Integrated Diffractive Optics for Surface Ion Traps

Photonic interconnects are a bottleneck to achieving large-scale trapped ion quantum computing. We have modified a Georgia Tech Research Institute microwave chip trap by using e-beam lithography to write reflective diffractive collimating optics (80 $\mu$m x 127 $\mu$m, f=58.6 $\mu$m, $\lambda$=369.5nm) on the center electrode. The optics have an NA of 0.55 x 0.73, capturing 13.2% of the solid angle. To evaluate the optics 174Yb+ was loaded by isotope selective photo-ionization from a thermal oven and then shuttled to imaging sites. Near diffraction limited sub-wavelength ion images were obtained with an observed spot sized FWHM of 338 nm x 268 nm vs. a diffraction limit of 336 nm x 257 nm. The total photon collection efficiency was measured to be 5.2±1.2%. Coupling into a single mode fiber of up to 2.0±0.6% was observed, limited by mismatch in the coupling optics. Image mode quality indicates coupling up to ~4% may be possible.