Infrared and Visible Semiconductor Lasers

Abstract

In previous chapters we paid particular attention to GaAs and InGaAsP semiconductor lasers that emit light in the wavelength range of 0.8–1.6 µm in view of their important applications in optical data storage and optical fiber communications systems. However, longer-wavelength semiconductor lasers have also been of considerable interest and have found applications in molecular spectroscopy among other things, because of their large spectral tuning range. Figure 1.3 showed the wavelength range covered by various material systems. Of particular interest are the lead-salt semiconductor lasers covering a large spectral range (2.5–34 µm) in the far-infrared region. Since they are relatively well developed, the bulk of this chapter is devoted to their study. The last section of this chapter briefly mentions infrared and visible semiconductor lasers fabricated by using other material systems. The interest in lead-salt semiconductor lasers is generated by the wide range of emission wavelengths that can be obtained by varying the composition of the various constituents. Injection lasers of the ternary materials Pb1-x Sn x Te and PbS1-x Se x can provide emission wavelengths in the range of 3 µm to ~ 34 µm. The band gap of these materials also varies considerably with temperature; as a result, a large degree of spectral tuning can be obtained simply by varying the operating temperature.