Design Of Multilayer Mirrors Research Articles

Multistrip multilayer mirrors for sources based on inverse Compton scattering

A technique has been developed for calculating the periods of multi-strip multilayer mirrors for effective use with sources based on the inverse Compton effect. A model for constructing the multi-strip mirror is presented. The model has been developed in accordance with modern capabilities for creating multilayer X-ray mirrors. The reflection coefficients and fractions of the energy emitted by the source that are reflected are compared for total external reflection, for multilayer Goebel mirrors and for multi-strip mirrors. It is shown that the multi-strip design of multilayer mirrors proposed in the work is almost an order of magnitude superior to Goebel mirrors and to mirrors based on the total external reflection effect in terms of the efficiency of use of the source energy.

Optimization of dielectric films with dual ion beam sputtering deposition for high reflectivity mirrors

Abstract Dielectric thin films deposited by Ion beam sputtering deposition technique have superior properties of good adhesion and customized optical properties suits to many optical filters for electro-optical sensors. In the present work Tantalum Pentoxide (Tantala) and Silicon Dioxide (Silica) thin films are fabricated with dual ion beam sputtering deposition process. The process parameters are optimized to achieve better surface quality and optical constants. The effect of the assist ion beam on the film properties is evaluated. Multi-layer dielectric mirrors realized with 1000 ppm loss on optimization of single-layer Silica and Tantala films, which will be suitable for linear and Ring Laser Resonators. The films are characterized by ellipsometer, non-contact optical profiler, spectrophotometer, and cavity ring-down loss meter. The multi-layer mirrors were subjected to vacuum annealing and the effect of annealing on film reflectivity is evaluated. The work emphasizes the process requirements of Ion Beam Sputtering to realize high reflectivity and low loss mirrors of Tantala and Silica films from Ta2O5 and SiO2 target materials. It gives an insight into the process deficiencies in matching the theoretical design of multi-layer mirrors from the practical aspects of coatings.

Trilayer model in design of W/C multilayer mirrors with a small period thickness

In the design of a W/C multilayer mirror, we applied a trilayer model to consider the interdiffusion of tungsten and carbon on the W-on-C interface and investigated the first Bragg angle and its reflectivity. As the interdiffusion thickness of a W/C multilayer mirror increased, the first Bragg angle and the reflected X-ray energy increased. However, as the period thickness of the W/C multilayer mirror increased, the effects of the interdiffusion became less pronounced. The criteria for the use of either the bilayer or the trilayer models for the design of W/C multilayer mirrors were presented for various period thicknesses. The trilayer model would be useful for the design of multilayer mirrors with a small period thickness of less than approximately 4.0 nm at an interdiffusion of 0.28 nm.

Synthesis of controlled semi-reflecting multilayer broad band mirrors

Broad-band dielectric multilayer mirrors formed by staggering achromatic periods are developed here to reach multilayer systems of controlled reflectance as well as band width. The basic theory and the complete synthesis procedure are presented for the design of multilayer mirrors with controlled reflectance. Six designs with different reflectance levels, ranging from 44% up to 90%, average reflectance over the whole visible region, are presented. These broad mirrors are useful in many research experiments of interferometry and spectroscopy.

Design of multi-layer mirrors for measuring optical phase modulation at 1300 nm

A theoretical design and experimental realization of multi-layer mirrors for Fabry–Perot interferometry and optical telecommunications is described in this work. The mirrors were designed and fabricated by 13 successive thin layers to achieve very high reflectance at optical wavelengths around 1300 nm. Thin layers are ZnS and MgF 2 presenting high and low refractive index, respectively. Layer thickness λ o/2 at λ o=656 nm. Experimental results include characterization of transmittance of mirrors around 1300 nm. Additionally, the mirrors were integrated in a Fabry–Perot interferometer to characterize optical sources emitting at 1300 nm. Finally to show a practical application, optical phase modulation was analyzed, using the fabricated mirrors through a scanning Fabry–Perot interferometer acting as high-resolution optical spectrum analyzer (OSA).

Optimization of multilayer mirrors at 134 nm with more than two materials

The design of multilayer mirrors with more than two materials is one of the key technologies for investigating lithography. We study a new procedure for optimizing multilayer mirrors of different combinations of materials at a wavelength of 13.4 nm. By adding Be and C layers in different orders to a Si/Mo stack, we have observed enhancement of the reflectivity and a reduction in the number of layers. The Luus-Jaakola optimization procedure has been implemented for the global optimization of the multilayer mirrors. With this algorithm it is not necessary to specify initially the number of layers present in a given design.

ANALYTICAL AND NUMERICAL ASPECTS OF BRAGG FIBER DESIGN

Analytical theory and numerical approaches to the simulation and optimal design of multilayer mirrors and optical Bragg waveguides are developed. Optimal refractive index profiles in planar and cylindrical geometry are found. Reduction of the full set of Maxwell’s equations to a scalar boundary value problem in the lowcontrast approximation is discussed. An efficient finite-difference scheme is used to simulate realistic Bragg fibers.

Design of multilayer mirrors for XUV applications using simulated annealing

By combining previous multilayer optics design methods a multilayer mirror (MLM) optimisation programme has been developed to provide a versatile tool for MLM design for the XUV range. The programme uses a simulated annealing algorithm to avoid the design of suboptimal multilayered stacks. Investigations have been carried out on the influence of the computational sublayer thickness used in the computation and on the algorithm for reducing the simulated annealing temperature. The optimisation programme allows variation of the angle of incident radiation, the interface roughness and the number of different materials within the MLM structure. The possibility of optimising the performance of the MLM using different merit functions or reflectivity profiles has been implemented. Variation of the incidence angle allows the design of polarisers by optimising at the Brewster angle and ratios of R/Rp around 10 3 are achieved for specific wavelengths. To select a specific line from a superimposed line and continuum spectrum a selective merit function is used. By maximising the ratio of the relevant line throughput to the continuum throughput, such MLM designs can be used to select a specific line from an electron impact or laser plasma source spectrum for microscopy or microbeam radiation experiments.

Selection and suppression of soft x-ray spectral features using optimized multilayer coatings

The design of multilayer mirrors which specifically select or suppress spectral features is described. To illustrate the method, the spectra from laser-produced plasmas of carbon and aluminium are used. By using a suitable mirror the intensity of the C V Heα line at λ = 4.03 nm can be reduced to 1.1 × 10 −4 of that in the C VI Lyα line at λ = 3.37 nm, compared to 0.97 in the source emission spectrum and 1.6 × 10 −2 for a periodic multilayer. In the aluminium spectrum, two closely spaced lines at λ = 3.505 and 3.660 nm, which have comparable emitted intensities, can be individually selected using pairs of multilayers. The reflected intensity ratios are under ten for periodic multilayers, but can be over 300 for the shorter wavelength line and almost 140 for the longer using optimized pairs of mirrors.

Fast imaging of hard x rays with a laboratory microscope

An improved x-ray microscope with a fully electronic CCD detector system has been constructed that allows improved laboratory-based microstructural investigations of materials with hard x rays. It uses the Kirkpatrick-Baez multilayer mirror design to form an image that has a demonstrated resolution of 4 microm at 8 keV (Cu K(alpha) radiation). This microscope performs well with standard sealed-tube laboratory x-ray sources, producing digital images with 20-s exposure times for a 5-microm Au grid (a thickness of two absorption lengths).

Multilayer mirrors and filters for imaging the earth's inner magnetosphere

We present guidelines for the performance of multilayer mirrors and filters for imaging the earth's inner magnetosphere by isolating the 304-Å He⁺ emission. Our analysis shows that the combination of filters and multilayer mirrors for an inner magnetosphere imager must attenuate the 1216-Å Lyman α emission by six orders of magnitude and the 584-, 834-, and 1026-Å background emissions by three orders of magnitude relative to the 304-Å signal. Multilayer mirrors with the highest possible reflectance at 304 Å are needed to preserve as much of the low-intensity 304-Å signal as possible. The design of multilayer mirrors is discussed, and the results of an exhaustive computer search for the best multilayer mirror design for 304-Å radiation are presented and analyzed. The theoretical performance of these new multilayer mirror designs is significantly better than that of designs currently used for imaging the solar 304-Å emission. Promising materials for normal-incidence multilayer mirrors for 304-Å radiation are B₄C, Be, Si, or SiC used with Al, Mg, or Mg2Si. Promising materials for a filter for this application are Te passivated with Si, or a combination of Al or Si with B or C.