The integration of optics for efficient light delivery and the collection of fluorescence from trapped ions in surface
electrode ion traps is a key component to achieving scalability for quantum information processing. Diffractive optical
elements (DOEs) present a promising approach as compared to bulk optics because of their small physical profile and
their flexibility in tailoring the optical wavefront. The precise alignment of the optics for coupling fluorescence to and
from the ions, however, poses a particular challenge. Excitation and manipulation of the ions requires a high degree of
optical access, significantly restricting the area available for mounting components. The ion traps, DOEs, and other
components are compact, constraining the manipulation of various elements. For efficient fluorescence collection from
the ions the DOE must be have a large numerical aperture (NA), which results in greater sensitivity to misalignment.
The ion traps are sensitive devices, a mechanical approach to alignment such as contacting the trap and using precision
motors to back-off a set distance not only cannot achieve the desired alignment precision, but risks damage to the ion
We have developed a non-contact precision optical alignment technique. We use line foci produced by off-axis linear
Fresnel zone plates (FZPs) projected on alignment targets etched in the top metal layer of the ion trap and demonstrate
micron-level alignment accuracy.