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arXiv · 2305.10639

Indium-Tin-Oxide for High-performance Electro-optic Modulation

Zhizhen Ma·Zhuoran Li·Behrouz Movahhed Nouri·Ke Liu·Chenran Ye·Hamed Dalir·Volker J. Sorger
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Abstract

Advances in opto-electronics are often led by discovery and development of materials featuring unique properties. Recently the material class of transparent conductive oxides (TCO) has attracted attention for active photonic devices on-chip. In particular Indium Tin Oxide (ITO) is found to have refractive index changes on the order of unity. This property makes it possible to achieve electro-optic modulation of sub-wavelength device scales, when thin ITO films are interfaced with optical light confinement techniques such as found in plasmonics; optical modes are compressed to nanometer scale to create strong light-matter-interactions. Here we review efforts towards utilizing this novel material for high-performance and ultra-compact modulation. While high performance metrics are achieved experimentally, there are open questions pertaining the permittivity modulation mechanism of ITO. Furthermore, we show that a footprint-saving waveguide inline cavity can enhance obtainable extinction-ratio to insertion-loss ratios by about one order of magnitude over non-cavity based version. Moreover, we offer a speed analysis that shows that the device is resistance limited, but not capacitance or drift-carrier limited. Interestingly, two bias options exist for ITO and we find that a side-connection enables devices that should in principle enable several hundred of GHz fast devices, using our routinely achievable ITO film resistivities. Finally, we offer a brief discuss about footprint savings of compact ITO modulators showing a 3-orders of magnitude smaller footprint over Silicon photonic MZI-based modulators.

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Zhizhen Ma, Zhuoran Li, Behrouz Movahhed Nouri, Ke Liu, Chenran Ye, Hamed Dalir, Volker J. Sorger. 2023-05-18. Indium-Tin-Oxide for High-performance Electro-optic Modulation. https://arxiv.org/abs/2305.10639

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