The mid-IR and THz optics group deals with photonics research in these unconventional spectral regions.
A part of the research group performs ultra-high-sensitivity molecular spectroscopy in the mid IR. The saturated-absorption cavity ring-down (SCAR) technique, conceived by the group, allows to detect extremely rare molecules, such as 14CO2 well below the natural abundance of ~1 ppt. The SCAR technology is protected by 3 patents and has been transferred from CNR to the spin-off company ppqSense S.r.l., which is further developing the laboratory prototype to make it a commercial instrument.
The group also develops alternative techniques for trace-gas detection, such as photoacoustic CEPAS, more suited for the development of compact, low-cost and portable gas absorption sensors. Molecular spectroscopy in the THz spectral region is also investigated through the development of a difference frequency generation spectrometer that grants ultra-broadband spectral coverage and accurate determination of molecular transitions.
In parallel, the group deals with the characterization of the emission of quantum cascade laser frequency combs (QCL-combs) in the mid-IR and terahertz (THz) spectral ranges. The applicability of QCL-combs for spectroscopy as well as metrological sources for classical and quantum communications is under investigation.
Linewidth and frequency stability of laser sources play a key role in all the high-sensitivity and high-precision spectroscopic techniques. Our research group has gained a large expertise in the analysis of phase and frequency noise of coherent sources, including up- and down-conversion sources, quantum and interband cascade lasers (QCLs and ICLs). During the last decade, a number of techniques for laser noise reduction and frequency stabilization have been developed, including optical and electronic locking to stable references (optical references, frequency combs, molecular transitions) or to high-finesse optical resonators (Fabry-Perot resonators, whispering gallery mode resonators). The group has also expertise in the realization of mid- and far-infrared coherent sources by means of nonlinear processes in crystals or diodes.
