VECSEL-based virtually imaged phased array spectrometer for rapid gas phase detection in the mid-infrared

Abstract

We present a novel, to the best of our knowledge, system for high-resolution, time-resolved spectroscopy in the mid-wave infrared based on a modelocked vertical external cavity surface emitting laser (VECSEL) frequency comb coupled to a virtually imaged phased array (VIPA) spectrometer. The GHz level repetition rate of VECSEL-based systems coupled to VIPA spectrometers enables comb tooth resolved spectra without the use of additional filter cavities often required to increase comb tooth spacing. We demonstrate absorption spectroscopy on a methane ( C H 4 ) gas mixture at 2900 c m − 1 (3.4 µm) with over 35 c m − 1 spectral bandwidth in a single image. Rapid time-resolved measurements were made using a 300 µs exposure time with an acquisition rate limited to 125 Hz by the available camera. High-resolution absolute frequency measurements were performed by scanning the repetition rate of the VECSEL frequency comb.

Broadband 1-GHz mid-infrared frequency comb

“…For example, they enable DCS measurements over ~5 THz of spectral bandwidth with 10 µs time resolution, while still providing the necessary spectral resolution for gas phase measurements from atmospheric to combustion and exoplanet relevant temperatures and pressures. These benefits were highlighted previously in the near infrared 18 , but have not been fully extended to the MIR, where only a handful of 1 GHz MIR frequency combs exist [19][20][21][22][23][24][25] . It should be noted that the multi-GHz chip-based MIR frequency combs generated from electrooptic combs 26 quantum cascaded lasers 27 or microcombs 28 enable sub-microsecond spectral acquisition.…”

Optical Frequency Combs for Molecular Spectroscopy, Kinetics, and Sensing

“…Several research groups are actively applying FCS to gas-phase chemical reaction kinetics, harnessing both dual-comb and spatially dispersive methods to study reacting systems in room temperature flow cells, 56,58,[108][109][110][111][112][113] and high temperature flames, discharges, and shock tubes. [114][115][116][117][118][119][120][121][122] The application of these methods to problems in atmospheric chemistry is particularly compelling.…”

Microscopic nonequilibrium dynamics of gain coupled mode-locked dual cavity VECSELs

“…Although the two pulse trains generated in this work operate at slightly different center wavelengths, spectral broadening after amplification in Yb-fiber amplifiers will enable spectral broadening and overlap needed for generation of interferograms between the two systems, as we have demonstrated in previous work when amplifying the output of frequency combs based on vertical external cavity semiconductor lasers (VECSELs) 1 . 2 The easily adjustable and high-repetition rates of the shared-cavity VECSEL based DCS system can enable precision spectroscopic absorption-based measurements at high acquisitions rates useful in applications ranging from atmospheric monitoring to time-resolved studies of chemical dynamics (e.g. combustion, explosives, photo initiated reactions, laser-produced plasmas, etc.…”