Heterogeneous integrated phase modulator based on two-dimensional layered materials
Hao Chen, Zexing Zhao, ziming zhang, Guoqing Wang, Jiatong Li, Zhenyuan Shang, Mengyu Zhang, Kai Guo, Junbo Yang, Peiguang Yan
Abstract
Silicon nitride, with ultralow propagation loss and a wide transparency window, offers an exciting platform to explore integrated photonic devices for various emerging applications. It is appealing to combine the intrinsic optical properties of two-dimensional layered materials with high-quality optical waveguides and resonators to achieve functional devices in a single chip. Here we demonstrate a micro-ring resonator-based phase modulator integrated with few-layer <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m1"> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>MoS</mml:mi> </mml:mrow> <mml:mn>2</mml:mn> </mml:msub> </mml:mrow> </mml:math> . The ionic liquid is employed directly on the surface of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m2"> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>MoS</mml:mi> </mml:mrow> <mml:mn>2</mml:mn> </mml:msub> </mml:mrow> </mml:math> to form a capacitor configuration. The effective index of the composite <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m3"> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>MoS</mml:mi> </mml:mrow> <mml:mn>2</mml:mn> </mml:msub> <mml:mo>–</mml:mo> <mml:mi>SiN</mml:mi> </mml:mrow> </mml:math> waveguide can be modulated via adjusting bias voltages to achieve different charged doping induced electro-refractive responses in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m4"> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>MoS</mml:mi> </mml:mrow> <mml:mn>2</mml:mn> </mml:msub> </mml:mrow> </mml:math> film. The maximum effective index modulation of the composite <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m5"> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>MoS</mml:mi> </mml:mrow> <mml:mn>2</mml:mn> </mml:msub> <mml:mo>–</mml:mo> <mml:mi>SiN</mml:mi> </mml:mrow> </mml:math> waveguide can be achieved to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m6"> <mml:mrow> <mml:mn>0.45</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>3</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> . The phase tuning efficiency is measured to be 29.42 pm/V, corresponding to a <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m7"> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi mathvariant="italic">V</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="italic">π</mml:mi> </mml:mrow> </mml:msub> <mml:mi mathvariant="italic">L</mml:mi> </mml:mrow> </mml:math> of 0.69 V·cm. Since the micro-ring resonator is designed near the critical coupling regime, the coupling condition between the bus waveguide and micro-ring resonator can also be engineered from under-coupling to over-coupling regime during the charged doping process. That can be involved as a degree of freedom for the coupling tailoring. The ability to modulate the effective index with two-dimensional materials and the robust nature of the heterostructure integrated phase modulator could be useful for engineering reliable ultra-compact and low-power-consumption integrated photonic devices.