X-Ray Propagation in Tapered Waveguides: Simulation and Optimization

TL;DR

This paper employs the parabolic wave equation to simulate and optimize tapered x-ray waveguides, aiming to enhance beam concentration for applications like biomolecule investigation, highlighting the complexity of the optimization landscape.

Contribution

It introduces a simulation and optimization framework for tapered x-ray waveguides using parametrized geometries and analyzes the ruggedness of the gain landscape.

Findings

Tapered geometries can be parametrized by linear and Bezier functions.

The optimization landscape is highly rugged and complex.

Optimized waveguides can improve x-ray beam concentration.

Abstract

We use the parabolic wave equation to study the propagation of x-rays in tapered waveguides by numercial simulation and optimization. The goal of the study is to elucidate how beam concentration can be best achieved in x-ray optical nanostructures. Such optimized waveguides can e.g. be used to investigate single biomolecules. Here, we compare tapering geometries, which can be parametrized by linear and third-order (Bezier-type) functions and can be fabricated using standard e-beam litography units. These geometries can be described in two and four-dimensional parameter spaces, respectively. In both geometries, we observe a rugged structure of the optimization problem's ``gain landscape''. Thus, the optimization of x-ray nanostructures in general will be a highly nontrivial optimization problem.