A computer controlled frequency scanner for semiconductor laser

Abstract

A system is described for scanning the frequency of a semiconductor laser under the control of a computer. Simple commands from the computer can alter the rate and the direction of the scan, allowing the computer to control an experiment which requires a variable scan rate. An example is given where the semiconductor laser has been used to scan part of the methane absorption spectrum using a fast searching scan between absorption lines, and a slow scan through each line. The computer can also switch on a servo-control to lock the frequency of the laser to an absorption line, so that it is possible for the laser to be sequentially locked to a series of absorption lines providing a series of reference frequencies. The stability of the control system, when the laser is locked to a methane absorption line, is reported.