Folded thin-film lithium niobate modulator based on a poled Mach–Zehnder interferometer structure

The thin-film lithium niobate structure has been used recently to construct compact and high-performance electro-optical modulators. Due to the moderate electro-optical coefficient of the lithium niobate material, the device length of such a modulator is still long, a few centimeters usually. Here, a folded Mach–Zehnder interferometer based modulator on x -cut thin-film lithium niobate is demonstrated. An effective poling procedure is developed to activate the device. The proposed modulator structure can shorten the device length without affecting its performance. The measured V π L product of a fabricated and completely poled folded modulator is about 2 .74 V ⋅ c m , and the 3 dB electro-optical bandwidth is about 55 GHz. They are close to those of a conventional Mach–Zehnder modulator with a straight modulation section.