Second harmonic generation by the silicon Mach–Zehnder modulator with symmetric arm

The silicon Mach–Zehnder modulator is a significant type of optical modulator, which is widely utilized in optical communication and microwave photonics. The performance of the second harmonic microwave generation by a silicon Mach–Zehnder modulator is simulated and analyzed. The power and the purity of the second harmonic microwave mainly depend on two significant parameters: 1) the electrical nonlinearity of the diodes on arms of the modulator, 2) the bias voltage on the diode. Simulations show following results:1) when the built-in voltage Vb decreases from 8V to 3.5V, the incremental amounts of second harmonics and the fourth harmonics are 7.9dB and 15.6dB under the condition that the RF power is 15dBm and the bias voltage is 0V; 2) when the bias voltage increases from -0.5V to 4V, the ratio between second harmonics and the fourth harmonics varies from 20.0dB to 11.3dB under the condition that the RF power is 15dBm and the built-in voltage Vb is 3.5V. 3) when the RF power increases from 5dBm to 20dBm, the ratio between second harmonics and the fourth harmonics varies from 27.6dB to 11.6dB under the condition that is the bias voltage is 2V and the built-in voltage Vb is 3.5V. To conclude, the powers of second harmonics will increase with the reduction of the ratios between the second harmonics and the fourth harmonics.