Al0.45Ga0.55As/GaAs-based single-mode distributed-feedback quantum-cascade lasers with surface gratings

Conditions of fabrication of first order distributed-feedback surface gratings designed for single-mode Al0.45Ga0.55As/GaAs quantum cascades lasers with the emission wavelength of about 10 mu m are presented. The 1 mu m-deep rectangular-shaped gratings with the period of about 1.55 mu m and duty cycle in the range of 65-71% made by the standard photolithography are demonstrated. The wavenumber difference of about 7 cm(-1) at 77 K is observed for the radiation emitted by lasers fabricated from the same epitaxial structure with ridge widths in the range of 15-25 mu m. Moreover, the emission wavelength of the lasers could be tuned with temperature at a rate of 1 nm/K in the temperature range of 77-120 K. The full width at half maximum of the emitted spectra is similar to 0.4 cm(-1).