On-Chip Laser Beam Delivery for Integrated Ion Traps

In this paper we propose a micro-optical beam delivery system for integrated ion traps with anodic bonded BK7 glass including femtosecond-laser written waveguides. Focusing the light at the ion position reduces the beam waist and increases the light intensity. To this end, we position a 300 µm micro-ball lens and actively align it using a custom-built multi-axis optical assembly system. We obtain a 36-fold improvement of intensity at the focus, as compared to the waveguide alone. Beam waist measurements and wave-optical simulations indicate a diffraction limited focus.