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On CHip terahertz frequency Combs

Periodic Reporting for period 3 - CHIC (On CHip terahertz frequency Combs)

Reporting period: 2020-03-01 to 2021-08-31

The terahertz (THz) portion of the electromagnetic spectrum is at the junction between optics and electronics. As the fundamental vibration modes of many molecules lie in this spectral range, THz is a gate to sensing applications in fields as varied as medical, environmental and process control. Material inspection and non-invasive imaging for safety and medical applications greatly benefit from the non-ionizing, high resolution features of T-rays. The next major step for short-range high data rate wireless communication is the extension to higher frequencies entering the THz range.
Optical frequency combs have dominated the scene of laser physics in the last 10 years revolutionizing many fields of optics from metrology to high precision spectroscopy. Optical frequency combs act as rulers in the frequency domain and are characterized by their perfectly equally spaced and coherent modes. An extremely appealing application of optical frequency combs is the so-called dual-comb spectroscopy where multi-heterodyne detection is performed allowing broadband Fourier transform spectroscopy with high resolution, high sensitivity and no moving parts. Nowadays the THz range is still lacking bandwidth coverage and high power from frequency comb sources.
The objective of this proposal is to create on-chip, self-referenced frequency combs operating in the spectral region from 1.5-5-5 THz and room temperature on-chip dual band Mid-IR and THz combs.
Here below there is a selection of the three most significative papers published since the beginning of the project.

We demonstrated a dual comb device from a monolithic source with a distance of one octave (2.3-4.6 THz). “Coexisting frequency combs spaced by an octave in a monolithic quantum cascade laser” A Forrer, M Rösch, M Singleton, M Beck, J Faist, G Scalari, Optics express 26 (18), 23167-23177 2018

We demonstrated the first Peltier-cooled THZ quantum cascade laser and the new high temperature operation for a THz QCL , 210 K. “Thermoelectrically cooled THz quantum cascade laser operating up to 210 K” L Bosco, M Franckié, G Scalari, M Beck, A Wacker, J Faist, Applied Physics Letters 115 (1), 01060 2019

Within a collaboration with INO-LENS in Florence we demonstrated the coherence properties of a THz QCL measuring it against a metrological comb source, Francesco Cappelli, Luigi Consolino, Giulio Campo, Iacopo Galli, Davide Mazzotti, Annamaria Campa, Mario Siciliani de Cumis, Pablo Cancio Pastor, Roberto Eramo, Markus Rösch, Mattias Beck, Giacomo Scalari, Jérôme Faist, Paolo De Natale, Saverio Bartalini, Nature Photonics 13,562 (2019) 
The final goal is to create on-chip, self-referenced frequency combs operating in the spectral region from 1.5-5-5 THz, with high emitted power and a well defined far-field profile.
Another important goal is constituted by the demonstration of room temperature operation of THz QCLs.
THZ QCL operating up to 210 on a Peltier cooler
Dual comb spaced by one octave from a monolithic laser ridge