Experimental demonstration of frequency downconverted arm length stabilization for a future upgraded gravitational wave detector

TL;DR

This paper demonstrates a novel arm-length stabilization scheme compatible with AlGaAs coatings, which can enhance the sensitivity of future gravitational wave detectors by reducing thermal noise.

Contribution

It introduces an innovative ALS method suitable for AlGaAs coatings, overcoming limitations of traditional frequency-doubled locking schemes.

Findings

Successful experimental demonstration of the new ALS scheme.

Compatibility of the scheme with AlGaAs coatings confirmed.

Potential for improved detector sensitivity with reduced thermal noise.

Abstract

Ground-based laser interferometric gravitational wave detectors consist of complex multiple optical cavity systems. An arm-length stabilization (ALS) system has played an important role in bringing such complex detector into operational state and enhance the duty cycle. The sensitivity of these detectors can be improved if the thermal noise of their test mass mirror coatings is reduced. Crystalline AlGaAs coatings are a promising candidate for this. However, traditional ALS system with frequency-doubled 532 nm light is no longer an option with AlGaAs coatings due to the narrow bandgap of GaAs, thus alternative locking schemes must be developed. In this letter, we describe an experimental demonstration of a novel ALS scheme which is compatible with AlGaAs coatings. This ALS scheme will enable the use of AlGaAs coatings and contribute to improved sensitivity of future detectors.