INTEGRATION OF AN ELECTROOPTIC POLYMER IN AN INTEGRATED-OPTICS CIRCUIT ON SILICON

This paper presents the joining of active nonlinear polymer [1], [2] w aveguides with passive silicon nitride waveguides (SiO2/Si3N4/SiO2) to form an integrated Mach-Zehnder modulator with a lateral electrode co nfiguration on a silicon substrate, Passive and active waveguides are based on a silicon-nitride-strip guiding structure. In the active wave guide a nonlinear polymer layer is used to obtain an index modulation via the electrooptic effect, Despite the silicon nitride strip based g uiding structure, 63% of the energy of the fundamental mode is guided in the nonlinear polymer (provided by Flamel Technology, Venissieux, F rance). Poling with held strengths up to 75 V/mu m applied to the late ral electrodes has been employed to orient the chromophores. A half wa ve voltage of 35 V has been measured for an electrooptic coefficient o f 5.8 pm/V at a wavelength of 1.3 mu m. Optical loss measurements have been done on polymer and passive waveguides, The best results have be en 1.8 dB/cm for the active and 0.78 dB/cm for the passive waveguides leading to a total loss of 6 dB for a modulator with an interaction le ngth of 2.5 cm. The coupling Loss between a laser diode and the passiv e waveguide structure was measured to be at least 4.6 dB using a micro scope objective and piezo-electric displacement elements. Stability te sts under atmospheric conditions have shown a decrease of the electroo ptic coefficient which might be due to the hygroscopic behavior of the active polymer. The bandwidth of the modulator has been determined to be 4 MHz.