Phase-only Spatial Light Modulator Research Articles

Complex-valued scatter compensation in nonlinear microscopy

Nonlinear, i.e., multiphoton microscopy is a powerful technique for imaging deep into biological tissues. Its penetration depth can be increased further using adaptive optics. In this work, we present a fast, feedback-based adaptive-optics algorithm, termed C-DASH, for multiphoton imaging through multiple-scattering media. C-DASH utilizes complex-valued light shaping (i.e., joint shaping of amplitude and phase), which offers several advantages over phase-only techniques: it converges faster, it delivers higher image quality enhancement, it shows a robust performance largely insensitive to the axial position of the correction plane, and it has a higher ability to cope with, on the one hand, scattering media that vary over time and, on the other hand, scattering media that are partially absorbing. Furthermore, our method is practically self-aligning. We also present a simple way to implement C-DASH using a single reflection off a phase-only spatial light modulator. We provide a thorough characterization of our method, presenting results of numerical simulations as well as two-photon excited fluorescence imaging experiments. Published by the American Physical Society 2024

One-grating common-path phase-shifting interferometer for quantitative phase imaging

A one-grating common-path phase-shifting interferometer for quantitative phase imaging is proposed as an improvement over the original interferometer design. In the original version, the setup is long, involving a grating pair, and requires precise mechanical translation of the grating, which poses difficulties for practical applications. The proposed interferometer utilizes grating multiplexing to reduce the length of the optical setup and uses a phase-only spatial light modulator to implement pinhole filtering and phase shifting simultaneously without any moving parts, making it more conducive for the realization of a practical version.

Robust and efficient calibration method of liquid-crystal spatial light modulator based on the linear combination strategy

Abstract Phase-only spatial light modulators (SLMs) play a vital role in virous fields. However, its modulation accuracy is compromised by the static aberration and the phase response nonlinearity. To enhance the modulation accuracy, this paper presents an innovative full calibration method for SLMs, effectively addressing both static aberration and nonlinear phase responses using only two shots of camera. The main highlight of this paper is the binding of a novel linear combination strategy and a unique kinoform. This binding can eliminate phase distortion between two shots of camera, making our method dramatically robust in correcting phase response nonlinearity. Additionally, benefit from the accurate correction of phase response nonlinearity, the static aberration is accurately compensated by the single-shot spatial carrier phase-shifting technology. In conclusion, the proposed method's strong robustness, precision, and efficiency position it as an ideal solution for SLM calibration.

Finite-element Adaptive Meshing Statistics of Liquid Crystal Coaxial Phase Shifters for mmW Electronics and THz Photonics Beyond Display: A Comparative Study

Sub-mmW and THz frequencies offer ultra-high-speed communications for next-generation 5G/6G networks, wherein research advancing the understanding will benefit the electronics and photonics community. Specifically, meshing resolutions across varying frequency ranges and material properties are central to the solution accuracy, reliability, and cost (memory and time) of computational mmW and THz simulations, particularly for the emerging reconfigurable coaxial phase shifters employing nematic liquid crystals (LCs) as tunable media. In the present study, a comparative meshing statistics analysis is conducted for two devices designed for 60 GHz and 0.3 THz, respectively. Each design features two distinct tuning states (LC permittivity of 2.754 and 3.3, respectively), all pertinent to the coaxial TEM (Transverse Electromagnetic) mode. By quantifying the broadband meshing and solution statistics of diverse frequencies and dielectric tuning states for the first time, we establish memory-conserving computational metrology involving reconfigurable coaxial devices operationalized with LC-filled tunable dielectrics tailored for mmW electronics and THz photonics. Full Text: PDF References M. Makowski, I. Ducin, K. Kakarenko, J. Suszek, A. Kowalczyk, "Performance of the 4k phase-only spatial light modulator in image projection by computer-generated holography", Phot. Lett. Poland 8, 1 (2016). CrossRef J.F. Li, H.R. Li, "Liquid Crystal-Filled 60 GHz Coaxially Structured Phase Shifter Design and Simulation with Enhanced Figure of Merit by Novel Permittivity-Dependent Impedance Matching", Electronics 13, 3 (2024). CrossRef J.F. Li, H.R. Li, "Modeling 0.3 THz Coaxial Single-Mode Phase Shifter Designs in Liquid Crystals with Constitutive Loss Quantifications", Crystals 14, 4 (2024). CrossRef J.F. Li, D.P. Chu, "Liquid Crystal-Based Enclosed Coplanar Waveguide Phase Shifter for 54–66 GHz Applications", Crystals 9, 12 (2019). CrossRef Z. Cendes, "The development of HFSS", USNC-URSI Radio Science Meeting (Fajardo, IEEE 2016). CrossRef T. Vaupel, "Accuracy And Modeling Improvements For An Integral Equation Framework Applied To Thin Layer Microstrip And Substrate Integrated Waveguide (Siw) Structures", EuCAP (Copenhagen, IEEE 2020). CrossRef L.J. Jiang, W.C. Chew, "Low-frequency fast inhomogeneous plane-wave algorithm (LF-FIPWA)", Microwave Opt. Tech. Lett. 40, 2 (2004). CrossRef J. Zhu, D. Jiao, "Eliminating the Low-Frequency Breakdown Problem in 3-D Full-Wave Finite-Element-Based Analysis of Integrated Circuits", IEEE Trans. Microw. Theory Tech. 58, 10 (2010). CrossRef

Compact binocular holographic near-eye 3D display system based on a liquid crystal polarization grating

Holographic technology is considered as one of the most ideal 3D display technologies and has significant potential in near-eye display. However, binocular holographic near-eye 3D display still faces challenges such as serious visual fatigue and complex system. Here, we propose a compact binocular holographic near-eye 3D display system based on a liquid crystal polarization grating (LCPG). Based on the LCPG, the reconstructed light can be deflected respectively to left and right viewing areas. The proposed system achieves binocular display with only one phase-only spatial light modulator used to load computer-generated hologram, which makes the binocular display system more compact. Simultaneously, the proposed system reduces mismatches in the images perceived by two eyes, thus achieving a better binocular display effect. Experimental results demonstrate the feasibility of the proposed binocular holographic near-eye 3D display system with dual viewing areas. Additionally, based on the time-division multiplexing method, dynamic binocular holographic near-eye display can be achieved. The proposed system has potential applications in holographic virtual reality and augmented reality display.

Impact of altering phase modulation and geometrical shape of laser beam via a phase-only spatial light modulator on laser-induced fluorescence

This study investigates the impact of modulating and shaping a laser beam via a phase-only spatial light modulator (SLM) on the intensity of the laser-induced fluorescence (LIF) signal. Different phase modulations ranging from 0 to 2π are applied to the SLM window to evaluate the effect of the modulated beam on the emitted LIF signal from extra virgin olive oil EVOO samples. The laser beam is also shaped into circular and square geometries with varying diameters to determine the optimum size for maximizing the LIF signal strength. The results reveal that the highest LIF signal intensity could be obtained after modulating the incident laser beam with phase shifts of 0 and 2π, with an improvement factor of approximately 3 for Avanti olive oil and 1.42 for Al Jouf olive oil. Furthermore, laser beam shaping into a circular aperture with a radius of 2.45 mm or a square aperture with a side length of 2.45 mm yields the highest LIF signal improvement, with enhancement factors of approximately 2.9 for Avanti olive oil and 1.42 for Al Jouf olive oil. This work demonstrates the potential of SLM-based beam shaping techniques to optimize LIF measurements by tailoring the wavefront characteristics of the excitation laser source.

Polarization-filterless polarization-sensitive polarization-multiplexed phase-shifting self-reference digital holography

I propose a phase-shifting self-reference digital holography technique in which both three-dimensional (3D) and polarization information is simultaneously obtained without any polarization filters. A Fourier-transform lens, a polarization beam splitter, and two phase-only spatial light modulators are used to simultaneously generate self-reference holograms with orthogonal polarization directions. 3D and polarization information is multiplexed in the recorded phase-shifted digital holograms and retrieved by applying polarization-selective phase-shifting interferometry and numerical refocusing. The validity of the proposed technique is experimentally demonstrated.

Performance improved for two-photon multi-focus microscopy based on a spatial light modulator by eliminating the zero-order beam

Two-photon microscopy (TPM) has a wide range of applications in the biomedical field. Two-photon multi-focus microscopy (TPMM) greatly improves the imaging speed by combining TPM with multi-focus technology. Therefore, TPMM based on spatial light modulator (SLM) has greater advantages in generating multi-focus point (MFP) with uniform intensity and flexible position than to other schemes. However, the zero-order beam (ZOB) produced by SLM in TPMM causes imperfection of the imaging system. For example, some sample areas are scanned repeatedly or illuminated unexpectedly. In this article, we proposed a TPMM system with improved performance by eliminating the ZOB. Apart from the target MFP, we utilize a phase-only SLM to generate another corrective beam (CB) with controllable amplitude, phase, and position precisely. The CB can produce destructive interference completely with the ZOB generated by the dead areas of the SLM. The method has a larger field of view, higher efficiency, and better uniformity in generating MFP compared to the method of overlaying the blaze grating. Simulations and experiments demonstrate the advantages of this approach.

High diffraction efficiency complex amplitude modulation technique by using antiwave functions.

Complex amplitude modulation (CAM) is a single-step technique that codes the amplitude and phase of a diffracted optical field into a real function. Loading this function onto a phase-only spatial light modulator enables the reconstruction of 3D images. However, the obtained images have poor brightness because of the low diffraction efficiency. In this work, we show a novel solution, to the best of our knowledge, that overcomes this limitation. This is done by employing antiwave complex exponential functions, which modify the spectrum of the diffracted field. Proper configuration of these functions allows transferring energy across the diffraction spectrum to the informative diffraction order, which significantly improves the brightness of the reconstructed image. Simulations and experiments prove the efficiency of the proposed method.

On-demand orbital angular momentum comb from a digital laser

Photonic orbital angular momentum (OAM) carried by phase-structured vortex light is an important and promising resource for the ever-increasing demand towards high-capacity data information due to its intrinsic unlimited dimensionality. Large superpositions of OAM are easy to be produced, but on-demand generation of arbitrary OAM spectra such as an OAM comb similar to a frequency comb is still a challenge; especially, the on-demand OAM comb and arbitrary multi-OAM modes have not yet been realized at the source. Here we report a versatile at-source strategy for developing a flexibly and dynamically switchable on-demand digital OAM comb laser for the first time, to our knowledge, by controlling the phase degree of freedom itself rather than any proxy. For this aim, we present a crucial design idea that a nested ring cavity configuration is composed of a degenerate cavity embedded into a stable ring cavity and a pair of conjugate two-fold symmetric multi-spiral-phase digital holographic mirrors loaded onto reflective phase-only spatial light modulators. In the nested ring cavity, the stable ring cavity and the degenerate cavity meet the requirements of high spatial coherence and supporting any transverse mode, respectively. The paired conjugate holographic mirrors located in mutual object and image planes circumvent the competing issue among different OAM modes and control the number and chirality of modes in OAM combs with ease. Our strategy has also universality as it has the ability of encoding OAM spectra with arbitrary distribution. The realization of a dynamic on-demand multi-OAM-mode laser is an important progress in the infancy of multi-OAM-mode sources. Our idea provides a promising solution for development of emerging high-dimensional technologies; in the future, there will be increasing opportunities in the fundamentals and applications of high-dimensional OAM modes, and beyond. Our strategy not only contributes to the development of new laser technology, but also provides a toolbox for both linear and nonlinear generation of the multiple OAM modes at the source.

Adaptive phase control of a phase-only spatial light modulator using the Shack-Hartmann wavefront sensor

We present a method to study both static and dynamic phase errors in a phase-only spatial light modulator (SLM) caused by surface irregularities and an imperfect response of each pixel to the applied field. This, in turn, degrades optical reconstruction, particularly in holographic projection applications. The approach uses the Shack-Hartmann wavefront sensor (SHWFS) to measure these errors. A plane wave illuminates the SLM, and the reflected wavefront is measured by the SHWFS and converted into a phase-only computer-generated hologram (CGH). This CGH is displayed on the SLM to compensate for phase errors, which are verified by subsequent wavefront measurements. Experimental results demonstrate the simplicity, robustness to vibration, and real-time capabilities of the SHWFS in contrast to interferometric methods.

Non-mechanical steering of the optical beam in spectral-domain optical coherence tomography

We demonstrate in a proof-of-concept experiment spectral-domain optical coherence tomography where steering of the optical beam that probes the sample in a transverse scan does not make use of any mechanical element. Steering is done with the help of a phase-only spatial light modulator, that introduces a spatially-dependent phase between the two orthogonal polarization components of an optical beam, and some optical elements that control the polarization of light. We demonstrate that making use of the non-mechanical beam steering system considered here, we can reproduce the main traits of imaging with standard OCT that makes use of mechanical-assisted optical beam steering.

Experimental optical encryption with full complex modulation

We present, to our knowledge, a novel method to achieve experimental encryption using double random phase encoding with full complex modulation and a single phase-only spatial light modulator. Our approach uses double phase encoding to generate phase-only holograms containing complex-valued input planes for a joint transform correlator (JTC) cryptosystem. This approach enables users to independently manipulate both the phase and amplitude of the cryptographic keys and objects, thereby significantly enhancing the versatility of the optical cryptosystem. We validate the capabilities of our proposed scheme by generating optimized random phase masks and using them to experimentally encrypt various grayscale and binary objects. The experimental complex modulation obtained with the system detailed in this work, in conjunction with optimized random phase masks, results in an enhancement in the quality of the decrypted objects during reconstruction. Both numerical simulations and experimental findings corroborate the effectiveness of our proposal.

Nonvolatile Phase-Only Transmissive Spatial Light Modulator with Electrical Addressability of Individual Pixels.

Active metasurfaces with tunable subwavelength-scale nanoscatterers are promising platforms for high-performance spatial light modulators (SLMs). Among the tuning methods, phase-change materials (PCMs) are attractive because of their nonvolatile, threshold-driven, and drastic optical modulation, rendering zero-static power, crosstalk immunity, and compact pixels. However, current electrically controlled PCM-based metasurfaces are limited to global amplitude modulation, which is insufficient for SLMs. Here, an individual-pixel addressable, transmissive metasurface is experimentally demonstrated using the low-loss PCM Sb2Se3 and doped silicon nanowire heaters. The nanowires simultaneously form a diatomic metasurface, supporting a high-quality-factor (∼406) quasi-bound-state-in-the-continuum mode. A global phase-only modulation of ∼0.25π (∼0.2π) in simulation (experiment) is achieved, showing ten times enhancement. A 2π phase shift is further obtained using a guided-mode resonance with enhanced light-Sb2Se3 interaction. Finally, individual-pixel addressability and SLM functionality are demonstrated through deterministic multilevel switching (ten levels) and tunable far-field beam shaping. Our work presents zero-static power transmissive phase-only SLMs, enabled by electrically controlled low-loss PCMs and individual meta-molecule addressable metasurfaces.

Weak measurement of the Goos–Hänchen shift for a Hermite–Gaussian laser beam

We report on an experimental investigation of the Goos–Hänchen (GH) optical beam shift in the vicinity of the critical angle of incidence at an air–glass interface using a weak value amplification (WVA) technique for two mutually orthogonal first order Hermite–Gaussian (HG) modes (HG10 and HG01) of a light beam at 633 nm generated by a phase-only reflective spatial light modulator. We have developed a mathematical approach to visualize the beam shaping due to the WVA scheme of beam shifts for the HG modes. The study reveals the angle of incidence dependency of the GH shift in the total internal reflection condition. For both modes, a detailed study of the horizontal and transverse beam shift values with varied post-selection angles is also reported. In addition, a comparison of the beam shift values for both of the selected modes with the fundamental mode (HG00) has been demonstrated. We found a significant enhancement (about two to three times) in the beam shifts for the first order HG10 and HG01 modes compared to the fundamental mode (HG00). Our results clearly demonstrate the advantages of the HG modes of the light beam-exploiting WVA technique and thus may contribute significantly to this field and open up important applications in photonic manipulation and future technologies.

Reference-free in situ rapid regional calibration of phase-only spatial light modulators.

Spatial light modulators (SLMs) have become an indispensable element in modern optics for their versatile performance in many applications. Among various types of SLMs, such as digital micromirror devices (DMD), liquid crystal-based phase-only spatial light modulators (LC-SLMs), and deformable mirrors (DM), LC-SLMs are often the method of choice due to their high efficiency, precise phase modulation, and abundant number of effective pixels. In general, for research grade applications, an additional SLM calibration step is required due to fabrication imperfection resulting in non-flat liquid crystal panels and varying phase responses over the SLM area. Here, we demonstrate a straightforward approach for reference-free orthogonal calibration of an arbitrary number of SLM subregions which only requires the same measurement time as global calibration. The proposed method requires minimal optical elements and can be applied to any optical setup as is. As a benchmark performance test, we achieved a 2.2-fold enhancement in correction efficiency for wavefront shaping through scattering media utilizing the calibrated 2160 subregions of the SLM, in comparison with a single global look-up table (LUT).

Incoherent digital holography with two polarization-sensitive phase-only spatial light modulators and reduced number of exposures.

I propose methods for reducing the number of exposures in incoherent digital holography with two polarization-sensitive phase-only spatial light modulators (IDH with TPP-SLMs). In IDH with TPP-SLMs, no polarization filters are required, and not only three-dimensional (3D), but polarization information is also obtained. However, seven exposures are required to conduct filter-free polarimetric incoherent holography. In this article, the optical designs and modified phase-shifting interferometry to reduce the number of recordings are described. IDH with TPP-SLMs has the potential for filter-free single-shot multidimensional incoherent holographic imaging.

Development of High-power Infrared Laser Capable Phase-only Spatial Light Modulator

Development of High-power Infrared Laser Capable Phase-only Spatial Light Modulator

Orientation-selective elliptic higher-order Poincaré sphere beam arrays

In this study, a new class of light-beam arrays, called orientation-selective elliptic higher-order Poincaré sphere (OS-EHOPS) beam arrays, is introduced as an extension of the scalar case reported in a previous study (Wang et al., 2020). For each beamlet of such beam arrays, the state of polarization represented by higher-/hybrid-order Poincaré spheres is spatially inhomogeneous, whereas the spatial profile takes on an elliptical shape with controllable orientation and ellipticity. The design procedure, which is rooted in multi-coordinate transformations, is comprehensively described and analyzed. Furthermore, we established an experimental setup involving a phase-only spatial light modulator that served as a Dammann grating and a common-path interferometer to effectively generate OS-EHOPS beam arrays. Two types of OS-EHOPS beam arrays, with hexagonal and double-ring-arranged structures, were synthesized to verify the feasibility of our method. Our design and optical system have potential applications in beam shaping and orientation-selective microfabrication.

Adaptive focal lengths in white light focusing Fresnel lenses enabled by reflective-type and phase-only spatial light modulator

Fresnel zone plates (FZPs) are widely used in integrated optical systems to meet new cutting-edge demands for photonic integration and device miniaturizing. However, their use in applications of cross-scale fabrication still faces several obstacles, such as low efficiency, fixed focal length, single wavelength, large size, and complicated fabrication. Here, we first examine a novel adaptive focal length in white light focusing by using reflective-type and phase-only spatial light modulator (RLC-SLM) based on a liquid crystal on silicon. The device achieves a maximum diffraction efficiency of approximately 38% at primary focal points of binary phase-type FZPs throughout the visible range (red, green, and blue wavelengths). The RLC-SLM focuses the light of the desired wavelength while other sources are defocused. White light focusing and color separation are demonstrated by sequentially and additively switching different FZPs. These recent advances show that optically tunable FRZs are promising potential candidates to enhance adaptive camera systems, microscopes, holograms, and portable and wearable devices, thereby opening up novel possibilities in optical communications and sensing.