ELECTROOPTIC POLYMER MODULATORS OPERATING IN BOTH TE AND TM MODES INCORPORATING A VERTICALLY TAPERED CLADDING

We propose a modified electrooptic (EO) polymer waveguide structure su pporting both TE and TM modes in spite of the large birefringence indu ced by the poling. A vertically tapered structure is employed to conne ct a single-mode rib waveguide and a confinement-enhanced rectangular buried waveguide. This waveguide structure can be easily fabricated by a two-step RIE process with a shadow mask. To demonstrate TE/TM confi nement and single-mode operation, Mach-Zehnder intensity modulators ar e fabricated by incorporating the proposed waveguide structure. The ex tinction ratio is better than -15 dB, which proves the single-mode ope ration. Half-wave voltages for TM and TE modes are 6 and 24 V, respect ively.