High efficiency excitation of cylindrical optical near fields for atom guidance

We describe coupling of light beams to a micron-sized hollow fiber used fur atom guidance. In particular, we deal with an annular light beam produced by means of a hollow fiber. The coupling efficiency of the annular light be am to the LP01 mode with a cylindrical optical near field is compared to th at of a Gaussian light beam. Next, we examine optical pumping and healing e ffects of the light beams on atoms before they enter the hollow fiber. From these results, we find that the use of the annular light beam is more adva ntageous than the use of the Gaussian light beam for both high efficiency e xcitation of the LP01 mode and suppression of the preinteraction between at oms and leaked light at the entrance. The spatial intensity distribution of an annular light beam is measured with a protrusion-type fiber probe. This method is useful for observing fine structures of light beams with high sp atial resolution.