In 1905, Einstein used the idea of light quantization to explain the photoelectric effect.Since light came in discrete bundles whose magnitude was

Robert Lafon, Lou DiMauro, Brian Sheehy, Mark Widmer

determined by color, weak red photons could not liberate electrons from a surface regardless of the brightness of the light. However,shorter wavelength blue light could easily do the job as long as the photon energy exceeded the electron's binding energy. Some sixty years later, the idea of probing matter with light entered into a new regime with the invention of the laser. Extremely high intensities could be created by tightly focusing a short pulse of laser light. Now, instead of being restricted to only one chunk of light at a time, an atom could absorb multiple photons simultaneously. As a result, weak photons could conspire together to strip electrons from an atom. This broad area of physics is called nonlinear optics.
In our laboratory, we study various facets of nonlinear phenomena and ultra-fast optical physics. Our interest in nonlinear physics goes beyond spectroscopy and towards a regime of intense laser-atom interaction. Simply stated, laser fields are used that have a peak electric field strength equivalent to the fields binding electrons in the atom. The physics of this interaction is rich in new phenomena having both fundamental and applied interest. The laser peak intensities used for these studies ranges from 1012 - 1016 W/cm2 and it all fits on a tabletop source! The duration of the light pulse is only 10-14 seconds (10 femtoseconds), less than the transit time of light across the width of a human hair! In fact, shorter than the time that matter vibrates.
The tools in our laboratory are on the very forefront of ultra-fast physics. Our studies are aimed at finding new ways to exploit the light-matter interaction and actively controlling its outcome. Ongoing studies explore the production of tabletop sources of coherent hyper-x-rays and light pulses on the atomic time-scale (attoseconds = 10-18 seconds).
 

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