Highly Discriminative Amplification of a Single Frequency Comb Line

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. The optical power of a single line in optical frequency combs is inherently weak. The extraction and amplification of a single-frequency comb line are required for many high-precision applications. Highly discriminative amplification of a single comb line is achieved with a short polarization-maintaining fiber Brillouin amplifier for improved environmental stability, which generates the highest power, and best signal-to-noise ratio and side-mode-suppression ratio ever reported.image

Automated summary

This study introduces a high-gain, narrowband, all-polarization-maintaining fiber Brillouin amplifier to address the low power issue of single lines in optical frequency combs (OFCs). Numerical simulations and experiments are conducted to investigate the amplification process for an individual OFC line. The study demonstrates the direct generation of a Watt-level single-mode laser from an OFC, achieving the highest power, signal-to-noise ratio, and side-mode-suppression ratio reported to date.