The nonlinear metamaterials have been shown to provide nonlinear properties with high nonlinear conversion efficiency and in a myriad of light manipulation. Here we study terahertz generation from nonlinear metasurface consisting of single layer nanoscale split-ring resonator array. The terahertz generation due to optical rectification by the second-order nonlinearity of the split-ring resonator is investigated by a time-domain implementation of the hydrodynamic model for electron dynamics in metal. The results show that the nonlinear metasurface enables us to generate broadband terahertz radiation and free from quasi-phase-matching conditions. The proposed scheme provides a new concept of broadband THz source and designing nonlinear plasmonic metamaterials.
A quaternary ammonium derivative of konjac glucomannan (KGM) was prepared by a dry process from KGM and 2,3-epoxypropyl trimethylammonium chloride. We determined the optimization of the experimental conditions by studying on the effects of the water amount, alkaline catalyst amount, reaction temperature, and reaction time on the degree of substitution. In addition, the flocculation characteristics of the cationic derivative of KGM were evaluated in a 1.0% kaolin suspension with spectrophotometry via investigation of the influence of the flocculant amount, pH, salt concentration, temperature, and settling time on the flocculation. The results show that the synthesized cationic KGM could potentially be used as a high-performance flocculating agent.
A cantilever fiber-optic accelerometer using modal interferometer, with a large fringe visibility of up to 30dB, is proposed and demonstrated. In the system, an electrical testing replaces optical-spectrum detection to achieve fast acceleration measurement of the cantilever fiber-optic accelerometer, and the performance of the cantilever fiber-optic accelerometer is studied experimentally. Experimental results show that the minimum detectable acceleration is 1.36mg, and the resonance frequency is 520Hz. Meanwhile, the angular dependence of the fiber accelerometer is also analyzed in the article and the result shows that the output intensity difference is up to 18dB for different angles. This fiber-optic accelerometer can be used to detect underwater acoustic and seismic wave.Index Terms-Fiber-optic accelerometer, cantilever, modal interferometer, Integrated optics devices.I.
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