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Register a new userTime-delayed intensity-interferometry of the emission from ultracold atoms in a steady-state magneto-optical trap
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Added by
Hema Ramachandran Dr.
Publication date
2015
fields
Physics
and research's language is
English
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An accurate measurement of the bunching of photons in the fluorescent emission from an ultracold ensemble of thermal 87Rb atoms in a steady-state magneto-optical trap is presented. Time-delayed-intensity-interferometry (TDII) performed with a 5-nanosecond time resolution yielded a second-order intensity correlation function that has the ideal value of 2 at zero delay, and that shows coherent Rabi oscillations of upto 5 full periods - much longer than the spontaneous emission lifetime of the excited state of Rb. The oscillations are damped out by ~150ns, and thereafter, as expected from a thermal source, an exponential decay is observed, enabling the determination of the temperature of the atomic ensemble. Values so obtained compare well with those determined by standard techniques. TDII thus enables a quantitative study of the coherent and incoherent dynamics, even of a large thermal ensemble of atomic emitters.
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A steady-state magneto-optical trap (MOT) of fermionic strontium atoms operating on the 7.5 kHz-wide ${^1mathrm{S}_0} - {^3mathrm{P}_1}$ transition is demonstrated. This MOT features $8.4 times 10^{7}$ atoms, a loading rate of $1.3times 10^{7}$atoms/s, and an average temperature of 12 $mu$K. These parameters make it well suited to serve as a source of atoms for continuous-wave superradiant lasers operating on strontiums mHz-wide clock transition. Such lasers have only been demonstrated using pulsed Sr sources, limiting their range of applications. Our MOT makes an important step toward continuous operation of these devices, paving the way for continuous-wave active optical clocks.
We investigated non-equilibrium atomic dynamics in a moving optical lattice via observation of atomic resonance fluorescence spectrum. A three-dimensional optical lattice was generated in a phase-stabilized magneto-optical trap (MOT) and the lattice was made to move by introducing a detuning between the counter-propagating trap lasers. A non-equilibrium steady states (NESSs) of atoms was then established in the hybrid of the moving optical lattice and the surrounding MOT. A part of atoms were localized and transported in the moving optical lattice and the rest were not localized in the lattice while trapped as a cold gas in the MOT. These motional states coexisted with continuous transition between them. As the speed of the lattice increased, the population of the non-localized state increased in a stepwise fashion due to the existence of bound states at the local minima of the lattice potential. A deterministic rate-equation model for atomic populations in those motional states was introduced in order to explain the experimental results. The model calculations then well reproduced the key features of the experimental observations, confirming the existence of an NESS in the cold atom system.
We demonstrate a continuously loaded $^{88}mathrm{Sr}$ magneto-optical trap (MOT) with a steady-state phase-space density of $1.3(2) times 10^{-3}$. This is two orders of magnitude higher than reported in previous steady-state MOTs. Our approach is to flow atoms through a series of spatially separated laser cooling stages before capturing them in a MOT operated on the 7.4-kHz linewidth Sr intercombination line using a hybrid slower+MOT configuration. We also demonstrate producing a Bose-Einstein condensate at the MOT location, despite the presence of laser cooling light on resonance with the 30-MHz linewidth transition used to initially slow atoms in a separate chamber. Our steady-state high phase-space density MOT is an excellent starting point for a continuous atom laser and dead-time free atom interferometers or clocks.
We investigate theoretically the application of Sawtooth Wave Adiabatic Passage (SWAP) in a 1D magneto-optical trap (MOT). As opposed to related methods that have been previously discussed, our approach utilizes repeated cycles of stimulated absorption and emission processes to achieve both trapping and cooling, thereby reducing the adverse effects that arise from photon scattering. Specifically, we demonstrate this methods ability to cool, slow, and trap particles with fewer spontaneously emitted photons, higher forces and in less time when compared to a traditional MOT scheme that utilizes the same narrow linewidth transition. We calculate the phase space compression that is achievable and characterize the resulting system equilibrium cloud size and temperature.
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