Broadband linearly chirped light source with narrow linewidth based on external modulation

An external modulation method is proposed and experimentally demonstrated for the generation of linearly chirped light over broadband with narrow linewidth. Our chirped light source is a combination of an optical recirculating frequency shifter loop and an optical frequency linear sweeper. A linearly chirped light over a range of 200 GHz at a chirp rate of 3.6×1016 Hz/s is generated. The instantaneous linewidth of the chirped light is estimated to be less than 50 kHz.