Low-loss interconnection between electrooptic and passive polymer waveguides with a vertical taper

To enable the hybrid integration of the electrooptic (EO) polymer and the low-loss passive waveguides, a low-loss interconnection between the two waveguides is demonstrated based upon an adiabatic coupling in a vertically tapered waveguide. Fluorinated passive polymers incorporated in this device exhibits 0.35 dB/cm of propagation loss, and the EO polymer has an EO coefficient of 35 pm/V and a high thermal stability with a glass transition temperature of 200 degreesC. According to a beam propagation method simulation, the interconnection loss could be negligible if the taper length is longer than 300 mum. From the fabricated device, an interconnection loss of 0.4 dB is demonstrated by the cutback measurement of the waveguide loss.