Orientation and Motion of Water Molecules at Air/Water Interface

Analysis of SFG vibrational spectra of OH stretching bands in four experimental configurations shows that orientational motion of water molecule at air/water interface is libratory within a limited angular range. This picture is significantly different from the previous conclusion that the interfacial water molecule orientation varies over a broad range within the vibrational relaxation time, the only direct experimental evidence for ultrafast and broad orientational motion of a liquid interface by Wei et al. [Phys. Rev. Lett. 86, 4799, (2001)] using single SFG experimental configuration

Ultra-weak intrinsic FP cavity array for distributed sensing

This Letter reports on an ultraweak intrinsic Fabry–Perot interferometer (IFPI) array fabricated by a femtosecond (fs) laser for distributed sensing applications. Ultralow reflectors (\u3c - 60dB) were obtained. IFPIs with different physical lengths showed identical temperature sensitivity (-1.5GHz/°C). A distributed temperature sensing test was conducted. No crosstalk between IFPS elements in the array was observed, implying the device\u27s utility as a distributed sensing system. The possibility of using smaller bandwiths for sensor interrogation was experimentally proven. A small-scale temperature distribution test was conducted on a continuously cascaded ultraweak IFPI array, demonstrating its high spatial resolution. The temperature detection limit of this system was measured to be less than 0.667°C

THz Fiber Bragg Grating for Distributed Sensing

This letter reports a fiber Bragg grating for distributed sensing applications fabricated using single-mode optical fiber and a femtosecond laser and interrogated in the terahertz range. A theoretical model of device behavior was derived, which agreed well with experimentally observed device behavior. In order to investigate the utility of terahertz fiber Bragg gratings (THz FBGs) as a sensing modality, temperature tests were conducted. The results demonstrated a sensitivity of -1.32 GHz/ºC and a detection resolution of less than 0.0017 ºC. A temperature distribution test was also conducted using a THz FBG, demonstrating its potential as a distributed sensing platform with high spatial resolution. The feasibility of interrogating THz FBGs using narrow interrogation bandwidths was also experimentally shown