Wavefront Sensor Testing at APS, April 2023

I’m very proud of some recent work testing our prototype wavefront sensor at hard x-ray wavelengths. We felt very fortunate to have this rare opportunity to test several optical elements, with kind help from the APS team led by Lahsen Assoufid. Prof. Yamauchi made this possible by sharing a new adaptive x-ray mirror made by JTEC for this collaborative work.

Testing the ALS wavefront sensor at the Advanced Photon Source, 29-ID. Wojdyla, Bryant, Goldberg

April 2023

Shi, Wojdyla, Frith, Goldberg, Highland, Bryant at 29-ID, APS

April 2023

The SHARP High-NA Actinic Reticle review Program, 2013–

SHARP, the SHARP High-NA Actinic Reticle review Program
SHARP, the SHARP High-NA Actinic Reticle review Program
The SHARP Team 2014
The SHARP Team 2014, Alex Donahue, David Johnson, Markus Benk, Antoine Wojdyla, Kenneth Goldberg
SHARP zone plate array chip
SHARP zone plate array chip, with magnetic features and ruby balls for kinematic positioning
SHARP zone plate Chip array mounted in a kinematic holder
SHARP zone plate Chip array mounted in a kinematic holder
The SHARP Team collecting data
SHARP Team collecting data, David Johnson, Alex Donahue, Chris Anderson, Antoine Wojdyla, Kenneth Goldberg, Markus Benk

Commissioning and aligning the Microfield Exposure Tool (MET), 2003

Commissioning the two-mirror MET, 0.3-NA optic at 13.4-nm wavelength.
Commissioning the MET 0.3-NA, two-mirror optic at 13.4-nm wavelength.
Shown are [Goldberg, Naulleau, Denham]
High-NA null test to calibrate the system geometry. The iamges shows fringes that have a slightly hyberbolic profile due to the planar camera catching a spherical beam.
At high-NA, measurement accuracy is incredibly sensitive to the alignment and geometry. We devised a null-test to provide an absolute measurement of the system geometry for calibration of all other tests.
In a focusing system, the Foucault Test (or Knife-Edge test) is easy to interpret, independent of calibration.
The Foucault Test or (Knife-Edge) test is the easiest to perform, and easiest to interpret. Indepenent of the geometry, the light and dark pattern here reveals the x-derivative of the wavefront error in this moment. The 3rd-order pattern reveals a 4th-order, spherical aberration, which we corrected.
PS/PDI was very difficult to perform owing to the sub-15-nm pinhole sizes. We made it work using a real-time holographic feedback approach that we invented.
Applying our highest-accuracy technique Phase-Shifting Point-Diffraction Interferometry (PS/PDI) was a challenging task since the pinholes were below 15 nm wide and hard to find. We used a real-time holographic feedback approach that we invented, and software I wrote to visualize the data as we aligned the beam. This was a beautiful optic!
Single-grating shearing interferometry at 13.4-nm wavelength.
Shearing interferometry quickly became our favorite approach. Alignment is trivial, the efficiency is high, and the data is easy to analyze. Now, single-grating shearing is used in many beamline applications worldwide.

Measurement of the EUV Test Stand (ETS) 0.1-NA projection lens, 2000

Measurement of the Engineering Test Stand (ETS) at the ALS
Measurement of the Engineering Test Stand (ETS) at ALS Beamline 12.0.1. Shown are Kenneth Goldberg, Jeffrey Bokor, Patrick Naulleau
Sharing interferogram and Fourier transform analysis of the ETS EUV Engineering Test Stand optic
EUV Lateral Shearing Interferometry at 13.4 nm wavelength, and analysis performed with the Fourier Transform method of phase retrieval in orthogonal directions. A single, two-dimensional cross-grating divides the beam. This approach is now sometimes mistakenly called Talbot Interferometry. (Originally, Talbot Interferometry was a two-grating approach.)

Phase-shifting Point Diffraction Interferometry (PS/PDI), 1998

The PS/PSI and team in 1998
We measured a series of EUV Schwarzschild objective lenses of increasing quality, over several years. The lenses were the Berkeley 10x, The Sandia lens, Tinsley A, Tinsley B1, and Tinsley B2. In these tests, we reached diffraction-limited docusing, developed single-grating shearing interferometry, showed flare measurement, holographic imaging, and more. Shown are Paul Denham, Kenneth Goldberg, Patrick Naulleau.
The interferometer reached an accuracy of 1/300th of the EUV wavelength, below 50 pm. For this work, Goldberg and Naulleau shared the ALS Halbach Prize for Instrumentation. Goldberg and Naulleau are presented with the award by Werner Meyer-Ilse.

Coherent EUV Optics at the ALS, 1994

First Point Diffraction Interferometer tests at EUV wavelengths.
In 1994, we conducted the first Point Diffraction Interferometer (PID) tests at EUV wavelengths. These were among the first experiments at the newly opened Advanced Light Source (ALS). We measured the wavefront aberrations in a Fresnel zone plate lens at 13.4 nm wavelength