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Published on: May 3, 2015
A compact and open-source microcontroller-based rapid auto-alignment system
Yanda Geng1, Alan Tsidilkovski2, Kevin Weber1
1Joint Quantum Institute, National Institute of Standards and Technology and the University of Maryland, College Park, Maryland 20742, USA.
Abstract:
Maintaining stable and precise alignment of a laser beam is crucial in many optical setups. In this work, we present a microcontroller-based rapid auto-alignment system that detects and corrects for drifts in a laser beam trajectory using a pair of two-dimensional duo-lateral position sensing detectors (PSDs) and a pair of mirror mounts with piezoelectric actuators. We develop hardware and software for interfacing with the PSDs and for controlling the motion of the piezoelectric mirror mounts. Our auto-alignment strategy-implemented as a state machine on the microcontroller by a real-time operating system kernel from FreeRTOS-is based on a simple linearized geometrical optical model. We benchmark our system using the standard case of coupling laser light efficiently into the guided mode of a single-mode fiber optic patch cable. We can recover the maximum fiber coupling efficiency in ∼10 seconds, even for a laser beam misaligned to the point of zero fiber coupling efficiency.
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