90GHz Optical Phase Modulator Using Slotted Patch Antennas on Thin LiNbO_3 Optical Crystal

摘要

An optical phase modulator using slotted patch antennas on a thin LiNbO_3 optical crystal is proposed for operation of 90GHz millimeter-wave bands. Slotted patch antennas and straight optical waveguides are fabricated a low-k dielectric material (ε_r ～ 4 and h_L ～ 120μm) suspended with the thin LiNbO_3 optical crystal (h_(EO) ～ 20μm). They are bonded with a thin transparent ultra-violet (UV) adhesive glue {h_G ～ 20μm). Since low effective dielectric constant of the bonded substrate, large antenna size and long interaction length between millimeter-wave and lightwave electric fields are obtainable. Additionally, the thin LiNbO_3 optical crystal located on the slotted patch antennas is used also for the dielectric superstate to enhance antenna performance in further. Optical phase modulation can be achieved effectively along the optical waveguide located on the slotted structure of the patch antennas. Therefore, free space wireless millimeter-wave signals can be received by the antennas and converted to lightwave signals through electro-optic linear effect of the optical crystal. Analysis for its characteristics and fabrication processes of the proposed device for 90GHz millimeter-wave bands are discussed and reported.