Wavefront sensors are an important tool to characterize coherent beams of extreme ultraviolet radiation. However, conventional Hartmann-type sensors do not allow for independent wavefront characterization of different spectral components that may be present in a beam, which limits their applicability for intrinsically broadband high-harmonic generation (HHG) sources. Here we introduce a wavefront sensor that measures the wavefronts of all the harmonics in a HHG beam in a single camera exposure. By replacing the mask apertures with transmission gratings at different orientations, we simultaneously detect harmonic wavefronts and spectra, and obtain sensitivity to spatiotemporal structure such as pulse front tilt as well. We demonstrate the capabilities of the sensor through a parallel measurement of the wavefronts of 9 harmonics in a wavelength range between 25 and 49 nm, with up to λ/32 precision.

Opt. Express
EUV Generation & Imaging

Freisem, L., Jansen, M., Rudolf, D., Eikema, K., & Witte, S. (2018). Spectrally resolved single-shot wavefront sensing of broadband high-harmonic sources. Opt. Express, 26(6), 6860–6871. doi:10.1364/OE.26.006860