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Continuous-wave operation of a mid-infrared (~3.3 µm) interband cascade laser has been demonstrated at temperatures up to 264 K. The laser has also been operated continuously with a thermoelectric cooler near 260 K for more than 1900 h without observable degradation.
Mid-infrared (IR) interband cascade (IC) lasers take advantage of the broken bandgap alignment in Sb-based type-II quantum wells to reuse injected electrons in cascade stages for photon generation [1] with high quantum efficiency. Unlike intraband quantum cascade (QC) lasers [2], type-II IC lasers use interband transitions for photon emission without involving fast phonon scattering, making it possible to achieve very low threshold current density (e.g. < 10 A/cnr at 80 K, M00-200 A/cnr at 300 K). In addition, type-II IC lasers offer a wide wavelength tailoring without being limited by the conduction-band offset in the wavelength range of 3-4 mm where there are hydrocarbon signatures important for life detection in space exploration. Furthermore, theore- tical calculations [3, 4] project the feasibility of type-II IC lasers to operate in continuous-wave (CW) mode up to room temperature with high optical output power. Although significant progress [5-8] has been achieved towards such theoretical projections, the amount of effort expended in developing IC lasers is very limited compared to other semiconductor lasers such as InP- and GaAs-based QC lasers. There- fore their performance is still far from the theoretical projections. Since IC lasers have relatively high thermal resistivity (~10 K * cm2=kW), up to now their CW operation temperature has been limited to 237 K [7]. Here we report om recent progress in achieving CW operation of rnid-IR IC lasers operating in 3.3 mm at temperatures up to 264 K. In addition, we report initial reliability testing results of these lasers mounted on a thermoelectric (TE) cooler.
The type-II IC laser was grown in a solid-source Applied-EPI Gen-III molecular beam epitaxy (MBE) system on an undoped p-type GaSb substrate and has 12 cascade stages with a similar structure as the laser...