Optical frequency-comb generation in phase-locked random lasers using MAPbI3 nanocrystals

Abstract

Optical frequency-comb (OFC) generation provides an important tool for absolute optical frequency measurement, precision spectroscopy, quantum manipulation, and remote clock synchronization. Third-order optical nonlinear interaction between light waves and microcavities is an effective approach for OFC generation, where optical Kerr effect-based self-phase modulation and four-wave mixing (FWM) are the main mechanisms. However, OFC generation has never been observed in random-lasing (RL) systems, since the basic optical mechanisms were absent in such strong scattering and low energy-confinement schemes. Our achievements in the phase-locking of random lasers solved this challenge, and we report here OFC generation along with the phase-locked random lasing in microdisk patterns of MAPbI₃, where each microdisk consists of nanocrystalline particles randomly distributed in shape and size. Cascaded FWM around each of the phase-locked RL lines generated a series of sidelines, forming equally distributed OFC teeth in an extended spectral band. The number and the spectral separation of the OFC teeth exhibit strong dependence on the pump fluence, confirming both the phase-locking and cascaded FWM mechanisms. This study not only explores nonlinear photophysics and applications of halide perovskites, but also makes significant contribution to the development of random lasing and OFC-generation physics, enabling potentially on-chip integration of OFC devices without complicated designs of microcavities.