Scalable and Reconfigurable Continuously Tunable Lithium Niobate Thin Film Delay Line Using Graphene Electrodes

Abstract

We propose a novel continuously tunable delay line in X-cut lithium niobate thin film driven by graphene electrodes, featuring low power consumption and low half-wave voltage-length product. The use of the graphene electrodes combined with the air slots makes the device quite low power consumption. Our designed device, which has a footprint of 8.9 mm × 1.9 mm, is capable of providing a continuously tunable delay range from 0 to 100 ps with minimum 3 dB bandwidth of >20 GHz. By optimizing the width of the waveguide core and the distance between the graphene and the waveguide core, we can obtain the low power consumption and low voltage - length product <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">π</sub> <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</i> = 1.12 V·cm at 1550 nm when <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">w</i> = 2 μm and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> = 0.3 μm. In addition, the graphene electrode has negligible light absorption with <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">w</i> = 2 μm and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> = 0.3 μm, the switching power is 151 mW without air slots, and the switching power is 95.36 mW with air slots etching depth of 5.3 μm formed on both sides of the waveguides. And further, the air slots formed on both sides and at the bottom of the waveguides make a low switching power of 2.85 mW.