Active region design for high power quantum cascade superluminescent emitters

Abstract

This work designs and characterizes a novel quantum cascade active region with a high dipole matrix element (34.7 Å) and a broad emission spectrum as a potential candidate for high power quantum cascade superluminescent (QCSL) emitters with a center wavelength of ~8 μm. Two designs, one with doping in the active region and the other with doping in the injector region, are investigated. Circular mesas are fabricated, measured, and compared with a standard ~8 μm laser design. Electroluminescence spectra measurements show that, compared to a standard laser design, the new design with doping in the active region exhibits a broader spectrum with a full width at half maximum (FWHM) of ~350 cm-1 at 300 K. In addition, at 300 K, with increased current, the FWHM of this design shows little gain narrowing in contrast to the standard laser design. This provides evidence that the spectral breadth of the active region doped design is maintained over different currents and that this design is a good candidate for high temperature and high power QCSL devices.