Ions on a needle´s tip - Traps with enhanced optical and physical access

A novel radio-frequency (rf) ion trap geometry that reduces the solid angle obstructed by trap electrodes to a minimum. Since access and proper ion confinement are inherently opposing goals, we realized three different traps with access ranging from 71% to 96% of 4pi to characterize the trade-offs. Fabrication, characterization, as well as promising applications of similar traps in quantum optics and field sensing are discussed. The trap geometry consists of concentric electrode rings, similar to planar Penning traps or rf-trap arrays, but extends into the third dimension and thus gains optical access from below the common electrode plane.