Low-voltage linear silicon optical modulator with a single-drive parallel-push-pull scheme

We demonstrate a single-drive parallel-push-pull silicon optical modulator. Compared with the serial-push-pull scheme, the parallel-push-pull scheme allows the driving signal to be applied on both the arms without division. It makes the device suitable for low-voltage driving. Since the electrode drives two PN junctions at the same time, we dope the waveguides periodically in order to lower the capacitance per unit length of the loaded PN junction. This design could alleviate the matching requirement of the coplanar waveguide electrode. When optically biased at the quadrature point, the device has an extinction ratio of 3.1 dB at the speed of 20 Gbps and under the driving voltage of 1.8 Vpp. Benefitting from the push-pull scheme, its linearity performance is also improved. Compared with the device adopting the scheme with only one arm being driven, the spurious free dynamic ranges for second-order harmonic distortion and third-order intermodulation distortion increase by 11.5 dB and 2 dB to 101dB.Hz1∕2 and 113dB.Hz2∕3, respectively.