A Fully Fiber-Integrated Ion Trap for Portable Optical Atomic Clocks

We present a novel, single-ion trap with integrated optical fibers directly embedded within the trap structure to deliver laser light as well as collect the ion's fluorescence. This eliminates the need for optical windows. We characterise the system's performance and measure signal-to-background ratios in the ion's fluorescence on the order of 50, which allows us to perform state readout with a fidelity over 99% in 600 μs. We test the system's resilience to thermal variations in the range between 22°C and 53°C, and the system's vibration resilience at 34 Hz and 300 Hz and find no effect on its performance. The combination of compactness and robustness of our fiber-coupled trap makes it well suited for applications in, as well as outside, research laboratory environments and in particular for highly compact portable optical atomic clocks. While our system is designed for trapping ⁴⁰Ca⁺ ions the fundamental design principles can be applied to other ion species.