The new material orientation patterned gallium phosphide (OPGaP) enables coherent and broadband infrared spectroscopy in the spectral fingerprint region from 6 to 12um, accessing the largest molecular absorption cross-sections and permitting sensitive, quantitative and species-specific measurements. Here, we show how dual-comb spectroscopy-a form of high-speed Fourier-transform spectroscopy involving no moving parts and capable of very high resolutions-can be extended to the 6-8um wavelength band using femtosecond optical parametric oscillators (OPOs). By acquiring dual-comb interferograms in a time comparable with the mutual decoherence time of the OPO combs we implement cross-correlation-based spectral averaging to obtain high-fidelity spectra of H2O and CH4 at approximately 0.3 cm-1 resolutions from 1285 to 1370 cm-01 and 1500-1585 cm-1.
- Spectrometers and spectroscopic instrumentation
- Parametric oscillators and amplifiers
- Spectroscopy, Fourier transforms
- Spectroscopy, molecular