Generation of equidistant frequencies in a semiconductor laser with an external cavity

A cw semiconductor laser with external feedback provided by a diffraction g rating was investigated experimentally. The laser drive current was modulat ed at a frequency of 0.3 - 5 GHz, The spectrum of the output radiation cons isted of several equidistant frequencies and the intervals between these fr equencies were determined by the current-modulation frequency. Optimal cond itions were found for the generation of the maximum number of such frequenc y components. The maximum width of the spectrum was 48 GHz, A method was de veloped for measuring the difference frequencies in the optical range with the aid of such lasers.