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Efficiently shaping femtosecond, transverse Gaussian laser beams to flat-top beams with flat wavefronts is critical for large-scale material processing and manufacturing. Existing beam shaping devices fall short either in final beam homogeneity or efficiency. We present an approach that uses refractive optics to perform the majority of the beam shaping and then uses a fine-tune device (spatial light modulator) to refine the intensity profile. For the beam that we selected, circularly asymmetric with intensity fluctuations, our method achieved a uniformity of 0.055 within 90% of the beam area at 92% efficiency. The optimization involved an iterative beam shaping process that converged to optimum within 10 iterations.

Airy beams showing curved paths have found extensive applications in fields such as optical trapping, biomedical analysis, and material processing. Despite their utility, dynamic control of Airy beams poses a significant challenge. This work investigates the experimental realization of dynamic steering of Airy beams by utilizing computer-generated holograms with phase-amplitude encoding on a phase-only spatial light modulator (SLM). We successfully generated and controlled Airy beams by imposing dynamic phase masks that manipulated both the phase and amplitude of the field, which sets our approach apart from conventional methods with only phase manipulation. By directly encoding in situ such a hologram and transferring it to an SLM, we are able to control the initial position and rotational orientation of Airy beams without relying on mechanical movement or traditional optical setups involving lenses and apertures. Generating Airy beams in any initial position and rotational direction is anticipated to significantly impact applications such as optical trapping, optical communication, and biomedical imaging by providing a flexible platform for dynamic Airy beam manipulation.

We propose a method of the formation of spiral-shaped microreliefs in thin films of chalcogenide glasses. The method is based on projection lithography using laser beams with a structured polarization distribution. To control the polarization of the initial laser beam, a spatial light modulator HOLOEYE LC 2012 is used. It is shown that changing the contrast of the mask images displayed on the modulator display affects the convexity/concavity of the formed profiles. This approach can be effectively used for the direct laser fabrication of more complex nano-/microelements, as well as their arrays.

Diffractive Optical Elements (DOEs) are indispensable tools across numerous technological domains due to their capacity to manipulate light with sophistication and versatility. Their compact dimensions, lightweight nature, and compatibility with diverse materials render DOEs as prime candidates for integration into various optical systems, spanning from consumer electronics to state‐of‐the‐art scientific devices. Thus, DOEs stand as essential catalysts in technological advancement, facilitating innovation and unlocking new applications across a broad spectrum of disciplines. In this comprehensive review paper, Numerous types of DOEs widely acknowledge for their efficacy in both free space optics and imaging applications are delved. Beyond mere enumeration, their practical applications, elucidating their transformative impact on these fields are carefully examined. Furthermore, the challenges encountered in their implementation are dissected, paving the way for insightful discussions on future trajectories and advancements. [ABSTRACT FROM AUTHOR]

Liquid crystals have been applied to light modulation devices by taking advantage of their prominent feature of electro-optical response. The modulation contains the amplitude (intensity) modulation and the phase modulation. The most common device of the intensity modulation is a liquid crystal display. On the other hand, devices that apply the phase modulation function have also been attracting attention in the market in recent years. However, the operating principle of phase modulation devices is difficult to understand because the concept of phase is less familiar than that of intensity. Taking up a simple light beam steerer using liquid crystal as an example of the phase modulator, this paper explains its operating principle through numerical simulation. [ABSTRACT FROM AUTHOR]

An adaptive method for wavefront aberrations compensating has been developed based on the use of a spatial light modulator, the phase function of which is matched to a set of Zernike functions. It is proposed to use the second central moment of intensity of the focal image as a functional. A study of the second central moment was carried out for both individual wavefront aberrations and their superposition. It is shown that achieving the reference value of the second moment can serve as a sign of sufficient compensation for aberration. [ABSTRACT FROM AUTHOR]

A matrix formalism, denoted as ABCD, has been developed and experimentally implemented to describe structured transformations and the orbital angular momentum of structured Laguerre–Gaussian beams in an astigmatic optical system containing a single cylindrical lens. It is demonstrated that the matrix formalism not only aligns well with the method of integral astigmatic transformations but also significantly broadens the scope of its application. [ABSTRACT FROM AUTHOR]

Airy beams showing curved paths have found extensive applications in fields such as optical trapping, biomedical analysis, and material processing. Despite their utility, dynamic control of Airy beams poses a significant challenge. This work investigates the experimental realization of dynamic steering of Airy beams by utilizing computer-generated holograms with phase-amplitude encoding on a phase-only spatial light modulator (SLM). We successfully generated and controlled Airy beams by imposing dynamic phase masks that manipulated both the phase and amplitude of the field, which sets our approach apart from conventional methods with only phase manipulation. By directly encoding in situ such a hologram and transferring it to an SLM, we are able to control the initial position and rotational orientation of Airy beams without relying on mechanical movement or traditional optical setups involving lenses and apertures. Generating Airy beams in any initial position and rotational direction is anticipated to significantly impact applications such as optical trapping, optical communication, and biomedical imaging by providing a flexible platform for dynamic Airy beam manipulation. [ABSTRACT FROM AUTHOR]

Ultrashort pulsed laser ablation is an excellent process for high precision micromachining of thin substrates across a broad range of solid materials. As a special application, this method is used in laser drilling to create functional surfaces, e.g. porous materials for filtration or electrodes for electrolysis. This study proposes a different physical alternative to conventional pulsed laser drilling by transitioning the process from a gaseous atmosphere to a denser and thermally more conductive liquid medium. To overcome physical limitations from a low plasma energy threshold and time-related impediments associated with pressure wave and cavitation bubble formation, this study explores different pulse energies at 1032 nm central wavelength with MHz and GHz burst technology and a combined process parallelization through multi-beam generation with a high-power spatial light modulator. Utilizing laser bursts, hole densities of 924 / mm² with diameters as small as 2 micrometers can be generated over large areas of up to 2500 mm². In combination with multi-beam processing, the effective drilling time can be reduced below 5 ms / hole for a total of 9 parallel beams. All tests were conducted on 25 micrometer thin foils of titanium grade 1, immersed in flowing deionized water. [ABSTRACT FROM AUTHOR]

In the fast‐growing field of integrated photonics, quantifying the dispersive characteristics of the optical components integrated on chip is of key importance. The short length of on‐chip components, however, makes it challenging to measure their dispersive properties. Hence, experimental data are relatively scarce, especially at wavelengths close to the zero‐dispersion wavelength (ZDW) where the dispersion‐length product becomes very small. Ideally, the dispersion should be characterized with a technique that, besides being highly sensitive, “directly” yields the dispersion value without frequency derivative calculations nor the addition of dedicated on‐chip measurement structures. To fulfill these requirements, a dispersion characterization technique is presented relying on femtosecond‐resolution time‐of‐flight measurements combined with advanced spatial light modulator (SLM) technology. With this new “direct” technique, suitable for measuring dispersion‐length products down to 5 × 10−5 ps nm−1, the dispersion of mm‐length silicon nitride waveguides is characterized, both in the weakly dispersive (close to the ZDW) and strongly dispersive regimes. Furthermore, dispersion data are presented for sub‐mm‐length trident couplers and inverted taper couplers connected to the waveguides. The resulting insights into the waveguides’ and couplers’ dispersive properties, and the wide applicability of the technique, will benefit the development of advanced photonic integrated circuits (PICs) in silicon nitride and other waveguide material platforms. [ABSTRACT FROM AUTHOR]

At present, there is a large number of aspherical surfaces in the optical systems. However, making separate compensators to detect each aspherical surface is costly, lack versatility, and faces processing challenges. To solve the problem that different compensators are needed for various aspherical surfaces with different parameters, a method of interferometric surface test put was forward by using spatial light modulator (SLM) as a null-test compensator. This method combined a polarizing beam splitter and waveplates to construct a testing optical path, so as to achieve the measurement of aspheric surface errors. The interferometric testing method was validated by simulating the testing optical path of a field lens with concave aspherical surfaces on both surfaces on ZEMAX. In the meantime, the wavefront modulation error of SLM was simulated and analyzed through MATLAB. The simulation results indicate that the method can test different aspheric surface errors, and the wavefront modulation accuracy within the designed optical path reaches up to 0. 008 3λ. [ABSTRACT FROM AUTHOR]

In this work, we propose a structured-illumination lensless digital holographic microscopy (SI-LDHM). SI-LDHM illuminates a sample with 24 structured illuminations (8 orientations × 3 phase shifts) and records the defocused interferogram formed by two copies of object waves along the ±1st diffraction orders of each SI. The reconstructed object waves under different illumination orientations are respectively propagated to the sample plane along the +1st diffraction order and then averaged, thus yielding a clean image without the artifact of twin images. Experimental results demonstrated that thanks to the multi-oriented SI strategy, the twin image in SI-LDHM is sevenfold reduced compared to conventional DHM, while the spatial resolution is 1.15 times higher. [ABSTRACT FROM AUTHOR]

Significance: The feedback-based wavefront shaping emerges as a promising method for deep tissue microscopy, energy control in bio-incubation, and re-configurable structural illuminations. The cost function plays a crucial role in the feedbackbased wavefront optimization for focusing light through scattering media. However, popularly used cost functions, such as intensity (η) and peak-to-background ratio (PBR) struggle to achieve precise intensity control and uniformity across the focus spot. Aim: We have proposed an l2-norm-based quadratic cost function (QCF) for establishing both intensity and position correlations between image pixels, which helps to advance the focusing light through scattering media, such as biological tissue and ground glass diffusers. Approach: The proposed cost function has been integrated into the genetic algorithm, establishing pixel-to-pixel correlations that enable precise and controlled contrast optimization, while maintaining uniformity across the focus spot and effectively suppressing the background intensity. Results: We have conducted both simulations and experiments using the proposed QCF, comparing its performance with the commonly used η and PBR-based cost functions. The results evidently indicate that the QCF achieves superior performance in terms of precise intensity control, uniformity, and background intensity suppression. By contrast, both the - and PBR cost functions exhibit uncontrolled intensity gain compared with the proposed QCF. Conclusions: The proposed QCF is most suitable for applications requiring precise intensity control at the focus spot, better uniformity, and effective background intensity suppression. This method holds significant promise for applications where intensity control is critical, such as photolithography, photothermal treatments, dosimetry, and energy modulation within and outside bio-incubation systems. [ABSTRACT FROM AUTHOR]

The continuous miniaturization of semiconductor devices has increased the demand for advanced process control technologies. This process requires real-time measurement systems to monitor manufacturing parameters to ensure efficiency and high quality. This study introduces a novel optical module that uses a spatial light modulator to extract key-point intensity distributions from diffraction images in scatterometry. The efficacy of this method is demonstrated on a grating target with a pitch of 855 nm using a feature extraction algorithm that identifies key point locations based on calculated diffraction images. A particularly designed off-axis extraction pattern facilitates the acquisition of key-point intensity distributions. Moreover, incorporating a cylindrical lens into the optical setup reduces the image feature dimensionality, thereby decreasing the data storage space and enabling the output in a streamlined vector format conducive to further analysis. Experimental data on the development of this scatterometry-based optical module and the subsequent validation of the key-point extraction method indicate a maximum mean absolute error of 0.0080 and a cosine similarity consistently above 0.9999. This study integrates image analysis and measurement techniques by optics, providing a more efficient pathway for key-point extraction in diffraction images, offering the potential for improving real-time process monitoring in the semiconductor manufacturing industry. [ABSTRACT FROM AUTHOR]

Earth observation (EO) is crucial for addressing environmental and societal challenges, but it struggles with revisit times and spatial resolution. The EU-funded SURPRISE project aims to improve EO capabilities by studying space instrumentation using compressive sensing (CS) implemented through spatial light modulators (SLMs) based on micromirror arrays (MMAs) to improve the ground sampling distance. In the SURPRISE project, we studied the development of an MMA that meets the requirements of a CS-based geostationary instrument working in the visible (VIS) and mid-infrared (MIR) spectral ranges. This paper describes the optical simulation procedure and the results obtained for analyzing the performance of such an MMA with the goal of identifying a mirror design that would allow the device to meet the optical requirements of this specific application. [ABSTRACT FROM AUTHOR]

In order to solve the problems of high processing difficulty and limited spectral application range of specific spectra device in traditional quadriwave lateral shearing interferometry system, dividing incident light beam into four beams of lateral shearing coherent wavelets was proposed by using a spatial light modulator instead of a spectro grating. The diffraction efficiency of wavelets was adjusted flexibly by adjusting the refractive index of grating to adapt to the illumination light source, and the optical path difference distribution reflecting the height information and refractive index of the sample was reconstructed according to the interference effect between two wavelets, so as to realize accurate measurement of surface topography in a wide spectral and large dimensions range. In this study, the effect of incident light wavelength on the reconstruction accuracy of optical path difference was investigated by combining the Fourier transform method, and a wide spectrum quadriwave lateral shearing interferometry system from the visible to near infrared was built using a spatial light modulator. The results show that the system measured the etching depth of a standard quartz sample at 209.39 nm ± 1.72 nm, which is basically consistent with its nominal value of 210.83 nm ± 2.39 nm and the measurement value of 212.92 nm ± 1.35 nm by white light interferometer, which verifies the effectiveness of the surface topography measurement method proposed. This study can provide a theoretical reference for the extended application of quadriwave lateral shearing interferometry in the field of surface topography measurement. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Liquid Crystal & Displays is the property of Chinese Journal of Liquid Crystal & Displays and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The structuring of lithium-ion battery (LIB) electrodes and the diffusion media (DM) for polymer electrolyte membrane fuel cells (PEMFCs) with ultrashort laser pulses enables improved performance characteristics of both technologies. However, the transfer of the approaches from a laboratory scale to a commercial use has previously been hindered by the low average output power of ultrashort-pulsed (USP) laser beam sources and the limited productivity of single-beam structuring using scanning optics. Recent advancements in the development of USP laser systems have led to a steady increase in the available output power, thereby enabling new fields of applications. This study aims at accelerating the USP laser structuring of LIB electrodes and DM for PEMFCs to industrially relevant processing rates by comparing a single-beam with a multibeam structuring process regarding ablation characteristics and quality. For the multibeam strategy, the shape of the laser beam was modified by a spatial light modulator (SLM). In addition to microholes, the insertion of microchannels was investigated to demonstrate the high flexibility of state-of-the-art SLMs. The geometry of the created structures was measured with a laser scanning microscope, and the different layers were tested for their geometrical and electrochemical properties to compare both technologies. The results confirmed that applying an SLM enables high-quality microstructures with significantly higher structuring rates. Furthermore, this contribution includes a theoretical analysis of the specifications required for a laser setup to reach an industrially relevant productivity of the structuring processes. [ABSTRACT FROM AUTHOR]

In this work, we propose a structured-illumination lensless digital holographic microscopy (SI-LDHM). SI-LDHM illuminates a sample with 24 structured illuminations (8 orientations χ 3 phase shifts) and records the defocused interferogram formed by two copies of object waves along the ±1st diffraction orders of each SI. The reconstructed object waves under different illumination orientations are respectively propagated to the sample plane along the +1st diffraction order and then averaged, thus yielding a clean image without the artifact of twin images. Experimental results demonstrated that thanks to the multi-oriented SI strategy, the twin image in SI-LDHM is sevenfold reduced compared to conventional DHM, while the spatial resolution is 1.15 times higher. [ABSTRACT FROM AUTHOR]

Diode-pumped multi-mode graded-index (GRIN) fiber Raman lasers provide prominent brightness enhancement both in linear and half-open cavities with random distributed feedback via natural Rayleigh backscattering. Femtosecond laser-inscribed random refractive index structures allow for the sufficient reduction in the Raman threshold by means of Rayleigh backscattering signal enhancement by +50 + 66 dB relative to the intrinsic fiber level. At the same time, they offer an opportunity to generate Stokes beams with a shape close to fundamental transverse mode (LP01), as well as to select higher-order modes such as LP11 with a near-1D longitudinal random structure shifted off the fiber axis. Further development of the inscription technology includes the fabrication of 3D ring-shaped random structures using a spatial light modulator (SLM) in a 100/140 μm GRIN multi-mode fiber. This allows for the generation of a multi-mode diode-pumped GRIN fiber random Raman laser at 976 nm with a ring-shaped output beam at a relatively low pumping threshold (~160 W), demonstrated for the first time to our knowledge. [ABSTRACT FROM AUTHOR]

A high-throughput laser micro-machining system has been developed using a programmable multi-spot modulated line beam capable of >30x throughput enhancement over a single-spot system. While commercially available lasers have been rapidly growing in output energy and power, single-spot scanning systems cannot take full advantage of these advancements. This system provides high throughput, high resolution micro-processing on a variety of surfaces (stainless steel, aluminum, and polymer). This high productivity system is enabled by a high-power MEMS spatial light modulator called the Planar Light Valve (PLVTM). The PLV is a 1088-pixel device in a linear configuration capable of 10-bit, 100 kHz amplitude modulation. The PLV supports pulse energies of ~1 mJ (1064 nm, 10 ps) and has been used at pulse widths down to 300 femtoseconds. The system can resolve features as small as 10 µm with an edge placement resolution of 2.5 µm. Large area processing is done by scanning and stitching this line beam across the media using X-Y stages and a unique relay galvo scanner has been incorporated into the system to allow for faster scanning over a 15 x 15 mm area. [ABSTRACT FROM AUTHOR]

In this work a three-dimensional diffusion model is used to model photopolymers as a recording media. This model allows us to predict the properties of the Diffractive Optical Elements (DOEs) once we recorded into the photopolymer. This model had never been tested with more complex elements, such as multifocal diffractive lenses, as presented in the following in this work. In addition, the model includes; the estimation of the refractive index modulation, the low-pass filtering effect due to the experimental optical setup, and the evolution of the transverse intensity distribution. In this way, the selection of the appropriate material characteristics depending on the intended DOE application is made possible. Specifically, an acrylamide-based PVA/AA photopolymer is simulated using the proposed model. Moreover, coverplating and index matching systems are considered together to avoid the effects of thickness variation. Furthermore, in order to compare their properties using the proposed model, we focus on Fibonacci lenses (FL), a type of bifocal lenses. This allows us to evaluate the dependence of the focii intensity on the polymerisation rate, the diffusivity parameter, low-pass filtering effect and the use of the index matching system for these lenses. This enables us to know the recording parameters in order to produce this type of multifocal diffractive lenses with higher quality and precision. [ABSTRACT FROM AUTHOR]

Wavefront distortions pose a significant limitation in various optical applications, hindering further advancements in optical system performance. In this study, a novel generic calibration model based on Zernike‐fitting neural network (ZFNN) is proposed, which enables insitu wavefront correction with just a single‐shot measurement. The experimental setup follows a standard or equivalent focal‐field imaging optical path, allowing calibration without the need to remove any components from the optical system. The ZFNN, a physics‐informed neural network, offers the advantage of not requiring prior training, eliminating the need for extensive labeled data. With a fully connected network architecture and a modest number of neurons (469), the ZFNN achieves exceptionally fast optimization speed and meets the basic requirements for real‐time calibration. Consequently, this approach holds great potential for applications such as rapid calibration of optical systems, high‐precision light field modulation, and various advanced imaging techniques. [ABSTRACT FROM AUTHOR]

Copyright of Rare Metals is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The article considers the use of digital holography in reconstructing object images from different 3D scene cross-sections. This reconstruction enables the study of different materials, characterization of microparticles in a medium, and analysis of microplastic content in water bodies. A method is proposed for reconstructing object images from digital off-axis holograms using a generative adversarial network (GAN). The generative adversarial network is used to reconstruct 3D scene cross-sections in which off-axis objects are present. The application of neural networks is shown to improve the speed and quality of reconstruction, as well as to reduce image noise. The proposed method was tested on numerically synthesized and optically measured digital holograms. By means of this method, eight 3D scene cross-sections were reconstructed using a single synthesized hologram. An average structural similarity index measure of at least 0.73 was obtained. In the study, the authors experimentally recorded sets of digital off-axis holograms of phase objects displayed on spatial light modulators to form the cross-sections of the 3D scene. In the reconstruction of object images using optically registered holograms, the average structural similarity index measure for the cross-sections of the scene amounted to 0.83. The proposed method enables a high-quality reconstruction of object images and will be useful in the analysis of micro- and macro-objects, including in biomedical applications, metrology, as well as characterization of materials, surfaces, and volume media. [ABSTRACT FROM AUTHOR]

Due to its complex spatial distribution, the higher-order Hermite–Gaussian mode possesses significant application in fields such as precision measurement and optical communication. The spatial light modulator, with its capability to modulate the complex amplitude distribution of the incident light field, finds extensive applications in optical information processing and adaptive optics, thus making it an indispensable tool in these fields. Using cascaded spatial light modulators can efficiently and superbly generate a higher-order Hermite–Gaussian mode; however, the experimental system is challenging, and there are many influencing factors, such as the misalignment between the optical field on the plane of the second spatial light modulator and the hologram loaded onto it, as well as the spot size of the optical field on the plane of the second spatial light modulator. In this paper, we analyzed the influence of the above factors on the quality of generating a higher-order Hermite–Gaussian mode, providing a reference for the efficient and high-quality generation of the higher-order Hermite–Gaussian mode. [ABSTRACT FROM AUTHOR]

The paper demonstrates a method for calculating spiral beams of a given configuration based on a linear combination of displaced Gaussian beams. A new method for generating spiral beams is implemented. The effect of scaling the phase distribution on the quality of the generated light fields is experimentally investigated. The synthesized fields are tested in an experiment on optical manipulation of ensembles of single microparticles. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Liquid Crystal & Displays is the property of Chinese Journal of Liquid Crystal & Displays and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We clarified that a ferroelectric liquid crystal (FLC) has high resolution display capability as small as 1 × 1 μm pixel pitch using an FLC pixel array with a two‐layer electrode, which has a 1 × 1‐μm‐checkered apertured electrode and a plane electrode separated by an insulation layer. By applying +2 V to the apertured electrode and −10 V to the plane electrode in the two‐layer electrode and 0 V to the transparent common electrode, a checkered pattern was clearly observed, which indicates the successful individual pixel driving with a pixel pitch of 1 × 1 μm. When fabricating 1 × 2‐μm‐pitch rectangular FLC pixels, we elucidated that the liquid crystal alignment direction should be along the shorter side of the pixels to avoid asymmetric transmittance distribution in each pixel. Moreover, we successfully reconstructed a 3D holographic image using 10 × 10 k FLC pixel array with a pitch of 1 × 1 μm driven by the two‐layer electrode with hologram‐patterned apertures. We showed that FLC is a strong candidate material for realizing spatial light modulator with extremely small pixel pitches, which is essential for holographic displays with wide‐viewing‐zone angles. [ABSTRACT FROM AUTHOR]

This paper presents the development of liquid crystal on silicon (LCOS) technology aimed at enhancing the image quality and reliability of projectors. Additionally, we introduce an 8K LCOS panel with a pixel pitch of 2.6 μm. Furthermore, we discuss the application prospects of the developed phase‐only spatial light modulator. [ABSTRACT FROM AUTHOR]

The application of non-uniform spiral gratings to control the structure, topological parameters and propagation of orbital angular momentum (OAM) beams was studied experimentally with coherent near-infrared light. Adapted digital spiral grating structures were programmed into the phase map of a high-resolution liquid-crystal-on-silicon spatial light modulator (LCoS-SLM). It is shown that characteristic spatio-spectral anomalies related to Gouy phase shift can be used as pointers to quantify rotational beam properties. Depending on the sign and gradient of spatially variable periods of chirped spiral gratings (CSGs), variations in rotation angle and angular velocity were measured as a function of the propagation distance. Propagation-dependent self-torque is introduced in analogy to known local self-torque phenomena of OAM beams as obtained by the superposition of temporally chirped or phase-modulated wavepackets. Applications in metrology, nonlinear optics or particle trapping are conceivable. [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]

Holographic display enabled by performing both amplitude modulation (AM) and phase modulation (PM) in a single Liquid Crystal on Silicon (LCoS)‐based Spatial Light Modulator (SLM) is introduced. Light propagation is manipulated in two different directions to perform both AM and PM via liquid crystals alignment layer which can be based on technologies by using photoalignment, nano‐imprint lithography (NIL), or unique over‐driving across Liquid Crystal (LC) layer of Vam‐Vpm method which are described and proved to be effective to tune incident light, control the polarization and propagation of the light entering the liquid crystals of a single LCoS‐based SLM (LCoS‐SLM) device. These methods enable holographic display and to alleviate the issues in using two separated SLMs trying to achieve the same. Further, the design techniques and methods to suppress adjacent pixels' crosstalk due to fringe field effect (FFE) [1] in 2D array are amenable to ensure higher resolution with pixel pitch down to 1¼m for compact size and higher pixel numbers beyond 8K×4K. It mitigates to reduce chores of pixel‐to‐pixel alignment, and to enhance image clarity and quality within a single LCoS‐SLM. It will be applicable to enable holographic display with such unique LCoS‐SLM particularly for AR/VR/MR smart glasses applications [18] [19] [20] once being fabricated in the future. [ABSTRACT FROM AUTHOR]

Bessel beams have multiple applications owing to their propagation-invariant properties, including particle trapping, optical coherence tomography, and material processing. However, traditional Bessel-beam shaping techniques require bulky components, which limits the development of miniaturized optical systems for integration with other devices. Here, we report a novel femtosecond laser direct writing strategy for fabricating mesoscale (from submicrometer to subcentimeter) binary optical elements with microscale resolution. This strategy utilizes femtosecond beams with a long focal depth to increase throughput while reducing the constraints on critical sample positioning. As a demonstration, we manufactured and characterized a 2.2 mm diameter binary axicon. The experimentally measured quasi-Bessel beam intensity distribution and the numerical results were remarkably consistent, demonstrating a suitable tradeoff between the overall size, efficiency, and structural fidelity. Furthermore, a compact Bessel lens containing binary axicons was constructed and successfully used for femtosecond laser mask-less ablation of periodic grating-type surface plasmon polariton excitation units. The demonstrated approach shows significant potential for fabricating customizable integrated optical components.

Realizing a spatial phase modulation (SPM) from 0 to 2π is vital for achieving precise light field manipulation, when the phase-only spatial light modulator (SLM) is driven by the voltage. However, insufficient bias voltage degrades the quality of the generated structured light. Here, we propose a superpixel method that consists of 2 × 2 adjacent pixels to equalize the imperfect SPM response, when the bias voltage is insufficient. Meanwhile, a look-up table (LUT) is established between the target light field and the superpixel equalized light field, for reducing the computational complexity of phase hologram generation. When the phase modulation depth is reduced from 2π to 1.67π, we can generate the vortex beams with better quality by the superpixel technique. Characterizing the spatial phase distribution of vortex beams through interferometry verifies the correct function of the superpixel enabled SPM equalization method. In addition, the peak signal-to-noise ratio (PSNR) is used as the metric to quantitatively evaluate the quality of the generated vortex beam. Compared with the phase modulation distortion caused by the insufficient bias voltage, the PSNR after the superpixel enabled SPM equalization is improved by 4.5 dB. Our results would facilitate various applications mediated by power-efficient phase modulation utilizing the SLM.

Earth observation (EO) is crucial for addressing environmental and societal challenges, but it struggles with revisit times and spatial resolution. The EU-funded SURPRISE project aims to improve EO capabilities by studying space instrumentation using compressive sensing (CS) implemented through spatial light modulators (SLMs) based on micromirror arrays (MMAs) to improve the ground sampling distance. In the SURPRISE project, we studied the development of an MMA that meets the requirements of a CS-based geostationary instrument working in the visible (VIS) and mid-infrared (MIR) spectral ranges. This paper describes the optical simulation procedure and the results obtained for analyzing the performance of such an MMA with the goal of identifying a mirror design that would allow the device to meet the optical requirements of this specific application.

Diode-pumped multi-mode graded-index (GRIN) fiber Raman lasers provide prominent brightness enhancement both in linear and half-open cavities with random distributed feedback via natural Rayleigh backscattering. Femtosecond laser-inscribed random refractive index structures allow for the sufficient reduction in the Raman threshold by means of Rayleigh backscattering signal enhancement by +50 + 66 dB relative to the intrinsic fiber level. At the same time, they offer an opportunity to generate Stokes beams with a shape close to fundamental transverse mode (LP01), as well as to select higher-order modes such as LP11 with a near-1D longitudinal random structure shifted off the fiber axis. Further development of the inscription technology includes the fabrication of 3D ring-shaped random structures using a spatial light modulator (SLM) in a 100/140 μm GRIN multi-mode fiber. This allows for the generation of a multi-mode diode-pumped GRIN fiber random Raman laser at 976 nm with a ring-shaped output beam at a relatively low pumping threshold (~160 W), demonstrated for the first time to our knowledge.

The orbital angular momentum (OAM) associated with structured singular beams carries vital information crucial for studying various properties and applications of light. Determining OAM through the interference of light is an efficient method. The interferogram serves as a valuable tool for analyzing the wavefront of structured beams, especially identifying the order of singularity. In this study, we propose a modified Mach–Zehnder interferometer architecture to effectively determine the topological charge of Bessel–Gaussian (BG) beams. Several numerically generated self-referenced interferograms have been used for analysis. Moreover, this study examines the propagation property and phase distribution within BG beams after they are obstructed by an aperture in the interferometer setup. [ABSTRACT FROM AUTHOR]