the signals of portable lidars for autonomous vehicles. The solution was obtained for typical wavelengths used in laser sensing tasks: 0.355, 0.532, 0.905, 0.940, 1.064, 1.55, 2.15, and 10.6 μm. The solution was obtained within the framework of the Mie scattering theory for water and ice. The inherent

Lensless inline digital holographic microscopy (LI-DHM) and Fourier ptychographic microscopy (FPM) are two widespread quantitative phase imaging (QPI) techniques. They have been employed in various fields, especially for biological slice imaging because of their simplicity in use, stability in structure, and also large field of view. Spherical phase response (for example from HeLa cells) is commonly

To improve the phase-measuring profilometry measurement speed, phase-shifted fringes can be encoded into color channels. However, for colored objects, the intensity of the fringes in each channel is affected by surface texture. Therefore, a measurement method based on color coding and sinusoidal correction is proposed. First, two color images are encoded. The red (R) and blue (B) channels for the first

The determination of residual water content is vital for the quality control of high explosives, such as octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX). However, conventional analytical methods are time-consuming and inaccurate. We have proposed a simple, sensitive, and accurate method for moisture determination based on terahertz (THz) time-domain spectroscopy. A model based on effective medium

Aiming at small size, compact structure, strong light-collecting ability, and low loss requirements of optical coherence tomography (OCT) probes used for human body detection, we design an all-fiber OCT probe, which is composed of a single-mode fiber and a multimode fiber (MMF) with spherical lens. By measuring the optical performance of these probes, we found that, when the length of the MMF of the

A laser signal simulation system based on a backward transmission screen is proposed. The system is used to test the performance of laser-guided weapons in a laboratory environment. The system enables the simulation of the laser-guided weapons by controlling the movement of a two-axis motor and changing the laser intensity. In addition, using the ScramNet ring topology, real-time hardware-in-the-loop

Durable window materials with minimal optical loss are important for future high-energy laser (HEL) systems that will operate at or near the megawatt level. Sapphire is recognized as a promising HEL window candidate due to its outstanding optical transparency and mechanical properties. However, its weak scattering characteristics and absorption levels near the 1-μm wavelength region need to be lowered

Recently, the use of carrier frequencies in the domain of wireless bearer has been enhanced to fulfill the data transmission need. The research activities are coordinated to wireless communication with high information rates and amended security. An idea of the slotted rectangular patch antenna that depends on the photonic crystal structure is offered for a wireless communication system. The proposed

In a homeland security setting, the ability to detect explosives at a distance is a top security priority. Consequently, the development of remote, noncontact detection systems continues to represent a path forward. In this vein, a remote detection system for excitation of infrared emissions using a CO2 laser for generating laser-induced thermal emission (LITE) is a possible solution. However, a LITE

We are using active infrared (IR) spectroscopic imaging to detect trace explosives on surfaces at proximal distances up to a few meters. The technology comprises an IR quantum cascade laser (QCL) for illumination and an IR focal plane array (FPA) sensor to collect signal backscattered from surfaces of interest. By sweeping the wavelength of the QCL while collecting image frames with the FPA, we generate

Standoff detection of hazardous materials using infrared backscattering spectroscopy shows promise due to its speed of detection, sensitivity, chemical specificity, eye safety, and the ability to perform detection in a stealthy manner. However, infrared diffuse reflectance spectra of trace particles on substrates exhibit a strong dependence on substrate type, particle size, and mass loading. This has

Since solids are only sometimes seen en masse in a pure bulk form, and for liquids other than water almost never, a capability to model reflectance spectra from analytes deposited on various substrates would be highly advantageous. If available, the real, n ( ν ) , and imaginary, k ( ν ) , components of the complex refractive index, n∼ = n + ik, can be used to simulate infrared spectra, accounting

An experiment was conducted to study turbulence along a 149-km path between the Mauna Loa and Haleakala mountain tops using digital cameras and light-emitting diode (LED) beacons. Much of the path is over the ocean, and a large portion of the path is 3 km above sea level. On the Mauna Loa side, six LED beacons were placed in a roughly linear array with pair spacings from 7 to 62 m. From the Haleakala

To obtain a real-time noninvasive analysis of the content of the aqueous humor (AH) in the eye, a confocal dark-field ophthalmic probe was designed and optimized by ray-tracing software. The confocal technique allows Raman spectrometric sampling of the AH with suppressing signals from the surrounding tissues. Dark-field illumination prevents the excitation light to reach the vulnerable retinal tissue