Tuning the radiation frequency of a mid-IR quantum cascade laser

The Fourier-transform spectroscopy method was used to measure the emission spectra of a pulsed quantum cascade laser in the 4.5 $\mu$m range and to demonstrate the tuning of the emission wavelength from 4.56 $\mu$m (2233.9 cm$^{-1}$) to 4.48 $\mu$m (2192.5 cm$^{-1}$) in a wide temperature range from 293 to 10 K.