Category Archives: Research

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 […]