Takashi Hosoda

Continuous wave operation of diode lasers at 3.36μm at 12°C

GaSb-based type-I quantum-well diode lasers emitting at 3.36μm at 12°C with 15mW of continuous wave output power are reported. Devices with two or four InGaAsSb compressively strained quantum wells and AlInGaAsSb quinternary barriers were fabricated and characterized. It was shown that increase in the quantum-well number led to improved laser differential gain and reduced threshold current.

Type-I Diode Lasers for Spectral Region Above 3 μm

In this paper, we consider the role of carrier confinement in achieving high-power continuous wave (CW) room temperature operation of GaSb-based type-I quantum-well (QW) diode lasers at wavelengths above 3 μm. The use of compressive strain and quinternary barrier materials to confine holes in the active QWs allows the fabrication of 3-μm GaSb-based type-I QW diode lasers operating at 17 °C in the CW mode with output power of 360 mW. We will present the results of characterization of 2.2-μm diode lasers grown on metamorphic virtual substrates. The use of InGaSb virtual substrate makes it possible to fabricate devices with As free QWs. The prospects of using virtual substrates for development of GaSb-based type-I lasers will be discussed.

Continuous-wave room temperature operated 3.0μm type I GaSb-based lasers with quinternary AlInGaAsSb barriers

Diode lasers emitting at 3.0μm were designed and fabricated. Device active region contained two compressively strained InGaAsSb quantum wells incorporated in quinternary AlInGaAsSb barriers. Laser output power at room temperature was 130mW in continuous wave regime and more than 1W in pulse.

Room temperature operated 3.1μm type-I GaSb-based diode lasers with 80mW continuous-wave output power

High-power diode lasers with heavily-strained In(Al)GaAsSb type-I quantum-well active region emitting at 3.1 mum at room temperature are reported. Devices operate in continuous-wave regime with output power above 200 mW and 80 mW at 250 K and 285 K, correspondingly.

Type-I GaSb-Based Laser Diodes Operating in 3.1- to 3.3-

Type-I quantum-well (QW) diode lasers based on AlInGaAsSb-InGaAsSb-AlInGaAsSb heterostructure active region with narrow waveguide and high indium content in the barrier were fabricated. Room-temperature continuous-wave output power of 190, 165, and 50 mW for devices emitting 3.1, 3.2, and 3.3 μm correspondingly were demonstrated. Experiment shows that improvement of the hole confinement in QWs by use of 32% indium in AlGaInAsSb barrier is a promising way of further enhancement of the device performance.

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The cascade pumping scheme reduced the threshold current density of high power type-I quantum well GaSb-based λ ∼ 3 μm diode lasers down to ∼100 A/cm2 at room temperature. Laser heterostructures had single GaInAsSb quantum well gain stages connected in series by means of GaSb/AlSb/InAs tunnel junctions followed by InAs/AlSb electron injectors. Devices with densely stacked two and three gain stages and 100-μm-wide aperture demonstrated peak power conversion efficiency of 16% and continuous wave output power of 960 mW. Corresponding narrow ridge lasers demonstrated above 100 mW of output power. The experiment showed that the bandwidth of the gain and its rate of increase with current depended strongly on the thickness of AlSb layer separating electron injectors from quantum wells. The possible impact of electron injector interfaces and ionized impurities on the carrier scattering and recombination in the active quantum well is discussed.

m Wavelength Range

Metamorphic virtual substrates with lattice constants 0.9% larger than those of GaSb were developed by solid-source molecular beam epitaxy. The mismatch between the parent GaSb and the virtual substrate was accommodated by a network of misfit dislocations formed in GaInSb buffer layers with linearly graded indium and gallium compositions. Arsenic-free laser heterostructures emitting at 2.2 μm at room temperature were grown on virtual substrates. The antimony was the only group V element used in growth. These novel diode lasers operate at room temperature and generate above 1.4 W of continuous-wave (CW) power.

Cascade type-I quantum well diode lasers emitting 960 mW near 3 μm

Mid-IR (λ≈3–3.5 μm) light emitting diodes with quinternary AlInGaAsSb barriers and InGaAsSb strained quantum wells grown on GaSb substrates have been demonstrated. The devices produced a quasi-cw emission power of 0.7 mW at room temperature and 2.5 mW at T=80 K.

High-Power 2.2-

Diode lasers operating at 3 µm in continuous wave mode at room temperature were fabricated using metamorphic molecular beam epitaxy. The laser heterostructures have a lattice constant 1.3–1.6% bigger than that of the GaSb substrates. The mismatch between the epi-structure and the substrate lattice constants was accommodated by a network of misfit dislocations confined within linearly compositionally graded buffer layers. Two types of the buffers were tested—GaInSb and AlGaInSb. The laser heterostructures with Al-containing buffer layers demonstrated better surface morphology and produced devices with lower threshold and higher efficiency. At the same time the use of Al-containing buffers caused an excessive voltage drop across the laser heterostructure. Thus, a maximum continuous wave output power of 200 mW was obtained from lasers grown on GaInSb buffers, while only 170 mW was obtained from those grown on AlGaInSb buffers.

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Laser diodes based on AlInGaAsSb/InGaAsSb heterostructures with different waveguide widths were designed and fabricated. The decrease in the waveguide width from 1470 to 470 nm led to the improvement of the device performance. Lasers with 470 nm quinternary waveguides demonstrated 200 mW continuous wave output power at room temperature.