High Power Thermoelectrically Cooled and Uncooled Quantum Cascade Lasers With Optimized Reflectivity Facet Coatings

We present a method of preserving the device wall-plug efficiency by adjusting mirror losses with facet coatings for longer cavity quantum cascade lasers. An experimental study of output power and wall-plug efficiency as functions of mirror losses was performed by varying the front facet coating reflectivity with a high-reflectivity-coated rear facet. The use of optimized reflectivity coatings on 7-mm-long chips resulted in continuous-wave output power of 2.9 W at 293 K for thermoelectrically cooled devices mounted on AlN submounts and average and continuous-wave output power in excess of 1 W for uncooled devices emitting at 4.6 µm.Engineering and Applied Science

3 W Continuous-Wave Room Temperature Single-Facet Emission From Quantum Cascade Lasers Based On Nonresonant Extraction Design Approach

A strain-balanced, InP-based quantum cascade laser structure, designed for light emission at 4.6 $\mu$m using a new nonresonant extraction design approach, was grown by molecular beam epitaxy. Removal of the restrictive two-phonon resonant condition, currently used in most structure designs, allows simultaneous optimization of several design parameters influencing laser performance. Following the growth, the structure was processed in buried heterostructure. Maximum single-ended continuous-wave optical power of 3 W was obtained at 293 K for devices with stripe dimensions of 5 mm 11.6 $\mu$m. Corresponding maximum wallplug efficiency and threshold current density were measured to be 12.7% and 0.86 kA/cm$^{2}$.Physic

Continuous wave operation of buried heterostructure 4.6 µm quantum cascade laser Y-junctions and tree arrays.

Room-temperature continuous-wave operation for buried heterostructure 4.6 µm quantum cascade laser Y-junctions and tree arrays, overgrown using hydride vapor phase epitaxy, has been demonstrated. Pulsed wall plug efficiency for the Y-junctions with bending radius of 5mm was measured to be very similar to that of single-emitter lasers from the same material, indicating low coupling losses. Comparison between model and experimental data showed that the in-phase mode was dominating for 10mm-long Y-junctions with 5 µm-wide 1mm-long stem and 5 µm-wide branches. Total optical power over 1.5 W was demonstrated for four-branch QCL tree array

Continuous wave operation of buried heterostructure 4.6 µm quantum cascade laser Y-junctions and tree arrays.

Room-temperature continuous-wave operation for buried heterostructure 4.6 µm quantum cascade laser Y-junctions and tree arrays, overgrown using hydride vapor phase epitaxy, has been demonstrated. Pulsed wall plug efficiency for the Y-junctions with bending radius of 5mm was measured to be very similar to that of single-emitter lasers from the same material, indicating low coupling losses. Comparison between model and experimental data showed that the in-phase mode was dominating for 10mm-long Y-junctions with 5 µm-wide 1mm-long stem and 5 µm-wide branches. Total optical power over 1.5 W was demonstrated for four-branch QCL tree array

Activation energy study of electron transport in high performance short wavelengths quantum cascade lasers

We present a method to study current paths through quantum cascade lasers (QCLs). The temperature dependence of the current is measured at a fixed voltage. At low temperatures we find activation energies that correspond to the energy difference between the injector ground state and the upper laser level. At higher temperatures additional paths with larger activation energies are found. Application of this method to high performance QCLs based on strained InGaAs/InAlAs quantum wells and barriers with different band-offsets allows us to identify individual parasitic current paths through the devices. The results give insight into the transport properties of quantum cascade lasers thus providing a useful tool for device optimization.Physic