Search for a Stochastic Background of 100-MHz Gravitational Waves with Laser Interferometers

Abstract

This Letter reports the results of a search for a stochastic background of gravitational waves (GW) at 100 MHz by laser interferometry. We have developed a GW detector, which is a pair of 75-cm baseline synchronous recycling (resonant recycling) interferometers. Each interferometer has a strain sensitivity of $\ensuremath{\sim}{10}^{\ensuremath{-}16}\text{ }\text{ }{\mathrm{Hz}}^{\ensuremath{-}1/2}$ at 100 MHz. By cross-correlating the outputs of the two interferometers within 1000 seconds, we found ${h}_{100}^{2}{\ensuremath{\Omega}}_{\mathrm{gw}}<6\ifmmode\times\else\texttimes\fi{}{10}^{25}$ to be an upper limit on the energy density spectrum of the GW background in a 2-kHz bandwidth around 100 MHz, where a flat spectrum is assumed.