Useful models of four-wave mixing in Bose–Einstein condensates
| Autor: | Marek Trippenbach, Eryk Infeld |
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| Rok vydání: | 2003 |
| Předmět: | |
| Zdroj: | Journal of Physics B: Atomic, Molecular and Optical Physics. 36:4327-4337 |
| ISSN: | 1361-6455 0953-4075 |
| Popis: | A recent experiment demonstrated four-wave mixing of wavepackets in a sodium Bose–Einstein condensate (Deng et al 1999 Nature 398 218). This was followed by a theoretical and numerical treatment of the experiment (Trippenbach et al 2000 Phys. Rev. A 62 02368). In the experiment, a short period of free expansion of the condensate, after release from the magnetic trap, was followed by a set of two Bragg pulses which created moving wavepackets. These wavepackets, due to nonlinear interaction and under phase-matching conditions, created a new momentum component in a four-wave mixing process. We propose simple mathematical models for this process. Next we suggest that, instead of exactly matching the frequencies as in the abovementioned experiments, we introduce a small mismatch in the energies, and therefore the frequencies Δω. We show that such a small mismatch can compensate for the initial phases that are built on the condensate during free expansion. A physical explanation is offered. This compensation can improve the efficiency of four-wave mixing; in some cases even increasing it by a factor of 2. We also deal with the situation where two strong wavepackets are accompanied by a weak input beam applied as a seed both with and without a mismatch. Here the influence of the mismatch is less obviously beneficial. We also comment on recent work by Ketterle's group (Vogels et al 2002 Phys. Rev. Lett. 89 020401). |
| Databáze: | OpenAIRE |
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