High Figure of Merit Optical Buffering in Coupled-Slot Slab Photonic Crystal Waveguide with Ionic Liquid

Topological rainbow based on coupling of topological waveguide and cavity

Topological photonics and topological photonic states have opened up a new frontier for optical manipulation and robust light trapping. The topological rainbow can separate different frequencies of topological states into different positions. This work combines a topological photonic crystal waveguide (topological PCW) with the optical cavity. The dipole and quadrupole topological rainbows are realized through increasing cavity size along the coupling interface. The flatted band can be obtained by increasing cavity length due to interaction strength between the optical field and defected region material which is extensively promoted. The light propagation through the coupling interface is built on the evanescent overlapping mode tails of the localized fields between bordering cavities. Thus, the ultra-low group velocity is realized at a cavity length more than the lattice constant, which is appropriate for realizing an accurate and precise topological rainbow. Hence, this is a novel release for strong localization with robust transmission and owns the possibility to realize high-performance optical storage devices.

One-Dimensional Topological Photonic Crystal Mirror Heterostructure for Sensing

A paradigm for high-quality factor (Q) with a substantial fulfillment for appraising sensing ability and performance has been investigated. Through constructing a 1D (one-dimensional) topological photonic crystal (PhC) mirror heterostructure, which is formed by the image view of 1D topological PhC stacking with its original one. In the 1D topological PhC-mirror heterostructure, there is an interesting mode that appeared with the symmetric, typical Lorentzian-line shape with 100% transmittance in the topological mirror edge-state mode (hybrid resonance mode) at the heterostructure interface. Physically, such a mode is a defect mode, but the defect is introduced through topological operations. The high Q-factor of 5.08 × 10⁴ is obtained due to the strong optical localization of the defect mode at the topological edge area. Consequently, this device acts as a narrow passband filter. Moreover, due to the narrow bandpass property, it may be an advantageous reference for many applications in filtering, switching, and sensing. Thus, introducing an electro-optical (EO) polymer layer at the interface to modify the edge defect can tune the defect mode both in frequency and Q-factor for higher spatial pulse compression and higher EO sensitivity. Accordingly, the Q-factor of 105, the sensitivity of 616 nm/RIU, and the figure of merit of 49,677.42 RIU⁻¹ are obtained. The sensing ability and performance are attributable to the strong optical localization in the interface region and enhanced light-matter interaction. We predict that the 1D topological PhC mirror heterostructure will be an outstanding point in the field of optical sensing, filters, and optical switching in different fields.

Elongated-Hexagonal Photonic Crystal for Buffering, Sensing, and Modulation

A paradigm for high buffering performance with an essential fulfillment for sensing and modulation was set forth. Through substituting the fundamental two rows of air holes in an elongated hexagonal photonic crystal (E-PhC) by one row of the triangular gaps, the EPCW is molded to form an irregular waveguide. By properly adjusting the triangle dimension solitary, we fulfilled the lowest favorable value of the physical-size of each stored bit by about μ5.5510 μm. Besides, the EPCW is highly sensitive to refractive index (RI) perturbation attributed to the medium through infiltrating the triangular gaps inside the EPCW by microfluid with high RI sensitivity of about 379.87 nm/RIU. Furthermore, dynamic modulation can be achieved by applying external voltage and high electro-optical (EO) sensitivity is obtained of about 748.407 nm/RIU. The higher sensitivity is attributable to strong optical confinement in the waveguide region and enhanced light-matter interaction in the region of the microfluid triangular gaps inside the EPCW and conventional gaps (air holes). The EPCW structure enhances the interaction between the light and the sensing medium.

Polarization-Independent Circulator Based on Composite Rod of Ferrite and Plasma in Photonic Crystal Structure

We propose a type of polarization-independent circulator based on a composite rod of ferrite and plasma materials in a two-dimensional photonic crystal (PhC) slab. Only one composite rod was set at the center of the structure to provide circulation for both TE- and TM-polarized waves. Additionally, to improve the performance of the circulator, three additional rods were inserted to improve the coupling condition between the center magneto-optical microcavity and the corresponding waveguides. Finite element method was used to calculate the characteristics of the structure and the Nelder–Mead optimization method was employed to obtain the optimum parameters. The results show that a low insertion loss (~0.22 dB) and high isolation (~14 dB) can be achieved in our structure for waves of both TE and TM polarizations. The idea presented here may be useful for designing compact polarization devices in large-scale integrated photonic circuits.