S. Slivken

Room temperature quantum cascade lasers with 27% wall plug efficiency

Using the recently proposed shallow-well design, we demonstrate InP based quantum cascade lasers (QCLs) emitting around 4.9 μm with 27% and 21% wall plug efficiencies in room temperature (298 K) pulsed and continuous wave (cw) operations, respectively. The laser core consists of 40 QCL-stages. The highest cw efficiency is obtained from a buried-ridge device with a ridge width of 8 μm and a cavity length of 5 mm. The front and back facets are antireflection and high-reflection coated, respectively. The maximum single facet cw power at room temperature amounts to 5.1 W.

Room temperature continuous wave operation of quantum cascade lasers with 12.5% wall plug efficiency

An InP based quantum cascade laser heterostructure emitting at 4.6μm was grown with gas-source molecular beam epitaxy. The wafer was processed into a conventional double-channel ridge waveguide geometry with ridge widths of 19.7 and 10.6μm without semi-insulating InP regrowth. An uncoated, narrow ridge device with a 4.8mm cavity length was epilayer down bonded to a diamond submount and exhibits 2.5W maximum output power with a wall plug efficiency of 12.5% at room temperature in continuous wave operation.

Room temperature continuous wave operation of quantum cascade lasers with watt-level optical power

We demonstrate quantum cascade lasers at an emitting wavelength of 4.6μm, which are capable of room temperature, high power continuous wave (cw) operation. Buried ridge geometry with a width of 9.8μm was utilized. A device with a 3mm cavity length that was epilayer-down bonded on a diamond submount exhibited a maximum output power of 1.3W at room temperature in cw operation. The maximum output power at 80K was measured to be 4W, with a wall plug efficiency of 27%.

High-temperature, high-power, continuous-wave operation of buried heterostructure quantum-cascade lasers

We report cw operation of buried heterostructure quantum-cascade lasers (λ=6 μm) using a thick electroplated Au top contact layer and epilayer-up bonding on a copper heat sink up to a temperature of 333 K (60 °C). The high cw optical output powers of 446 mW at 293 K, 372 mW at 298 K, and 30 mW at 333 K are achieved with threshold current densities of 2.19, 2.35, and 4.29 kA/cm2 respectively, for a high-reflectivity-coated, 9-μm-wide and 3-mm-long laser.

Continuous-wave operation of λ∼4.8μm quantum-cascade lasersat room temperature

Continuous-wave (cw) operation of quantum-cascade lasers emitting at λ∼4.8μm is reported up to a temperature of 323K. Accurate control of layer thickness and strain-balanced material composition is demonstrated using x-ray diffraction. cw output power is reported to be in excess of 370mW per facet at 293K, and 38mW per facet at 323K. Room-temperature average power measurements are demonstrated with over 600mW per facet at 50% duty cycle with over 300mW still observed at 100% (cw) duty cycle.

Buried heterostructure quantum cascade lasers with high continuous-wave wall plug efficiency

The authors report on the development of λ∼4.7μm strain-balanced InP-based quantum cascade lasers with high wall plug efficiency and room temperature continuous-wave operation. The use of narrow-ridge buried heterostructure waveguides and thermally optimized packaging is presented. Over 9.3% wall plug efficiency is reported at room temperature from a single device producing over 0.675W of continuous-wave output power. Wall plug efficiencies greater than 18% are also reported for devices at a temperature of 150K, with continuous-wave output powers of more than 1W.

Temperature dependent characteristics of λ∼3.8μm room-temperature continuous-wave quantum-cascade lasers

Temperature dependent characteristics of λ∼3.8μm quantum-cascade lasers (QCLs) operating up to 318K in continuous-wave (cw) mode are reported. A high-reflectivity coated 11.5-μm-wide and 4-mm-long epilayer-down bonded QCL using a diamond submount shows a considerable improved cw operation with an output power of 143mW and a threshold current density of 1.51kA∕cm2 at 298K. The temperature dependence on optical and electrical performances of the QCLs with respect to the output power, slope efficiency, threshold current/voltage, turn-on voltage, differential series resistance, and emission wavelength are investigated systematically above liquid nitrogen temperature.

High-power, room-temperature, and continuous-wave operation of distributed-feedback quantum-cascade lasers at λ∼4.8μm

A high-power continuous-wave (CW) operation of distributed-feedback quantum-cascade lasers using a buried grating with epitaxial regrowth up to temperatures of above 60°C is demonstrated. For a high-reflectivity-coated 13μm-wide and 3mm-long cavity, CW output powers of 135mW at 25°C and still 37mW at 60°C are obtained. The device exhibits a CW threshold current density of 1.1kA∕cm2, a maximum CW wall-plug efficiency of 1.48% at 25°C, and a characteristic temperature of 177K in pulsed mode. Single-mode emission near 4.8μm with a side-mode suppression ratio of >30dB and a tuning range of ∼8.1cm−1 (i.e., tunability of 0.18cm−1∕K) in the temperature range from 15to60°C is observed.

2.4 W room temperature continuous wave operation of distributed feedback quantum cascade lasers

We demonstrate high power continuous-wave room-temperature operation surface-grating distributed feedback quantum cascade lasers at 4.8 μm. High power single mode operation benefits from a combination of high-reflection and antireflection coatings. Maximum single-facet continuous-wave output power of 2.4 W and peak wall plug efficiency of 10% from one facet is obtained at 298 K. Single mode operation with a side mode suppression ratio of 30 dB and single-lobed far field without beam steering is observed.

High-power continuous-wave operation of a 6 μm quantum-cascade laser at room temperature

We report continuous-wave (cw) operation of quantum-cascade lasers (λ=6 μm) using a thick electroplated Au top contact layer and epilayer-up bonding on a copper heat sink up to a temperature of 308 K (35 °C). The high cw optical output powers of 132 mW at 293 K and 21 mW at 308 K are achieved with threshold current densities of 2.29 and 2.91 kA/cm2, respectively, for a high-reflectivity-coated 15 μm wide and 2 mm long laser.