Analysis of Half-Wave Voltage in Microwave LiNbO₃ Mach-Zehnder Modulators

The work is devoted to measuring and calculation the half-wave voltage of LiNbO3 Mach-Zehnder modulators at direct current and from the load frequency. Half-wave voltage and bandwidth are the most important parameters of modulators that characterize their effectiveness. A sharp change in the half-wave voltage was recorded with a sweep time of more than one minute in the range of 10 V on the transfer function. The spread of the half-wave voltage could reach up to 30% of the initial value. This effect is related to operating point drift, and this method can be used to somewhat assess the stability of $\mathbf{LiNbO}_{3}$ Mach-Zehnder modulators. In addition, electro-optical parameters was measured from load modulation frequency in the range from 1 to 40 GHz. The results show a linear increase in the half-wave voltage from a frequency above 1 GHz. The obtained results are important for improving the stability and performance of LiNbO3 Mach-Zehnder modulators during their operation.