Abstract: An apparatus for quantitatively detecting isotopologue of carbon dioxide using dual-photon absorption, comprising a laser source, a laser frequency stabilizer, a sample chamber, a signal detector, and a signal analyzer. The sample chamber comprises an optical resonator and a piezoelectric ceramic. The laser source is configured to output a laser beam. The laser frequency stabilizer is configured to lock the laser beam to a mode frequency of the optical resonator. The piezoelectric ceramic is configured to adjust a length of the optical resonator to alter the mode frequency of the optical resonator to match energy levels of a target molecular isotopologue. The signal detector is configured to detect a transmission intensity of the light beam passing the optical resonator to obtain a dual-photon absorption signal. The signal analyzer is configured to analyze and process the dual-photon absorption signal to obtain a concentration of the target molecular isotopologue.

Abstract: A device and a spectrometer for quantitatively detecting carbon 14 isotope by a dual-wavelength method. Two mid-infrared lasers with different wavelengths are locked in an optical cavity of a sample chamber, to ensure the two lasers are collinear. The cavity length of the optical cavity is adjusted by a cavity length adjusting unit, to tune the mode frequency of the optical cavity, and then tune the frequencies of the two mid-infrared lasers, so that the frequencies of the two mid-infrared lasers match with different energy levels of the target isotope molecule simultaneously. After the frequencies of the mid-infrared lasers match with the energy levels of the target isotope molecule simultaneously, the target isotope molecule is excited by two mid-infrared lasers simultaneously, and the optical cavity output signal of the second mid-infrared laser passing through the optical cavity is detected.

Abstract: A detection method and detection system for a trace gas, the detection method comprising: providing a resonant cavity, a gas to be measured being filled inside of a cavity body of the resonant cavity; providing detection light rays having different frequencies, the detection light rays being incident to the inside of the resonant cavity from one end of the resonant cavity in the extending direction and exiting from the other end of the resonant cavity in the extending direction so as to obtain detection light rays carrying information of a trace gas to be measured, and the cavity body of the resonant cavity having a degree of freedom of expansion and retraction in the extending direction so that the longitudinal mode frequency of the resonant cavity matches the frequencies of the incident detection light rays; and according to the detection light rays that have different frequencies and that carry information of said trace gas, acquiring the molecular saturation absorption spectrum of said trace gas, and calc