Efficient Photoionization Loading of Ytterbium and Indium Ion Traps

We aim to perform precision optical spectroscopy on narrow transitions of In$^{+}$ and Yb$^{2+}$ to search for possible time variation of fine-structure constant $\alpha $. The high sensitivity of a transition frequency in Yb$^{2+}$ to $\dot {\alpha }$ and its insensitivity to external fields make it one of the best systems to test the time variation of fine-structure constant. In this report, we present a simple and efficient method to load a Paul trap with In$^{+}$ and Yb$^{+}$ ions. Resonant lasers from blue laser diodes at 410 nm and 399 nm are used to excite 5$^{2}$P$_{1/2}$-6$^{2}$S$_{1/2}$ transition of In and 6$^{1}$S$_{0}$-6$^{1}$P$_{1}$ transition of Yb, respectively. A second photon from the same 410 nm laser drives the In atoms into the continuum, while the Yb atoms are excited to high-lying Rydberg states by the same 399 nm laser and then subsequently ionized by the presence of a strong RF field. The progress of laser cooling of single trapped In$^{+ }$and Yb$^{+}$ ions, the proposed method of producing doubly-ionized Yb$^{2+}$ ions, and our approach using a frequency-comb laser for direct spectroscopy of clock transitions will be discussed. This work is supported by Los Alamos National Laboratory LDRD.