Design Optimization of $Z$-Cut Lithium Niobate Electrooptic Modulator With Profiled Metal Electrodes and Waveguides

Abstract

Analysis and optimization of an ultra-high-speed Z-cut lithium niobate (LN) electrooptic modulator, operating at a high-frequency region, by using a full-wave finite-element numerical technique, has been demonstrated. Investigation of the effects of adjusting the buffer layer thickness, the electrode height, the electrode trapezoidal profile, and the waveguide trapezoidal profile on the microwave effective index N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> , the characteristic impedance Z <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> , the microwave losses alpha <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> , and the half-wave voltage-length product V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pi</sub> L has been reported. Optimization of these parameters yield to a novel design of the LN modulator, with a low V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pi</sub> L and a high bandwidth, operating at a frequency range between 1 and 100 GHz. The frequency-dependent dispersion of the key device parameters, with the aim of determining the device suitability for high-speed operation, has been demonstrated.