  Optical bottle beams can be used to trap atoms and small low-index particles.
We introduce a figure of merit for optical bottle beams, specifically in the
context of optical traps, and use it to compare optical bottle-beam traps
obtained by three different methods. Using this figure of merit and an
optimization algorithm, we identified optical bottle-beam traps based on a
Gaussian beam illuminating a metasurface that are superior in terms of power
efficiency than existing approaches. We numerically demonstrate a silicon
metasurface for creating an optical bottle-beam trap.
