Abstract

Brillouin two-beam coupling has been used to achieve gains as high as 10⁹.¹ For a given input signal power there is a maximum pump extraction efficiency, and therefore an upper limit to the attainable gain for a given pump power.² For example, for a 0.1 mW input signal the maximum experimental efficiency is about 2%, so that for a pump power of 20 MW the maximum gain is 4 × 10⁹. The cause of this efficiency limitation is the presence of spontaneously scattered noise at the Stokes-shifted frequency. This noise arises from scattering of the pump light by acoustic fluctuations in the medium and will be amplified by the same factor as the input signal. In this work we present a system that can overcome this limitation and achieve higher efficiency and gain.

© 1994 IEEE