ing at the problem that the inter-satellite laser communication system is easily affected by the pointing errors, the method of third-order central moment is used to make the pointing error equivalent to the modified Rayleigh distribution under the condition that the pointing errors obey the Beckmann distribution. Under the assumptions that the outage probability and the transmission power are fixed, the optimal model of transmitter power and the optimal model of outage probability are established, respectively. The optimal root mean square width of the Gaussian beam emitted by the antenna under the above two assumptions is calculated. Through the numerical simulation, the numerical relationship of the outage probability and the minimum transmitting power with the optimal root mean square width is given. According to the numerical analysis results, the optimal root mean square width of a Gaussian beam can be selected based on the definite pointing error distributions, so that the optimal link performance for the inter-satellite laser communications is obtained.

ing at the problem of the severe image degradation under a low-light condition, a low-light image enhancement algorithm based on deep convolutional neural network (DCNN) is proposed. The training sample is synthesized by this algorithm according to the Retinex model. Then, the original low-light image is converted from RGB (Red Green Blue) space to HSI (Hue Saturation Intensity) color space. The luminance component is enhanced by using the DCNN while keeping the chrominance component and the saturation component unchanged. Finally, the image is turned back to the RGB space from HSI color space to get the finally enhanced image. The experimental results show that, compared with the existing excellent image enhancement algorithms, the proposed algorithm can not only effectively enhance the brightness and the contrast, but also can avoid the color distortion and the over-enhancement, and both the subjective vision and objective evaluation index are further improved.

ing at the shortcomings of low absorptivity and narrow working band for a single structure nano-antenna, we propose a multi-slot butterfly dipole nano-antenna by the fusion of the multi-slot structure and the butterfly dipole. The multi-slot butterfly dipole is formed from an Au nano-butterfly dipole etched by multiple slots. This structure can simultaneously realize the near-field coupling of tips, the grating coupling, and the hybrid coupling among different media. The coaction of these three couplings can effectively improve the absorptivity in a wide band. The absorption performance of this nano-antenna in a wide band is analyzed by the finite-difference time-domain method. The numerical analyses show that several absorption peaks exist in the absorption characteristic curve of this multi-slot butterfly dipole nano-antenna in the 400-1800 nm band, and the maximum and the average absorptivities are 98.4% and 84.1%, respectively. The absorption performance of the proposed nano-antenna is obviously superior to that of the butterfly dipole nano-antenna. This antenna can keep a stable absorption performance in a wide band under different polarization states and different incident angles of light.