Subjects: Optics >> Quantum optics submitted time 2023-02-19
Abstract： Strong coupling exhibits unique ability to preserve quantum sates between light and matter, which is essential for the development of quantum information technology. To explore the physical mechanism behind this phenomenon, we employ the tight-binding method for expanding the temporal coupled-mode theory, with the absorption spectrum formula of coupled system directly obtained in an analytical way. It reveals all the physical meaning of parameters defined in our theory, and shows how to tailor lineshapes of the coupled systems. Here, we set an example to manipulate the strong coupling in a hybrid structure composed of excitons in monolayer WS$_2$ and quasi-bound states in the continuum supported by the TiO$_2$ nanodisk metasurfaces. The simulated results show that a clear spectral splitting appeared in the absorption curve, which can be controlled by adjusting the asymmetric parameter of the nanodisk metasurfaces and well fitted through our theoretical predictions. Our work not only gives a more comprehensive understanding of such coupled systems, but also offers a promising strategy in controlling the strong light-matter coupling to meet diversified application requests.
Peer Review Status:
Awaiting Review
Subjects: Optics >> Quantum optics submitted time 2023-02-19
Abstract： We investigate the strong coupling between the excitons and quasi-bound states in the continuum (BIC) resonance in a bulk WS$_2$ metasurface. Here we employ the bulk WS$_2$ to construct an ultrathin nanodisk metasurface, supporting the symmetry-protected magnetic dipole (MD) quasi-BIC resonance, which can self-hybridize with the excitons and lead to a strong light-matter interaction enhancement within the structure without the necessity for an external cavity. This strong coupling can be charactered by the considerable Rabi splitting of 159 meV and the clearly anti-crossing behavior appeared in the absorption spectrum. Furthermore, we analyze such light-matter coupling by constructing a Hamiltonian model including the surplus excitons, and tune the interaction from weak coupling to strong coupling regimes via the tunability radiation loss of the quasi-BIC resonance. Our results have great potential for manipulating the exciton-polaritons at room temperature, and provide a promising prospect for photonic devices that exploit strong coupling in applications.
Peer Review Status:Awaiting Review
Subjects: Optics >> Quantum optics submitted time 2023-02-19
Abstract： The emerging all-dielectric platform exhibits high-quality ($Q$) resonances governed by the physics of bound states in the continuum (BIC) that drives highly efficient nonlinear optical processes. Here we demonstrate the robust enhancement of third-(THG) and fifth-harmonic generation (FHG) from all-dielectric metasurfaces composed of four silicon nanodisks. Through the symmetry breaking, the genuine BIC transforms into the high-$Q$ quasi-BIC resonance with tight field confinement for record high THG efficiency of $3.9\times10^{-4}$ W$^{-2}$ and FHG efficiency of $4.8\times10^{-10}$ W$^{-4}$ using a moderate pump intensity of 1 GW/cm$^{2}$. Moreover, the quasi-BIC and the resonantly enhanced harmonics exhibit polarization-insensitive characteristics due to the special $C_{4}$ arrangement of meta-atoms. Our results suggest the way for smart design of efficient and robust nonlinear nanophotonic devices.
Peer Review Status:Awaiting Review
Subjects: Optics >> Quantum optics submitted time 2023-02-19
Abstract： Enhancing absorption in optically thin semiconductors is the key in the development of high-performance optical and optoelectronic devices. In this paper, we resort to the concept of degenerate critical coupling and design an ultra-thin semiconductor absorber composed of free-standing GaAs nanocylinder metasurfaces in the near infrared. The numerical results show that perfect absorption can be achieved through overlapping two Mie modes with opposite symmetry, with each mode contributing a theoretical maximum of 50% in their respective critical coupling state. The absorption also shows the polarization-independent and angle-insensitive robustness. This work, together with the design concept, opens up great opportunities for the realization of high-efficiency metasurface devices, including optical emitters, modulators, detectors, and sensors.
Peer Review Status:Awaiting Review
Subjects: Optics >> Quantum optics submitted time 2023-02-19
Abstract： Optical metasurfaces enable to engineer the electromagnetic space and control light propagation at an unprecedented level, offering a powerful tool to achieve modulation of light over multiple physical dimensions. Here, we demonstrate a Sb$_{2}$S$_{3}$ phase-change metasurface platform that allows active manipulation of both amplitude and phase. In particular, we implement dynamic nanoprinting and holographic image display through tuning crystallization levels of this phase-change material. The Sb$_{2}$S$_{3}$ nanobricks tailored to function the amplitude, geometric and propagation phase modulation constitute the dynamic meta-atoms in the multiplexed metasurfaces. Using the incident polarizations as decoding keys, the encoded information can be reproduced into a naonprinting grayscale image in the near field and two holographic images in the far field. These images can be switched on and off by taking advantages of the reversible tunability of Sb$_{2}$S$_{3}$ nanostructure between amorphous and crystalline states. The proposed phase-change metasurfaces featuring manifold information and multifold encryption promise ultracompact data storage with high capacity and high security, which suggests an exciting direction for modern cryptography and security applications.
Peer Review Status:Awaiting Review
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