New method for residual amplitude modulation control in fibered optical experiments

TL;DR

This paper introduces a novel single-photodetector method for controlling residual amplitude modulation in fibered optical systems, overcoming limitations of previous techniques affected by polarization-dependent losses.

Contribution

A new method using a single photodetector for RAM control in fibered optical experiments, improving stability where prior methods faced polarization-related issues.

Findings

The new method effectively reduces RAM in fibered systems.

It outperforms previous techniques in polarization-dependent loss scenarios.

Demonstrated successful implementation in fibered optical setups.

Abstract

When locking the frequency of a laser to an optical cavity resonance, the residual amplitude modulation (RAM), which accompanies the phase modulation necessary to build the error signal, is a major limitation to the frequency stability. We show that the popular method demonstrated by Wong and Hall to cancel this effect, based on the measurement of the RAM using an auxiliary detector, is limited in the case of optical setups exhibiting polarization dependent losses and an imperfect polarizer at the modulator output, such as guided-wave optical systems. We propose and demonstrate a new method, using a single photodetector, to generate the two error signals and demonstrate its usefulness in the case of fibered systems.