Attosecond coherent control of free-electron wave functions using semi-infinite light fields

Light–electron interaction is the seminal ingredient in free-electron lasers and dynamical investigation of matter. Pushing the coherent control of electrons by light to the attosecond timescale and below would enable unprecedented applications in quantum circuits and exploration of electronic motions and nuclear phenomena. Here we demonstrate attosecond coherent manipulation of a free-electron wave function, and show that it can be pushed down to the zeptosecond regime. We make a relativistic single-electron wavepacket interact in free-space with a semi-infinite light field generated by two light pulses reflected from a mirror and delayed by fractions of the optical cycle. The amplitude and phase of the resulting electron–state coherent oscillations are mapped in energy-momentum space via momentum-resolved ultrafast electron spectroscopy. The experimental results are in full agreement with our analytical theory, which predicts access to the zeptosecond timescale by adopting semi-infinite X-ray pulses.

Spatio-temporal shaping of a free-electron wave function via coherent light-electron interaction

Fabrizio Carbone, Ivan Madan, Giovanni Maria Vanacore

The past decade has witnessed a quantum revolution in the field of computation, communication and materials investigation. A similar revolution is also occurring for free-electron based techniques, where the classical treatment of a free electron as a point particle is being surpassed toward a deeper exploitation of its quantum nature. Adopting familiar concepts from quantum optics, several groups have demonstrated temporal and spatial shaping of a free-electron wave function, developing theoretical descriptions of light-modulated states, as well as predicting and confirming fascinating phenomena as attosecond self-compression and orbital angular momentum transfer from light to electrons. In this review, we revisit the milestones of this development and the several methods adopted for imprinting a time-varying phase modulation on an electron wave function using properly synthesized ultrafast light fields, making the electron an exquisitely selective probe of out-of-equilibrium phenomena in individual atomic/nanoscale systems. We discuss both longitudinal and transverse phase manipulation of free-electrons, where coherent quantized exchanges of energy, linear momentum and orbital angular momentum mediating the electron-light coupling are key in determining their spatio-temporal redistribution. Spatio-temporal phase shaping of matter waves provides new routes toward image-resolution enhancement, selective probing, dynamic control of materials, new quantum information methods, and exploration of electronic motions and nuclear phenomena. Emerging as a new field, electron wave function shaping allows adopting familiar quantum optics concepts in composite-particle experiments and paves the way for atomic, ionic and nuclear wave function engineering with perspective applications in atomic interferometry and direct control of nuclear processes.

SPRINGERNATURE2020

Scanning near-field infrared microscopy and spectromicroscopy applied to nano-systems and cells

Dusan Vobornik

This thesis further explores the possibilities of scanning near-field optical microscopy (SNOM) in both materials and life sciences. Two experimental SNOM setups were developed: one designed for infrared spectroscopy applications and the other for the imaging of fluorescently labeled samples. The results of the experiments that were conducted with both setups are presented and analyzed in this thesis. Diffraction limits the resolution of lens-based microscopes to a value close to that of the wavelength of the light that is used to illuminate the samples. SNOM instruments overcome this limit by probing the near-field light — the light that remains within close vicinity of the sample and decays exponentially away from it. The SNOM concept and instrumental design are described. A comparison of SNOM with other novel microscopies (electron, atomic force, and scanning tunneling microscopies) outlines the main advantages of SNOM — the sole optical microscopy technique with a nanometer resolution. Aperture-based infrared SNOM (IR-SNOM), performed in the spectroscopic mode using the Vanderbilt University free electron laser, recently started delivering spatially resolved information on the distribution of chemical species and on other laterally fluctuating properties. The IR-SNOM combines the IR spectroscopy's chemical specificity and the SNOM's high optical and topographical resolutions. The IR-SNOM experimental setup is described in detail and results from the study of cells, boron nitride and lithium fluoride thin films are presented and analyzed. They demonstrate the great potential of this new technique. An overview of the development of IR-SNOM, as well as a consideration of its future possibilities are presented. The newly built SNOM instrument at EPFL was used for experiments that are complementary to the aforementioned IR-SNOM experiments. Specifically, the new SNOM enabled the study of fluorescently marked samples. Images of fluorescently labeled cells and carbon nanotubes are presented and analyzed. The results further demonstrate the exciting possibilities of SNOM.

EPFL2005

Scanning near-field infrared microscopy and spectromicroscopy applied to nano-systems and cells

Dusan Vobornik

EPFL2005

Spatio-temporal shaping of a free-electron wave function via coherent light-electron interaction

Fabrizio Carbone, Ivan Madan, Giovanni Maria Vanacore

SPRINGERNATURE2020