Dual-comb photoacoustic spectroscopy with electro-optic generation for the analysis of gaseous samples

Abstract: In this work we present the design and characterization of a dual comb photoacoustic spectroscopy (DCPAS) set-up for ammonia detection in the near infrared. The system consists of a dual electro-optic (EO) comb generator that generates a multiheterodyne beating signal in the gas sample. The input to the dual EO comb generator is a laser diode tuned to a fixed wavelength within an absorption feature of ammonia (around 1531.6 nm, 6529 cm-1) and we show how the dual comb allows to perform PAS measurements and resolve the absorption features with high spectral resolution. We present results of the ammonia absorption line profile reconstruction with a bandwidth of 1 cm-1 and a resolution of 0.08 cm-1. Moreover, we show that dual comb technique based on electro-optic generation maximally simplifies the optimization of the multiheterodyne signal according the characteristic of the photoacoustic detection module. We present results using a resonant gas cell (pipe shape) and we show how easily the dual comb optical source is adjusted to generate multiherodyne beating tones within the band of resonance of the gas cell.