Bichromatic Slowing of Metastable Helium

Date of Completion

January 2012


Physics, Molecular|Physics, Atomic




This dissertation describes experiments to develop and realize an atomic decelerator (or "slower") for metastable helium using the optical bichromatic force (BCF). The research comprises two subtopics—using the bichromatic force at very large detunings, and developing a chirped BCF slower. There is experimental evidence that as bichromatic detunings approach 300 times the natural linewidth, the BCF breaks down. The likely cause is that large Doppler frequency shifts from the rapid deceleration result in cumulative dephasing of the Rabi cycling of the atom. To circumvent this and other problems, we have developed an alternate slower design in which the center frequency of a narrow BCF force profile is swept to stay resonant with the atoms as they are slowed. Results from a first-generation experiment show atomic slowing larger than has previously been possible with a large fixed detuning. Additional refinements will allow the design to be scaled up enough to slow metastable helium atoms to magneto-optical trapping velocities, with a brightness comparable to modern Zeeman slowers, but in a much smaller and considerably simplified configuration. I close with a discussion of prospects for direct laser slowing of molecules using the BCF. An estimate for CaF shows that a buffer-gas cooled beam can be slowed to rest, and proof-of-principle experiments in atomic helium yield very promising results. ^