The Advanced LIGO Input Optics

TL;DR

This paper describes the design, implementation, and testing of the input optics system for Advanced LIGO, enabling unprecedented sensitivity in gravitational wave detection by preparing laser beams with extreme precision.

Contribution

It introduces custom-designed input optics components tailored for Advanced LIGO's high sensitivity requirements, building on previous LIGO experience.

Findings

Components meet design specifications

Achieved sub-attometer beam preparation

Validated performance under operational conditions

Abstract

The Advanced LIGO gravitational wave detectors are nearing their design sensitivity and should begin taking meaningful astrophysical data in the fall of 2015. These resonant optical interferometers will have unprecedented sensitivity to the strains caused by passing gravitational waves. The input optics play a significant part in allowing these devices to reach such sensitivities. Residing between the pre-stabilized laser and the main interferometer, the input optics is tasked with preparing the laser beam for interferometry at the sub-attometer level while operating at continuous wave input power levels ranging from 100 mW to 150 W. These extreme operating conditions required every major component to be custom designed. These designs draw heavily on the experience and understanding gained during the operation of Initial LIGO and Enhanced LIGO. In this article we report on how the components of the input optics were designed to meet their stringent requirements and present measurements showing how well they have lived up to their design.