Soft x-ray nanobeam formed by an ellipsoidal mirror

Abstract

Ellipsoidal mirrors are promising optical devices for soft x-ray focusing. A fabrication process consisting of master fabrication and replication has been developed to produce ellipsoidal mirrors with wide apertures of approximately 10 mm. In the present study, the focusing performance of an ellipsoidal mirror was evaluated using soft x-rays in the soft x-ray beamline BL25SU-a of SPring-8. The focus sizes were measured at photon energies of 300, 400, and 500 eV. A quantitative figure error of the ellipsoidal mirror was also evaluated by analyzing the wavefield of the focused beam retrieved using ptychography. The figure error distributions measured at different photon energies agreed with each other at a root mean square level of 1 nm. The developed focusing system can be used for various types of microscopy, allowing the use of a wide range of x-ray energies.

Derivation of closed-form ellipsoidal X-ray mirror shapes from Fermat's principle

“…1(b)] (Yumoto et al, 2017) or on-axis, with an annular shape [Fig. 1(a)] (Takeo et al, 2020). Rotational symmetry around the major axis, connecting the foci (i.e.…”

Metrology of a Focusing Capillary Using Optical Ptychography

“…For a perfectly fabricated capillary, a uniform residual phase is expected, while for the capillary measured in this work, we observed the residual phase varying within a range of radian. As the interaction between incident photons and the capillary inner surface is a total reflection, the residual phase can be modeled as the phase shift introduced by the optical path difference of beams reflected from a perfect ellipsoidal surface and a surface with local height errors [ 2 ]. As shown in Figure 5 d, the relationship between the residual phase and the height error h can be expressed as , where is the wavelength and is the incident angle on the ellipsoidal capillary surface [ 22 ].…”

“…They are widely used as the condenser optic for Transmission X-ray Microscopy. Recent fabrication advancement has successfully pushed the focal size to ∼200 nm [ 2 ]. Capillaries have been implemented as focusing optics in synchrotron [ 3 ] and FEL [ 4 ] applications.…”

Advanced fabrication technologies for ultraprecise replicated mirrors for x-ray telescopes

“…Because the thermal expansion coefficients of quartz glass and nickel are significantly different, these materials can be easily separated simply by dipping them in warm water. The mirrors we fabricated have been used for focusing soft X-rays in a beamline with high-order harmonics 15 , a synchrotron radiation facility 13,17 , and an X-ray free-electron laser facility 16 . Here we show an example of soft X-ray focusing at the SPring-8 synchrotron facility.…”

“…Although KB mirrors consist of vertical and horizontal focusing mirrors, an ellipsoidal mirror can focus X-rays in two dimensions with a single reflection, but improvement of the figuring accuracy is necessary for use in X-ray microscopy. We established an ellipsoidal mirror fabrication process employing mandrel fabrication and electroforming 13,14 , and successfully focused soft X-rays onto a spot several hundred nanometers wide [15][16][17] . A small Wolter-type mirror was also fabricated for imaging soft X-rays with a spatial resolution of 200 nm 18 .…”