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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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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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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]

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]

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]

The first mirror is the front-end optic component that reflects light emitted from the plasma to the diagnostic system in fusion plasmas. Silicon carbide (SiC), known for its relatively high mechanical strength and radiation tolerance, has been selected as the substrate material for the first mirror in the ITER divertor vacuum ultraviolet (VUV) spectrometer. To measure the reflectivity of the ellipse cylindrical SiC mirror to be manufactured, a device for reflectivity measurement in the VUV wavelength range was developed. First, the reflectivity of a sample SiC mirror (15 mm diameter × 10 mm thick) was measured across the ITER-required incidence angles, and the results are reported in this study. A hollow cathode lamp with helium gas was used as the VUV light source in the wavelength range of 23–60 nm, and a dedicated VUV spectrometer to select specific wavelengths was developed. The spectrometer utilized laminar-type replica diffraction gratings (Shimadzu 30-006) and two back-illuminated charge-coupled devices (BI-CCD, Andor DO 940P-BEN) for the grating and detector, respectively. A cropping technique with aperture was employed to precisely localize the VUV light's reflection onto the SiC mirror surface. The experimentally measured reflectivity values of SiC at the required incidence angles of VUV light were compared with theoretically calculated reflectivity curves. The oxidation layer (SiO2) formed on the SiC surface and the incidence angle of VUV light to the BI-CCD chip (E2V) would be the factors affecting the accuracy of the reflectivity. [ABSTRACT FROM AUTHOR]

The design of a vacuum ultraviolet spectroscopy system has been performed to monitor and provide feedback for impurity control in SPARC. The spectrometer, covering a wavelength range of 10–2000 Å through a flat-field configuration with diffraction gratings, incorporates five survey lines of sight. This allows for comprehensive impurity analysis across the core and four divertor regions (inner/outer and upper/lower). Its compact modular design facilitates vertical stacking of each spectrometer unit, significantly reducing space in the tokamak hall, where a dedicated radiation shielding bunker will be built. Safety features include a secondary helium enclosure to mitigate tritium permeation risks during deuterium–tritium (D–T) operations and shielding within the beamlines for enhanced radiation protection. The silicon carbide mirror design for divertor observation ensures its survivability in the in-vessel environment of SPARC, validated by thermal and electromagnetic analysis. Signal modeling and data acquisition testing results show that an exposure time of a few milliseconds is appropriate considering photon flux reaching the detector, demonstrating the system's capability for discharge control that includes disruption avoidance. [ABSTRACT FROM AUTHOR]

In this work, an imaging spectrometer with a diffraction-limited resolution of 0.043 nm is designed by using two manufacturable gradient-index (MGRIN) lenses with a linear refractive index distribution to suppress the aberrations. The MGRIN lenses are made from a combination of two separate base materials that their refractive indices are determined by the fractional composition of each base material at any point. The volume fraction of each base material in both lenses changes linearly from the front edge to the rear vertex of the lens. The input light to the spectrometer originates from a single-mode fiber with a core diameter of 9 μm and a numerical aperture of 0.1. The parallel rays after passing through the collimator are diffracted by a diffraction grating with a number of grooves of 1200 g/mm. The criteria determining the quality of the image show that the aberrations of the image have been optimally controlled. Comparing the results of this design with some similar studies done by other researchers shows that the root-mean-square radius of the spot diagram and Airy disk radius are significantly smaller than those designs. In addition, the modulation transfer function diagram has a better fit with the diffraction limit curve. These results make our proposed spectrometer have a stronger resolution than those in previous studies. [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]

Our research focuses on the development of a surface-plasmon sensor that uses a stationary surface plasmon, referred to as a "nonpropagating mode." This mode is observed when light is incident perpendicularly on a surface-plasmon sensor based on a metal diffraction grating. We performed a comprehensive analysis of the behavior of the surface-plasmon resonances within this nonpropagating mode, employing the rigorous coupled-wave analysis method. Using electron-beam lithography, sputtering, and a lift-off process, we fabricated such a surface-plasmon sensor and evaluated its optical properties rigorously. By combining simulations and experiments, we successfully utilized the nonpropagating mode to detect a liquid medium with a refractive index of 1.70. Simulations show that the nonpropagating mode arises due to a Fano resonance; i.e., to a resonant interaction between a localized surface plasmon generated at the edge of a metal grating strip during normal incidence and a propagating surface plasmon that occurs at the boundary between the metal diffraction grating and the measurement medium. The present results provide useful information for the advancement of surface-plasmon sensing technologies. [ABSTRACT FROM AUTHOR]

Topological defects (TDs) manifest in many condensed matter systems. In liquid crystals (LCs), they occur as point or line singularities in the otherwise smooth director profile. Engineered and controllable TDs are of great interest for functional optoelectronic devices; however, the formation mechanism in patterned devices is not fully understood. In this work, electrically addressable TDs in doped mixtures of prototypical n‐alkyl‐cyanobiphenyl LCs 4‐cyano‐4′‐pentylbiphenyl (5CB) and 4‐cyano‐4′‐octylbiphenyl (8CB) are focused on. Doping concentrations of hexadecyltrimethylammonium bromide (CTAB) are varied and the effect of varying the host LC properties (through binary 5CB:8CB mixtures) on defect formation is studied. In the results, a strong correlation between LC "fluidity" and the ease of defect array formation is presented, with 0.5 wt% CTAB‐doped 5CB giving the best controllability/uniformity of TDs at low‐threshold voltages. Furthermore, it is demonstrated that the devices can be utilized as electrically switchable optical diffractive elements. In these findings, directions are mapped out that future studies can take in designing deterministic, electrically or magnetically tunable TD‐based photonic devices using LC systems. [ABSTRACT FROM AUTHOR]

The scanning nuclear microprobe of the Institute of Applied Physics of the National Academy of Sciences of Ukraine is an analytical channel based on the compact electrostatic accelerator “Sokol” of the Van de Graaff type with the maximum voltage at the high-voltage terminal of 2 MV and is designed for local non-destructive analysis of samples of various origins with high sensitivity (~1 ppm), as well as for the fabrication of three-dimensional small structures of high quality using proton beam writing. The resolution of the microprobe is about 3 μm with a beam current of I ~ 100 pA and 0.6 μm with I ~1 pA. The maximum scanning raster with a focused beam on the sample surface is 1 × 1 mm² . The microprobe implements the techniques of particle-induced X-ray emission, Rutherford backscattering, and secondary electron microscopy. The article also gives examples of the use of the nuclear microprobe in physical research. [ABSTRACT FROM AUTHOR]

Hyperspectral detection of the change rate of organic matter content in agricultural remote sensing requires a high signal-to-noise ratio (SNR). However, due to the large number and efficiency limitation of the components, it is difficult to improve the SNR. This study uses high-efficiency convex grating with a diffraction efficiency exceeding 50% across the 360–850 nm range, a back-illuminated Complementary Metal Oxide Semiconductor (CMOS) detector with a 95% efficiency in peak wavelength, and silver-coated mirrors to develop an imaging spectrometer for detecting soil organic matter (SOM). The designed system meets the spectral resolution of 10 nm in the 360–850 nm range and achieves a swath of 100 km and a spatial resolution of 100 m at an orbital height of 648.2 km. This study also uses the basic structure of Offner with fewer components in the design and sets the mirrors of the Offner structure to have the same sphere, which can achieve the rapid adjustment of the co-standard. This study performs a theoretical analysis of the developed Offner imaging spectrometer based on the classical Rowland circular structure, with a 21.8 mm slit length; simulates its capacity for suppressing the +2nd-order diffraction stray light with the filter; and analyzes the imaging quality after meeting the tolerance requirements, which is combined with the surface shape characteristics of the high-efficiency grating. After this test, the grating has a diffraction efficiency above 50%, and the silver-coated mirrors have a reflection value above 95% on average. Finally, the laboratory tests show that the SNR over the waveband exceeds 300 and reaches 800 at 550 nm, which is higher than some current instruments in orbit for soil observation. The proposed imaging spectrometer has a spectral resolution of 10 nm, and its modulation transfer function (MTF) is greater than 0.23 at the Nyquist frequency, making it suitable for remote sensing observation of SOM change rate. The manufacture of such a high-efficiency broadband grating and the development of the proposed instrument with high energy transmission efficiency can provide a feasible technical solution for observing faint targets with a high SNR. [ABSTRACT FROM AUTHOR]

The existence of amplified spontaneous emission (ASE) is a fundamental principle of laser dyes. ASE indicates the spectral variation of the optical gain of a laser dye. Analyzing the spectral distribution of ASE is important for designing lasers. We demonstrate ASE investigations on planar waveguides made of a (co-)polymer. Similar to organic DFB (distributed feedback) lasers, a line grating allows a partial decoupling of the guided radiation. This decoupled radiation is detected as an indicator of the guided radiation. The diffraction of the radiation is utilized to perform a spectrally selective investigation of the ASE by spatially splitting it. This analysis method reduces the influence of isotropic photoluminescence and allows ASE to be analyzed across its entire spectrum. We were able to observe ASE in F8BT over a range from λ A S E , m i n = 530 nm to λ A S E , m a x = 570 nm and determine ASE threshold power densities lower than E A S E < 2.57 μJ/cm2. The study of the power density of the ASE threshold is performed spectrally selectively. [ABSTRACT FROM AUTHOR]

Large-scale diffraction gratings were fabricated in surface relief on azobenzene thin films and transferred to flexible PDMS substrates using soft lift-off lithography. The PDMS gratings were strained along the grating vector axis and the resulting surface topography was analyzed using diffraction angle measurements, AFM imagery and surface plasmon resonance (SPR) spectra. All measurement methods exhibited a linear response in strain indicating the useability of these sensors in real-world applications. For SPR-based strain sensing, an increasing pitch and a decreasing modulation depth were observed with increasing strain. The SPR peak shifted by ~1.0 nm wavelength and the SPR intensity decreased by ~0.3 a.u. per percentage of applied strain. The tested PDMS samples retained their integrity even after multiple cycles of stretching and relaxation, making them a suitable strain sensor. [ABSTRACT FROM AUTHOR]

In this study, we revealed the impact of pumping scheme, fibre length, pumping power, and the reflectivity of the output fibre Bragg grating on the performance of a Tm3+-doped fibre laser (TDFL) operating at a wavelength of 1.72 µm. Numerical simulations enabled the optimization of output power and the reduction of losses due to reabsorption, as well as amplified spontaneous emission (ASE) around 1820 nm. The Tm3+-doped fibre (TDF) was bi-directionally pumped at 1570 nm to enhance pump absorption. The simulations suggest that a maximum power of 5.96W at 1.72 µm and a slope efficiency of 64% are achievable using a Tm3+-doped silica fibre with a bi-directional pump of 4Wforward and 6Wbackward. [ABSTRACT FROM AUTHOR]

An all-liquid flexible metamaterial crossing the ultrabroadband range of S, C, X, and Ku bands is reported. This work demonstrates for the first time a frequency selective absorber (FSA) using all-flexible materials, which enables a transmission band of 2.4–4 GHz and a 6–20 GHz ultrawideband absorption. Firstly, liquid metal (LM) as a new functional material with self-healing capability and high reflectivity, based on its metasurface can realize the minimum insertion loss of 0.72 dB at 3.2 GHz. Then, utilizing dielectric resonance and diffraction grating effects of the water-based metasurface, the design can achieve greater than 90% absorption in the frequency band of 6–20 GHz, with a relative bandwidth of 107%. Furthermore, by miniaturizing the design, the FSA exhibits high stability in TM mode with oblique incidence up to 60° and TE mode at 45°. Our design can be fabricated using polydimethylsiloxane lithography and encapsulated with water and LM with a thickness of only 8 mm. Finally, the fabricated FSA are tested by bending to different curvatures, and the good performance indicates its promising applications in electromagnetic stealth, compatibility and wearable devices. [ABSTRACT FROM AUTHOR]

The concept of an optical profiler based on optical resonance was proposed, highlighting the initial requirements for mode number estimation. We proposed a method for estimating the longitudinal mode number of a laser propagating in an external cavity diode laser with high accuracy, utilizing dual-periodic diffraction gratings. These gratings were fabricated using interference lithography. To estimate the mode number, the wavelengths of two different modes are compared. Therefore, the greater the difference between the wavelengths, the higher the accuracy of the mode number determination. While the mode number difference was approximately 35 when using a conventional diffraction grating, this could be increased by a factor of 20 to around 700 using the dual-periodic grating. The relative accuracy achieved was 1.4 × 10−5. [ABSTRACT FROM AUTHOR]

Two-sided approximate boundary conditions are obtained for an absolutely absorbing ("black") layer lying on a multilayer dielectric. Paired summation equations (PSEs) are obtained for the tangent components of the electric and magnetic field strengths at the slots. These equations are solved by the Galerkin method with basis functions in the form of Chebyshev and Legendre polynomials. The resulting system of linear algebraic equations has fast internal convergence. To control the accuracy of the obtained solution, a dual problem is solved – a lattice of "black stripes." In this case, the unknowns in the PSU are the current density on the strips. The properties of lattices are analyzed. [ABSTRACT FROM AUTHOR]

In this paper, we describe the design and construction of a spectrophotometer of easy economic access that operates in the region of 300 nm to 700 nm as a proposal for qualitative and quantitative demonstrations of optical spectroscopy in physics courses of secondary education, undergraduate in physics, chemistry, biology, and some engineering. The spectrophotometer is made up of four basic elements: a slit, a 1000 lines/mm diffraction grating, a TSL1402R sensor, and an Arduino MEGA board. The light that passes through the slit is collimated by a first lens at a focal length of 5 cm. The collimated beam hits the diffraction grating of 1000 lines/mm, where it is diffracted and subsequently focused by a second lens (with a focal length of 5 cm) for the sensor, which is controlled by the Arduino MEGA. The spectra were visualized in real time by the serial plotter of the Arduino IDE and subsequently analyzed by OriginLab. To demonstrate the potential of the spectrophotometer presented here, it was used to visualize the spectra generated by different light sources for domestic use. The spectra obtained with the proposed spectrophotometer compared to those obtained using a commercial spectrophotometer, showed quite similar results, thus demonstrating the performance of the spectrophotometer and concluding that the spectrophotometer operates satisfactorily to carry out future investigations. [ABSTRACT FROM AUTHOR]

Plasmonic sensors have great potential for widespread usage. However, the prohibitive cost of noble metals restrains the wider adoption of these devices. The aim of our study is to develop a cost-effective Al-based alternative to common noble metal-based plasmonic detectors. We considered a structure consisting of an n-type doped Si wafer with a shallow p-n junction and an overlying Al grating with a trapezoidal groove profile. The RCWA (rigorous coupled-wave analysis) method was used to numerically calculate the distribution of absorbed light energy in the plasmonic detector layers and to optimize the grating parameters. Based on the simulation results, experimental samples of plasmonic photodetectors with optimal grating parameters (period—633 nm, relief depth—50 nm, groove filling factor—0.36, and thickness of the intermediate Al layer—14 nm) were manufactured, and their properties were studied. For these samples, we obtained a polarization sensitivity value of Ip/Is = 8, an FWHM of the resonance in the photocurrent spectrum ranging from 50 to 100 nm, a sensitivity at the resonance maximum of Iph = 0.04–0.06 A/W, and an angular half-width of photocurrent resonance of Δθ = 5°, which are comparable to noble metal-based analogs. Our results may be used for creating cost-effective high-sensitivity plasmonic sensors. [ABSTRACT FROM AUTHOR]

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]

Diffraction gratings have always been used to effectively couple optical radiation within integrated waveguides. This is also valid for plasmonic structures that support Surface Plasmon Polariton (SPP) waves. Traditional gratings usually excite SPP waves at the interface where they are located or, for thin metal nanostrips, at both interfaces. But reducing the thickness of the metal layer in the presence of a grating has the handicap of increasing the tunnelling of light towards the substrate, which means higher losses and reduced coupling efficiency. In this paper, we design and optimize novel gratings buried within the metallic thin films for selective coupling of SPP waves onto individual interfaces. Compared with traditional superficial gratings, the novel buried ones demonstrate higher efficiency and much lower residual tunnelling of light through the coupling structures. [ABSTRACT FROM AUTHOR]

Extending the scope of the self-imaging phenomenon, traditionally associated with linear optics, to the domain of magnonics, this study presents the experimental demonstration and numerical analysis of spin-wave (SW) self-imaging in an in-plane magnetized yttrium iron garnet film. We explore this phenomenon using a setup in which a plane SW passes through a diffraction grating, and the resulting interference pattern is detected using Brillouin light scattering. We have varied the frequencies of the source dynamic magnetic field to discern the influence of the anisotropic dispersion relation and the caustic effect on the analyzed phenomenon. We found that at low frequencies and diffraction fields, the caustics determine the interference pattern. However, at large distances from the grating, when the waves of high diffraction order and number of slits contribute to the interference pattern, the self-imaging phenomenon and Talbot-like patterns are formed. This methodological approach not only sheds light on the behavior of SW interference under different conditions but also enhances our understanding of the SW self-imaging process in both isotropic and anisotropic media. [ABSTRACT FROM AUTHOR]

Liquid crystal diffractive sails can generate controllable tangential radiation pressures, which have advantages in the Solar Polar Imager mission (SPI). This paper proposes a composite diffractive sail design consisting of an ideal passive diffraction grating sail and liquid crystal polarization gratings (LCPGs). The main diffractive grating sail generates thrust for orbital transfer with a sun-facing attitude. An optimal 3.8-year transfer trajectory is obtained by an improved direct method. Small-area LCPGs distributed around the edge are used for three-axis attitude control. The LCPGs can continuously modulate the force and torque by controlling the applied voltage based on the electro-optical characteristic of liquid crystal materials. A control strategy, including an adaptive attitude-tracking PD controller and a control allocation method, is designed to track the attitude profile generated by the transfer trajectory. Finally, the attitude-orbit coupling dynamics are used to simulate the whole process, and the results show that orbital insertion errors are minor. • A combined diffractive solar sail model using liquid crystal polarization gratings. • Independent and controllable three-axis attitude control of diffractive solar sails. • Optimizing transfer trajectory for solar polar mission based on the proposed sail. • An adaptive attitude-tracking PD controller and a control allocation method. [ABSTRACT FROM AUTHOR]

We demonstrate a pulsed Er-doped ZBLAN fiber laser operating at 3.75 μm based on the gain-switching scheme. A diffraction grating is introduced as a wavelength selection component to enable stable lasing in this long-wavelength region that deviates from the emission peak of 4F9/2→4I9/2 transition in Er3+. Different from the conventional gain-switching behavior where the pulse repetition frequency of the output laser is same as the that of the pump, the gain-switched laser demonstrated here shows a variable pulse repetition frequency, which accounts for 1/n (n = 4, 3, 2) of the pump pulse repetition frequency, in response to the 1950 nm pump power. The output pulse characteristics, including average output power, repetition frequency, pulse duration, and peak power, are investigated in detail. Over 200 mW average output power at 3.75 μm was obtained at 12 W of 1950 nm pump power. This work demonstrates that the Er-doped ZBLAN fiber laser, in combination with gain-switched scheme, is a feasible and promising approach to generate powerful pulsed emission > 3.7 μm. [ABSTRACT FROM AUTHOR]

In this work, we study the polarization properties of diffraction gratings recorded in thin films of the azopolymer PAZO (poly[1-[4-(3-carboxy-4-hydroxyphenylazo)benzene sulfonamido]-1,2-ethanediyl, sodium salt]) using digital polarization holography. Using two quarter-wave plates, the phase retardation of each pixel of the SLM is converted into the azimuth rotation of linearly polarized light. When recording from the azopolymer side of the sample, significant surface relief amplitude is observed with atomic force microscopy. In contrast, recording from the substrate side of the sample allows the reduction of the surface relief modulation and the obtaining of polarization gratings with characteristics close to an ideal grating, recorded with two orthogonal circular polarizations. This can be achieved even with a four-pixel period of grating, as demonstrated by our results. [ABSTRACT FROM AUTHOR]