A novel concept for increasing the peak sensitivity of LIGO by detuning the arm cavities

TL;DR

This paper proposes using detuned arm cavities in LIGO to enhance shot noise limited sensitivity between 125 and 400 Hz without increasing light power, potentially offering a less hardware-intensive alternative to RSE.

Contribution

The paper introduces a novel detuning technique for LIGO's arm cavities that improves sensitivity in a specific frequency band, providing an alternative to traditional RSE configurations.

Findings

Sensitivity increased by up to 80% around 225 Hz

Improved sensitivity in the 125-400 Hz range

Comparable to conventional RSE with moderate reflectivity

Abstract

We introduce a concept that uses detuned arm cavities to increase the shot noise limited sensitivity of LIGO without increasing the light power inside the arm cavities. Numerical simulations show an increased sensitivity between 125 and 400 Hz, with a maximal improvement of about 80% around 225 Hz, while the sensitivity above 400Hz is decreased. Furthermore our concept is found to give a sensitivity similar to that of a conventional RSE configuration with a Signal-Recycling mirror of moderate reflectivity. In the near future detuned arm cavities might be a beneficial alternative to RSE, due the potentially less hardware intensive implementation of the proposed concept.