TY - GEN
T1 - Design of apertureless tips with very high plasmon field enhancement
AU - Čajko, F.
AU - Tsukerman, I.
AU - Kisliuk, A.
AU - Sokolov, A. P.
PY - 2006
Y1 - 2006
N2 - In contrast with aperture-limited Scanning Near-field Optical Microscopy, where the focusing of light is achieved only with very high attenuation, in aperture/ess near-field optics light is both focused and strongly amplified by the surface plasrnons of the probe. Although the general feasibility of this idea and the unprecedented in optics lateral resolution of ∼ 15-30 nm have already been demonstrated, the actual field enhancement has so far been well below theoretical expectations, and the useful optical signals have been weak. To bridge the gap between the "proof-of-concept" experiments and reliable optical microscopy with molecular-scale resolution, one needs to unify accurate simulation with effective measurements of the optical properties of the tips and with fabrication. We use dark-field microscopy with side collecting optics for measurements of the optical properties of the tip. The side view allows us to observe the radiation of the tip and hence to analyze its optical properties at the apex. In addition, the measured Raman signal provides an estimate of the electric field enhancement by the tip. Our simulation protocol consists of two parts: electrostatics and wave analysis. Electrostatic simulations give good qualitative predictions, are very fast and therefore conducive to multiparametric optimization. Rill wave analysis is needed to evaluate the dephasing effects and far-field signals. The Finite Element Method is used for all simulations. Various tip designs with the field enhancement ranging from ∼ 50 to over 250 (depending on various parameters), with the commensurate enhancement of the Raman signal by ∼ 454 (for gold coating) and ∼ 2704 (for silver coating), are presented and analyzed.
AB - In contrast with aperture-limited Scanning Near-field Optical Microscopy, where the focusing of light is achieved only with very high attenuation, in aperture/ess near-field optics light is both focused and strongly amplified by the surface plasrnons of the probe. Although the general feasibility of this idea and the unprecedented in optics lateral resolution of ∼ 15-30 nm have already been demonstrated, the actual field enhancement has so far been well below theoretical expectations, and the useful optical signals have been weak. To bridge the gap between the "proof-of-concept" experiments and reliable optical microscopy with molecular-scale resolution, one needs to unify accurate simulation with effective measurements of the optical properties of the tips and with fabrication. We use dark-field microscopy with side collecting optics for measurements of the optical properties of the tip. The side view allows us to observe the radiation of the tip and hence to analyze its optical properties at the apex. In addition, the measured Raman signal provides an estimate of the electric field enhancement by the tip. Our simulation protocol consists of two parts: electrostatics and wave analysis. Electrostatic simulations give good qualitative predictions, are very fast and therefore conducive to multiparametric optimization. Rill wave analysis is needed to evaluate the dephasing effects and far-field signals. The Finite Element Method is used for all simulations. Various tip designs with the field enhancement ranging from ∼ 50 to over 250 (depending on various parameters), with the commensurate enhancement of the Raman signal by ∼ 454 (for gold coating) and ∼ 2704 (for silver coating), are presented and analyzed.
KW - Apertureless near-field optical microscopy
KW - Dark field microscopy
KW - Finite element analysis
KW - Plasmon enhancement
KW - Side collecting optics
UR - http://www.scopus.com/inward/record.url?scp=33746742991&partnerID=8YFLogxK
U2 - 10.1117/12.663122
DO - 10.1117/12.663122
M3 - Conference contribution
AN - SCOPUS:33746742991
SN - 0819462519
SN - 9780819462510
T3 - Proceedings of SPIE - The International Society for Optical Engineering
BT - Nanophotonics
T2 - Nanophotonics
Y2 - 3 April 2006 through 5 April 2006
ER -