Browsing by Author "Luo, Henry"
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Item Second-Harmonic Generation for Narrow-Line Cooling of 7Li(2017-02-14) Luo, Henry; Hulet, Randall GLaser cooling of lithium atoms is usually performed on the 2S1/2 to 2P3/2 transition at 671 nm. The Doppler temperature of this transition, which is the limit temperature of laser cooling, is 140 µK. The 2S1/2 to 3P3/2 transition at 323 nm has a Doppler temperature 7 times smaller than that of the 671 nm transition. With the 323 nm transition, it is possible to reach a temperature low enough for an all-optical production of a Bose-Einstein condensate. The 323 nm light is produced by second-harmonic generation (SHG). We present our design of the laser system that generates light at 646 nm and the frequency-doubling cavity for SHG. The laser frequency is stabilized by a Fabry-Perot cavity and an Iodine transition.Item Solitons and Breathers in Bose-Einstein Condensates(2021-04-30) Luo, Henry; Hulet, Randall G.Solitons are non-dispersive wave packets that balance the wave dispersion with a focusing nonlinearity. They maintain their shape and velocity after collisions with other solitons, owing to the integrability of the underlying nonlinear partial differential equations. They appear in various physical systems, such as water waves, light waves in optical fiber, and matter waves. In our laboratory, we study solitons and their interactions in a Bose-Einstein condensate with an attractive nonlinearity, trapped in a quasi-one-dimensional waveguide. We investigate the collisions of a pair of solitons and explore the relative phase implications on the boundary of integrability. We study soliton train formation with the quench of the nonlinearity strength, and interactions between neighboring solitons in the train. We form a composite soliton, known as a breather, where multiple solitons overlap and the wavefunction ``breathes'' in time. We also explore the response of an elongated condensate to an external modulation of the nonlinearity. These experiments characterize the mean-field descriptions of solitons and Bose-Einstein condensates and explore the boundaries between the mean-field theory and quantum many-body theory.