Long wavelength interband cascade lasers on GaSb substrates

Abstract

Interband Cascade Lasers (ICLs) are semiconductor laser sources emitting photons in the mid-infrared wavelength region. In the GaSb material system, ICLs cover the ~2.7 µm to ~5.6 µm wavelength range operating in continuous wave mode. In this spectral region, the low power consumption of ICLs is unrivaled compared to diode lasers and quantum cascade lasers emitting in this region. Many important gases like hydrocarbons have strong absorption lines in this wavelength region. ICLs are therefore suitable for gas sensing applications like tunable laser absorption spectroscopy (TLAS) for the detection of various gases. ICLs combine the cascading of active stages from quantum cascade lasers with interband transitions of diode lasers enabled by the semimetallic interface between InAs and GaSb. Beyond 5.6 μm important gases like nitrogen oxides have strong absorption lines making long wavelength GaSb ICLs interesting. We show the realization of long wavelength emitting ICLs optimized by reducing the number of electron injector quantum wells and improving doping in the active region, increasing thicknesses of the separate confinement layer and cladding layer. The devices emit at 5.72 μm and 6.00 μm, with pulsed mode characteristic temperatures of 47 K and threshold current densities of 1194 A/cm2 and 778 A/cm2 with voltage drops of 1.29 V and 1.33 V respectively.