J. P. Commin

High peak power λ∼3.3 and 3.5 μm InGaAs/AlAs(Sb) quantum cascade lasers operating up to 400 K

We demonstrate λ∼3.5 μm and λ∼3.3 μm strain compensated In0.7Ga0.3As/AlAs(Sb)/InP quantum cascade lasers operating in pulse regime at temperatures up to at least 400 K. Peak optical power exceeding 3.5 W at 300 K has been achieved at both wavelengths for 10 μm wide 4 mm long lasers with high reflectivity coated back facets. Threshold current densities of 2.5 kA/cm2 and 3.5 kA/cm2 have been observed at 300 K for the devices emitting at λ∼3.5 μm and λ∼3.3 μm, respectively.

InP-Based Midinfrared Quantum Cascade Lasers for Wavelengths Below 4 μm

We review the recent development of high-performance short-wavelength (λ ~ 3.05-3.8 μm) strain-compensated InGaAs/AlAs(Sb)/InP quantum cascade lasers (QCLs). The lasers are demonstrated in which wavelengths as low as 3.05 μm are obtained at temperatures up to 295 K. We also verify that strain-compensated In0.7Ga0.3As/AlAs(Sb) QCLs with AlAs barriers in the active region operate with much better performance compared with the lasers having identical design but with AlAsSb barriers throughout the whole core region. λ ~ 3.3-3.7 μm laser emission is observed at temperatures up to at least 400 K and up to 20 W of output optical power at 285 K for the QCLs with various core region designs. Room temperature distributed feedback InGaAs/AlAs(Sb) QCLs with buried third-order gratings have been also developed, displaying single-mode operation in the wavelength range of 3.358-3.380 μm for temperatures between 270 and 360 K.

High performance, high temperature λ≈3.7 μm InGaAs/AlAs(Sb) quantum cascade lasers

We report the development of λ≈3.7 μm strain-compensated InGaAs/AlAs(Sb) quantum cascade lasers operating up to at least 400 K with high peak power and high wall plug efficiency in pulsed regime. We present a detailed comparison of the laser characteristics for devices containing AlAs barriers in the active region with those for devices of identical design but with AlAsSb barriers throughout. The devices with AlAs barriers show significantly superior performance with peak optical power of 2.6 W at 300 K decreasing to 1 W at 400 K, and threshold current densities of 3.3 and 8.2 kA/cm2 at 300 and 400 K, respectively.

Room-Temperature GaAs/AlGaAs Quantum Cascade Lasers Grown by Metal–Organic Vapor Phase Epitaxy

We demonstrate λ ~ 9 μm GaAs/Al0.45Ga0.55As quantum cascade lasers (QCLs) operating up to 320 K. Metal- organic vapor phase epitaxy has been used throughout for the growth of the devices. Detailed comparison has been carried out for the QCLs with various waveguides and grown on (100) GaAs substrates with different miscut angles towards (111)A. Introduction of InGaP cladding layers into the optical waveguide significantly improves the QCL performance due to a better optical confinement and lower waveguide losses compared with the GaAs-based waveguide. A 20- μm-wide 4-mm-long device with high reflectivity coating on the laser back facet demonstrates room-temperature pulsed output power of 220 mW and a lowered threshold current density of 6.5 kA/cm2.

λ∼3.36 μm room temperature InGaAs/AlAs(Sb) quantum cascade lasers with third order distributed feedback grating

We report on the development of strain compensated InGaAs/AlAs(Sb) quantum cascade lasers, incorporating a buried third order distributed feedback grating. Single mode operation with a side mode suppression ratio of ∼30 dB has been achieved in the wavelength range of 3.358–3.380 μm for temperatures between 270 and 360 K. The threefold increase in grating pitch size, compared with a first order grating, allows conventional photolithographic techniques to be used for single mode laser fabrication.

High-Peak-Power Room-Temperature

We report the development of high-peak-power λ ~ 3.6 μm strain-compensated In0.7Ga0.3As-AlAs(Sb) quantum cascade lasers (QCLs). The QCLs operate up to at least 400 K with high wall-plug efficiency (~9% at 300 K) in the pulsed regime. The lasers are based on a vertical transition bound-to-continuum design. Devices of 30-μm width and 4-mm length, with high reflectivity coating on the rear facet, deliver more than 20-W peak optical power at 285 K with a threshold current density of 3.1 kA/cm2. Over 2 W of peak power is obtained at 400 K.

\lambda\sim 3.6\ \mu

We report on the midinfrared broadband transmission spectroscopy measurements of a λ∼4.3 μm strain compensated In0.64Ga0.36As/Al0.58In0.42As/InP quantum cascade laser. A detailed experimental analysis of the electronic distribution for bias values below the laser threshold is presented, highlighting the effects of the design with strongly diagonal laser transition. A marked voltage induced Stark shift is observed for the diagonal laser transition while the vertical intersubband transitions involved higher energy levels remained nearly bias independent. We also demonstrate the direct observation of intersubband transitions originating from the ground level of the injector miniband to the level confined above the AlInAs barriers.