Ultra-high sensitivity frequency-comb-referenced multi-parametric sensors based on 1-D photonic components

A novel generation of sensors of strain, temperature, absolute and relative molecular concentration is reported. Such devices, based on 1-D photonic structures, rely on ultrastable laser sources, referenced to a fiber-based optical frequency comb synthesizer (OFCS). In particular, recent advances in the realization of two complementary laser sensors are presented. One is a spectroscopic facility which exploits frequency mixing in a periodically-poled LiNbO3 crystal to generate highly coherent (a few hundred kHz linewidth) infrared radiation tunable in the 2.9-3.5 micron wavelength range. Such radiation can be coupled to high-finesse enhancement cavities to detect trace amounts of gases, including rare isotopes in natural abundance. The other system, making use of fiber Bragg grating components, provides strain and temperature sensing with extremely high sensitivities (about 100 f[, i.e. 10-13 ”L/L). Due to the remoteness guaranteed by the fiber coupling, these two systems can both be used in difficult environments and inserted in a multi-parametric network for real-time and continuous monitoring of large areas. Prospects for application in volcanic areas are also discussed.