Silicon Ring Optical Modulator with p/n Junctions Arranged along Waveguide for Low-Voltage Operation

For low-voltage and high-speed operation, a Si ring optical modulator, where p/n junctions are arranged along the waveguide of the ring resonator, is proposed. In this device, a switching speed of over 30 GHz and a modulation of 3 dB are estimated at a low operation voltage of 1 V by simulation. Optimum design parameters are obtained: the carrier concentration is 1 x 10(18) cm(-3) and the length of the p- and n-type regions is 0.4 mu m. The modulators were fabricated and the performance was evaluated. The modulation is 1.25 dB at 6 V, which is lower than the simulated value. This is explained by the unexpected low carrier concentration. It is suggested that the optimization of the fabrication process will yield better performance. (C) 2012 The Japan Society of Applied Physics