Reconfigurable symmetry-broken laser in a symmetric microcavity

Abstract

The coherent light source is one of the most important foundations in both optical physics studies and applied photonic devices. However, the whispering gallery microcavity, as a prime platform for novel light sources, has the intrinsically chiral symmetry and severely rules out access to directional light output, all-optical flip-flops, efficient light extraction, etc. Here, we demonstrate a reconfigurable symmetry-broken microlaser in an ultrahigh-Q whispering gallery microcavity with the symmetric structure, in which a chirality of lasing field is empowered spontaneously by the optical nonlinear effect. Experimentally, the ratio of counter-propagating lasing intensities is found to exceed 160:1, and the chirality can be controlled dynamically and all-optically by the bias in the pump direction. This work not only presents a distinct recipe for coherent light sources with robust and reconfigurable performance, but also opens up an unexplored avenue to symmetry-broken physics in optical micro-structures.

Low-threshold topological nanolasers based on the second-order corner state

“…The currently designed topological lasing systems are almost at the microscale, leading to large thresholds, which are usually approximately several milliwatts. In contrast, topological nanolasers can combine the advantages of topological robustness and nanolasers, including a small footprint, a low threshold, and a high energy efficiency [24][25][26][27][28][29][30][31] , but are still lacking except for the scheme using the 0D interface state in the 1D photonic beam with a threshold of approximately 46 μW 19 .…”

Phosphorus(III)-assisted regioselective C–H silylation of heteroarenes

“…In 2010, the C7-selective C–H borylation of indole was uncovered through iridium catalysis with the assistance of N -silyl-directing group 50 . Our group 51 , 52 and Ingleson group 53 have reported the chelation-assisted C–H borylation mediated by BBr 3 , in which the installation of a pivaloyl group at the N1 position of indole selectively brings the boron species to the C7 position and allows subsequent C–H borylation in an efficient manner (Fig. 1c ).…”

Single-mode characteristic of a supermode microcavity Raman laser

“…Single microcavities supporting high-Q whispering-gallery modes (WGMs) (17)(18)(19) are found as a natural platform for studying supermodes, which are formed by the coupling between degenerate counterpropagating waves (20)(21)(22). So far, supermode lasers in WGM microcavities have been demonstrated with not only intrinsic gain materials (3,7,(12)(13)(14), but also nonlinear optical effects, e.g., stimulated scattering (2,8,9,11). In particular, the latter is advantageous for recording low linewidths (23)(24)(25), as well as neither a requirement of specific gain materials nor a limitation in operation frequencies (26)(27)(28)(29)(30).…”

“…Different from the conventional inversion lasers based on electronic transitions, stimulated scattering involving only bosonic modes is inherently immune from the spatial hole burning and holds a homogeneous gain (35)(36)(37)(38). Hence, energy in the pump field should be clamped at a fixed value once the lasing threshold is reached (24,39,40), leading to a single-mode lasing (2,6,23). However, beat notes are widely observed in supermode microlaser output during pump scanning, so that these lasers are generally regarded as dual-mode lasers (8,9,41).…”

“…The Raman microlaser is generated by optically pumping a WGM microcavity and propagates in both the clockwise (CW) and counterclockwise (CCW) directions (Fig. 1A) (2,26). The intracavity counterpropagating waves are coupled by a scatterer at the surface (8,9,21,42), which forms a pair of standing-wave supermodes, the symmetric a+ and antisymmetric a−, defined by the relative position between the mode distribution and the scatterer (Fig.…”