Search results for "scanning"
showing 10 items of 1808 documents
Resolution enhancement in quantitative phase microscopy
2019
Quantitative phase microscopy (QPM), a technique combining phase imaging and microscopy, enables visualization of the 3D topography in reflective samples, as well as the inner structure or refractive index distribution of transparent and translucent samples. Similar to other imaging modalities, QPM is constrained by the conflict between numerical aperture (NA) and field of view (FOV): an imaging system with a low NA has to be employed to maintain a large FOV. This fact severely limits the resolution in QPM up to 0.82λ/NA, λ being the illumination wavelength. Consequently, finer structures of samples cannot be resolved by using modest NA objectives in QPM. Aimed to that, many approaches, suc…
Electrodynamics in complex systems
1996
This paper discusses recent theoretical efforts to develop a general and flexible method for the calculation of the field distributions around and inside complex optical systems involving both dielectric and metallic materials. Starting from the usual light-matter coupling Hamiltonian, we derive a self-consistent equation for the optical field in arbitrary optical systems composed of N different subdomains. We show that an appropriate solving procedure based on the real-space discretization of each subdomain raises the present approach to the rank of an accurate predictive numerical scheme. In order to illustrate its applicability, we use this formalism to address challenging problems relat…
Electron Crystallography – New Methods to Explore Structure and Properties of the Nano World
2012
Electron crystallography, as the branch of science that uses electron scattering, developed in the last century into a manifold and powerful approach to study the structure of matter. Major historical milestones of this development are discussed. Especially electron diffraction experienced recently a renaissance and grew into an established method of structure analysis. The techniques of data collection and processing available nowadays are described.
A/V ratio as predicted by full width at half maximum and by blood vessel tracking in presence of ocular aberrations
2011
Aberrations impact A/V ratio calculated from full width at half maximum. We investigated whether aberrations affect A/V ratio calculated by tracking the vessels. Aberrations changed the A/V ratio. We conclude that aberrations impact A/V ratio.
Analysis of photon-scanning tunneling microscope images of inhomogeneous samples: determination of the local refractive index of channel waveguides
1995
Channel waveguides are imaged by a photon-scanning tunneling microscope (PSTM). The polarization of the light and its orientation with respect to the guide axis are shown to be very important parameters in the analysis of the images of such samples. We simulated image formation for the plane of incidence parallel to the axis of the guide. Our theoretical results are qualitatively in agreement with our measurements. These results show the ability of the PSTM to give information about the local refractive-index variations of a sample.
Disorder and localization effects on the local spectroscopic and infrared optical properties ofGa1−xMnxAs
2015
We study numerically the influence of disorder and localization effects on the local spectroscopic characteristics and infrared optical properties of ${\text{Ga}}_{1\ensuremath{-}x}{\text{Mn}}_{x}\text{As}$. We treat the band structure and disorder effects at an equal level by using an exact diagonalization supercell simulation method. This method accurately describes the low-doping limit and gives a clear picture of the transition to higher dopings, which captures the localization effects inaccessible to other theoretical methods commonly used. Our simulations capture the rich in-gap localized states observed in scanning tunneling microscopy studies and reproduce the observed features of t…
Analysis of the imaging method for assessment of the smile of laser diode bars.
2009
We study imaging systems designed to assess the smile of laser diode bars (LDBs). The magnification matrix is derived from the required sampling period and the geometries of the LDBs and the charge-coupled device (CCD) array. These image-forming systems present in-plane pure translation invariance, but in the case of anamorphic ones, lack in-plane rotation invariance. It is shown that the smile parameters of the image of the LDB are linked with the smile parameters of the LDB by simple mathematical expressions. The spatial resolution of such optical systems is estimated at approximately 1 microm for a mean wavelength of lambda approximately 800 nm. Our results suggest that, with the current…
Asymptotic and Numerical Studies of Resonant Tunneling in 2D-Waveguides for Electrons of Small Energy
2021
Chapter 5 is devoted to asymptotic studies of electron resonant tunneling in a two-dimensional waveguide with two narrows. The narrow diameter plays the role of a small parameter. The asymptotics of basic characteristics of resonant tunneling are presented for electrons with energy between the first and the second thresholds. Moreover, the asymptotics results are compared with numerical ones obtained by approximate calculation of the scattering matrix.
Flexible drift-compensation system for precise 3D force mapping in severe drift environments
2011
The acquisition of dense 3D data sets is of great importance, but also a challenge for scanning probe microscopy (SPM). Thermal drift often induces severe distortions in the data, which usually constrains the acquisition of dense data sets to experiments under ultra-high vacuum and low-temperature conditions. Atom tracking is an elegant approach to compensate for thermal drift and to position the microscope tip with highest precision. Here, we present a flexible drift compensation system which can easily be connected to existing SPM hardware. Furthermore, we describe a 3D data acquisition and position correction protocol, which is capable of handling large and non-linear drift as typically …
Detection of the optical magnetic field by circular symmetry plasmons
2000
We report on the influence of coating a sharpened optical fiber tip with Au when observing nanofabricated dielectric structures with a Photon Scanning Tunneling Microscope (PSTM) in constant-height mode. For well-defined incident wavelengths and coating thicknesses, we found that such tips detect the distribution of the magnetic field associated with the optical wave in the near-field zone. A simple tip model indicates that this phenomenon is related to the excitation of circular symmetry plasmons in Au coated tips.