| 研究実績の概要 |
After being successful in achieving plasmon nanofocusing with one wavelength, we extended our technique to obtain nanofocusing for white light.
1. Numerical simulation of plasmic: As we did for one wavelength, we continued the 3D-FDTD simulations to optimize coupler structure for a broad range of wavelengths. Our simulation results showed that a single slit with optimized size was the best coupler for white light.
2. Fabrication of plasmonic tip: We first oxidized the AFM Si cantilever tips, so that the material of the tip changed from Si to SiO2. The oxidized tips were coated on the one side with thin layer of silver. The challenge lied in obtaining very smooth surface of silver, which we completed successfully. Finally, using the focused ion beam (FIB) technique, we created a slit, which was optimized through the simulation, at a distance of 6 mm from the tip apex.
3. Measurement of nano-focusing and nano-imaging: After successful fabrication of the plasmonic tip for the nanofocusing of white light, we utilized these tips to confirm their features. We illuminated the slit coupler with white light and observed the creation of white nano-light at the apex of the tip. This nano-light was optically observed through various filters to confirm the presence of broad range of wavelengths in the light spot. Broadband was also confirmed by measuring the full spectrum. Finally, we applied these tips to perform high-resolution tip-enhanced Raman spectroscopy (TERS) on CNT samples and confirmed high-contrast, high-resolution nano-imaging.
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