We introduce a new class of ($2+1$) dimensional circle Pearcey beams (CPBs) with the abruptly autofocusing (AAF) characteristics. Compared with circular Airy beams, CPBs can increase the peak intensity contrast, shorten the focus distance and, especially, eliminate the oscillation after the focal point. Furthermore, we discuss the influence of the optical vortices (including on-axis, off-axis, and vortex pairs) on the light intensity distribution of the CPBs during propagating.

In this Letter, we introduce a new class of abruptly autofocued and rotated circular chirp Pearcey Gaussian vortex beams (AARCCPGVBs) which tend to abruptly autofocused circular chirp Pearcey vortex beams or chirp Gaussian vortex beams by adjusting the spatial distribution factors. Different from other rotated beams [Opt. Lett. 31, 694 (2006) [CrossRef] and Opt. Lett. 31, 2199 (2006) [CrossRef] ], the AARCCPGVBs are autofocused abruptly, maintain a low rotating speed before the focal point, and rotate abruptly and quickly in the focal point. Further, the position of the focal point in the propagating direction can also be controlled by adjusting the chirp factor.

We study the photonic band structures and the attenuation behavior of waves in configuration-periodic square networks where nearest-neighbor nodes are connected by more than one segment. It is shown that even though the period of the unit cell of a square network cannot be defined by the lengths of the segments and the nodes may not be arranged periodically in space, one can still use the Floquet-Bloch theorem in this network system if the theorem is modified. We find that the attenuation can be extremely large even though there is no absorption in the networks and its strength does not have a quasiparabolic profile as a function of wave frequency inside a gap. Large gaps and narrow passbands created by resonances and antiresonances are found.

The evolution of the chirped ring Pearcey Gaussian vortex (CRPGV) beams in free space is numerically investigated. The optical bottle beam and two-consecutive optical bottle beam can be directly generated from a ring Pearcey Gaussian beam with central vortices and the second-order chirp in free space. In particular, the focusing intensity will decrease when the vortices’ locations are far away from the center of the beam or the topological charges are smaller. Our results show that the beam shapes, the normalized focusing intensity, and the focal length of the CRPGV beams can be controlled by choosing different beam parameters.

In this Letter, a new, to the best of our knowledge, type of autofocusing and symmetric beam arisen from two quartic spectral phases is introduced in theory and experiment. The symmetric Pearcey Gaussian beam (SPGB), formed with a Gaussian term and two multiplying Pearcey integrals, processes a focusing intensity approximately 1.32 times stronger than the intensity of the symmetric Airy beam. Its four off-axis main lobes split into four bending trajectories symmetrically after focusing. The rectangular intensity distribution and the focal length of the SPGB can be adjusted by two kinds of distribution factors. Additionally, the vortex-guiding property of the beam is demonstrated by embedding an off-axis vortex into the SPGB, which can be applied in particle guiding.

Focus-tunable metalenses play an indispensable role in the development of integrated optical systems. In this paper, the phase change material Sb₂S₃ is used in a thermally modulated varifocal metalens based on PB-phase for the first time. Sb₂S₃ not only has a real part of refractive index shift between the amorphous and crystalline state but also has low losses in both amorphous and crystalline states in the near-infrared region. By switching Sb₂S₃ between the two states, a metalens doublet with a variable focal length is proposed. Moreover, the full width at half maximum of each focal point is close to the diffraction limit. And the focusing efficiency can be over 50% for the two focal points. Together with the advantage of precise thermal control, the proposed metalens has great potential in the application of multi-functional devices, biomedical science, communication and imaging.