Abstract
This talk will cover a systematic study of highly enhanced optical field and its induced thermal transport in nanotips under laser irradiation. First of all, the effects on electric field distribution caused by curvature radius, tip aspect ratio, and polarization angle of the incident laser are studied. Our Poynting vectors study clearly shows when a laser interacts with a metal tip, it is bent around the tip and concentrated under the apex, where extremely high field enhancement appears. A shift of field peak position away from the tip-axis is observed. For the incident light, only its component along the tip axis direction has contribution to the electric field enhancement under the tip apex. The dynamic thermal behavior inside nanoscale tungsten tips due to absorption of incident laser is explored in combination with the optical field simulation. Second, the temperature rise of the nanotip is determined from the relationship between Raman shift versus temperature. Microscale resolution is achieved for temperature probing and microscale spatially resolved temperature response when the laser spot moves along the tip axis until to the cantilever. Sound agreement between the modeling and experimental result is observed, and discussions are provided about the reasons for their discrepancy. Finally, sub-10 nm static thermal response of the substrate beneath the nanotip under near-field laser focusing is discussed, in parallel with comparison with theoretical analysis of the local nanoscale ballistic heat conduction and non-linear optical absorption.
© 2012 Optical Society of America
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