Microwave Characteristics and Bandwidth of BaTiO 3 Crystal Film Waveguide Electrooptic Modulator to Match the Light‐Wave Standard (Invited)

In this article, the electrooptic (EO) intensity modulators using waveguide Mach–Zehnder interferometer and three‐electrode architecture are designed/fabricated on a c‐axis oriented barium titanate (BaTiO 3 ) crystal film. First, based on the light‐microwave coupled traveling, a microwave bandwidth standard of −6.4 dB to matching the −3 dB light‐wave bandwidth standard is derived. Then, the coherent correlation between bandwidth and bit‐energy of microwave is modeled. As a result, the broad simulations are put forward to the correlative microwave bandwidth and bit‐energy of EO modulator, and then three impactful points are found as that (i) the microwave matrix parameter S 21 attenuates faster with electrode width, implying the decrease of microwave bandwidth; (ii) the microwave index decreases with frequency, reducing the microwave‐lightwave mismatching; and (iii) the bit‐energy decreases with microwave bandwidth. As a result, the microwave bandwidth of over 60 GHz, are predicted by HFSS simulations, followed by a matched light‐wave bandwidth of over 55 GHz. Consequently, the experimental results of fabricated devices are in accord with the predictions with the simulations. Thus, the findings reached in this work are very conducive to budgeting the bandwidth for applications of BaTiO 3 crystal film waveguide EO modulator.