An electro-optic (EO) modulator using a TiO2 slot hybrid waveguide has been designed and fabricated. Optical mode calculations revealed that the mode was primarily confined within the slots when using a double-slot configuration, thus achieving a high EO activity experimentally. The TiO2 slots also acted as an important barrier to induce an enhanced DC field during the poling of the EO polymer and the driving of the EO modulator. The hybrid phase modulator exhibited a driving voltage (Vπ) of 1.6 V at 1550 nm, which can be further reduced to 0.8 V in a 1 cm-long push-pull Mach–Zehnder interferometer (MZI) structure. The modulator demonstrated a low propagation loss of 5 dB/cm and a relatively high end-fire coupling efficiency.

Figure 1:(a) Schematic and (b) TE0 mode distribution of the EO polymer filled TiO2 double-slot modulator when d = 150 nm; (c) single-slot structure and (d) its TE0 mode distribution are shown for comparison.

Figure 2: Calculated electrode absorption loss and light confinement versus slot width.

Figure 3: Simulated DC electrical filed distributions around the slots of the (a) double-slot and (b) single-slot modulator.

doi: 10.1038/srep08561