In this work, we study a composite zinc oxide photonic crystal that includes a meso-cavity coupled to a photonic crystal L3 microcavity to obtain a double resonance effect and second-harmonic generation conversion efficiency as high as 468 W-1. This exceptional conversion efficiency was attributed to the high quality-factors Q found in the fundamental and second-harmonic modes whose values were of the order of 105 and 106, respectively. Since the L3 microcavity plays a relevant role in the second-harmonic generation of the composite photonic crystal, we performed a calculation of its photonic band structure to observe the induced modes in its bandgap. Furthermore, we also found that the resonant mode adjusted to the frequency of the second-harmonic exhibits high Purcell factors of the order of 105. Hence, in a semiconductor material, it can be easily enhanced the light emission at the second harmonic frequency using an adequate driving fundamental frequency light beam. These results can stimulate the engineering of photonic nanostructures in semiconductor materials to achieve highly efficient non-linear effects with applications in cavity Quantum Electrodynamics.
Topological photonics has attracted remarkable attention in recent years due to its ability to generate robust topological states, especially suitable for the study of cavity quantum electrodynamics. In this work, we present a theoretical study of a topological photonic crystal based on the 2D Su–Schrieffer–Heeger model, with corner states induced by a rotational operation on the axis parallel to the interface of two different topologies of a photonic crystal, forming a bowtie cavity. The studied topological photonic crystal presents inversion symmetry due to the rotation operation allowing the simultaneous existence of two non-degenerated corner states: one located in the weak coupling regime and the other in the strong coupling regime. Therefore, we present the emergence of distinctive effects from both regimes, such as the Purcell effect and Rabi splitting. We also address the study of the origin and evolution of the corner states resulting from the bulk-edge-corner correspondence. The topological bowtie cavity studied in this work combines the virtues of topological systems and the extreme confinement offered by cavities with bowtie architecture, which enriches the study of corner states in sophisticated topological structures.
This research shows that the morphological characteristics of the external microstructure of the beautiful skin of the Urosaurus ornatus lizard contribute to the explanation of the origin of their iridescent and thermal properties. High-resolution scanning electron microscopy studies revealed that the skin surface of the U. ornatus lizard is constituted by a semi-ordered array of hexagonal photonic crystals with sub-micrometric structural parameters. The iridescence properties of the ventral patch and dorsal surface of the U. ornatus lizard were numerically simulated modeling both surfaces by a set of coupled photonic crystals with structural parameters proposed from statistical measurements of the lattice parameter and holes diameter of its skin surface. The dorsal surface showed the ability to reflect visible light and at least in a significant range the ultraviolet and near infrared radiation. A complete photonic band gap for the transverse magnetic polarization mode of the incident light in both dorsal and ventral surfaces was predicted by calculations. The spectral reflectance and the structure of photonic bands obtained explain the reflection of the infrared radiation by the dorsal surface which might help to the thermoregulation of the lizard body. The results obtained suggest that the selective reflection of incident light performed by the photonic structural array defined on the skin surface of the U. ornatus has a significant contribution to its apparent color.
In this work, we present an experimental study of the angular dependence of the optical reflectance in two 2-dimensional photonic structures, built on a silicon substrate coated with a ZnO thin film. Photonic structures studied describe a regular square lattice with a lattice constant a = 1.05 μm and circular air holes with a radius r = 0.63a. Additionally, one of these photonic structures contains a pattern of nine quasi-circular micro-cavities embedded in a regular square lattice photonic crystal, describing a secondary square lattice. A comparison of the optical reflectance of the two photonic structures as a function of the incidence angle for transverse magnetic polarization mode in the visible (Vis) and near-infrared (NIR) ranges of the electromagnetic spectrum was accomplished. Results obtained revealed a strong angular dependence of the reflective optical properties of the two 2-dimensional photonic structures on the illumination incidence angle. The photonic structure with the array of resonant optical cavities presented a very unusual behavior regarding the reflectance of the substrate, this because its reflectance described specific modulations dependent on the incidence angle of illumination.
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