大气闪烁对自适应光学校正的影响

Atmospheric scintillation effect on adaptive optics correction

激光在大气湍流中长距离近水平传输时,闪烁加强,限制了常规自适应光学的校正能力。数值研究了大气闪烁对自适应光学校正的影响,拟合得到了在Fresnel数一定时,Strehl比与Rytov方差的表达式,以及Rytov方差一定时,Strehl比与Fresnel数的表达式。结果表明,在Rytov方差较小时,纯相位校正Strehl比只与Rytov方差有关;随着Rytov方差的增加,Strehl比不仅与Rytov方差有关,还与Fresnel数有关,Fresnel数越大,校正Strehl比越大;大发射和接收孔径有利于提高校正Strehl比;在一定的Rytov方差下,Stregl比随Fresnel数增大而增加,逐步趋于饱和,达到纯相位校正的极限。

Scintillation increases when laser propagates long distance near horizontally in the atmosphere, which limits the ability of conventional adaptive optical system. Numerical simulations based on wave optics computer code are given for different atmospheric conditions. For given Rytov variance, different turbulence strengths and propagating distances are considered. Various receiving and projecting apertures are also taken into account. Rytov variance and propagation Fresnel number have still effect on Strehl ratio. The expressions of Strehl ratio with Rytov variance are obtained from weak to strong scintillation. For given Rytov variance, Strehl ratio with Fresnel number is studied. Large aperture can benefit correction. The results show that Strehl ratio increases with Fresnel number increases and saturates to the limit of ideal phase-only correction for given Rytov variance.