The Si-Photonic Modulator Using Three- Waveguides Coupler Structure

We proposed and demonstrate the Si-modulatorusing three-waveguides coupler structure for the first time. Byusing three-waveguide structure can decrease the couplinglengthcontrary to conventional directional coupler structure. Forthe modulation operation, pn diode is employed to have junctionat the only one waveguide. The proposed structure wasfabricated using CMOS-compatible process and shows thecompact device size about ~500 μm2 which is much smaller thanMZI modulator structure. By applying forward bias voltage of1.2 V, π-phase shift is achieved with Vsw∙L ~ 0.23 V∙mm. Finally,it shows operation speed up to 3 Gbps with extinction ratio of 3dB which is faster than carrier injection using p-i-n diode. Itcanaffordable for the operation speed up to 3 Gbps using carrierinjection of pn diode by applying forward bias. We expect thatperformance of device can be enhanced using more sophisticatedfabrication process and can be used as the new structure of Siphotonicmodulator