Abstract

Transparent conductive oxides (TCOs) such as indium-tin oxide (ITO) have attracted increasing interests in integrated photonics and silicon photonics, owing to their large plasma dispersion and epsilon-near-zero (ENZ) effect. The nonlinear change of refractive index induced by free carrier modulation leads to a large electro-optic modulation with ultra-compact device footprint and unprecedented energy efficiency. However, high-speed modulation result is rare, mainly due to the lack of high-speed device design and fabrication quality. In this article, we characterize the fundamental electro-optic modulation structure consisting of Au/ITO/oxide/p-Si capacitor, showing that the property of ITO is greatly affected by the process condition. We also report an 8-μm-long hybrid plasmonic-silicon modulator driven by an ENZ ITO capacitor, achieving 100fJ/bit energy efficiency, 3.5 GHz modulation bandwidth, and 4.5 Gb/s data rate. The electro-absorption modulator covers a broad optical bandwidth from 1515 to 1580 nm wavelength. For future development of such modulators, we point out that by replacing ITO with higher mobility TCO materials, we can achieve 40 GHz modulation bandwidth and 0.4 fJ/bit energy efficiency using a 3-μm-long device.

Ultra-compact and broadband electro-absorption modulator using an epsilon-near-zero conductive oxide

Qian Gao, Erwen Li, and Alan X. Wang
Photon. Res. 6(4) 277-281 (2018)

Gigahertz speed operation of epsilon-near-zero silicon photonic modulators

Michael G. Wood, Salvatore Campione, S. Parameswaran, Ting S. Luk, Joel R. Wendt, Darwin K. Serkland, and Gordon A. Keeler
Optica 5(3) 233-236 (2018)

Electro-optical modulation of a silicon waveguide with an “epsilon-near-zero” material

Alok P. Vasudev, Ju-Hyung Kang, Junghyun Park, Xiaoge Liu, and Mark L. Brongersma
Opt. Express 21(22) 26387-26397 (2013)

Transparent conductive oxides for the epsilon-near-zero Tamm plasmon polaritons

Rashid G. Bikbaev, Stepan Ya. Vetrov, and Ivan V. Timofeev
J. Opt. Soc. Am. B 36(10) 2817-2823 (2019)

Extreme local field enhancement by hybrid epsilon-near-zero–plasmon mode in thin films of transparent conductive oxides

Innem V. A. K. Reddy, Josep M. Jornet, Alexander Baev, and Paras N. Prasad
Opt. Lett. 45(20) 5744-5747 (2020)