Angular spectrum-based wave-propagation method with compact space bandwidth for large propagation distances

Rigorous propagation methods enable diffraction calculations at high NA. However, for the case of large propagation distances and full NA calculations of a signal, common solutions require zero padding or upsampling. This Letter overcomes these problems by introducing a sampling scheme based on compact space bandwidth product representation, which adjusts the sampling frequency of input and propagated field according to the evolution of the generalized space bandwidth product. This sampling concept allows proposing a novel AS method enabling high efficiency, high accuracy, and high-NA diffraction computations at larger propagation distances without need of zero padding or upsampling. The method has several advantages: (1) high accuracy for larger propagation distances; (2) reduced sampling with minimal computation effort; (3) zooming capability; and (4) both focusing and defocusing propagations possible.