arXiv subjects

Bingsuo Zou

Publications and source records attributed to Bingsuo Zou.

At least 19 recordsLinked to original sources

arXiv2026

Robust Unidirectional Edge States in the Continuum in non-Topological Floquet Photonic Crystals

Robust unidirectional edge propagation is conventionally attributed to topological protection. Whether edge states in the continuum (EICs) can exhibit such robustness in non-topological systems remains an open question. Here we demonstrate robust unidirectional EICs in Floquet photonic crystals (PhCs) composed of a honeycomb lattice of helical waveguides, where both time-reversal and spatial inversion symmetries are broken. Within a topologically trivial parameter regime of this system, where the Chern, valley Chern, and winding numbers all vanish, the EIC robustness is decoupled from topology. Instead, the robustness originates from a z-periodic Floquet artificial gauge field geometrically locked to the helical lattice. Numerical simulations show that the EIC survives 120 bent edges, 6% on-site potential noise, and 27% hopping phase noise. This work establishes a paradigm for robust light propagation in non topological systems and broadens the physical basis for unidirectional EICs.

physics.optics↗

arXiv2026

Dynamically preparing robust Bell states by time-boundary engineering

Quantum entanglement is essential for modern quantum information processing. Entanglement gates convert initially non-entangled states into entangled ones by applying time-dependent parametric pulses. While Bell state preparation has been experimentally validated in various platforms, its stability and fidelity are constrained by environmental decoherence and parametric fluctuations.Here, we propose a dynamical framework for preparing robust Bell states by leveraging time-boundary engineering and momentum-space projective measurements within Su-Schrieffer-Heeger (SSH) systems. Employing Lindblad master equation, we theoretically demonstrate that the prepared Bell states exhibit remarkable robustness against both environmental decoherence and parametric time fluctuations, achieving a nearly perfect quantum fidelity, with momentum conservation law governing this robust behavior. To enrich Bell states in momentum space, multi-band SSH models are designed to induce multifold time scattering processes. This time-boundary engineering framework is applicable to both fermionic and bosonic excitations, offering a robust paradigm for generating Bell states in quantum communication and quantum computation.

quant-ph↗

arXiv2024

Magnetic polaronic exciton in A-type 2D van der Waals bulk material CrSBr

2D magnetic semiconductor CrSBr exhibits unique magneto-optical properties, yet its electronic structure and photophysical mechanisms remain unclear at high magnetic field and low temperature. Through comprehensive spectroscopic investigations, its charge-transfer band edge is identified at 500 nm. Below this band-edge, local excitonic magnetic polaronic states from Cr3+ ions out of FM aggregates in layer and bilayer could be seen due to phonon-spin-exciton coupling, in which magnetic polaronic PL1 emission occurs at 720 nm from single Cr3+ d-d transition, a dark-state pair exciton occurs at 850 nm in 10 K magnetic field, and double-peak PL2 emission at 920 nm out of Cr3+ FM trimer in monolayer is seen; besides, the magnetic bi-polaronic PL3 at 990 nm can be assigned to Cr3+ tetramers between FM adjacent layers. In magnetic field perpendicular to the layer, direct competition between PL1and dark-state excitons and PL2 and PL3 excitonic states persist in different temperatures. This study sheds light on the complicated magneto-exciton interactions in the multi-body effect of CrSBr, beneficial for quantum modulation in layered magnetic semiconductors.

cond-mat.mtrl-sci↗

arXiv2024

Intrinsic Orbital Angular Momentum Originated from Optical Catastrophe Superposition

Conventionally, intrinsic orbital angular momentum (OAM) is associated with phase vortices. However, our investigation into the propagation dynamics of 2D superimposed catastrophe beams, termed cyclone catastrophe beams (CCBs), reveals that these beams inherently exhibit rotation and possess OAM, distinct from the typical connection to phase vortices. Our observations clearly show these beams rotating during autofocusing propagation and particle manipulation, confirming the presence of OAM. Theoretical calculations affirm that the OAM of these beams is intrinsic and can be adjusted by varying the number of superimposed beams. Furthermore, our interference and phase studies indicate that, although CCBs exhibit phase vortices, they do not rotate around the singularities of phase vortices and their total topological charges are zero. This implies that the manifestation of OAM within CCBs does not rely on nonzero topological charge of the presented phase vortices within CCBs. Especially, eigenstates decomposition analysis illustrates that CCBs can be decomposed as a composite of Laguerre-Gaussian (LG) modes with uneven fidelity, where the topological charges of LG modes align with multiples of the superimposed catastrophe beams but do not equal to the value of the OAM per photon within CCBs, emphasizing the intrinsic OAM within CCBs and the absence of a connection to phase vortices. Our findings not only advance the understanding of the relationship between OAM and phase vortices but also pave the way for different applications of OAM waves, catalyzing their development in optics and other domains.

physics.optics↗

arXiv2023

Statistics of tens-of-photon states scattered by optical cavity, two-level atom and Jaynes-Cummings emitter

Manipulating photon states serves as a primary requirement for various optical devices and is of high relevance for quantum information technology. Nevertheless, the fundamental theoretical framework for tens-of-photon states has not been established. This study successfully establishes the matrix-product-state theory to explore the statistics of the tens-of-photon states scattered by optical cavities (OCs), two-level atoms (TLAs), and Jaynes-Cummings emitters (JCEs) in waveguide-QED systems. Taking 10-photon states as an example, we reveal some novel physical results that differ from those for few-photon cases. We verify that OCs do not change the statistics of the incident photon states, being independent of the photon number. However, for the TLAs and JCEs, the photon number strongly impacts the photon bunching and anti-bunching behaviors. As the photon number increases, there exists a maximum strength for the photon-photon correlation induced by the JCE. Especially, the scattered waves by the TLA (or JCE) exhibit extremely different statistics behaviors for the 10-photon cases from those for the bi-photon. These distinguishable conclusions for the tens-of-photon states and the matrix-product-state theory pave the way for the multi-photon manipulation.

physics.optics↗

arXiv2023

All-Dielectric Structural Coloration Empowered by Bound States in the Continuum

The technological requirements of low-power and high-fidelity color displays have been instrumental in driving research into advanced coloration technologies. At the forefront of these developments is the implementation of dye-free coloration techniques, which overcome previous constraints related to insufficient resolution and color fading. In this context, resonant dielectric nanostructures have emerged as a promising paradigm, showing great potential for high efficiency, remarkably high color saturation, wide gamut palette, and realistic image reproduction. However, they still face limitations related to color accuracy, purity, and simultaneous brightness tunability. Here, we demonstrate an all-dielectric metasurface empowered by photonic bound states in the continuum (BICs), which supports sharp resonances throughout the visible spectral range, ideally suited for producing a wide range of structural colors. The metasurface design consists of titanium dioxide (TiO2) ellipses with carefully controlled sizes and geometrical asymmetry, allowing versatile and on-demand variation of the brightness and hue of the output colors, respectively.

physics.optics↗

arXiv2023

Robust autofocusing propagation in turbulence

We conducted a comprehensive study on the robust propagation of the same spot-size Gaussian beam (SSGB), same envelope Gaussian beam (SEGB), Circular Airy beam (CAB) and Circular Pearcey beam (CPB) in complex environments. Our findings clearly demonstrate that autofocusing beams exhibit higher stability in propagation compared with the Gaussian beams. To validate our results, we statistically analyze the intensity fluctuation of autofocusing beams and Gaussian beams. The analysis reveals that the intensity fluctuations of autofocusing beams are significantly smaller than that of Gaussian beams. Furthermore, we study the variation of the coherence factor and find that the coherence of autofocusing beams is better than that of Gaussian beams under turbulence. Additionally, we observe the change of the scintillation index (SI) with the propagation distance z, and our results show that autofocusing beams exhibit less oscillation than Gaussian beams, indicating that autofocusing beams propagate in complex environments with less distortion and fewer intensity fluctuation. Overall, our results suggest that autofocusing beams are promising for applications such as optical trapping and manipulation in complex environments. Our study provides valuable insights into the selection of stable beams that exhibit high intensity and high field gradient at the focal position in complex environments.

physics.optics↗

arXiv2023

Caustic analysis of partially coherent self-accelerating beams: Investigating self-healing property

We employed caustic theory to analyze the propagation dynamics of partially coherent self-accelerating beams such as self-healing of partially coherent Airy beams. Our findings revealed that as the spatial coherence decreases, the self-healing ability of beams increases. This result have been demonstrated both in simulation and experiment. This is an innovative application of the caustic theory to the field of partially coherent structured beams, and provides a comprehensive understanding of self-healing property. Our results have significant implications for practical applications of partially coherent beams in fields such as optical communication, encryption, and imaging.

physics.optics↗

arXiv2023

Controllable nonlinear propagation of partially incoherent Airy beams

The self-accelerating beams such as the Airy beam show great potentials in many applications including optical manipulation, imaging and communication. However, their superior features during linear propagation could be easily corrupted by optical nonlinearity or spatial incoherence individually. Here we investigate how the interaction of spatial incoherence and nonlinear propagation affect the beam quality of Airy beam, and find that the two destroying factors can in fact balance each other. Our results show that the influence of coherence and nonlinearity on the propagation of partially incoherent Airy beams (PIABs) can be formulated as two exponential functions that have factors of opposite signs. With appropriate spatial coherence length, the PIABs not only resist the corruption of beam profile caused by self-focusing nonlinearity, but also exhibits less anomalous diffraction caused by the self-defocusing nonlinearity. Our work provides deep insight into how to maintain the beam quality of self-accelerating Airy beams by exploiting the interaction between partially incoherence and optical nonlinearity. Our results may bring about new possibilities for optimizing partially incoherent structured field and developing related applications such as optical communication, incoherent imaging and optical manipulations.

physics.optics↗

arXiv2021

Exceptional points in a topological photonic system

Exceptional points as branch singularities describe peculiar degeneracies of non-Hermitian systems that do not obey energy conservation. This work shows that exceptional points can emerge in a topological photonic system, for example, the topological photonic waveguide coupled with two degenerate counter-propagation topological whispering gallery modes. Such a photonic architecture is designed by crystal-symmetry-protected topological photonic insulators based on air rods in conventional dielectric materials. The relevant exceptional point reveals the breaking of the parity-time symmetry, reflected by the change of the transmission-dip number in the optical transmission spectra of the system. Achieving exceptional points in topological photonic systems possibly opens a new avenue toward robust optical devices with exceptional-point-based unique properties and functionalities.

physics.optics↗

arXiv2021

Topologically protected Fano resonance in photonic valley Hall insulators

Rapidly developing photonics brings many interesting resonant optical phenomena, in which the Fano resonance (FR) always intrigues researchers because of its applications in optical switching and sensing. However, its sensitive dependence on environmental conditions makes it hard to implement in experiments. We in this work suggest a topologically-protected FR based on the photonic valley Hall insulators, immune to the system impurities. The topologically-protected FR is achieved by coupling the valley-dependent topological edge states (TESs) with one double-degenerate cavity. The $δ$-type photonic transport theory we build reveals that this topological FR dates from the interference of the two transmissions that are attributed to the parity-odd cavity mode and the parity-even one. We confirm that the induced Fano line shape of the transmission spectra is robust against the bending domain walls and disorders. Our work may provoke exciting frontiers for manipulating the valley transport and pave a way for the topologically protected photonic devices such as optical switches, low-threshold lasers, and ultra-sensitive sensors.

physics.optics↗

arXiv2021

Ultrafast photomechanical transduction through thermophoretic implosion

Since the historical experiments of Crookes, the direct manipulation of matter by light has been both a challenge and a source of scientific debate. Here we show that laser illumination allows to displace a vial of nanoparticle solution over centimetre-scale distances. Cantilever-based force measurements show that the movement is due to millisecond long force spikes, which are synchronised with a sound emission. We observe that the nanoparticles undergo negative thermophoresis, while ultrafast imaging reveals that the force spikes are followed by the explosive growth of a bubble in the solution. We propose a mechanism accounting for the propulsion based on a thermophoretic instability of the nanoparticle cloud, analogous to the Jeans instability that occurs in gravitational systems. Our experiments demonstrate a new type of laser propulsion, and a remarkably violent actuation of soft matter, reminiscent of the strategy used by certain plants to propel their spores.

cond-mat.soft↗

arXiv2019

Transport tuning of photonic topological edge states by optical cavities

Crystal-symmetry-protected photonic topological edge states (PTESs) based on air rods in conventional dielectric materials are designed as photonic topological waveguides (PTWs) coupled with side optical cavities. We demonstrate that the cavity coupled with the PTW can change the reflection-free transport of the PTESs, where the cavities with single mode and twofold degenerate modes are taken as examples. The single-mode cavities are able to perfectly reflect the PTESs at their resonant frequencies, forming a dip in the transmission spectra. The dip full width at half depth depends on the coupling strength between the cavity and PTW and thus on the cavity geometry and distance relative to the PTW. While the cavities with twofold degenerate modes lead to a more complex PTES transport whose transmission spectra can be in the Fano form. These effects well agree with the one-dimensional PTW-cavity transport theory we build, in which the coupling of the PTW with cavity is taken as $δ$ or non-$δ$ type. Such PTWs coupled with side cavities, combining topological properties and convenient tunability, have wide diversities for topological photonic devices.

physics.optics↗

arXiv2017

Excitation of exciton-polariton vortices in pillar microcavities by a Gaussian beam

With coupled Gross-Piteavskii equations we study excitation of exciton-polariton vortices and antivortices in a pillar microcavity by a Gaussian pump beam. The structure of vortices and antivortices shows a strong dependence on the microcavity radius, pump geometry, and nonlinear exciton-exciton interaction. Due to the nonlinear interaction the strong Gaussian beam cannot excite more polariton vortices or antivortices with respect to the weak one. The calculation demonstrates that the weak Gaussian beam can excite vortex-antivortex pairs, vortices with high angular momentum, and superposition states of vortex and antivortex with high opposite angular momentum. The pump geometry for the Gaussian beam to excite these vortex structures are analyzed in detail, which holds a potential application for Sagnac interferometry and generating the optical beams with high angular momentum.

physics.optics↗

arXiv2016

EMP Lasing from Mn doped lead bromide perovskites nanorods

Diluted magnetic semiconductor (DMS) nanostructures are promising platform to modulate carriers and spins for new information devices. Here we report that the high quality pure CH3NH3PbBr3 nanorods and Mn doped CH3NH3PbBr3 nanorods have been prepared by solution method and in which the exciton magnetic polarons (EMP) formed in Mn doped NRs, and a single mode lasing phenomenon from collective EMP in single NR have been detected when excited by fs pulse laser. This finding helps to understand the exciton and spin interactions and pave ways to the realization of new type of bosonic laser.

cond-mat.mes-hall↗

arXiv2015

Suppression of space broadening of exciton polariton beams by Bloch oscillation effects

We theoretically study the transport of exciton polaritons under different applied photon potentials. The relation between the photon potentials and the thickness of the cavity layer is calculated by the finite element simulation. The theoretical analysis and numerical calculation indicate that the cavity photon potential is proportional to the thickness of the cavity layer with the coefficient being about $1.8$ meV/nm. Further, the periodic and linear photon potentials are considered to control the transport of the exciton polaritons in weak- and strong-field pump situations. In both situations the periodic potential cannot by itself effectively suppress the scatterings of the disorder potentials of the cavity photons and excitons and the nonlinear exciton-exciton interaction. When the linear potential is added to the cavity photons, the polariton transport exhibits the Bloch oscillation behavior. Importantly, the polariton Bloch oscillation can strongly suppress the space broadening due to the disorder potentials and nonlinear exciton-exciton interaction, which is beneficial for designing the polariton circuits.

physics.optics↗

arXiv2015

Transmission comb of a distributed Bragg reflector induced by two surface dielectric gratings

With transfer matrix theory, we study the transmission of a distributed Bragg reflector (DBR) with two dielectric gratings on top and on the bottom. Owing to the diffraction of the two gratings, the transmission shows a comb-like spectrum which red shifts with increasing the grating period during the forbidden band of the DBR. The number density of the comb peaks increases with increasing the number of the DBR cells, while the ratio of the average full width at half maximum (FWHM) of the transmission peaks in the transmission comb to the corresponding average free spectral range, being about 0.04 and 0.02 for the TE and TM incident waves, is almost invariant. The average FWHM of the TM waves is about half of the TE waves, and both they could be narrower than 0.1 nm. In addition, the transmission comb peaks of the TE and TM waves can be fully separated during certain waveband. We further prove that the transmission comb is robust against the randomness of the heights of the DBR layers, even when a 15\% randomness is added to their heights. Therefore, the proposed structure is a candidate for a multichannel narrow-band filter or a multichannel polarizer.

physics.optics↗

arXiv2014

Nonlocal coupling effects on single-photon transmission in a one-dimensional waveguide interacted with a side optical cavity

The nonlocal coupling effect between a one-dimensional waveguide (1DW) and a side optical cavity (SOC) is studied. We first find the real-space Hamiltonian of the nonlocal-coupling system of the 1DW and SOC, and then derive out an equation determining the energy of the hybridization state between the 1DW and SOC modes and an analytic formula for the single-photon transmission. Through them, we recognize that the single-photon transmission-dip position can be changed by adjusting the SOC size and the coupling strength between the 1DW and SOC. The transmission spectra strongly depends on the nonlocal-coupling function between the 1DW and SOC, and holds an asymmetry line shape. At last, we simulate the asymmetry of the single-photon transmission by a gold-based waveguide coupled with a rectangular SOC.

physics.optics↗