Spectroscopy with EUV light

In a recently published manuscript, researchers in the group of Stefan Witte (ARCNL/ VU) describe a method they developed to perform spectroscopy with Extreme Ultraviolet (EUV)  light. The researchers published their findings in the journal Optica.

EUV light
EUV light is radiation with a much shorter wavelength than visible light, typically in the range between 10 to 100 nanometer. Such EUV radiation has several properties that make it highly interesting for materials science; it can be used for imaging with extremely high resolution, and various opaque materials become partially transparent in the EUV regime.

Spectroscopy
Spectroscopy is a widespread technique to essentially get an optical fingerprint of different materials, by measuring the wavelengths of light that interact with a material. However, spectroscopy with EUV light instead of visible light is highly challenging. The ARCNL research team were the first ones to develop a technique using a table-top EUV source for spectroscopy experiments that also provides spatial resolution. This new approach enables measurements to determine the exact location of a specific element in a structured object.

Experiment
Getting to EUV spectroscopy called for an inventive approach. The researchers carried out an experiment using a technique called ‘high-harmonic generation’ to generate  laser-like beams of EUV radiation. They then used Fourier transform spectroscopy to produce two coherent extreme-ultraviolet pulses with a precisely controlled time delay.  The method worked as shown by a demonstration in which the local composition of a metal thin film was identified.

Schematics of the specialized systems developed by the ARCNL team for EUV spectroscopy. Also shown are EUV interference patterns produced in two different gases (Argon and Neon).

Reference
G.S.M. Jansen, D. Rudolf, L. Freisem, K.S.E. Eikema, S. Witte, Spatially resolved Fourier transform spectroscopy in the extreme ultraviolet, Optica 3, 1122-1125 (2016)