This paper investigates the photovoltaic properties of miscut LiNbO3 single crystal with different thicknesses under irradiation of a 248 nm ultraviolet laser pulse with 20 ns duration without an applied bias. Nanosecond photovoltaic response is observed and faster rise time is obtained in thinner samples. In accord with the 248 nm laser duration, the full width at half maximum of the photovoltaic signals keeps a constant of ~ 20 ns. With decrease of the crystal thickness, the photovoltaic sensitivity was improved rapidly at first and then decreased, and the maximum photovoltage occurred at 0.38 mm-thick single crystal. The present results demonstrate that decreasing the LiNbO3 single crystal thickness can obtain faster response time and improve the photovoltaic sensitivity.
The optical properties of four kinds of lubricating greases （urea, lithium, extreme pressure lithium, molybdenum disulfide lithium greases） with different NLGL （National Lubricant Grease Institute of America） numbers were investigated using terahertz time-domain spectroscopy. Greases with different NLGL grades have unique spectral features in the terahertz range. Comparison of the experimental data with predictions based on Lorentz Lorenz theory exhibited that the refractive indices of each kind of lubricating grease were dependent on the their consistency. In addition, molybdenum disullfide （MoS2） aa a libricant additive shows strong absorption from 0.2 to 1.4 THz, leading to higher absorption of MoS2-1ithium grease than that of lithium grease.
We investigate the diffusion interaction and quantitative analysis of zinc dialkyldithiophosphate （ZDDP） mixed with lube base oil （LBO） at different concentrations using terahertz time-domain spectroscopy （THzTDS）.When the concentration exceeds 6.78%,the characteristic absorption peaks exhibit significantly shift,and the absorption coefficient peak value is nonlinear against concentration.Moreover,the absorption coefficients of mixed samples follow the Beer＇s law at a concentration below 6.78%.The quantitative analysis enables a strategy for monitoring the formulation of lubricating oil in real time
