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% to 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 to 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 to 120 K. The full width at half maximum of the emitted spectra is similar to 0.4 cm(-1). (C) 2017 Society of Photo-Optical Instrumentation Engineers (SPIE)