Progress towards dual vertical slot modulator for millimeter wave photonics

Dual vertical slot modulators leverage the field enhancement provided by the continuity of the normal electric flux density across a boundary between two dielectrics to increase modal confinement and overlap for the propagating optical and RF waves. This effect is achieved by aligning a conventional silicon-based optical slot waveguide with a titanium dioxide RF slot. The TiO2 has an optical refractive index lower than silicon, but a significantly higher index in the RF regime. The dual slot design confines both the optical and RF modes to the same void between the silicon ribs of the optical slot waveguide. To obtain modulation of the optical signal, the void is filled with an organic electro optic material (OEOM), which offers a high optical non-linearity. The optical and RF refractive index of the OEOM is lower than silicon and can be deposited through spin processing. This design causes an extremely large mode overlap between the optical field and the RF field within the non-linear OEOM material which can result in a device with a low V-pi and a high operational bandwidth. We present work towards achieving various prototypes of the proposed device, and we discuss the fabrication challenges inherent to its design.