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

Abstract

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 <i>x</i>-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 <i>V</i>_π<i>L</i> product of a fabricated and completely poled folded modulator is about 2.74<i>V</i>⋅<i>c</i><i>m</i>, 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.