European Research Council Starting Grant xstream: X-Ray – waveforms at the Space-Time Resolution Extreme for Atomic-scale Movies
Coherent X-Ray Light for the Second Quantum Revolution
Nonlinear and extreme-nonlinear optics revolutionized the ability to create non-diverging, coherent beams with tunable spectral and temporal properties and spin and orbital angular momentum, particularly in the electromagnetic spectral regions where lasers based on conventional population inversion are not practical. New breakthroughs in attosecond science and extreme nonlinear optics promise a similar revolution in the X-ray regime using novel laboratory-scale ultrafast lasers.
In the European Research Council project XSTREAM, the fundamental atomic, phase matching, and group velocity matching limits of the process of high-order harmonic generation in the multi-keV X-ray regime will be explored using some of the most promising quantum design approaches in extreme nonlinear optics: X-rays driven by mid-infrared lasers, X-rays driven by ultraviolet lasers, and X-rays with tunable angular momentum using frequency and polarization mixing of ultrafast driving laser pulses. The knowledge gained in this ERC project is expected identify the best quantum designs moving forward to generate bright coherent X-ray beams on a tabletop at photon energies of 1-10 keV and greater with unprecedented attosecond-to-zeptosecond (10-18 – 10-21 seconds) spectral bandwidths and tunable angular momentum state. The development of high-energy high-power driving lasers based on scalable Yb-platforms at kHz repetition rate and also over extended wavelength range under XSTREAM is essential for investigating the limits of high harmonic generation, as well as for future applications.
This ERC research project is very relevant to several areas of interest, covering academic, industrial, and defense programs. Generating bright fully coherent light in the soft and hard X-ray region of the spectrum will support the development of cutting-edge nano-electronics and integrated circuits, new generation data storage devices key to the industry and academia, novel lightweight photovoltaics for energy generation, and advanced bio-sensing and medical imaging with unprecedented spatio-temporal resolution. This unique light will assist in directly observing function through 5 dimensional imaging - on the nanoscale with femtosecond or higher temporal resolution, and with effective 5th dimension of elemental and chemical specificity. In materials, heterogeneity is frequently a prerequisite for emergent behavior. At the same time, long-range correlations, hot spots, disorder, imperfect interfaces, and impurities can dominate the properties of nano-systems – in magnetics, superconducting materials, photovoltaics, batteries, etc. Design rules for future nano-systems that operate at fundamental limits of density, efficiency, and speed can be formulated as nanoscale structure and dynamics in heterogeneous systems are captured and understood using the XSTREAM novel light tools. In perspective, compact, well-directed light beams of laser-like hard X-rays would also allow for remote delivery of a beam of highly penetrating X-ray radiation that can be used for standoff detection.
Inventing a fully spatially and temporally coherent version of the Roentgen X-ray tube, which also provides exquisite control of all classical and quantum properties of the generated X-ray light, is a central part of the short and long-term research of XSTREAM. A versatile light source with tunable spectral, spatial, and temporal shape, and angular momentum, promises to be both a conceptual revolution in attosecond science and extreme nonlinear optics, as well as an essential tool for the Second Quantum Revolution in the 21st century.