Effect of Fabry-Perot Structure on Electroabsorption and Quadratic Electro-optic Modulation in the Nonconjugated Conductive Polymer Iodine-doped Polyethylene Terephthalate (PET).

Determination of the real part of Kerr coefficient in the nonconjugated conductive polymer iodine-doped polyethylene terephthalate (PET) has been recently reported.¹ In this report, we discuss the imaginary part of Kerr coefficient of iodine-doped PET determined by measuring electroabsorption at 633 nm wavelength for two different doping levels. The magnitudes as obtained are: ~ 2.3x10^-12 m/V² for low doping and ~ 1.7x10^-11 m/V² for high doping respectively. These are exceptionally large magnitudes and are due to the subnanometer sized quantum dots in nonconjugated conductive polymers.² At low doping and higher fields we observed electric field-induced hysteresis / bistability in the electroabsorption data. Also, at medium / high doping and relatively higher fields we observed hysteresis / bistability in the quadratic electro-optic (dispersive) measurements. This is the first time electric field induced bistabilty observed for a plastic film. These are due to the large optical nonlinearities produced by subnanometer quantum dots in these doped polymers and existence of a feedback system involving Fabry-Perot structure in the film having optically smooth surfaces. These novel results should lead to new fundamental insights and photonic devices involving these plastic films. More detailed studies of these novel characteristics are in progress.