Laser-interferometric Detectors for Gravitational Wave Background at 100 MHz : Detector Design and Sensitivity

TL;DR

This paper proposes a laser interferometer experiment to detect gravitational wave background at 100 MHz, identifying the most sensitive design and estimating achievable sensitivity with realistic parameters.

Contribution

It introduces a new experimental setup for 100 MHz GWB detection and compares detector designs, highlighting the synchronous recycling interferometer as most sensitive.

Findings

Synchronous recycling interferometer outperforms Fabry-Perot Michelson at 100 MHz

Estimated sensitivity surpasses previous indirect limits

Designs evaluated for realistic experimental parameters

Abstract

Recently, observational searches for gravitational wave background (GWB) have developed and given direct and indirect constraints on the energy density of GWB in a broad range of frequencies. These constraints have already rejected some theoretical models of large GWB spectra. However, at 100 MHz, there is no strict upper limit from direct observation, though the indirect limit by He4 abundance due to big-bang nucleosynthesis exists. In this paper, we propose an experiment with laser interferometers searching GWB at 100 MHz. We considered three detector designs and evaluated the GW response functions of a single detector. As a result, we found that, at 100 MHz, the most sensitive detector is the design, a so-called synchronous recycling interferometer, which has better sensitivity than an ordinary Fabry-Perot Michelson interferometer by a factor of 3.3 at 100 MHz. We also give the best sensitivity achievable at 100 MHz with realistic experimental parameters.