Interband cascade lasers

Appl. Phys. Lett. 106, 251102 (2015)

Interband cascade lasers (ICL) — devices in which injected electrons are reused in serially-cascaded active regions to generate multiple photons via interband transitions — are promising sources of mid-infrared light. An attraction of the design is that its efficiency and low drive current potentially make it suitable for battery-operated applications such as a chemical detector of methane. Lu Li and co-workers from University of Oklahoma have now demonstrated InAs-based ICLs at room temperature with record-breaking performance. To enhance the confinement factor of the generated light in the central GaInSb/InAs active cascade region, InAs/AlSb intermediate cladding layers with a smaller refractive index than that of the active cascade region were introduced to replace a portion of the undoped InAs space-confinement layers. The 10-μm-wide, 3.5-mm-long device lased in continuous-wave mode at temperatures up to 308 K near 4.85 μm. The lasing threshold current density was below 1 kA cm⁻². By introducing the intermediate cladding layer, the lasing performance in pulsed mode was also improved. The 2.0-mm-long device exhibited a threshold current density of 247 A cm⁻² at 300 K for emission near 4.6 μm, the lowest ever reported among mid-infrared semiconductor lasers at similar wavelengths. Another device lased in pulse mode at temperatures up to 377 K near 5.1 μm, the highest operating temperature reported for electrically pumped ICLs at this wavelength.