Search

We propose a high sensitivity fiber optical temperature sensor with simple structure. The sensor is composed of a multimode fiber (MMF) and a short single mode fiber (SMF) whose end is coated with silver film as a reflective mirror. Due to the mismatch between the MMF core and the SMF core, part of guided mode is coupled with the cladding modes of downstream SMF cladding. The mode index difference between the fiber core and cladding is attributed to the phase difference, resulting in interference. When ambient temperature increases, the interference spectrum presents red-drift because of the difference in thermo-dependence. A high temperature sensitivity of 120 pm/℃ is achieved, and the linearity is 99.5%. The configuration is simple and has a compact size, making it a good candidate for distant temperature sensing and oil prospecting.

In order to trap more sunlight onto the crystalline silicon solar cell and improve the photo-electric conversion efficiency, it is very important to study the optical scattering properties of silicon nanowire arrays on silicon wafer. The rigorous coupled wave analysis method is used for optical simulation, and the Taguchi method is used for efficient optimization. The simulation results show that at the above-mentioned wavelengths the reflectance of the optimized structure is less than 2%, and also able to achieve the wide-angle antireflection. At room temperature and ambient pressure, the silicon nanowire arrays each with a period of 50 nm, duty ratio of 0.6 and height of 1000 nm are successfully prepared on mono-crystalline Si wafers using a novel metal-catalyzed chemical etching technique, the reflectance test results are consistent with simulation values. The average reflectance of the optimized structure over the above-mentioned wavelength range is 4%-5%, showing that the antireflection effect is obvious compared with the reflectivity of about 35% of the single crystal silicon. The minus reflection microstructures reduce the sun battery microstructure costs, at the same time, reduce the monocrystalline silicon surface light reflecting loss, improve the photoelectric conversion efficiency.

Based on the structure health monitoring of civil engineering structure such as bridges, dams, high-rise building, the fiber Bragg grating sensor is used to achieve the real-time monitoring and diagnosis of structural performance, in order to discovery the damage and to evaluate the safety of structure. Fiber-optical grating sensing based on flextensional member is proposed. The measuring of pressure, strain and acceleration can be realized. The strain of camber beam belly is analysed theoretically and verified experimentally. The strain of the camber beam belly is proportional to the pressure and acceleration in the vertical direction. Its biggest advantage is small size under the same sensitivity. The transverse dimensions is limited in well and the longitudinal acceleration needs to be measured, so beam based sensor structure are not likely to be used. Under the condition of measuring longitudinal acceleration sensor structure, beam pumping are not likely to be used. This new type of flextensional member elastic sensitive structure can serve as elastic element for the design of fiber bragg grating strain, weighing and pressure, and acceleration sensor.

The effect of background beam with different Glass constant on the relative spatial refractive perturbation in photovoltaic crystal was discussed, in which was introduced the concrete conditions for the formation of bright or dark photovoltaic spatial solitons in crystals with negative refractivity change. Based on the results, for what is to our knowledge the first time, the bright photovoltaic solitons was experimentally observed in LiNbO3:Fe by use of e-ray signal of 532nm and o-ray background illumination of 488nm.