Using a simple model, we calculate the heating rates arising from laser intensity noise and beam-pointing fluctuations in far-off resonance optical traps. Intensity noise causes exponential heating, while beam-pointing noise causes heating at a constant rate. The achievement of heating time constants well beyond 10 sec imposes stringent requirements on the laser noise power spectra. Noise spectra are measured for a commercial argonion laser to illustrate the expected time scales.

A Fokker-Planck equation is derived for the energy distribution of atoms in a three-dimensional harmonic trap with fluctuations in the spring constant and the equilibrium position. Using this model, we predict trap lifetimes based on the measurable noise spectra of the fluctuations. The energy distributions evolve into a single eigenmode where the apparent temperature of the distribution remains constant while the population decays as a consequence of the energy input. The method of analysis and the corresponding results are applicable to any optical, magnetic, or ion trap that is approximately harmonic, and offer useful insights into both noise-induced and optical heating processes. ͓S1050-2947͑98͒05211-1͔

We demonstrate an ultrastable CO 2 laser trap that provides tight confinement of neutral atoms with negligible optical scattering and minimal laser-noise-induced heating. Using this method, fermionic 6 Li atoms are stored in a 0.4 mK deep well with a 1͞e trap lifetime of 300 sec, consistent with a background pressure of 10 211 Torr. To our knowledge, this is the longest storage time ever achieved with an all-optical trap, comparable to the best reported magnetic traps. [S0031-9007(99)09193-0] PACS numbers: 32.80.PjOff-resonance optical traps have been explored for many years as an attractive means of tightly confining neutral atoms [1]. Far off resonance optical traps (FORTs) employ large detunings from resonance to achieve low optical heating rates and high density, as well as to enable trapping of multiple atomic spin states in nearly identical potentials [2][3][4][5][6]. For CO 2 laser traps [7], the extremely large detuning from resonance and the very low optical frequency lead to optical scattering rates that are measured in photons per atom per hour. Hence, optical heating is negligible. Such traps are potentially important for the development of new standards and sensors based on spectroscopic methods, for precision measurements such as determination of electric dipole moments in atoms [8], and for fundamental studies of cold, weakly interacting atomic or molecular vapors.However, all-optical atom traps have suffered from unexplained heating mechanisms which limit the minimum attainable temperatures and the maximum storage times in an ultrahigh vacuum [4,9,10]. Recently, we have shown that to achieve long storage times in all-optical traps that are not limited by optical heating rates, heating arising from laser intensity noise and beam pointing noise must be stringently controlled [11,12]. Properly designed CO 2 lasers are powerful and extremely stable in both frequency and intensity [13,14], resulting in laser-noiseinduced heating times that are measured in hours. Hence, in an ultrahigh vacuum (UHV) environment, where loss and heating arising from background gas collisions are minimized [15,16], extremely long storage times should be obtainable using ultrastable CO 2 laser traps.In this Letter, we report storage of 6 Li fermions in an ultrastable CO 2 laser trap. Trap 1͞e lifetimes of 300 sec are obtained, consistent with a background pressure of 10 211 Torr. This constitutes the first experimental proof of principle that extremely long storage times can be achieved in all-optical traps. Since arbitrary hyperfine states can be trapped, this system will enable exploration of s-wave scattering in a weakly interacting Fermi gas.The well depth for a focused CO 2 laser trap is determined by the induced dipole potential U 2a gĒ 2 ͞2, where a g is, to a good approximation, the ground state static polarizability [7], andĒ 2 is the time average of the square of the laser field. In terms of the maximum laser intensity I for the Gaussian CO 2 laser beam, the ground state well depth U 0 in Hz isIn our experiments, a...

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