We characterize a Fabry-Perot microwave cavity designed for trapping atoms
and molecules at the antinode of a microwave field. The cavity is fed from a
waveguide through a small coupling hole. Focussing on the compact resonant
modes of the cavity, we measure how the electric field profile, the cavity
quality factor, and the coupling efficiency, depend on the radius of the
coupling hole. We measure how the quality factor depends on the temperature of
the mirrors in the range from 77 to 293K. The presence of the coupling hole
slightly changes the profile of the mode, leading to increased diffraction
losses around the edges of the mirrors and a small reduction in quality factor.
We find the hole size that maximizes the intra-cavity electric field. We
develop an analytical theory of the aperture-coupled cavity that agrees well
with our measurements, with small deviations due to enhanced diffraction
losses. We find excellent agreement between our measurements and
finite-difference time-domain simulations of the cavity.Comment: 16 pages, 8 figure
