A new method for high-resolution quantitative measurement of the dielectric function by using scattering scanning near-field optical microscopy (s-SNOM) is presented. The method is based on a calibration procedure that uses the s-SNOM oscillating dipole model of the probe-sample interaction and quantitative s-SNOM measurements. The nanoscale capabilities of the method have the potential to enable novel applications in various fields such as nano-electronics, nano-photonics, biology or medicine.
The dependence of the near-field signal on the dielectric function of a specific material proposes scattering-type near-field optical microscopy (s-SNOM) as a viable tool for material characterization studies. Our experiment shows that specific material identification by s-SNOM is not a straightforward task as parameters involved in the detection scheme can also influence material contrast measurements. More precisely, we demonstrate that s-SNOM contrast in a pseudo-heterodyne detection configuration depends on the oscillation amplitude of the reference mirror and that for reliable measurements of the contrast between different materials this aspect needs to be taken into consideration.
In this paper we present some investigations on the near field based on a novel approach for scattering technique. Our new scanning near field optical microscope is introduced for resolving optical properties of surfaces with lateral resolution reaching 10 nm and better. The different works modes of the system are presented.
Confocal Scanning Laser Microscopy (CSLM) allows the acquisition of image stacks, representing optical sections on the volume of the specimen. An image corresponding to an optical section will in some cases contain defocused, low contrast or saturated regions for the areas of the sample which are not in focal plane. In the case of the Photonic Quantum Ring (PQR) laser structures, it is important to have images consisting of regions of uniform quality in order to observe morphological details that are linked to the photocurrent confinement. In this purpose we have developed an image fusion method, which based on a stack of CSLM images will output a fused image consisting of square regions from different images in the stack. In this paper we present the image fusion algorithm that we have used and the results that we have obtained on PQR laser structures. Keywords: image fusion, image enhancement, confocal scanning laser microscopy, photonic quantum ring laser structures.
INTRODUCTIONImage fusion represents a process in which relevant information from two or more images is combined together into a single image. The aim of image fusion is to integrate complementary and redundant information from a set of images in order to create a composite image that will contain a better description of the scene than any of the individual source images [1]. Applications of image fusion have been implemented with great success in many different fields such as remote sensing, biomedical imaging [2], computer vision and defense systems [5]. Excellent results have also been achieved in the case of three-dimensional microscopy, where certain limitations imposed by the low axial resolution have been overcome by fusing images acquired at different placements of the sample [4]. A fusion algorithm should ideally preserve all relevant information from the fused images, suppress irrelevant parts of the image and noise and minimize any artifacts or inconsistencies in the fused image [3].Image fusion can be performed in both frequency and spatial domains. Our approach, which deals with the fusion of CSLM images, was developed on a region level basis. Each image in the stack is divided in the same number of square regions. A quality assessment for the same region in all the images in the stack is performed, and the region of the best quality is chosen to appear in the fused image. In the end we obtain a fused image of uniform quality, with morphological details of the structure being more visible than in any other image that contributed to the fusion.
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