Mid-IR broadened-waveguide and angled-grating distributed feedback (α-DFB) "W" quantum well lasers

Abstract

There is a growing demand for midwave-infrared (3-5 /spl mu/m) laser diodes operating in CW mode at non-cryogenic temperatures, for chemical sensing and other applications requiring low cost and portability. While optically-pumped mid-IR lasers recently achieved CW operation up to 290 K, previous III-V diodes emitting beyond 3 /spl mu/m have never operated CW above 180 K. In the presentation we report progress toward the goal of thermoelectrically (TE) cooled operation by using antimonide type-II W quantum well (QW) diodes, and also high-power/high-brightness using optically-pumped angled-grating distributed feedback (/spl alpha/-DFB) lasers with W active regions. The InAs(l5/spl Aring/)/Ga/sub 0.75/In/sub 0.25/Sb(27/spl Aring/)/InAs(15/spl Aring/)/AlGaAsSb(80/spl Aring/) W diode active region is designed to rely on light holes for the interwell tunneling transport rather than heavy holes. Another key design element is the insertion of relatively thick (0.6 /spl mu/m-thick) undoped AlGaAsSb separate confinement heterostructure (SCH) layers on each side of the active region. By increasing the mode overlap with the core, this broadened waveguide configuration maximizes the optical confinement factor in the active region with 5 or 10 quantum wells while minimizing free-carrier absorption losses in the doped AlGaAsSb cladding layers.