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Gratings are widely used for coupling into and out of evanescent and propagating electromagnetic modes, which are otherwise not accessible due to their large in-plane wave vector. A precise description of the optical response requires the knowledge of the grating geometry. Here, we present an investigation of the optical properties of dielectric gratings of sub-micron periodicity fabricated on a multilayer structure, which supports Bloch surface waves, by means of spectroscopic ellipsometry. Taking into account non-idealities, such as the finite spectral bandwidth, in the modeling process is shown to be a necessity for an accurate description of the observed spectra. The grating geometry determined from the analysis of ellipsometry data agrees very well with atomic force microscopy scans. Thus, our ellipsometric model is corroborated. [ABSTRACT FROM AUTHOR]

This tutorial min review discusses the important features of nanotechnology of colour generation by the quantum dots (QDs), nanostructured photonic crystals (PCs) and plasmonic metal nanoparticles. Quantum dots (QDs) are characterized by the tunable and size dependent strong fluorescence emission properties. Photonic crystals (PCs) generate the material independent structural colour ( iridescent colour dependent on the angle of observation ) due to the constructive interference arising from Bragg diffraction by the nanostructured photonic crystals (PCs) producing the diffraction gratings. It causes the vibrant colour in the opals and pearls, wings of peacocks and butterflies, in the necks of pigeons, variable colours in chameleons, etc. Plasmonic nanoparticles like Au-, Ag- and Cu-nanoparticles show the both light absorption and scattering properties that can be tuned by varying the size, morphology and composition of the nanoparticles. Structural colour ( iridescent colour ) by PCs is used by nature while colouring by QDs and plasmonic nanoparticles are due to the man made activities. The nanotechnology based colour is superior to the organic pigment based colour in terms of brightness and photostability and this field is an emerging area of research with a great promise in terms of applications in various fields. [ABSTRACT FROM AUTHOR]

Spatial heterodyne spectroscopy (SHS) based on prism dispersion is a novel technique designed to overcome the limitations of traditional grating-based SHS, which is affected by grating diffraction. However, there are still some challenges with this technique, one of which is that the fringe localization plane (FLP) moves with changes in wavelength. This paper proposes a prism-based tunable SHS where the FLP is fixed, utilizing prism–bimirror–mirror structures. The theoretical spectral resolving power, based on an example, is higher than 1300 in the spectral range from 10,000 cm−1 to 25,641 cm−1 and is approximately 27,595 at 25,641 cm−1. Furthermore, we propose solutions to simplify the motion control system and address the problem of spectral aliasing. [ABSTRACT FROM AUTHOR]

We describe a testbed to characterize the optical response of compact superconducting on-chip spectrometers in development for the EXperiment for Cryogenic Large-Aperture Intensity Mapping (EXCLAIM) mission. EXCLAIM is a balloon-borne far-infrared experiment to probe the CO and CII emission lines in galaxies from redshift 3.5 to the present. The spectrometer, called µ-Spec, comprises a diffraction grating on a silicon chip coupled to kinetic inductance detectors (KIDs) read out via a single microwave feedline. We use a prototype spectrometer for EXCLAIM to demonstrate our ability to characterize the spectrometer's spectral response using a photomixer source. We utilize an on-chip reference detector to remove the spectral structure introduced by the off-chip optics and a silicon etalon to calibrate the absolute frequency. [ABSTRACT FROM AUTHOR]

Based on additive manufacturing via photopolymerization, this study combines polymer-dispersed liquid crystal (PDLC) technology with 3D printing technology to produce tunable micro-optical components with switchable diffraction or focusing characteristics. The diffraction grating and Fresnel zone plate are the research targets. Their structures are designed and simulated to achieve expected optical functions. A liquid crystal display (LCD) 3D printer is used to produce structures on transparent conductive substrates. The printed structures are filled with PDLCs and covered with transparent conductive substrates to achieve tunable functions. The proposed configurations are implemented and verified. The experimental results show that the diffraction efficiency of the 0th order increases from 15% to 50% for the diffraction grating and the focusing spot intensity decreases from 74% to 12% after the application of an electric field. These results demonstrate the feasibility of the proposed tunable optical component configurations. [ABSTRACT FROM AUTHOR]

In this work, we studied the photoinduced polarimetric and optical properties of the photosensitive carbazole-based azopolymer prepared in the form of thin films. Poly-N-(2,3-epoxypropyl)carbazole was used as a polymer matrix, which was copolymerized with the commercially available azo dye Solvent Yellow 3. Thin films of µm thicknesses were obtained by home-made rod-coating techniques. Polarization holographic recording was applied for direct diffraction gratings patterning. The polarization states of the recording beams were P–P, S–S, ±45° and left-right circular. The optical path of the probe beam passing through investigating media is defined by the summary changes in surface topography and volume anisotropy. The periodically modulated polarization/amplitude interference patterns produced by the gratings were investigated by in situ measurements of the diffraction efficiency (DE) kinetics in the first diffraction order at the DE saturation value. The surface relief was measured by AFM. A comparison of the behavior of azopolymer films during the recording of diffraction gratings with different polarization configurations of recording beams was carried out. The presented results confirm the possibility of recording not only the amplitude and phase of light, as in scalar holography, but also the polarization states of interfering beams. The angular dependences of the probe beam azimuth and ellipticity were analyzed, and some peculiarities of azopolymer photoinduced changes are discussed. [ABSTRACT FROM AUTHOR]

Micro and nanopatterned surfaces hold potential for various applications, such as wettability control, antibiofouling, and optical components. However, conventional patterning processes are characterized by complexity, high costs, and environmental burdens because of the use of resists. Therefore, this paper proposes facile and ultrafast electrochemical imprinting employing a polymer electrolyte membrane (PEM) stamp for achieving micro and nanoscale patterning on Si surfaces. The solid‐state electrochemical process efficiently generates oxide and hydrated oxide (Si–OH) patterns within several seconds at room temperature in a dry ambient environment. The formed oxide pattern can be employed as an etching mask to prepare diffraction gratings with diverse high‐resolution (≈100 nm) patterns utilizing the dry PEM stamp. The resulting oxide pattern on the Si surface exhibits instantaneous structural coloration upon exposure to humid air, attributable to the formation of a water microdroplet array on the oxide pattern. The oxide pattern is successfully applied for dynamic diffraction grating and letter encryption. The proposed solid‐state electrochemical oxidation scheme based on a PEM stamp, which eliminates the need for liquid electrolyte and resist, represents a simple and ultrafast process with a time cost of a few seconds, characterized by low processing costs and environmental impact. [ABSTRACT FROM AUTHOR]

Domain randomness is inherent in the fabrication of periodically poled lithium niobate (PPLN). The main cause of such domain randomness in fabrication of PPLN is due to electric poling process. This domain randomness not only impacts the effectiveness of frequency conversion, but also enhances the effectiveness of nonphase matched parasitic processes, which in many cases limits the performance of the device. In this paper, we experimentally demonstrate a nondestructive characterization of domain randomness in PPLN by diffraction-noise pattern with uniform illumination. We measure the domain randomness of PPLN and provide an effective method for poling quality assessment either as good or poor quality of PPLN through this paper. [ABSTRACT FROM AUTHOR]

The photorefractive effect is a phenomenon in which the refractive index changes at the interference fringe, forming a diffraction grating (hologram). Photorefractive materials are composed of a combination of electro-optical materials and photoconductive compounds. Liquid crystals mixed with a photoconductive compound are useful as photorefractive materials because of their large birefringence and fluidity. Various applications are expected, such as amplifying optical signals, dynamic holograms, and Fourier optical elements. This article describes the development of high-performance photorefractive materials using liquid crystals and their applications in laser ultrasonics. [ABSTRACT FROM AUTHOR]

An objective soft x-ray flat-field spectrograph employing a laminar-type bilayer coated, varied-line-spacing, spherical grating was designed to improve the detection limit and sensitivity of soft x-ray flat-field spectrographs in a region of 250–550 eV. As a design criterion, spectral flux, SF, [Hatano et al., Appl. Opt. 60, 4993–4999 (2021)], which is proportional to the amount of optical flux incident onto a detector and correlated with detection sensitivity, was used to be maximized. To enhance reflectivity with the coating design, Au/Ni bilayer coating was investigated to optimize the incidence angle and thickness of the Ni layer. This is based on the consideration that, in an energy region of over 400 eV, refractive indices of Au (bottom layer), Ni (top layer), and vacuum are increased from the bottom to the top of the layers, and a supplemental enhancement of reflectivity can be expected by optimizing the thickness of the top layer. Thus, the thickness of Ni and the incidence angle were chosen to be 8.0 nm and 86.00°, respectively. To maintain dispersion and spectral resolution of the grating used at an incidence angle of 87.07° as previously designed, groove density was increased to 1500 lines/mm from 1200 lines/mm of our previous design. Finally, a holographic, varied-line-spacing, spherical grating was designed assuming an aspherical-wavefront-recording configuration. The numerical simulation results showed that the spectrograph employing newly designed grating with laminar-type grooves and Au/Ni bilayer coating exhibited 2–18 times higher spectral flux as well as an improved spectral resolution compared with those obtained with the previously designed gratings and spectrographs. [ABSTRACT FROM AUTHOR]

In order to solve the problem of narrow band coverage of traditional infrared gratings, a new type of diffraction grating is invented and named as angle-gradient echelle grating. The blaze angle of the grating gradually changes along the direction of the grating grooves, which can be regarded as etching countless sub-gratings with different blaze angles on a grating, breaking the limitation of the number of blaze angles of traditional gratings. In addition, in order to solve the processing problem of angle-gradient echelle grating, a new processing method, shaped vibration cutting (SVC) with a time-varying trajectory is developed. By exploring the influence of different processing parameters on the grating processing results, a suitable processing plan was proposed. Eventually, angle-gradient echelle grating with blaze angles varying from 30° to 55° and surface roughness of as low as 20 nm was fabricated on metallic glass, a material that is difficult to machine. • A blazed grating with a gradient blaze angle is proposed. • The proposed grating has high diffraction efficiency in the infrared band. • A variable vibration trajectory processing method is proposed. • The feasibility of the processing method is verified on an aluminum substrate. • This method can achieve high-quality structural processing on metallic glass. [ABSTRACT FROM AUTHOR]

Submicrometer double-grooved gratings feature unique optical properties and diverse potential applications, most of which have been fabricated by electron beam lithography up till now. On the other hand, holographic lithography based on a phase mask [near-field holography (NFH)] has the advantages of high throughput, low cost, and a compact setup in terms of a short optical path. Distinguished from conventional NFH based on double-beam interference, multibeam NFH based on multibeam interference is studied to form groove profiles of double-grooved gratings in this study. The formation principle of double-grooved gratings is attributed to the multibeam interference of the transmitted beams behind the phase mask. Within such multibeam interference, every two of diffracted beams interfere and form several sets of latent subgrating patterns. The formation of double-grooved gratings can be understood as the superimposition of different portions of subgrating patterns. We also demonstrated the potential and challenges of several key factors in tailoring the symmetric and asymmetric double-grooved structures, including the incidence angles, the efficiency distribution of phase masks, exposure-development conditions, and the spacing between the mask and substrate. Symmetric and asymmetric double-grooved gratings with periods of 666.7, 950, and 1000 nm were fabricated by coplanar three-beam NFH at normal incidence, and coplanar four-beam NFH at oblique incidence and near normal incidence. The experimental results of the evolution of the grating profiles of double-grooved gratings are in relatively good agreement with the simulation. This study provides an alternative cost-effective fabrication method for the mass production of double-grooved gratings. Moreover, this study also enriches the diversity of groove profiles of diffraction grating by NFH. [ABSTRACT FROM AUTHOR]

Optics has advanced through centuries of research into the fundamental properties of light and its interactions with matter. Within this rich history, one optical component stands out: the diffraction grating. Liquid crystals (LCs) have emerged as promising candidates in diffraction gratings. LCs are versatile and adaptable materials influenced by various external factors. Diffractive LC grating devices can be produced through methods such as photo alignment, using polymer walls, or employing patterned electrodes. However, photo alignment poses challenges in terms of manufacturing complexity, and using polymer walls is associated with some drawbacks, such as high driving voltage and slower response times, which must be considered in their application. Currently, research efforts are predominantly focused on manufacturing techniques involving patterned electrodes. In this review, we comprehensively explored the theoretical foundations underpinning diffraction gratings. Additionally, we summarized research on diffractive gratings based on LC using patterned electrodes and conducted a comparative analysis of the characteristics of each device. [ABSTRACT FROM AUTHOR]

Carbon‐based fiber materials are widely used in aerospace, military, and electronics owing to their outstanding comprehensive properties. However, the high degree of crystallization and chemical inertness of their surfaces impede the coloring of such materials by traditional dyeing methods, thereby limiting their application in a broader field. Exploring advanced micro/nano‐processing technology for colored carbon‐based fiber materials has become a growing interdisciplinary research area in recent years. Therefore, this review comprehensively discusses the structure‒color‒function relationships of carbon‐based fiber materials. The structure of carbon‐based fiber materials and their properties responsible for challenges in coloring by traditional dyeing methods are discussed. Moreover, the color‐generating mechanisms underlying the display of structural colors by living organisms due to fundamental optical phenomena, including thin/multilayer‐film interference, diffraction grating, scattering, and photonic crystals, are described. Furthermore, recent progress in bio‐inspirated colored carbon‐based fiber materials prepared via advanced micro/nanoscale manufacturing strategies is reviewed. In addition, emerging applications of colored carbon‐based fiber materials in various fields are presented. Finally, the possible challenges and future directions for the design, large‐scale production, and application of colored carbon‐based fiber materials and their composites are discussed, aiming to promote the material design of innovative next‐generation systems and research in the advanced material and related engineering fields. [ABSTRACT FROM AUTHOR]

The diffraction efficiency of blaze gratings is optimized only at a specific frequency due to a fixed blaze angle, resulting in reduced and variable diffraction efficiencies over the working frequency band. Additionally, blazed gratings demonstrate polarization dependence due to their groove structures and the interaction of light with their surfaces. Consequently, designing gratings with constant diffraction efficiencies across a wide frequency bandwidth while maintaining polarization independence remains a challenge. Here, a design paradigm of dispersion engineerable meta‐grating inspired by orthogonal harmonic oscillations (OHO) is presented. Utilizing the OHO model, the phase dispersion of a metasurface can be precisely controlled, which applies to any unit cell featuring two orthogonal electromagnetic resonances. As a proof of concept, a polarization‐insensitive meta‐grating is showcased, where the blazed angle adapts with the incident frequency, ensuring broadband performance. In the experiment, the adaptively‐blazed grating measured an optimized and constant diffraction efficiency of ≈80% over the working wavelength range, i.e., 8.7–12.2 µm. The difference in diffraction efficiency between the two perpendicular linear polarization states remains within 4.6%. The proposed paradigm paves the way for meta‐device design based on precise dispersion engineering, which has potential applications in spectrometers, broadband beam forming and steering, hyperspectral imaging, etc. [ABSTRACT FROM AUTHOR]

X-ray grating interferometry allows for the simultaneous acquisition of attenuation, differential-phase contrast, and dark-field images, resulting from X-ray attenuation, refraction, and small-angle scattering, respectively. The modulated phase grating (MPG) interferometer is a recently developed grating interferometry system capable of generating a directly resolvable interference pattern using a relatively large period grating envelope function that is sampled at a pitch that is small enough that X-ray spatial coherence can be achieved by using a microfocus X-ray source or G0 grating. We present the theory of the MPG interferometry system for a 2-dimensional staggered grating, derived using Fourier optics, and we compare the theoretical predictions with experiments we have performed with a microfocus X-ray system at Pennington Biomedical Research Center, LSU. The theoretical and experimental fringe visibility is evaluated as a function of grating-to-detector distance. Additionally, quantitative experiments are performed with porous carbon and alumina compounds, and the mean normalized dark-field signal is compared with independent porosimetry measurements. Qualitative analysis of attenuation and dark-field images of a dried anchovy are shown. [ABSTRACT FROM AUTHOR]

The efficiency of drilling and cutting of metals by laser radiation under the influence of two lasers, during processing in water and drilling of small holes in ceramics and metal with a high aspect ratio has been determined. The conditions for clearing the channel of laser radiation propagation through the flame of burning hydrocarbons, as well as high-quality welding of two identical tapes made of polymer composite materials for several types of tapes have been found. Diamond coatings on a cutting tool made of VK8 hard alloy in the plasma of a laser plasmatron have been obtained, and diagnostics of the plasma and coatings has been carried out. A two-wave pyrometer based on a spectrometer with a diffraction grating for measuring the temperature of a heated surface has been developed. [ABSTRACT FROM AUTHOR]

Using Dammann grating (DG) metasurfaces enables miniaturization and integration of devices for generating structured light, allowing them to be used in different applications with different types or working wavelengths of structured light. However, most existing DG metasurfaces are based on Hermitian photon systems, and there has been no exploration of the results of DG metasurfaces under non-Hermitian photon system conditions. In this study, we numerically constructed a non-Hermitian DG metasurface with parity-time (PT) symmetry of the adjacent silicon dioxide substrate and lithium niobate (LiNbO3, LN) nanorods. Simulation results have demonstrated that introducing PT symmetry into DG metasurfaces alters their response wavelengths, leading to changes in the structured light patterns. To further investigate the effects introduced by incorporating PT symmetry into diffraction gratings, we have also designed two types of pseudo-Dammann gratings (PDG), namely, annular PDG and cross-shaped PDG. Incorporating PT symmetry into PDG not only improved the uniformity of the diffracted light spot arrays but also altered the distribution arrangement of the spots in one type of PDG, enabling the generation of novel and unique structured light patterns in the far field. This study theoretically proposed a PT-symmetric and dynamically tunable metasurface structure, providing a new approach for the design, control, and fabrication of dynamically adjustable optical components. [ABSTRACT FROM AUTHOR]

Phase gradient metagratings (PGMs) reshape the impinging wavefront though the interplay between the linear adjacent phase increment inside supercells and the grating diffraction of supercells. However, the adjacent phase increment is elaborately designed by tuning the resonance of each subcell at a certain target frequency, which inevitably confines PGMs to operate only at the single frequency in turn. We notice that there exists a freedom of phase choice with a multi-2π increment in a supercell of PGMs, whereas conventional designs focus on the 2π increment. This freedom can induce a collaborative mechanism of surface impedance matching and multi-wavelength subcells, enabling the design of PGMs at multi-wavelengths. We further design and fabricate a supercell consisting of eight curved pipes to construct the two-wavelengths PGMs. The linear adjacent phase gradient of 0.25π at the fundamental frequency 3430 Hz is achieved, while the almost perfect transmission effect is observed due to the impedance match at the ends of curved pipes. In addition, the transmission field at the double frequency 6860 Hz is measured, whose refraction direction is consistent with that at 3430 Hz. This design strategy originated from phase choice freedom in the supercell and the experimental fabrication might stimulate applications on other multi-wavelength metasurfaces/metagratings. [ABSTRACT FROM AUTHOR]

The article discusses the use of CMOS sensor chips from discarded cameras or smartphones as teaching tools for demonstrating diffraction. The authors conducted diffraction experiments using electronic components and fluorescent dyes to visualize diffracted light paths. They also created transmission gratings using CMOS sensors as templates and observed diffraction patterns. The study aimed to provide low-cost demonstrations of physics concepts, particularly related to diffraction. The research was conducted by Lian Hu and Yi-Xiang Wang from Jiangnan University in China, who are interested in developing innovative physics demonstrations. [Extracted from the article]

2D diffraction gratings based on Gauss lattices are a class of nonperiodic lattice in which the sites are located at Rj1,j2=j1ndx̂+j2ndŷ${\bf R}_{j_1,j_2}=j_1^nd\hat{\bf x} + j_2^nd\hat{\bf y}$ with j1,j2∈{...,−1,0,1,...}$j_1,j_2\!\in \! \lbrace \ldots, -1,0,1,\ldots \rbrace$, n∈{2,3,4,...}$n\! \in \! \lbrace 2,3,4, \ldots \rbrace$, dx̂$d\hat{\bf x}$ and dŷ$d\hat{\bf y}$ orthogonal primitive vectors in the plane, and d$d$ the lattice constant. Gauss lattices are treated for various orders n$n$, and discuss applications for gratings separable in the x$x$ and y$y$ directions. These gratings, while geometrically very simple, produce complex pseudorandom diffraction patterns, though they exhibit rotational invariance and strong correlations along the x$x$ and y$y$ directions. Then how to generalize the approach is discussed to attain nonseparable gratings where such features are suppressed. The result is an intensity distribution like that of diffuse light, the effect originating in the breaking of the hidden translational invariance of the Gauss lattice. [ABSTRACT FROM AUTHOR]

We employed a double-layer coupled diffractive optical element, based on metasurfaces and diffraction gratings, which exhibits wavefront modulation and chromatic dispersion compensation. Utilizing this double-layer coupled diffractive optical element in the optical information transmission process of a diffractive waveguide allows for the transmission of color image information using a single-layer waveguide structure. Our results demonstrate that, under the conditions of a field of view of 47° × 47°, an entrance pupil size of 2.9 × 2.9 mm2, and an exit pupil extension size of 8.9 mm, the uniformity of the brightness for each monochromatic field reached 85%, while the uniformity of color transmission efficiency exceeded 95%. [ABSTRACT FROM AUTHOR]

Since surface relief transmission gratings have very strict requirements on operators and use environment, according to the semiconductor laser external cavity spectral beam combining system, this paper proposes a design scheme for a semiconductor laser array spectral beam combining system based on the grating-external cavity. The finite element approach was used to create a wideband, high-efficiency fill-in multilayer dielectric transmission grating structure for a high-power spectrum beam combining system. The incidence angle, ridge height, duty cycle, and sidewall inclination angle of the transmission grating were tuned and evaluated, and a link between the transmission grating's diffraction efficiency and grating characteristics was discovered. The calculated design of the high-power fused silica transmission grating has a negative first-order peak diffraction efficiency of 99.5% in the 800 nm range. In the spectral region of 765–872 nm, the transmission grating's diffraction effectiveness exceeds 92%. The filled ultra-high diffraction efficiency multilayer dielectric transmission grating design addresses the issue of resistance to high-power lasers under complicated operating settings. It is intended to maintain a high diffraction efficiency even after several cleaning cycles, and it is an ideal component for high-power spectrum beam combining systems. [ABSTRACT FROM AUTHOR]

Multifocus microscopy has previously been demonstrated to provide volumetric information from a single shot. However, the practical application of this method is challenging due to its weak optical sectioning and limited spatial resolution. Here, we report on the combination of a distorted diffraction grating and multifocal scanning illumination microscopy to improve spatial resolution and contrast. DG is introduced in the emission path of the multifocal scanning illumination microscopy, which splits the fluorescence signal from different sample layers into different diffraction orders. After postprocessing, super-resolution wide-field images of different sample layers can be reconstructed from single 2D scanning. [ABSTRACT FROM AUTHOR]

Prior magneto‐optical transmission models through ferrofluids are limited by oversimplifications which hinder accuracy and generalizability. To overcome this challenge, this study models the magnetic field effect on the magneto‐optical transmission through hematite ferrofluid using the method of invariant embedding. Optical coherence tomography (OCT) is used to extract the changes in the refractive index, enabling a discovery of a magnetodielectric effect for the hematite ferrofluid. To establish a basis for control and understanding, the influence of the magnetic field on the spatial transmission profile at different wavelengths, optical propagation lengths, and the effect of variation of each size parameter on the optical transmission have been investigated. Further parametric studies allowed finding out an analogy to nonuniform, cascade, volume holographic diffraction gratings, which is crucial for a wide range of optical and bioimaging applications. Compared to the experimental results, the presented model achieves 99% accuracy over the wavelength range (300–1100) nm under uniform static magnetic field (0–6.5) mT. Besides, the conspicuous lead of evidentiary understanding of magneto‐optical interactions with magnetic fluids, the structural milestones of the model can be further utilized to model similar challenging constructs in complex media. The innumerable applications of study extend to involve communication engineering, biomedical, optical, and security applications. [ABSTRACT FROM AUTHOR]

Quantum cascade lasers (QCLs) in the mid-infrared (MIR) hold significant potential for widespread applications in both military and civilian contexts. However, the utility of present single-chip QCLs is hampered by issues such as low output power and subpar beam quality. This study addresses these limitations by employing spectral beam combining (SBC) based on a diffraction grating, with an aim to enhance both power and beam quality of MIR QCLs. Coaxial power synthesis of three single-chip QCLs (around 4.75 μm) is achieved experimentally, importantly, the beam quality did not decrease after combining, essentially maintaining the same quality as before combining. It is proposed that there are four main factors affecting the combining efficiency, namely operating optical power (or driving current) of the chips, individual differences in QCL chips, diffraction grating, and reflectivity of feedback mirror, and their effects on the combining efficiency are discussed separately. This study confirms that SBC is an effective way to obtain high-power and high-beam quality MIR QCL sources, and lays a research foundation for more beam spectral combining. [ABSTRACT FROM AUTHOR]

The unique diffractive properties of gratings have made them essential in a wide range of applications, including spectral analysis, precision measurement, optical data storage, laser technology, and biomedical imaging. With advancements in micro- and nanotechnologies, the demand for more precise and efficient grating fabrication has increased. This review discusses the latest advancements in grating manufacturing techniques, particularly highlighting laser interference lithography, which excels in sub-beam generation through wavefront and amplitude division. Techniques such as Lloyd's mirror configurations produce stable interference fringe fields for grating patterning in a single exposure. Orthogonal and non-orthogonal, two-axis Lloyd's mirror interferometers have advanced the fabrication of two-dimensional gratings and large-area gratings, respectively, while laser interference combined with concave lenses enables the creation of concave gratings. Grating interferometry, utilizing optical interference principles, allows for highly precise measurements of minute displacements at the nanometer to sub-nanometer scale. This review also examines the application of grating interferometry in high-precision, absolute, and multi-degree-of-freedom measurement systems. Progress in grating fabrication has significantly advanced spectrometer technology, with integrated structures such as concave gratings, Fresnel gratings, and grating–microlens arrays driving the miniaturization of spectrometers and expanding their use in compact analytical instruments. [ABSTRACT FROM AUTHOR]

This study investigates the optical properties of diffraction gratings using localized surface plasmon resonance (LSPR) with metal nano-hemispheres. We fabricated metal nano-hemisphere gratings (MNHGS) with Ga, Ag, and Au and examined their wavelength-selective diffraction properties. Our findings show that these gratings exhibit peak diffraction efficiencies at 300 nm, 500 nm, and 570 nm, respectively, corresponding to the LSPR wavelengths of each metal. The MNHGs were created through thermal nanoimprint and metal deposition, followed by annealing. The experimental and simulation results confirmed that the MNHGs selectively diffract light at their resonance wavelengths. Applying these findings to third-order nonlinear laser spectroscopy (MPT-TG method) enhances measurement sensitivity by reducing background noise through the selective diffraction of pump light while transmitting probe light. This innovation promises a highly sensitive method for observing subtle optical phenomena, enhancing the capabilities of nonlinear laser spectroscopy. [ABSTRACT FROM AUTHOR]

Volume-phase holographic gratings are suitable for use in greenhouse gas detection imaging spectrometers, enabling the detection instruments to achieve high spectral resolution, high signal-to-noise ratios, and high operational efficiency. However, when utilized in the infrared wavelength band with high dispersion requirements, gratings struggle to meet the demands for low polarization sensitivity due to changes in diffraction performance caused by phase delays in the incidence of light waves with distinct polarization states, and current methods for designing bulk-phase holographic gratings require a large number of calculations that complicate the balance of diffraction properties. To overcome this problem, a design method for transmissive bulk-phase holographic gratings is proposed in this study. The proposed method combines two diffraction theories (namely, Kogelnik coupled-wave theory and rigorous coupled-wave theory) and establishes a parameter optimization sequence based on the influence of design parameters on diffraction characteristics. Kogelnik coupled-wave theory is employed to establish the initial Bragg angle range, ensuring that the diffraction efficiency and phase delay of the grating thickness curve meet the requirements for incident light waves in various polarization states. Utilizing rigorous coupled-wave theory, we optimize grating settings based on criteria such as a center wavelength diffraction efficiency greater than 95%, polarization sensitivity less than 10%, maximum bandwidth, and spectral diffraction efficiency exceeding 80%. The ideal grating parameters are ultimately determined, and the manufacturing tolerances for various grating parameters are analyzed. The design results show that the grating stripe frequency is 1067 lines per millimeter, and the diffraction efficiencies of TE and TM waves are 96% and 99.89%, respectively. The diffraction efficiency of unpolarized light is more than 88% over the whole spectral range with an average efficiency of 94.49%, an effective bandwidth of 32 nm, and a polarization sensitivity of less than 7%. These characteristics meet the performance requirements for dispersive elements based on greenhouse gas detection, the spectral resolution of the detection instrument is up to 0.1 nm, and the signal-to-noise ratio and working efficiency are improved by increasing the transmittance of the instrument. [ABSTRACT FROM AUTHOR]

Thee‐dimensional nano‐structuring of bulk fused silica glass remains a challenging issue due to limitations of traditional fabrication methods. In the present work the fabrication of hollow mm‐length channels is demonstrated in bulk fused silica by femtosecond laser irradiation followed by chemical etching, achieving feature sizes of 300 nm. The tight focusing and threshold energy conditions allow to reveal unexplored fabrication regimes. The robustness and repeatability of the process are demonstrated through the fabrication of fused silica diffraction gratings, made of parallel hollow channels with variable pitches even in the sub‐wavelength regime. [ABSTRACT FROM AUTHOR]

We report the results of laboratory studies of the main optical properties of the slitless spectrograph developed for a small telescope with a 0.5 m-diameter primary mirror and a focal ratio of . The spectrograph operates in the 450–950 nm wavelength interval and has a field of . Its distinctive feature is the use of a composite grism subdivided into two subapertures with independently optimized parameters. Measurements show that the use of such a grism makes it possible to achieve a spectral resolving power from 461 to 1041 with the grating diffraction efficiency as high as 45 . We demonstrate that our solution provides better optical characteristics compared to the classical grism and that our measurements agree well with the results of modeling. [ABSTRACT FROM AUTHOR]

In this work, the external magnetic field is employed as a "knob" to transfer the light energy from the zero-order diffraction to the high-order diffractions of electromagnetically induced grating in a degenerate two-level atomic medium. Under a standing-wave coupling field, the diffraction of the probe beam is created with the diffraction pattern including zero-, first- and second-order diffractions. When the magnetic field is not applied, the absorption grating is formed based on amplitude modulation of the transmission function; most of the probe light energy is focused on the zero-order diffraction (about 70%) and only about 6% of the first-order diffraction. However, when the external magnetic field is applied, the phase grating is formed based on the phase modulation of transmission function; the probe light energy is transferred from zero-order diffraction to first- and second-order diffractions, in which the first-order diffraction efficiency can be obtained about 32% with proper magnetic field strength. Moreover, the probe light energy can also be transferred from zero-order diffraction to first- and second-order diffractions by adjusting the frequency and/or the intensity of the coupling and probe fields in the presence of external magnetic field. [ABSTRACT FROM AUTHOR]

Unlike acoustic metasurfaces that rely solely on phase gradients, acoustic metagratings (AMs) operate based on both phase gradients and grating diffraction, thus further extending the generalized Snell's law (GSL). In particular, AMs can achieve reversal of refraction and reflection based on the parity of the number of wave propagations inside the AMs. So far, discussions of this GSL extension have largely been applied to one-dimensional periodic AMs, while the designs of two-dimensional (2D) periodic AMs and their performance in three-dimensional (3D) space have been quite limited. Here, we study the GSL extension in 3D space and experimentally demonstrate a series of functional 2D periodic AMs. The designed AMs can achieve sound refraction/reflection under any incidence angle in 3D space, without restrictions to certain critical ranges; adjusting incident angles only enables the reversal of refraction and reflection. Additionally, we demonstrate two types of dual-layer sound lenses based on two AMs, whose reversal of refraction and reflection can be realized by simply attaching or separating the two AMs. Our work paves the way to complex 3D wavefront manipulation of AMs, which may find potential use in practical acoustic devices. [ABSTRACT FROM AUTHOR]

Particle plasmon resonance (PPR), or localized surface plasmon resonance (LSPR), utilizes intrinsic resonance in metal nanoparticles for sensor fabrication. While diffraction grating waveguides monitor bioaffinity adsorption with out-of-plane illumination, integrating them with PPR for biomolecular detection schemes remains underexplored. This study introduces a label-free biosensing platform integrating PPR with a diffraction grating waveguide. Gold nanoparticles are immobilized on a glass slide in contact with a sample, while a UV-assisted embossed diffraction grating is positioned opposite. The setup utilizes diffraction in reflection to detect changes in the environment's refractive index, indicating biomolecular binding at the gold nanoparticle surface. The positional shift of the diffracted beam, measured with varying refractive indices of sucrose solutions, shows a sensitivity of 0.97 mm/RIU at 8 cm from a position-sensitive detector, highlighting enhanced sensitivity due to PPR–diffraction coupling near the gold nanoparticle surface. Furthermore, the sensor achieved a resolution of 3.1 × 10−4 refractive index unit and a detection limit of 4.4 pM for detection of anti-DNP. The sensitivity of the diffracted spot was confirmed using finite element method (FEM) simulations in COMSOL Multiphysics. This study presents a significant advancement in biosensing technology, offering practical solutions for sensitive, rapid, and label-free biomolecule detection. [ABSTRACT FROM AUTHOR]

The article presents methods for amplifying femtosecond laser pulses. A chirped-pulse amplification setup and a grating-based device are presented that can be used to amplify a chirped pulse with a total gain of up to 1011. A typical block diagram of a chirped-pulse amplifier for producing high-power femtosecond pulses is described. The use of an amplifying system consisting of a multipass amplifier and amplification stages with a progressive increase in the diameter of the laser beam makes it possible to increase the pulse energy by a factor of 108–109, avoiding damage to the amplifying elements. The method of amplifying chirped pulses requires the use of diffraction gratings with sizes close to 1 m to amplify pulses up to energies of tens of J. In particular, the use of giant laser systems based on amplifying cascades containing neodymium glass plates is noted. A parametric method for amplifying femtosecond pulses is considered. The advantages and disadvantages of parametric amplification are discussed. A general block diagram of an installation for obtaining petawatt-level femtosecond pulses by parametric amplification is presented. The principle of parametric amplification is used not only to obtain ultra-high powers and intensities, but also to achieve high values of other parameters. [ABSTRACT FROM AUTHOR]

The paper presents a model of an open resonator exhibiting a single high-Q eigen oscillation within a one-octave frequency band. The resonator is synthesized by integrating a diffraction radiation antenna, which comprises a segment of a dielectric waveguide above a metal substrate with a diffraction grating, into a system of flat reflectors aligned parallel to the wave fronts of surface and bulk waves generated by the antenna. A pulse response with an amplitude-frequency characteristic featuring one pronounced resonant maximum, which corresponds to an eigen oscillation with Q factor exceeding 104 , has been achieved in the proposed system. The optical length of the resonator exceeds the wavelength of the working oscillation by over 50 times. The feasibility of tuning the resonator via moving both the mirrors and the diffraction grating is demonstrated. The proposed model holds promise for applications in the development of solid-state and quantum radiation sources operating in the microwave and higher frequency ranges. [ABSTRACT FROM AUTHOR]

In this paper, a comparative analysis and numerical simulation of operation of two types of amplitude binary gratings (conventional and fork), both in the focal plane and near-field diffraction under illumination by mode beams with different polarization states, were performed. The simulation of the field formation in the focal plane was performed using the Richards–Wolf formalism. The diffraction calculation in the near-field diffraction was performed based on the FDTD method, considering the 3D structure of optical elements. The possibility of multiplying the incident beam in different diffraction orders of binary gratings and the polarization transformation associated with spin–orbit interaction at tight focusing were shown. In this case, various polarization transformations were formed in ±1 diffraction orders of the fork grating due to different signs of the introduced vortex-like phase singularity. The obtained results can be useful for the laser processing of materials and surface structuring. [ABSTRACT FROM AUTHOR]

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Due to the orbital angular momentum it carries, the vortex beam generated by forked gratings is an important way to investigate physics and probe matter. However, unwanted high-order diffractions inherently introduced by traditional fork gratings may be overlaid on useful first-order diffraction, leading to errors in subsequent decomposition of the spectrum. Here, we present a single optical element with a sinusoidal transfer function, termed as quasi-random-dots fork gratings, which can effectively suppress high-order diffractions. The biggest advantage of quasi-random-dots fork gratings is that it can achieve single-order diffraction with a planar structure that can only be achieved by sinusoidal fork gratings with a three-dimensional structure. Therefore, it is a much simpler process to fabricate. Both simulation and experimental results confirm that quasi-random-dots fork gratings can effectively eliminate diffractions of second order and higher orders, and only 0th and ±1st orders are retained. In addition, the helical phase structure of vortex beams with multiple topological charges is also demonstrated. This optical element has potential applications in the field of particle manipulation and imaging. [ABSTRACT FROM AUTHOR]

Diffractive optical elements (DOEs) enable precise control over the direction and filtering of light, making them common components in spectrometers, waveguides, and sensors. There is great interest in tunable and sub‐micron diffractive optical elements in flexible photonics and for responsive structural colors. Here this study presents sub‐micron tunable diffraction gratings produced by patterning a liquid crystal elastomer (LCE). The intrinsic anisotropic deswelling of the liquid crystal elastomer enables sub‐micron (707 nm) pitch structures to be produced from a micron‐scale (1040 nm) surface relief grating. Using atomic force microscopy (AFM) and diffraction measurements, a thermal pitch tunability is demonstrated of +212 nm (+31%) or −322 nm (−33%) over a temperature range of 215 °C depending on grating orientation. A mechanical pitch tunability is demonstrate of +1110 nm by applying strains of up to 157% to the liquid crystal elastomer. The height of the diffraction grating is preserved over strain due to the negative Poisson‐ratio, or "auxetic", behavior exhibited by this chosen family of the liquid crystal elastomers. This report opens the possibility of using LCEs to facilitate flexible sub‐micron diffractive optical elements, with a high degree of tunability for sensing and structural color applications. [ABSTRACT FROM AUTHOR]

AbstractFor a long time, the forming quality of large area diffraction gratings is restricted by the one-time coating quality and uniformity of large thickness and large area aluminum films. Large thickness coatings, low accuracy of large depth grooves and diamond tool wear problems were the main reasons for the failure of the test to inscribe large area diffraction gratings. Therefore, the use of layered coating process can effectively ensure the uniformity and consistency of large-area and large-thickness grating blanks coated with aluminum film, and improve the high precision of large depth diffraction grating slot type. In order to reveal the mechanism of the groove-forming process of multilayer aluminum films, the microstructure and mechanical properties of different aluminum films were observed. In this article, the removal behavior and mechanism of nanomechanically scratched multilayer aluminum film materials are investigated using a molecular dynamics approach, and the characteristics of multilayer aluminum films scratched into grooves are analyzed in terms of surface morphology, scratching force, structural evolution, dislocation distribution, von Mises stress and shear strain. The results indicate that in the scratching simulation process, multilayer aluminum film has a higher number of removed atoms and a larger atomic displacement compared to single layer aluminum film, which is conducive to precise shape control of the groove. The average tangential force and normal force of multilayer aluminum film show a decreasing trend compared to single layer aluminum film, which helps to scratch grooves and reduce tool wear. The total length of the dislocation lines of the multilayer aluminum film is large, and the distribution area is large, which improves the precision of scratching the grooves. Therefore, an appropriate increase in the number of aluminum film layers has a precise control effect on the groove shape. This study has certain reference significance for analyzing the complex grooving deformation law of grating aluminum film, improving the diffraction efficiency of grating aluminum film, and further improving the manufacturing process of grating aluminum film. [ABSTRACT FROM AUTHOR]

We present the design and experimental demonstration of multilayer etched CMOS-compatible grating couplers with high efficiency on a heterogeneous silicon-lithium niobate platform. The dual-level grating coupler comprises 90 nm-thick Si waveguides and 220 nm-thick Si grating with a linear chirped structure without etching LN. The design changes the grating diffraction properties, which not only reduce back reflection but also improve directionality and fiber-to-chip mode match. In comparison with existing studies, this work achieves high coupling efficiency solely through CMOS-compatible etching without additional bottom reflectors or high-index overlays. Theoretical calculations predict a fiber-to-chip coupling efficiency of −1.76 dB and an off-chip diffraction efficiency of −1.1 dB for the TE mode. The experimental measurement of the peak coupling efficiency is −2.84 dB with the back reflection as low as −26 dB. The grating coupler paves the way for monolithic integration of Si and LN. [ABSTRACT FROM AUTHOR]

The influence of grating filling factor on the spectral sensitivity of sensors, characterized by full width at half maximum (FWHM) and a figure of merit (FOM), operating on the principle of waveguide mode resonance in dielectric gratings formed on a substrate, has been investigated. Resonant wavelengths were determined for varying grating thicknesses and filling factors. Sensitivity values were obtained for normally and obliquely incident plane waves, as well as for Gaussian beams. Additionally, a scaling rule is presented, allowing determination of sensor parameters using a calculator based on identical grating parameters and corresponding resonant wavelengths. This method holds when linear dimensions of the grating and tested wavelengths are scaled proportionally. [ABSTRACT FROM AUTHOR]

Liquid crystal polarization gratings liquid crystal Pancharatnam‐Berry phase optical element (LCPGs) are a superior alternative to traditional diffraction gratings due to their high diffraction efficiency, strong polarization sensitivity, and versatile tunability. This paper introduces an electrically switchable liquid crystal polarization grating based on cholesteric liquid crystals (CLCs). The LCPG is designed to operate in reflective (R‐mode) and transmissive (T‐mode) states. It utilizes the standing helical (SH) configuration of CLCs for reflective functionality and transitions to a lying helical (LH) configuration for transmissive operations. This dual‐mode capability is achieved through a unique application of electric fields, which reorient the liquid crystal helix axis according to the desired optical function. The performance of the LCPG in both R‐mode and T‐mode is evaluated by applying different frequencies and voltages to dynamically switch between the helical states. The manufacturing process is simple, and the device performs robustly. This suggests that the technology could be useful for developing optical systems that require dynamic control over light modulation. [ABSTRACT FROM AUTHOR]

A low‐cost single frequency laser, emitting in the mid‐infrared spectral region and dissipating minimal electrical power, is a key ingredient for the next generation of portable gas sensors for high‐volume applications involving chemical sensing of important greenhouse and pollutant gases. Herein, a Quantum Cascade Surface Emitting Laser (QCSEL) is proposed, which is implemented as a short linear cavity with high reflectivity coated end‐mirrors to suppress any edge emission and employs a buried semiconductor diffraction grating to extract the light from the surface. By wafer‐level testing, the cavity length scaling is investigated, mirror reflectivities larger than 0.9 are extracted, and a pulsed threshold power dissipation of 237 mW for an emission wavelength near 7.5 µm is achieved. Finally, single‐mode emission with a side‐mode suppression ratio larger than 33 dB is demonstrated for a 248 µm short cavity, which is mounted with the epitaxial layer up and operated in continuous wave at 20 ∘C$^{\circ}{\rm C}$. [ABSTRACT FROM AUTHOR]

In this article, coherent manipulation of conductivity-dependent sensitivity of the surface plasmon polariton waves(SPPs) is theoretically investigated at the interface of silver metal and conductive atomic medium based on grating geometry using wavelength interrogation. It is reported that the sensitivity of SPPs depends on the phase and amplitude of the complex conductivity of the conductive atomic medium as well as the parameters of driving fields. The conductivity-dependent wavelength interrogation of sensitivity with respect to the refractive index is written as d λ / d n d (σ) and is a function of complex conductivity. A useful control in sensitivity is investigated with variation of phase and amplitude of complex conductivity as well as probe and control field detunings and Rabi frequency as well as decay rates. The order of diffraction and grating period play an important role in the manipulation of the sensitivity. The sensitivity increases with increasing grating period and decreases with increasing order of diffraction. A maximum value of sensitivity is reported to 600 nm/RIU with amplitude and phase of complex conductivity. The reported results have benefits in sensor devices and plasmonster technology. [ABSTRACT FROM AUTHOR]