Terahertz Emission from HgCdTe QWs under Long-Wavelength Optical Pumping

Currently semiconductor lasers in the wavelength range from 20 to 60 μm are scarce. HgTe/CdHgTe heterostructures is a potential basis for alternative sources of coherent radiation in this range. We propose that in such structures carrier heating is the main mechanism, which quenches stimulated emission under high excitation intensity. Lower-energy optical excitation is one way to reduce this negative effect. We compare output power vs excitation intensity at pumping wavelengths of 2.3 and 10.6 μm. Comparison shows that longer wavelength leads up to 3 order of magnitude higher total output power at the same number of photons in pulse. At the same time, for structures designed for the wavelengths above 20 μm, the heating is observed even under 10.6 μm pumping. We debate excitation by quantum cascade lasers with low energy of photons to be the main route for further development of HgTe/CdHgTe sources for 20–60 μm wavelength range.