Conjugated topological interface-states in coupled ring resonators

The optical properties of topological photonics have attracted much interest recently because its potential applications for robust unidirectional transmission that are immune to scattering at disorder. However, researches on topological series coupled ring resonators (T-SCRR) have been much less discussed. The existence of topological interface-states (TIS) in the T-SCRR is described for the first time in this article. An approach has been developed to achieve this goal via the band structure of dielectric binary ring resonators and the Zak phase of each bandgap. It is found that an ultra-high-Q with complete transmission is obtained by the conjugated topological series coupled ring resonators due to the excitation of conjugated topological interface-states, which is different from those in conventional TIS. Furthermore, the problem of transmission decreases resulting from high-Q increases in the traditional photonic system is significantly improved by this approach. These findings could pave a novel path for developing advanced high-Q filters, optical sensors, switches, resonators, communications and quantum information processors.

Broadband Spin-Dependent Directional Coupler via Single Optimized Metallic Catenary Antenna

With the rapid development of on-chip optics, integrated optical devices with better performance are desirable. Waveguide couplers are the typical integrated optical devices, allowing for the fast transmission and conversion of optical signals in a broad working band. However, traditional waveguide couplers are limited by the narrow operation band to couple the spatial light into the chip and the fixed unidirectional transmission of light flow. Furthermore, most of the couplers only realize unidirectional transmission under the illumination of the linear polarized light. In this work, a broadband polarization directional coupler based on a metallic catenary antenna integrated on a silicon-on-insulator (SOI) waveguide has been designed and demonstrated under the illumination of the circularly polarized light. By applying the genetic algorithm to optimize the multiple widths of the metallic catenary antenna, the numerical simulation results show that the extinction ratio of the coupler can be maintained larger than 18 dB in a wide operation band of 300 nm (from 1400 to 1700 nm). Moreover, the coupler can couple the spatial beam into the plane and transmit in the opposite direction by modulating the rotation direction of the incident light. The broadband polarization directional coupler might have great potential in integrated optoelectronic devices and on-chip optical devices.

Broadband and polarization-mediated unidirectional plasmon polaritons launch based on metallic triangle aperture arrays

The application of the subwavelength planar structure to control the propagation direction of surface plasmon polaritons (SPPs) has attracted many interests in recent years. However, the traditional unidirectional transmission devices of SPPs are limited by the low extinction ratio, narrow working band and the incapability of controlling the transmission directions. In this study, a novel SPPs unidirectional transmission device based on metallic aperture arrays of the right triangle (RT) is proposed and demonstrated by numerical simulations (finite-difference time-domain method). The maximum extinction ratio of the unidirectional transmission device can reach upto 33 dB under the irradiation of linearly polarized light, and the device possesses a wide operating band ([Formula: see text] nm) while the extinction ratio is greater than 10 dB. Moreover, the transmission direction of SPPs can be flexibly controlled by tuning the polarization of the incident beam. This broadband, polarization-mediated and high extinction ratio unidirectional transmission device shows great potential in the compact plasmonic devices.