We investigate spontaneous emission from a quantum emitter located within the mode volume of a microring resonator that features chiral exceptional points. We show that this configuration offers enough degrees of freedom to exhibit a full control to either enhance or suppress the emission process. Particularly, we demonstrate that the Purcell factor can be enhanced by a factor of two beyond its value in an identical microring operating at a diabolic point. Our conclusions, which are derived using a non-Hermitian Hamiltonian formalism, are confirmed by employing full-wave simulations of realistic photonic structures and materials. Our results offer a straightforward route to improve the performance of single photon sources using current photonics technology without the need for building optical resonators with ultrahigh quality factors or nanoscale volumes.
Planar microcavities allow the control and manipulation of spin-polarization, manifested in phenomena like the optical spin Hall effect due to the intrinsic polarization mode splitting. Here, we study a transparent microcavity with broken rotational symmetry, realized by aligning the optical axis of a uniaxial cavity material in the cavity plane. We demonstrate that the in-plane optical anisotropy gives rise to exceptional points in the dispersion relation, which occur pair-wise, are circularly polarized, and are cores of polarization vortices. These exceptional points are a result of the non-…
In a non-Hermitian optical system with loss and gain, an exceptional point (EP) will arise under specific parameters where the eigenvalues and eigenstates exhibit simultaneous coalescence. Here we report a dynamical switching of lasing behavior in a non-Hermitian system composed of coupled microcavities by modulating the EPs. Utilizing the effect of gain, loss and coupling on the eigenstates of coupled microcavities, the evolution path of the eigenvalues related to the laser emission characteristics can be modulated. As a result, the lasing emission property of the coupled cavities exhibits an…
Recently, presence of hidden singularities known as exceptional points (EPs) in non-Hermitian quantum systems has opened up a tremendous interest in different domains of physics owing to their unique unconventional physical effects. Effectively for such systems an EP appears as a fascinating topological defect where two mutually interacting eigenstates of the system coalesce. In this work, we report occurrence of EP via avoided crossing between coupled resonance states in an optical microcavity with spatially varying gain loss profile, an optical analogue of non-Hermitian system. With suitably…
Exceptional rings in nonlinear non-Hermitian planar optical microcavities: implementation, signal enhancement, and topology
Paderborn University（帕德博恩大学）；Wyant College of Optical Sciences, University of Arizona（亚利桑那大学怀特光学科学学院）；Department of Physics, University of Arizona（亚利桑那大学物理系）
Asymmetric microcavities supporting Whispering-gallery modes (WGMs) are of great significance for on-chip optical information processing. We define asymmetric microcavities on topologically curved surfaces, where the geodesic light trajectories completely reconstruct the cavity mode features. The quality factors of the lossy chaotic and island modes in flat cavities can be increased by up to ~200 times by the space curvature. Strong and weak coupling between modes of very different origins occur when the space curvature brings them into resonance, leading to a fine tailoring of the cavity phot…
Skyrmions in scalar fields of non-Hermitian optical microcavities: spontaneous formation, nonlinear control, and optical forces
Paderborn University（帕德博恩大学）；Wyant College of Optical Sciences, University of Arizona（亚利桑那大学怀亚特光学科学学院）；Department of Physics, University of Arizona（亚利桑那大学物理系）；University of Stuttgart（斯图加特大学）
Metal halide perovskites are materials that show unique characteristics for photovoltaics and light emission. Amplified spontaneous emission and stimulated emission has been shown with these materials, together with electroluminescence in light-emitting diodes and light-emitting transistors. An important achievement that combine stimulated emission and electroluminescence could be the fabrication of electrically driven metal halide perovskite lasers. In this work, the integration of metal halide perovskite light-emitting field-effect transistors with photonic microcavities is proposed. This ca…
Measured and calculated results are presented on the emission properties of a new class of emitters operating in the cavity quantum electrodynamics regime. The structures are based on high-finesse GaAs/AlAs micropillar cavities, each with an active medium consisting of a layer of InGaAs quantum dots and distinguishing feature of having substantial fraction of spontaneous emission channeled into one cavity mode (high-beta factor). This paper shows that the usual criterion for lasing with a conventional (low-beta factor) cavity, a sharp nonlinearity in an input-output curve accompanied by notice…
We present a general theory of spontaneous emission at exceptional points (EPs)---exotic degeneracies in non-Hermitian systems. Our theory extends beyond spontaneous emission to any light--matter interaction described by the local density of states (e.g., absorption, thermal emission, and nonlinear frequency conversion). Whereas traditional spontaneous-emission theories imply infinite enhancement factors at EPs, we derive finite bounds on the enhancement, proving maximum enhancement of 4 in passive systems with second-order EPs and significantly larger enhancements (exceeding $400\times$) in g…
We experimentally demonstrate the spontaneous synchronization and the exceptional point (EP) induced pulse generation mechanism in the breather complex. The breathing frequency and phase are found to be synchronized during the formation of a 9-breather assembled complex in a mode-locked fiber laser. The breathers are formed at exactly the time point of the complex's breathing frequency leaving or entering the subharmonic entrainment. Such new pulse generation mechanism should be related to the non-Hermitian EPs or the time translation symmetry breaking. The investigations of destroying and reb…
Exceptional points (EPs), singularities of non-Hermitian physics where complex spectral resonances degenerate, are one of the most exotic features of nonequilibrium open systems with unique properties. For instance, the emission rate of quantum emitters placed near resonators with EPs is enhanced (compared to the free-space emission rate) by a factor that scales quadratically with the resonance quality factor. Here, we verify the theory of spontaneous emission at EPs by measuring photoluminescence from photonic-crystal slabs that are embedded with a high-quantum-yield active material. While ou…
We first present a quasinormal mode (QNM) theory for coupled loss-gain resonators working near an exceptional point. Assuming linear media, which can be fully quantified using the complex pole properties of the QNMs, we show how the QNMs yield a quantitatively good model to a full dipole spontaneous emission response in Maxwell's equations at various spatial positions and frequencies (linear response). We also develop a highly accurate and intuitive QNM coupled-mode theory, which can be used to rigorously model such systems using only the QNMs of the bare resonators, where the hybrid QNMs of t…
Non-Hermitian Hamiltonians describing open systems can feature singularities called exceptional points (EPs). Resonant frequencies become strongly dependent on externally applied perturbations near an EP which has given rise to the concept of EP-enhanced sensing in photonics. However, while increased sensor responsivity has been demonstrated, it is not known if this class of sensor results in improved signal-to-noise performance. Here, enhanced responsivity of a laser gyroscope caused by operation near an EP is shown to be exactly compensated by increasing sensor noise in the form of linewidth…
We demonstrate general classifications of Riemann surface topology generated by multiple arbitrary-order exceptional points of quasi-stationary states. Our studies reveal all possible product permutations of holonomy matrices that describe a stroboscopic encircling of 2nd order exceptional points. The permutations turn out to be categorized into a finite number of classes according to the topological structures of the Riemann surfaces. We further show that the permutation classes can be derived from combinations of cyclic building blocks associated with higher-order exceptional points. Our res…
Transition of Photonic Dissipative Dynamics through the Exceptional Point
Ministry of Industry and Information Technology Key Lab of Micro-Nano Optoelectronic Information System, Guangdong Provincial Key Laboratory of Semiconductor Optoelectronic Materials and Intelligent Photonic Systems, Harbin Institute of Technology, Shenzhen（工业和信息化部微纳光电信息系统重点实验室，广东省半导体光电子材料与智能光子系统重点实验室，哈尔滨工业大学（深圳））；Pengcheng Laboratory（鹏城实验室）；Quantum Science Center of Guangdong-Hongkong Macao Greater Bay Area（粤港澳大湾区量子科学中心）；Collaborative Innovation Center of Extreme Optics, Shanxi University（极端光学协同创新中心，山西大学）；Heilongjiang Provincial Key Laboratory of Advanced Quantum Functional Materials and Sensor devices, Harbin Institute of Technology, Harbin（黑龙江省先进量子功能材料与传感器器件重点实验室，哈尔滨工业大学）
We propose a novel inverse-design method that enables brute-force discovery of photonic crystal (PhC) structures with complex spectral degeneracies. As a proof of principle, we demonstrate PhCs exhibiting third-order Dirac points formed by the \emph{accidental} degeneracy of modes of monopolar, dipolar, and quadrupolar nature. We show that under suitable conditions, these modes can coalesce and form a third-order exceptional point (EP3), leading to diverging Petermann factors. We show that the spontaneous emission (SE) rate of emitters at such EP3s, related to the local density of states, can …
Controlling gain and loss of coupled optical cavities can induce non-Hermitian degeneracies of eigenstates, called exceptional points (EPs). Various unconventional phenomena around EPs have been reported, and expected to incorporate extra functionalities into photonic devices. The eigenmode exactly under the EP degeneracy is also predicted to exhibit enhanced radiation. However, such responses have yet to be observed in on-chip lasers, because of both the limited controllability of their gain and loss and the lifting of degeneracy by pump-induced cavity detuning. Here, we report the first non-…
The past few years have witnessed growing interests in exceptional points (EPs) in various domains, including photonics, acoustics and electronics. However, EPs have mainly been realized based on the degeneracy of resonances of physical systems; distinct degeneracies occur relating to the absorption properties of waves, with distinct physical manifestations. Here we demonstrate this physically different kind of exceptional point, by engineering degeneracies in the absorption spectrum of optical microcavities with dissipation. We experimentally distinguish the conditions to realize a resonant E…
The photonic spin Hall effect (SHE), featured by a spin-dependent transverse shift of an impinging optical beam driven by its polarization handedness, has many applications including precise metrology and spin-based nanophotonic devices. It is highly desirable to control and enhance the photonic SHE. However, such a goal remains elusive, due to the weak spin-orbit interaction of light, especially for systems with optical loss. Here we reveal a flexible way to modulate the photonic SHE via exceptional points, by exploiting the transverse shift in a parity-time (PT) symmetric system with balance…
This paper theoretically and numerically studies the response characteristics of non-Hermitian resonant photonic systems operating near an exceptional point (EP), where two resonant eigenmodes coalesce. It is shown that a system near an EP can exhibit a non-Lorentzian frequency response, whose line shape and intensity strongly depend on the modal decay rate and coupling parameters for the input waves, unlike a normal Lorentzian response around a single resonance. In particular, it is shown that the peak intensity of the frequency response is inversely proportional to the fourth power of the mo…
Chiral exceptional bound states in the continuum: a higher-order singularity for on-chip control of quantum emission
School of Integrated Circuits, Harbin Institute of Technology (Shenzhen)（哈尔滨工业大学（深圳）集成芯片学院）；Key Laboratory of Quantum Materials and Devices of Ministry of Education, School of Physics, Southeast University（东南大学物理学院量子材料与器件教育部重点实验室）；Institute for Quantum Science and Technology, National University of Defense Technology（国防科技大学量子科学与技术研究院）
Two-mode coupling is very common and basic in optics. Recently, a lot more works are focusing on the optical mode coupling with gain and loss due to its tighter link to actual world. For a couple between one gain and one loss mode, by adjusting the coupling constant, the mode in the spectrum will at first stay then move after the constant passing some critical point. This phase transition can be explained by non-Hermitian PT phase transition theory.However, only few works research the spontaneous emission adjustment based on this procedure. It has a lot of promising utilization in on chip opti…
Exceptional points (EPs) are special parameter values of a non-Hermitian eigenvalue problem where eigenfunctions corresponding to a multiple eigenvalue coalesce. In optics, EPs are associated with a number of counter-intuitive wave phenomena, and have potential applications in lasing, sensing, mode conversion and spontaneous emission processes. For open photonic structures, resonant states are complex-frequency solutions of the Maxwell's equations with outgoing radiation conditions. For open dielectric structures without material gain or loss, the eigenvalue problem for resonant states can hav…
Purcell enhanced electroluminescence of a unipolar light emitting quantum device at 10 micron
Laboratoire de Physique de l’École normale supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université Paris Cité（巴黎高等师范学院物理实验室，ENS，巴黎文理研究大学，法国国家科学研究中心，索邦大学，巴黎西岱大学）；III-V Labs, a joint lab between Thales, Nokia and CEA（III-V 实验室，泰雷兹、诺基亚和CEA的联合实验室）；Laboratoire Matériaux et Phénomènes Quantiques, Université Paris Cité（材料与量子现象实验室，巴黎西岱大学）；Centre de Nanosciences et de Nanotechnologies, Université Paris-Saclay, CNRS（纳米科学与工程中心，巴黎萨克雷大学，法国国家科学研究中心）
Higher-order exceptional points unveiled by nilpotence and mathematical induction
NTT Research, Inc.（NTT研究所）；Nanophotonics Center, NTT, Inc.（NTT光子学中心）；NTT Basic Research Laboratories, NTT, Inc.（NTT基础研究中心）；Central Michigan University（中密歇根大学）；Department of Physics, Institute of Science Tokyo（东京科学大学物理学系）
Parity-Time ($\mathcal{PT}$) symmetry has become an important concept in the design of synthetic optical materials, with exotic functionalities such as unidirectional transport and non-reciprocal reflection. At exceptional points, this symmetry is spontaneously broken, and solutions transition from those with conserved intensity to exponential growth or decay. Here we analyze a quantum-photonic surface formed by a single layer of atoms in an array with light mediating strong cooperative many-body interactions. We show how delocalized collective excitation eigenmodes can exhibit an effective $\…
