TECHNICAL ACTIVITIES 1998 - NISTIR 6268

Four-wave Mixing of Matter Waves. This figure shows the predictions of a numerical simulation of four-wave mixing of matter waves derived from a Bose-Einstein condensate (BEC) of sodium atoms. This is an example of nonlinear atom optics. The process is analogous to four-wave mixing in ordinary nonlinear optics, by which three light waves are mixed to generate a new light wave. The left side of the figure shows an initial BEC wavepacket. Two light pulses use Bragg scattering to produce BEC traveling waves with recoil momenta directed as indicated. After the light pulses, there are wavepackets with three momenta present: the initial BEC with zero momentum, and the two new wavepackets moving in the directions indicated. Nonlinear mixing among the three matter-wavepackets produces a new matter-wavepacket not initially present with a fourth momentum. Energy and momentum are conserved in this process. The three fast moving matter-wavepackets separate after a short time. This is indicated on the right side of the figure, which shows the four wavepackets, including the new one produced by four-wave mixing. The simulations were carried out by integrating the time-dependent nonlinear Schrödinger equation which characterizes a zero temperature BEC. The predictions of the theory have been verified by a recent experiment by the NIST Laser Cooling Group.

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TECHNICAL ACTIVITIES 1998 - Contents

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