Near-diffraction limited direct imaging of patterned light fields for trapping (Conference Presentation)

Abstract

Configurable trapping potentials are of great interest in cold atom physics, as they enable production of dynamical highly flexible fields that exhibit unprecedented stability and diverse geometries. Direct imaging can be used to create large area trapping potentials but is often overlooked due to its inability to correct for wavefront aberrations of the optical system [1]. This need not be a major disadvantage for a well-corrected optical system and brings advantages including the simplicity and speed of direct imaging. This is in contrast to the Fourier plane method which requires complex calculations to generate proper holograms and suffers from phase defects and speckle. For applications in cold atom trapping, these effects are especially detrimental as the atoms are sensitive to perturbations at the ~1% level of the optical potential. Our approach uses off-the-shelf lenses and microscope objectives and is able to achieve 630(10) nm full width half maximum (FWHM) patterning resolution using a 0.45 NA objective, within 5% of the diffraction limit of the system, while imaging through 1.25 mm of glass. The light field patterning is done using a digital micromirror device (DMD) which allows for dynamic trapping potentials due to its ability to store 13,889 frames and its 22 kHz full frame refresh rate. We use this method to pattern planar potentials for the purpose of cold atom experiments and have found that for atoms, which tend to respond relatively slowly to perturbations, it is possible to combine half-toning and time averaging to produce grey scale patterns, additionally allowing for pattern correction [2]. [1] P. C. Mogensen and J. Gluckstad, Optics Communications 175, 75–81 (2000). [2] G. Gauthier, I. Lenton, N. McKay Parry, M. Baker, M. J. Davis, H. Rubinsztein-Dunlop, and T. W. Neely, arXiv preprint arXiv:1605.04928 (2016).