T. Earles

86% internal differential efficiency from 8 to 9 µm-emitting, step-taper active-region quantum cascade lasers

8.4 μm-emitting quantum cascade lasers (QCLs) have been designed to have, right from threshold, both carrier-leakage suppression and miniband-like carrier extraction. The slope-efficiency characteristic temperature T1, the signature of carrier-leakage suppression, is found to be 665 K. Resonant-tunneling carrier extraction from both the lower laser level (ll) and the level below it, coupled with highly effective ll-depopulation provide a very short ll lifetime (~0.12 ps). As a result the laser-transition differential efficiency reaches 89%, and the internal differential efficiency ηid, derived from a variable mirror-loss study, is found to be 86%, in good agreement with theory. A study of 8.8 μm-emitting QCLs also provides an ηid value of 86%. A corrected equation for the external differential efficiency is derived which leads to a fundamental limit of ~90% for the ηid values of mid-infrared QCLs. In turn, the fundamental wallplug-efficiency limits become ~34% higher than previously predicted.

Resonant Leaky-Wave Coupled Phase-Locked Arrays of Mid-Infrared Quantum Cascade Lasers

This paper presents the resonant leaky-wave coupling of quantum cascade lasers, which, in turn, has provided in-phase-mode operation to 3.0 W front-facet emitted power in a near-diffraction-limited far-field beam pattern, with 2.5 W in the main lobe.

Two-dimensional conduction-band engineering for performance optimization of quantum cascade lasers

This paper presents the deep-well quantum cascade laser (DW QCL) structures of novel active-region designs for virtually suppressing carrier leakage as well as for further increasing the CW η_wp,max value. Preliminary results are T₁ values as high as 797 K over the 20-60^oC range in heatsink temperature.

Tapered active-region quantum cascade lasers for virtual suppression of carrier-leakage currents

A quantum-cascade laser design for effectively suppressing carrier leakage is demonstrated. The characteristic temperatures for threshold and slope efficiency, T 0 and T 1 , reach values of 231 K and 797 K over the 20–60°C range

High-performance, reliable, 730 nm-emitting Al-free active region diode lasers

Compressively-strained InGaAsP QW active (/spl lambda/=732 nm) diode lasers achieve 2.4 W CW front-facet power from 100 /spl mu/m-wide apertures, with reliable operation at 0.5 W CW. Record-high characteristic temperatures for the threshold current and the differential quantum efficiency, T/sub 0/=115 K and T/sub 1/=285 K are obtained by growing on misoriented substrates.

Narrow spectral width (<1 /spl Aring/ FWHM) 1.1-W cw operation from 100-/spl mu/m stripe DFB diode lasers (/spl lambda/=0.893 /spl mu/m) with Al-free optical-confinement region

We present results from 100-/spl mu/m stripe DFB lasers, which operate at 1.1 W cw with a linewidth of 0.9 W and at 1 W quasi-cw (5 /spl mu/s, 2 kHz) with a linewidth of 1.2 A. These SCH lasers use a broad-waveguide structure consisting of an InGaAs DQW active region within an InGaP optical confinement region and InGaAlP cladding layers.

0.4-W diffraction-limited beam and single-frequency operation from resonant antiguided phase-locked laser array with DFB grating

We present here the first demonstration of a phase-locked array for which a DFB grating acts as an array-mode selector. Single-frequency and single-spatial mode operation are achieved to 0.45 W peak power. Thus, resonant antiguided optical waveguide (ROW) DFB laser diode arrays have potential for stable-beam, reliable operation to watt range coherent powers.