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2005 Nuggets

Novel Electroactive Materials and Tunable Photonic Crystals
D. Jeong, Q. Chen, Y. Wang, Q. M. Zhang, V. Gopalan, S. Yin (PSU), G. Kavarnos (URI and NUWC), IRG3

Photonic crystals with large tunability are attractive for many important operations in optic communications including programmable filters, dynamic gain equalization and chromatic dispersion compensation. Among various methods, electric filed induced tuning offers many advantages. One challenge in achieving large tuning range by external fields in photonic crystals is the small strain (<0.1%) or refractive index change (<0.1%) in the currently available electroactive materials. Recently, based on first principles calculations, we predicted that there is a large electro-optic (E-O) effect in a P(VDF-TrFE) based polymer when undergoing a conformational change between the polar and non-polar forms (refractive index change ~ 10%). Indeed, we show that in P(VDF-TrFE-CFE) terpolymer in which a small amount of chlorinated termonomer is copolymerized with P(VDF-TrFE) to modify the phase stability between different conformations and create nano-polar phases, a large E-O effect can be realized. Furthermore, the terpolymer also exhibits large electrostrictive strain (Figure 1). Utilizing the P(VDF-TrFE-CFE) terpolymer, a 1.5D photonic crystal - a long period fiber grating (LPFG) is under investigation in which a refractive index change in the cladding can result in a large tuning. Photonic crystals with defects modes will be investigated in which the large tuning available can produce switching in the guided modes.