We compare two designs of metallodielectric stacks (MDS) based on Ag/GaP and Au/GaP, and calculate their superresolving
bandwidths. The super-resolving bandwidth of the Ag/GaP design is (520nm-560nm), while that of Au/GaP is
(630nm-660nm). We evaluate these two designs in their ability to resolve two 20nm wide apertures separated by a
center-to-center distance of 80nm. We also compare two numerical techniques used to study these systems, namely the
transfer matrix method (TMM) and the finite element method (FEM). The TMM is simpler than more numerically demanding FEM technique but FEM is more robust for determining super-resolution in most cases. Finally we discuss the practical limitations of our super-resolving imaging devices in resolving objects that are much smaller than the incident wavelength.
Experimental investigations reveal significant nonlinear responses from metallodielectric stacks (MDSs) with constituent
metal films of silver (Ag), gold (Au) or copper (Cu). In particular, the Cu dielectric MDS exhibited large non-linear
absorption. Nevertheless, there is a need to investigate these materials with more faithful numerical techniques in order
to account for the underlying physical processes observed in the experiments. We apply a Finite Element Method (FEM)
with radial symmetry to numerically solve for the Z-scan experiment of a MDS using the corresponding nonlinear
Maxwell equations. The amplitude and the phase of the electromagnetic field at the exit interface of the MDS are used
for transforming to the far-field regime.
Fluorescence has important applications in chemical and biological sensing and analysis due to the large selection of
fluorescent markers and their specificity in staining. In order to achieve high sensitivity, the strength and the collection
efficiency for the fluorescence signal is a critical issue that needs to be addressed. In this paper, we study the use of one
dimensional photonic band gap (1D PBG) structures to enhance the florescence excitation and collection. The 1D PBG
structure is designed to create an enhanced evanescent field for the excitation wavelength at the interface of last layer of
the PBG and the sample. Meanwhile, the 1D PBG also serves as an omnidirectional reflector for the florescence signal,
leading to higher collection efficiency. The combination of both effects provides a significant enhancement of
florescence signal. In order to verify the feasibility, GaP/SiO2 multilayer thin film stack is designed and fabricated. High
quality GaP/SiO2 multilayer thin film stack is fabricated using sputtering technique. The sputtered GaP thin film is
characterized using ellipsometer. GaP thin film with very high refractive index (n=3.45 at 633 nm) was obtained. The
performance of the multilayer stack as omnidirectional reflector is also reported.
The scale-invariant feature detecting methods always require a lot of computation yet sometimes still fail to meet the real-time demands in robot vision fields. To solve the problem, a quick method for detecting interest points is presented. To decrease the computation time, the detector selects as interest points those whose scale normalized Laplacian values are the local extrema in the nonholonomic pyramid scale space. The descriptor is built with several subregions, whose width is proportional to the scale factor, and the coordinates of the descriptor are rotated in relation to the interest point orientation just like the SIFT descriptor. The eigenvector is computed in the original color image and the mean values of the normalized color g and b in each subregion are chosen to be the factors of the eigenvector. Compared with the SIFT descriptor, this descriptor's dimension has been reduced evidently, which can simplify the point matching process. The performance of the method is analyzed in theory in this paper and the experimental results have certified its validity too.