I would like to extend a special thanks to NSF: the entire team of directors, staff, and reviewers for selecting our team’s research proposal for funding.  I am practically in tears of joy.  It is so wonderful that NSF would support my team and undergraduate physics research in general.  Thank you!!

This project, is title “RUI: Atomic Physics with Rapidly Frequency Chirped Laser Light,”, award #   1803837

The proposed research project will study the dynamics of collisions between ultracold atoms in the presence of an external laser field to control what happens during the collision.  These experiments will lead to a greater understanding of understanding of light-assisted collisions and simple chemical reactions.   The major advancement in this project is that the laser is pulsed on the same time and energy scales as the atoms experience during the collision.  In the field of ultrafast lasers similar experiments have been done on much faster time scales and have led to a greater understanding of light-assisted chemical reactions.  Because our atoms are very cold, we are able to conduct these experiments on significantly slower time scales (10^-9 s instead of 10^-14 s).  We have already developed a novel, amplitude and phase modulated laser system that will allow us to conduct these experiments.  This laser system will also allow us to explore methods for completely controlling atomic excitation of atoms.  These techniques have been used to slow atoms (ARP force) and are an interesting avenue toward slowing molecules to a stop.  We propose to use our laser system to increase the level of control of the excitation process.  All of this, makes these experiments an ideal environment for undergraduate physics students to conduct exciting physics (and borderline chemistry) experiments, explore using lasers to control quantum mechanical excited-state collisions, and possibly adding new techniques for generating ultracold molecules.  Engaging students in undergraduate research is a high impact teaching practice and helps to generate elite trained scientists.

Both of the projects are centered on our novel laser system to generate intense rapidly frequency-chirped laser light.  This laser system will be used to explore controlling a variety of dynamics in atomic physics, including coherently controlling ultracold collisions and the study of rapid adiabatic passage (ARP) with shaped laser pulses.  In the first project, we will use trap loss from a magneto-optical trap as a tool to explore coherently controlling trajectories in inelastic light-assisted collisions between atoms.  Recent work has shown that ultracold collisions between two rubidium atoms can be controlled with frequency-chirped laser light; typically the entire process takes about 1 ns.  By tuning the laser frequency and amplitude on that same time scale, we are able to influence the behavior of the collision and the entire process can be coherent.  The initial experiments have shown that this is the case using a 1 GHz in 100 ns laser pulse; however, the experiments weren’t fast enough to observe total control over collisional processes.  We have shown using semi-classical simulations, and propose to demonstrate experimentally, that a modest increase in the chirp-rate leads to full control over collisional processes of this type (1 GHz in 20 ns).  We also propose to show that shaping our laser pulses in a proof-of-principle experiment on the 1 ns time scale can lead to control over collisions in a novel way.   In the second project, we will explore using shaped frequency-chirped laser light as a means to accelerate atomic gases.  We will do this by using a pair of counter propagating frequency-chirped pulses delayed by much less than the lifetime of the transition.  We will be able to work with a Doppler broadened gas because the range of our chirp is large and Rb is heavy. Successful developments on this project may increase the likelihood that coherent processes will be used to slow molecular beams (SrF, CaF, etc), for cold and ultracold molecule experiments.