High-frequency broadband laser phase noise cancellation using a delay line

TL;DR

This paper demonstrates a fiber-loop delay line interferometer that effectively cancels high-frequency laser phase noise around 1.5 MHz, significantly improving noise reduction for advanced quantum and metrological experiments.

Contribution

It introduces a novel high-frequency phase noise cancellation method using a fiber-loop delay line, extending noise suppression capabilities to the 100 kHz–10 MHz range.

Findings

Achieved over 10 dB noise reduction at 1.5 MHz

Reduced phase noise to less than -160 dB (rad$^2$/Hz)

Effective for deep ground-state cooling of mechanical motion

Abstract

Laser phase noise remains a limiting factor in many experimental settings, including metrology, time-keeping, as well as quantum optics. Hitherto this issue was addressed at low frequencies, ranging from well below 1 Hz to maximally 100 kHz. However, a wide range of experiments, such as, e.g., those involving nanomechanical membrane resonators, are highly sensitive to noise at higher frequencies in the range of 100 kHz to 10 MHz, such as nanomechanical membrane resonators. Here we employ a fiber-loop delay line interferometer optimized to cancel laser phase noise at frequencies around 1.5 MHz. We achieve noise reduction in 300 kHz-wide bands with a peak reduction of more than 10 dB at desired frequencies, reaching phase noise of less than -160 dB (rad$^2$/Hz) with a Ti:Al$_2$O$_3$ laser. These results provide a convenient noise reduction technique to achieve deep ground-state cooling of mechanical motion.