First demonstration of phase-sensitive gain stabilization by using heterodyne Costas optical phase-locked loop

Abstract

This study proposes a heterodyne Costas optical phase-locked loop (HC-OPLL) circuit for frequency nondegenerate optical parametric phase-sensitive amplification (ND-PSA) of phase-conjugated twin waves (PCTWs), and experimentally demonstrates stabilization of phase-sensitive gain in the ND-PSA by the HC-OPLL for the first time. First, theoretical derivation shows the proposed HC-OPLL circuit can correct phase error between PCTWs and a pump. Then, stabilization of phase-sensitive gain in ND-PSA of PCTWs with 42.3-GHz frequency spacing is experimentally demonstrated using the HC-OPLL circuit. The proof-of-principle experiment shows that gain fluctuations are reduced successfully through the use of HC-OPLL circuit.