Highly Discriminative Amplification of a Single Frequency Comb Line

Abstract The optical power of a single line in optical frequency combs (OFCs) is inherently weak, so the extraction and amplification of a single OFC line is required for many high‐precision applications. In this work, a high gain, narrowband, and all‐polarization‐maintaining (PM) fiber Brillouin amplifier is introduced to address this issue. The use of PM fiber as the gain medium provides higher Brillouin gain and avoids polarization sensitivity to thermal and acoustic disturbance. The gain fiber is reduced to tens of meters with higher pump power, which is beneficial for the phase quality of the amplified comb line. Numerical simulations and experiments are performed to investigate the features of the Brillouin amplification process for an individual OFC line. Notably, direct generation of a Watt‐level single‐mode laser from an OFC is demonstrated, with a signal‐to‐noise‐ratio (SNR) of 47 dB and a side‐mode‐suppression‐ratio (SMSR) exceeding 60 dB, which represents the highest power, and best SNR and SMSR performance ever reported, to the best of the knowledge.