Research On Diffraction Effect Of LC-SLM And Its Applications

With the wide application of DWDM and the huge increase of fiber-optic capacity, SDH are overburdened, the third generation multifunction ROADM based WSS is increasingly becoming the key device of next dynamic generation all-optic-network, have obtained much attention in the field of optical research institutions. The WSS based LC-SLM have the features of colorless, directionless, contentionless and high flexible spectrum, so WSS have become the major research emphasis home and abroad.This paper developed the WSS experiment prototype using the simple optical systems based on theoretical analysis method combined with numerical simulation calculation. The main points of this paper are as follows:(1) A brief introduction of the liquid crystal spatial light modulator development is given. Based on the liquid crystal electro-optical properties, the amplitude and phase modulation of liquid crystal and the structure of liquid crystal spatial light modulator are analyzed in detail. Different polarization states and light intensity of output light throughout the liquid crystal are calculated by the theory of Jones Matrix.(2) Based on the theory of scalar diffraction, a model is established to investigate the diffraction efficiency of liquid crystal spatial light modulator load blazed grating image. An analytic expression of diffraction efficiency is deduced in spatial domain and frequency domain.(3) We use the Twyman-Green interferometer to measure the phase modulation characteristics and utilize MATLAB procedure to carry on the numerical evaluation. By processing data measured, drawing out the phase modulation curves of phase-only liquid crystal spatial light modulator. With analysis and calculation, we optimize the phase modulated curves, modify the Look-up table, and advance the diffraction efficiency.(4) According to the analysis of theory, the experimental system of liquid crystal based Wavelength Selective Switch is built and demonstrated, finally realized the basic functions of1×30WSS, the software of Java language to control the liquid crystal spatial light modulator is written. Therefore this paper provides theoretical basis and key techniques for developing a prototype of wavelength selector switch.