This paper demonstrates detection of methane using tunable diode laser spectroscopy (TDLS) through difference frequency generation (DFG) in order to address fundamental rotational-vibrational absorption lines, located around 3404 nm. Direct detection confirms that wavelength referencing of recovered lineshapes, developed for Near infra-red (Near-IR) systems, has been successfully transferred to the presented Middle infra-red (Mid-IR) system. Traditional 1f and 2f TDLS with WMS detection regimes are also functionally confirmed analogous to their Near-IR equivalents.
- carbon compounds
- chemical variables measurement
- measurement by laser beam
- optical harmonic generation