Resonant cavity interband cascade light emitting devices with record spectral intensity

Interband cascade light emitting devices (ICLEDs) emitting in the midwave infrared (MW) employ the same active stages stacked in series as interband cascade lasers (ICLs), but without a cavity that provides sufficient optical feedback for lasing. The resulting spectral bandwidth is quite broad, typically ≈ 0.5-1.5μm. However, in this work we dramatically narrow the linewidth by placing the active stages between top and bottom distributed Bragg reflectors (DBRs) to form a resonant cavity ICLED with design similar to that of recent resonant cavity infrared detectors (RCIDs). The ICLED wafer was grown at NRL with 20 active stages designed for peak emission near 4.5μm. Praevium bonded the chip to a 33-period GaAs/AlGaAs DBR, and then deposited a single-period Ge/SiO2 DBR as the top mirror. For continuous wave operation at 25°C, most of the emission falls within the resonance feature with center wavelength 4.47μm and full-width-at-half-maximum linewidth ≈ 40nm. This is the narrowest ever reported for an RCLED with peak wavelength beyond 3.5μm, and combined with the cw output of ≈ 0.10mW within the resonance peak from a device with diameter 140μm yields a spectral intensity more than 2× higher than any previous result beyond 3.5μm. These sources that are less expensive to manufacture than MW lasers are well suited for chemical sensing and other applications.