Single-mode characteristic of a supermode microcavity Raman laser

Abstract

Microlasers in near-degenerate supermodes lay the cornerstone for studies of non-Hermitian physics, novel light sources, and advanced sensors. Recent experiments of the stimulated scattering in supermode microcavities reported beating phenomena, interpreted as dual-mode lasing, which, however, contradicts their single-mode nature due to the clamped pump field. Here, we investigate the supermode Raman laser in a whispering-gallery microcavity and demonstrate experimentally its single-mode lasing behavior with a side-mode suppression ratio (SMSR) up to 37 dB, despite the emergence of near-degenerate supermodes by the backscattering between counterpropagating waves. Moreover, the beating signal is recognized as the transient interference during the switching process between the two supermode lasers. Self-injection is exploited to manipulate the lasing supermodes, where the SMSR is further improved by 15 dB and the laser linewidth is below 100 Hz.

Ultralow‐Threshold and High‐Quality Whispering‐Gallery‐Mode Lasing from Colloidal Core/Hybrid‐Shell Quantum Wells

“…[ 32 ] However, NPLs‐whispering gallery mode (WGM) lasers with ultrahigh quality ( Q ) factor and extremely small mode volume, [ 33,34 ] in which the closed feedback loop is formed via total internal reflection in the boundaries of high refractive index cavity, are rarely studied. WGM microlasers, which can provide strong optical confinement and feature greatly enhanced light‐matter interactions, [ 35 ] have attracted wide attention and promoted various advances such as ultrahigh‐sensitivity sensing, [ 4,5,36–39 ] integrated optics, [ 40–42 ] nonlinear optics, [ 43,44 ] and novel coherent light source. [ 40,41 ] Besides, some quite interesting physical phenomena and mechanisms related to microlasers have also been studied, including structured light, [ 42 ] exceptional‐point, [ 43–45 ] near‐degenerate supermodes, [ 41 ] and so on.…”

“…WGM microlasers, which can provide strong optical confinement and feature greatly enhanced light‐matter interactions, [ 35 ] have attracted wide attention and promoted various advances such as ultrahigh‐sensitivity sensing, [ 4,5,36–39 ] integrated optics, [ 40–42 ] nonlinear optics, [ 43,44 ] and novel coherent light source. [ 40,41 ] Besides, some quite interesting physical phenomena and mechanisms related to microlasers have also been studied, including structured light, [ 42 ] exceptional‐point, [ 43–45 ] near‐degenerate supermodes, [ 41 ] and so on. Although coreless fiber‐assisted NPLs‐WGM laser has been demonstrated previously, unfortunately, the giant optical loss caused by the longitudinal freedom of the fiber results in the lasing threshold up to hundreds of µJ cm −2 and only multimode lasing action with prominent spontaneous emission background was presented, [ 27 ] which hinders their practical utilization.…”

Tale of Two Resonances: Waveguide–Plasmon Coupling and High Q-Factor Engineering on the Nanoscale

“…Although the noise in detection may offset the enhancement in frequency splitting for EP sensors under small perturbations, the sensing precision (i.e., signal-to-noise ratio) can be improved, for example, if operating near the lasing threshold. , In addition, employing the missing dimension of EPs, non-Hermitian lasing might be achieved in a hybrid system by harnessing directionality of the waveguide mode and the exciting light. This also generates novel chiral modes and opens up a new avenue for developing new light sources for photonic integrated devices. , The tale of two resonances continues.…”

“…This also generates novel chiral modes and opens up a new avenue for developing new light sources for photonic integrated devices. 110,111 The tale of two resonances continues.…”

Flexible Manipulation of Lasing Modes in an Erbium-Doped Microcavity via an Add–Drop Configuration

“…However, these proposed methods have disadvantages, such as sacrificed Q factors induced by the decreased cavity size or lack of flexibility. The ultrahigh- Q silica microcavity is a good candidate to achieve an ultralow-threshold and ultranarrow-linewidth laser. − Silica microbottle cavities have been given much attention and applied in various areas, such as cavity quantum electrodynamics, cavity optomechanics, microlaser, and so on. ,, There are rich WGMs and, thus, lasing modes that can be selectively excited in the microbottle cavity due to its parabolic profile. Since it has nondegenerate axial symmetrical modes, this makes optical gain shared by multiple lasing modes, which leads to optical instability due to mode competition .…”