Ultrafast Quantum Optics group. New control over electrons with laser light and other means.
Dr. P. Hommelhoff, Experimental Physics
It is now nearly a decade since the invention of the laser frequency comb (Nobel Prize to T.W. Hänsch in 2005). This technique enables controlling the optical electric field of laser pulses, as opposed to just controlling the parameters of the laser pulse envelope. A wealth of phenomena can now be explored which had been not accessible before, such as phase controlled emission of electrons from sharp field emission tips. Phase control only makes a difference in the regime in which the electrons follow the laser electric field, which means that the electrons have to leave the tip via a tunnel process. Not only has this process not been observed before, also the properties are highly interesting. Since the electron tunnel current resolves the electric field and is highly non-linear in it, emission durations of about a quarter of a laser period are expected. For a near-infrared laser pulse shorter than 8 fsec, a single 700 attosecond long pulse is expected. Also, electron pulse shaping with the help of the phase control of the driving laser is conceivable.
But not only new emission regimes can be explored; laser phase control will also allow acceleration of electron directly with laser light. We are working towards a low-energy proof-of-concept experiment on this in a collaborative effort with the inventors of this idea, Tomas Plettner and Robert L. Byer of Stanford University.
Besides from exploring and exploiting electron control with the help of phase stable lasers we are currently developing a novel low-energy guiding structure for electrons. This experiment aims at electron interferometry and, once laser emitted electron emission from special tips is well-controlled enough, basic controlled electron-electron interaction experiments might follow.
Along these main topics we develop the laser sources and other tools necessary for the experiments. For example, we have developed a phase-stable single pass laser amplifier that was so powerful that we were able to generate white-light, an extreme non-linear effect, at the full oscillator repetition rate for the first time.
Contribution to IMPRS curriculum:
Lecturer: P. Hommelhoff, T. Hänsch and P. Treutlein (3+1 hours/week)
Light and atoms; laser cooling and applications; magnetic traps for neutral atoms, optical dipole traps, evaporative cooling; Bose- Einstein condensation in atomic gases; quantum statistics; cold collisions; Gross-Pitaevskii equation; loss processes in Bose- Einstein condensates; selected experiments with Bose-Einstein condensates; coherent matter waves; atom lasers; superfluidity; vortices; cold atoms in periodic lattice potentials; strongly correlated quantum gases; superfluid to Mott insulator transition.