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.
Highlights
The coherent light source is one of the most important foundations in both optical physics studies and applied photonic devices
In summary, we have demonstrated a reconfigurable symmetrybroken microlaser in a symmetric ultrahigh-Q WGM microcavity, which is free from any delicate structure design
Note that the directional laser can be obtained by other mechanisms in semiconductors, depending on special properties of particular materials
Summary
The coherent light source is one of the most important foundations in both optical physics studies and applied photonic devices. Beyond the strategies by explicit symmetry breaking, the spontaneous symmetry breaking (SSB) of the counterpropagating optical field has been demonstrated recently in a passive microcavity[29,30], which holds potential to dynamically switch the direction of the propagating light. It is still elusive for the SSB of a laser field in an active microcavity due to the accompanying complex lasing dynamics. The chiral symmetry of the lasing emission is broken spontaneously by the microcavity-enhanced optical Kerr nonlinearity This SSB of the Raman laser occurs above a threshold of a few tens of microwatts, and the ratio of counter-propagating emission intensities exceeds 160:1. The chirality can be all-optically and dynamically controlled by a bi-directional pump, and the threshold power of the SSB is adjustable using a nanotip scatterer
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