QCL-based frequency metrology from the mid-infrared to the THz range: a review

Abstract

Quantum cascade lasers (QCLs) are becoming a key tool for plenty of applications, from the mid-infrared (mid-IR) to the THz range. Progress in related areas, such as the development of ultra-low-loss crystalline microresonators, optical frequency standards, and optical fiber networks for time and frequency dissemination, is paving the way for unprecedented applications in many fields. For most demanding applications, a thorough control of QCLs emission must be achieved. In the last few years, QCLs' unique spectral features have been unveiled, while multifrequency QCLs have been demonstrated. Ultra-narrow frequency linewidths are necessary for metrological applications, ranging from cold molecules interaction and ultra-high sensitivity spectroscopy to infrared/THz metrology. A review of the present status of research in this field is presented, with a view of perspectives and future applications.

Retrieval of phase relation and emission profile of quantum cascade laser frequency combs

“…The miniaturization of these sources, together with the expansion of their operation range towards other spectral regions (e.g. mid and far IR), is crucial for broadening their application range.In this direction, the most interesting results have recently been achieved with quantum cascade lasers (QCLs), current-driven semiconductor lasers based on intersubband transitions in quantum wells, emitting high-power coherent radiation in the mid IR and terahertz (THz) [6][7][8][9][10][11]. In…”

Mixing Properties of Room Temperature Patch‐Antenna Receivers in a Mid‐Infrared (λ ≈ 9 µm) Heterodyne System

“…Mid‐infrared (MIR) quantum cascade lasers (QCLs) are today mature, powerful, and stable radiation sources that can be used as local oscillators (LO) in heterodyne systems for coherent low‐noise detection . QCL‐based heterodyne systems have been pioneered in the last decade and were mainly intended for environmental and astrophysics applications .…”

A Mid-Infrared Narrowband Absorber Based on a Subwavelength Fine-Structured Silicon–Gold Metagrating

“…However, such narrowband PAs operating in the mid-infrared (mid-IR) spectral region are particularly useful, as in the mid-IR spectral region there are various molecular fingerprint spectra [28]. When used with diode lasers and quantum cascade lasers, these narrowband PAs can be very promising in a number of applications, including spectroscopic sensing and gas detection [29,30].…”