Laser Phase Noise Measurement by Using Offset Optical Phase Locked Loop

Phase noise is a key parameter to evaluate the short-term stability of a single-frequency laser. It is of great important for many applications, such as Lidar, coherent optical communication, optical sensing, and optical atomic clock, just to name a few. In this paper, we propose a method to characterize the phase noise of a single-frequency, which based on an offset phase locked loop (OPLL). The phase of the laser under test and a low noise reference laser are locked via an offset OPLL. The phase noise of the laser under test can be extracted by the beat-note of the two lasers. Experimentally, we achieve the phase noise of a narrow-linewidth laser, which agree well with the results of a commercial optical noise analyzer.