Model-based real-time synthesis of acousto-optically generated laser-beam patterns and tweezer arrays

Acousto-optic deflectors (AODs) enable spatiotemporal control of laser beams through diffraction at an ultrasonic grating that is controllable by radio-frequency (rf) waveforms. These devices are a widely used tool for high-bandwidth random-access scanning applications, such as optical tweezers in quantum technology. A single AOD can generate multiple optical tweezers by multitone rf input in one dimension. Two-dimensional (2D) patterns can be realized with two perpendicularly oriented AODs. As the acousto-optical response depends nonlinearly on the applied frequency components, phases, and amplitudes, and in addition experiences dimensional coupling in 2D setups, intensity regulation becomes a unique challenge. Guided by coupled-wave theory and experimental observations, we derive a compute-efficient model which we implement on a graphics processing unit. Only one-time sampling of single-tone laser-power calibration is needed for model parameter determination, allowing for straightforward integration into optical instruments. We implement and experimentally validate an open-loop diffraction efficiency control system that enables programmable 2D multibeam trajectories with intensity control applied at every time step during digital signal generation, overcoming the limited flexibility, pattern-size constraints, and bandwidth limitations of methods using precalculation and precalibration of a predefined pattern set or closed-loop feedback. The system is capable of stable real-time waveform streaming of arrays with up to <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mn>50</a:mn> <a:mo>×</a:mo> <a:mn>50</a:mn> </a:math> tweezers with minimal time resolution of 1.4 ns (700 MS/s) and a peak latency below 257 µs for execution of newly requested patterns. Reactive, real-time 2D multibeam laser patterning and scanning with strict intensity matching will substantially benefit parallelization and increasing data rates in materials processing, microscopy, and applications of optical tweezers, where the work presented is of immediate relevance for time-critical conditional operations with minimal latency.