Ultrasonic-Refraction Shutter for Optical Maser Oscillators

Recent interest in the application of infrared and optical masers (lasers) for range measurement, surveillance, welding, and drilling has focused attention on the problem of obtaining high peak-power pulses of short duration and fast risetime from these quantum devices. Kerr cells, Pockel cells, rotating disks, and mirrors have been used as shutters in the past with varying degrees of success. In this paper, experiments are described that demonstrate an ultrasonic shutter suitable for obtaining giant pulses from a ruby optical maser by utilizing the refraction resulting from the passage of a plane-parallel light beam through an ultrasonic field whose wavelength is much larger than the width of the light beam. Amplitude, risetime, and pulse duration are comparable with the values reported utilizing a Kerr cell and superior to those reported for rotating mechanical shutters. In addition, the ultrasonic shutter can be utilized to synchronize the usually random output pulses of a ruby optical maser with the ultrasonic frequency.