Surface plasmon field enhancement: excitation by a short pulse or narrow beam of light

With the advance of laser technology, there are many applications exciting surface plasmons with very short pulses of light. We perform a quantitative study of field amplification of surface plasmons excited by short light pulses. The dependence of the maximum intensity of the electromagnetic fields at the metal-dielectric interface is obtained as a function of the pulse duration. A Gaussian light pulse is used as the excitation source and the propagation of this pulse is computed on an attenuated total reflection system for the Kretschmann geometry. The field enhancement produced by the pulse is about 80% of the steady-state case when the width of the pulse is half the decay time of the surface plasmon, and it gets close to 95% when the width is equal to the time decay. We obtain an approximate expression for the field amplification as a function of the pulse width that is close to the exact calculation. Additionally, an approximate expression is obtained for the enhancement of the fields when surface plasmons are excited with a narrow spatial width beam. (C) 2018 Optical Society of America.