Ultrahigh spatiotemporal resolved pump-probe signal near a gold nano-slit is detected by femtosecond-SNOM. By employing two-color pump-probe configuration and probing at the interband transition wavelength of the gold, signal contributed by surface plasmon polariton is avoided and spatiotemporal evolvement of excited electrons is successfully observed. From the contrast decaying of the periodical distribution of the pump-probe signal, ultrafast diffusion of excited electrons with a time scale of a few hundred femtoseconds is clearly identified. For comparison, such phenomenon cannot be observed by the one-color pump-probe configuration. (C) 2010 Optical Society of America
Ultrahigh spatiotemporal resolved pump-probe signal on a metal nanostructure is detected by femtosecond-SNOM. By using two-color pump-probe configuration, ultrafast hot electron transportation is clearly observed on a time scale of a few hundred femtoseconds. (C) 2010 Optical Society of America
An asymmetric single-nanoslit composed of a conventional nanoslit with a nanogroove next to it in a metallic film is proposed to generate unidirectional surface plasmon polaritons (SPPs) efficiently with back-side illumination. Numerical simulations show that due to the different interference processes of SPPs to opposite directions, efficient unidirectional SPP generation can be achieved. Experimentally, an extinction ratio of about 30:1 for SPPs to opposite directions and a generation efficiency of about 1.8 times that of the symmetrical case are demonstrated at wavelength of 830 nm with the lateral dimension of the asymmetric single-nanoslit of only 370 nm. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3472251]
Based on full 3D finite element method simulations, the transmission of a dielectric-loaded surface plasmon polariton waveguide (DLSPPW) based 1/4 circle is calculated for a 90 degrees bend model and a 270 degrees bend model, respectively. It is found that the 270 degrees bend model gives almost pure bending loss while the 90 degrees bend model contains additional coupling loss. The models are applied to deduce the loss and unloaded quality factor of DLSPPW based waveguide ring resonators (WRRs) and the results of the 270 degrees bend model agree well with direct simulating results of the WRRs. Thus the 270 degrees bend model gives a fast and simple way to calculate bending loss and it is helpful for WRR design because no wavelength scan is needed.