Fig. 3.

Schematic of the cantilever-enhanced DC-PAS. CW laser－continuous wave laser, AOM－acousto-optic modulator, EOM－electro-optic modulator, EDFA－erbium-doped optical fiber amplifier, PD－photodetector, DAQ－data acquisition. (a) A dual comb interacts with gas molecules in a non-resonant PAC, the multiheterodyne sound waves push the multimode vibration of the cantilever. A probe laser is irradiated to the interface of the cantilever. The intensity changes of the probe laser are detected by PD2 and then recorded by DAQ. (b) Image of the non-resonant PAC. It consists of the fiber interfaces of the CW laser and the probe laser, as well as the inlet and outlet of the gas. (c) Schematic structure of FPI cantilever sensor head. The sensor head is composed of a stainless-steel shell, a fiber, a ceramic ferrule and a cantilever. (d) Image of the cantilever. The cantilever which is manufactured by laser micromachining technique, has a size of 2 mm × 1 mm and a thickness of 10 μm.