Integrated Multi-Dithering Controller for Adaptive Optics

Effective compensation of phase noise in laser communication calls for fast, real-time, adaptive wavefront control. We present an analog, continuous-time, high-speed VLSI (Very Large Scale Integration) controller implementing multi-dithering perturbative gradient descent optimization of a direct measure of optical performance. The system applies parallel sinusoidal perturbations to the wavefront over a range of frequencies, and performs parallel synchronous detection of the metric signal to derive the gradient components over each frequency band. The system operates over a wide range of frequencies, supporting applications of model-free adaptive optics extending from compensation of slow atmospheric turbulence to compensation of fast random phase fluctuations in the actuators and laser amplifiers. The system has been tested as a phase controller for a multiple laser beam wavefront propagating through a highly turbulent medium. The results indicate a compensation bandwidth exceeding 300 kHz matching the turbulence bandwidth.