Green light stimulates terahertz emission from mesocrystal microspheres.
The discovery of efficient sources of terahertz radiation has been exploited in imaging applications, and developing a nanoscale terahertz source could lead to additional applications. High-frequency mechanical vibrations of charged nanostructures can lead to radiative emission, and vibrations at frequencies of hundreds of kilohertz have been observed from a ZnO nanobelt under the influence of an alternating electric field. Here, we observe mechanical resonance and radiative emission at ∼ 0.36 THz from core-shell ZnO mesocrystal microspheres excited by a continuous green-wavelength laser. We find that ∼ 0.016% of the incident power is converted into terahertz radiation, which corresponds to a quantum efficiency of ∼ 33%, making the ZnO microspheres competitive with existing terahertz-emitting materials. The mechanical resonance and radiation stem from the coherent photo-induced vibration of the hexagonal ZnO nanoplates that make up the microsphere shells. The ZnO microspheres are formed by means of a nonclassical, self-organized crystallization process, and represent a straightforward route to terahertz radiation at the nanoscale.
National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China.
X L
XL
Wu
S J
SJ
Xiong
Z
Z
Liu
J
J
Chen
J C
JC
Shen
T H
TH
Li
P H
PH
Wu
Paul K
PK
Chu
D003460:Crystallization / Q000379:methods; D007834:Lasers; D049329:Nanostructures / Q000737:chemistry*; D036103:Nanotechnology / Q000379:methods; D013059:Spectrum Analysis, Raman; D055053:Terahertz Radiation; D015034:Zinc Oxide / Q000737:chemistry
D015034:Zinc Oxide
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