The International Organization for Standardization (ISO), in collaboration with the academic community, has developed and published a comprehensive system of standards for the characterization of optical components and laser beams. Our study offers a pedagogical introduction to the theory and application of laser beam characterization in accordance with ISO 13694:2018 and ISO 11145:2018. The characterizing

The presence of haze degrades the quality of a captured image. The aerosols in the atmosphere cause scattering of the incident light, and this phenomenon is observed on the captured image as well, where some regions appear grayish and colors in those regions appear faded. To improve the quality of the hazy images, we propose a joint fusion and restoration model that sufficiently enhances the contrast

Until now, sea fog monitoring relied mainly on point monitoring equipment, such as a forward scatter visibility sensor mounted on the shore or on an island, which produce non-ideal data during a variable and unevenly distributed sea fog. In 2019, a visibility lidar instrument for sea fog monitoring was installed in the Beilun area of the Ningbo Zhoushan Port, China. Two sea fog events were monitored

A deep learning-based method is proposed to recover the absolute phase value from a single fringe pattern. We propose a deep neural network architecture that includes two subnetworks used for wrapping phase calculation and phase unwrapping, respectively. The training set is generated with the absolute phase obtained by the combination of phase shifting and gray coding. In addition, a reference plane

In large-scale imaging or measurement, a rotating photogrammetric system with a camera fixed on the surface of the turntable can be used to extend the field of view of the camera with the rotation of the turntable. The camera’s projection center needs to be located at the rotation axis of the turntable, so the images captured during the sequentially rotating share the same projection center. It is

The separation of complex inner and outer contours of glass articles with curved surfaces using ultrashort pulsed lasers is reported. Single-pass, full-thickness modifications along the entire substrate are achieved using a processing optics that allows for beam shaping of non-diffracting beams and, additionally, for aberration compensation of phase distortions occurring at the curved interface. The

We report an approach for generating an evenly spaced, flat, and spectrally broad optical frequency comb (OFC) by the exploitation of gain modulation experienced by a fourth-ordered periodic Gaussian pulse train. The spectrally flat OFC generator is realized by propagating the periodic optical pulse through high gain SOA. The spectrum flatness limits up to 10 dB for 102 frequency lines, which is improved

We present the evaluation and comparison of four different polymers (VeroClear, ClearVue, LOCTITE 3820, and WaterShed) to produce macro transparent optical components using additive manufacturing. The refractive indices were measured at increasing temperatures. The Cauchy and Sellmeier coefficients were fitted subsequently. We used the measured and calculated parameters to determine the Abbe numbers

The measurement of the refractive index of optical glass samples is a common and fundamental activity in numerous fields of expertise. Several measurement techniques exist with relative accuracies from 10 − 2 to, at least, 10 − 7 with complexities that are inversely related to the corresponding uncertainty. We describe an implementation of a technique based on the measurement of the lateral displacement

In order to resolve the problem of speckle interference phase map noise interference, a phase denoising method of digital speckle pattern interferometry based on empirical wavelet transform (EWT) and cross correlation is proposed. First, the EWT is used to decompose the speckle phase map, and a series of components is obtained. Then the noise-free components containing phase information are extracted

Current optofluidic devices are analog focus-tunable elements with a continually varying focus between foci. An innovative digitized optofluidic element was developed to enable fast switching between the foci. The operation involves an internally placed elastic membrane of changing shape between the refractive and diffractive forms with a tiny amount of fluid transfer by a micro-actuator. This allows

We propose a miniature anamorphic lens design that records wide-screen videos on an ordinary CMOS format. The front group consists of two freeform lenses, which achieve different focal lengths in the two orthogonal directions and thus enable the anamorphic characteristics. The rear group is made of rotationally symmetric aspheric elements that relay the image on the sensor. The annularly stitched extreme-point-based

A high-repetition pulsed Nd : YVO4 laser based on the multi-longitudinal-mode beat note is presented. The mechanism of multi-mode oscillating in the Nd : YVO4 laser with FP cavity is analyzed. With the multi-mode Nd : YVO4 laser in experiments, it is found that the more longitudinal modes beating in the laser cavity, the narrower time duration of the laser pulse is obtained. An adjustable aperture

The performance of all-optical (AO) logic AND and OR gates, which are realized for the first time using reflective semiconductor optical amplifiers (RSOAs) as nonlinear elements, is theoretically investigated at 120 Gb / s. The switching modules that incorporate the RSOAs and exploit their potential for AO signal processing are the Mach–Zehnder interferometer and the delayed interferometer for the

A kind of bending-insensitive multicore fiber (MCF) is proposed. The core adopts a low-mode gradient index structure to form a seven-core few-mode fiber. The finite element method is used to simulate and analyze the bending loss of the central core and the outer core, the crosstalk between the core modes, and the influence of core parameters on the crosstalk performance. Data simulation results show

We present broadband supercontinuum generation in dispersion engineered tellurite clad As2S3 core photonic crystal fiber. Finite element method (FEM) is adopted for different numerical analysis of the fiber. The design is so engineered that zero dispersion is obtained at 1550-nm wavelength. Very high nonlinearity is achieved in the proposed structure as 5.5 × 104 W − 1 km − 1. For a 20 fs input pulse

High-power and high-quality pulsed fiber lasers with low repetition frequency are widely applied to various fields ranging from basic science to industrial applications. Coherent beam combining (CBC) is a significant method to obtain that beam, but few methods used for large-scale CBC of pulsed fiber lasers with low repetition frequency were presented. To realize it, a new method based on a continuous

A metamaterial- and graphene-based broadband terahertz (THz) electromagnetic wave absorber that is composed of a stack of patterned gold film layer, patterned graphene layer, polyimide layer, and silicon layers was studied in detail. Our study is based on numerical simulations and electromagnetic absorption level higher than 90% over 2.09 THz band was demonstrated. The absorption frequency band significantly

Modulation transfer function (MTF) evaluation in the imaging of the optical lenses with poorly corrected geometric distortion involves sampling region of interest (ROI) images that are affected by geometric distortion, reducing its accuracy. A based liquid-crystal-device MTF (LMTF) method is proposed for this purpose by evaluating MTF of the medical rigid endoscope. This method establishes a mathematical

We present a full-scale numerical study of thermally induced optical aberrations on the primary mirror of a beam director telescope. In particular, we investigate high-power laser-induced deformations, resulting monochromatic aberrations, and their effects on imaging and laser focusing performance of primary telescope mirrors in shared aperture beam director systems. As a practical example, we consider

The present work introduces the concept of a total-internal-reflection (TIR)-based optical rotation, quasi-phase-matching (QPM) technique for generating highly efficient second-harmonic optical output in a rectangular slab of magnesium oxide-doped lithium niobate crystal coated with a thin layer of yttrium oxide. Combinational effects of TIR optical rotation QPM and fractional QPM techniques are experienced

A scheme called clipping-piecewise linear companding (C-PLC) was proposed in this paper to address the problem of high clipping noise and peak-to-average power ratio (PAPR) in optical orthogonal frequency division multiplexing (O-OFDM) signal for visible light communication (VLC) systems. The clipping information of the signal could be retained by adding a suffix at its end, which could reduce the

Intensity modulation of broadband optical signals transmitted through large-core fiber-optic cables often resorts to opto-mechanical choppers, usually in the form of bulky rotating wheels. We demonstrate an alternative fiber-optic intensity modulator with a compact footprint of 55.6 × 12.8 × 4.6 mm3 that can be integrated in-line in an optical system. The design comprises two optical fiber cantilevers

We investigate the physical-layer security performance for a wireless-powered relaying mixed free-space optical-radio frequency (FSO-RF) system. In this system, a source transmits optical information to a relay (R), which decodes the received signal with a decode-and-forward protocol, converts it into an RF signal, and forwards it to a destination in the presence of an eavesdropper. Furthermore, we

A reliable, high-energy, and efficient 2 μm laser is a key component in the development of a coherent Doppler wind detection lidar. A theoretical and experimental analysis of (Tm, Ho) co-doped laser amplifiers is presented. Considering the influence of energy transfer, upconversion, and ground-state depletion, the amplified pulse energy as a function of input pulse energy can be predicted at different

Terahertz radiation for inspection and fault detection has been of interest for the semiconductor industry since the first generation and detection of THz signals. Until recent hardware advances, THz systems lacked the signal quality and reliability for use as an effective nondestructive testing (NDT) method. Incremental advances in THz sources, detectors, and signal processing resulted in the successful

The application of a light-field camera based on an overlapped square aperture micro-lens array (MLA) is reported. The location and direction of the incident light rays are recorded and reconstructed with a large depth of field by this imaging system. The optimized square MLA for light-field imaging, which increases the fill factor and utilization efficiency of the image sensor, is proposed. The array

We examine the chromatic properties of ghost images appearing in expanded viewing angle polarization-type head-up display systems. We propose an achromatic polarization correction method to suppress ghost images in the whole visible spectral range. The method is based on the use of two half-wave plates of orthogonal optical axis–one being laminated on the combiner, the other attached to the head-up

A planar lightwave circuit-based multi-channel arrayed waveguide grating (AWG) is used as a critical part of the fiber Bragg grating (FBG) interrogation unit and designed to be integrated into the fiber grating sensing system. We designed and fabricated a high-performance, 40 channels AWG in the device, enabling whole C-band wavelength demodulation while maintaining high-measurement resolution. The

Editor-in-Chief Adam Wax looks forward to resuming in-person conferences.

Diffractive lenses are optical elements commonly used in many applications owing to their simple and compact design. A multifocal diffractive lens enables the simultaneous focusing of an incident laser beam on several positions along the optical axis. The distances between the focal points and the energy densities in the foci can be changed by varying grating parameters, i.e., the modulation depth

Off-axis three-mirror anastigmat (TMA) telescopes provide excellent correction of aberrations over a large field-of-view in one direction. In a push broom configuration, this lightweight and compact optical configuration enables high-performing imaging. Moreover, passive multi-spectral acquisition can be achieved using a filter stack positioned at the detector vicinity. Stray light is a typical limiting

A stable S-band single longitudinal mode (SLM) erbium-doped fiber laser (EDFL) with narrow linewidth based on passive multiple-subring resonator (PMSR) has been proposed and experimentally verified. The designed structure of PMSR can effectively expand the equivalent free spectral range and eliminate dense longitudinal modes. In addition, the dual-coupled fiber ring contained therein can form a narrow-band

Our study describes effective techniques to transfer heat away from UV emitters based on dielectric barrier discharge excilamps. It presents findings from an investigation into the efficiency of excilamp radiation when cooled by air, inert gas, and liquid refrigerants. The devised cooling techniques were used to create radiation sources with a UV power density of up to 117 mW / cm2.

We propose a scheme of optical frequency comb (OFC) generation based on cascaded Mach–Zehnder modulator (MZM) and electroabsorption modulator (EAM) with Gaussian-shaped pulse signal. In the proposed scheme, the MZM and the nonzero-chirp EAM are driven by a periodic Gaussian-shaped pulse signal that is controlled with binary sequences, and then an OFC is output from EAM. The theoretical model of the

We propose and numerically design a magnetically tuned orbital angular momentum (OAM) generator operating in the terahertz (THz) regime based on air-clad microstructured optical fibers (ACMOFs) infiltrated with functionalized liquid crystals (LCs). The ACMOFs consist of a ring-like air hole layer uniformly arranged the outer surface, serving as both the whispering gallery mode (WGM) microcavity and

Continuous depth maps are reconstructed based on depth estimation from light-field data of axially distributed image sensing (ADS). In the proposed method, the light field of ADS is introduced, and the light-field trajectory function is presented, which formulates the relationship between image point positions in different axially captured images and the depth of object point. The depth value of an

Fringe projection technology is often used for three-dimensional (3D) measurement, but it is difficult to measure highlight surfaces. Polarization systems are usually used to remove highlight surfaces. Polarizing filters can be used to eliminate the highlights of the image, but they may also cause the image to be too dark and affect the measurement accuracy. Otherwise, to ensure measurement accuracy

We propose and demonstrate experimentally multimode Q-switched mode-locking (QML) fiber laser signal generation based on a long few-mode Er-doped fiber (FM-EDF). The erbium-doped profile of the fiber has been optimized to equalize the modal gain. The fiber supporting six modes has a total length of 5.5 m, a part of the fiber is used as a gain medium, and the unpumped part of the fiber is used as a

The performance analysis on phase change material germanium-antimony-tellurium-Ge2Sb2Te5 (GST)-assisted silicon waveguide-based non-volatile 1 × 2 and 2 × 2 switches are proposed. The designed structure contains a hybrid silicon waveguide and a regular silicon waveguide. By perfectly choosing the design considerations of the proposed switches, the power of transverse electric mode is coupled and shifted

A point-to-point optical link is usually based on a laser beam, where the most common propagation model is the Gaussian beam type. Due to its directional characteristics, minor alignment errors can cause considerable attenuation. The calculation of the misalignment losses involves solving an integral of a Gaussian beam translated over a receiver’s effective surface, leading to a more accurate link

The exotic properties of topological photonic crystals (PCs) have a series of application prospects in the field of optical communication. We present a Y-shaped beam splitter based on topologically protected waveguide, which consists of the topologically trivial PCs with line defect. The investigation results indicate it has the merits of unidirectional propagation, robustness, and excellent transmission

A laser diode illuminator for single-photon avalanche diode detection-based pulsed time-of-flight 3D range imaging is presented. The illuminator supports a block-based illumination scheme and consists of a 16-element custom-designed common anode quantum-well laser diode bar working in the enhanced gain switching regime and lasing at ∼810 nm. The laser diode elements are separately addressable and driven

We propose a three-dimensional (3D) multimodal medical imaging system that combines freehand ultrasound and structured light 3D reconstruction in a single coordinate system without requiring registration. To the best of our knowledge, these techniques have not been combined as a multimodal imaging technique. The system complements the internal 3D information acquired with ultrasound with the external

The advantages of optical time-domain reflectometer (OTDR) using spread spectrum technology are analyzed briefly. For the shortcomings of spread spectrum OTDR in traditional despreading method, the concept of optical domain multiplier is first proposed, i.e., the most important multiplication operation in despreading is realized by modulating the phase of Mach–Zehnder modulator before photoelectric

A simple nematic liquid crystal-filled dual-core photonic crystal fiber polarization beam splitter is designed and analyzed by the full-vector finite element method. The length of the polarization beam splitter is 13.3390 μm and the maximum extinction ratio (ER) is 143.49 dB. The bandwidth of ERs greater than 10 dB is 200 nm at a wavelength of 1.55 μm. This simple and easy-to-manufacture structure

Using polarization fields, light interference figures and isogyres of some uniaxial and biaxial birefringent optical elements are modeled. The effects of diattenuation, and linear and circular birefringence are included, and the Airy spiral is displayed for various cases. The two branches of the Airy spiral are shown to separate and surround separately the melatopes in the case of biaxial elements

Fe:ZnSe and other transition metals have broad upper and lower energy manifolds that give rise to broad absorption and fluorescence bands in the mid-infrared spectral region. Energy transfer between Fe2 + ions via re-absorption of fluorescence (due to the spectral overlap of these bands) and phonon-assisted energy transfer (due to the lattice dynamics of ZnSe) becomes more probable with increasing

Highly responsive, flexible aluminum nitride single nanowire ultraviolet photodetector (AlNNW-UVPD) is reported for the first time with the highest responsivity of 1197.5 mA / W along with an excellent external quantum efficiency of 584% under 254-nm UV light exposure at 30 V bias. A flexible nanoscale photodetector on a very small scale was fabricated through a scalable and highly cost-efficient hot-contact

We report a temperature measurement method based on fixed wavelength transmission intensity of long-period fiber grating. Relative to wavelength or edge filtering, this method has obvious advantages in measurement accuracy and cost. The relationship between the transmission intensity and temperature at a fixed wavelength is simulated based on the theory of long-period fiber grating coupling mode. The

Many applications require colored surfaces while maximizing photons to pass through with no optical losses. As the perceived color depends on the spectral content and the number of reflected photons for each wavelength, it is necessary to consider not only the chromatic content but also the brightness. As a first application example, photovoltaic modules could see their acceptance in urban situations

Pulsed laser ablation of pyrolytic graphite with a 4-J / cm2 KrF laser in backgrounds of air, argon, nitrogen, and helium at pressures up to 10 Torr was performed to study the plume dynamics. Optical emission imaging with a 2-ns gated intensified charged-coupled device camera was used to determine shock front positions and plume trajectories for characterization by free expansion, Sedov–Taylor (ST)

Visible light positioning (VLP) has been widely studied since it can provide high accuracy indoor positioning functionality with light-emitting diode (LED) beacons. However, existing VLP systems still suffer from high positioning latency and low robustness in practical scenarios. A robust and low-complexity image processing algorithm is proposed for LED region-of-interest (ROI) extraction and tracking

Due to high data rates, license-free spectrum, and immunity to electromagnetic interference, free-space optical (FSO) links are being considered as a potential candidate to meet the ever-increasing traffic demands of users. The FSO links remain less explored, as their performance depends on environmental conditions such as dust, fog, and clouds. Such conditions do not affect the radio frequency (RF)

Antireflection coatings (ARCs) on an optical substrate appear to be highly effective for reducing reflectance for optical and photovoltaic (PV) panel applications. In this perspective, we have prepared and investigated the performance of silica nanoparticles (SNPs) ARC through a sol–gel process for the PV module applications. The ∼160-nm-thick sol–gel prepared SNPs have been coated on a glass substrate

A full theoretical analysis of the performance of passive inline Sagnac interferometric optical current sensor with component errors has been completed. A mathematical model was developed to show how nonideal components affect the overall performance of the sensor. The Faraday rotator element is a critical component in this passively biased optical current sensor. The analysis indicates that errors

Long-range horizontal path imaging through atmospheric turbulence is hampered by spatiotemporally randomly varying shifting and blurring of scene points in recorded imagery. Although existing software-based mitigation strategies can produce sharp and stable imagery of static scenes, it remains highly challenging to mitigate turbulence in scenes with moving objects such that they remain visible as moving

Waveform decomposition techniques are commonly used to extract attributes of targets from light detection and ranging (LiDAR) waveforms. The conventional Gaussian decomposition (GD) cannot deal with system waveforms (SWs) with non-Gaussian shapes, whereas the recently proposed B-spline-based decomposition method holds an assumption of similarity transformation. We present a multi-Gaussian decomposition

A laser power scale transfer technique was developed based on shape detection; using this technique, detectors can be precisely centered on laser beams, thereby significantly reducing measurement errors introduced by detector nonuniformities and misalignments. A modified imaging scheme was designed and embedded in the scale transfer setup, and the effective resolution was proven to be better than 100

Camera calibration is crucial for geometric vision-based three-dimensional (3D) deformation measurement tasks. Among existing calibration techniques, the one based on planar targets has attracted much attention in the community due to its flexibility and reliability. Our study proposes a calibration technique to obtain high-accuracy internal and external parameters based on low-cost ordinary planar