TERACOMB · Quantum Cascade Lasers Based TERAhertz Frequency COMB

Despite significant research efforts during the past 10 years, the terahertz (THz) spectral range remains vastly underexploited, owing essentially to the insufficient signal-to-noise ratio (SNR) achievable with present technology. The project's aim is to address this problem by building a new technological platform enabling the generation of high power, broad bandwidth, THz frequency combs (FCs) with a high frequency stability. The demonstration of FCs in the visible and near-IR spectral ranges has been among the main breakthroughs in the field of optics in the past decade. FCs are commonly generated by mode-locked lasers. In the frequency domain they consist of a broad spectrum of narrow lines, separated by a constant frequency interval, corresponding, in the time domain, to the repetition rate of the emitted pulse train. The time duration of the emitted pulses is roughly given by the inverse of the spectral bandwidth. Due to the lack of mode-locked lasers, FCs in the THz range are nowadays generated by inherently inefficient non-linear conversion techniques. This is the main cause for the low SNR of present THz systems. The THz FCs envisioned in this project will be based on THz quantum cascade lasers (QCLs), a novel, compact and powerful THz semiconductor laser source. THz FCs will be generated by mode-locked THz QCLs, and/or by using THz QCLs as semiconductor amplifiers. This will allow the production of FCs with average powers in excess of 10mW, with a spectral bandwidth > 1THz, and a corresponding pulse duration < 1ps. Such high power THz FCs will be combined with highly sensitive coherent detection techniques based on compact fs-fiber lasers that will be developed ad hoc in this project. The ultimate goal is the realization of an enabling THz technology, which may be adapted for a wide variety of applications in fields such as Physics, Chemistry, Biology and Medicine.