Photonic Time Crystals (PTCs) - dielectric media with their refractive index modulated periodically in time, offer new opportunities in photonics arising from time reflections and momentum bandgaps. Here, we study the emission of light from a radiation source inside a PTC. We solve the general classical and quantum mechanical models of emission in a temporally-varying medium, and find that radiation is always exponentially amplified when associated with the momentum gap, whether initiated by a macroscopic source, an atom, or by vacuum fluctuations, drawing the amplification energy from the modulation. The radiation linewidth becomes narrower as time advances, and is centered in the middle of the momentum gap. We calculate the spontaneous decay rate of an atom embedded in a PTC and show that it vanishes at the band edge due to low density of photonic states. Finally, we propose the concept of nonresonant tunable PTC lasers.
Chalcogenide glass (ChG) is an attractive material for integrated nonlinear photonics due to its wide transparency and high nonlinearity, and its capability of being directly deposited and patterned on Silicon wafer substrates. It has a singular Raman effect among amorphous materials. Yet, the Raman lasing performance in high quality and chip integrated ChG microresonators remains unexplored. Here, we demonstrate an engineered Raman lasing dynamic based on home developed photonic integrated high-Q ChG microresonators. With a quality factor above 10^6, we achieve the record-low lasing threshold…
Line lasing in a two-dimensional lattice of orbital photonic resonators
Univ. Lille, CNRS, UMR 8523 – PhLAM – Physique des Lasers Atomes et Molécules（里尔大学，法国国家科学研究中心，UMR 8523 – 激光物理原子与分子物理实验室）；Université Paris-Saclay, CNRS, Centre de Nanosciences et de Nanotechnologies（巴黎萨克雷大学，法国国家科学研究中心，纳米科学与工程中心）
Recently, optical bound states in continuum in various passive photonic crystals have been identified and similar structures incorporated with optical gain have been reported to exhibit lasing. However, no explicit control over the type of lasing BIC has been reported. In this work, we utilize all four fundamental BICs related to the lowest energy Gamma-point of a square photonic crystal lattice. We identify the associated topological charges from experimentally obtained dispersions, finite element method simulations, as well as from spherical decomposition method based on the microscopic pola…
Analogs of spontaneous emission and lasing in photonic time crystals
Korea Advanced Institute of Science and Technology（韩国科学技术院）；University of California, Berkeley（加州大学伯克利分校）；Stanford University（斯坦福大学）；the Hong Kong University of Science and Technology（香港科技大学）；Chung-Ang University（中央大学）
Topological lasers are a new class of lasers that seek to exploit the special properties of topological states of light. A typical limiting factor in their performance is the existence of non-topological states with quality factors comparable to the desired topological states. We show theoretically that by distributing uniform gain and loss on two sublattices of a two-dimensional higher-order topological insulator (HOTI) lattice, single-mode lasing based on topological corner states can be sustained over a wide range of pump strengths. This behavior stems from the parity/time-reversal breaking…
Exceptional points, with simultaneous coalescence of eigen-values and eigen-vectors, can be realized with non-Hermitian photonic systems. With the enhanced response, exceptional points have been proposed to improve the performance of photonic sensing. Recently, there are intense debate about the actual sensing advantage of exceptional points. The major concern is that intrinsic noise is also amplified at exceptional points. Here, we aim to clarify the contribution of exceptional points for photonic sensing. This is achieved by analyzing the condition to realize divergent quantum Fisher informa…
Microwave vortex beam lasing via photonic time crystals
Key Laboratory of advanced optoelectronic quantum architecture and measurements of Ministry of Education, Beijing Key Laboratory of Nanophotonics & Ultrafine Optoelectronic Systems, School of Physics, Beijing Institute of Technology（教育部先进光电量子架构与测量重点实验室，北京纳米光子学与超精细光电系统北京市重点实验室，物理学院，北京理工大学）；Beijing Key Laboratory of Millimeter wave and Terahertz Techniques, School of Information and Electronics, Beijing Institute of Technology（毫米波与太赫兹技术北京市重点实验室，信息与电子学院，北京理工大学）
The ability to tune the wavelength of light emission on a silicon chip is important for scalable photonic networks, distributed photonic sensor networks and next generation computer architectures. Here we demonstrate light emission in a chip-scale optomechanical device, with wide tunablity provided by a combination of radiation pressure and photothermal effects. To achieve this, we develop an optically active double-disk optomechanical system through implantation of erbium ions. We observe frequency tuning of photoluminescence in the telecommunications band with a wavelength range of 520 pm, g…
We explore absorbing open-boundary modes in non-Hermitian photonic systems. The modes have a continuum spectrum in the infinite system-size limit and can exhibit the non-Hermitian skin effect. In contrast to the conventional non-Hermitian skin modes under the fixed-end open-boundary condition, the modes concerned exhibit a strongly size-dependent spectrum that gradually converges to the non-Bloch-band dispersion. The modes correspond to the poles of the $S$ matrix, and are closely related to the lasing. We demonstrate these properties in a two-dimensional non-Hermitian photonic crystal with ga…
Universidad Autónoma de Madrid（马德里自治大学）；Università di Padova（帕多瓦大学）；Wrocław University of Science and Technology（弗罗茨瓦夫科技大学）；EPFL（洛桑联邦理工学院）；Univ Rennes, INSA Rennes, CNRS, Institut FOTON – UMR 6082（雷恩大学、雷恩国立应用科学学院、法国国家科学研究中心、FOTON研究所）；Instituto Nicolás Cabrera, Universidad Autónoma de Madrid（尼古拉斯·卡布里拉研究所，马德里自治大学）；Instituto de Física de la Materia Condensada (IFIMAC), Universidad Autónoma de Madrid（凝聚态物理研究所（IFIMAC），马德里自治大学）
Amplified spontaneous emission is a source of broadband noise that parasitically limits the achievable gain in laser amplifiers. While optical bandpass filtering elements can suppress these broadband noise contributions, such filters are typically designed around specific frequencies or require manual tuning, rendering them less compatible with tunable laser systems. Here, we introduce a nonlinear self-adaptive filter and demonstrate the suppression of amplified spontaneous emission surrounding the lasing mode of a tunable 780 nm external cavity diode laser, using the two-beam coupling interac…
Topological Lasing from Thouless Pumping in Bilayer Photonic Crystal
Donostia International Physics Center（圣塞巴斯蒂安国际物理中心）；Chemistry Faculty (UPV/EHU)（巴斯克大学化学学院）；Brown University（布朗大学）；Institute for Basic Science (IBS)（韩国基础科学研究院）；Universität Siegen（锡根大学）；Ecole Centrale de Lyon（里昂中央理工学院）；INSA Lyon（里昂国立应用科学学院）；Université Claude Bernard Lyon 1（里昂第一大学）；CPE Lyon（里昂国家高等化工、物理、生物学院）；CNRS（法国国家科学研究中心）；IKERBASQUE, Basque Foundation for Science（伊克尔巴斯科奎，巴斯克科学基金会）
Hanbat National University（韩巴特国立大学）；Paul Scherrer Institute（保罗谢勒研究所）；École Polytechnique Fédérale de Lausanne (EPFL)（洛桑联邦理工学院）；IBM Research Europe – Zürich（IBM欧洲苏黎世研究中心）；Imperial College London（伦敦帝国学院）
The advance of topological photonics has heralded a revolution for manipulating light as well as for the development of novel photonic devices such as topological insulator lasers. Here, we demonstrate topological lasing of circular polarization in a polymer-cholesteric liquid crystal (P-CLC) superlattice, tunable in the visible wavelength regime. By use of the femtosecond-laser direct-writing and self-assembling techniques, we establish the P-CLC superlattice with a controlled mini-band structure and a topological interface defect, thereby achieving a low threshold for robust topological lasi…
