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The one-dimensional nonlinear photonic crystals containing defects that are embedded in air are investigated.However,attributed that the reflective second harmonic wave is so strong that it can not be ignored,the slowly varying amplitude approximation is not applicable to such a system.The paper presents a general solution of second harmonic generation without adopting the slowly varying approximation when the incident light is obliquely launched upon the one-dimensional inhomogeneous systems.The result shows that the wavelengthes corresponding to the defect modes shift to the short-wavelength with the increasing angle of incidence.The broadened band width second harmonic generation with high conversion efficiency can be achieved by modulating the angle of incidence of fundamental wave.Furthermore,this method can be applicable to any one-dimensional inhomogeneous systems and the conversion efficiency of second harmonic generation can be easily and conveniently calculated.

In order to improve the stability of Traditional Chinese Medicine′s fluorescence fingerprint spectra of constructing images and data processing efficiency,Liquid Crystal Spectrometer was used to detect spectral image of Cortex Phellodendri and Total Saponins of Panax Ginseng.Effective pixels were extracted using the combination of filter and localizing pixels means,besides,their pixels′ spectral images were obtained to draw Traditional Chinese Medicine′s fluorescent fingerprints correspondingly.Considering their Euclidean distance,when compared the three methods,the combination of filter and localizing pixels means has the best fluorescence fingerprint and spectral stability,followed by the background differencing,then is the optimization of pixels.By experimental results,it is revealed that spectral stability by this way is better and can be used to build Traditional Chinese Medicine′s fluorescent fingerprints.Based on these points,a new approach used for collecting effective pixels during Traditional Chinese Medicine′s fingerprints construction is proposed.

In order to increase the second harmonic generation conversion efficiency,the periodic optical superlattice was sandwiched with nonpoled and nonlinear media with finite and variable width,which can bring about the significant modulation for the fundamental wave with changing the thickness of the additional media.It is found that: the conversion efficiency increases or reduces when the energy of fundamental wave increases or reduces;it can be enhanced significantly when transmission resonance(the rate of transmission obtains 1) takes place;compared with the conventional sample(the optical superlattice embedded in infinite and nonlinear media),the second harmonic generation conversion efficiency is enhanced 1.5 times at most;for the practical sample(the optical superlattice embedded in air),it can be enhanced 3.3 times at most.So the second harmonic generation conversion efficiency can be enhanced apparently by the transmission resonance.

The effective refractive index of finite one-dimensional photonic crystal(PC) was investigated.Firstly,the concept of a complex effective refractive index for the structure of finite periodic PC was introduced.Then the complex transmission coefficient was calculated by using the transfer matrix method.On this basis,analytical expression of the effective refractive index could be derived.Considered by the spatial structure of photonic crystal and the existence of photonic band-gap,the characteristics of photonic band-gap structure,the effective refractive index,optical thickness,physical thickness and the center wavelength were investigated.It is found that amplitude of oscillation for the effective refractive index can be effected by the ratio of refractive index of the basic periodic structure and the physical thickness of the basic periodic structure of PC;Center wavelength has no effect on the effective refractive index.