Abstract-Design and fabrication of frequency-responsive terahertz transmittance modulator based on vanadium dioxide spherical films

 

Jiran Liang, Ke Zhang, Tianyu Su, Shuangli Wang, Xuan Yu, 

https://ww.sciencedirect.com/science/article/abs/pii/S0030401821000845?dgcid=rss_sd_all

In this paper, a spherical film array structure based on vanadium dioxide (VO2) was designed and fabricated aimed to enhance the frequency response of transmittance in terahertz (THz) band of VO2 films. Vanadium dioxide and vanadium pentoxide composite spherical films were grown on the surface of two-dimensional single layer array of SiO2 sphere by magnetron sputtering and rapid thermal annealing method, and the frequency response of transmittance of spherical films was studied. The THz transmittance modulation depth (MD) of spherical films increased significantly in the 1.5–3 THz range as frequency increased, while MD of planar films only increased slightly throughout the frequency band. We attributed the frequency response of the MD of spherical films to the absorption by electric dipole resonance. The numerical simulations and electric field distributions illustrate that the regulating effect of resonance absorption would increase as the width of spherical gaps increase. When the width of the spherical gaps  was 

0.05μm, the absorptivity would increase by 120% from 1.5 to 3 THz, showing the possibility of further improving the THz MD of spherical films. This research would provide a good candidate material in the active modulation in terahertz band which broaden a path for dynamic terahertz radiation manipulation devices.

Abstract-Geometric constraints on phase coexistence in vanadium dioxide single crystals

Christina McGahan1, Sampath Gamage2,3, Jiran Liang1,4, Brendan Cross2,3, Robert E Marvel5,6, Richard F Haglund1,5 and Yohannes Abate2,3

Published 18 January 2017 • © 2017 IOP Publishing Ltd 

http://iopscience.iop.org/article/10.1088/1361-6528/aa5652

The appearance of stripe phases is a characteristic signature of strongly correlated quantum materials, and its origin in phase-changing materials has only recently been recognized as the result of the delicate balance between atomic and mesoscopic materials properties. A vanadium dioxide (VO2) single crystal is one such strongly correlated material with stripe phases. Infrared nano-imaging on low-aspect-ratio, single-crystal VO2 microbeams decorated with resonant plasmonic nanoantennas reveals a novel herringbone pattern of coexisting metallic and insulating domains intercepted and altered by ferroelastic domains, unlike previous reports on high-aspect-ratio VO2 crystals where the coexisting metal/insulator domains appear as alternating stripe phases perpendicular to the growth axis. The metallic domains nucleate below the crystal surface and grow towards the surface with increasing temperature as suggested by the near-field plasmonic response of the gold nanorod antennas.