Supersonic Band Characteristics of Laser Microphone Using Self-coupling Effect of Semiconductor Laser

Abstract

In a conventional microphone, the diaphragm limits the detectable sound frequency range. To overcome this limitation, a laser microphone was developed using the self-coupling effect of a semiconductor laser. In this paper, the supersonic band characteristics of the laser microphone were investigated using a super tweeter. From the experiment results, it was observed that the optimum reflectivity of a reflector is almost 25% when the laser power is 25 mW. Moreover, a flat frequency response is achieved between 40 Hz and 150 kHz when the long diameter of the laser beam is 1.0 mm, and the upper limit of the detectable frequency relates to the long diameter of the laser beam.