Investigation Of Polymer Dispersed Liquid Crystal Film Based On Novel Liquid Crystal Variable Optical Attenuator

With the development of optical fiber communications and application of Dense Wavelength Division Multiplexing, it is very important to equilibrium the channel power. The optical attenuator is a key device which acts to equilibrium power. It can adjust the power in the range of the require of clients in the optical fiber network. The attenuator can protect the receiver .With the development of optical fiber network, the attenuator should be made more title,more intelligence ,easy integrated. So many academies at abroad are concentrated on the research of the Variable Optical Attenuator, and have made a great deal of process. As a novel variable attenuator, polymer dispersed liquid crystal VOA have been researched by many institutions such as NTT, which use the optical scattering character of PDLC film. In our country the pure liquid crystal VOA has been researched. This kind of VOA needs a couple of polarize chips. Our device will use polymer dispersed liquid crystal instead of pure liquid crystal, which doesn't need any polarize chips. In this paper, our work is to process the key section of VOA-polymer dispersed liquid crystal materials, and include two parts: the first is effective medium theory of polymer dispersed liquid crystal droplet systems and the second is the process of PDLC film . In the theory ,we constructed a bipolar liquid crystal droplet model, and allowed the bipolar droplet axes to vary. The crucial physics in this paper involved a balance between energy, which favours orientation of a droplet with a local easy axis, and the electrostatics, which favours alignment with the field. We have found that once the droplet bipolar axis is allowed to rotate, it will do so in the presence of a sufficiently powerful electric field, leading to dramatic reorientation phenomena which will also exhibit an optical signature. The reorientation is threshold-like whit some hysteresis if the droplets are initially oriented in a ;lane perpendicular to the applied voltage. From this character, we can catch the essence of the electronic-optical character of PDLC film. And tutor our experiment. In the course of experiments, at the firstly, we use the ultraviolet polymerization induced phase separation to process the PDLC films. In order to sit the order of PDLC system, we selected the E7 as the liquid crystal materials. It has a high birefringence, which is 0.2246 and normal optical refraction index is 1.5216,which is suit to the fiber optical refraction index. After considering the optical polymerization rate,phase separation between polymer and liquid crystal.,the optical refraction between polymer and liquid crystal, we selected the polymer :MMA and Bisphenol A epoxy acrylat; photo-initiator:I-184 At the secondly, we got a high optical transmittance of PDLC film with a saturation voltage. After investigating the effect of the...