The KTa_1-xNb_xO₃ (KTN) electro-optic modulator (EOM) is extensively applied to laser three-dimensional imaging and other fields, and optimizing its modulation contrast is essential for improving its modulation performance. It is generally considered that the modulator achieves optimal modulation contrast when its transmittance is 50%; however, the dielectric constant does not change with the electric field. Instead, the dielectric constant of a KTN crystal has a dynamic response under an electric field, which causes deviations in optimization. This study investigates the dynamic response of the dielectric constant to an electric field at low and high frequencies, and the maximizing modulation contrast method, which is based on the transmittance derivative function, is proposed. In the verification experiment, the proposed optimization method is used to achieve a maximum modulation contrast of 0.106 when the AC electric field is 320 V/m at a frequency of 1 kHz. The bias electric field is 95.4 kV/m, which is 3.5 times that of the 50% transmittance point. Additionally, when the AC electric field is 320 V/m at 500 kHz and the bias electric field is 87.8 kV/m, a maximum modulation contrast of 0.05 is achieved, which is double that of the 50% transmittance point.

KTa _1-x Nb _x O ₃（KTN）电光调制器（EOM）广泛应用于激光三维成像等领域，优化其调制对比度对于提高其调制性能至关重要。一般认为调制器在其透光率为50%时达到最佳调制对比度；然而，介电常数不随电场变化。相反，KTN 晶体的介电​​常数在电场下具有动态响应，这会导致优化偏差。本研究研究了介电常数对低频和高频电场的动态响应，并提出了基于透射率导数函数的最大化调制对比度方法。在验证实验中，当交流电场为 320 V/m 且频率为 1 kHz 时，所提出的优化方法用于实现 0.106 的最大调制对比度。偏置电场为95.4 kV/m，是50%透光点的3.5倍。此外，当交流电场为 320 V/m，频率为 500 kHz 且偏置电场为 87.8 kV/m 时，最大调制对比度为 0.05，是 50% 透射率点的两倍。