Improvement of electro-optic effect and novel waveguide structure in hybrid polymer/sol-gel modulators

A thermally stable crosslinkable electro-optic (EO) polymer is successfully contact-poled in a hybrid EO polymer/sol-gel waveguide modulator. The highest EO coefficient is demonstrated when the EO polymer is poled with a low resistivity sol-gel cladding layer. We achieve the highest in-device EO polymer r(33) coefficient of 170pm/V at 1.55 mu m, which has not been possible with previously reported polymer claddings. A sol-gel waveguide/cladding plays the main role in our hybrid approach not only for poling efficiency, but also for low coupling loss, and stable coupling and waveguiding. The coupled light from the optical fiber propagates through the sol-gel input waveguide and adiabatically vertically transits between the sol-gel core and the EO polymer core. A phase modulator and a Mach-Zehnder modulator with a 2.4cm-long electrode and an inter-electrode distance of 15 mu m demonstrated a half wave voltages (V-pi) of 2.5V and 1.0V at 1.55 mu m, respectively. We also examine a push-pull poled Mach-Zehnder waveguide modulator.