The use of semiconductor laser diodes at low temperatures

The theoretical analysis and experimental research of possibility of using commercially available semiconductor laser diodes at low temperatures (down to the temperature of 50 K) has been performed in the paper. The relevance of this work is caused by the need to develop sensors for remote measurement of low temperatures on the basis of semiconductor laser emitters. To implement the idea some analysis of wavelength emitted by the semiconductor laser diode as a function of medium temperature has been made. Physical causes that determine this relationship have been discussed. It has been shown that the temperature coefficient of change of the band gap width is a key factor in determining the dependence of the wave length of the laser radiation from the medium temperature. The calculation of numerical values of the temperature coefficient of change of the band gap width for the studied semiconductor laser diodes has been performed. Comparison of the experimental results with the published data has been performed. The temperature coefficient of change of the band gap width for some diode brands has been determined experimentally. It has been shown that in the temperature range 130 ÷ 150 K there is a sharp change in the parameter being analyzed. It has been commented that further studies are needed in this direction to explain possible reasons for the observed effect. To determine the effect of temperature on the nature of the semiconductor laser diode emission spectrum the emission spectra at several temperatures have been measured. It has been shown that at a certain temperature the semiconductor laser diode can be operated in a single mode. It has been noted that the value of the temperature coefficient of change of the band gap width is maintained irrespective of the laser operation mode (single mode, multimode, spontaneous emission mode). The results of the research are relevant for analysis of the work of laser emitters at low operating temperatures.