Autofocusing and self-healing of partially blocked circular Airy derivative beams

We numerically and experimentally study the autofocusing and self-healing of partially blocked circular Airy derivative beams (CADBs). The CADB consists of multiple rings, and partial blocking of CADB with different kinds is achieved by using symmetric and asymmetric binary amplitude apertures, enabling blocking of inner/outer rings and sectorially. The CADB blocked with different types possesses the ability to autofocus, however, the abruptness in the autofocusing varies with the amount in certain types of blocking. The abrupt autofocusing is quantified by a maximum k-value, and how fast it changes around the autofocusing distance (zaf). In particular, CADB blocked with inner rings (first/two/three) exhibits an abrupt autofocusing, as the k-value sharply increases [decreases] just before [after] zaf. The maximum k-value always occurs at zaf, which decreases as the number of blocked inner rings increases. For CADB blocked with outer rings, the k-value gradually changes around zaf, indicating a lack of abrupt autofocusing. The value of zaf increases with the number of blocked outer rings. This suggests that although outer rings contain low intensities, these play an important role in abrupt autofocusing. A sectorially blocked CADB possesses an abrupt autofocusing, and maximum k-value depends on the amount of blocking. The CADB blocked with different types possesses good self-healing abilities, where blocked parts reappear as a result of redistribution of intensity. The maximum self-healing occurs at zaf, where an overlap integral approaches a maximum value. Finally, we have compared ideal CADB and partially blocked CADB having the same radii of central dark region, and found that an ideal CADB possesses better abrupt autofocusing. We have found a good agreement between the numerical simulations and experimental results.