Toward new frontiers for terahertz quantum cascade laser frequency combs

Abstract

Broadband, quantum-engineered, quantum cascade lasers (QCLs) are the most powerful chip-scale sources of optical frequency combs (FCs) across the mid-infrared and the terahertz (THz) frequency range. The inherently short intersubband upper state lifetime spontaneously allows mode proliferation, with large quantum efficiencies, as a result of the intracavity four-wave mixing. QCLs can be easily integrated with external elements or engineered for intracavity embedding of nonlinear optical components and can inherently operate as quantum detectors, providing an intriguing technological platform for on-chip quantum investigations at the nanoscale. The research field of THz FCs is extremely vibrant and promises major impacts in several application domains crossing dual-comb spectroscopy, hyperspectral imaging, time-domain nanoimaging, quantum science and technology, metrology and nonlinear optics in a miniaturized and compact architecture. Here, we discuss the fundamental physical properties and the technological performances of THz QCL FCs, highlighting the future perspectives of this frontier research field.

Laser Frequency Combs with Fast Gain Recovery: Physics and Applications

“…Following the first works in the mid‐infrared, THz QCL frequency combs were demonstrated with homogeneous [ 37 ] and heterogeneous [ 38,39 ] designs, opening the door to precision spectroscopy, imaging, and metrology also in the terahertz range. [ 40 ] Further efforts on dispersion engineering based on waveguide and coating designs (Figure 2c,d) optimized to reduce the net group velocity dispersion (GVD) of the laser, [ 41,42 ] as well as more elaborate schemes based on intersubband cavity polaritons in the case of THz QCLs, [ 43 ] allowed broadening the spectral extent of QCL combs and their current operation range.…”

A Review of THz Technologies for Rapid Sensing and Detection of Viruses including SARS-CoV-2

“…Meta-and nanomaterials with various unit cell geometries working in the THz region are an emerging option assuring much promise for on-site, high-speed virus detection and have the potential to go beyond the detection limit. Moreover, with recent advancements in miniaturized THz technologies [86][87][88][89][90], THz-based virus sensing platforms can be widely deployed, even to remote locations. Even though terahertz based biosensing methods have been used for several sectors [91,92], there is still a need for extensive research on SARS CoV-2 and similar virus detection.…”

Physics and technology of Terahertz quantum cascade lasers

“…The research field of THz frequency combs is extremely vibrant and promises major impacts in several application domains crossing quantum metrology, dual-comb spectroscopy [134], hyper spectral imaging, timedomain nano-imaging, quantum science and technology, and non-linear optics [135].…”