A microfabricated phase Fresnel lens was used to image ytterbium ions trapped
in a radio frequency Paul trap. The ions were laser cooled close to the Doppler
limit on the 369.5 nm transition, reducing the ion motion so that each ion
formed a near point source. By detecting the ion fluorescence on the same
transition, near diffraction limited imaging with spot sizes of below 440 nm
(FWHM) was achieved. This is the first demonstration of imaging trapped ions
with a resolution on the order of the transition wavelength.Comment: 8 pages, 3 figure
