Near-field optical apertured tip and modified structures for local field enhancement

Area of Science:

• Nanotechnology
• Optical Microscopy
• Materials Science

Background:

• Near-field scanning optical microscopy (NSOM) probes are crucial for nanoscale optical imaging.
• Conventional NSOM probes often suffer from low optical throughput, limiting their performance.
• Improving light transmission efficiency is key to advancing NSOM capabilities.

Purpose of the Study:

• To experimentally measure and simulate the spatial distribution of near-field light at the aperture of a novel Si micromachined NSOM probe.
• To evaluate the optical throughput of the fabricated NSOM probes.
• To investigate the fabrication of enhanced NSOM probes.

Main Methods:

• Fabrication of a miniature aperture on a SiO(2) tip using low-temperature oxidation and selective etching.
• Experimental measurement of optical transmission efficiency (throughput) and near-field light spatial distribution.
• Three-dimensional finite difference time domain (FDTD) simulations to model near-field light confinement.

Main Results:

• The fabricated 100-nm aperture probe demonstrated an optical throughput of approximately 10(-2), orders of magnitude higher than optical fibers.
• FDTD simulations confirmed good near-field light confinement with 1% throughput for a 100-nm aperture, matching experimental results.
• A 300-nm aperture probe showed a spatial distribution with a 250 nm FWHM and an estimated throughput of 2.4%.

Conclusions:

• The developed Si micromachined NSOM probe offers significantly higher optical throughput compared to conventional designs.
• Experimental and simulation results show good agreement, validating the probe's performance.
• Initial fabrication of high-throughput coaxial and surface plasmon enhanced NSOM probes shows promise for future advancements.