Some developments and applications of the optical lever

Abstract

The history of the optical lever is briefly reviewed from its invention by Poggendorf in 1826 to the recognition by Ising in 1926 of Brownian fluctuations of a galvanometer in the records obtained by Moll and Burger in 1925 with their thermoelectric relay. The design of optical levers and amplifiers by the author and his collaborators is outlined; these give sensitivities of the order 10-10 radian for a mirror 2.0 mm X 2.0 mm, and an observation bandwidth of 10 c/s. The effects of convection currents and photon fluctuations are indicated. The applications of optical levers to a range of measurements, including Brownian fluctuations, radiation pressure, linear expansion and infra-red detection are described. Optical and photoelectric systems similar to those developed for the optical lever can be used for alignment measurement; applications include refractometry for refractive index changes of order 10-9, and a test of the constancy of the velocity of light in a transverse magnetic field.