HIGH-SENSITIVE DETECTION OF TRACE GASES USING OPTICAL HETERODYNE METHOD WITH A HIGH FINESSE INTRACAVITY RESONATOR

A novel highly sensitive method to detect the concentration of trace g as for environmental purposes is proposed. This method includes the ap plication of frequency modulation for stabilization of laser frequency , together with optical heterodyne measurement. The shift of resonance frequency of the Fabry-Perot cavity resonator is due to the change of refractive index, accompanied by the dispersion effect due to the pre sence of a target gas (e.g., methane, carbon dioxide or nitrogen dioxi de) inside the Fabry-Perot cavity.