Automated motors for optics calibration

Problem. Coupling laser light into a single-mode fiber requires precise mirror alignment. Over time, mirror screws drift, reducing coupling efficiency and necessitating manual realignment. The objective was to automate this recovery process to ensure a stable optical path without constant human intervention.

What we did. We designed a compact 3D-printed box with a photodiode fixed at the top. This photodiode measures the output intensity from the fiber coupled from the opposite side of the box ceiling. Arduino-controlled motors are fixed to the mirror post with a machined metal support. They adjusts the mirror screws to achieve better alignment when the diode’s measured intensity falls below a predetermined threshold. The mechanical system was designed to be compact, minimizing its footprint on an optical table.

Result. Our lab no longer has to worry about the time drift effect of laser power coupled into optical fibers. A significant amount of tedious manual labor has been automated, making the system self-sustaining.

Why it matters. While adjusting mirrors can be tedious but manageable for relatively simple optics experiments, it becomes a major cause of failure in large-scale setups like cold-atom quantum computers. If deployed effectively, this system will enable projects that require the precise alignment of numerous mirrors for extended periods, making them feasible for the first time.