All-fiber random Kerr optical frequency combs

Optical frequency combs (OFCs) unite the electromagnetic spectrum coherently, and they can be realized in a number of different techniques, e.g., OFCs based on mode-locked lasers, electro-optic modulation of continuous-wave (CW) lasers, CW-pumped ring cavities such as micro-resonators, soliton formation and compression through modulation instability induced by dual-laser pumping, etc. Here, we introduce a different approach, achieving the first random Kerr OFC, the spectral-synthesized analog of a random laser. Based on modulation instability for simultaneous parametric amplification and temporal amplitude compression assisted by the distributed random feedback through Rayleigh scattering within a half-open cavity, trains of solitons are formed and further compressed leading to OFCs with spectral bandwidth over ~ 100 nm, wide comb spacing of ~ 1 nm, and minimum soliton duration of ~ 390 fs. The random Kerr OFC can operate continuously as a robust and flexible device, offering adjustable comb spacing, tunable soliton repetition rate, and tunable gate rate. Optical frequency combs, which consist of equidistant laser lines, can be formed by many well-established techniques. Here, authors generate a random Kerr optical frequency comb through the assistance of random feedback and the gain from modulation instability within an all-fiber configuration.