Rui Q. Yang

High power mid-infrared interband cascade lasers based on type-II quantum wells

We report a high power mid-infrared interband cascade laser operating at temperatures up to 170 K. The threshold current densities of this laser are considerably lower than the previously reported values in cascade lasers. The structure was grown by molecular beam epitaxy on a GaSb substrate and comprises 23 periods of active regions separated by digitally graded multilayer injection regions. A peak optical output power of ∼0.5 W/facet and a slope of 211 mW/A per facet, corresponding to a differential external quantum efficiency of 131%, are observed at 80 K and at a wavelength of ∼3.9 μm.

Mid-infrared interband cascade lasers with quantum efficiencies >200%

An external differential quantum efficiency exceeding 200% has been observed from 4 μm InAs/InGaSb/AlSb interband cascade lasers under 1 μs pulses and 0.1% duty cycle at 80 K. By increasing the pulse lengths and the repetition rates, average powers >16 mW have been measured with 5 μs pulses at 10% duty cycle, the internal quantum efficiency and the internal loss are determined to be 220% and 14 cm−1, respectively.

Interband cascade light emitting diodes in the 5–8 μm spectrum region

Interband cascade electroluminescence in the 5–8 μm spectrum region is observed from a staircase of Sb-based type-II quantum well structures. The structure was grown by molecular beam epitaxy on a GaSb substrate and comprises 15 periods of active regions separated by digitally graded multilayer injection regions. The device has been operated at 300 and 77 K with an output optical power up to 700 nW. The strong blue shift of the electroluminescent peak with the applied bias due to the Stark effect has also been observed.

Demonstration of cascade process in InAs/GaInSb/AlSb mid-infrared light emitting devices

We demonstrate the cascade process in mid-infrared electroluminescent InAs/GaInSb/AlSb multi-quantum-well devices. We report the proportional relation between the emitted optical power and the number of periods. This observed scaling is associated with the sequential transport of electrons from one active region to the next situated downstream in potential energy through the injection region. Deviations from this exact scaling are correlated with the variation of the wafer-to-wafer structural quality.

Long-wavelength infrared (~10-15 mm) electroluminescence from Sb-based interband cascade devices.

Electroluminescence in the long-wavelength infrared (10-15 mm) spectrum region was observed from Sb-based type-II interband cascade quantum well structures. The device structure was grown by molecular beam epitaxy on a GaSb substrate and comprises 10 repeated periods of active regions separated by digitally graded multilayer injection regions. The devices have been operated at 300 K and 77 K, with an output optical power up to 50 nW. The emission wavelength, the longest observed in any compound semiconductor material at room temperature, results from tailoring the heterostructure, demonstrating a unique capability of this Sb-family type-II material system.

Mid-IR interband cascade lasers: progress toward high performance

Type-II interband cascade (IC) lasers take advantage of the broken-gap alignment in type-II quantum wells to reuse electrons for sequential photon emissions from serially connected active regions. Here, we review our recent progress in InAs/GaInSb type-II IC lasers at emission wavelengths of 3.6 - 4 micrometers . These semiconductor lasers have exhibited significantly higher differential quantum efficiencies and peak powers than previously reported. Low threshold current densities (e.g., approximately 56 A/cm2 at 80 K) and power efficiency exceeding 14% were observed from mesa-stripe lasers when operated in cw mode. Also, these lasers were able to operate at temperatures up to approximately 252 K in pulsed mode and approximately 142 K in cw mode. We observed slope efficiencies exceeding 1 W/A/facet, corresponding to a differential external quantum efficiency exceeding 600%, from devices at temperatures above 80 K. A peak output power of approximately 6 W/facet was observed from an IC laser at 80 K.

High-power and high-efficiency mid-infrared type-II quantum well and interband cascade lasers

High power and high quantum efficiency operation of both diode-pumped and interband cascade lasers based on InAs/Ga(In)Sb type-II quantum well with a broken gap band alignment have been demonstrated. The interband cascade laser yielded 0.5 W peak and 16 mW average output per facet under 1- and 5-microsecond(s) long pulses at 80K, while the optically pumped 4-micrometers devices yielded 0.9-1.6 W peak and 90-150 mW average output per facet for 0.1- to 1-ms long pulses at 71K. These output powers are among the highest long-pulse results reported from any semiconductor laser at these wavelengths.

Room-temperature low-threshold type-II quantum-well lasers at 4.5 /spl mu/m

The present data confirm theoretical predictions that semiconductor lasers based on type II InAs-InGaSb-InAs-AlSb QWs should have significant advantages over other structures in the MIR spectral region, due to both improved carrier confinement and the potential of significant Auger suppression.

Quantum cascade light emitting diodes based on type-II quantum wells

We have demonstrated room-temperature CW operation of type- II quantum cascade (QC) light emitting diodes at 4.2 micrometers using InAs/InGaSb/InAlSb type-II quantum wells. The type-II QC configuration utilizes sequential multiple photon emissions in a staircase of coupled type-II quantum wells. The device was grown by molecular beam epitaxy on a p-type GaSb substrate and was composed of 20 periods of active regions separated by digitally graded quantum well injection regions. The maximum average output power is about 250 (mu) W at 80 K, and 140 (mu) W at 300 K at a repetition rate of 1 kHz with a duty cycle of 50%.

High quantum efficiency InAs/GaInSb/AlSb interband cascade lasers

We proposed and demonstrated a new type of quantum cascade laser based on interband transitions in InAs/GaInSb/AlSb type-II quantum wells. Contrary to the conventional heterostructure or quantum well lasers, this device takes advantage of recycling carriers from valence band back to conduction band for sequential photon emissions to achieve high quantum efficiency. So far, an external differential quantum efficiency exceeding 200% has been observed from 4- micrometers lasers under 1 microsecond(s) pulses and 0.1% duty cycle at 80 K. Under 5 - 10 microsecond(s) pulse lengths and 10% duty cycle, peak powers > 160 mW have been obtained, the corresponding internal quantum efficiency was deduced to be 220%.