FPGA-Based Real-Time Laser Beam Profiling and Stabilization System for Quantum Simulation Applications

Abstract

Lasers are imperative in quantum simulation experiments to trap and cool atoms. With the growing complexity of experimental setups, precise control and stability of the position and exotic shape of lasers have become essential for high-fidelity operations. However, disturbances such as temperature fluctuations, mechanical vibrations, deformation of materials, and acoustic noise pose challenges to fulfill these requirements. In this paper, we propose and evaluate the first system for stabilizing the laser's beam position using two high-resolution cameras with high frame-rates, and image processing in a field-programmable gate array (FPGA) with low latency and subsequent in-loop feedback to the laser control. The proposed image processing hardware extracts the Gaussian beam distribution from two 5 MP cameras at 47 fps and 435 ns latency. These are fed to four proportional-integral-derivative (PID) controllers implemented on the FPGA. The PID modules provide feedback through parallel digital-to-analog converter (DAC) channels for steering mirrors to stabilize the beam within 5 µm accuracy. Using two cameras at distinct sample distances on the optical axis allows for controlling the incidence angle of the laser beam onto the image planes. The current system is a building block for future extensions allowing real-time phase-feedback on optical lattices, stabilization of independent optical tweezers in an array, and focus position stabilization of transverse electromagnetic (e.g. TEM01) modes enabling large-scale quantum simulations.