Design of high extinction radio silicon optical modulator at 2 μm using cascaded compensation method

Abstract

The effect of the free carrier effect is more significant in the mid-infrared band when compared with the 1310 band and 1550 band. In this paper, we propose a cascaded Mach-Zehnder interference (MZI) structure to improve the extinction ratio (ER) of the modulator in the mid-infrared band. The cascaded compensation method is to add the next-stage equal-arm MZI device to the two phase shifters of the major MZI. The output light intensity of the two phase shifters can be maintained at the same level by adjusting the output loss of both the equal-arm MZI. With the cascaded compensation method, the simulated ER of the optical modulator is increased from 36 dB to 55 dB under −4 Vbias while the device still maintains a low insertion loss (IL) of 12.5 dB. Through the cascaded compensation method, the modulation depth of the modulator at −2 V, −4 V, −6 V, and −8 V are 58 dB, 53 dB, 57 dB, and 59 dB, respectively. Meanwhile, the dynamic ER is 9.2 dB at a data rate of 40 Gbps, which is 4.5 dB higher than that of the original one.