Electrooptic Polymer Modulator With Single-Mode to Multimode Waveguide Transitions

Grayscale lithography has been used to create refractive index (RI) tapers in an electrooptic (EO) polymer modulator. These RI tapers are used to convert a passive single-mode photobleached polymer waveguide to the fundamental mode of an unbleached, active multimode polymer waveguide. The benefits of this modulator design include a coupling loss reduction of 2.6 dB per interface and an increased confinement factor of 0.83. Using this design, an EO polymer modulator was fabricated with a half-wave voltage of 1.9 V, modulation extinction ratio of 15 dB, and a fiber to lens insertion loss of 11.6 dB.