High-Q filters with complete transmission by quasi-periodic dielectric multilayers

Photonic-crystal-based high-performance ring resonator using a topological interface state: design and analysis

We propose a photonic crystal ring resonator for the enhancement of quality factor that supports two-dimensionally bounded topological edge states. Crystal parameters are obtained through finite-difference time-domain numerical simulation to get the enhanced quality factor using the topological properties of the photonic crystal. Topological edge states are created when two regions with dissimilar band topologies come together at an interface and are contained within a slab of dielectric material. These edge states can move along sharp edges without backscattering. The transmission dropout issue arises whenever the quality factor is enhanced in a conventional photonic system and is eliminated remarkably by employing the present approach. Such nanoscale photonic crystal structures promote robust interactions between quantum emitters and photonic edge states.

Robust high-Q filter with complete transmission by conjugated topological photonic crystals

High quality factor (High-Q) and transmission optical devices are required for various applications in the fields of physics and engineering. Critical for these applications is the realization of a structure with high-Q, complete transmission and small volume. A robust high-Q filter with complete transmission by conjugated topological photonic crystals (CTPC) is presented. The study shows that an ultra-high-Q of more than 108 with complete transmission is obtained by the CTPC with 2 μm long due to the excitation of conjugated topological edge-states (CTES). It is also found that even though the quality factor of resonances increases as the periodic number of multilayers increases, these resonances are still complete transmission. A novel concept of CTES is first proposed in this study and investigated the effect of its topological phenomenon on high quality factor via CTPC. We theoretically realize the robust high-Q and complete transmission in the CTPC, which is different from those in periodic, quasi-periodic, Fabry-Perot photonic crystals and traditional topological photonic crystals (TPC).

Ultra-slow light in one-dimensional Cantor photonic crystals

Ultra-slow light and complete transmission properties in one-dimensional Cantor photonic crystals are presented. In contrast to traditional dielectric photonic crystals, the proposed structure has large group delay, slower group velocity, and a high quality factor within the same layers and materials. This study shows that larger than 1 μs group delay and slower than 1 m/s group velocity are achieved in the fifth-order Cantor photonic crystal with 52.75 μm length. This ultra-slow-light structure is very promising for application in advanced slow-light devices. A high quality factor of 10⁹ and multiband filters with complete transmission can also be obtained by using this approach.

Extraordinary light absorptance in graphene superlattices

Extraordinary absorption decrease in graphene superlattices in the visible range is presented. Due to competition between loss and resonant reflection at resonance, the absorption displays non-monotonic behavior. As the period number increases above a certain critical value, absorption decreases with the increase in the period number. This is in contrast to ordinary absorption for a non-resonant condition, which monotonically increases with the period number. Moreover, this extraordinary property can also be controlled by applying a gate voltage to graphene sheets. The results provide not only a new understanding of graphene physics but also an application in nanophotonics and optoelectronics.

Exciton photoluminescence in resonant quasi-periodic Thue-Morse quantum wells

This Letter investigates exciton photoluminescence (PL) in resonant quasi-periodic Thue-Morse quantum wells (QWs). The results show that the PL properties of quasi-periodic Thue-Morse QWs are quite different from those of resonant Fibonacci QWs. The maximum and minimum PL intensities occur under the anti-Bragg and Bragg conditions, respectively. The maxima of the PL intensity gradually decline when the filling factor increases from 0.25 to 0.5. Accordingly, the squared electric field at the QWs decreases as the Thue-Morse QW deviates from the anti-Bragg condition.