Optical Information Processing Research Articles

Polarization and wavelength routers based on diffractive neural network

In the field of information processing, all-optical routers are significant for achieving high-speed, high-capacity signal processing and transmission. In this study, we developed three types of structurally simple and flexible routers using the deep diffractive neural network (D2NN), capable of routing incident light based on wavelength and polarization. First, we implemented a polarization router for routing two orthogonally polarized light beams. The second type is the wavelength router that can route light with wavelengths of 1550, 1300, and 1100 nm, demonstrating outstanding performance with insertion loss as low as 0.013 dB and an extinction ratio of up to 18.96 dB, while also maintaining excellent polarization preservation. The final router is the polarization-wavelength composite router, capable of routing six types of input light formed by pairwise combinations of three wavelengths (1550, 1300, and 1100 nm) and two orthogonal linearly polarized lights, thereby enhancing the information processing capability of the device. These devices feature compact structures, maintaining high contrast while exhibiting low loss and passive characteristics, making them suitable for integration into future optical components. This study introduces new avenues and methodologies to enhance performance and broaden the applications of future optical information processing systems.Graphical

Controllable optical effects in Landau-quantized graphene

This paper investigates the manipulation and control of optical properties in a Y-configured four-level Landau-Quantized Graphene system. Through a comprehensive analysis of the density matrix elements, we explore the influence of various system parameters, including control field intensities, detunings, and decay rates, on the optical response of the graphene sample. Our findings unveil compelling phenomena such as optical transparency, sub- and superluminal light propagation, and the emergence of multiple absorption peaks and transparency windows. Specifically, we examine the impact of decay rates on the absorption characteristics of graphene, revealing that higher decay rates diminish the effectiveness of Electromagnetically Induced Transparency (EIT) and slow light in the system. Furthermore, by systematically varying system parameters, we demonstrate the controllability of achieving either single or double EIT through manipulation of control field intensities and detunings. These results open promising avenues for applications in optical communications and quantum information processing, where precise control over graphene's optical properties is critical.

Superior AlGaN/GaN-Based Phototransistors and Arrays with Reconfigurable Triple-Mode Functionalities Enabled by Voltage-Programmed Two-DimensionalElectron Gas for High-Quality Imaging.

High-quality imaging units are indispensable in modern optoelectronic systems for accurate recognition and processing of optical information. To fulfill massive and complex imaging tasks in the digital age, devices with remarkable photoresponsive characteristics and versatile reconfigurable functions on a single-device platform are in demand but remain challenging to fabricate. Herein, an AlGaN/GaN-based double-heterostructure is reported, incorporated with a unique compositionally graded AlGaN structure to generate a channel of polarization-induced two-dimensional electron gas (2DEGs). Owing to the programmable feature of the 2DEGs by the combined gate and drain voltage inputs, with a particular capability of electron separation, collection and storage under different light illumination, the phototransistor shows reconfigurable multifunctional photoresponsive behaviors with superior characteristics. A self-powered mode with a responsivity over 100AW-1 and a photoconductive mode with a responsivity of ≈108AW-1 are achieved, with the ultimate demonstration of a 10×10 device array for imaging. More intriguingly, the device can be switched to photoelectric synapse mode, emulating synaptic functions to denoise the imaging process while prolonging the image storage ability. The demonstration of three-in-one operational characteristics in a single device offers a new path toward future integrated and multifunctional imaging units.

Deterministic quasi-continuous tuning of phase-change material integrated on a high-volume 300-mm silicon photonics platform

Programmable photonic integrated circuits (PICs) consisting of reconfigurable on-chip optical components have been creating new paradigms in various applications, such as integrated spectroscopy, multi-purpose microwave photonics, and optical information processing. Among many reconfiguration mechanisms, non-volatile chalcogenide phase-change materials (PCMs) exhibit a promising approach to the future very-large-scale programmable PICs, thanks to their zero static power and large optical index modulation, leading to extremely low energy consumption and ultra-compact footprints. However, the scalability of the current PCM-based programmable PICs is still limited since they are not directly off-the-shelf in commercial photonic foundries now. Here, we demonstrate a scalable platform harnessing the mature and reliable 300 mm silicon photonic fab, assisted by an in-house wide-bandgap PCM (Sb2S3) integration process. We show various non-volatile programmable devices, including micro-ring resonators, Mach-Zehnder interferometers and asymmetric directional couplers, with low loss (~0.0044 dB/µm), large phase shift (~0.012 π/µm) and high endurance (>5000 switching events with little performance degradation). Moreover, we showcase this platform’s capability of handling relatively complex structures such as multiple PIN diode heaters in devices, each independently controlling an Sb2S3 segment. By reliably setting the Sb2S3 segments to fully amorphous or crystalline state, we achieved deterministic multilevel operation. An asymmetric directional coupler with two unequal-length Sb2S3 segments showed the capability of four-level switching, beyond cross-and-bar binary states. We further showed unbalanced Mach-Zehnder interferometers with equal-length and unequal-length Sb2S3 segments, exhibiting reversible switching and a maximum of 5 (N+1,N=4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$N+1,N=4$$\\end{document}) and 8 (2N,N=3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${2}^{N},N=3$$\\end{document}) equally spaced operation levels, respectively. This work lays the foundation for future programmable very-large-scale PICs with deterministic programmability.

Comparative study of phase retrieval algorithms for surface shape measurement by optical profilometry

Recent advances in optical sensors and information processing technology have granted a rapid progress in three-dimensional (3D) optical metrology, enabling highly accurate 3D inspection of complex-shaped objects. However, the 3D object surface estimation requires a phase recovery from so-called intensity fringe patterns of the tested objects. In this work, we present a comparative study of three most highlighted phase retrieval methods (phase shifting, Fourier transform and wavelet transform) using single or multiple acquired fringe patterns. Moreover, the phase retrieval methods performance is tested on additive and multiplicative noise based degraded fringe patterns, giving some qualitative and quantitative conclusions. Some experimental data are processed using Fourier transform and wavelet transform based algorithms to confirm accuracy of these two phase retrieval techniques.

Tunable temporal dynamics of dipole response in graphene-wrapped core–shell nanoparticles

The investigation on the temporal dynamics of graphene-wrapped core–shell nanoparticles under the illumination of a Gaussian impulse have been carried out. By altering the graphene layers and the aspect ratio of the core–shell structure, we can adjust the resonant modes into typical cases in regime of terahertz. Accordingly, different scenarios for the temporal evolution are detected, which include two kinds of ultrafast oscillation with exponential decay tendency, pure exponential decay, and Gaussian shape, when the pulse duration of the incident pulse is much shorter than, similar to, and much longer than the localized surface plasmon lifetime. To one's interest, when the coupling between two resonant modes exists, one predicts the long-periodic oscillation, whose period is just the difference between the frequencies of the resonant modes. Hence, the intrinsic properties of the ultrafast oscillation can be hardly influenced by the input signals. Further quantitative calculation demonstrate that the periods of the ultrafast oscillations can be tuned by different physical mechanisms, which are, respectively, based on the self-interacting correction of a single resonance and the strong coupling between the resonant modes in frequency domain. Our results may be applicable in the fields of optical sensors, optical information processing, and other nanophotonic devices.

Twist-Angle-Controlled Nonlinear Circular Dichroism on Gold-Crystal Hybrid Metasurfaces.

Optical chirality, which plays important roles in liquid crystal display and biological and chemical detection, has been attracting scientists' attention due to its potential applications in optical information processing. Usually, the chiral optical response of natural molecules is very weak. However, the emergence of metasurfaces offers a promising solution to solve this issue. By judiciously designing the geometry of meta-atoms, we have realized strong optical circular dichroism (CD) in both linear and nonlinear optical regimes. However, tuning of the CD with a metasurface remains challenging. Here, we propose the twist-angle-controlled nonlinear CD effect by using the second-harmonic generation process on a gold-crystal hybrid metasurface. The CD effect of the second-harmonic waves can be tuned well by controlling the twist angle between the two constituent materials. The proposed hybrid metasurface may open new avenues for developing ultracompact and multifunctional nonlinear optical devices.

Multiple optomechanically induced transparency generated slow light in an array of optomechanical system

We present an array of optomechanical systems which consist of an optical cavity and three nanomechanical resonators. Introducing Jaynes-Cumming (J-C) coupling in the nearest neighbor resonator allows for the formation of optomechanical systems with arrays of N nanomechanical resonators. Using a strong pump field and a weak probe field to drive the optical cavity simultaneously, we investigated the coherent optical response and the probe transmission spectrum manifested as multiple optomechanically induced transparency. We illustrate the impact of probe-cavity detuning, J-C coupling strength, and the number of nanomechanical resonators on the transparent window. In particular, we analyze nanomechanical resonators and find that increasing their number results in multiple transparent windows and slow light at different frequencies. We also find that the slow light effect can be enhanced by increasing the number of nanomechanical resonators with odd numbers at resonance. These findings imply that the arrays of optomechanical system can be used for multichannel optical communications and multichannel quantum information processing.

Dual perfect vectorial vortex beam generation with a single spin-multiplexed metasurface

Perfect optical vortex beams (POVBs) carrying orbital angular momentum (OAM) possess annular intensity profiles that are independent of the topological charge. Unlike POVBs, perfect vectorial vortex beams (PVVBs) not only carry orbital angular momentum but also exhibit spin angular momentum (SAM). By incorporating a Dammann vortex grating (DVG) on an all-dielectric metasurface, we demonstrate an approach to create a pair of PVVBs on a hybrid-order Poincaré sphere. Benefiting flexible phase modulation, by engineering the DVG and changing the input-beam state we are able to freely tailor the topological OAM and polarization eigenstates of the output PVVBs. This work demonstrates a versatile flat-optics platform for high-quality PVVB generation and may pave the way for applications in optical communication and quantum information processing.

Controllable storage and retrieval of temporal vector optical solitons in semiconductor double quantum dots by inter-dot tunneling coupling effect

In this study, we analyzed the storage and retrieval of vector optical fields in semiconductor double quantum dots with interdot tunneling coupling. Our findings indicate that temporal vector optical solitons (TVOS) can be effectively stored and retrieved through this coupling. Furthermore, we conducted numerical simulations to investigate the interaction between TVOS. Our results suggest that the interaction between in-phase solitons is attractive, while the interaction between anti-phase solitons is repulsive. Additionally, we found that TVOS remain stable even after a collision, which is significant for the processing of optical information in solid quantum materials. Overall, our study sheds light on the potential of interdot tunneling coupling for storing and retrieving vector optical fields in semiconductor double quantum dots. Additionally, our findings regarding the interaction between TVOS can inform future research in the field of optical information processing.

Enhanced superluminal pulse propagation via chiral quantum dot system

The control and enhancement of superluminal pulse propagation via a chiral quantum-dots (QDs) system is presented in this article. The proposed system is a double chiral QDs four-level system, that gets excited by pump and probe fields, along with inter-dot tunneling strength. It is observed that the strength of inter-dot tunneling strongly influences the left-circular polarized (LCP) and right-circular polarized (RCP) superluminal pulse propagation. By appropriately modulating this strength, optimal coherence within the system can be achieved, thereby contributing to enhanced superluminal pulse propagation. We have examined the characteristics of RCP and LCP beams and observed the large negative group index and advance time. The observation of a large negative group index and advanced time shows strong evidence for enhanced superluminal pulse propagation in the proposed chiral QDs system. This study has important applications in the field of optical information processing, temporal cloaking, quantum communication, and improving computer chip speed.

MoS2/ZnO-heterostructured optoelectronic synapse for multiwavelength optical information-based sensing, memory, and processing

The rapid development of artificial intelligence and humanoid robots requires hardware-level revolution of synapses-based bionic vision system. However, current optoelectronic synapses featuring multiwavelength sensing and multifunctional processing necessitate intricate integrations of multi-materials and floating gate configurations, which induces complex fabrication process and limited integration density. Here, we propose a novel two-terminal optoelectronic synaptic device based on MoS2/ZnO heterostructure which integrates sense and memory functions and realizes multifunctional optical information processing while circumvents the need of complex configurations. By simultaneously exploiting the photo-adsorption oxygen dissociation property of ZnO and the persistent photoconductivity effect of MoS2, the device demonstrates synaptic capability of four-color perception with a single synaptic event consuming a mere 2.55×10−9 J. Different from the traditional power-density sensitive nociceptor, for the first time photon energy-sensitive nociceptors is developed, which can mimic the process of UV irradiation to the retina leading to fear of visible light. Diverse information processing ability, such as photonic information encryption, associative learning, and logic calculation, was demonstrated in a single device, indicating a practical strategy for facile design for future high integration intensity neuromorphic devices.

On-chip silicon photonic nanohole metamaterials enabled high-density waveguide arrays

High-density silicon waveguide arrays manufactured on a complementary metal-oxide-semiconductor (CMOS)-foundry platform hold great promise for optical information processing and photonic integration. However, evanescent waves arising from nanoscale confinement would cause significant optical crosstalk in waveguide arrays, which remains a vital issue in various applications. Here, by utilizing silicon photonic nanohole metamaterials, we propose a scheme to greatly suppress the crosstalk in the devices and then demonstrate ultra-compact low-crosstalk waveguide arrays. For a 100-µm-long waveguide array at a half-wavelength pitch, low crosstalk of −19 dB can be obtained in a wide range of wavelengths (1500 nm–1580 nm). In the experimental demonstrations, our approach exhibits the ability to suppress the crosstalk over a broad bandwidth without substantially increasing the propagation loss as well as the promising design flexibility, which shall pave the way for metamaterials enabled high-density waveguide arrays.

Soliton transformation in a cold Rydberg atomic system

This work presents a method for achieving soliton transformation in a cold Rydberg atomic system to enable the realization of diverse optical potentials. Our investigation demonstrates that this system can generate various solitons, including Gaussian, elliptical, ring, and necklace structures, based on different optical lattice potentials. Additionally, stable transitions from Gaussian profile to three other profiles can be achieved either abruptly or gradually by adjusting the centers and modulation depths of potentials along the direction of light propagation. These findings highlight the versatility of this system for generating and manipulating solitons. The ability to control soliton transformation offers prospects for various applications, including all-optical switching, optical information processing, and other areas.

Logical Platforms for Mobile Application in Decision Support Systems Based on Color Information Processing

Logical Platforms for Mobile Application in Decision Support Systems Based on Color Information Processing

Longitudinal manipulation of local nonseparability in vector beams.

The inherent nonseparability of vector beams presents a unique opportunity to explore novel optical functionalities, expanding new degrees of freedom for optical information processing. In this Letter, we introduce a novel, to the best of our knowledge, method for tailoring the local nonseparability along the propagation axis of vector beams. Employing higher-order Bessel vector beams, the longitudinal control over the local nonseparability is achieved through targeted amplitude modulation of constituent orthogonal polarization components within the main ring region. Experimental demonstrations of diverse longitudinal nonseparability profiles corroborate the efficacy and versatility of our approach, opening avenues for further exploration of the nonseparability manipulation in vector beams.

Superluminal propagation of surface plasmon polaritons via hybrid chiral quantum dots system

We present a novel methodology for enhancing superluminal surface plasmon polaritons (SPPs) propagations within a hybrid nanostructure configuration consisting of gold (Au) metal and chiral quantum dots (CQDs) medium. The arrangement of CQDs and metal hybrid nanostructures enables the production of SPPs when exposed to incident light. The resonances of SPPs within a hybrid nanostructure are determined through analytical calculations using Maxwell’s equations under specified boundary conditions, while the dynamics of the CQDs system are calculated using the density matrix approach. It is demonstrated that the propagation of SPPs is significantly influenced by both right-circularly polarized (RCP) and left-circularly polarized (LCP) SPPs. Additionally, we investigate the enhancement of superluminal SPPs propagation by varying the electron tunneling strength and the intensity of the control field within the hybrid system. The characteristics of RCP and LCP SPPs have been investigated, indicating a large negative group index and advancement in time. The observation of a large negative group index and advancement in time provides strong evidence for enhanced superluminal SPPs propagation within the proposed hybrid nanostructure. The results have potential applications in the fields of optical information processing, temporal cloaking, quantum communication, and the advancement of computer chip speed.

Spatiotemporal modulation of ultrafast plasmonic vortices with spin–orbit coupling

The vortex field of surface plasmon polariton with orbital angular momentum (OAM), called plasmonic vortex, has played an important role in various research fields. However, the spatiotemporal properties of plasmonic vortex pulses excited by ultrafast laser, especially the dynamics of spin‒orbit coupling in the ultrafast plasmonic vortex field, have yet to be investigated deeply. Here, we study the spatiotemporal modulation of ultrafast plasmonic vortices with spin‒orbit coupling, using both analytical and simulation methods. The ultrafast plasmonic vortices are excited by a ring-shaped plasmonic lens, with an incident light composed of two time-delayed femtosecond sub-pulses carrying the same OAM but orthogonal circular polarizations. The dynamics of time-varying electric field, energy flow and angular momentum distributions of the plasmonic vortices are demonstrated, revealing details of the spin‒orbit coupling in spatiotemporal domain, such as the merging of multiple phase singularities with energy flow loops, and the variation of spin/orbital angular momentum per photon over time. This work could deepen the understanding of spin‒orbit coupling in plasmonic field and provide new ideas for ultrafast on-chip optical information processing.

Inelastic two-wave mixing induced high-efficiency transfer of optical vortices

A scheme for high-efficiency transfer of optical vortices is proposed by an inelastic two-wave mixing (ITWM) process in an inverted-Y four-level atomic medium, which is originally prepared in a coherent superposition of two ground states. The orbital angular momentum (OAM) information in the incident vortex probe field can be transferred to the generated signal field through the ITWM process. Choosing reasonable experimentally realizable parameters, we find that the presence of the off-resonance control field can greatly improve the conversion efficiency of optical vortices, rather than in the absence of a control field. This is caused by the broken of the destructive interference between two one-photon excitation pathways. Furthermore, we also extend our model to an inelastic multi-wave mixing process and demonstrate that the transfer efficiency between multiple optical vortices strongly depends on the superposition of the ground states. Finally, we explore the composite vortex beam generated by collinear superposition of the incident vortex probe and signal fields. It is obvious that the intensity and phase profiles of the composite vortex can be effectively controlled via adjusting the intensity of the control field. Potential applications of our scheme may exist in OAM-based optical communications and optical information processing.

Orbital-angular-momentum-dependent speckles for spatial mode sorting and demultiplexing

Characterizing the orbital-angular-momentum (OAM) modes is critically important for OAM-encoded data transfer. However, traditional characterizing approaches rely on either complex and precise experimental configurations or complicated prior information processing. In these scenarios, the correlation features of OAM-dependent speckles from the scattering effect have received little attention. Here, we investigate the cross-correlation characteristics of the OAM speckles resulting from a scattering medium and propose an appealing alternative for spatial mode sorting and demultiplexing based on the OAM-dependent speckles. We demonstrate theoretically and experimentally that the cross-correlation operation between two different OAM-dependent speckles can uniformly derive an annulus pattern, whose dimension is determined by the absolute topological charge difference value between the two corresponding OAM modes. Based on this mechanism, the original coherent OAM modes can be easily sorted by implementing the cross-correlation operation between incoherently measured OAM-dependent speckles. To fully capitalize on the orthogonal feature of the OAM-dependent speckles, we also construct OAM mode demultiplexing experiments using a ground glass diffuser, where both 8-bit grayscale and 24-bit RGB OAM-encoded data demultiplexing are successfully demonstrated with superior error rates. Results show that the OAM-dependent speckles, previously treated as a nuisance for practical applications, can be surprisingly utilized as a competitive candidate for OAM mode sorting and demultiplexing, thus opening new directions in optical communication and information processing.