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Published on: September 27, 2011
Group delay and dispersion in adiabatic plasmonic nanofocusing
Vasily Kravtsov1, Joanna M Atkin, Markus B Raschke
1Department of Physics, Department of Chemistry, and JILA, University of Colorado, Boulder, Colorado 80309, USA.
Optics Letters
|April 19, 2013
Summary
Surface plasmon polariton propagation slows significantly on conical tips, reaching velocities below 0.2c. This finding supports plasmonics for broadband slow-light technologies.
Area of Science:
- * Physics, Optics, and Photonics
Background:
- * Surface plasmon polaritons (SPPs) are light-like waves confined to the interface between a dielectric and a metal.
- * Nanofocusing SPPs concentrates electromagnetic energy into subwavelength volumes, crucial for nanoscale optics.
- * Controlling SPP propagation speed is key for developing novel optical devices.
Purpose of the Study:
- * To experimentally measure the group velocity of broadband SPPs on a conical tip.
- * To investigate the influence of geometry on SPP propagation near the apex.
- * To assess the potential of SPPs for slow-light applications.
Main Methods:
- * Femtosecond time-domain interferometry was employed to precisely measure group delay.
- * Characterization of SPP propagation dynamics on a precisely fabricated conical tip.
- * Analysis of the relationship between taper geometry and group velocity.
Main Results:
- * A significant decrease in SPP group velocity was observed, with values below 0.2c at the apex.
- * Measured group delay was (9±3) fs, confirming substantial velocity reduction.
- * Second-order dispersion was found to be below 25 fs(2).
Conclusions:
- * Experimental results generally align with adiabatic plasmonic nanofocusing theory.
- * SPP velocity is highly sensitive to the apex's taper geometry.
- * Observed slow-light effects provide a foundation for plasmonic slow-light devices.
