Applications In Optical Information Processing Research Articles

Coherent control of dressing interaction of sequential-doubly-dressed four-wave mixing

Abstract We investigate the coherent control of dressing interaction in four-wave mixing (FWM) in a Y-type four-level atomic system based on the dressed states theory. We study the density matrix equation acted by two dressing fields simultaneously governing FWM signal intensity and the eigenvalues under the dressed state formalism. It is shown that the peak position and intensity of Autler–Townes splitting both originate from the dressing interaction as the detuning of the probe field is scanned. Moreover, it is observed that the interaction could be controlled by the dressing fields. Such flexibly controlled nonlinear signal has potential applications in optical communication and quantum information processing.

Stabilizing and Guiding Rogue Waves in a Cold Atomic Gas

AbstractRogue waves (RWs) are mysterious nonlinear waves and have attracted much attention in recent years. However, they are usually unstable during propagation. Here, a scheme for stabilizing and guiding optical RWs in a cold atomic gas working under the condition of electromagnetically induced transparency is presented. It is shown that an external potential for probe laser field can be created by using an assisting laser field. If the assisting laser field has the form of Gaussian beam, the instability of the RWs can be largely suppressed. It is also shown that the RWs can be stabilized and guided to propagate along curved trajectories if the assisting laser field has the form of Airy beam. The results reported here contribute to the effort for stabilizing and manipulating RWs, which may have potential applications in optical transmission and information processing.

Dissimilar soliton molecule formed by dissipative pulses in a single-mode mode-locked fiber laser

Soliton molecules, or also known as optical bound states, are the most representative example of solitons’ particle nature and have given birth to diverse light-matter analogies. Despite detailed research on regular bound states, the soliton molecule synthesis of dissimilar pulses has rarely been reported. Here, soliton molecules formed by dissimilar dissipative solitons are demonstrated in a single-mode mode-locked fiber laser, with an in-depth analysis of their evolution dynamics. This novel bound state features pulse trapping between two ultrafast vector pulses with distinct pulse properties including energy, duration, and chirp, leading to unique temporal and spectral profiles. This laser provides an optimal platform for studying complex interactions between different types of dissipative solitons. The findings here can provide new degrees of freedom for the generation of optical soliton molecules and can fuel applications in optical information processing, metrology, and spectroscopy.

Characteristics study of a dual-wavelength polarization filter based on gold-filled square lattice photonic crystal fiber

This study proposes a polarization filter based on gold-filled photonic crystal fiber (PCF) with a square lattice structure. Utilizing the finite element method (FEM), the filtering characteristics of the model were numerically simulated. The dispersion relation and loss characteristics of this structure were analyzed, and the optimal structural parameters were obtained through structural adjustments. Furthermore, the performance of the filter was evaluated under a 2% variation in manufacturing tolerances for gold film thickness (), air hole spacing (), and air hole diameters () and (). Results indicated that at the 1310 nm and 1550 nm communication windows, the confinement losses of the filter were 1354.6 dB/cm and 869.04 dB/cm, respectively, while the losses for the -polarization were merely 16.97 dB/cm and 0.98 dB/cm. When the filter length was set to 0.5 mm, the maximum extinction ratios (ERs) for the two windows reached 588.2 dB and 370.6 dB, and the filter bandwidth extended to 640 nm. Moreover, the characteristics of the filter under manufacturing tolerances were computed, revealing that the filter’s performance remained stable and feasible despite manufacturing errors. The proposed rectangular gold-coated PCF is anticipated to have broad applications in optical fiber communication and optical information processing.

Realization of spinful metaphotonic stokes skyrmions

Abstract Topologically protected skyrmion textures of light have garnered significant attention due to their potential applications in next-generation high-density data storage and logic devices. However, achieving compact and tunable on-chip skyrmion modes remains a formidable challenge. In this work, we present a novel approach empowered by birefringent metasurfaces to generate and manipulate spin-multiplexed photonic skyrmion textures. By encoding independent phase profiles onto orthogonal spin states, we observe the emergence of anti-skyrmions and skyrmioniums via Stokes parameter measurements, elucidating their distinct topological characteristics. This spin-multiplexed metasurface platform not only facilitates high-dimensional multiplexing but also enables the miniaturization of topological quasi-particles, offering promising prospects for applications in optical memory, information processing, and communications.

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.

Nonreciprocal Pancharatnam-Berry metasurface for unidirectional wavefront manipulations

Optical metasurfaces employing the Pancharatnam-Berry (PB) geometric phase, called PB metasurfaces, have been extensively applied to realize spin-dependent light manipulations. However, the properties of conventional PB metasurfaces are intrinsically limited by the Lorentz reciprocity. Breaking reciprocity can give rise to new properties and phenomena unavailable in conventional reciprocal systems. Here, we propose a mechanism to realize nonreciprocal PB metasurfaces of subwavelength thickness by using the Faraday magneto-optical (FMO) effect of yttrium iron garnet (YIG) material in synergy with the PB geometric phase of spatially rotating meta-atoms. Using full-wave numerical simulations and multipole analysis, we show that the metasurface composed of dielectric cylinders and a thin YIG layer can achieve high isolation of circularly polarized lights, attributed to the enhancement of the magneto-optical effect by the resonant Mie modes and Fabry-Pérot (FP) cavity mode. In addition, the metasurface can enable unidirectional wavefront manipulations of circularly polarized lights, including nonreciprocal beam steering and nonreciprocal beam focusing. The results contribute to the understanding of the interplay between nonreciprocity and geometric phase in light manipulations and can find applications in optical communications, optical sensing, and quantum information processing.

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.

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.

Topological protection of dual-polarization biphoton states in photonic crystals

Polarization control is a major issue in topological quantum optics that limits reliable generation and transmission of quantum states. This study presents what we believe to be a novel topological photonic crystal design that provides topological protection for biphoton pairs for both TE and TM polarization. By well-designed cell configurations within the lattice, two topological boundaries emerge that can accommodate TM and TE modes at the same time. By adjusting the dispersion curves, we can further design nonlinear four-wave mixing processes within the topological photonic crystals and provide theoretical explanations for the entanglement of the dual-polarization biphoton states. Numerical results confirm the robust transport of entangled photon pairs, even when subjected to sharp bending. Moreover, combining the dual-polarization topological photonic crystal with a polarization beam splitter enables the preparation of polarization-encoded maximally entangled states. Our work exhibits significant potential for applications in robust optical quantum information processing and quantum secure communication.

All-optical ultrafast polarization switching with nonlinear plasmonic metasurfaces.

Optical switching has important applications in optical information processing, optical computing, and optical communications. The long-term pursuit of optical switch is to achieve short switching time and large modulation depth. Among various mechanisms, all-optical switching based on Kerr effect represents a promising solution. However, it is usually difficult to compromise both switching time and modulation depth of a Kerr-type optical switch. To circumvent this constraint, symmetry selective polarization switching via second-harmonic generation (SHG) in nonlinear crystals has been attracting scientists' attention. Here, we demonstrate SHG-based all-optical ultrafast polarization switching by using geometric phase controlled nonlinear plasmonic metasurfaces. A switching time of hundreds of femtoseconds and a modulation depth of 97% were experimentally demonstrated. The function of dual-channel all-optical switching was also demonstrated on a metasurface, which consists of spatially variant meta-atoms. The nonlinear metasurface proposed here represents an important platform for developing all-optical ultrafast switches and would benefit the area of optical information processing.

Disorder enhanced relative intrinsic detection efficiency in NbTiN superconducting nanowire single photon detectors at high temperature

The intrinsic detection performance of superconducting nanowire single photon detectors (SNSPDs) is highly dependent on the superconducting properties of underlying thin films. This report outlines the enhancement of detection performance for single telecom wavelength photons in disordered NbTiN SNSPD at 4.2 K. By increasing the nitrogen content and deposition pressure, the NbTiN films show suppression in critical temperature and an increase in sheet resistance. Notably, the resulting SNSPDs display a broader saturation plateau at 2.2 K, leading to superior detection performance at 4.2 K. With the disordered 7-nm-thick NbTiN films, we fabricated SNSPDs with system detection efficiency up to 83% for 1550 nm photons at 4.2 K. Moreover, these devices also show saturated intrinsic detection efficiency for 2000 nm photons. With the features outlined, the devices can be integrated into the idle 4.2 K stage of the dilution refrigerator for applications in optical quantum information processing or utilize for detecting laser radar signals in airborne platforms.

Tightly focused optical skyrmions and merons formed by electric-field vectors with prescribed characteristics

Abstract Optical skyrmions, which are topological quasi-particles with nontrivial electromagnetic textures, have garnered escalating research interest recently for their potential in diverse applications. In this paper, we present a method for generating tightly focused optical skyrmion and meron topologies formed by electric-field vectors under 4π-focusing system, where both the topology types (including Néel-, Bloch-, intermediate- and anti-skyrmion/meron) and the normal direction of the two-dimensional topology projection plane can be tailored at will. By utilizing time-reversal techniques, we analytically derive the radiation pattern of a multiple concentric-ring array of dipoles (MCAD) to obtain the required illumination fields on the pupil planes of the two high numerical aperture lenses. The Deby vector diffraction integral theory is employed to calculate the corresponding tightly focused field, and their topology characteristics are quantitatively evaluated by the electric-field vector distribution. The results demonstrate that arbitrary electric-field based skyrmion and meron can be conveniently generated by adjusting the oscillation direction of each dipole in the MCAD and the normal direction of the dipole array. The generated optical topologies with fully controllable degrees of freedom provide potential applications in optical information processing, transmission, and storage.

Enhanced negative refraction in one- and two-dimensional chiral atomic lattices

We consider a physical scheme for the realization of optical lattices that have negative refracting under certain conditions. The lattice is formed by clusters of five-level closed-loop chiral atoms assumed to have a Gaussian density distribution in dipole traps along one or two dimensions. With a suitable combination of strong standing wave control fields, spatial symmetry of atoms is achieved. Besides, the dispersion properties of an atomic lattice can be modified conveniently by adjusting various parameters related to the atoms or the lattice. We show that negative-like refraction is not specific to the atoms themselves, but also emerges due to the periodicity of the lattice. We further reveal that the refraction is negative over specific regions on the lattice and strongly depends on the number of atoms trapped along a particular direction. Our model is effectively controllable remotely and may have applications in negative refraction devices and optical information processing.

Giant nonlocal Kerr nonlinearity and polaritonic solitons in a Rydberg-dressed Bose-Einstein condensate.

We present a scheme to generate nonlocal optical Kerr nonlinearity and polaritonic solitons via matter-wave superradiance in a Rydberg-dressed Bose-Einstein condensate (BEC). We show that the polariton spectrum of the scattered field generated by the superradiance is changed significantly due to the existence of the long-range Rydberg-Rydberg interaction between atoms, i.e. it has a roton-maxon form; moreover, the BEC structure factor displays a strong dependence on the Rydberg-dressing, which can be tuned in a controllable way. We also show that such a Rydberg-dressed BEC system can support a giant nonlocal optical Kerr nonlinearity, and hence allow the formation and stable propagation of polaritonic solitons, which have ultraslow propagation velocity and ultralow generation power. The results reported here are useful to understand the unique properties of Rydberg-dressing in BECs and have potential applications in optical information processing and transmission.

High-frame-rate reconfigurable diffractive neural network based on superpixels.

The existing implementations of reconfigurable diffractive neural networks rely on both a liquid-crystal spatial light modulator and a digital micromirror device, which results in complexity in the alignment of the optical system and a constrained computational speed. Here, we propose a superpixel diffractive neural network that leverages solely a digital micromirror device to control the neuron bias and connection. This approach considerably simplifies the optical system and achieves a computational speed of 326 Hz per neural layer. We validate our method through experiments in digit classification, achieving an accuracy of 82.6%, and action recognition, attaining a perfect accuracy of 100%. Our findings demonstrate the effectiveness of the superpixel diffractive neural network in simplifying the optical system and enhancing computational speed, opening up new possibilities for real-time optical information processing applications.

Tunable sum-frequency generation in modal phase-matched thin film lithium niobate rib waveguides.

In this work, we report a highly efficient and tunable on-chip sum-frequency generation (SFG) on a thin-film lithium niobate platform via modal phase matching (e + e→e). It provides on-chip SFG a solution with both high efficiency and poling-free by using the highest nonlinear coefficient d33 instead of d31. The on-chip conversion efficiency of SFG is approximately 2143%W-1 with a full width at half maximum (FWHM) of 4.4 nm in a 3-mm-long waveguide. It can find applications in chip-scale quantum optical information processing and thin-film lithium niobate based optical nonreciprocity devices.

Coherent transfer of optical vortices via backward four-wave mixing in a double- Λ atomic system

We propose and analyze an efficient scheme for the coherent transfer of optical vortices in a cold atomic ensemble with four-level double-$\mathrm{\ensuremath{\Lambda}}$ configuration. The orbital angular-momentum (OAM) information can be transferred from the incident vortex fields to the generated backward signal field via resonant backward four-wave mixing (FWM). Considering the single vortex probe field initially acting on one transition of the atomic ensemble and using experimentally achievable parameters, we identify the conditions under which the resonant backward FWM allows us to greatly improve the conversion efficiency of optical vortices beyond what is achievable in the resonant forward OAM transfers. It is found that the complete energy conversion of optical vortices originates from the perfect competition between linear absorption and parametric gain. We also demonstrate that the phase mismatching would be detrimental to the high-efficiency transfer of optical vortices. Furthermore, we show that the generated backward signal field develops a new pure or mixing OAM state when the control field is also a vortex beam. Finally, we investigate the composite vortex beam generated by collinear superposition of the incident vortex probe and signal fields, which can controlled via adjusting the intensity of the control field. Our scheme may have potential applications in OAM-based optical communication and optical information processing.

Multidimensional optical solitons and their manipulation in a cold atomic gas with a parity-time-symmetric optical Bessel potential

We propose a scheme to realize an optical Bessel potential with parity-time ($\mathcal{P}T$) symmetry and investigate the existence, propagation, and manipulation of multidimensional optical solitons through the interplay among diffraction, Kerr nonlinearity, and potential confinement in a cold atomic gas under the condition of electromagnetically induced transparency (EIT). We show that the system supports not only two-dimensional stationary optical solitons but also rotary ones; the stability of such solitons can be actively controlled by the gain-loss component (imaginary part), while the rotary motions can be tuned by the refractive-index component (real part) of the $\mathcal{P}T$-symmetric potential. Moreover, we demonstrate that the system allows the existence of stable three-dimensional spatiotemporal optical solitons, i.e., optical bullets, which have ultraslow propagation velocity and display helicoidal motions with controllable propagation trajectories. Due to the Kerr nonlinearity enhanced by the EIT effect, extremely low power is needed to create these multidimensional optical solitons. The results reported here are useful not only for the generation and manipulation of high-dimensional solitons via $\mathcal{P}T$-symmetric potentials, but also for promising applications in optical information processing and transmission.

Controllable plasmonic vortex sequence with on-chip discrete-slit-based metalens

Like free-space vortex beams, surface plasmon polaritons can carry orbital angular momentum to form plasmonic vortices (PVs). Recently, research interest in PV fundamentals and applications has increased. However, generating and manipulating the topological charges of PVs over wide ranges using on-chip devices remains challenging. Here, we propose an on-chip plasmonic metalens structure to generate tunable PV sequence with controllable topological charges at discrete wavelengths. When compared with conventional spiral-slit structures, the designed metalens has additional structural parameters that bring more degrees of freedom to control the range and interval of the topological charge distribution of the PV sequence. Analytical and simulation methods are used to verify the metalens’ functionality. It is proved that the topological charges of the generated PV sequence are symmetrically distributed about the fundamental mode (l = 0), which cannot be realized by a traditional Archimedean helix. In addition, the normalized powers of the PV sequence are all above 0.8, showing that the designed metalens structure has potential for use as an on-chip optical vortex comb device. This work has potential applications in on-chip optical information processing, integrated optical communications, and optical tweezers.