Study Of Tunable Fabry-perot Filter Based On Piezoelectric Polymer Film

Optical communication system has promoted the continuous development of WDM technology, which also promoted development of optical devices including optical filters. Tunable Fabry-Perot Filter (FPF) has high practical value in optic communication. So far, FPF has been studied a lot at home and abroad. FPFs with different modulation principles have their own advantages and disadvantages in the modulation range, response speed and insertion loss, so the filters have been used in different situation. The PVDF and its copolymers have also been studied widely for the characteristic of flexibility and easy production in large scale, during which the electrostrictive effect of PVDF copolymers has been especially studied recently. In this paper, the electrostrictive effect of piezoelectric copolymer P (VDF-TrFE), which is the copolymer of vinylidene fluoride (VDF) and trifluoro ethylene (TrFE), is applied as spacer in a F-P filter. This filter is a high -performance filter tunable in a wide spectrum.The structure of the device is designed considering all the effects that may exist in the device. As a result, the filter has been fabricated with the structure of DBR/electrode/spacer/electrode/DBR, in which P (VDF-TrFE) is designed as the spacer layer material to obtain large tunability in wide range because of its great electrostrictive effect. The copolymer is etched partly at where the light traverses to avoid the electro-optic effect. Advantages of this structure include the exclusion of electro-optic effect and the improvement of the voltage utilization. All the production processes are the conventional processes which will not increase the cost of the device.Two filters are fabricated in infrared band, one etched and the other not. The performance of the two devices is studied. The comparison of performance verifies the structure we designed of FP cavity is conducive to improvement of transmittance and other indicators of the filter. Filters with air spacer in both visible and infrared bands were produced to study the F-P cavity performance in different bands. The effects of different fabrication process to the filter performance are discussed.FPF with air spacer is modulated by additional voltage and the transmittance spectra have been studied. The resonant wavelengths have been modulated by the applied voltage. The optical length is measured to be 8.04μm ,which shrink under an electric field. The filter exhibits a total optical path-length change of -0.757% under an electric field of 47V/μm. The results indicate that the electrostrictive effect play a major role.The results indicate that the piezoelectric electrostrictive effect of piezoelectric polymers can be used to make tunable filters, which can be modulated in wide spectra, and there is further room for performance improvement. In addition, polymers have the advantages of easy processing, resulting in better application prospect.