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Enumeration	Reference	Cover	Find
1.	Abramson, Nils (author) FEMTOSECOND IMAGING Motion picture of short pulses 2011 In: Nature Photonics. - : Springer Science and Business Media LLC. - 1749-4885 .- 1749-4893. ; 5:7, s. 389-390 Journal article (peer-reviewed)
2.	Agåker, Marcus, et al. (author) Spectroscopy in the vacuum-ultraviolet 2011 In: Nature Photonics. - : Springer Science and Business Media LLC. - 1749-4885 .- 1749-4893. ; 5:5, s. 248-248 Journal article (peer-reviewed)
3.	Albinsson, Bo, 1963, et al. (author) Untapping solar energy resources 2020 In: Nature Photonics. - : Springer Science and Business Media LLC. - 1749-4885 .- 1749-4893. ; 14:9, s. 528-530 Journal article (other academic/artistic)
4.	Arnold, Cord L., et al. (author) Lightning protection by laser 2023 In: Nature Photonics. - : Springer Science and Business Media LLC. - 1749-4885 .- 1749-4893. ; 17:3, s. 211-212 Journal article (peer-reviewed)
5.	Barty, A., et al. (author) Self-terminating diffraction gates femtosecond X-ray nanocrystallography measurements 2012 In: Nature Photonics. - 1749-4885 .- 1749-4893. ; 6:1, s. 35-40 Journal article (peer-reviewed)abstract X-ray free-electron lasers have enabled new approaches to the structural determination of protein crystals that are too small or radiation-sensitive for conventional analysis1. For sufficiently short pulses, diffraction is collected before significant changes occur to the sample, and it has been predicted that pulses as short as 10 fs may be required to acquire atomic-resolution structural information1, 2, 3, 4. Here, we describe a mechanism unique to ultrafast, ultra-intense X-ray experiments that allows structural information to be collected from crystalline samples using high radiation doses without the requirement for the pulse to terminate before the onset of sample damage. Instead, the diffracted X-rays are gated by a rapid loss of crystalline periodicity, producing apparent pulse lengths significantly shorter than the duration of the incident pulse. The shortest apparent pulse lengths occur at the highest resolution, and our measurements indicate that current X-ray free-electron laser technology5 should enable structural determination from submicrometre protein crystals with atomic resolution.
6.	Barty, Anton, et al. (author) Ultrafast single-shot diffraction imaging of nanoscale dynamics 2008 In: Nature Photonics. - : Springer Science and Business Media LLC. - 1749-4885 .- 1749-4893. ; 2:7, s. 415-419 Journal article (peer-reviewed)abstract The transient nanoscale dynamics of materials on femtosecond to picosecond timescales is of great interest in the study of condensed phase dynamics such as crack formation, phase separation and nucleation, and rapid fluctuations in the liquid state or in biologically relevant environments. The ability to take images in a single shot is the key to studying non-repetitive behaviour mechanisms, a capability that is of great importance in many of these problems. Using coherent diffraction imaging with femtosecond X-ray free-electron-laser pulses we capture time-series snapshots of a solid as it evolves on the ultrafast timescale. Artificial structures imprinted on a Si3N4 window are excited with an optical laser and undergo laser ablation, which is imaged with a spatial resolution of 50 nm and a temporal resolution of 10 ps. By using the shortest available free-electron-laser wavelengths(1) and proven synchronization methods(2) this technique could be extended to spatial resolutions of a few nanometres and temporal resolutions of a few tens of femtoseconds. This experiment opens the door to a new regime of time-resolved experiments in mesoscopic dynamics.
7.	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.
8.	Bohm, Christian, et al. (author) A MHz-repetition-rate hard X-ray free-electron laser driven by a superconducting linear accelerator 2020 In: Nature Photonics. - : Springer Science and Business Media LLC. - 1749-4885 .- 1749-4893. ; 14:6, s. 391-397 Journal article (peer-reviewed)abstract The European XFEL is a hard X-ray free-electron laser (FEL) based on a high-electron-energy superconducting linear accelerator. The superconducting technology allows for the acceleration of many electron bunches within one radio-frequency pulse of the accelerating voltage and, in turn, for the generation of a large number of hard X-ray pulses. We report on the performance of the European XFEL accelerator with up to 5,000 electron bunches per second and demonstrating a full energy of 17.5 GeV. Feedback mechanisms enable stabilization of the electron beam delivery at the FEL undulator in space and time. The measured FEL gain curve at 9.3 keV is in good agreement with predictions for saturated FEL radiation. Hard X-ray lasing was achieved between 7 keV and 14 keV with pulse energies of up to 2.0 mJ. Using the high repetition rate, an FEL beam with 6 W average power was created. The first operation of the European X-ray free-electron laser facility accelerator based on superconducting technology is reported. The maximum electron energy is 17.5 GeV. A laser average power of 6 W is achieved at a photon energy of 9.3 keV.
9.	Canalias, Carlota, et al. (author) Mirrorless optical parametric oscillator 2007 In: Nature Photonics. - : Springer Science and Business Media LLC. - 1749-4885 .- 1749-4893. ; 1:8, s. 459-462 Journal article (peer-reviewed)abstract Parametric interaction of counterpropagating photons has the unique property of automatically establishing distributed feedback and thus realizing novel sources of coherent and tunable radiation, such as mirrorless optical parametric oscillators. This device does not require alignment or any optical components other than the second-order nonlinear medium itself(1). Here we present the first experimental demonstration of such an oscillator, which was made feasible by quasi phase-matching in a nonlinear photonic structure with submicrometre periodicity. This type of oscillator has been extensively discussed as a theoretical possibility(1-5). It generates signal and idler waves in the near- and mid-infrared, respectively, and exhibits unique and useful spectral properties. The oscillator signal is essentially a wavelength-shifted replica of the pump spectrum, and the bandwidth of the idler is two orders of magnitude narrower than that of the pump. It also has very low output wavelength sensitivity to temperature variations.
10.	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.
11.	Elshaari, Ali W., et al. (author) Correction: Hybrid integrated quantum photonic circuits (Apr, 10.1038/s41566-020-0609-x, 2020) 2020 In: Nature Photonics. - : Springer Nature. - 1749-4885 .- 1749-4893. ; 14:5 Journal article (peer-reviewed)
12.	Elshaari, Ali W., et al. (author) Hybrid integrated quantum photonic circuits 2020 In: Nature Photonics. - : Springer Nature. - 1749-4885 .- 1749-4893. ; 14:5, s. 285-298 Journal article (peer-reviewed)abstract Recent developments in chip-based photonic quantum circuits have radically impacted quantum information processing. However, it is challenging for monolithic photonic platforms to meet the stringent demands of most quantum applications. Hybrid platforms combining different photonic technologies in a single functional unit have great potential to overcome the limitations of monolithic photonic circuits. Our Review summarizes the progress of hybrid quantum photonics integration, discusses important design considerations, including optical connectivity and operation conditions, and highlights several successful realizations of key physical resources for building a quantum teleporter. We conclude by discussing the roadmap for realizing future advanced large-scale hybrid devices, beyond the solid-state platform, which hold great potential for quantum information applications.
13.	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%.
14.	Gahl, Cornelius, et al. (author) A femtosecond X-ray/optical cross-correlator 2008 In: Nature Photonics. - : Springer Science and Business Media LLC. - 1749-4885 .- 1749-4893. ; 2:3, s. 165-169 Journal article (peer-reviewed)abstract For a fundamental understanding of ultrafast dynamics in chemistry, biology and materials science it has been a long-standing dream to record a molecular movie in which both the atomic trajectories and the chemical states of every atom in matter are followed in real time(1). Free- electron lasers provide this perspective as they deliver brilliant femtosecond X-ray pulses spanning a wide photon energy range, which is necessary to gather element- specific and chemical- stateselective information with femtosecond time resolution. The key challenge lies in synchronizing the free- electron lasers with separate optical lasers. We exploit the peak brilliance of the free- electron laser in Hamburg(2,3) ( FLASH) and establish X- raypulseinduced transient changes of the optical reflectivity in GaAs as a powerful tool for X- ray/ optical cross- correlation. This constitutes a breakthrough in the path towards recording a molecular movie and - equally importantly - opens up the field of femtosecond X- ray- induced dynamics, only accessible with high- brilliance X- ray free- electron lasers.
15.	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.
16.	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.
17.	Hamel, Deny R., et al. (author) Direct generation of three-photon polarization entanglement 2014 In: Nature Photonics. - 1749-4885 .- 1749-4893. ; 8:10 Journal article (peer-reviewed)abstract Non-classical states of light are of fundamental importance for emerging quantum technologies. All optics experiments producing multi-qubit entangled states have until now relied on outcome post-selection, a procedure where only the measurement results corresponding to the desired state are considered. This method severely limits the usefulness of the resulting entangled states. Here, we show the direct production of polarization-entangled photon triplets by cascading two entangled downconversion processes. Detecting the triplets with high-efficiency superconducting nanowire single-photon detectors allows us to fully characterize them through quantum state tomography. We use our three-photon entangled state to demonstrate the ability to herald Bell states, a task that was not possible with previous three-photon states, and test local realism by violating the Mermin and Svetlichny inequalities. These results represent a significant breakthrough for entangled multi-photon state production by eliminating the constraints of outcome post-selection, providing a novel resource for optical quantum information processing.
18.	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.
19.	Hanczyc, Piotr, 1985, et al. (author) Multiphoton absorption in amyloid protein fibres 2013 In: Nature Photonics. - : Springer Science and Business Media LLC. - 1749-4885 .- 1749-4893. ; 7:12, s. 969-972 Journal article (peer-reviewed)abstract Fibrillization of peptides leads to the formation of amyloid fibres, which, when in large aggregates, are responsible for diseases such as Alzheimer's and Parkinson's. Here, we show that amyloids have strong nonlinear optical absorption, which is not present in native non-fibrillized protein. Z-scan and pump-probe experiments indicate that insulin and lysozyme β-amyloids, as well as α-synuclein fibres, exhibit either two-photon, three-photon or higher multiphoton absorption processes, depending on the wavelength of light. We propose that the enhanced multiphoton absorption is due to a cooperative mechanism involving through-space dipolar coupling between excited states of aromatic amino acids densely packed in the fibrous structures. This finding will provide the opportunity to develop nonlinear optical techniques to detect and study amyloid structures and also suggests that new protein-based materials with sizable multiphoton absorption could be designed for specific applications in nanotechnology, photonics and optoelectronics.
20.	Hantke, Max F., et al. (author) High-throughput imaging of heterogeneous cell organelles with an X-ray laser 2014 In: Nature Photonics. - : Springer Science and Business Media LLC. - 1749-4885 .- 1749-4893. ; 8:12, s. 943-949 Journal article (peer-reviewed)abstract We overcome two of the most daunting challenges in single-particle diffractive imaging: collecting many high-quality diffraction patterns on a small amount of sample and separating components from mixed samples. We demonstrate this on carboxysomes, which are polyhedral cell organelles that vary in size and facilitate up to 40% of Earth's carbon fixation. A new aerosol sample-injector allowed us to record 70,000 low-noise diffraction patterns in 12 min with the Linac Coherent Light Source running at 120 Hz. We separate different structures directly from the diffraction data and show that the size distribution is preserved during sample delivery. We automate phase retrieval and avoid reconstruction artefacts caused by missing modes. We attain the highest-resolution reconstructions on the smallest single biological objects imaged with an X-ray laser to date. These advances lay the foundations for accurate, high-throughput structure determination by flash-diffractive imaging and offer a means to study structure and structural heterogeneity in biology and elsewhere.
21.	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).
22.	Helgason, Òskar Bjarki, 1989, et al. (author) Dissipative solitons in photonic molecules 2021 In: Nature Photonics. - : Springer Science and Business Media LLC. - 1749-4885 .- 1749-4893. ; 15:4, s. 305-310 Journal article (peer-reviewed)abstract Many physical systems display quantized energy states. In optics, interacting resonant cavities show a transmission spectrum with split eigenfrequencies, similar to the split energy levels that result from interacting states in bonded multi-atomic—that is, molecular—systems. Here, we study the nonlinear dynamics of photonic diatomic molecules in linearly coupled microresonators and demonstrate that the system supports the formation of self-enforcing solitary waves when a laser is tuned across a split energy level. The output corresponds to a frequency comb (microcomb) whose characteristics in terms of power spectral distribution are unattainable in single-mode (atomic) systems. Photonic molecule microcombs are coherent, reproducible and reach high conversion efficiency and spectral flatness while operated with a laser power of a few milliwatts. These properties can favour the heterogeneous integration of microcombs with semiconductor laser technology and facilitate applications in optical communications, spectroscopy and astronomy.
23.	Helgason, Òskar Bjarki, 1989, et al. (author) Surpassing the nonlinear conversion efficiency of soliton microcombs 2023 In: Nature Photonics. - 1749-4885 .- 1749-4893. ; 17:11, s. 992-999 Journal article (peer-reviewed)abstract Laser frequency combs are enabling some of the most exciting scientific endeavours in the twenty-first century, ranging from the development of optical clocks to the calibration of the astronomical spectrographs used for discovering Earth-like exoplanets. Dissipative Kerr solitons generated in microresonators currently offer the prospect of attaining frequency combs in miniaturized systems by capitalizing on advances in photonic integration. Most of the applications based on soliton microcombs rely on tuning a continuous-wave laser into a longitudinal mode of a microresonator engineered to display anomalous dispersion. In this configuration, however, nonlinear physics precludes one from attaining dissipative Kerr solitons with high power conversion efficiency, with typical comb powers amounting to ~1% of the available laser power. Here we demonstrate that this fundamental limitation can be overcome by inducing a controllable frequency shift to a selected cavity resonance. Experimentally, we realize this shift using two linearly coupled anomalous-dispersion microresonators, resulting in a coherent dissipative Kerr soliton with a conversion efficiency exceeding 50% and excellent line spacing stability. We describe the soliton dynamics in this configuration and find vastly modified characteristics. By optimizing the microcomb power available on-chip, these results facilitate the practical implementation of a scalable integrated photonic architecture for energy-efficient applications.
24.	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.
25.	Houard, Aurélien, et al. (author) Laser-guided lightning 2023 In: Nature Photonics. - : Springer Nature. - 1749-4885 .- 1749-4893. ; 17:3, s. 231-235 Journal article (peer-reviewed)abstract Lightning discharges between charged clouds and the Earth's surface are responsible for considerable damages and casualties. It is therefore important to develop better protection methods in addition to the traditional Franklin rod. Here we present the first demonstration that laser-induced filaments-formed in the sky by short and intense laser pulses-can guide lightning discharges over considerable distances. We believe that this experimental breakthrough will lead to progress in lightning protection and lightning physics. An experimental campaign was conducted on the Santis mountain in north-eastern Switzerland during the summer of 2021 with a high-repetition-rate terawatt laser. The guiding of an upward negative lightning leader over a distance of 50 m was recorded by two separate high-speed cameras. The guiding of negative lightning leaders by laser filaments was corroborated in three other instances by very-high-frequency interferometric measurements, and the number of X-ray bursts detected during guided lightning events greatly increased. Although this research field has been very active for more than 20 years, this is the first field-result that experimentally demonstrates lightning guided by lasers. This work paves the way for new atmospheric applications of ultrashort lasers and represents an important step forward in the development of a laser based lightning protection for airports, launchpads or large infrastructures. A terawatt laser filament is shown to be able to guide lightning over a distance of 50 m in field trials on the Santis mountain in the Swiss Alps.
26.	Huang, Yuqing, et al. (author) Room-temperature electron spin polarization exceeding 90% in an opto-spintronic semiconductor nanostructure via remote spin filtering 2021 In: Nature Photonics. - : NATURE RESEARCH. - 1749-4885 .- 1749-4893. ; 15, s. 475-482 Journal article (peer-reviewed)abstract An exclusive advantage of semiconductor spintronics is its potential for opto-spintronics, which will allow integration of spin-based information processing/storage with photon-based information transfer/communications. Unfortunately, progress has so far been severely hampered by the failure to generate nearly fully spin-polarized charge carriers in semiconductors at room temperature. Here we demonstrate successful generation of conduction electron spin polarization exceeding 90% at room temperature without a magnetic field in a non-magnetic all-semiconductor nanostructure, which remains high even up to 110 degrees C. This is accomplished by remote spin filtering of InAs quantum-dot electrons via an adjacent tunnelling-coupled GaNAs spin filter. We further show that the quantum-dot electron spin can be remotely manipulated by spin control in the adjacent spin filter, paving the way for remote spin encoding and writing of quantum memory as well as for remote spin control of spin-photon interfaces. This work demonstrates the feasibility to implement opto-spintronic functionality in common semiconductor nanostructures. An electron spin polarization of 90% is achieved in a non-magnetic nanostructure at room temperature without magnetic field. This is accomplished by remote spin filtering of InAs quantum-dot electrons via an adjacent tunnelling-coupled GaNAs spin filter.
27.	Inganäs, Olle (author) ORGANIC PHOTOVOLTAICS Avoiding indium 2011 In: Nature Photonics. - : Nature Publishing Group. - 1749-4885 .- 1749-4893. Other publication (peer-reviewed)abstract n/a
28.	Jenkins, Amelia, et al. (author) Who needs mirrors? 2007 In: Nature Photonics. - Royal Inst Technol, Stockholm, Sweden. : NATURE PUBLISHING GROUP. - 1749-4885 .- 1749-4893. ; 1:8, s. 484-484 Journal article (other academic/artistic)
29.	Jiang, Jizhong, et al. (author) Synergistic strain engineering of perovskite single crystals for highly stable and sensitive X-ray detectors with low-bias imaging and monitoring 2022 In: Nature Photonics. - : Nature Portfolio. - 1749-4885 .- 1749-4893. ; 16:8, s. 575-581 Journal article (peer-reviewed)abstract X-ray detectors based on dual-site-doped perovskite single crystals exhibit excellent sensitivity of 2.6 x 10(4) mu C Gy(air)(-1) cm(-2) under a low field of 1 V cm(-1). The detectable dose rate is as low as 7.09 nGy(air) s(-1). The operational stability is beyond half a year. Although three-dimensional metal halide perovskite (ABX(3)) single crystals are promising next-generation materials for radiation detection, state-of-the-art perovskite X-ray detectors include methylammonium as A-site cations, limiting the operational stability. Previous efforts to improve the stability using formamidinium-caesium-alloyed A-site cations usually sacrifice the detection performance because of high trap densities. Here we successfully solve this trade-off between stability and detection performance by synergistic composition engineering, where we include A-site alloys to decrease the trap density and B-site dopants to release the microstrain induced by A-site alloying. As such, we develop high-performance perovskite X-ray detectors with excellent stability. Our X-ray detectors exhibit high sensitivity of (2.6 +/- 0.1) x 10(4) mu C Gy(air)(-1) cm(-2) under 1 V cm(-1) and ultralow limit of detection of 7.09 nGy(air) s(-1). In addition, they feature long-term operational stability over half a year and impressive thermal stability up to 125 degrees C. We further demonstrate the promise of our perovskite X-ray detectors for low-bias portable applications with high-quality X-ray imaging and monitoring prototypes.
30.	Jorgensen, A. A., et al. (author) Petabit-per-second data transmission using a chip-scale microcomb ring resonator source 2022 In: Nature Photonics. - : Springer Science and Business Media LLC. - 1749-4885 .- 1749-4893. ; 16:11, s. 798-802 Journal article (peer-reviewed)abstract Optical fibre communication is the backbone of the internet. As essential core technologies are approaching their limits of size, speed and energy-efficiency, there is a need for new technologies that offer further scaling of data transmission capacity. Here we show that a single optical frequency-comb source based on a silicon nitride ring resonator supports data capacities in the petabit-per-second regime. We experimentally demonstrate transmission of 1.84 Pbit s–1 over a 37-core, 7.9-km-long fibre using 223 wavelength channels derived from a single microcomb ring resonator producing a stabilized dark-pulse Kerr frequency comb. We also present a theoretical analysis that indicates that a single, chip-scale light source should be able to support 100 Pbit s–1 in massively parallel space-and-wavelength multiplexed data transmission systems. Our findings could mark a shift in the design of future communication systems, targeting device-efficient transmitters and receivers.
31.	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.
32.	Lindfors, Klas, et al. (author) Local polarization of tightly focused unpolarized light 2007 In: Nature Photonics. - : Springer Science and Business Media LLC. - 1749-4885 .- 1749-4893. ; 1:4, s. 228-231 Journal article (peer-reviewed)abstract The polarization of light is important in a great variety of optical phenomena, ranging from transmission, reflection and scattering to polarimetric imaging of scenes and quantum-mechanical selection rules of atomic and molecular transitions. Among some less-well-known phenomena that illustrate the vectorial nature of light are the Pancharatnam(1) (or geometric(2)) phase, singularities in the polarization pattern of clear sky(3) and polarization of microwave background radiation(4). Here, we examine the partial polarization of focused light. We experimentally demonstrate a rather surprising phenomenon, where the focusing of unpolarized light results in rings of full polarization in the focal plane of the focusing optics. The polarization rings are imaged with a resolution of < 100 nm by probing the focal region using a gold nanoparticle.
33.	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.
34.	Lutman, A. A., et al. (author) Polarization control in an X-ray free-electron laser 2016 In: Nature Photonics. - : Springer Science and Business Media LLC. - 1749-4885 .- 1749-4893. ; 10:7, s. 468-472 Journal article (peer-reviewed)abstract X-ray free-electron lasers are unique sources of high-brightness coherent radiation. However, existing devices supply only linearly polarized light, precluding studies of chiral dynamics. A device called the Delta undulator has been installed at the Linac Coherent Light Source (LCLS) to provide tunable polarization. With a reverse tapered planar undulator line to pre-microbunch the beam and the novel technique of beam diverting, hundreds of microjoules of circularly polarized X-ray pulses are produced at 500-1,200 eV. These X-ray pulses are tens of femtoseconds long, have a degree of circular polarization of 0.98(+0.02)(-0.04) at 707 eV and may be scanned in energy. We also present a new two-colour X-ray pump-X-ray probe operating mode for the LCLS. Energy differences of Delta E/E = 2.4% are supported, and the second pulse can be adjusted to any elliptical polarization. In this mode, the pointing, timing, intensity and wavelength of the two pulses can be modified.
35.	Marchesini, Stefano, et al. (author) Massively parallel X-ray holography 2008 In: Nature Photonics. - : Springer Science and Business Media LLC. - 1749-4885 .- 1749-4893. ; 2:9, s. 560-563 Journal article (peer-reviewed)abstract Advances in the development of free-electron lasers offer the realistic prospect of nanoscale imaging on the timescale of atomic motions. We identify X-ray Fourier-transform holography(1,2,3) as a promising but, so far, inefficient scheme to do this. We show that a uniformly redundant array(4) placed next to the sample, multiplies the efficiency of X-ray Fourier transform holography by more than three orders of magnitude, approaching that of a perfect lens, and provides holographic images with both amplitude-and phase-contrast information. The experiments reported here demonstrate this concept by imaging a nano-fabricated object at a synchrotron source, and a bacterial cell with a soft-X-ray free-electron laser, where illumination by a single 15-fs pulse was successfully used in producing the holographic image. As X-ray lasers move to shorter wavelengths we expect to obtain higher spatial resolution ultrafast movies of transient states of matter.
36.	Marklund, Mattias (author) Fundamental optical physics : probing the quantum vacuum 2010 In: Nature photonics. - : Springer Science and Business Media LLC. - 1749-4885 .- 1749-4893. ; 4:2, s. 72-74 Journal article (peer-reviewed)
37.	Maroju, Praveen Kumar, et al. (author) Attosecond coherent control of electronic wave packets in two-colour photoionization using a novel timing tool for seeded free-electron laser 2023 In: Nature Photonics. - : Springer Science and Business Media LLC. - 1749-4885 .- 1749-4893. ; 17, s. 200-207 Journal article (peer-reviewed)abstract In ultrafast spectroscopy, the temporal resolution of time-resolved experiments depends on the duration of the pump and probe pulses, and on the control and characterization of their relative synchronization. Free-electron lasers operating in the extreme ultraviolet and X-ray spectral regions deliver pulses with femtosecond and attosecond duration in a broad array of pump-probe configurations to study a wide range of physical processes. However, this flexibility, together with the large dimensions and high complexity of the experimental set-ups, limits control of the temporal delay to the femtosecond domain, thus precluding a time resolution below the optical cycle. Here we demonstrate a novel single-shot technique able to determine the relative synchronization between an attosecond pulse train-generated by a seeded free-electron laser-and the optical oscillations of a near-infrared field, with a resolution of one atomic unit (24 as). Using this attosecond timing tool, we report the first example of attosecond coherent control of photoionization in a two-colour field by manipulating the phase of high-order near-infrared transitions.
38.	Matsui, Yasuhiro, et al. (author) Low-chirp isolator-free 65-GHz-bandwidth directly modulated lasers 2021 In: Nature Photonics. - : Springer Nature. - 1749-4885 .- 1749-4893. ; 15:1, s. 59-63 Journal article (peer-reviewed)abstract Today, in the face of ever increasing communication traffic, minimizing power consumption in data communication systems has become a challenge. Direct modulation of lasers, a technique as old as lasers themselves, is known for its high energy efficiency and low cost. However, the modulation bandwidth of directly modulated lasers has fallen behind those of external modulators. In this Article, we report wide bandwidths of 65-75 GHz for three directly modulated laser design implementations, by exploiting three bandwidth enhancement effects: detuned loading, photon-photon resonance and in-cavity frequency modulation-amplitude modulation conversion. Substantial reduction of chirp (alpha < 1.0) as well as isolator-free operation under a reflection of up to 40% are also realized. A fast data transmission of 294.7 Gb s(-1) over15 km of a standard single-mode fibre in the O-band is demonstrated. This was achieved without an optical fibre amplifier due to a high laser output power of 13.6 dBm.
39.	Mikkelsen, Anders (author) Spectroscopy: Seeing excitations in a new light 2011 In: Nature Photonics. - : Springer Science and Business Media LLC. - 1749-4885 .- 1749-4893. ; 5:11, s. 650-653 Journal article (other academic/artistic)
40.	Mirian, N. S., et al. (author) Generation and measurement of intense few-femtosecond superradiant extreme-ultraviolet free-electron laser pulses 2021 In: Nature Photonics. - : Springer Science and Business Media LLC. - 1749-4885 .- 1749-4893. ; 15, s. 523-529 Journal article (peer-reviewed)abstract Free-electron lasers producing ultrashort pulses with high peak power promise to extend ultrafast non-linear spectroscopic techniques into the extreme-ultraviolet-X-ray regime. Key aspects are the synchronization between pump and probe, and the control of the pulse properties (duration, intensity and coherence). Externally seeded free-electron lasers produce coherent pulses that can be synchronized with femtosecond accuracy. An important goal is to shorten the pulse duration, but the simple approach of shortening the seed is not sufficient because of the finite-gain bandwidth of the conversion process. An alternative is the amplification of a soliton in a multistage, superradiant cascade: here, we demonstrate the generation of few-femtosecond extreme-ultraviolet pulses, whose duration we measure by autocorrelation. We achieve pulses four times shorter, and with a higher peak power, than in the standard high-gain harmonic generation mode and we prove that the pulse duration matches the Fourier transform limit of the spectral intensity distribution. By amplifying a soliton in a multistage cascade, few-femtosecond extreme-ultraviolet free-electron laser pulses are achieved.
41.	Oppeneer, Peter. M. (author) Materials Optics : Lighting Up Antiferromagnets 2017 In: Nature Photonics. - : NATURE PUBLISHING GROUP. - 1749-4885 .- 1749-4893. ; 11:2, s. 74-76 Journal article (other academic/artistic)abstract Weak coupling of light to the microscopic magnetic order in antiferromagnetic materials makes their optical characterization notoriously difficult. Now, a table-top magneto-optical technique has been developed for detecting the vector direction of antiparallel-aligned magnetic moments in a metallic antiferromagnet
42.	Oppeneer, Peter M., et al. (author) Plasmonic lasers turn magnetic 2022 In: Nature Photonics. - : Springer Nature. - 1749-4885 .- 1749-4893. ; 16:1, s. 11-13 Journal article (other academic/artistic)
43.	Porat, Gil, et al. (author) Phase-matched extreme-ultraviolet frequency-comb generation 2018 In: Nature Photonics. - : Springer Science and Business Media LLC. - 1749-4885 .- 1749-4893. ; 12:7, s. 387-391 Journal article (peer-reviewed)abstract Laser-driven high-order harmonic generation1,2 provides spatially3 and temporally4 coherent tabletop sources of broadband extreme-ultraviolet (XUV) light. These sources typically operate at low repetition rates, frep ≲ 100 kHz, where phase-matched HHG is readily achieved5,6. However, many applications demand the improved counting statistics or frequency-comb precision afforded by high repetition rates, frep > 10 MHz. Unfortunately, at such high frep, phase matching is prevented by steady-state plasma accumulated in the generation volume7–11, strongly limiting the XUV average power. Here, we use high-temperature gas mixtures as the generation medium to increase the gas translational velocity, thereby reducing the steady-state plasma in the laser focus. This allows phase-matched XUV emission inside a femtosecond enhancement cavity at frep = 77 MHz, enabling a record generated power of ~ 2 mW in a single harmonic order. This power scaling opens up many demanding applications, including XUV frequency-comb spectroscopy12,13 of few-electron atoms and ions for precision tests of fundamental physical laws and constants14–20.
44.	Rebernik Ribič, P., et al. (author) Coherent soft X-ray pulses from an echo-enabled harmonic generation free-electron laser 2019 In: Nature Photonics. - : Springer Science and Business Media LLC. - 1749-4885 .- 1749-4893. ; 13, s. 555-561 Journal article (peer-reviewed)abstract X-ray free-electron lasers (FELs), which amplify light emitted by a relativistic electron beam, are extending nonlinear optical techniques to shorter wavelengths, adding element specificity by exciting and probing electronic transitions from core levels. These techniques would benefit tremendously from having a stable FEL source, generating spectrally pure and wavelength-tunable pulses. We show that such requirements can be met by operating the FEL in the so-called echo-enabled harmonic generation (EEHG) configuration. Here, two external conventional lasers are used to precisely tailor the longitudinal phase space of the electron beam before emission of X-rays. We demonstrate high-gain EEHG lasing producing stable, intense, nearly fully coherent pulses at wavelengths as short as 5.9 nm (~211 eV) at the FERMI FEL user facility. Low sensitivity to electron-beam imperfections and observation of stable, narrow-band, coherent emission down to 2.6 nm (~474 eV) make the technique a prime candidate for generating laser-like pulses in the X-ray spectral region, opening the door to multidimensional coherent spectroscopies at short wavelengths. © 2019, The Author(s), under exclusive licence to Springer Nature Limited.
45.	Seifert, T., et al. (author) Efficient metallic spintronic emitters of ultrabroadband terahertz radiation 2016 In: Nature Photonics. - 1749-4885 .- 1749-4893. ; 10:7, s. 483- Journal article (peer-reviewed)abstract Terahertz electromagnetic radiation is extremely useful for numerous applications, including imaging and spectroscopy. It is thus highly desirable to have an efficient table-top emitter covering the 1-30 THz window that is driven by a low-cost, low-power femtosecond laser oscillator. So far, all solid-state emitters solely exploit physics related to the electron charge and deliver emission spectra with substantial gaps. Here, we take advantage of the electron spin to realize a conceptually new terahertz source that relies on three tailored fundamental spintronic and photonic phenomena in magnetic metal multilayers: ultrafast photoinduced spin currents, the inverse spin-Hall effect and a broadband Fabry-Perot resonance. Guided by an analytical model, this spintronic route offers unique possibilities for systematic optimization. We find that a 5.8-nm-thick W/CoFeB/Pt trilayer generates ultrashort pulses fully covering the 1-30 THz range. Our novel source outperforms laser-oscillator-driven emitters such as ZnTe(110) crystals in terms of bandwidth, terahertz field amplitude, flexibility, scalability and cost.
46.	Shapiro, David A., et al. (author) Chemical composition mapping with nanometre resolution by soft X-ray microscopy 2014 In: Nature Photonics. - : Springer Science and Business Media LLC. - 1749-4885 .- 1749-4893. ; 8:10, s. 765-769 Journal article (peer-reviewed)abstract X-ray microscopy is powerful in that it can probe large volumes of material at high spatial resolution with exquisite chemical, electronic and bond orientation contrast1, 2, 3, 4, 5. The development of diffraction-based methods such as ptychography has, in principle, removed the resolution limit imposed by the characteristics of the X-ray optics6, 7, 8, 9, 10. Here, using soft X-ray ptychography, we demonstrate the highest-resolution X-ray microscopy ever achieved by imaging 5 nm structures. We quantify the performance of our microscope and apply the method to the study of delithiation in a nanoplate of LiFePO4, a material of broad interest in electrochemical energy storage11, 12. We calculate chemical component distributions using the full complex refractive index and demonstrate enhanced contrast, which elucidates a strong correlation between structural defects and chemical phase propagation. The ability to visualize the coupling of the kinetics of a phase transformation with the mechanical consequences is critical to designing materials with ultimate durability.
47.	Simpson, Emma R., et al. (author) Complete polarization control 2018 In: Nature Photonics. - : Springer Science and Business Media LLC. - 1749-4885 .- 1749-4893. ; 12:6, s. 316-317 Journal article (peer-reviewed)abstract The polarization state of isolated attosecond pulses generated by high-order harmonic generation can now be manipulated at will. The development opens the door for a multitude of ultrafast experiments to investigate chiral media.
48.	Slavík, Radan, et al. (author) All-optical phase and amplitude regenerator for next-generation telecommunications systems 2010 In: Nature Photonics. - 1749-4885 .- 1749-4893. ; 4:10, s. 690-695 Journal article (peer-reviewed)abstract Fibre-optic communications systems have traditionally carried data using binary (on-off) encoding of the light amplitude. However, next-generation systems will use both the amplitude and phase of the optical carrier to achieve higher spectral efficiencies and thus higher overall data capacities. Although this approach requires highly complex transmitters and receivers, the increased capacity and many further practical benefits that accrue from a full knowledge of the amplitude and phase of the optical field more than outweigh this additional hardware complexity and can greatly simplify optical network design. However, use of the complex optical field gives rise to a new dominant limitation to system performance—nonlinear phase noise. Developing a device to remove this noise is therefore of great technical importance. Here, we report the development of the first practical (‘black-box’) all-optical regenerator capableof removing both phase and amplitude noise from binary phase-encoded optical communications signals.
49.	Sulzer, Philipp, et al. (author) Cavity-enhanced field-resolved spectroscopy 2022 In: Nature Photonics. - : Springer Science and Business Media LLC. - 1749-4885 .- 1749-4893. ; 16:10, s. 692-697 Journal article (peer-reviewed)abstract Femtosecond enhancement cavities1 are key to applications including high-sensitivity linear2–4 and nonlinear5,6 gas spectroscopy, as well as efficient nonlinear optical frequency conversion7–10. Yet, to date, the broadest simultaneously enhanced bandwidths amount to <20% of the central optical frequency8,9,11–15. Here, we present an ultrabroadband femtosecond enhancement cavity comprising gold-coated mirrors and a wedged-diamond-plate input coupler, with an average finesse of 55 for optical frequencies below 40 THz and exceeding 40 in the 120–300 THz range. Resonant enhancement of a 50-MHz-repetition-rate offset-free frequency comb spanning 22–40 THz results in a waveform-stable ultrashort circulating pulse with a spectrum supporting a Fourier limit of 1.6 cycles, enabling time-domain electric-field-resolved spectroscopy of molecular samples with temporally separated excitation and molecular response16. The contrast between the two is improved by taking advantage of destructive interference at the input coupler. At an effective interaction length with a gas of up to 81 m, this concept promises parts-per-trillion-level ultrabroadband electric-field-resolved linear and nonlinear spectroscopy of impulsively excited molecular vibrations.
50.	Tagarelli, Fedele, et al. (author) Electrical control of hybrid exciton transport in a van der Waals heterostructure 2023 In: Nature Photonics. - 1749-4885 .- 1749-4893. ; 17:7, s. 615-621 Journal article (peer-reviewed)abstract Interactions between out-of-plane dipoles in bosonic gases enable the long-range propagation of excitons. The lack of direct control over collective dipolar properties has so far limited the degrees of tunability and the microscopic understanding of exciton transport. In this work we modulate the layer hybridization and interplay between many-body interactions of excitons in a van der Waals heterostructure with an applied vertical electric field. By performing spatiotemporally resolved measurements supported by microscopic theory, we uncover the dipole-dependent properties and transport of excitons with different degrees of hybridization. Moreover, we find constant emission quantum yields of the transporting species as a function of excitation power with radiative decay mechanisms dominating over nonradiative ones, a fundamental requirement for efficient excitonic devices. Our findings provide a complete picture of the many-body effects in the transport of dilute exciton gases, and have crucial implications for studying emerging states of matter such as Bose–Einstein condensation and optoelectronic applications based on exciton propagation.

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