Numerical Study of Dynamic Adaptive Phase Correction of Radiation Turbulent Distortions and Estimation of their Frequency Bandwidth with a Shack–Hartmann Wavefront Sensor

Simulation of phase correction of sinusoidal distortions in the adaptive optical system with finite operation speed

“…Numerical model of dynamic adaptive phase correction has been described in [5]. The spatial resolution of wavefront sensor and adaptive mirror is considered to be ideal, full attention is payed to the influence of temporal resolution on the correction efficiency.…”

“…Note that phase distortions with a characteristic frequency ν turb whose spectrum represents a frequency band (for example, atmospheric phase distortions) require a lower bandwidth ν AOS for correction than sinusoidal phase distortions with the same ν turb . For example, it was shown in [5] that when atmospheric phase distortions are corrected, a decrease in the laser beam divergence relative to the initial value was observed at ν AOS / ν turb >2. This is explained by the fact that in the case of a frequency band in the temporal spectrum of phase distortions with ν turb , frequencies ν are compensated for which ν AOS / ν > 6, while new harmonics appear with frequencies n ν AOS -ν, where n is an integer.…”

Numerical investigation of dynamic coherent beam combining in turbulent atmosphere with taking into account the double-pass delay

“…For phase distortions under consideration, the Greenwood frequency equals 0.1 Hz. Previously it was shown [11] that the Greenwood frequency approximately equals turbulence bandwidth, which can be determined as a frequency containing 95% of spectral energy of the oscillation spectrum of a Shack-Hartmann wavefront sensor centroid when the sub-aperture size is close to the Fried parameter.…”