| 1. |
- Bengtsson, S., et al.
(author)
-
Space–time control of free induction decay in the extreme ultraviolet
- 2017
-
In: Nature Photonics. - : Springer Science and Business Media LLC. - 1749-4885 .- 1749-4893. ; 11:4, s. 252-258
-
Journal article (peer-reviewed)abstract
- Ultrafast extreme-ultraviolet (XUV) and X-ray sources are revolutionizing our ability to follow femtosecond processes with ångström-scale resolution. The next frontier is to simultaneously control the direction, duration and timing of such radiation. Here, we demonstrate a fully functional opto-optical modulator for XUV light, similar to modulators available at infrared (IR) and visible wavelengths. It works by using an IR pulse to control the spatial and spectral phase of the free induction decay that results from using attosecond pulses to excite a gas. The modulator allows us to send the XUV light in a direction of our choosing at a time of our choosing. The inherent synchronization of the XUV emission to the control pulse will allow laser-pump/X-ray probe experiments with sub-femtosecond time resolution.
|
|
| 2. |
- El Hassan, Ashraf, 1976-, et al.
(author)
-
Corner states of light in photonic waveguides
- 2019
-
In: Nature Photonics. - : Springer Science and Business Media LLC. - 1749-4885 .- 1749-4893. ; 13:10, s. 697-700
-
Journal article (peer-reviewed)abstract
- The recently established paradigm of higher-order topological states of matter has shown that not only edge and surface states but also states localized to corners, can have robust and exotic properties. Here we report on the experimental realization of novel corner states made out of visible light in three-dimensional photonic structures inscribed in glass samples using femtosecond laser technology. By creating and analysing waveguide arrays, which form two-dimensional breathing kagome lattices in various sample geometries, we establish this as a platform for corner states exhibiting a remarkable degree of flexibility and control. In each sample geometry we measure eigenmodes that are localized at the corners in a finite frequency range, in complete analogy with a theoretical model of the breathing kagome. Here, measurements reveal that light can be ‘fractionalized,’ corresponding to simultaneous localization to each corner of a triangular sample, even in the presence of defects.
|
|
| 3. |
- Freitag, Marina, et al.
(author)
-
Dye-sensitized solar cells for efficient power generation under ambient lighting
- 2017
-
In: Nature Photonics. - : NATURE PUBLISHING GROUP. - 1749-4885 .- 1749-4893. ; 11:6, s. 372-
-
Journal article (peer-reviewed)abstract
- Solar cells that operate efficiently under indoor lighting are of great practical interest as they can serve as electric power sources for portable electronics and devices for wireless sensor networks or the Internet of Things. Here, we demonstrate a dye-sensitized solar cell (DSC) that achieves very high power-conversion efficiencies (PCEs) under ambient light conditions. Our photosystem combines two judiciously designed sensitizers, coded D35 and XY1, with the copper complex Cu(II/I)(tmby) as a redox shuttle (tmby, 4,4', 6,6'-tetramethyl-2,2'-bipyridine), and features a high open-circuit photovoltage of 1.1 V. The DSC achieves an external quantum efficiency for photocurrent generation that exceeds 90% across the whole visible domain from 400 to 650 nm, and achieves power outputs of 15.6 and 88.5 mu W cm(-2) at 200 and 1,000 lux, respectively, under illumination from a model Osram 930 warm-white fluorescent light tube. This translates into a PCE of 28.9%.
|
|
| 4. |
- Gorkhover, Tais, et al.
(author)
-
Femtosecond and nanometre visualization of structural dynamics in superheated nanoparticles
- 2016
-
In: Nature Photonics. - : Springer Science and Business Media LLC. - 1749-4885 .- 1749-4893. ; 10:2, s. 93-97
-
Journal article (peer-reviewed)abstract
- The ability to observe ultrafast structural changes in nanoscopic samples is essential for understanding non-equilibrium phenomena such as chemical reactions, matter under extreme conditions, ultrafast phase transitions and intense light-matter interactions. Established imaging techniques are limited either in time or spatial resolution and typically require samples to be deposited on a substrate, which interferes with the dynamics. Here, we show that coherent X-ray diffraction images from isolated single samples can be used to visualize femtosecond electron density dynamics. We recorded X-ray snapshot images from a nanoplasma expansion, a prototypical non-equilibrium phenomenon. Single Xe clusters are superheated using an intense optical laser pulse and the structural evolution of the sample is imaged with a single X-ray pulse. We resolved ultrafast surface softening on the nanometre scale at the plasma/vacuum interface within 100 fs of the heating pulse. Our study is the first time-resolved visualization of irreversible femtosecond processes in free, individual nanometre-sized samples.
|
|
| 5. |
- Gorkhover, Tais, et al.
(author)
-
Femtosecond X-ray Fourier holography imaging of free-flying nanoparticles
- 2018
-
In: Nature Photonics. - : Springer Science and Business Media LLC. - 1749-4885 .- 1749-4893. ; 12:3, s. 150-153
-
Journal article (peer-reviewed)abstract
- Ultrafast X-ray imaging on individual fragile specimens such as aerosols 1 , metastable particles 2 , superfluid quantum systems 3 and live biospecimens 4 provides high-resolution information that is inaccessible with conventional imaging techniques. Coherent X-ray diffractive imaging, however, suffers from intrinsic loss of phase, and therefore structure recovery is often complicated and not always uniquely defined 4,5 . Here, we introduce the method of in-flight holography, where we use nanoclusters as reference X-ray scatterers to encode relative phase information into diffraction patterns of a virus. The resulting hologram contains an unambiguous three-dimensional map of a virus and two nanoclusters with the highest lateral resolution so far achieved via single shot X-ray holography. Our approach unlocks the benefits of holography for ultrafast X-ray imaging of nanoscale, non-periodic systems and paves the way to direct observation of complex electron dynamics down to the attosecond timescale.
|
|
| 6. |
- Hammarström, Per, 1972-
(author)
-
BIOLUMINESCENCE IMAGING Photonic amyloids
- 2019
-
In: Nature Photonics. - : Nature Publishing Group. - 1749-4885 .- 1749-4893. ; 13:7, s. 442-444
-
Journal article (peer-reviewed)abstract
- Emerging data reveal that amyloid fibrils possess intrinsic photonic activity, showing luminescence over a wide range of the electromagnetic spectrum from the ultraviolet to the near-infrared.
|
|
| 7. |
- Hartmann, N., et al.
(author)
-
Attosecond time-energy structure of X-ray free-electron laser pulses
- 2018
-
In: Nature Photonics. - : Springer Science and Business Media LLC. - 1749-4885 .- 1749-4893. ; 12:4, s. 215-220
-
Journal article (peer-reviewed)abstract
- The time-energy information of ultrashort X-ray free-electron laser pulses generated by the Linac Coherent Light Source is measured with attosecond resolution via angular streaking of neon 1s photoelectrons. The X-ray pulses promote electrons from the neon core level into an ionization continuum, where they are dressed with the electric field of a circularly polarized infrared laser. This induces characteristic modulations of the resulting photoelectron energy and angular distribution. From these modulations we recover the single-shot attosecond intensity structure and chirp of arbitrary X-ray pulses based on self-amplified spontaneous emission, which have eluded direct measurement so far. We characterize individual attosecond pulses, including their instantaneous frequency, and identify double pulses with well-defined delays and spectral properties, thus paving the way for X-ray pump/X-ray probe attosecond free-electron laser science. © 2018 The Author(s).
|
|
| 8. |
- Hickstein, Daniel D., et al.
(author)
-
Non-collinear generation of angularly isolated circularly polarized high harmonics
- 2015
-
In: Nature Photonics. - 1749-4885 .- 1749-4893. ; 9:11, s. 743-750
-
Journal article (peer-reviewed)abstract
- We generate angularly isolated beams of circularly polarized extreme ultraviolet light through the first implementation of non-collinear high harmonic generation with circularly polarized driving lasers. This non-collinear technique offers numerous advantages over previous methods, including the generation of higher photon energies, the separation of the harmonics from the pump beam, the production of both left and right circularly polarized harmonics at the same wavelength and the capability of separating the harmonics without using a spectrometer. To confirm the circular polarization of the beams and to demonstrate the practicality of this new light source, we measure the magnetic circular dichroism of a 20 nm iron film. Furthermore, we explain the mechanisms of non-collinear high harmonic generation using analytical descriptions in both the photon and wave models. Advanced numerical simulations indicate that this non-collinear mixing enables the generation of isolated attosecond pulses with circular polarization.
|
|
| 9. |
- Kfir, Ofer, et al.
(author)
-
Generation of bright phase-matched circularly-polarized extreme ultraviolet high harmonics
- 2015
-
In: Nature Photonics. - 1749-4885 .- 1749-4893. ; 9:2, s. 99-105
-
Journal article (peer-reviewed)abstract
- Circularly-polarized extreme ultraviolet and X-ray radiation is useful for analysing the structural, electronic and magnetic properties of materials. To date, such radiation has only been available at large-scale X-ray facilities such as synchrotrons. Here, we demonstrate the first bright, phase-matched, extreme ultraviolet circularly-polarized high harmonics source. The harmonics are emitted when bi-chromatic counter-rotating circularly-polarized laser pulses field-ionize a gas in a hollow-core waveguide. We use this new light source for magnetic circular dichroism measurements at the M-shell absorption edges of Co. We show that phase-matching of circularly-polarized harmonics is unique and robust, producing a photon flux comparable to linearly polarized high harmonic sources. This work represents a critical advance towards the development of table-top systems for element-specific imaging and spectroscopy of multiple elements simultaneously in magnetic and other chiral media with very high spatial and temporal resolution.
|
|
| 10. |
- Liu, Xiao-Jing, et al.
(author)
-
Einstein-Bohr recoiling double-slit gedanken experiment performed at the molecular level
- 2015
-
In: Nature Photonics. - 1749-4885 .- 1749-4893. ; 9:2, s. 120-125
-
Journal article (peer-reviewed)abstract
- Double-slit experiments illustrate the quintessential proof for wave-particle complementarity. If information is missing about which slit the particle has traversed, the particle, behaving as a wave, passes simultaneously through both slits. This wave-like behaviour and corresponding interference is absent if 'which-slit' information exists. The essence of Einstein-Bohr's debate about wave-particle duality was whether the momentum transfer between a particle and a recoiling slit could mark the path, thus destroying the interference. To measure the recoil of a slit, the slits should move independently. We showcase a materialization of this recoiling double-slit gedanken experiment by resonant X-ray photoemission from molecular oxygen for geometries near equilibrium (coupled slits) and in a dissociative state far away from equilibrium (decoupled slits). Interference is observed in the former case, while the electron momentum transfer quenches the interference in the latter case owing to Doppler labelling of the counter-propagating atomic slits, in full agreement with Bohr's complementarity.
|
|
