AOM-based ultra-low noise laser intensity control up to the MHz range

Abstract

High-power laser sources that exhibit low relative intensity noise and allow simultaneous dynamic control of their light level are required for a broad range of applications in various fields of physics. Acousto-optic modulators (AOMs) are widely used for active power stabilization and regulation due to their simple drive electronics requirements and high optical power handling capability in free-space. However, the rather slow propagation speed of the sound wave within the AOM crystal typically limits their control bandwidth to a few hundred kHz. In this work, we present a novel AOM-based control system that is capable of significantly suppressing intensity noise of high-power lasers up to the MHz range. By combining two standard feedback loops with one feedforward control branch and optimizing the beam path in the AOM crystal, ultra-low relative intensity noise levels down to $-155\, \text{dB}\,\text{Hz}^{-1}$ even at several hundred kHz are achieved. Our results are relevant for applications that require ultra-low intensity noise at Fourier frequencies up to the MHz range, such as optical lattice experiments with light ultracold atoms.