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单光子源通常采用基于高斯光束的高度衰减激光脉冲,假设激光束具有初始高斯时域脉冲波形和TEM_(01)模拉盖尔-高斯空域分布.基于折射率起伏的Rytov近似和修正von Karman谱模型,研究了大气湍流对星地量子通信单光子捕获概率的影响;建立了上行信道和下行信道的单光子捕获概率理论模型;针对低轨卫星-地面站间激光链路,对单光子捕获概率进行了分析.结果表明:上行信道的单光子捕获概率强烈依赖于地面折射率结构常数C_n~2(0),且随着C_n~2(0)的增加而减小;然而,下行信道的单光子捕获概率并不依赖于C_n~2(0),即大气湍流对其没有影响.
Single-photon sources usually use highly attenuated laser pulses based on Gaussian beams, assuming that the laser beam has initial Gaussian time-domain pulse shape and TEM 01 mode Laguerre-Gaussian spatial distribution. The Rytov approximation based on refractive index fluctuations and the modified von Karman spectrum Model, the influence of atmospheric turbulence on the single-photon capture probability of the ground-based quantum communication has been studied. The single-photon capture probability theoretical model of the uplink channel and the downlink channel has been established. For the low-orbit satellite-ground station laser link, The results show that the single-photon capture probability of the uplink channel strongly depends on the structure constant of ground refractive index C_n ~ 2 (0), and decreases as C_n ~ 2 (0) increases. However, Photon capture probability does not depend on C_n ~ 2 (0), that is, atmospheric turbulence has no effect on it.