Compensation and control of the birefringence of polymers for photonics

We demonstrated that a method based on the analysis of both orientational birefringence (intrinsic birefringence) and photoelastic birefringence (photoelastic coefficient) is effective for designing polymers that are processed in a molten state and used in a glassy state. The designed polymer exhibits no birefringence for any orientation of the polymer main chains or under elastic deformation. Birefringence is close to zero even in injection-molded plates of the polymer. We have also shown that it is possible to compensate and control birefringence of polymers using inorganic nanocrystals, and we have obtained valuable information on the optimal size of nanocrystals for compensation and control of birefringence. Nanocrystals measuring ∼200 nm in length and 20 nm in width are sufficiently small to compensate for birefringence, but sufficiently large to permit control of orientation by casting. Reverse birefringence wavelength dispersion of a polymer film containing nanocrystals was achieved by casting and heat drawing.