Folded thin-film lithium niobate modulator based on a poled Mach–Zehnder interferometer structure
Jinyao Hu, Chijun Li, Changjian Guo, Chao Lü, Alan Pak Tao Lau, Pengxin Chen, Liu Liu
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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mi>x</mml:mi> </mml:math> -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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:msub> <mml:mi>V</mml:mi> <mml:mi>π</mml:mi> </mml:msub> </mml:mrow> <mml:mi>L</mml:mi> </mml:math> product of a fabricated and completely poled folded modulator is about <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mn>2</mml:mn> </mml:mrow> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mn>.74</mml:mn> <mml:mspace width="thinmathspace"/> <mml:mspace width="thinmathspace"/> <mml:mi mathvariant="normal">V</mml:mi> </mml:mrow> <mml:mo>⋅</mml:mo> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi mathvariant="normal">c</mml:mi> <mml:mi mathvariant="normal">m</mml:mi> </mml:mrow> </mml:math> , 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.