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Title: Hybrid metasurface for ultra-broadband terahertz modulation

We demonstrate an ultra-broadband free-space terahertz modulator based on a semiconductor-integrated metasurface. The modulator is made of a planar array of metal cut-wires on a silicon-on-sapphire substrate, where the silicon layer functions as photoconductive switches. Without external excitation, the cut-wire array exhibits a Lorentzian resonant response with a transmission passband spanning dc up to the fundamental dipole resonance above 2 THz. Under photoexcitation with 1.55 eV near-infrared light, the silicon regions in the cut-wire gaps become highly conductive, causing a transition of the resonant metasurface to a wire grating with a Drude response. In effect, the low-frequency passband below 2 THz evolves into a stopband for the incident terahertz waves. Experimental validations confirm a bandwidth of at least 100%, spanning 0.5 to 1.5 THz with -10 dB modulation depth. This modulation depth is far superior to -5 dB achievable from a plain silicon-on-sapphire substrate with effectively 25 times higher pumping energy. The proposed concept of ultra-broadband metasurface modulator can be readily extended to electrically controlled terahertz wave modulation.
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  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  2. Univ. of Adelaide (Australia)
Publication Date:
OSTI Identifier:
Report Number(s):
Journal ID: ISSN 0003-6951; APPLAB
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Applied Physics Letters
Additional Journal Information:
Journal Volume: 105; Journal Issue: 18; Journal ID: ISSN 0003-6951
American Institute of Physics (AIP)
Research Org:
Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
Sponsoring Org:
Country of Publication:
United States