Measurement and control of subangstrom displacement by acoustooptical techniques

Abstract

Control of laser mirror spacing and angular orientation is very important for laser frequency and mode stability. Interferometric methods have been used to measure such small displacements. For example, using a Mach-Zehnder interferometer, a stable He-Ne laser, and a frequency counter, submicrometer displacement can be measured. Because the Mach-Zehnder interferometer is very sensitive to mechanical vibration and misalignment, this technique is rather difficult, and expensive equipment, such as stable lasers and fast counters, is needed.