Quantum Cascade Lasers (QCLs) are semiconductor lasers that, in contrast to common diode lasers, operate on intersubband transitions in the conduction band of the materials in the heterostructure. This means that device characteristics are defined by quantum well structure rather than material bandgaps. A superlattice of quantum wells is engineered to give off a photon […]

Many QCL devices tend toward a laser core design consisting of 30-40 stages (about 1-2 μm thick,) with a device length of 2-5 mm and a laser core width of ~10 μm. The device length is largely constricted by the effects of strain causing bending for particularly long devices. Number of stages and laser core […]

Quantum mechanical selection rules dictate that laser light generated by a QCL must be polarized along the growth direction of the superlattice in the laser core. This arrangement makes a vertical emitting device, like a VCSEL, impossible. Laser light in a QCL can be coaxed into vertical emission with diffraction gratings. The periodic gratings cause […]

The Lattice Constant of a semiconductor describes the spacing (in angstroms) of the atoms in the semiconductor crystal of that material. Growing different semiconductor material on top of each other creates a boundary region where the two crystal structures meet. If the lattice constants are different enough, the mismatching positions of the atoms in the […]

Operation of continuous wave quantum cascade lasers with a frequency-shifted feedback provided by an acousto-optic modulator is reported. Measured linewidth of 1.7 cm−1 for these devices, under CW operating conditions, was in a good agreement with predictions of a model based on frequency-shifted feedback seeded by spontaneous emission. Linewidth broadening was observed for short sweep […]

The recent demonstration of external cavity quantum cascade lasers with optical feedback, controlled by an acousto-optic modulator, paves the way to ruggedized infrared laser systems with the capability of tuning the emission wavelength on a microsecond scale. Such systems are of great importance for various critical applications requiring ultra-rapid wavelength tuning, including combustion and explosion […]

5.6 μm quantum cascade lasers based on the Al0.78In0.22As/In0.69Ga0.31As active region composition with the measured pulsed room temperature wall plug efficiency of 28.3% are reported. Injection efficiency for the upper laser level of 75% was measured for the design by testing devices with variable cavity lengths. A threshold current density of 1.7 kA/cm2 and a […]

We report simultaneous two wavelength operation of an acousto-optically tuned quantum cascade laser (QCL). The two wavelengths can be independently tuned as well as independently switched, retaining the submicrosecond switching capability. In addition, we have used the two wavelength operation as a tool for the direct measure of the lifetimes of the lasing states in […]

5.6 μm quantum cascade lasers based on Al 0.78 In 0.22 As/In 0.69 Ga 0.31 As active region composition with measured pulsed room temperature wall plug efficiency of 28.3% are reported. Injection efficiency for the upper laser level of 75% was measured for the new design by testing devices with variable cavity length. Threshold current […]

5.6μm quantum cascade lasers based on Al0.78In0.22As/In0.69Ga0.31As active region composition with measured pulsed room temperature wall plug efficiency of 28.3% are reported. Injection efficiency for the upper laser level of 75% was measured by testing devices with variable cavity length. Threshold current density of 1.7kA/cm2 and slope efficiency of 4.9W/A were measured for uncoated 3.15mm […]