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Terahertz emission from surface-immobilized gold nanospheres
Kotaro Kajikawa1, Yusuke Nagai, Yuichi Uchiho
1Department of Electronics and Applied Physics, Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, Nagatsuta, Yokohama 226-8502, Japan. kajikawa@ep.titech.ac.jp
Optics Letters
|October 3, 2012
Summary
Surface-immobilized gold nanospheres generate strong terahertz (THz) waves via optical rectification. This THz emission is significantly enhanced compared to traditional gold films, even off-resonance.
Area of Science:
- Plasmonics
- Nonlinear Optics
- Terahertz (THz) Science and Technology
Background:
- Optical rectification is a nonlinear optical process for generating electromagnetic waves.
- Terahertz (THz) wave generation is crucial for various spectroscopic and imaging applications.
- Surface plasmon resonance in metallic nanostructures can enhance light-matter interactions.
Purpose of the Study:
- To investigate terahertz (THz) wave emission from surface-immobilized gold nanospheres (SIGNs).
- To compare THz emission efficiency of SIGNs with traditional gold thin films.
- To explore the underlying nonlinear optical mechanisms responsible for THz generation.
Main Methods:
- Fabrication of surface-immobilized gold nanospheres on a gold film.
- Excitation of the nanostructure with off-resonant laser wavelengths.
- Measurement of emitted terahertz (THz) radiation using electro-optic sampling.
- Theoretical modeling to understand light electric field enhancement.
Main Results:
- Observed electromagnetic wave emission at terahertz (THz) wavelengths from SIGNs.
- Achieved THz emission approximately 4.8 times stronger than from a 10 nm gold film.
- Confirmed quadratic dependence of THz amplitude on excitation light intensity.
Conclusions:
- Surface-immobilized gold nanospheres are efficient sources for THz wave generation via optical rectification.
- The SIGN system enhances the light electric field, leading to improved THz emission.
- The observed THz generation is attributed to a second-order nonlinear optical process.
