Silicon lithium niobate electro-optic waveguide modulator structures in the parallel-plate configuration

Area of Science:

• Photonics and Optoelectronics
• Materials Science
• Integrated Circuits

Background:

• Waveguide modulators are crucial components in optical communication systems.
• Traditional metal electrodes in modulators suffer from significant optical losses due to surface plasmons.
• Silicon-based electrodes present a potential alternative to mitigate these losses.

Purpose of the Study:

• To investigate waveguide modulators with parallel-plate electrodes using computer modeling.
• To compare optical losses and bandwidth limitations of metal versus silicon electrodes.
• To explore the fabrication and performance of devices integrating silicon and lithium niobate.

Main Methods:

• Computer modeling of waveguide modulators with different electrode materials (metal vs. silicon).
• Analysis of optical loss mechanisms, including surface plasmons and resistive losses.
• Fabrication of devices using silicon-on-sapphire substrates, lithium niobate films, and hydrogenated amorphous silicon electrodes.
• Characterization of electrode resistivity, optical absorption, and electro-optic coefficients.

Main Results:

• Metal electrodes exhibit high optical losses due to surface plasmons, while silicon electrodes show lower losses.
• Device bandwidth is constrained by electrode resistivity and proximity, with silicon doping impacting conductivity and absorption.
• Fabricated lithium niobate films possess approximately 50% of the bulk electro-optic coefficient.
• A trade-off exists between achievable bandwidth and optical loss in device optimization.

Conclusions:

• Silicon electrodes are a promising alternative to metal electrodes for reducing optical losses in waveguide modulators.
• Device performance is governed by a balance between electrical conductivity, optical absorption, and electrode geometry.
• The integration of silicon integrated circuits with waveguide modulators on a common substrate is feasible using these fabricated devices.