Damage-resistant single-pulse optics for x-ray free electron lasers

Abstract

Short-pulse ultraviolet and x-ray free electron lasers of unprecedented peak brightness are in the process of revolutionizing physics, chemistry, and biology. Optical components for these new light sources have to be able to withstand exposure to the extremely high-fluence photon pulses. Whereas most optics have been designed to stay intact for many pulses, it has also been suggested that single-pulse optics that function during the pulse but disintegrate on a longer timescale, may be useful at higher fluences than multiple-pulse optics. In this paper we will review damageresistant single-pulse optics that recently have been demonstrated at the FLASH soft-x-ray laser facility at DESY, including mirrors, apertures, and nanolenses. It was found that these objects stay intact for the duration of the 25-fs FLASH pulse, even when exposed to fluences that exceed the melt damage threshold by fifty times or more. We present a computational model for the FLASH laser-material interaction to analyze the extent to which the optics still function during the pulse. Comparison to experimental results obtained at FLASH shows good quantitative agreement.

Single-particle coherent diffractive imaging with a soft x-ray free electron laser: towards soot aerosol morphology

“…An unanticipated phenomenon was observed when SEM analysis of the aerosol samples was performed post-exposure to FLASH. The polystyrene spheres residing on the silicon portion of the substrate acted as nanolenses [25]. At a wavelength of 32 nm, the index of refraction is less than 1, and the sphere acts as a diverging lens.…”