Recent advances in polymer integrated-optics technology

Traditional EO polymer modulators employ a Mach-Zehnder interferometer architecture with only one arm modulated under a microstrip line electrode. The V/sub /spl pi// of such modulator can be expressed as, V/sub /spl pi//=/spl lambda/h/n/sup 3/r/sub 33/L/spl Gamma/ (Eq. 1) where /spl lambda/ is the optical wavelength, h is the gap between electrodes, n is the index of refraction, r/sub 33/ is the EO coefficient of the polymer waveguide layer, L is the interaction length, and /spl Gamma/ is a modal overlap integral. Low V/sub /spl pi// can be achieved by adjusting one or several parameters in Eq. 1. However, many factors such as reducing the gap distance or increasing the interaction length are limited by optical insertion loss and modulation frequency requirements. The most effective approach for low V, is to increase the EO coefficient r/sub 33/, and recent work at the University of Southern California has demonstrated some limits to increasing the doping density of the nonlinear chromophores.