Prof. Dr. Dr. h.c. mult. Gérard Mourou
Nobel Prize in Physics 2018Vita  
Professor at the École Polytechnique, Palaiseau, France and A. D. Moore Distinguished University Professor Emeritus, University of Michigan, USA

Extreme Light for the Benefit of Science and Society

The advent of ultra-intense laser pulses generated by the technique of Chirped Pulse Amplification (CPA) along with the development of high-fluence laser materials has opened an entirely new fields of optics.

A CPA laser exhibits stunning capabilities. It can generate the largest field, the largest pressure, the highest temperature, and accelerating field, making it a universal source of high energy particles and radiations. CPA has been demonstrated in applications as diverse as eye surgery or space cleaning by de-orbiting debris by laser-induced rocket effect.

CPA technology produces a wide range of intensities extending from 10¹⁴ to 10²⁵ W/cm². In the lower part of this range, the intensity regimes of 10¹⁴ to 10¹⁷ the applications include micromachining, that can be performed on material irrelevant of its nature, i.e., ceramic, metal, biological tissue, cornea, etc. Extremely clean cuts of minimal roughness even at the atomic scale are produced. This attractive property led us to applications on ophthalmic procedures like refractive surgery, cataract surgery, corneal transplant, and glaucoma. Today, a million patients a year are benefiting from femtosecond interventions. In science, in the same intensity level, CPA makes possible to reach the attosecond frontier, offering a formidable tool to time resolved fundamental electronic processes.

For intensities >10¹⁸ W/cm² laser-matter interaction becomes strongly dominated by the relativistic character of the electron. In contrast to the nonrelativistic regime, the laser field moves matter more effectively, including motion in the direction of laser propagation, nonlinear modulation, and harmonic generation, leading to high energy particle and radiation production. One of the hallmarks of this regime is Laser Wakefield Acceleration (LWA) where the electromagnetic energy from a laser pulse is transformed into kinetic energy producing accelerating gradient thousand times higher than those obtained in conventional accelerators. The electron beam can in turn produce a copious amount of keV radiation by betatron or Compton scattering.

For intensities at 10²⁵ W/cm² the laser field becomes so large that protons and ions become relativist with GeV energies. The acceleration is directly produced by the light pressure. The source size is very small, and the large acceleration gradient combine to make this source brightness better than any existing.

The coupling of an intense laser field to matter also has implications for the study of the highest energies in astrophysics, such as ultrahigh-energy cosmic rays with energies more than 10²⁰ eV. The intense laser fields can also produce an accelerating field sufficient to simulate general relativistic effects in the laboratory via the equivalence principle like the loss of information in Black Holes.

Many CPA applications offer great benefit to humankind. We discuss a few examples capitalizing on the compactness of the CPA-based source. For instance, the generation of high energy protons and neutrons applied to the treatment of cancer i.e. proton therapy or in nuclear pharmacology where short-lived radionuclides could now be created for therapy or diagnostics near the patient’s bed. High energy protons and protons could be used in a new type of laser architectures for clean and abundant energy productions by nuclear fission or fusion.

On the environmental arena, owing to the efficient generation of high energy neutrons, it is one of our goals to use them to shorten the degree of radiotoxicity of the most dangerous elements, the minor actinide in nuclear waste.

Finally, looking onwards, particle production in "empty" space will remain one of the main scientific objectives of the field. It is the historical path which guided the field to acquire an understanding of fundamental questions on the structure of vacuum, to give us a glimpse on the propagation of light in vacuum and how it defines the mass of all elementary particles.

Finally, a novel laser architecture to reach intensities at the Schwinger level is explored. It is based on the so call the l3 concept where the laser energy is condensed into a l3 spherical volume leading to the highest energy densiy, intensity and the highest ponderomotive pressure. Interacting with a nanometric thin target, the reflected light be in ultrahigh intensity,  single cycle and in the X-ray regime. A Successful transposition would give the field a formidable boost equivalent to the one when maser transitioned into laser, moving from GHz to PHz (Light) frequencies with high intensities.

Prof. Dr. Dr. h.c. mult. Stefan W. Hell
Nobel Prize in Chemistry 2014Vita  
Director, Max Planck Institute for Biophysical Chemistry, Göttingen, and Max Planck Institute for Medical Research, Heidelberg, Germany
Professor at University of Göttingen and Heidelberg University

Optical microscopy: the resolution revolution

Throughout the 20th century it was widely accepted that a light microscope relying on conventional optical lenses cannot tell apart details that are much finer than about half the wavelength of light, or 200-400 nanometers, due to diffraction. However, in the 1990s, the viability to overcome the diffraction barrier was realized and microscopy concepts defined that can resolve fluorescent features down to molecular dimensions. In this short talk, I will discuss the simple yet powerful principles that allow neutralizing the limiting role of diffraction1,2. In a nutshell, feature molecules residing closer than the diffraction barrier are transferred to different (quantum) states, usually a bright fluorescent state and a dark state, so that they become discernible for a brief period of detection. Thus, the resolution-limiting role of diffraction is overcome, and the interior of transparent samples, such as living cells and tissues, can be imaged at the nanoscale.

1. Hell, S.W. Far-Field Optical Nanoscopy. Science 316, 1153-1158 (2007).
2. Hell, S.W. Microscopy and its focal switch. Nature Methods 6, 24-32 (2009).

Prof. Dr. Karsten DanzmannVita  
Director, Max Planck Institute for Gravitational Physics (Albert Einstein Institute) and Director, Institute for Gravitational Physics, Leibniz Universität Hannover, Germany

Gravitational Wave Astronomy: Listening to the sounds of the dark universe!

For thousands of years we have been looking at the universe with our eyes. But most of the universe is dark and will never be observable with electromagnetic waves. Since September 14th , 2015, everything is different:

Gravitational waves were discovered! We have obtained a new sense and finally we can listen to the universe. The first sounds that we heard were from unexpectedly heavy Black Holes. By now, gravitational wave astronomy has become routine. Laser interferometers on the earth are operating at the quantum limit and soon we will be able to listen to low frequencies with detectors in space. With gravitational wave detectors we are listening to the dark side of the universe. And some day we will hear the Big Bang.

Prof. Dr. Reinhard Genzel
Nobel Prize in Physics 2020Vita  
Director, Max Planck Institute for Extraterrestrial Physics (MPE), Garching
Professor of the Graduate School, Physics and Astronomy Departments, University of California, Berkeley, USA

A 40-Year Journey

More than one hundred years ago, Albert Einstein published his Theory of General Relativity (GR). One year later, Karl Schwarzschild solved the GR equations for a non-rotating, spherical mass distribution; if this mass is sufficiently compact, even light cannot escape from within the so-called event horizon, and there is a mass singularity at the center. The theoretical concept of a 'black hole' was born, and was refined in the next decades by work of Penrose, Wheeler, Kerr, Hawking and many others. First indirect evidence for the existence of such black holes in our Universe came from observations of compact X-ray binaries and distant luminous quasars. I will discuss the forty year journey, which my colleagues and I have been undertaking to study the mass distribution in the Center of our Milky Way from ever more precise, long term studies of the motions of gas and stars as test particles of the space time. These studies show the existence of a four million solar mass object, which must be a single massive black hole, beyond any reasonable doubt.