Exploiting the Metal-Insulator Transition of VO2 Thin Films for Terahertz Wave Modulation and Switching. Issue 1805 (11th June 2015)

• Record Type: Journal Article
• Authors: Hoque, Md Nadim Ferdous; Karaoglan-Bebek, Gulten; Holtz, Mark; Bernussi, Ayrton A.; Fan, Zhaoyang
• Editors: Augustynski, J.; Grosse, F.; Kumar, D.; Sanchez, F.; Santato, C.; Sun, X.W.; Vomiero, A.; Yamamoto, T.
• Is Part Of: MRS proceedings. Issue 1805(2015)
• Publication Date: 2015-06-11
• Subjects: crystal growth, -- metal-insulator transition, -- optical properties; Electrical engineering -- Congresses; Physics -- Congresses; Materials -- Research -- Congresses; Materials science -- Congresses; 620.11
• DOI: 10.1557/opl.2015.594
• Languages: English
• ISSNs: 0272-9172

Abstract

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 ∼ 10 15 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.