High Bandwidth / Low Latency wavefront sensing for airborne directed energy applications

Ground-based laser weapon systems and imaging systems are susceptible to atmospheric-induced wavefront aberrations. Control loop architectures are employed to address global tilts and can implement adaptive optics beam control by detecting the wavefront and utilizing a deformable mirror or phase modulators in a Coherent Beam Combination architecture to rectify atmospheric distortions. Airborne platforms face additional wavefront perturbations near the aircraft body or turret, necessitating high spatial resolution and high-bandwidth real-time wavefront measurements for closed-loop adaptive optics correction. The challenge lies in achieving high-bandwidth real-time wavefront sensing since existing sensor technologies have limitations in this aspect. Traditional focal plane arrays, for instance, are typically restricted to sampling rates in the 1-10 kHz range, even when paired with high-bandwidth streaming cameras using CoaXPress data transmission. Although some high-speed cameras can exceed 100 kHz sampling rates, they store data in local memory, making it unsuitable for real-time processing. To address this challenge, we propose the adoption of position sensing diodes (PSDs) as a promising solution for achieving high-bandwidth real-time wavefront data processing. This architecture has been previously demonstrated in a 10x10 array with a 100kHz sample rate [Abado, 2010]. PSDs offer the advantage of rapid data acquisition. Furthermore, to overcome the computational hurdles, we envision a seamless integration of PSDs with field-programmable gate arrays (FPGAs). This FPGA-based processing approach will enable swift calculations of the center of gravity for wavefront slopes and the application of advanced reconstruction algorithms, paving the way for an effective high-bandwidth wavefront sensing technology.