Periodic Reporting for period 1 - EUVORAM (Extreme-Ultraviolet Meta-Optics for Attosecond Microscopy)
Période du rapport: 2023-01-01 au 2025-06-30
Extreme ultraviolet light sources have matured, both in brightness, as well as in producing ever shorter attosecond light pulses. On the contrary, transmissive Extreme ultraviolet optics remain sparse due to material absorption. Thus, extreme ultraviolet microscopy today focuses mainly on lensless techniques or secondary observables such as photoelectrons. EUVORAM (Extreme-Ultraviolet Meta-Optics for Attosecond Microscopy) aims to experimentally demonstrate that meta-optical devices are realizable in the extreme ultraviolet using a novel design approach and that they can solve the current lack of transmissive extreme ultraviolet optics. By emulating the spatial phase profiles of aspheric lenses, we will fabricate focusing meta-optics yielding near-diffraction limited microfoci in the extreme ultraviolet. Combined with contemporary attosecond pulse sources based on laser-driven high-harmonic generation, these meta-lenses will enable high-numerical-aperture extreme ultraviolet focusing that maintains attosecond pulse durations. EUVORAM will exploit this capacity to develop techniques to build a light microscope that unifies attosecond time and nanometer spatial resolution. After their demonstration, we will apply these techniques to follow the ultrafast hot electron dynamics and sub-nanometer charge transfers in individual plasmonic nanoparticles using spatially resolved attosecond transient absorption spectroscopy.
EUVORAM is one of the first projects connecting attosecond science and dielectric meta-surfaces. The planned extreme ultraviolet meta-optics and their novel design will undercut the current short-wavelength limit of meta-surface optics by a factor of five and thus directly redefine the state-of-the-art. The project will push lens-based microscopy to unprecedented time resolutions and at the same time allow hyperspectral attosecond imaging. The latter will free attosecond experiments from observing ensemble averages and provide spatially resolved insight into the light-matter interaction of photonic nanodevices.
EUVORAM is one of the first projects connecting attosecond science and dielectric meta-surfaces. The planned extreme ultraviolet meta-optics and their novel design will undercut the current short-wavelength limit of meta-surface optics by a factor of five and thus directly redefine the state-of-the-art. The project will push lens-based microscopy to unprecedented time resolutions and at the same time allow hyperspectral attosecond imaging. The latter will free attosecond experiments from observing ensemble averages and provide spatially resolved insight into the light-matter interaction of photonic nanodevices.
In the framework of the EUVORAM project, we successfully created an overview of candidate materials for achieving metasurfaces for different extreme ultraviolet wavelengths (10 – 120 nm). Using numerical modeling, we created libraries linking the material and shape of nanostructures to their optical transmission properties allowing us to emulate most classical optics by drilling tiny holes in silicon membranes.
In collaboration with Harvard University, we fabricated the first transmissive lens (and overall optics) for extreme ultraviolet light. We demonstrated at TU Graz that this device works and focuses light to minuscule spot sizes - close to the physical (diffraction) limit. Extrapolating these proof-of-principle results to metalenses with higher numerical apertures (with larger diameter or shorter focal length) suggests that the technology can focus light below 100 nm.
To test such lenses for even smaller focusing and show that they also work for the shortest light pulses available today, with funding from the ERC, we built a state-of-the-art beamline for extreme ultraviolet light and attosecond experiments. In this beamline, we implemented a novel measurement technique, with which we demonstrated we can generate and manipulate pulses lasting less than 0.000 000 000 000 001 seconds.
We are now working to combine extreme spatial with extreme temporal resolution and develop methods to implement an attosecond microscope. With leaders in the field, we reviewed the most promising techniques with similar goals and their prospects for advancing science and technology, e.g. to understand the very start of energy flow from light to electrons in solids, to enhance communication and computation towards petahertz speeds, or to optimize the efficiency of light harvesting devices such as solar cells.
Furthermore, with support from the ERC, we exploited that attosecond physics and comb-based spectroscopy both rely on knowing the absolute phase of light pulses to create better (dual-comb) spectrometers in collaboration with the Coherent Sensing Laboratory at TU Graz, explored how metalenses can enhance photoacoustic imaging with the Optics of Nano and Quantum Materials Laboratory at KFU Graz, and, in collaboration with Harvard University, demonstrated how metasurfaces can design the shape of light in microcavities with unprecedented freedom.
In collaboration with Harvard University, we fabricated the first transmissive lens (and overall optics) for extreme ultraviolet light. We demonstrated at TU Graz that this device works and focuses light to minuscule spot sizes - close to the physical (diffraction) limit. Extrapolating these proof-of-principle results to metalenses with higher numerical apertures (with larger diameter or shorter focal length) suggests that the technology can focus light below 100 nm.
To test such lenses for even smaller focusing and show that they also work for the shortest light pulses available today, with funding from the ERC, we built a state-of-the-art beamline for extreme ultraviolet light and attosecond experiments. In this beamline, we implemented a novel measurement technique, with which we demonstrated we can generate and manipulate pulses lasting less than 0.000 000 000 000 001 seconds.
We are now working to combine extreme spatial with extreme temporal resolution and develop methods to implement an attosecond microscope. With leaders in the field, we reviewed the most promising techniques with similar goals and their prospects for advancing science and technology, e.g. to understand the very start of energy flow from light to electrons in solids, to enhance communication and computation towards petahertz speeds, or to optimize the efficiency of light harvesting devices such as solar cells.
Furthermore, with support from the ERC, we exploited that attosecond physics and comb-based spectroscopy both rely on knowing the absolute phase of light pulses to create better (dual-comb) spectrometers in collaboration with the Coherent Sensing Laboratory at TU Graz, explored how metalenses can enhance photoacoustic imaging with the Optics of Nano and Quantum Materials Laboratory at KFU Graz, and, in collaboration with Harvard University, demonstrated how metasurfaces can design the shape of light in microcavities with unprecedented freedom.
Our central breakthrough was the demonstration of extreme ultraviolet metasurfaces and thus the introduction of the first universal transmissive optics technology for extreme ultraviolet light. From that development, many exciting opportunities arise: using the technology open paths to create holograms to shape extreme ultraviolet light in any shape, spiral phase plates to create optical angular momentum, and, with improved fabrication recipes, polarization optics for extreme ultraviolet light.
For us, the most exciting is the opportunity to create focusing optics with a high numerical aperture and a short focal length. Combined with our other breakthroughs, the design and commissioning of a flexible attosecond beamline, the generation of attosecond pulses via high-harmonic generation, and the implementation of a simplified ultrashort-pulse measurement technique to prove their time structure, this development opens a path towards light microscopy with extreme spatial and temporal resolution.
For us, the most exciting is the opportunity to create focusing optics with a high numerical aperture and a short focal length. Combined with our other breakthroughs, the design and commissioning of a flexible attosecond beamline, the generation of attosecond pulses via high-harmonic generation, and the implementation of a simplified ultrashort-pulse measurement technique to prove their time structure, this development opens a path towards light microscopy with extreme spatial and temporal resolution.