Strong Field Physics

Argon momentum spectrum

The interaction of an isolated atom with an intense electromagnetic field is the basis for one of the forefront problems in atomic, molecular and optical physics.

The ability to couple large amounts of energy into an atom by the absorption of many photons posed many intriguing questions and has led to many new discoveries such as above-threshold ionization, high-harmonic generation, multiple ionization and adiabatic stabilization.

With the intention of extending our basic knowledge of Strong-Field physics, our group is pursuing research into single atom response to an ultra-fast burst of electromagnetic radiation that will not only provide basic tests of scaling laws and theory but also initiate some novel experimental investigations in strong field physics.

Subtopics in strong field physics

One of our objectives is to broaden the scope of experimental investigations by utilizing the wavelength scaling of the strong field interaction at low frequency (hν << Ip, where Ip is the binding energy).

Various aspects of the strong field interaction have an implicit wavelength dependence that is a crucial scaling parameter and has not been explored or exploited in a systematic fashion.

Addressing these scaling laws with novel ionization experiments using few-cycle mid-infrared (2 µm and 4 µm) pulses is crucial since it tests the very foundations of all our understanding of the intense laser-atom interaction.

Using principles of strong field tunnel ionization and Keldysh scaling, we are working to:

  • Initiate a global investigation of fundamental scaling laws
  • Enable high-sensitivity electron interferometry for studying electron dynamics
  • Significantly increase the number of experimentally accessible atomic systems
  • Examine strong field interactions for prepared coherent states
  • And initiate investigations on field enhanced electron emission from nanostructures

A second thrust of our research is into understanding and connecting the behavior of atoms in intense x-ray fields with the more studied optical regime.

Scaling laws suggest that atomic behavior at x-ray frequencies will be very different from that in the optical regime.

Using the unprecedented x-ray intensities available at the Linear Coherent Light Source (LCLS), at the SLAC National Laboratory, we are exploring the strong-field high frequency regime to test these scaling laws.

For more information on research going on at the LCLS, please visit