Scientists demonstrate first mid-IR emission from a III-V vertical-cavity surface-emitting laser
Jerry Meyer and associates at the Naval Research Laboratory (NRL; Washington, DC) have demonstrated a III-V-materials-based optically pumped vertical-cavity surface-emitting laser (VCSEL) emitting in the mid-infrared (mid-IR) region. The grou¥claims it is the first such device demonstrated. "Previously, the only short-cavity VCSEL emitting beyond 1.7 µm was a French device at 2.35 µm that hasn`t been published yet and a mercury cadmium telluride (HgCdTe) device that emits at 3.06 µm, but only u¥to 30 K," says Meyer. Although designed by the NRL group, the 2.9-µm-output devices are made by Dave Chow at Hughes Research Laboratory (Malibu, CA) who grew the lasers on gallium antimonide (GaSb) substrates. They are fabricated with a bottom gallium antimonide/ aluminum arsenic antimonide (GaSb/AlAsSb) Bragg mirror, an indium arsenide/ gallium antimonide/indium arsenide/aluminum antimonide (InAs/GaSb/InAs/AlSb) type-II "W" active region, and a dielectric to¥mirror.
When pulsed, the laser operates at temperatures u¥to 280 K with a power-conversion efficiency of more than 1% at 220 K. "This is far higher than anything seen for edge emitters at this wavelength and temperature," notes Meyer. For CW operation, the device turns on at a threshold pum¥power of 4 mW and exhibits a 4.5% power conversion efficiency at 80 K. It operates u¥to 160 K, "already approaching the highest reported Tmax of 180 K for CW mid-IR edge-emitters." One obvious application for these devices is chemical sensing. Meyer projects that his grou¥will shortly achieve CW single-mode output at thermoelectric-cooler temperatures (>200 K).