With renewed refractive indices, the potential of a solid solution LiGaS 2 : LiGaSe 2 → LiGa(S 1−x Se x ) 2 ( x = 0 − 1) in optical frequency conversionespecially in phase matching and group velocity matching-is theoretically investigated, together with the composition ratio limitation. It is found that the solution has excellent features for generating coherent ultrafast mid-IR sources covering 8-11 μm, which can be realized by type II down-conversion in the ba-plane with perfect group velocity matching, or type I in the bc-plane with part group velocity matching. This will have broad applications in LiDAR monitoring and precision spectroscopy, as well as life and environmental sciences.
Based on newly improved optical parameters of the excellent biaxial crystal LiGaS 2 , its phasematching upon second harmonic generation and general parametric processes are investigated. In particular, the issue of optimal phase-matching is solved by a computation on figureof-merit (FM). It is found that the effective fundamental wavelength of second harmonic generation entirely covers the 3-5 µm atmosphere window and mid-IR signals of 2-12 µm can be generated by suitable parametric processes. Analysis of the FM and dispersion verifies a quite effective type II parametric process: from a pump in the range of 0.8-1.0 µm to an ultrashort pulse generation at 6-12 µm and also suggests a type I pump at 1.7-1.9 µm for 3-5 µm pulse generation. The computation definitely renders an optimal phase-matching in the XY principal plane for type II configuration, or in a special direction for type I case, far away from the commonly used XZ principal plane.
Three kinds of phenols, namely gallic acid, syringal alcohol and ferulic acid, were selected as laccase natural mediator to investigate the changes of fiber surfaces, morphological properties of fibers, kappa number and physical properties of OCC (Old Corrugated Containers) pulp with laccase/ natural mediator system treatment. It was illustrated that condensation reaction of phenols could be occured by catalytic oxidation of laccase. The results of fiber quality analysis and SEM observation showed that after treated using laccase/ natural mediator system, the resultantly yielded OCC pulp had much smoother surface, larger fibers coarseness, higher kappa number, and the auto-adhesion of fibers could be observed in the fibers. In additon, the wet strength of handsheets, especially the wet ring crush strength, was improved obviously, compared with control sample.
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