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_π of such modulator can be expressed as, V_π=λh/n³r₃₃LΓ (Eq. 1) where λ is the optical wavelength, h is the gap between electrodes, n is the index of refraction, r₃₃ is the EO coefficient of the polymer waveguide layer, L is the interaction length, and Γ is a modal overlap integral. Low V_π 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 r₃₃, and recent work at the University of Southern California has demonstrated some limits to increasing the doping density of the nonlinear chromophores