Quantum-enhanced laser phase noise filter

Quantum noise is the fundamental limit of laser phase noise filter. We cannot directly realize a quantum-enhanced phase noise suppression through the currently popular technologies, limited by a large number of technical noises as well as quantum noise penalty. It becomes the huge obstacle to implement the quantum-enhanced phase noise filter. Here, we propose an effective regime to experimentally demonstrate the first quantum-enhanced laser phase noise filter, by introducing a hybrid amplitude and phase noises stabilization scheme without the disturbing of current technologies limitations. We have addressed the primary influence factors in the extracting of laser phase noise, and made the quantum enhancement via squeezed vacuum injection feasible. Finally, a maximum of 5 dB quantum-enhanced phase noise filtering is experimentally realized across the Fourier frequencies from 5 to 60 kHz. The novelty scheme is more than just a proof-of-principle, and unlocks the squeezed vacuum enhanced laser phase noise suppression for various applications.