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Coherent Control with Shaped Ultrafast Laser Pulses

Shitong Zhao
Augustana University
Physics, Chemistry & Math Major
Mentored by Dr. Itzik Ben-Itzhak and Graduate Research Assistant, Bethany Jochim

As one of the greatest 20th century advances in physics, the atom/molecule is identified as the basic building block of matter [1]. Controlling the inner workings of atoms and molecules (e.g. chemical reactions) has been a long-standing endeavor of the scientific community. Traditionally, this task has been performed by varying the atomic/molecular environment such as temperature, pressure, concentration, etc. However, the extent to which the atomic/molecular dynamics can be controlled by this method is limited. Recently, along with the invention and advancements of laser technology, governing the atomic/molecular dynamics with higher degrees of freedom has been made feasible. This is typically accomplished by shining ultrafast laser light (laser pulses with time durations of femtoseconds) on the molecules being studied and varying the parameters that characterize the laser light, such as intensity, wavelength, and time duration of the laser light [2] (See Figure 1).

Often, a pulse shaper is needed to reshape the ultrafast laser pulses, which in effect influences the properties of the laser light mentioned above (See Figure 2). The spatial light modulator (SLM) is a common pulse shaper that has been employed in achieving control over atomic/molecular dynamics with success (for example, see [3-4]). Though a powerful pulse shaping tool, the SLM requires highly accurate setup and testing. The primary goal of my project is to assemble an SLM into the laser beam path, test it, and make sure that it functions properly (See Figure 3 for our alignment of related optics). After the alignment and testing of the SLM, it will be utilized in a larger project that aims at controlling the yield of a desired product of a chemical reaction, such as the ones studied in [5].

Figure 1

Fig. 1: Shaped ultrafast laser pulses incident on molecules to achieve molecular selectivity. Figure from Trebino slides [2].

Figure 2

Fig. 2: A pulse shaper producing an output pulse whose shape is different from that of the original pulse. Figure from Trebino slides [2].

Figure 3

Fig. 3: A photo of our experimental setup.

 

Acknowledgments

In addition to my mentor, all the AMO graduate student assistants, and JRM staff, I would also like to thank Eric Wells, who is my physics professor at Augustana University.

References

1. "Controlling the Quantum World: The Science of Atoms, Molecules, and Photons," written by the AMO 2010 Committee, P.H. Bucksbaum and R. Eisenstein, co-chairs. National Academies Press, Washington D.C., 2007.

2. R. Trebino, "Ultrafast Optics Course," http://www.frog.gatech.edu/talks.html, July 31, 2017.

3. Robert J. Levis, Getahun M. Menkir and Herschel Rabitz, Science292 (5517), 2001.

4. G. Gerber et al., Science282 (5390), 1998.

5. E. Wells et al., Nat. Comm.4 (2895), 2013. 

Final Presentation

National Science Foundation

This program is funded by the National Science Foundation through grant number PHY-1461251. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.