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Exploiting the Metal-Insulator Transition of VO2 Thin Films for Terahertz Wave Modulation and Switching

Published online by Cambridge University Press:  11 June 2015

Md Nadim Ferdous Hoque
Affiliation:
Department of Electrical and Computer Engineering and Nano Tech Center, Texas Tech University, Lubbock, Texas 79409, USA
Gulten Karaoglan-Bebek
Affiliation:
Department of Physics and Nano Tech Center, Texas Tech University, Lubbock, Texas 79409, USA
Mark Holtz
Affiliation:
Department of Physics and MSEC, Texas State University, San Marcos, Texas 78666, USA
Ayrton A. Bernussi
Affiliation:
Department of Electrical and Computer Engineering and Nano Tech Center, Texas Tech University, Lubbock, Texas 79409, USA
Zhaoyang Fan
Affiliation:
Department of Electrical and Computer Engineering and Nano Tech Center, Texas Tech University, Lubbock, Texas 79409, USA
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Abstract

VO2 is one of the very few natural materials that can be used to modulate terahertz (THz) radiations. A 100-nm thick VO2, when in its metallic phase, has a charge density of more than ∼ 1015 cm-2 which will strongly reflect and absorb the THz radiation; while in its insulator state, the charge density is lowered by several orders of magnitude to be THz transparent. Therefore, exploiting the metal-insulator transition of VO2 is a potential approach to modulate or even switch THz radiation for THz optics. Here we report that VO2 epitaxial thin films on sapphire substrate exhibits 85% amplitude modulation depth in a broad bandwidth, while this value can be improved to 95% when VO2 film is coated on both sides of a substrate. We further demonstrate that with wafer bonding, 4-layered VO2 thin films exhibit a transmittance as low as -20 dB to -30 dB at their metallic state, enough for switching applications. We also report our proof-of-concept demonstration of THz spatial light modulator that exhibits amplitude modulation as large as 96%, -30 dB pixel-to-pixel crosstalk, and a broad THz bandwidth.

Type
Articles
Copyright
Copyright © Materials Research Society 2015 

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References

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