Design of a silicon Mach–Zehnder modulator with a U-type PN junction

We have developed a silicon depletion-mode modulator featuring a novel U-type PN junction that enables a substantial improvement in electro-optical modulation efficiency. Through electrical, optical, and manufacturing process simulations, an ultralow VπL of 0.63  V·cm is exhibited with 3 V reverse bias. The high modulation efficiency enables a high extinction ratio (ER) of >17  dB with only a 1 mm phase shifter when the excess loss at the “on” state is 2 dB. The ER can maintain >12  dB at ∼28  GHz operation with a 3 V peak-to-peak voltage due to the small voltage attenuation of the short phase shifter.