optics – Lightsources.org

Installation of SESAME’s HESEB soft X-ray beamline starts

2022/02/082022/02/10

From 9^th to 27^th January, a team from the German company FMB Feinwerk- und Meßtechnik GmbH in Berlin that was awarded the contract for construction of HESEB, the Helmholtz-SESAME Beamline for soft X-ray spectroscopy, together with SESAME’s team, installed the complete front-end and optics of the beamline at the ID 11 port of the SESAME ring.

In 2019, five research centers of the German Helmholtz Association, DESY (Deutsches Elektronen-Synchrotron), FZJ (Forschungszentrum Jülich), HZB (Helmholtz-Zentrum Berlin), HZDR (Helmholtz-Zentrum Dresden-Rossendorf), and KIT (Karlsruher Institut für Technologie), joined forces to implement a new, state-of-the-art soft X-ray beamline at SESAME. The HESEB project is being generously funded to the order of 3.5 M€ by the Initiative & Networking Fund of the Helmholtz Association.

The source will be a refurbished BESSY-II UE56 APPLE-II undulator provided by HZB.

HESEB will be the first soft X-ray beamline at SESAME and will significantly expand the research capabilities available to the user community in the Middle East and neighbouring regions. The undulator’s ability to provide linearly to circularly polarized light makes the beamline very suitable for materials science applications, especially magnetic materials. Its plane grating monochromator uses exchangeable gratings to cover a photon energy range from 70 eV to 2000 eV.

Image: The HESEB project team during installation at SESAME of the front-end and optics of the beamline

Credit: © SESAME 2022

Read more on the SESAME website and see a time-lapse video of the HESEB installation below:

One of the most exciting things is being part of the community

2022/01/192022/01/19

FERMI #LightSourceSelfie

Michele Manfredda is an Italian physicist working at FERMI, the Free Electron laser Radiation for Multidisciplinary Investigations, near Trieste in Italy. Michele words in the PADReS group, which stands for photon analysis delivery and reduction system. The group’s role is to make experiments possible for FERMI users and they look after the optics and diagnostics of the light. As Michele explains, the role involves working in different places and with different teams. His #LightSourceSelfie takes viewers on a fantastic tour of FERMI.

Michele explains that he was first attracted to this field of research by the fact that simple things are done in a very complicated way. When it comes to advice that Michele would give those starting out in their careers, he says, “The advice I would give to someone entering the world of large facilities is go for it. They are crazy environments and you will enjoy it, but remember large facilities can be very time-consuming. So always keep in mind what you can give to science and what science can give you back. Also, find the right people. People you can learn from and people you like to work with because remember, science facilities are wonderful creations but the most wonderful creation is your career, your life. So, as an optical physicist, I tell you don’t be focused on your sample only, be focused mostly on you.”

Using strain to control echoes in ultrafast optics

2021/12/152021/12/16

Researchers at MAX IV measured echoes produced by silicon crystals using the coherent X-ray based technique, tele-ptychography, at NanoMAX imaging beamline. Their findings reveal that strain can be used to tune the time delay of echoes, an important step for tailoring ultrafast X-ray optics.

“The use of coherent X-rays to visualize echoes is new. This is the first time it has been used for this purpose, however, the technique itself is not new,” said Dina Carbone, MAX IV Beamline Scientist and project leader.

Echoes are parallel, monochromatic X-ray beams which appear, with time delay, from the diffraction of perfect crystals, which are often used in ultrafast optics systems. Dynamical diffraction effects produce echoes.

Echoes are difficult to observe because of their proximity to each other—only a few microns apart—and appear even closer in the presence of strain, explained Carbone. “We knew it would become possible to see them using this new special approach. It would also be quite a challenge because we had to build an ad-hoc setup at NanoMAX. The experience of the group from PSI [Paul Scherrer Institute] was quite crucial.”

Diamond-II programme set to transform UK science

2021/07/162021/07/28

Diamond Light Source has established itself as a world-class synchrotron facility enabling research by leading academic and industrial groups in physical and life sciences. Diamond has pioneered a model of highly efficient and uncompromised infrastructure offered as a user-focussed service driven by technical and engineering innovation.

To continue delivering the world-changing science that Diamond leads and enables, Diamond-II is a co-ordinated programme of development that combines a new machine and new beamlines with a comprehensive series of upgrades to optics, detectors, sample environments, sample delivery capabilities and computing. The user experience will be further enhanced through access to integrated and correlative methods as well as broad application of automation in both instrumentation and analysis. Diamond-II will be transformative in both spatial resolution and throughput and will offer users streamlined access to enhanced instruments for life and physical sciences.

Read more on the Diamond website

Image: Diamond’s synchrotron building

Credit: Diamond Light Source

Unravelling the molecular structure, self-assembly, and properties of a cephalopod protein variant

2021/04/062021/05/06

Cephalopods, such as the loliginid in Figure 1A, are known for their remarkable ability to rapidly change the color and appearance of their skin. These capabilities are enabled in part by unique structural proteins called reflectins, which play essential roles in optical behavior of cephalopod skin cells. Moreover, reflectins have demonstrated exciting potential as functional materials within the context of biophotonic and bioelectronic systems. Given reflectins’ demonstrated significance from both fundamental biology and applications perspectives, some research effort has been devoted to resolving their three-dimensional (3D) structures. However, the peculiar sequence composition of reflectins has made them extremely sensitive to subtle changes in environmental conditions and prone to aggregation, thus significantly complicating the study of their structure-function relationships and precluding their definitive molecular-level structural characterization. In this work, we have elucidated the structure of a reflectin variant at the molecular level, demonstrated a robust methodology for controlling its assembly and optical properties.

We began our studies by rationally selecting a prototypical reflectin variant (RfA1TV) by using a bioinformatics-guided approach (Figure 1B). Next, we not only produced the variant in high yield and purity but also optimized conditions for maintaining this protein in a monomeric state (Figure 1C). We then probed the protein with small angle X-ray scattering (SAXS) using the Austrian SAXS beamline at the Elettra Synchrotron Laboratory in Trieste, Italy. For this purpose, a well-dispersed solution of RfA1TV was prepared in a low-pH buffer and transferred into a glass capillary, which was positioned in the path of an incident X-ray beam. The X-rays scattered by the solution-borne RfA1TV molecules formed a 2-D pattern on a Pilatus3 1M detector (Figure 1D). Subsequently, radial averaging and image calibration of the two-dimensional data furnished corresponding one-dimensional curves, which were further processed, analyzed, and correlated with other experiments to obtain insight into the protein’s geometry (Figure 1E).

Read more on the Elettra website

Image: (A) A camera image of a Doryteuthis pealeii squid. (B) An illustration of the selection of the prototypical truncated reflectin variant (RfA1TV) from full-length Doryteuthis pealeii reflectin A1. (C) A digital camera image of a solution of primarily monomeric RfA1TV (Upper) and a corresponding cartoon of RfA1TV monomers (Lower Inset). (D) An illustration of the SAXS analysis of the reflectin variant, wherein incident X-rays are scattered by the solution-borne proteins to furnish a corresponding scattering pattern. (E)The 3D structure of RfA1TV (random coils – gray, helices – orange, β-strands – purple).

Credit: This figure has been adapted from M. J. Umerani*, P. Pratakshya* et al.Proc. Natl. Acad. Sci. U.S.A 117, 32891-32901 (2020).

Crystals, lasers, glasses, and bent molecules: adventures in nonlinear optics

2020/04/222020/04/22

Light is an indispensable scientific tool. For example, laser-based optical sensors can detect oxygen in the environment, proteins in biomedical samples, and process markers in industrial settings, among other applications. However, not all wavelengths of light can be generated by a single laser, which limits what chemicals can be detected with optical sensing. That’s where nonlinear optical crystals can help. By shining multiple lasers with different wavelengths through such crystals, researchers can tune laser beams via frequency conversion and cover more of the optical spectra. This has been a successful approach for wavelengths from ultraviolet to near-infrared(IR), but the mid-IR region has lacked practical nonlinear optical crystals. However, crystals may not be the only game in town. A multi-institution international research team is exploring a possible solution to the crystal problem: cutting-edge glasses containing mercuric iodide. The idea is that these glasses could behave like nonlinear optical crystals, offering an enticing approach to the generation of novel amorphous optical materials. But first, the researchers needed to figure out what these glasses look like at the atomic scale. For that, they went to the U.S. Department of Energy’s (DOE’s) Advanced Photon Source (APS) to collect high-energy x-ray diffraction data. By combining the diffraction data with other structural data and computer modeling, the team uncovered the secrets behind how a glass can act like a crystal.

Nonlinear optical crystals are widely used in photonics applications, but can be challenging to synthesize. To sidestep the need for crystals, scientists have been pursuing glassy materials that can tune lasers. One challenge is that glassy materials with isotropic internal structures aren’t able to perform the frequency conversion necessary to tune lasers. However, glasses with chiral asymmetric properties have nonlinear optical potential. This research team is investigating hybrid molecular/network glasses with non-centrosymmetric mercuric iodide (HgI₂).

Image: Schematic representation of second harmonic generation as light passes through bent HgI2 molecules adopting a non-random orientation within mesoscopic domains of sulfide glass.

New optical device opens path for extreme focusing of X-rays

2019/12/022019/12/09

Adaptable refractive correctors for X-ray optics

An innovative new type of optical component for X-rays has been developed by a scientific team in the Optics and Metrology Group at Diamond Light Source. This new optical component is designed to correct for the effect of imperfections in the optical elements used for focusing of X-rays. It works by introducing a controlled change to the X-ray’s phase. It is known as an “adaptable refractive corrector” – so called because the corrector uses refraction and can adapt the correction to the unique imperfection of any optical element. The researchers have designed and tested such a component at Diamond obtaining reductions in the effect of the imperfections in a range of mirror and lens focusing optical elements by a factor of up to 7. This development is expected to have application to new developing techniques such as hard X-ray microscopy at the nanometre scale.

Image: Schematic showing the adaptable corrector with a double mirror system.

How virtual photons alter atomic X-ray spectra

2019/03/292019/04/04

Control out of the vacuum, virtually

Certain X-ray optical properties of metal atoms can be controlled with the help of virtual photons. This has been demonstrated for the first time by a DESY research team at PETRA III, by using the highly brilliant radiation from this X-ray light source at DESY. In the journal Physical Review Letters they report on how the X-ray spectra of metal atoms can be controlled by virtual photons. This opens up new possibilities for specifically modifying the X-ray optical properties of materials.
So-called virtual photons play an important role in the interaction of light and matter. This is quite remarkable because they do not exist in the classical sense. Virtual photons are created in the vacuum out of nothing and then disappear again after an extremely short time. If these photons interact during their short existence with the electrons of an atom, the binding energies of the electrons shift ever so slightly.

Image: Experimental setup to measure the collective Lamb shift at tantalum.
Credit: DESY, Haber et al.

Towards X-ray transient grating spectroscopy at SwissFEL

2019/03/012019/04/16

The high brilliance of new X-ray sources such as X-ray Free Electron Laser opens the way to non-linear spectroscopies.

These techniques can probe ultrafast matter dynamics that would otherwise be inaccessible. One of these techniques, Transient Grating, involves the creation of a transient excitation grating by crossing X-ray beams on the sample. Scientists at PSI have realized a demonstration of such crossing by using an innovative approach well suited for the hard X-ray regime. The results of their work at the Swiss Free Electron Laser have been published in the journal Optics Letters.
Non-linear optics is an important field of physics where the non-linear response of matter in extreme electromagnetic fields is studied and exploited for novel applications. It has been widely used for creating new laser wavelengths (Sum/Difference Frequency Generation – S/DFG) as well as for studying a variety of properties such as charge, spin, magnetic transfer as well as heat diffusion. A broad class of non-linear spectroscopy is Four Wave Mixing (FWM) where three laser beams are overlapped in space and time in a sample and a fourth beam with different wavelength and angle is detected, background free. This allows studying specific transitions and selectively excite the sample tuning the incoming beams’ wavelength while studying their dynamics by controlling the relative time delays between the laser pulses. Transient Grating (TG) spectroscopy is a special case of degenerate FWM where two of the incoming beams have the same wavelength and are crossed at the sample creating an interference pattern, or transient grating, which excites the sample as long as the field is present. When the TG impinges on the material, its index of refraction is locally perturbed and electrons exposed to the radiation are excited. These electrons then transfer their extra energy to the lattice and the heat is then dissipated by the system. A third beam, delayed with respect to the pump TG, probes the dynamics of this excitation.

Image: Layout depicting the experimental conditions at the Alvra experimental station. (Find all the details here)

World record: Fastest 3D tomographic images at BESSY II

2018/08/082018/08/09

An HZB team has developed an ingenious precision rotary table at the EDDI beamline at BESSY II and combined it with particularly fast optics.

This enabled them to document the formation of pores in grains of metal during foaming processes at 25 tomographic images per second – a world record.

The quality of materials often depends on the manufacturing process. In casting and welding, for example, the rate at which melts solidify and the resulting microstructure of the alloy is important. With metallic foams as well, it depends on exactly how the foaming process takes place. To understand these processes fully requires fast sensing capability. The fastest 3D tomographic images to date have now been achieved at the BESSY II X-ray source operated by the Helmholtz-Zentrum Berlin.

Dr. Francisco Garcia-Moreno and his team have designed a turntable that rotates ultra-stably about its axis at a constant rotational speed. This really depends on the highest precision: Any tumbling around the rotation axis or even minimal deviations in the rotation speed would prevent the reliable calculation of the 3D tomography. While commercially available solutions costing several hundred thousand euros allow up to 20 tomographic images per second, the Berlin physicists were able to develop a significantly cheaper solution that is even faster. ”My two doctoral students at the Technische Universität Berlin produced the specimen holders themselves on the lathe”, says Garcia-Moreno, who not only enjoys working out solutions to tricky technical problems, but possesses a lot of craftsman skill himself as well. Additional components were produced in the HZB workshop. In addition, Garcia-Moreno and his colleague Dr. Catalina Jimenez had already developed specialized optics for the fast CMOS camera during the preliminary stages of this work that allows even for simultaneous diffraction. This makes it possible to record approximately 2000 projections per second, from which a total of 25 three-dimensional tomographic images can be created.

Image: Experimental setup is composed of a fast-rotation stage, an IR heating lamp (temperature up to 800 °C), a BN crucible transparent to X-rays, a 200-μm thick LuAG:Ce scintillator, a white-beam optical system, and a PCO Dimax CMOS camera. The incident (red) and transmitted (green) X-ray beams as well as the light path from the scintillator to the camera (blue) are shown.
Credit: HZB

Scientists have a new way to gauge the growth of nanowires

2018/03/192018/03/27

In a new study, researchers from the U.S. Department of Energy’s Argonne and Brookhaven National Laboratories observed the formation of two kinds of defects in individual nanowires, which are smaller in diameter than a human hair.

These nanowires, made of indium gallium arsenide, could be useful for a wide range of applications in a field scientists have termed optoelectronics, which encompasses devices that work by converting light energy into electrical impulses. Fiber optic relays are a good example.

The effectiveness of these devices, however, can be affected by tiny defects in their components. These defects, which can change both the optical and electronic properties of these materials, interest scientists who seek to tailor them to boost the functionality of future optoelectronics, including materials that will be able to manipulate quantum information.

>Read more on the NSLS-II website and the Advanced Photon Source website

Image: Argonne and Brookhaven researchers observed two kinds of defects forming in individual nanowires, depicted here. These nanowires are smaller in diameter than a human hair.
Credit: Megan Hill/Northwestern University

A comparison of the etch mechanisms of germanium and silicon

2018/02/132018/02/15

Time multiplexed, deep reactive ion etching (DRIE) is a standard silicon microfabrication technique for fabricating MEMS sensors, actuators, and more recently in CMOS development for 2.5D and 3D memory devices.

At CHESS, we have adopted this microfabrication technique to develop novel x-ray optics called,Collimating Channel Arrays (CCAs) [1], for confocal x-ray fluorescence microscopy (CXRF). Because the first CCA optics were fabricated from silicon substrates, the range of x-ray fluorescence energies for which they could be used, and hence the elements they could be used to study, was limited. Unwanted x-rays above about 11 keV could penetrate through the silicon, showing up as background and interfering with the measurement.

To solve the background problem, germanium substrates were used to fabricate the CCA optics. Germanium, which is much denser and therefore x-ray opaque than silicon, is also etch compatible with the fluorine etch chemistry for silicon DRIE. However, small differences in etch behavior between germanium and silicon can cause big differences in the outcome. Here, Genova et al JVST B [2] report a systematic comparison of the etch mechanisms of silicon and germanium, performed with the Plasma Therm Versaline deep silicon etcher at the Cornell NanoScale Science & Technology Facility (CNF). The etch rates of silicon and germanium were compared by varying critical parameters in the DRIE process, especially the applied power and voltage used for each of 3 steps in the etch process, on custom-designed wafers with a variety of features with systematically varying dimensions.

>Read more on the CHESS website

Image: (extract, full image here) SEM of high aspect ratio (>13:1) etched features in Si at 3.7 μm/min (a) and Ge at 3.4 μm/min (b)

Scientists demonstrate unparalleled phase control of free-electron laser pulses

2017/05/302017/10/09

Double flashes with attosecond precision

Thanks to a smart mirror scientists can control the phase of X-rays from DESY’s free-electron laser FLASH with attosecond precision. The feat enables new investigations of the interactions of light and matter, as the team headed by DESY scientist Tim Laarmann reports in the journal Nature Communications. An attosecond is a billionth of a billionth of a second. The phase indicates at which point in its rapid oscillation a light wave is at a given point in time or space. Phase-sensitive measurements are important to gain insight of light-matter interactions and require phase-controlled pulses. Although phase control is an established technique in optics, the soft X-rays generated by FLASH oscillate a hundred times faster than visible light, requiring a hundred times better precision.

The scientists have now demonstrated phase control and interferometric autocorrelation at FLASH using pulse pairs created with a smart split-and-delay unit. The successful transfer of a powerful optical method towards short wavelengths paves the way towards utilization of advanced nonlinear methodologies even at partially coherent free-electron lasers that rely on self-amplified spontaneous emission (SASE). Free-electron lasers (FEL) are driven by powerful particle accelerators and produce laser-like light pulses by sending bunches of fast electrons through a magnetic slalom course.

>Read More