Ronald E. Burge

X-ray holography for VLSI using synthetic bilevel holograms

The gains are pointed out of the potential replacement of the usual patterned transmission x-ray mask, in consideration of high-resolution proximity lithography for VLSI, by a diffraction element, or bilevel in-line hologram, to be projected under near-field conditions using synchrotron radiation. The hologram can be configured to correct for diffraction blurring due to projection, and be designed for pre-determined gaps between mask and wafer. The adjustment of experimental parameters can account for the waveguide effects that arise from mask elements with small features which are several hundred x-ray wavelengths thick.It is shown that the hologram, for projection printing at the 50nm feature size, at mask to wafer gaps of 10micrometers or greater, can be fabricated in a similar fashion to a high-resolution mask. The calculation of the hologram is computationally intensive, but a database of calculated features is envisaged.

The effect of soft X‐radiation on myofibrils

Myofibrils, the contractile organelles from striated muscles, have been examined in the X‐ray microscope to determine the effect of radiation on their function and structure. Using X‐rays of energy 350–385 eV in the water window we find that after an exposure to 7·5 × 105 photons/μm2 (calculated to give an absorbed dose of 20000 Gy) the myofibrils will no longer contract. The use of the free radical scavenging agent, DMSO, gives some protection to the fibrils. It has also been found that after this much irradiation the fibrils lose up to 20% of their mass. Further substantial mass loss occurs on subsequent irradiation. After 25 times the loss‐of‐function exposure only 30% of the mass remains. Analysis of a series of images of the same myofibril covering this range of exposures shows that the mass is preferentially lost in some areas of the structure and consequently significant structural changes occur.

Region of validity of perturbation theory for dielectrics and finite conductors

Abstract We present a study of region of validity of first-order perturbation theory applied to rough surface scattering. The scattering problem is solved numerically for the case of periodic surface or gratings varying in one dimension. Scattering of electromagnetic waves from an ensemble of gratings of sufficiently long period will give a good approximation to the case of an infinite rough surface. We use this to test the validity of the first-order perturbation theory. Use of an infinite periodic surface allows us to give results for a range of angle of incidence covering those representing a low grazing angle, near 90° from the mean surface normal. We consider the case for perfect dielectrics and finite conductors. The real and imaginary parts of the refractive index used were limited to less than three due to the numerical instability of the numerical calculation method involved. We find that for perfect dielectrics the first-order small perturbation theory remains for TE polarization valid for all i...

Three-dimensional stereoscopic display using ray traced computer generated holograms

Abstract This paper presents a method of displaying a computer graphics rendered scence in three dimensions using the methods of computer generated holography. The display hologram is of the autostereoscopic type, comprising a series of perspective views of the scene concerned. The approach developed in this paper uses a ray tracing graphic rendering method to produce realistic shaded scenes. The scenes are encoded holographically and written at a directly usable size on a high resolution optical plotter.

Dependence of Speckle Statistics on Backscatter Cross-Section Fluctuations in Synthetic Aperture Radar Images of Rough Surfaces

A theory is described to relate the statistical properties of the fields backscattered from rough surfaces to those of speckle in synthetic hetic aperture rdar (SAR) images. The expressions are derived for the autocorrelation and cross-correlation functions of speckle intensity in both single-look and multilook images of stationary random rough surfaces in terms of the SAR system parameters and the autocorrelation function of backscatter radar cross-section fluctuations. It is shown that if the correlation scale of cross-section fluctuations is comparable with or greater than the SAR resolution, the correlation functions of speckle intensity depend on those of the cross-section fluctuations. This property, therefore, may be applied to image classification. Comparison on of the theory with computer simulation shows good agreement.

Scattering of scalar waves by two-dimensional gratings of arbitrary shape: application to rough surfaces at near-grazing incidence

We present the numerical study of scattering of scalar waves from impenetrable two-dimensional periodic surfaces of arbitrary shape. Nearly all numerical simulations of scattering of waves from rough surfaces in the past have been limited to one-dimensional surfaces and moderate angles of incidence. By making the surface infinite and bi-periodic, it becomes possible to simulate numerically scattering from two-dimensional surfaces, even down to grazing angle. Only impenetrable surfaces are considered. Some calculations are presented, and are used to compare with the small perturbation, or Rayleigh–Rice theory. It is found that for near grazing incidence, Neumann boundary condition, the small perturbation theory gives inaccurate values, especially near the backscatter direction.

Two optimisation approaches to COHOE design

Abstract Two methods of constraint optimisation are applied to the generation of Computer Originated Holographic Optical Elements (COHOEs). Their purpose is to determine the optimal holographic phase function to transform an arbitrary incident wavefront into an arbitrary diffracted wavefront. The merits of the two methods are discussed and experimental results are presented, including a 1 to 1024 ‘fanout’ COHOE.

Polarization dependence of the electromagnetic field distribution across wavelength-sized relief grating surfaces

The complex values of the surface electromagnetic fields of relief gratings for both TE and TM polarization are rigorously evaluated with use of the boundary-matching technique. The amplitude and phase of the surface field can be significantly modified by the edges and walls. The degree of modulation is strongly dependent on various factors, including the incident polarization. As the incident angle varies, the behavior of the surface-field amplitude is considered to be connected to the Brewster-angle effect. The complex refractive index of the grating material also influences the shape of the surface field but not in a proportional way. The oscillating surface fields with depth for both TE and TM polarization are explained as being due to secondary backward diffraction. In particular, as the edge and wall effects influence the TE and TM components differently, the oscillation peaks occur at different positions when TE and TM curves are compared.

SAR imaging of volume scatterers

The first renormalization scattering method is used to obtain an expression for the synthetic-aperture radar (SAR) complex image amplitude of a volume scatterer with an undulating boundary surface. This expression is then used to derive further expressions for correlations of such an image when the boundary is either deterministic or random. >

Elemental Mapping of Biological Tissue by X-Ray Absorption Difference Imaging in the STXM

A number of microscopic techniques are used to produce images containing information on the distribution of the elements in biological tissue. Principally, these are visible and U.V. microscopy fluorescence light microscopy, EDS electron microscopy, WDS electron microscopy, EELS electron microscopy, and SIMS. Of the above techniques, those most widely used for elemental mapping are visible/U.V. light microscopy [1] and EDS electron microscopy [2]. With the advent of bright x-ray sources and improving x-ray optics, it is now possible to image a range of elements (in wet and dry systems) using soft x-rays in the scanning x-ray microscope (STXM). X-ray absorption difference imaging (XADI) utilizes natural changes in the absorption of x-rays for small increments in x-ray energy to produce an elemental map of a specimen.