Authors:	R. A. Yadav, V. B. Palekar, G. Morthier, R. Kumar
Title:	Elecro-thermally driven vanadium dioxide based guided wave THz modulator
Format:	International Journal
Publication date:	6/2025
Journal/Conference/Book:	Advanced Theory and Simulations
Editor/Publisher:	Wiley,
Volume(Issue):	p.e01200
DOI:	10.1002/adts.202501200
Citations:	Look up on Google Scholar
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Abstract

To meet the growing demand for integrated, broadband, on-chip, external THz modulation, we propose a CMOS-compatible THz modulator operating in the 0.5 to 0.6 THz frequency range. To the best of author’s knowledge, this is the first report of a volatile phase change material (PCM) vanadium dioxide (VO2) based, electro-thermally driven on-chip THz modulator designed using the SOI dielectric waveguide platform. The intensity of the guided THz wave is modulated using the electro-thermally induced structural phase transformation property of VO2, integrated on top of the silicon-on-insulator (SOI) dielectric waveguide. For an active length and thickness of 1000 μm and 150 nm of the VO2, respectively, the modulator achieves a modulation depth of more than 90% with an insertion loss of less than 1 dB. Two micro-fins heater configurations, one enabling direct heating and the other being graphene assisted,
are used for the electro-thermally driven phase transformation of VO2. The response time (sum of the rise and fall time) of the modulator for the direct
and graphene assisted micro-fins heaters are 2.45 ms and 0.79 ms, respectively, which is the highest modulation speed achieved to date using the electro-thermal excitation of VO2 for its THz modulation application. Additionally, a taper coupler is designed and investigated, which facilitates the coupling of the THz waves between hollow metallic rectangular waveguides and the SOI dielectric waveguide. It exhibits an average coupling loss of 0.19 dB per coupling section and an average propagation loss of 0.24 dB/cm in the 0.5 to 0.6 THz frequency
range.