Mid-infrared interband cascade superluminescent diode with tunable spectral-width and monolithically integrated detector

This study reports a mid-infrared interband cascade superluminescent diode (ICSLD). By controlling the proportion of amplified spontaneous emission in the spectrum, we have achieved spectral width tuning from 1358 to 44 nm. Benefiting from the optical field confinement effect of the waveguide structure, the radiant exitance of the device reaches 77 W/cm2 at 78 K and 5.04 W/cm2 at 300 K, which is an order of magnitude higher than that of the surface-emitting LEDs based on the same material. A five-stage cascaded InAs/GaAsSb interband cascade structure is employed as the active region. The maximum output power-to-length ratio of the ICSLDs at 78 K is close to the state-of-the-art, while the injection current and device length are only 20% of those of quantum cascade superluminescent diodes. The interband cascade structure exhibits a longer nonradiative lifetime than the quantum cascade structure, which is the key to realizing low power consumption. A theoretical model for superluminescent diodes is developed, which reveals that variations in device size and operating conditions typically cause the output power and spectral width to vary inversely. Furthermore, the device functions as an edge-illuminated mesa photodiode at zero bias. It shows a responsivity of 2.6 A/W at 78 K, which is an order of magnitude higher than that of the top-illuminated mesa photodiode fabricated from the same epitaxial wafer. We demonstrate the generation and detection of optical signals on the same epitaxial wafer using ICSLDs.