Evanescent-wave type photoacoustic spectrum trace gas sensor based on optical fiber resonant cavity and measurement method

The invention discloses an evanescent-wave type photoacoustic spectrum trace gas sensor based on an optical fiber resonant cavity and a measurement method. The sensor is composed of a semiconductor laser source, an optical fiber combiner, a tapered optical fiber, a quartz tuning fork and a phase modulator. The measurement method comprises the following steps that (1) laser emitted by the semiconductor laser source is input into the optical fiber combiner, and the laser passes through the phase modulator, so that the optical fiber combiner is formed into an optical resonant cavity, and the laser power in optical fiber is amplified and enhanced, therefore a stronger optical evanescent field is generated in the position of the tapered optical fiber; (2) to-be-measured target gas absorbs the energy of an evanescent wave field in the position of the tapered optical fiber, so that an acoustic wave field is generated; the quartz tuning fork is used for detecting an acoustic wave signal and inverting gas concentration. The evanescent-wave type photoacoustic spectrum trace gas sensor based on the optical fiber resonant cavity and the measurement method have the advantages that the laser excitation power is effectively improved, therefore the detection sensitivity of a photoacoustic spectrum gas sensor is greatly improved.