Ni Pei-Gen

Formation Process of a TiO2 Inverse Opal

Inverse opals of TiO2 with different filling fractions were fabricated by using an opal of polystyrene spheres as a template. Scanning electron microscopy showed the accumulative process of TiO2. The transmission spectra of inverse opals with different filling fractions were measured and the shifts of transmission dip with the filling fraction were observed. Our investigation made the infiltration process clear, and it might be helpful for further improvement of the fabrication of TiO2 inverse opals.

Tow-Dimensional Micro-grating Formed by Polystyrene Spheres

We report a simple method to make two-dimensional plane gratings that can be used as splitters. In the self-assembly process, the colloidal spheres can form single layer square or triangular lattice on a flat surface and in our experiments the triangular lattice is a more common structure. As an incident beam passes through the triangular lattice, it can be split into seven sub-beams, among which six beams have the same density and scattering angle. This grating is not sensitive to the polarization direction of the incident light.

A Two-Dimensional Nonlinear Photonic Crystal with a Rectangular Loop

A novel model of two-dimensional periodically poled lithium niobate designed for second harmonic generation of 1064 nm is proposed, in which a rectangular light route is used. The effective length of the sample is longer than the sample real length by (5/3).21/2 times. The conversion efficiency enhances greatly without prolonging the periodically poled crystal length.

High-Order Stimulated Raman Emission and Two-Photon Stimulated Emission by Photodissociation of PbI2 Molecules

When focusing YAG laser pulses at 266 nm into a heat-pipe oven containing PbI2 molecules vapor, four red line emissions at 626.0, 619.8, 613.7 and 621.8 nm are observed. The photodissociation mechanism of PbI2 molecules and the possible generation channels of these four line emissions are given. Moreover, the dependence of the emission at 626.0 nm on incident laser energy and heat-pipe temperature is measured. The experimental observation is well supported by the photodissociation mechanism proposed by us.

Stimulated Emission at 722.9 nm by Laser Photodissociation of PbI2 Vapor

The stimulated emission at 722.9 nm is observed by a direct photodissociation of the PbI2 molecules with a 266 nm pulse laser. The possible dissociation channels are discussed. Two-photon resonant photodissociation mechanism is used to explain the generation of the 722.9 nm emission. The emission is measured at different incident laser energy and heat-pipe temperature. The obtained experimental result is well supported by the photodissociation mechanism given by us.