| Electro-optical effect can be used to modulate optical intensity, phase, polarization, frequency and direction. Which has been widely used in photoelectron elenements such as optical switch, modulator, bistable optical device, spatial light modulator and waveguide. The current electro-opticical crystals and polymer composite thim film have many disadvantages such as low electro-optic coefficient, difficult to prepare or with weak chemical, poling and orientational stability,so finding new electro-optic materials is a significant orientation. In this paper we combine both electrostrictive and stress birefringence materials, and prepare new electro-optic composites by using stress coupling method. The structure of composites is simple and easy to be prepared, and can probably offer a new idea to development of electro-optic materials. Since the properties of layered composites depends on the product effect of electrostrictive and stress birefringence effects, beautiful electro-optic properties can be expected by rationally choosing materials.There are lots of impact factors for property of layered electro-optic composites, such as performances of electrostrictive phase and stress birefringence phase, volume fraction and interface coupling, so it does require a theoretical model to study the property and variety regulation. The paper introduces how to deduce and analyze transverse electro-optic coefficient of free double-layered and triple-layered electro-optic composites, with constitutive equations of electrostrictive and stress birefringence phase and using elastic mechanics models. Transverse electro-optic coefficients of Pb(Zr,Ti)O3- Polycarbonate (PZT-PC) and PZT-PC-PZT was calculated in the paper by the corresponding parameters, and we analyzed the relationship between electro-optic coefficient and factors such as thickness and volume fraction of stress birefringence phase, voltage and wavelength of light resource. The results revealed that piezoelectric strain coefficient of electrostrictive phase, stress-optic constant of stress birefringence phase, proper volume fraction and better interface coupling are the key factors of electro-optic properties in layered electro-optic composites. In the paper electro-optical effect of layered composites depends on the product effect,which stems from stress coupling, in theory we discussed gradient effect of stress and the influence on electro-optic coefficient, this is quantitatively analyzed to gradient effect of layered composites for the first time, which has important significance for some product effect in composite (magnetoelectric effect, for example).Because of having electric hysteresis of field strain curve of electrostrictive phase, electro-optic curves in the experiment exist double-valued property, in other words, the same electric field strength corresponds to two values of light transmission. It is possible be used in bistable optical device. Electro-optic uniformity of composites is affected by proper annealing treatment and height of stress birefringence phase PC, it is found that electro-optic uniformity and stability is better when the height of PC is 1.5mm in the experiment. For PZT-PC-PZT composites with a thickness of 3mm, electro-optic coefficients?vary from 23 to 29pm/v in the range of d1/d3 from 0.15 to 0.5. these values are about 4 times higher than?22=6.8pm/v of LiNbO3.In the experiment it is found that electro-optic coefficients at high frequencies are much higher than these at lower frequences, which achieve 100-250pm/v when modulation frequence in the range from 20khz to 1.5Mhz. This property is quite different from which in current electro-optic materials and is truly significant. We think change of coefficient is relevant to dielectric resonance, and according to which suggesting some methods to increase upper limit of working frequency for electro-optic composites, such as size change of sample. |
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