Periodic Reporting for period 4 - XSTREAM (X-ray-waveforms at the Space-Time Resolution Extreme for Atomic-scale Movies)
Okres sprawozdawczy: 2022-02-01 do 2023-07-31
Nonlinear optics and quantum optics revolutionized the ability to create coherent photons in broad regions of the electromagnetic spectrum where laser light based on conventional physics is not practical. Breakthroughs in attosecond science and extreme nonlinear optics promise a similar revolution in the X-ray regime. In an earlier breakthrough, an international team demonstrated that the high harmonic generation process driven by mid-IR laser fields can be used to generate 1.6 keV photons, implementing a 5000 order nonlinear process while still maintaining the phase synchronization necessary for good conversion efficiency. This work represents the most extreme coherent upconversion for electromagnetic waves in the 60 year history of nonlinear optics. Moreover, the limits are still uknown –theoretically or experimentally - it may be possible to create coherent hard X-rays using a laboratory-scale apparatus. In another surprising breakthrough, the team showed that UV-driven high harmonic generation in multiply ionized plasma can also be highly efficient, representing a second route towards the X-ray region. Remarkably, this regime provides X-rays with contrasting spectral and temporal properties. Furthermore, by shaping the spin angular momentum of a bi-color mid-IR field, the team demonstrated robust phase synchronization where the quantum properties of the driver are transferred to the generated X-rays.
In this ERC XSTREAM, the fundamental quantum physics and phase synchronization limits of the upconversion in the X-ray regime have been explored starting with three most promising approaches: I. mid-IR driven X-rays, II. UV driven X-rays, and III. all-optical phase synchronization in frequency and angular momentum mixing. XSTREAM aims to identify the best paths forward for generating bright coherent X-rays at photon energies of 1-10 keV with unprecedented attosecond-to-zeptosecond pulse durations and tunable classical and quantum properties of the light.
This X-ray research is relevant to areas of interest covered by academic, industrial, and defense programs supporting the second quantum revolution of 21st century. In perspective, compact non-diverging hard X-ray laser light would allow for remote delivery of penetrating radiation as a standoff detection where X-ray absorption and fluorescence spectroscopy determines elemental composition. Research on soft - hard X-ray light tools will also support the development of cutting edge nanoelectronics, atomtronics, new generation of magnetic storage key to society, efficient photovoltaics for green energy generation, and advanced bio-sensing and medical imaging. Our ability to directly observe function on the nanoscale with femtosecond or higher temporal resolution, in buried layers of quantum materials or next gen semiconductor chips, is still severely limited and can only be done at large scale facilities. Short and long range electron correlations, disorder, and impurities can govern the function of magnetic, superconducting nanosystems, and batteries. As a result, design rules for future nanosystems that operate at fundamental limits of quantum correlations, energy density, and speed, cannot be formulated until nanoscale structure and dynamics can be visualized and understood.
Inventing a coherent quantum version of the Roentgen X-ray tube that provides an exquisite control of all classical and quantum properties of light is a central part of the short and long term research of XSTREAM. Designer X-ray light with tunable spectral, spatial, temporal shape, and spin-orbital angular momentum, promises to be both a conceptual revolution in attosecond science, extreme nonlinear and quantum optics, as well as an essential tool for bio and nanoimaging and quantum technology in the second quantum revolution.
In this ERC XSTREAM, the fundamental quantum physics and phase synchronization limits of the upconversion in the X-ray regime have been explored starting with three most promising approaches: I. mid-IR driven X-rays, II. UV driven X-rays, and III. all-optical phase synchronization in frequency and angular momentum mixing. XSTREAM aims to identify the best paths forward for generating bright coherent X-rays at photon energies of 1-10 keV with unprecedented attosecond-to-zeptosecond pulse durations and tunable classical and quantum properties of the light.
This X-ray research is relevant to areas of interest covered by academic, industrial, and defense programs supporting the second quantum revolution of 21st century. In perspective, compact non-diverging hard X-ray laser light would allow for remote delivery of penetrating radiation as a standoff detection where X-ray absorption and fluorescence spectroscopy determines elemental composition. Research on soft - hard X-ray light tools will also support the development of cutting edge nanoelectronics, atomtronics, new generation of magnetic storage key to society, efficient photovoltaics for green energy generation, and advanced bio-sensing and medical imaging. Our ability to directly observe function on the nanoscale with femtosecond or higher temporal resolution, in buried layers of quantum materials or next gen semiconductor chips, is still severely limited and can only be done at large scale facilities. Short and long range electron correlations, disorder, and impurities can govern the function of magnetic, superconducting nanosystems, and batteries. As a result, design rules for future nanosystems that operate at fundamental limits of quantum correlations, energy density, and speed, cannot be formulated until nanoscale structure and dynamics can be visualized and understood.
Inventing a coherent quantum version of the Roentgen X-ray tube that provides an exquisite control of all classical and quantum properties of light is a central part of the short and long term research of XSTREAM. Designer X-ray light with tunable spectral, spatial, temporal shape, and spin-orbital angular momentum, promises to be both a conceptual revolution in attosecond science, extreme nonlinear and quantum optics, as well as an essential tool for bio and nanoimaging and quantum technology in the second quantum revolution.
Mid-IR driven X-rays: The team performed rigorous theoretical effort to determine the feasibility of extending the emission to photon energies of 1-10 keV using a 9 µm driver. This work suggested that the X-ray waveguiding designs and advanced models, pioneered through successfully scaling the phase matched emission to 1.6 keV region with 1-4 µm lasers, can also be extended to the multi-keV range. Quantum diffusion of the accelerated electron wavepackets which reduces the X-ray yield does not terminate the emission. Importantly, the influence of group velocity walk-off effects is less pronounced for multi-cycle compared to few-cycle driving fields.
UV-driven X-rays: Advanced studies showed that intense shorter-wavelength UV fields focused in helium plasma can reach the near-1 keV range before fully ionizing the gas. In this widely unexplored regime, the team demonstrated experimental extension of the conventional and a secondary cutoff to 300 eV, into the soft X-ray water window, in a new quantum optics regime.
Frequency and angular momentum mixing: The combination of UV bi-color fields with circular polarization was explored theoretically to determine the temporal phase matching window and degree of circularity of the X-ray polarization are improved compared to IR bi-color schemes, extending the emission for the first time into the 120 eV soft X-ray region and above.
State-of-the-art Ytterbium laser and X-ray technology developments tremendously assisted the progress.
UV-driven X-rays: Advanced studies showed that intense shorter-wavelength UV fields focused in helium plasma can reach the near-1 keV range before fully ionizing the gas. In this widely unexplored regime, the team demonstrated experimental extension of the conventional and a secondary cutoff to 300 eV, into the soft X-ray water window, in a new quantum optics regime.
Frequency and angular momentum mixing: The combination of UV bi-color fields with circular polarization was explored theoretically to determine the temporal phase matching window and degree of circularity of the X-ray polarization are improved compared to IR bi-color schemes, extending the emission for the first time into the 120 eV soft X-ray region and above.
State-of-the-art Ytterbium laser and X-ray technology developments tremendously assisted the progress.
ERC XSTREAM resulted in a great success discovering two novel quantum regimes of coherent X-ray generation where the design of the light properties is dominated by the dynamics of entangled electrons in a simple helium atomic system. Interestingly, this physics extends beyond the three-step high harmonic model, essentially, representing the first scaling into the X-ray region merging attosecond strong field physics with quantum optics.
In a new regime, using UV fields, entangled electron dynamics are shown to yield a characteristic secondary plateau in the 300 eV region - well beyond the conventional cutoff. This is due to simultaneous double electron recombination where a single higher energy X-ray photon is emitted only in systems with strongly correlated electrons. This experimental discovery paves a way to a sensitive attosecond correlation spectroscopy. Similar physics of harmonics from solids might be able to quantify interactions in phase transition materials of relevance to quantum computing and superconductivity.
In a more extreme regime, focused EUV fields tuned to a resonance of helium are shown to produce very bright X-ray emission. Favorable quantum dynamics of the electron wavepackets, and phase and group velocity matching of the light fields enhance the yield. Furthermore, record-fast attosecond Rabi oscillations are predicted to suppress the depletion of the ground state which otherwise terminates the photon creation.
In a third scientific advance, the team demonstrated a novel technique for producing designer spectral combs of X-ray harmonics for resonance applications using spectrally-tunable UV-visible fields. Self-phase modulation blue-shift and Raman-induced red-shift conveniently tune the combs while maintaining superb coherence, narrow linewidth, and brightness. This light itself is ideal for EUV-driven X-rays at resonance and multidimensional studies of ferromagnetics through resonant coherent diffractive imaging.
All these XSTREAM advances in quantum control over the coherent X-ray emission enable new insights into complex entangled dynamics for applications in quantum nanoscience and technology.
In a new regime, using UV fields, entangled electron dynamics are shown to yield a characteristic secondary plateau in the 300 eV region - well beyond the conventional cutoff. This is due to simultaneous double electron recombination where a single higher energy X-ray photon is emitted only in systems with strongly correlated electrons. This experimental discovery paves a way to a sensitive attosecond correlation spectroscopy. Similar physics of harmonics from solids might be able to quantify interactions in phase transition materials of relevance to quantum computing and superconductivity.
In a more extreme regime, focused EUV fields tuned to a resonance of helium are shown to produce very bright X-ray emission. Favorable quantum dynamics of the electron wavepackets, and phase and group velocity matching of the light fields enhance the yield. Furthermore, record-fast attosecond Rabi oscillations are predicted to suppress the depletion of the ground state which otherwise terminates the photon creation.
In a third scientific advance, the team demonstrated a novel technique for producing designer spectral combs of X-ray harmonics for resonance applications using spectrally-tunable UV-visible fields. Self-phase modulation blue-shift and Raman-induced red-shift conveniently tune the combs while maintaining superb coherence, narrow linewidth, and brightness. This light itself is ideal for EUV-driven X-rays at resonance and multidimensional studies of ferromagnetics through resonant coherent diffractive imaging.
All these XSTREAM advances in quantum control over the coherent X-ray emission enable new insights into complex entangled dynamics for applications in quantum nanoscience and technology.