Design And Research On A Surface Plasma Filter Based On Photorefractive Effect

In the branch of the optical communication development, there is a new technology- the Visible Light Communication(Visible Light Communication, VLC) that used of Visible Light as the transmission medium. It was suitable for short distance wireless communication and could take the place of Wi-Fi wireless communication, and deal with the “last mile” in wireless communication. the The essay based on the lithium niobate crystals(LiNbO3) as photoelectric materials which was attached the metal medium silver, designed and researched a filter that based on photorefractive effect and surface plasma resonance in the area of VLC communication.First of all, it studied the dispersion relation of surface plasma wave and the analysed about the theory of photorefractive effect. It also calculated the characteristic parameters of the surface plasma wave. Starting from the theory, it deduced the physical condition of photorefractive-plasma resonance. Based on one of dimensional refractive index modulation from lithium niobate(LiNbO3) crystal phase grating, put forward the composite index of refraction on the state of photorefractive grating in lithium niobate(LiNbO3) crystal. Furthermore, it deduced the sensitivity of the surface plasma resonance wavelength that corresponding to the half angle of dual beam. So it provides theory foundation for simulation about the subsequent photorefractive-plasma filter.Secondly, it designed the photorefractive plasma filter. Put forward the photorefractive plasma filter structure,designed the state of lithium niobate crystal that written grating. Through simulation, found that the surface plasma resonance angle was equal to the incident angle that was calculated from the matching wave vector formula. After simulation,the value of the angle is 46 degrees. Through the orientation of the poynting’s vector, it proved the existence of the surface plasma resonance wave. Finally, light the range from 500 nm to 760 nm incidented into the surface of the structure at fixed degrees. Taking the half of the angle that was written grating were 45°, 50° and 55° respectively。Through spectrum, it occur an obvious reflection minimum at 668 nm, 654 nm and 643 nm respectively. In conclusion, the result showed that the change of photorefractive grating period, corresponding to the surface plasma resonant wavelength was shift.Finally, designed the photorefractive plasma filter experiment scheme and analysed the experimental result. The experimental process involved the manufacture of device and measurement. As same as simulation’s operation, the half of the angle that is written grating were 45°, 50° and 55° respectively, in experimental result, the surface plasma resonant wavelength were 700 nm, 694 nm, 690 nm respectively. At last, analysed the key factors of experiment and put forward the improved experiment.