UCLA researchers in the Department of Electrical Engineering have developed grating-based quantum-cascade vertical external lasers that operate in the terahertz and mid-infrared range.
Mid-infrared (IR) quantum-cascade (QC) lasers with high output power and excellent near-diffraction beam patterns are of strong interest for remote sensing and infrared countermeasure applications. Mid-IR QC lasers, which combine wavelengths through a diffraction grating, are the dominant semiconductor laser source in infrared countermeasure devices. However, the broad-area edge emitting waveguides result in reduced beam quality. Vertical-external-cavity surface-emitting lasers (VECSEL) have a promising architecture for increasing the output power of mid-IR QC lasers. QC-VECSELs have been previously demonstrated in the Terahertz range. However, the metallic microcavity resonators prevent this approach from being scaled to shorter wavelengths in the mid-IR (below λ~15μm) range. Mid-IR QC-lasers are of strong interest for gas sensing, since many molecules have vibrational spectral signatures (i.e. “fingerprints) between 2-30μm.
UCLA researchers have developed a method for fabricating a QC VECSEL in either the terahertz (30-300μm) or mid-infrared spectral (3-30μm) range. This approach uses dielectric-metal gratings rather than metallic microcavity resonators to allow for increased output power while maintaining a high-quality beam pattern. The surface emission may allow for the combination of many laser beams to further boost the output power. Moreover, other undesired modes which do not radiate are naturally prevented from lasing since they are strongly coupled to the metal grating and experience high loss.
Quantum-cascade vertical-external-cavity surface-emitting laser (QC-VECSEL), mid-infrared (IR) quantum-cascade (QC) lasers, dielectric-metal gratings, metallic microcavity resonators, terahertz range, waveguides