Mid-infrared virtually imaged phased array spectrometer with optical frequency comb: fast thermometry over large dynamic range

Abstract

We demonstrate a broadband mid-infrared frequency comb spectrometer utilizing virtually imaged phased array (VIPA) with the potential of quantitative, fast thermometry over large dynamic range. A modified Boltzmann plot method for attaining quantitative spectral interpretation in the dispersive VIPA system is proposed and realized, despite the broadband spectral overlapping and spatially variant instrumental broadening. The developed method allows accurate interpretation of the comb spectra even without reaching single-comb-tooth resolution, and can be readily extended to other measurements with overlapped spectra. The method is validated with measurements of the v 3 band of methane, and a single-shot temperature accuracy of within 10 K is experimentally demonstrated over the range of 300–600 K at a rate of 200 Hz. The present method takes full benefit of the unique advantages of the high-resolution, broadband VIPA-based frequency comb spectroscopy and has the potential to offer fast and precise thermometry. As far as we know, this is the first study to use a mid-infrared VIPA for temperature measurement with frequency comb spectroscopy.