Thermal relaxation trimming for enhancement of extinction ratio in electro-optic polymer Mach-Zehnder modulators

We propose and demonstrate a trimming method to enhance extinction ratio in an electro-optic (EO) polymer modulator with a Mach-Zehnder interferometer structure. In order to adjust the power splitting ratio at Y-branches, which is a main factor determining the extinction ratio, our method is exploited by using a change of the refractive index of the poled EO polymer due to thermal relaxation. The trimming is controlled by heating the Y-branch area via a heater. By using the thermal relaxation trimming, the extinction ratio in the adjusted EO modulator is enhanced by more than $7\mathrm{dB}$ without excess loss.