InAs-based Interband Cascade Lasers Research Articles

Comparison between InAs-based and GaSb-based interband cascade lasers with hybrid superlattice plasmon-enhanced claddings

We compare InAs-based and GaSb-based interband cascade lasers (ICLs) with the same 12-stage active region designed to emit at a wavelength of 4.6 µm. They employ a hybrid cladding architecture with the same geometry and inner claddings consisting of InAs/AlSb superlattices but different outer claddings: The InAs-based ICL employs plasmon enhanced n-type doped InAs layers while the GaSb-based ICL employs plasmon-enhanced n-type doped InAs0.915Sb0.085 claddings lattice matched to GaSb. Due to the lower refractive index of n + -InAsSb (n = 2.88) compared to n+ -InAs (n = 3.10) and higher refractive index of separate confinement layers, the GaSb-based ICL shows a 3.8% higher optical mode confinement in the active region compared to the InAs-based ICL. However, the InAs-based ICL has 15.3% lower free carrier absorption losses than the GaSb-based ICL, resulting in approximately equal threshold gains. Experimentally operated in pulsed mode and at room temperature, the GaSb-based ICL shows a 15.3% lower threshold current density, but also 12.8% higher threshold voltage resulting in comparable threshold power densities. Also presented is the influence of geometry and doping variation on confinement factors and calculated free carrier absorption losses in the GaSb-based ICL.

High-temperature continuous-wave operation of InAs-based interband cascade laser

In this work, we report an InAs-based interband cascade laser that emits at λ = 4.58 μm in continuous-wave mode up to a maximum temperature of 64 °C, an increase of 29 °C beyond the previously highest reported value for InAs-based interband cascade lasers. At T = 20 °C, an output power of 20 mW was achieved for a 10-μm × 2-mm ridge waveguide device with one facet coated for high reflection and epilayer-down mounting.

Enhanced performance of InAs-based interband cascade lasers emitting between 10–13 µm

Interband cascade lasers (ICLs) based on the type-II quantum well (QW) active region have attracted much attention for a range of practical applications in the mid-infrared due, in part, to their low power consumption. However, extending the operating wavelength of these ICLs into the long-wave infrared region presents several challenges including the reduced thermal conductivity of the optical cladding layers and the diminished wavefunction overlap in the type-II QW. One solution to alleviate the former concern is to use InAs-based ICLs. To solve the latter problem, InAs0.5P0.5 barriers are introduced in the active region, which lowers the electronic energy level and allows for the InAs well width to be reduced at longer emission wavelengths. Here the advancement of long wavelength ICLs, made from four new InAs-based ICL wafers grown by molecular beam epitaxy, is reported. These ICLs lased in the wavelength range from 10 to 13 µm and showed significantly improved performance compared with previous ICLs, including the first demonstration of broad-area devices operating in continuous wave mode beyond 12 µm. These ICLs exhibited substantially increased output powers with reduced threshold voltages (V th) and current densities (J th). They operated at temperatures up to 40 K higher than previous ICLs at similar wavelengths.

Low threshold InAs-based interband cascade lasers grown by MBE

Mid-infrared interband cascade laser (ICL) structures aimed for emission at room temperature in the 4–5 μm wavelength region are grown by molecular beam epitaxy (MBE) on InAs substrates. High crystalline quality of the epitaxial structures has been confirmed by X-ray diffraction with thickness deviations less than 1% from the designs. Also, the average surface defect density is in the low ten to the fourth level. The broad-area (BA) devices made from the MBE-grown ICL wafers can lase in continuous wave (CW) mode in a wavelength range from 3.5 to 4.8 μm at temperatures up to 257 K, which is the highest reported for BA InAs-based ICLs at similar wavelengths. Their threshold current densities are low (e.g. 2.7 A/cm2 at 80 K), indicating excellent material quality with a very low Shockley-Reed-Hall recombination. In pulsed mode, the lowest threshold current density is 252 A/cm2 at 300 K, and the maximum operating temperature has reached 379 K. By comparisons in device performance among multiple MBE-grown ICL wafers, the importance of beam equivalent pressure stability and accurate control of layer thicknesses is demonstrated for the desirable performance.

Long wavelength interband cascade lasers

InAs-based interband cascade lasers (ICLs) can be more easily adapted toward long wavelength operation than their GaSb counterparts. Devices made from two recent ICL wafers with an advanced waveguide structure are reported, which demonstrate improved device performance in terms of reduced threshold current densities for ICLs near 11 μm or extended operating wavelength beyond 13 μm. The ICLs near 11 μm yielded a significantly reduced continuous wave (cw) lasing threshold of 23 A/cm2 at 80 K with substantially increased cw output power, compared with previously reported ICLs at similar wavelengths. ICLs made from the second wafer incorporated an innovative quantum well active region, comprised of InAsP layers, and lased in the pulsed-mode up to 120 K at 13.2 μm, which is the longest wavelength achieved for III–V interband lasers.

InAs-based interband cascade lasers at 4.0 μm operating at room temperature * * Project supported by the National Natural Science Foundation of China (Nos. 61790583, 61774150, 61774151) and the National Basic Research Program of China (No. 2014CB643903).

InAs-based interband cascade lasers (ICLs) with InAs plasmon waveguides or InAs/AlSb superlattice (SL) waveguides were demonstrated at emission wavelengths below 4.1 μm. The threshold current densities of the lasers with SL waveguides were 37 A/cm2 at 77 K in continuous wave mode. The operation temperature of these lasers reached room temperature in pulsed mode. Compared with the thick InAs n++ plasmon cladding layer, the InAs/AlSb superlattice cladding layers have greater advantages for ICLs with wavelengths less than 4 μm even in InAs based ICLs because in the short-wavelength region they have a higher confinement factor than InAs plasmon waveguides.

InAs-based distributed feedback interband cascade lasers

Single mode emission of InAs-based interband cascade lasers using lateral metal gratings that provide distributed feedback is presented. A double ridge configuration was developed, where the grating is placed above the active region while a second, slightly wider ridge ensures current confinement in the active region. Side mode suppression ratios above 30 dB have been obtained, and single mode emission was observed at wavelengths around 6 μm in continuous-wave operation up to a temperature of −10 °C. Current- and temperature-tuning rates of 0.011 nm/mA and 0.50 nm/ °C, respectively, have been found, and a total tuning range of 6.5 nm has been covered by one device. As a reference, ridge waveguide devices without a grating made from the same material were able to emit in pulsed mode up to 49 °C and in continuous-wave operation at temperatures up to 0 °C around 6 μm.

Low-threshold InAs-based interband cascade lasers operating at high temperatures

InAs-based interband cascade (IC) lasers with improved optical confinement have achieved high-temperature operation with a threshold current density as low as 247 A/cm2 at 300 K for emission near 4.6 μm. The threshold current density is the lowest ever reported among semiconductor mid-infrared lasers at similar wavelengths. These InAs-based IC devices lased in pulsed mode at temperatures up to 377 K near 5.1 μm. Narrow-ridge devices were able to operate in continuous-wave mode at temperatures up to 308 K near 4.8 μm. The implications and prospects of these results are discussed.

Room‐temperature operation of InAs‐based interband‐cascade‐lasers beyond 6 µm

A report is presented on long wavelength room-temperature operation of InAs-based interband cascade lasers (ICLs) at 6.06 µm. The broad area and ridge waveguide devices operate in pulsed mode up to 25 and 40 °C, respectively, and therewith extend the available room-temperature operation range of ICLs to longer wavelengths.

InAs-Based Mid-Infrared Interband Cascade Lasers Near 5.3 $\mu{\rm m}$

InAs-based interband cascade (IC) lasers with dielectric-metal hybrid top cladding layers were demonstrated at emission wavelengths near 5.3 μm for temperatures up to 248 K in continuous wave mode and 300 K in pulsed mode. Preliminary experimental results showed that these hybrid waveguide IC lasers had slightly better device performances in terms of operating temperature, compared to IC lasers with InAs plasmon cladding layers on both sides. The threshold current densities of these IC lasers were as low as 12 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> with voltage efficiency above 96% at 80 K. The output power of these IC lasers reached 120 mW/facet and a power efficiency of 21% was obtained at 80 K.

InAs-based interband cascade lasers with emission wavelength at 10.4 µm

An InAs-based plasmon waveguide interband cascade laser has been demonstrated near 10.4 µm. The device operated at temperatures up to 166 and 190K in CW and pulsed modes, respectively. This device showed a threshold current density as low as 10 A/cm2 at 80K. Also, simultaneous lasing at dual wavelengths near 9.1 and 10.2 µm was observed from this device.

InAs-based interband cascade lasers near 6 µm

Broad-area interband cascade lasers have been demonstrated on an InAs substrate and at emission wavelengths near 6 mum at temperatures up to 150 K in continuous-wave mode. The emission wavelengths are the longest achieved among III-V interband diode lasers. The threshold current density and voltage are about 50 A/cm 2 and 2.4 V, respectively, at 82 K.