On-chip Mach-Zehnder interferometer for 1550 nm laser frequency stabilization

Low-noise stable lasers have broad applications in metrology, spectroscopy, communication, and quantum physics. Here we demonstrate locking a semiconductor laser to an on-chip silicon nitride Mach-Zehnder interferometer (MZI) using the Pound-Drever-Hall (PDH) stabilization technology. After locking, the frequency noise of the laser is suppressed by up to 37 dB, and the relative stability reaches 3 × 10^-10 at a gate time of 1 ms, showing an order of magnitude improvement compared to a free-running operation. In addition, the linewidth of the stabilized laser is 420 kHz at an integration time of 10 ms, narrowed by eight times.