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Optical nanofocusing by tapering coupled photonic-plasmonic waveguides
Xiaolong He1, Liu Yang, Tian Yang
1University of Michigan- Shanghai Jiao Tong University Joint Institute, National Key Laboratory of Nano/Micro Fabrication Technology, State Key Laboratory of Advanced Optical Communication Systems and Networks, Shanghai Jiao Tong University, Shanghai, China.
Optics Express
|July 13, 2011
Summary
We designed a compact optical device that concentrates light into a tiny, high-intensity spot using surface plasmons. This innovation achieves efficient light manipulation for potential nanoscale applications.
Area of Science:
- Photonics and Plasmonics
- Nanophotonics
- Optical Engineering
Background:
- Efficiently concentrating optical waves into sub-wavelength dimensions is crucial for advanced photonic applications.
- Surface plasmons offer a route to overcome the diffraction limit of light, enabling nanoscale optical manipulation.
- Existing methods for generating high-intensity plasmonic focal spots often involve complex structures and fabrication.
Purpose of the Study:
- To numerically design a compact, efficient structure for concentrating optical waves into a deep sub-wavelength surface plasmon focal spot.
- To achieve high photon-to-surface plasmon coupling efficiency and significant electric field enhancement.
- To develop a device with potentially simpler fabrication compared to previous approaches.
Main Methods:
- Numerical design and simulation of a compact optical structure integrating a silicon-on-insulator waveguide with a metallic strip taper.
- Development of a systematic design approach to optimize the coupling efficiency between optical waves and surface plasmons.
- Analysis of the focal spot characteristics, including size, intensity enhancement, and wavelength dependence (1.55 μm).
Main Results:
- Achieved an optimal photon-surface plasmon side coupling efficiency of up to 50% at 1.55 μm wavelength.
- Generated a focal spot with dimensions of approximately 20nm × 20nm × 7nm.
- Demonstrated an over 50-fold increase in electric field intensity within the focal region.
- The entire device has a compact length of 2.2 μm.
Conclusions:
- The numerically designed compact structure effectively concentrates optical waves into a high-intensity, deep sub-wavelength surface plasmon focal spot.
- The proposed device offers high coupling efficiency and significant field enhancement, suitable for nanoscale photonic applications.
- The design is expected to be simpler to fabricate than existing devices, paving the way for practical implementation.
