Compact laser sources emitting in the mid- to long-wavelength infrared range (4 to12 microns) currently are of great interest for spectroscopic applications in homeland security, laser photo-acoustic spectroscopy, missile-avoidance systems, medical diagnostics and free-space communications. However, lack of sufficiently powerful, compact sources has drastically limited development in these fields.

Currently, multiple single index beams have been combined in an attempt to generate high-power laser light sources, but these techniques cannot provide the increased beam quality over large distances required by many applications. A method to create a high-power, narrow-beam laser source in the mid- to long-wavelength range is needed.

UW–Madison researchers have developed a compact laser array device capable of generating high-power, coherent laser light at mid-infrared wavelengths by scaling the power of quantum-cascade (QC) lasers whereby an active photonic crystal (APC) structure is fabricated in the QC material. The combined APC-QC structure allows the laser device to emit diffraction-limited, stable beams from large apertures.

The compact quantum-cascade laser structure consists of one or more active cores, an optical confinement structure, a cladding structure and laterally-spaced trench regions extending through the structures. The structure has index steps an order of magnitude higher than in conventional structures. Quasi-continuous wave or continuous wave laser operations are desirable in many applications, but often are vulnerable to thermally induced variations in the dielectric constant. The APC-QC structure allows a device to operate as a quasi-continuous wave or continuous wave laser without thermally induced variations. Furthermore, the heat generated in the low-index regions can be effectively laterally removed by materials in the high-index regions.

File Number: P09338US01