Utilizing Rydberg superatoms to fuse W state and GHZ state

Qiuping Shao, Jie Wang, Yanqiang Ji, Y. L. Liu, Li Dong, and Xiao-Ming Xiu

DOI: 10.1364/JOSAB.507157 Received 29 Sep 2023; Accepted 22 Nov 2023; Posted 22 Nov 2023  View: PDF

Abstract: Multi-particle entanglement has important applications in quantum information and quantum computing. Here we propose two schemes to fuse large-scale entangled W state and GHZ state. In the first fusion scheme, we send two Rydberg superatoms which belong to an n-particle W state and an m-particle W state, respectively, into a vacuum cavity, an (n+m-2)-particle W state can be obtained by detecting the state of the superatoms after the interaction. In the second fusion scheme, we send two Rydberg superatoms into two separate cavities, with the assistance of circularly polarized photon, we can obtain a (k+l)-particle GHZ state after detecting the state of the photon. The numerical simulation analysis shows that both of the two schemes are robust against both the spontaneous emission of superatoms and the decay of cavity. The feasibility analysis indicates that this two schemes can be realized in experiment.

Asynchronous Topological Phase Transition in Trimer Lattices

Yu Dang, Jin Zhang, Tao Jiang, Guoguo Xin, Junhao Yang, Wenjing Zhang, and Xinyuan Qi

DOI: 10.1364/JOSAB.509952 Received 20 Oct 2023; Accepted 22 Nov 2023; Posted 22 Nov 2023  View: PDF

Abstract: We propose a non-reciprical double-layer trimer photonic lattice model. In this model, two kinds of topological phase are presented. By adjusting the the imaginary coupling coefficients and intra-cell coupling coefficients in this model, the two topological phases appeared in different coefficient ranges and they show asynchronous topological phase transition during changing the coupling coefficients. We discovered that these asynchronous topological phase transitions can impact the system's light transmission properties. When the coupling coefficients are adjusted to put the system in a topologically non-trivial state, the light beam injected along the edge tends to localize at the edge. Moreover, before and after the phase transition the lowest energy band, The evolution of the light beam at the boundary exhibits oscillatory and non-oscillatory behavior. Realizing asynchronous topological phase transitions can be employed to control the light transmission properties of the system, which has potential applications in optical communication and the design of photonic integrated circuits.

Scalability of differential-(quadrature)-phase-shift quantum digital signature

Kyo Inoue and Toshimori Honjo

DOI: 10.1364/JOSAB.502166 Received 01 Aug 2023; Accepted 20 Nov 2023; Posted 20 Nov 2023  View: PDF

Abstract: Quantum digital signature (QDS) is a quantum communication technology that distributes authentication keys to candidates of message recipients who will confirm if a message received afterward is the legitimate one, referring to the authentication keys. Although accommodating many recipients maybe one of the significant QDS system performances, conventional QDS protocols seem indifferent to this issue. In this study, we investigate the number of accommodable recipients in recently proposed differential-phase-shift (DPS) QDS and differential-quadrature-phase-shift (DQPS) QDS systems. They are unique QDS protocols in which quantum signal are broadcasted to all recipients simultaneously and there is no post data-processing between the sender and recipients, which is favorable to accommodate a large number of recipients. We analyze the system conditions required to satisfy the QDS criteria, and evaluate the maximum number of recipients. The results indicate that several hundreds of recipients can be accommodated in a 100-km transmission system.

Ultra-high-Q and sensitive refractive index sensing in low refractive index dielectric gratings based on bound states in the continuum

Zezhou Fang, Han-Lei Xu, JIn-Yue Su, Jinyun Zhou, and Ziming Meng

DOI: 10.1364/JOSAB.506368 Received 18 Sep 2023; Accepted 20 Nov 2023; Posted 20 Nov 2023  View: PDF

Abstract: The realization of high quality factor (Q-factor) and strong local optical fields has long been of great interest in the field of nanophotonics. Unfortunately, it is still challenging to achieve high-Q and strong localized fields in nanostructures made of low refractive index materials. In this study, drawing upon the concept of bound states in the continuum (BIC), an asymmetric dielectric grating composed of low refractive index materials is demonstrated to generate an ultra-high-Q symmetry-protected quasi-BIC in the visible wavelength. Importantly, the design of BIC (quasi-BIC) mode enables the strong localized confinement of light in air. By leveraging this property, we realize ultra-sensitive refractive index sensing with a remarkable sensitivity of 669 nm/RIU and a high figure of merit (FOM) of 45314 RIU-1. This study offers a novel approach to achieve highly sensitive and high-precision refractive index sensing with potential applications in the practical realization of strong light-matter interactions using low-index materials.

Sub-nanosecond free carrier recombination in an indirectly excitedquantum-well heterostructure

Michele Perlangeli, Francesco Proietto, Fulvio Parmigiani, and Federico Cilento

DOI: 10.1364/JOSAB.507039 Received 28 Sep 2023; Accepted 19 Nov 2023; Posted 20 Nov 2023  View: PDF

Abstract: Nanometer-thick quantum-well structures are quantum model systems offering a few discrete unoccupied energy states that can be impulsively filled and that relax back to equilibrium predominantly via spontaneous emission of light. Here we report on the response of an indirectly excited quantum-well heterostructure, probed by means of time and frequency resolved photoluminescence spectroscopy. This experiment provides access to the sub-nanosecond evolution of the free electron density, indirectly injected in the quantum-wells. In particular, the modelling of the time-dependent photoluminescence spectra unveils the time evolution of the temperature and of the chemical potentials for electrons and holes, from which the sub-nanosecond time-dependent electron density is determined. This information allows to prove that the recombination of excited carriers is mainly radiative and bimolecular at early delays after excitation, while, as the carrier density decreases, a monomolecular and non-radiative recombination channel becomes relevant. Access to the sub-nanosecond chronology of the mechanisms responsible for the relaxation of charge carriers provides a wealth of information for designing novel luminescent devices with engineered spectral and temporal behavior.

Influence of the interaction geometry on the fidelity of the two-qubit Rydbergblockade gate

Ivan Vybornyi, Leonid Gerasimov, Dmitriy Kupriyanov, Stanislav Straupe, and Kirill Tikhonov

DOI: 10.1364/JOSAB.504629 Received 31 Aug 2023; Accepted 19 Nov 2023; Posted 20 Nov 2023  View: PDF

Abstract: We present a comparative analysis of physical constraints limiting the quality of spin entanglement created using the Rydberg blockade technique in an ensemble of trapped neutral 87Rb atoms. Based on the approach developed earlier in [Phys. Rev. A 106, 042410 (2022)], we consider the complete multilevel Zeeman structure of the interacting atoms and apply our simulations to two excitation geometries featured by different transition types, both feasible for experimental verification. We demonstrate that the blockade shift strongly depends not only on the interatomic separation but also on the angular position of the atom pair with respect to the quantization axis determined by polarization of the driving fields. As an example, we have estimated fidelity for a promising design of a CZ gate, recently proposed by H. Levine et al. [Phys. Rev. Lett. 1 , 170503 (2019)] for various possible experimental geometries. Anisotropic effects in entangling gates considered here are important for the optimal choice of proper geometry for quantum computing in two- and three-dimensional arrays of atomic qubits and are of considerable interest for quantum silmulators, especially those which are designed for anisotropic physical models.

Characterization of the Polarization Fluctuations in Gain-Switched VCSELs for Quantum Random-Number Generation

Ana Quirce, Angel Valle, Marcos Valle-Miñón, and Jaime Gutiérrez

DOI: 10.1364/JOSAB.506611 Received 20 Sep 2023; Accepted 18 Nov 2023; Posted 22 Nov 2023  View: PDF

Abstract: We report a characterization of the polarization fluctuations observed when gain-switching vertical-cavity surface-emitting lasers (VCSELs) for quantum random number generation (QRNG) applications. We compare our experimental measurements with the results obtained from a stochastic rate equations model that incorporates the intrinsic parameters of the VCSEL found using the state-of-the-art experimental techniques. The good agreement obtained between our experiments and simulations can be used to establish a validation process that permits to monitor the device behaviour to detect malicious intrusion or malfunctioning of the QRNG. Simulations of the model are used to look for parameters that maximize the QRNG performance. Along this direction we consider the performance when considering a VCSEL with vanishing values of the amplitude and phase anisotropies. We show that in this system the obtained raw bits have a low bias value that is independent on the sampling time chosen to obtain the random bit and on the parameters of the modulation. We also use the simulations of the model to predict the QRNG performance at high modulation frequencies. We show that random bits obtained at several Gbps rates, after appropriate post-processing, fully pass the NIST statistical test.

Rigorous Higher Order Poincar{\'e} Optical Vortex modes

Koray Köksal, Mohamed Babiker, and Vassilis Lembessis

DOI: 10.1364/JOSAB.500511 Received 12 Jul 2023; Accepted 18 Nov 2023; Posted 20 Nov 2023  View: PDF

Abstract: The state of polarisation of a general form of an optical vortex mode is represented by the vector ${\bn {\hat{\epsilon}}}_m$ which is associated with a vector light mode of order $m> 0$. It is formed as a linear combination of two product terms involving the phase functions $e^{\pm im\phi}$ times the optical spin unit vectors ${\bn {\sigma}}^{\mp}$. Any such state of polarisation corresponds to a unique point $(\Theta_P,\Phi_P)$ on the surface of the order $m$ unit Poincar\'e sphere. However, albeit a key property, the general form of the vector potential in the Lorentz gauge ${\bf A}={\bn {\hat{\epsilon}}}_m\Psi_m$ from which the fields are derived, including the longitudinal fields, has neither been considered, nor has had its consequences explored. Here we show that the spatial dependence of $\Psi_m$ can be found rigorously by demanding that the product ${\bn {\hat{\epsilon}}}_m\Psi_m$ satisfies the {\underline{vector}} paraxial equation. For a given order $m$ this leads to a unique $\Psi_m$ which has no azimuthal phase of the kind $e^{i\ell\phi}$ and it is a solution of a {\underline{scalar}} partial differential equation with $\rho$ and $z$ as the only variables. The theory is employed to evaluate the angular momentum for a general Poincar\'e mode of order $m$ yielding the angular momentum for right and left circularly polarised, elliptically-polarised, linearly-polarised and radially and azimuthally-polarised higher order modes. We find that only the modes of order $m\geq 2$ have non-zero angular momentum. All modes have zero angular momentum for points on the equatorial circle for which $\cos\Theta_P=0$.

Resonance ionization spectroscopy of high-lying 4sns and 4snd Rydberg levels of odd calcium isotopes

Yoshihiro Iwata, Miyabe Masabumi, Katsuaki Akaoka, Ikuo Wakaida, and Shuichi Hasegawa

DOI: 10.1364/JOSAB.507539 Received 11 Oct 2023; Accepted 17 Nov 2023; Posted 22 Nov 2023  View: PDF

Abstract: Calcium Rydberg levels are of significant interest for efficient and isotope-selective resonance ionization of trace radionuclides such as calcium-41 (⁴¹Ca). In this study, we report novel measurement data on the energy level shifts of ⁴³Ca for 4sns ¹S₀ and 4s(n-1)d ¹D₂ (n=40,45,50,55,60) Rydberg levels due to hyperfine-induced singlet-triplet mixing specific to isotopes with an odd mass number. Both ³S₁ and ³DJ triplet signals corresponding to forbidden transitions were enhanced for ⁴³Ca at the high principal quantum numbers n=55 and 60, indicating a mixing of singlet components to some extent.

Sub-diffraction metalens for generating longitudinal bifoci and optical needle

Zhixiang Wu, Xinyu Li, Yiyang Zou, Deng Hu, Liang Xiong, and liping shang

DOI: 10.1364/JOSAB.505482 Received 11 Sep 2023; Accepted 16 Nov 2023; Posted 16 Nov 2023  View: PDF

Abstract: Lenses are a fundamental component of optical systems. Bifoci and optical needle devices have excellent application potential in many optical systems. Conventional lenses are limited by their diffraction limits, and the spot size has a considerable influence on the resolution of optical and microscopic images. Optical super-oscillation is a novel technique for far-field sub-diffraction focusing. In this study, we proposed a binary-amplitude super-oscillatory lens (SOL) approach for generating bifoci and optical needles (ON), and it was based on angular spectrum method (ASM) and a binary-particle-swarm optimization (BPSO) algorithm. We reported a class of binary-amplitude-based Bifoci- and ON-SOLs that generated sub-diffraction bifoci and optical needles. Sub-diffraction bifoci with a transverse range of 0.401λ–0.522λ were archived for a work wavelength of λ = 632.8 nm. The generated optical needle had a sub-diffraction length of 4.122λ, and the super-oscillation region was 2.083λ long. The design and fabrication of such binary-amplitude devices is easy to implement, and the proposed lens design method can be extended to other optical bands.

Inverse Design of Polymorphic Dirac-like Cone Dispersion Relationship Photonic Crystals

Yixin Wang, Quan Xie, and Chun Jiang

DOI: 10.1364/JOSAB.506157 Received 15 Sep 2023; Accepted 16 Nov 2023; Posted 20 Nov 2023  View: PDF

Abstract: Dirac-like cone linear dispersion relations in photonic crystals (PhCs) often endow them with unique properties, yet searching for such relations can be challenging. We introduce a generalized inverse design system that, given the dielectric constants and lattice of two-dimensional PhCs, can efficiently determine its structural parameters to obtain its Dirac-like cone dispersion. Employing this inverse design strategy, we design three types of Dirac cone PhCs, including triple degenerate, quadruple degenerate, and triple degenerate under dual-polarization with the same frequency. Further investigations reveal a systematic relationship between the radius of the dielectric rods in these PhCs and their corresponding Dirac frequencies across varying dielectric constants. The zero-refractive index characteristic is validated in two of the three PhCs studied, as confirmed through numerical simulations. Additionally, by leveraging our proposed inverse design method, we introduce an innovative shell dielectric rod model, which encapsulates a dielectric material, achieving a quadruple degenerate dispersion structure with dual Dirac cones. This research provides a potent tool for the inverse design of PhCs and expands its application in Dirac cone dispersion design.

Coherence as an indicator to discern electromagnetically induced transparency and Autler-Townes splitting

Arif Laskar, Pratik Adhikary, Niharika Singh, and Saikat Ghosh

DOI: 10.1364/JOSAB.505262 Received 07 Sep 2023; Accepted 14 Nov 2023; Posted 14 Nov 2023  View: PDF

Abstract: Electromagnetically induced transparency (EIT) and Autler-Townes splitting (ATS) are generally characterized and distinguished by the width of the transparency created in the absorption profile of a weak probe in presence of a strong control field. This often leads to ambiguities, as both phenomena yield similar spectroscopic signature. However, an objective method based on the AIC test offers a quantitative way to discern the two regimes when applied on the probe absorption profile. The obtained transition value of control field strength was found to be higher than the value given by pole analysis of the corresponding off-diagonal density matrix element $\rho_{13}$. By contrast, we apply the test on ground state coherence $\rho_{12}$ and the measured coherence quantifier, which yielded a distinct transition point around the predicted value even in presence of noise. Our test accurately captures the transition between the two regimes, indicating that a proper measure of coherence is essential for making such distinctions.

Machine learning for self-tuning mode-locked lasers with multiple transmission filters

Mahmut Bagci and J. Kutz

DOI: 10.1364/JOSAB.505672 Received 12 Sep 2023; Accepted 14 Nov 2023; Posted 14 Nov 2023  View: PDF

Abstract: We develop an adaptive control and self-tuning procedure for mode-lock fiber laser systems using multiple transmission filters. Critical for self-tuning is the ability to properly characterize the average cavity birefringence for which we propose three classification algorithms based upon learned libraries of observed dynamic patterns, including a uniform, a hierarchical, and a dynamic selection procedure from such patterns. A maximum seeking algorithm is then constructed to determine the optimal (maximal) waveplate(s) and polarizer(s) settings. Thus the adaptive control and self-tuning scheme is designed as a combination of maximum seeking and dynamic library selection algorithms. Numerical implementation shows that the proposed self-tuning scheme achieves stable, high-energy mode-locking while circumventing the multi-pulsing instability.

Cascaded sum frequency generation of ultraviolet laser source at 228 nm based on stimulated Raman adiabatic passage

yintong jin, zhen chen, jialiang zhang, and Changshui Chen

DOI: 10.1364/JOSAB.506363 Received 18 Sep 2023; Accepted 14 Nov 2023; Posted 14 Nov 2023  View: PDF

Abstract: Based on stimulated Raman adiabatic passage (STIRAP) technology, a cascaded sum frequency generation (SFG) conversion scheme is proposed for generating an ultraviolet laser source at 228 nm. The conversion involves two simultaneous SFG processes, in which the input signal laser is converted to ultraviolet laser through a negligible intermediate laser. Numerical simulations demonstrate the efficient conversion processes in a nonlinear LaBGeO5 (LBGO) crystal, and the effects of the coupling modulation function, pump laser intensity, and temperature on the quantum efficiency are investigated. The output of a tunable ultraviolet laser source was achieved by varying the signal or pump laser wavelength. The large amount of new optical data obtained in this work will contribute to the generation of ultraviolet laser sources.

Refractive index sensor based on D-shaped resonator and stub resonator and its slow light characteristics

Yunping Qi, SHIYU ZHAO, Qiang Shi, Li Wang, Yujiao Wen, Zhou zihao, Shu Zhang, and xiang xian wang

DOI: 10.1364/JOSAB.505989 Received 15 Sep 2023; Accepted 13 Nov 2023; Posted 13 Nov 2023  View: PDF

Abstract: In this paper, a Metal-Insulator-Metal waveguide structure is proposed based on a D-shaped resonator and a stub resonator and it can generate multiple Fano resonances. The magnetic field (Z-direction) distribution and transmission spectrum of the structure are analyzed by the finite element method (FEM). The theory results are performed with the multimode interference coupled mode theory (MICMT), and they show high agreement with the simulation outcomes. The calculations also discuss the effect of structural parameters on the transmission spectrum. Moreover, the structure’s sensing characteristics are analyzed in detail, achieving a maximum sensitivity and FOM* of 1300 𝑛𝑚/𝑅𝐼𝑈 and 181.44, respectively. In addition, the slow-light properties of the structure are also investigated, whose group delay and group index can reach 0.24 ps and 48.93, respectively. The group delay time is dynamically regulated by controlling the number of D-shaped resonators to achieve the effect of a delay line. It can provide some reference value for multifunctional on-chip optical integrated devices based on MIM waveguide structure.

Surface plasmon resonance sensor based on a D-shaped hollow microstructured fiber with bimetallic film

Ling Tian-Sheng, yuting Zhang, Yulai She, Hao Du, Huajun Lai, and Yi Xu

DOI: 10.1364/JOSAB.495194 Received 24 May 2023; Accepted 13 Nov 2023; Posted 14 Nov 2023  View: PDF

Abstract: The proposed surface plasmon resonance (SPR) sensor is based on a D-shaped hollow microstructured fiber with a bimetallic film. Gold (Au) is deposited on the flat surface of the PCF to excite surface plasmon resonance. Indium tin oxide (ITO) acts is covered the gold and the fiber surface as an interlayer. The use of bimetallic films improves the adhesion between optical films and fiber surfaces, and enhances the coupling effect of SPR. The effect of air holes in the core and the thickness of the metal film on the sensor performance was analyzed using the finite element method. The theoretical maximum wavelength sensitivity of the sensor in the refractive index (RI) detection range of 1.30-1.39 is 9900 nm/RIU, which corresponds to a resolution of 1.01×10-5 RIU-1, and a maximum amplitude sensitivity of 425.58 RIU-1. The proposed sensor becomes a candidate for biomolecular detection and environmental detection as it has high sensitivity and avoids the internal coating of the plasmonic metals.

Higher Order Multipoles in Metaphotonic Structures: An Overview Of Symmetric Approaches And Providing A Comprehensive Theoretical Method

Hosein Allahverdizade, Ehsan Afkari, Sina Aghdasinia, and Mohammad Bemani

DOI: 10.1364/JOSAB.503770 Received 21 Aug 2023; Accepted 13 Nov 2023; Posted 13 Nov 2023  View: PDF

Abstract: This research explores localized electric fields in 2-D photonic crystals, focusing on higher order multipoles. Novel formulas are developed to accurately describe and analyze these complex electromagnetic modes. By considering various crystal element arrangements, we investigate the formation and interactions of electric, magnetic, and toroidal moments. we examine the effects of symmetry on the localized electromagnetic fields in 2-D periodic structures and explain how Bound States in the Continuum (BICs) arise and behave in different symmetry classes. It is important to point out that every singularity point which occur in multipolar series expansions depends on a BIC point and it inspire us to study the characteristic of them. Furthermore, we analyze a variety of BICs and use perturbed and degeneracy breaking to investigate high-Q factor BICs. The results provide a thorough understanding of how symmetry and multi-polar interactions affect potential applications in cutting-edge metasurfaces and photonic devices (metaphotonic).

Cancer Cell Detection by Plasmonic Dual V-shaped PCF Biosensor

mai makawy, Yusuf Hamoud, REDA A.EL-KHORIBI, WAFAA SOLIMAN, yehia badr, Mohamed Hameed, and Salah Obayya

DOI: 10.1364/JOSAB.500921 Received 17 Jul 2023; Accepted 13 Nov 2023; Posted 20 Nov 2023  View: PDF

Abstract: In this paper, highly sensitive plasmonic photonic crystal fiber (PCF) biosensor is reported for cancer cell detection. The modal analysis of the reported biosensor is performed using full vectorial finite element method (FVFEM). The suggested PCF sensor has dual V-shaped groves to enhance the sensor sensitivity where two gold nano-rods are mounted on the etched surfaces. The main idea of the optical sensors is to track the electromagnetic coupling between the leaky core mode and the surface plasmon mode (SPM) at the metal/dielectric interface. When the SP mode and one of the fundamental core modes are phase-matched, strong coupling occurs. Therefore, maximum confinement loss is achieved for the core-guided mode at the resonance wavelength which depends on the analyte refractive index (RI). The V-shaped groove enhances the core/SPM coupling where high RI sensitivity of 24,000 nm/RIU is achieved along refractive index (RI) range from 1.38 to 1.39, with a resolution of 2.703×〖10〗^(-6) RIU. The potential of using the suggested RI sensor for cancer cell detection is then demonstrated. In this context, high sensitivities of ,700 nm/RIU, 8,208 nm/RIU and 14,428.6 are obtained for basal, cervical, and breast cancer cells with resolutions of 4.22×〖10〗^(-6) RIU,12.18×〖10〗^(-6) RIU, and 6.93×〖10〗^(-6) RIU, respectively. The achieved sensitivity and resolution are higher than that of the recent reported cancer biosensors. Moreover, the developed label free biosensor is safer than other chemical and surgical techniques

A self-powered photodetector based on CsPbBr3/n-Si Schottky junction

Feng Hua, Xin Du, huang yu, Yiting Gu, Jianfeng Wen, Fuchi Liu, Junxue Chen, and Tao Tang

DOI: 10.1364/JOSAB.503296 Received 15 Aug 2023; Accepted 12 Nov 2023; Posted 13 Nov 2023  View: PDF

Abstract: Self-powered photodetectors (SPPDs) are attracting considerable publicity due to their superiority over conventional photodetectors (PDs) in terms of high sensitivity, fast response, and no need for an external power supply. Halide perovskites are much anticipated in SPPDs for their unusual photoelectronic properties. This work developed a Schottky-junction CsPbBr3/n-Si SPPD by growing stable all-inorganic CsPbBr3 microcrystals on an n-Si substrate using a solution method. At zero bias, such Schottky SPPD has a very weak dark current (0.3 pA). Moreover, the device has a wide linear dynamic range (LDR, 110 dB), sizeable on/off ratio (>105) and high detection rate (>1012 Jones). Through the research of this project, it is expected to obtain a new way to prepare Schottky photodiodes with high stability and self-driven.

Coherent control of a multi-level resonant medium bysubcycle pulses

Anton Pakhomov, Nikolay Rosanov, Mikhail Arkhipov, and Rostislav Arkhipov

DOI: 10.1364/JOSAB.503633 Received 17 Aug 2023; Accepted 12 Nov 2023; Posted 13 Nov 2023  View: PDF

Abstract: We theoretically demonstrate the possibility of the coherent control of the response of a multi-level resonant medium by means of half-cycle unipolar or quasi-unipolar pulses. We show that despite the ultra-broadspectrum of half-cycle pulses one can efficiently steer the induced medium polarization through the proper choice of the parameters of excitation pulses. Besides, we find out that the response of a multi-levelmedium for the amplitude of driving subcycle pulses below a certain threshold can be quantitatively well approximated by the two-level model.

All-dielectric metasurface with multiple Fano resonances supporting high-performance refractive index sensing

Chen Zhao, Yiping Huo, Tong Liu, Zuxiong Liao, Congmu Xu, and Tao Zhang

DOI: 10.1364/JOSAB.505147 Received 07 Sep 2023; Accepted 11 Nov 2023; Posted 13 Nov 2023  View: PDF

Abstract: All-dielectric metasurface has important application value in many fields, especially in refractive index sensing. In this paper, an all-dielectric metasurface composed of silicon triangular-hole nanodisk array is designed and studied numerically. Through introducing asymmetry in the proposed metasurface and transforming the bound states in the continuum (BIC) into the quasi-BIC, three sharp Fano resonances with almost 100% modulation depth can be achieved, and the highest quality-factor (Q-factor) can reach 49,915. Further, the three Fano resonances can be regulated and controlled by adjusting the structural parameters. Moreover, the sensing performance of the structure is researched by changing the ambient refractive index. The maximum sensitivity obtained is 245 nm/RIU, and the best figure of merit (FOM) is 1880. The proposed structure provids a scheme for the design of optical devices, especially refractive index sensors.

Giant and tunable 2D-chiroptical response in few-layer borophene metasurfaces

Min Cheng

DOI: 10.1364/JOSAB.505479 Received 11 Sep 2023; Accepted 10 Nov 2023; Posted 13 Nov 2023  View: PDF

Abstract: The 2D-chiroptical response in the few-layer borophene metasurfaces (FBM) is studied theoretically. By stacking borophene metasurfaces with the same physical parameters, near the topological transition for borophene metasurface it is found that there exist strong 2D chirality, which can be controlled by the incident angle and the twist angle between the metasurfaces. When the borophene metasurfaces with different electron densities are stacked, the strong circular conversion dichroism (CCD) is found near the corresponding topological transition frequency for each borophene metasurface, resulting in the formation of the multiband CCD spectra. It is demonstrated that in the FBM there exist the ultrahigh sensitivity of the CCD to substrate refractive index.

Hyper-parallel nonlocal CNOT operation assisted by quantum-dot spin in double-sided optical microcavity

Meng-Fan Chen, Ping Zhou, Qi Lan, and Xiang-Qi Lu

DOI: 10.1364/JOSAB.505732 Received 11 Sep 2023; Accepted 10 Nov 2023; Posted 10 Nov 2023  View: PDF

Abstract: Implementation CNOT operation between different nodes in quantum communication network nonlocally plays an important role in distributed quantum computation.We present a protocol for implementation of hyper-parallel nonlocal CNOT operation via hyperentangled photons simultaneously entangled in spatial-mode and polarization degree of freedoms(DOF) assisted by quantum-dot spin in double-sided optical microcavity. The agent Alice lets photons traverse the double-sidedoptical microcavity sequentially and applies single-qubit measurements on the electron and the hyperentangled photon. The agent Bob first performs corresponding unitary operations according to Alice's measurement results, then lets photons traverse the double-sided optical microcavity sequentially and performs the single-qubit measurements. The hyper-parallel nonlocal CNOT operation can be implemented simultaneously in spatial-mode and polarization degree of freedoms by performing single-qubit operations in accordance with Bob's measurement results. The protocol has the advantage of having high channel capacity for long-distance quantum communication by using hyperentangled state as the quantum channel.

Concept of Miniature Dipole Trap System based on Simple Architecture Grating Chip

Yumeng Zhu, Shiming Wei, Junyi Duan, Minghao Yao, Chenfei Wu, Shengkang Zhang, Zhilong Yu, Yadong Zhou, and Xiaochi Liu

DOI: 10.1364/JOSAB.498252 Received 16 Jun 2023; Accepted 10 Nov 2023; Posted 13 Nov 2023  View: PDF

Abstract: This research presents the theoretical demonstration of a grating chip that can facilitate a miniature dipole trap system for rubidium atoms. The innovative chip design is expected to form both a magneto-optical trap and a dipole trap with a single laser. The paper further examines the dependence of the chip's focusing properties and diffraction efficiency on its structural parameters. Findings confirm the proposed design's ability to effectively trap atoms. The research also proposes a compact vacuum chamber design compatible with the grating chip. This design incorporates a non-evaporable getter and dispenser, utilizing materials with minimal outgassing and helium permeation rates.

Forward Propagation and Backward Propagation Guided Mode Waves of Electric Dipole Resonances in hBN Metasurface

gao jin, Yue Zhao, Sheng Zhou, Qiang Zhang, shufang fu, XiangGuang Wang, Xuan Wang, and Xuan-Zhang Wang

DOI: 10.1364/JOSAB.500445 Received 12 Jul 2023; Accepted 10 Nov 2023; Posted 13 Nov 2023  View: PDF

Abstract: The generation of a forward propagation (FP) and backward propagation (BP) guided-mode in a double ridge hBN metasurface (DRM) is investigated. The DRM has the capability to effectively trap and guide incident light through diffraction and excitation of guided mode propagating within DRM. The x component of Poynting vector of the FP mode wave is identical and the BP mode is opposite to that of the incident wave. The BP mode frequency range for TE waves was found in the type I hyperbolic band (HB I) range, while for TM waves, it was found in the gap of HB I and type I hyperbolic band (HB II) range of hBN. The electric dipole (ED) moment contributes most significantly to the FP and BP mode, with its power being much greater than that of other multipolar moment modes. The DRM has shown promising potential in the field of sensors base on BP mode. These findings suggest that DRMs hold significant promise for the development of optical metasurfaces, optical switches, and high-performance sensors.

Comparing continuous and pulsed nitrogen-vacancy DC magnetometry in the optical-power-limited regime

Maggie Wang, Michael Caouette-Mansour, Adrian Solyom, and Lilian Childress

DOI: 10.1364/JOSAB.502566 Received 04 Aug 2023; Accepted 08 Nov 2023; Posted 10 Nov 2023  View: PDF

Abstract: Ensembles of nitrogen-vacancy (NV) center spins in diamond offer a robust, precise and accurate magnetic sensor. As their applications move beyond the laboratory, practical considerations including size, complexity, and power consumption become important. Here, we compare two commonly-employed NV magnetometry techniques -- continuous-wave (CW) vs pulsed magnetic resonance -- in a scenario limited by total available optical power. We develop a consistent theoretical model for the magnetic sensitivity of each protocol that incorporates NV photophysics - in particular, including the incomplete spin polarization associated with limited optical power; after comparing the models' behaviour to experiments, we use them to predict the relative DC sensitivity of CW versus pulsed operation for an optical-power-limited, shot-noise-limited NV ensemble magnetometer. We find a ~2-3 x gain in sensitivity for pulsed operation, which is significantly smaller than seen in power-unlimited, single-NV experiments. Our results provide a resource for practical sensor development, informing protocol choice and identifying optimal operation regimes when optical power is constrained.

Stability of homogeneous mode in metamaterial regime with structural disorder

Ekaterina Maslova, Matvey Sogrin, and M Rybin

DOI: 10.1364/JOSAB.503086 Received 14 Aug 2023; Accepted 08 Nov 2023; Posted 10 Nov 2023  View: PDF

Abstract: This research is aimed to the stability of the epsilon-near-zero homogeneous mode in the metamaterial composed of dielectric rods. The homogeneous mode is shown to be tolerant to modification of the geometrical shape of the metamaterial boundaries and to introduction of internal boundaries associated with super-wavelength voids inside the structure. Besides we study the influence of structural disorder, that is the deviation of the rod position from the lattice sites, which is the inherent feature of any real structures. We investigate the influence of the disorder degree on the stability of the homogeneous mode. The closer parameters of the structure to the boundary of the ``photonic crystal -- metamaterial’’ transition, the less stable epsilon-near-zero regime is. Although the homogeneous mode collapses at a certain frequency, there is a range of disorder degree at which the homogeneous mode is still observed but at the lower frequency. While the change in frequency is weak, the epsilon-near-zero regime is robust against the introduction of structural disorder.

Transverse mode distribution in multimode diode-pumped Raman fiber laser

Oleg Sidelnikov, Alexey Kuznetsov, Denis Kharenko, Mikhail Gervaziev, Evgeny Podivilov, Mickhail Fedoruk, Stefan Wabnitz, and Sergey Babin

DOI: 10.1364/JOSAB.503609 Received 29 Aug 2023; Accepted 08 Nov 2023; Posted 10 Nov 2023  View: PDF

Abstract: Raman lasers based on multimode graded-index fiber may generate high-quality (M²~2) Stokes beams when pumped by highly-multimode (M²>30) laser diodes. Here we examine, both experimentally and theoretically, the energy distribution of the output Stokes beam across the principal quantum mode number n in a bent multimode fiber, operating well above the Raman threshold. In contrast to Kerr spatial beam cleaning, leading to a Rayleigh-Jeans mode power distribution, in a multimode Raman fiber laser we find that the output mode powers approach an exponential distribution. We introduce a coupled-mode equations model including random linear coupling between neighboring mode groups, and obtain a good agreement between numerical simulations and experimental results. The model shows that, for typical mode coupling coefficients, the randomization of the mode power distribution is compensated by both nonlinear (Raman, Kerr) effects and linear filtering from the fs-inscribed fiber Bragg grating, both acting on the Stokes beam over successive round-trips. When random coupling becomes the dominating factor, the mode power distribution of the Stokes beam tends to equipartition, similarly to what is observed with large-size highly-multimode beams of low intensity (and nonlinearity) in the absence of any filtering.

Strategies for optimizing plasmonic grating couplers with topology-based inverse design

Michael Efseaff and Mark Harrison

DOI: 10.1364/JOSAB.502571 Received 04 Aug 2023; Accepted 06 Nov 2023; Posted 07 Nov 2023  View: PDF

Abstract: Numerical simulations have become a cornerstone technology in the development of nanophotonic devices. Specifically, 3D finite-difference time domain (FDTD) simulations are a widely used due to their flexibility and powerful design capabilities. More recently, FDTD simulations in conjunction with a design methodology called inverse design has become a popular way to optimize device topology, reducing a device’s footprint and increasing performance. We implement a commercial inverse design tool to generate complex grating couplers and explore a variety of grating coupler design methodologies. We compare the conventionally designed grating couplers to those generated by the inverse design tool. Finally, we discuss the limitations of the inverse design tool and how different design strategies for grating couplers affect inverse design performance, both in terms of computational cost and performance of the resulting device.

Hybrid multi-channel electrically tunable bandstop filter based on DAST electro-optical material

Yunping Qi, Shu Zhang, Qiang Shi, Mingrui Su, SHIYU ZHAO, Zhou zihao, and xiang xian wang

DOI: 10.1364/JOSAB.506177 Received 18 Sep 2023; Accepted 02 Nov 2023; Posted 03 Nov 2023  View: PDF

Abstract: A voltage tunable hybrid multichannel bandstop filter based on a metal-insulator-metal (MIM) waveguide is presented in this work, which can realize three narrowband and one broadband filtering functions simultaneously. The filter comprises two asymmetric composite cavities, which are filled with organic electro-optical material of 4-dimethylamino-N-methyl-4-toluenesulfonate (DAST). The composite cavity is composed of a rectangular cavity and an annular cavity, and the annular cavity is formed by two rectangular cavities connected with two semi-elliptical annular cavities. The transmission spectrum and magnetic field distribution of the filter are studied and analyzed by the finite element method (FEM), and the effects of the structure parameters on the transmission spectrum are discussed. Our analysis indicates that the bandstop filter has minimum transmittances of 0.02\%, 0.29\% and 0.1\%, minimum bandwidths of 5 nm, 9 nm and 25 nm, and maximum quality factors (\emph{Q}) of 1 .7, 87.1 and 44.2 respectively in three narrowband modes. The stopband bandwidth at the broadband mode is 70 nm, and the adjustable range is 1695-2065 nm. Additionally, the filter characteristics can be adjusted by imposing a control voltage, providing a high degree of tunability and maintaining stable filter performance. Finally, the basic structure is optimized yielding an increased bandwidth of 8 nm for the broadband mode, which does remain with great electrical tuning characteristics. Consequently, the proposed structure can be applied with huge potential in high-density integrated circuits and nano-optics.

Vortex light - based identification of directional emission from sodium atoms

Alexander Akulshin, Felipe Pedreros Bustos, Nafia Rahaman, and Dmitry Budker

DOI: 10.1364/JOSAB.499977 Received 06 Jul 2023; Accepted 28 Oct 2023; Posted 01 Nov 2023  View: PDF

Abstract: The parametric and nonparametric nonlinear processes responsible for generation of directional infrared radiation in sodium vapors, excited to the 4D5/2 energy level by resonant laser radiation, are identified by the transfer of orbital angular momentum from the pump radiation to the generated fields. We show that the optical fields generated by amplified spontaneous emission (ASE) simultaneously participate in several loops of four-wave mixing (FWM) generating new directional emission. The measured spectral linewidth of the FWM emission at 819.7 nm sets an upper limit to the linewidth of two fields resulting from ASE at 38.6 nm and 9093.0 nm, assuming their spectra are uncorrelated. Understanding details of the new-field generation is central to applications such as directional laser guide stars, stand-off magnetometry and entangled field generation.

CTDNet: Cartoon-Texture Decomposition-based Gray Image Super-Resolution Network with Multiple Degradations

Baoshun Shi, WENYUAN XU, and Xiuwei Yang

DOI: 10.1364/JOSAB.501776 Received 26 Jul 2023; Accepted 15 Oct 2023; Posted 01 Nov 2023  View: PDF

Abstract: In the case of multiple degradations, current deep learning-based gray image Super-Resolution (SR) methods equally process all components in an image, resulting in missing subtle details. To address this issue, we elaborate a Cartoon-Texture Decomposition-based (CTD) module that can automaticallydecompose an image into a smooth cartoon component and an oscillatory texture component. CTD module is a plug-and-play prior module that can be applied in solving imaging inverse problems. Specifically, for the SR task under multiple degradations, we apply CTD as a prior module to build an unfolding SR network termed CTDNet. For the SR task of real terahertz images, the boundary (i.e., the boundary between the object of interest and the carrier table) recovered by CTDNet has artifacts, which limits itsrealistic applications. To reduce these boundary artifacts, we post-process the SR terahertz images by using a boundary artifact reduction method. Experimental results on the synthetic dataset and real terahertz images demonstrate that the proposed algorithms can maintain subtle details and achieve comparable visual results.