Scientific Results

All solid state mid-infrared dual-comb spectroscopy platform based on QCL technology

Year: 2015

Authors: Hugi A., Geiser M., Villares G., Cappelli F., Blaser S., Faist J.

Autors Affiliation: IRsweep GmbH, Burgstrasse 20, Zurich, CH-8037, Switzerland; Institute for Quantum Electronics, ETH Zurich, Zurich, CH-8093, Switzerland; CNR-INO – Istituto Nazionale di Ottica, LENS – European Laboratory for Non-Linear Spectroscopy, Via Nello Carrara 1, Sesto Fiorentino FI, 50019, Italy; Alpes Lasers SA, 1-3 Max.-de-Meuron, C.P. 1766, Neuchtel, CH-2000, Switzerland

Abstract: We develop a spectroscopy platform for industrial applications based on semiconductor quantum cascade laser (QCL) frequency combs. The platform\’s key features will be an unmatched combination of bandwidth of 100 cm-1, resolution of 100 kHz, speed of ten to hundreds of ┬Ás as well as size and robustness, opening doors to beforehand unreachable markets. The sensor can be built extremely compact and robust since the laser source is an all-electrically pumped semiconductor optical frequency comb and no mechanical elements are required. However, the parallel acquisition of dual-comb spectrometers comes at the price of enormous data-rates. For system scalability, robustness and optical simplicity we use free-running QCL combs. Therefore no complicated optical locking mechanisms are required. To reach high signal-to-noise ratios, we develop an algorithm, which is based on combination of coherent and non-coherent averaging. This algorithm is specifically optimized for free-running and small footprint, therefore high-repetition rate, comb sources. As a consequence, our system generates data-rates of up to 3.2 GB/sec. These data-rates need to be reduced by several orders of magnitude in real-time in order to be useful for spectral fitting algorithms. We present the development of a data-treatment solution, which reaches a single-channel throughput of 22% using a standard laptop-computer. Using a state-of-the art desktop computer, the throughput is increased to 43%. This is combined with a data-acquisition board to a stand-alone data processing unit, allowing real-time industrial process observation and continuous averaging to achieve highest signal fidelity.

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KeyWords: dual-comb spectroscopy; frequency comb; QCL; Quantum cascade laser; semiconductor; sensing