  Dynamic wavefront aberrations negatively impact a wide range of optical
applications including astronomy, optical free-space telecommunications and
bio-imaging. Wavefront errors can be compensated by an adaptive optics system
comprised of a deformable mirror and wavefront sensor connected by a control
loop. For satellite optical communications (SatCom), wavefront sensing is
particularly challenging due to the rapid wavefront fluctuations induced by
strong turbulence and movement of the transmitting satellite across the sky.
Existing wavefront sensing techniques require fast cameras (>kHz) that are not
widely available at wavelengths suitable for SatCom (e.g., 1550nm and
mid-to-long wave infrared). Here, we propose a new wavefront sensing technique
that uses a single photodiode and a fast mirror to make phase-diverse intensity
measurements of the incoming wavefront. We train neural networks to accurately
estimate the input phase given this phase-diverse sub-millisecond intensity
trace. Our simulations show that our technique is robust in cases of strong
turbulence where previous modal wavefront sensors fail due to modal crosstalk,
achieving 99% of the optimal Strehl ratio from a 50-mode correction at a
sensing rate of 2kHz. We explore typical cases of turbulence magnitude, sensing
speed and noise that might be encountered by such a system.
