Effect of conductivity and dielectric constant on the modulation voltage for optoelectronic devices based on nonlinear optical polymers

Abstract

Presented is the effect of using various cladding materials with different conductivities and dielectric constants on the applied voltage for optoelectronic (OE) devices based on nonlinear optical (NLO) polymers. Using a conductive polymer, we have demonstrated a 3 to 13 times increase in the effective electro-optic (EO) coefficient of electrode- poled NLO polymers, compared to using passive polymer claddings. We have achieved the lowest poling voltage to date for maximum EO coefficient, 300 V, for a two-layer waveguide structure consisting of a 2-?m- thick NLO polymer layer and a 2-?m-thick conductive cladding layer. The dielectric constants of both the NLO polymer core and passive polymer cladding materials used for conventional polymer-based integrated optic devices are typically very similar in magnitude. This suggests that only a small fraction of the applied modulation voltage is reaching the NLO polymer core layer, requiring 4 to 5 times higher modulation voltage than the desired V?. We have demonstrated a factor-of-2 decrease in the modulation voltage using the same conductive polymer, due to its possessing a much higher dielectric constant than the core material at the modulation frequency tested. The results show promise for shorter, lower-operating-voltage devices.