In1−xGaxP1−zAsz double-heterojunction-laser operation (77 °K, yellow) in an external grating cavity

Abstract

In_1−xGa_xP_1−zAs_z double‐heterojunction lasers fabricated by liquid‐phase epitaxy are operated at λ ≲6000 Å (77 °K) in an external grating cavity to provide wavelength‐selective optical feedback. Diodes with and without antireflecting coatings and with heterobarrier heights of ∼20, ∼65, and ∼90 meV are examined. With external grating feedback, laser operation occurs at reduced threshold current densities and narrower linewidths and, depending upon heterobarrier height, can be tuned over an appreciable wavelength range. Within certain tuning limits on either side of line center, the carrier recombination is drawn to the grating wavelength and, as in earlier work, laser operation on a homogeneously broadened line is observed. Beyond these limits, particularly for excitation just above the threshold of stimulated emission, laser operation on an inhomogeneously broadened line can be distinguished. These observations showing that homogeneous and inhomogeneous line broadening occur in a semiconductor laser are accounted for by a simple model of the recombination kinetics.