An Unconventional Approach to Compensate Wavefront Aberrations in Receivers for Space-to-ground Optical Communications

We propose a device to passively counteract the blurring of the focal spot at the receiver of a free-space laser communications system. By exploiting the negative refractive behavior of photonic crystals, aberrations in the optical system are compensated without increasing the propagation angle. We present the design of the photonic crystal structure and analyze its dispersion property. The prediction is confirmed by means of a rigorous electromagnetic numerical method. Furthermore, to estimate the impact of our approach to optical receivers, we employ the ray trace method and show that all the beams emerging from spots located in front of the crystal pass through a smaller limited area behind the crystal without any increase in propagation angle.