Suppressing ghost beams: Backlink options for LISA

K-S Isleif,K Danzmann,J Reiche,H Ward,J Livas,G Mueller,D Robertson,O Gerberding,D Penkert,E Fitzsimons,G Heinzel

doi:10.1088/1742-6596/840/1/012016

Abstract

In this article we discuss possible design options for the optical phase reference system, the so called backlink, between two moving optical benches in a LISA satellite. The candidates are based on two approaches: Fiber backlinks, with additional features like mode cleaning cavities and Faraday isolators, and free beam backlinks with angle compensation techniques. We will indicate dedicated ghost beam mitigation strategies for the design options and we will point out critical aspects in case of an implementation in LISA.

Highlights

The laser interferometer space antenna (LISA) consists of three spacecraft (S/Cs) forming an equilateral triangle in space [1, 2]
Due to orbital motion the angle between the laser links will change by ±1.5◦ and the arm length mismatch will reach a maximum deviation of the order of 1% over the period of one year
Experiments, comparing a fiber backlink connection with an ultra stable quasi-monolithic optical connection implemented on one optical bench (OB), have shown that a fiber-based phase reference distribution system (PRDS) is limited in its phase measurement by so called ghost beams that cause unwanted interferences

Summary

Introduction

The laser interferometer space antenna (LISA) consists of three spacecraft (S/Cs) forming an equilateral triangle in space [1, 2]. The candidates are based on two approaches: Fiber backlinks, with additional features like mode cleaning cavities and Faraday isolators, and free beam backlinks with angle compensation techniques. As consequence of implementing both, Telescope Pointing and TDI in LISA, two challenges need to be met: Firstly a flexible optical connection is required that provides the TX beam as local oscillator (LO) beam for the other OB.

Results

Conclusion