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.
- Research Organization:
- Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
- Sponsoring Organization:
- USDOE
- Grant/Contract Number:
- AC52-06NA25396
- OSTI ID:
- 1236572
- Alternate ID(s):
- OSTI ID: 1224275
- Report Number(s):
- LA-UR-14-27721; APPLAB
- Journal Information:
- Applied Physics Letters, Vol. 105, Issue 18; ISSN 0003-6951
- Publisher:
- American Institute of Physics (AIP)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
Web of Science
Similar Records
Investigation of broadband terahertz generation from metasurface
Terahertz Detection with Perfectly-Absorbing Photoconductive Metasurface