A compact and open-source microcontroller-based rapid auto-alignment system

TL;DR

This paper introduces a compact, open-source microcontroller-based system for rapid laser beam auto-alignment, utilizing PSD sensors and piezoelectric mirrors, achieving efficient fiber coupling within approximately 10 seconds.

Contribution

It presents a novel hardware and software implementation of a microcontroller-driven auto-alignment system using a simple optical model and real-time control strategies.

Findings

Achieves maximum fiber coupling efficiency in about 10 seconds

Effectively recovers alignment from severe misalignments

Operates with a simple, open-source hardware and software setup

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 mirrors mounts. Our auto-alignment strategy -- implemented as a state machine on the microcontroller by a FreeRTOS kernel -- 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 $\sim10$ seconds, even for a laser beam that was misaligned to the point of zero fiber coupling.