Nonlinear Optics, Quantum Optics and Ultrafast Phenomena with X-Rays from Synchrotrons and Free-Electron Lasers – Bernhard Adams

Date: Thu. March 28th, 2002, 4:15 pm-5:15 pm
Location: Rockefeller 301

In the last few decades, x-ray physics has made tremendous advances, and the development is expected to accelerate with the advent of x-ray free-electron lasers (XFEL). An XFEL will emit transversely fully coherent x-ray pulses of ca. 100fs duration at a peak power of 10¹⁰W . The LCLS project at Stanford and TESLA at DESY, Hamburg are in the advanced stages of planning and scientific cases were developed. A few examples from the fields of nonlinear optics, quantum optics, and the study of ultrafast phenomena will be presented in the talk and results from some experiments in these fields that have recently been done at synchrotron radiation facilities will also be mentioned.

• Study of the elementary processes of chemistry on the femtosecond level, using laser-pump, x-ray probe techniques: X-ray spectroscopy and diffraction, showing changes in the electronic configuration after laser excitation. Results from a recent laser-pump, x-ray probe spectroscopic experiment, done at the Advanced Photon Source, will be shown.
• Element- and ionization state specific imaging of laser-induced plasmas on femtosecond timescales.
• Atom interferometry, using x-ray standing waves as beamsplitters. The large photon momentum helps to achieve macroscopic separation of the atom beams.
• Spontaneous parametric down conversion (PDC) of x-rays. Photons can decay spontaneously into pairs of highly correlated photons due to nonlinear optical mixing with vacuum fluctuations. It is well known in the visible light regime and has been demonstrated for x-rays in several experiments. PDC of visible light is commonly used in experiments to demonstrate the nonlocality of quantum physics. The probing of pure quantum states depends on the detector quantum efficiency, which can be close to 100% with x-rays. An XFEL will be necessary to provide a large enough event rate and coherence.
• Optically triggered devices for coherent manipulation and detection of femtosecond x-rays: Diffraction from laser-induced structural changes and laser-assisited x-ray absorption. Although this field will fully open up only when an XFEL is available, active research has been done in the last few years within the limited current capabilities.