Electrically tunable subwavelength grating using transparent conductive oxide

Erwen Li; Qian Gao; Alan X. Wang

doi:10.1117/12.2292285

22 February 2018 Electrically tunable subwavelength grating using transparent conductive oxide

Erwen Li, Qian Gao, Alan X. Wang

Proceedings Volume 10536, Smart Photonic and Optoelectronic Integrated Circuits XX; 1053626 (2018) https://doi.org/10.1117/12.2292285
Event: SPIE OPTO, 2018, San Francisco, California, United States

Abstract

Transparent conductive oxides (TCOs) are getting increasing attention due to their unique epsilon-near-zero (ENZ) effect. The optical properties of TCOs can be dramatically changed from dielectric-like to metallic-like by controlling the carrier concentration in the telecommunication wavelengths, resulting in a near zero permittivity. The carrier concentration can be electrically manipulated when TCOs are built in a metal-oxide-semiconductor structure. With applied electrical bias, an accumulation layer forms at the oxide/TCO interface. When the accumulation layer meets ENZ condition, optical field is concentrated in the very thin accumulation layer, and thus the light-matter interaction is greatly enhanced. Such property makes TCOs wonderful materials for building active electro-optical devices. To data, several TCOs based devices configurations have been reported, such as metal-insulator-metal (MIM) waveguide based modulator, Si waveguide based plasmonic MOS modulator, PlasMOStor, and TCOs based tunable metasurfaces. Here, we design and demonstrate a TCOs based tunable subwavelength grating for surface normal modulation in the telecommunication wavelengths. The device combines the TCOs MOS structure with plasmonic grating filter. When applying voltage, the light-matter interaction in the active TCOs region is further enhanced by the surface-plasmon resonances coupled guided-mode resonances (GMRs), which enables high efficient modulation for both transmission and reflection mode with only 10nm thick TCOs layer. At peak wavelength (~1.55 μm), the simulated modulation depth achieves as high as 32% for transmission mode and 56% for reflection mode.

Citation Download Citation

Erwen Li, Qian Gao, and Alan X. Wang "Electrically tunable subwavelength grating using transparent conductive oxide", Proc. SPIE 10536, Smart Photonic and Optoelectronic Integrated Circuits XX, 1053626 (22 February 2018); https://doi.org/10.1117/12.2292285

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