Tunable room-temperature continuous-wave mid-infrared VCSELs

Over the last two years, our group has reported the first room-temperature continuous-wave (RTCW) fixed wavelength VCSELs operating above 3 microns, in both optically pumped and electrically pumped devices. Our optically pumped 3.3um devices employ one or two wafer-bonded GaAs/AlGaAs mirrors, in conjunction with a type I InGaAsSb/AlInGaAsSb quantum well active region. Our electrically pumped 3.3um devices employ a bottom wafer-bonded GaAs/AlGaAs mirror, top deposited ZnSe/ThF4 mirror, and type II interband cascade (ICL) active region. These fixed wavelength devices lay a foundation for tunable devices in the spectrally rich 3-5um region. Narrowly tunable devices can use thermal tuning, by variation of pump power (optically pumped devices), bias current (electrically pumped devices), or device temperature (both electrically and optically pumped devices). In this paper, we describe tunable CW optically pumped devices with >4nm of tuning near 3.3um using variation of pump power. CW electrically pumped devices show similar to 2nm tuning near 3.3um using variation of bias current. These results are a critical first step towards an inexpensive and high-speed methane sensing source. A first generation of MEMS-tunable optically pumped devices has achieved 70nm tuning range near 3.34um.