Ultra-violet (UV) fluorescence lifetime modification by aluminum (Al) and magnesium (Mg) nanoapertures are reported in this manuscript. Nanoapertures with diameter ranging from 30nm to 90nm are fabricated using focused ion beam (FIB). Largest lifetime reduction are observed for apertures with smallest diameters and undercuts into glass substrate. For Al nanoapertures, largest lifetime reduction is ∼5.30×, larger than perviously reported ∼3.50×.1 For Mg nanoapertures, largest lifetime reduction is ∼6.90×, which is the largest lifetime reduction of UV fluorescence dye reported so far in literature. The dependence of count rate per molecule (CRM) on aperture size and undercut is also investigated, revealing that CRM increases with increasing undercut, however, the CRM is small (less than 2) for the entire range of aperture size and undercut we investigated. FDTD simulation were conducted and in order to favorably compare experimental results with simulated results, it is critical to take into account the exact shape and material properties of the nano aperture. Simulation results revealed the fundamental difference between Al and Mg nano aperture under 266nm illumination-Mg nano aperture presents a waveguide mode in which the maximum field enhancement and Purcell factor is within the nano aperture instead of on the surface which is the case for Al nano aperture.
KEYWORDS: Near field scanning optical microscopy, Near field, Microfluidics, Super resolution, Diffraction, Antimony, Spatial resolution, Near field optics, Optical microscopes, Scattering
A new proposal for biological or microfluidic detection based on super-resolution near-field structure (Super-RENS) proposed by Tominaga is described. The mechanism of the near-field structure we proposed to image microfluid is very similar to near-field scanning optical microscope (NSOM). In this paper, we describe our simulation model and results of the electric field distribution in the near field zone and readout signals from the near-field structure to image microfluid. Calculations have demonstrated that the near-field structure can be applied in biomedicine to detect tracing element or image microfluid etc with a high spatial resolution beyond the diffraction limit.
The SPPs propagation on curved metal-dielectric interface is simulated by FDTD(finite-difference time-domain) method. The propagation loss, the transmittance and the reflection coefficients of SPPs on curved metal-dielectric interface with different radius of curvature is presented. The results shows the radiation loss is the key factor for the SPPs propagation when the propagation area is the same order as the wavelength, and the reflection coefficient is so small that it is ignorable. The critical situation when the radius is zero is also analyzed and the reflection coefficient is much larger than the former situation; for the transmittance, different electronic field components play different roles.
The general role of the surface plasmons in the transmission of
the metallic grating with narrow slits has been numerical
described using the finite difference time domain method.
Different parameters of grating have been used in the numerical
simulation. It is concluded that whether the transmission peak of
the SP resonance emerges or not does not depend on the SP
travelling on the grating surface. The grating depth and the width
of slit really give a dominant influence on the energy
transmission for the SP resonance.
The optical reflector based on two-dimensional photonic crystal constructed by a square lattice of dielectric rods has already been reported in recent years, But the enormous difficulties to fabricate this structure are well-known, because the height of the rods must be finite in a real system so in this case no guided modes appears when air waveguides are created. On the contrary, there is not this inherent limitation for the photonic crystal waveguide made of air holes. In this paper, I will demonstrate an optical reflector based on photonic crystal,which constructed by air holes introduced into high index material. We design a monomode waveguide with even symmetry and discuss the characteristic of the reflector obtained by inserting several defects into the monomode waveguide in FDTD method.This kind of reflectors still have guided mode even if it possess finite thickness. This will make optical reflector based on two-dimensional photonic crystal nearer to practical application.
The interference of the surface plasmons polaritons (SPPs),
localized SPPs, has been numerical analyzed by 2D finite
difference time domain (FDTD) method. The near-field distributions
of the localized SPPs have been presented. It is found that the
quality of the output is not always good with strong interaction
of the SPPs in super-RENS. It is also found that the near-field
distribution and the output are almost changeless when the regions
of the dark stripes have been adjusted.
KEYWORDS: Near field optics, Near field, Silver, Finite-difference time-domain method, Nonlinear optics, Super resolution, Particles, Surface plasmons, Optical storage, Near field scanning optical microscopy
In this paper, modified finite differential time domain (FDTD) method is used to investigate super resolution near-field structure (Super-RENS). The random distributed Ag particles, which is responsible for the localization and the enhancement of the surface plasmon within the Super-RENS, is included in this simulation. The near-field optical distribution when recording mark is just beneath the nonlinear aperture is achieved. And the transmitted readout signal is also simulated.
The very small aperture laser (VSAL) is an important light source used in the near-field optical storage system. It is necessary for studying the near-field property of VSAL's output light. The optical characters and the intensity distribution in the near-field of the output region of the VSAL have been numerical simulated using two dimension nonlinear FDTD (2D-NL-FDTD) method and the Fox-Li method. Through analyzing the results from the viewpoint of the Optics, the possible application in the near-field optical recording have been discussed, and some curves indicating the near-field optical characters of the output light have been presented.
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