Quantum Optical Devices Research Articles

Tunable dual-band unidirectional reflectionlessness in a one-dimensional waveguide-cavity optomechanical system

Tunable dual-band unidirectional reflectionless phenomena in a one-dimensional waveguide coupled with a cavity optomechanical system driven by external driving fields were investigated. The results indicated that dual-band unidirectional reflectionlessnesses can be obtained by appropriately adjusting the strengths of the external driving fields, phase shift between the two optical cavities, coupling strengths of the optical cavities to the waveguide and decay rates of the two cavities and mechanical resonators. Moreover their peaks can be tuned by changing both the effective optomechanical coupling strengths and phase shift, which can achieve unidirectional reflectionlessness by adjusting the external driving fields when the phase shift is difficult to adjust precisely. This work provides a well theoretical reference for the research and development of quantum optical devices such as optical diodes, switches, and isolators.

Single Quantum Emitters with Arbitrarily Polarized Dipole Moments Under Ambient Conditions

AbstractThe ability to control the spin of dipole moments of single quantum emitters is crucial for spin‐based quantum technologies. However, realizing circularly polarized (CP) dipole moments under ambient conditions has remained an outstanding challenge. Here, this work proposes an optical interface capable of converting a single quantum emitter into a deep‐subwavelength super‐emitter with an arbitrarily polarized dipole moment, including the long‐sought CP dipole. It is accomplished by coupling the emitter to dual dipolar modes of a plasmonic nanoantenna with precisely controlled amplitudes and phases, resulting in a coherent superposition of the modes that generates the desired dipole polarization. Meanwhile, the dipole moment amplitude is enhanced by over an order of magnitude. The CP super‐emitter behaves analogously to an ideal CP point dipole emitter, exhibiting characteristic spiraling field pattern and spin‐directional coupling to waveguide modes due to spin‐orbit locking. The results overcome a long‐standing challenge in constructing spin‐controlled quantum emitters under ambient conditions, opening new possibilities for tailoring light–matter interactions and designing novel quantum optical devices.

Thermally stable photoluminescence centers at 1240 nm in silicon obtained by irradiation of the SiO2/Si system

The study of light-emitting defects in silicon created by ion implantation has gained renewed interest with the development of quantum optical devices. Improving techniques for creating and optimizing these defects remains a major focus. This work presents a comprehensive analysis of a photoluminescence line at a wavelength of 1240 nm (1 eV) caused by defects arising from the ion irradiation of the SiO2/Si system and subsequent thermal annealing. It is assumed that this emission is due to the formation of defect complexes WM with trigonal symmetry similar to the well-known W-centers. A distinctive feature of these defects is their thermal resistance up to temperatures of 800 °C and less pronounced temperature quenching compared to the W-line. The difference in the properties of these defect centers and W-centers can be explained by their different defect environments, resulting from the larger spatial separation between vacancies and interstitial atoms diffusing from the irradiated layer. This, in turn, is associated with the difference in the distribution of primary radiation defects during irradiation of the SiO2/Si system and silicon not covered with a SiO2 film. The patterns of changes in the WM line depending on various factors, such as the thickness of the SiO2 film, type of conductivity and impurity concentration in the original silicon, irradiation parameters, and annealing regimes, is studied and explained in detail. These findings demonstrate the benefits of this new approach when compared to previous methods.

Modulation of Second-Order Sideband Efficiency in an Atom-Assisted Optomechanical System

We propose an efficient scheme to enhance the generation of optical second-order sidebands (OSSs) in an atom-assisted optomechanical system. The cavity field is coupled with a strong driving field and a weak probe field, and a control field is applied to the atom. We use the steady-state method to analyze the nonlinear interaction in the system, which is different from the traditional linear analysis method. The existence of an auxiliary three-level atom driven by the control field significantly enhances the generation of an OSS. It is found that the efficiency of the OSS can be effectively modulated by adjusting the Rabi frequency of the control field, optomechanical cooperativity and atomic coupling strength. Our scheme provides a promising solution for controlling light propagation and has potential application in quantum optical devices and quantum information networks.

Ultra‐Low‐Power Tunable Topological Photonic Filter on Hybrid Integrated Lithium Tantalite and Silicon Platform

AbstractIntegrated tunable optical filters are essential components in photonic signal processors, telecom systems, sensors, and quantum optical devices. Two of the most important features of a tunable filter are its dimensions and power consumption. Herein, the design and experimental validation of an on‐chip optical filter composed of a 1D topological photonic crystal cavity based on a hybrid integrated lithium tantalite‐silicon platform is presented. The strong optical confinement of the boundary state allows the fabrication of a tunable filter with an ultra‐compact size of 1.14 × 75 µm2 is demonstrated. Moreover, lithium tantalite has excellent electro‐optic properties and enables ultra‐low‐power wavelength tuning of the topological boundary state. The measured power consumption and tuning efficiency of the device are 0.0218 nW pm−1 and 6.64 pm V−1, respectively. The anisotropy of thin‐film lithium tantalite is verified by evaluating its tuning efficiency at different optical angles. The device can compensate for thermally induced refractive index changes ≈20 °C, exhibiting operational robustness. High‐speed transmission experiments confirm the stability of the developed tunable filter. This optical filter implements a topological structure with a compact size and can potentially be applied in on‐chip quantum optics, nonlinear optics, and optical sensing.

Frequency-tunable single-photon router based on a microresonator containing a driven three-level emitter

We propose a frequency-tunable router of single photons with high routing efficiency, which is constructed by two waveguides mediately linked by a single-mode whispering gallery resonator with a driven three-level emitter. Quantum routing probability in the output port is obtained via the real-space Hamiltonian. By adjusting the resonator–emitter coupling and the drive, the desired continuous central frequencies for the resonance peaks of routing photons can be manipulated nearly linearly, with the assistance of Rabi splitting effect and optical Stark shift. The proposed routing system may provide potential applications in designing other frequency-modulation quantum optical devices, such as multiplexers, filters, and so on.

Coherent equalization of linear quantum systems

This paper introduces a H∞-like methodology of coherent filtering for equalization of passive linear quantum systems to help mitigate degrading effects of quantum communication channels. For such systems, which include a wide range of linear quantum optical devices and signals, we seek to find a near optimal equalizing filter which is itself a passive quantum system. The problem amounts to solving an optimization problem subject to constraints dictated by the requirement for the equalizer to be physically realizable. By formulating these constraints in the frequency domain, we show that the problem admits a convex H∞-like formulation. This allows us to derive a set of suboptimal coherent equalizers using J-spectral factorization. An additional semidefinite relaxation combined with the Nevanlinna–Pick interpolation is shown to lead to a tractable algorithm for the design of a near optimal coherent equalizer.

Room-Temperature Strong Coupling of Few-Exciton in a Monolayer WS2 with Plasmon and Dispersion Deviation.

Engineering room-temperature strong coupling of few-exciton in transition-metal dichalcogenides (TMDCs) with plasmons promises to construct compact and high-performance quantum optical devices. But it remains unimplemented due to their in-plane excitons. Here, we demonstrate the strong coupling of few-exciton within 10 in monolayer WS2 with the plasmonic mode with a large tangential component of the electric field tightly trapped around the sharp corners of an Au@Ag nanocuboid, the fewest number of excitons observed in the TMDC family so far. Furthermore, we for the first time report a significant deviation with a relative difference of up to 100.6% between the spectrum and eigenlevel splitting dispersions, which increases with decreasing coupling strength. It is also shown that the coupling strength obtained by the conventional concept of both being equal to the measured spectrum splitting is markedly overestimated. Our work enriches the understanding of strong light-matter interactions at room temperature.

Multiplicative topological semimetals

Exhaustive study of topological semimetal (TSM) phases of matter in equilibriated electonic systems and myriad extensions has built upon the foundations laid by earlier introduction and study of Weyl semimetals, with broad applications in topologically protected quantum computing, spintronics, and optical devices. We extend recent introduction of multiplicative topological phases to find previously overlooked TSM phases of electronic systems in equilibrium, with minimal symmetry protection. We show these multiplicative TSM (MTSM) phases exhibit rich and distinctive bulk-boundary correspondence and response signatures that greatly expand understanding of consequences of topology in condensed matter settings, such as the limits on Fermi arc connectivity and structure, and transport signatures such as the chiral anomaly. In this paper, we therefore lay the foundation for extensive future study of MTSMs. Published by the American Physical Society 2024

Metasurface-based perfect vortex beam for optical eraser

Perfect vortex beams (PVBs) take advantage of conventional vortex beams regarding their property of constant diameter of the annular intensity distribution on different topological charges (TCs), facilitating spatially coupling multiple beams with different TCs simultaneously. However, there are demands for PVBs with larger TCs that can be integrated with CMOS-fabrication processes in applications since conditional PVBs are composed of bulky optical components. In this work, we demonstrate metasurface-based PVBs (MPVBs) with TCs as high as −32 and 16 in the visible, manifesting annular intensity distributions capable of broadband operation. The optical eraser concept by integrating MPVBs has been conducted, and the flower-like interference performs a helicity switch to facilitate the uniformization of ring-shaped intensity profiles for the MPVBs with different TCs. The optical eraser experiments demonstrate the potential of MPVBs in advancing both quantum optics and optical device engineering and pave the way for probing quantum behaviors in optics.

Nonlinear photonic crystals for completely independent asymmetric holographic imaging.

Nonlinear photonic crystals (NPCs) are microstructures characterized by a spatially modulated second-order nonlinear coefficient that have been extensively used for the generation and beam-shaping of coherent light at new frequencies. NPCs for asymmetric optical transmission have a significant impact on novel and multifunction photonic devices. However, nonreciprocal NPCs capable of completely independent asymmetric holographic imaging for the opposite propagation directions have not been reported. Here, we propose a holographic combiner for a different independent image generation at the second-harmonic (SH) wavelength when illuminated from opposite sides of NPCs. The design of the holographic combiner is based on a 3D nonlinear detour phase holography and an orbital angular momentum (OAM) multiplexing nonlinear holography. This work achieves completely independent asymmetric holographic imaging at the SH frequency by using NPCs, which may have potential applications in classical and quantum optical devices.

Unidirectional Reflectionlessness and Transmissionlessness in Indirectly Coupled Whispering‐Gallery Mode Resonators

AbstractThe reflection and transmission characteristics of a system composed of two whispering‐gallery mode (WGM) resonators are explored. Each resonator contains a Zeeman split quantum dot and side‐couples to an optical fiber. The results indicate that the unidirectional reflectionlessness and transmissionlessness can be achieved by adjusting the coupling strength between the resonators and the optical fiber, as well as the transition rate between the counter‐propagating modes within the WGM resonators. Besides, a one‐to‐one correspondence is set up between the resonance frequencies of quantum dots' energy levels and the positions of reflectionlessness (transmissionlessness) peaks when phase shift between two WGM resonators is . This research provides the valuable insights for the development of quantum optical devices such as isolators, circulators, and routers.

Stacking-Controlled Growth of rBN Crystalline Films with High Nonlinear Optical Conversion Efficiency up to 1.

Nonlinear optical crystals lie at the core of ultrafast laser science and quantum communication technology. The emergence of 2Dmaterials provides a revolutionary potential for nonlinear optical crystals due to their exceptionally high nonlinear coefficients. However, uncontrolled stacking orders generally induce the destructive nonlinear response due to the optical phase deviation in different 2D layers. Therefore, conversion efficiency of 2D nonlinear crystals is typically limited to less than 0.01% (far below the practical criterion of >1%). Here, crystalline films of rhombohedral boron nitride (rBN) with parallel stacked layers are controllably synthesized. This success is realized by the utilization of vicinal FeNi (111) single crystal, where both the unidirectional arrangement of BN grains into a single-crystal monolayer and the continuous precipitation of (B,N) source for thick layers are guaranteed. The preserved in-plane inversion asymmetry in rBN films keeps the in-phase second-harmonic generation field in every layer and leads to a record-high conversion efficiency of 1% in the whole family of 2D materials within the coherence thickness of only 1.6µm. The work provides a route for designing ultrathin nonlinear optical crystals from 2D materials, and will promote the on-demand fabrication of integrated photonic and compact quantum optical devices.

Transition to chaos in extended systems and their quantum impurity models

Chaos sets a fundamental limit to quantum-information processing schemes. We study the onset of chaos in spatially extended quantum many-body systems that are relevant to quantum optical devices. We consider an extended version of the Tavis–Cummings model on a finite chain. By studying level-spacing statistics, adjacent gap ratios, and spectral form factors, we observe the transition from integrability to chaos as the hopping between the Tavis–Cummings sites is increased above a finite value. The results are obtained by means of exact numerical diagonalization which becomes notoriously hard for extended lattice geometries. In an attempt to circumvent these difficulties, we identify a minimal single-site quantum impurity model that successfully captures the spectral properties of the lattice model. This approach is intended to be adaptable to other lattice models with large local Hilbert spaces.

Narrowband photoluminescence of Tin-Vacancy colour centres inSn-doped chemical vapour deposition diamond microcrystals.

Tin-Vacancy (Sn-V) colour centres in diamond have a spin coherence time in the millisecond range at temperatures of 2 K, so they are promising to be used in diamond-based quantum optical devices. However, the incorporation of large Sn atoms into a dense diamond lattice is a non-trivial problem. The objective of our work is to use microwave plasma-assisted chemical vapour deposition (CVD) to grow Sn-doped diamond with submicron SnO2 particles as a solid-state source of impurity. Well-faceted diamond microcrystals with sizes of afewmicrometres were formed on AlN substrates. The photoluminescence (PL) signal with zero-phonon line (ZPL) peak for Sn-V centre at ≈620 nm was measured at room temperature (RT) and at 7 K. The peak width (full width at half-maximum) was measured to be 1.1-1.7 nm at RT and ≈0.05 nm at 7 K. The observed variations of ZPL shape and position, in particular, narrowing of PL peak at RT and formation of single-line fine structure at low-T, are attributed to strain in the crystallites. The diamond doping with Sn via CVD process offers a new route to from Sn-V colour centre in the bulk of the diamond crystallites. This article is part of the Theo Murphy meeting issue 'Diamond for quantum applications'.

Quantum optical memory for entanglement distribution

Optical photons are powerful carriers of quantum information, which can be delivered in free space by satellites or in fibers on the ground over long distances. Entanglement of quantum states over long distances can empower quantum computing, quantum communications, and quantum sensing. Quantum optical memories are devices designed to store quantum information in the form of stationary excitations, such as atomic coherence, and are capable of coherently mapping these excitations to flying qubits. Quantum memories can effectively store and manipulate quantum states, making them indispensable elements in future long-distance quantum networks. Over the past two decades, quantum optical memories with high fidelities, high efficiencies, long storage times, and promising multiplexing capabilities have been developed, especially at the single-photon level. In this review, we introduce the working principles of commonly used quantum memory protocols and summarize the recent advances in quantum memory demonstrations. We also offer a vision for future quantum optical memory devices that may enable entanglement distribution over long distances.

Enhanced Homogeneity of Moiré Superlattices in Double-Bilayer WSe2 Homostructure.

Moiré superlattices have emerged as a promising platform for investigating and designing optically generated excitonic properties. The electronic band structure of these systems can be qualitatively modulated by interactions between the top and bottom layers, leading to the emergence of new quantum phenomena. However, the inhomogeneities present in atomically thin bilayer moiré superlattices created by artificial stacking have hindered a deeper understanding of strongly correlated electron properties. In this work, we report the fabrication of homogeneous moiré superlattices with controllable twist angles using a 2L-WSe2/2L-WSe2 homostructure. By adding extra layers, we provide additional degrees of freedom to tune the optical properties of the moiré superlattices while mitigating the nonuniformity problem. The presence of an additional bottom layer acts as a buffer, reducing the inhomogeneity of the moiré superlattice, while the encapsulation effect of the additional top and bottom WSe2 monolayers further enhances the localized moiré excitons. Our observations of alternating circularly polarized photoluminescence confirm the existence of moiré excitons, and their characteristics were further confirmed by theoretical calculations. These findings provide a fundamental basis for studying moiré potential correlated quantum phenomena and pave the way for their application in quantum optical devices.

К вопросу оценки надежности суперлюминесцентных диодов

A superluminescent diode (SLED or SLD) are used in low coherence tomography and in fiber-optic gyroscopes, where sources with a short coherence length and relatively high radiation power are required. SLED are, as a rule, the least reliable, and at the same time, extremely important for ensuring operability device. The article discusses the issue of resource reliability of the SLED to analyze the possibility of improving the accuracy of devices based on them during long-term operation. The work is a brief overview of achievements in the field of resource reliability analysis of quantum optical semiconductor devices, obtaining a general representation of the reliability of superluminescent radiation sources, changes in their parameters as a result of degradation, consideration of ways to solve problems associated with their spectral degradation.

Vacuum technique of nanodiamond dispersing on a substrate from an aqueous suspension

With the successful development of luminescent nanodiamond production, single diamond nanoparticles began to be actively used in the design of temperature and magnetic field nanosensors, quantum optical devices, and other nanotechnology applications. These applications require both express optical characterization of a large number of single nanoparticles and the ability to manipulate them. In this regard, the actual task is the low-density distribution of large ensembles of individual nanodiamonds on various substrates. In this study, we propose a vacuum technique for nanoparticle deposition on a substrate from its aqueous suspension, which has not been previously used in nanodiamond studies. The characteristic features of the spatial distribution of nanoparticles on a substrate were studied by atomic force microscopy. It has been shown that by reducing the nanodiamond concentration in the initial aqueous suspension, one can achieve a density of ≤1 particle/μm2 on almost the entire area of the substrate covered with nanodiamonds.

Chiral topological add–drop filter for integrated quantum photonic circuits

The integration of quantum emitters within topological nanophotonic devices enables the control of light–matter interactions at the single photon level. Here, we experimentally realize an integrated topological add–drop filter and observe multiport chiral emission from single photon emitters (quantum dots) embedded within the device. The filter is imprinted within a valley-Hall photonic crystal membrane and comprises a resonator evanescently coupled to a pair of access waveguides. We show that the longitudinal modes of the resonator enable the filter to perform wavelength-selective routing of light, protected by the underlying topology. Furthermore, we demonstrate that for a quantum dot located at a chiral point in the resonator, selective coupling occurs between well-defined spin states and specific pairs of the filter output ports. The combination of multiport routing, allied with the inherent nonreciprocity of the device at the single photon level, presents opportunities for the formation of complex quantum optical devices, such as an on-chip quantum optical circulator.