A Topological Multichannel Add-Drop Filter Based on Gyromagnetic Photonic Crystals

Abstract

We theoretically proposed a topological multichannel add-drop filter (ADF) and studied its unique transmission properties. The multichannel ADF was composed of two one-way gyromagnetic photonic crystal (GPC) waveguides, a middle ordinary waveguide, and two square resonators sandwiched between them, which can be regarded as two paralleling four-port nonreciprocal filters. The two square resonators were applied with opposite external magnetic fields (EMFs) to support one-way states propagating clockwise and counterclockwise, respectively. On the basis of the fact that the resonant frequencies can be tuned by the EMFs applied to the square resonators, when the intensities of EMFs were the same, the multichannel ADF behaved as a power splitter with a 50/50 division ratio and high transmittance; otherwise, it functioned as a demultiplexer to separate two different frequencies efficiently. Such a multichannel ADF not only possesses excellent filtering performance but also has strong robustness against various defects due to its topological protection property. Moreover, each output port can be switched dynamically, and each transmission channel can operate independently with little crosstalk. Our results have the potential for developing topological photonic devices in wavelength division multiplexing systems.

THz wave Mux/DeMux operation using bearded-type topological photonic crystal waveguide structure

“…[30][31][32] The oblique rectangular waveguide was arranged under the VPC waveguide, which was designed to demultiplex a specific frequency signal from its resonance state. A schematic of the THz demultiplexing 02SP27-5 © 2024 The Japan Society of Applied Physics IC based on the VPC-based resonator, which was electromagnetically coupled with the VPC waveguide [32][33][34] and the simulated intensity distribution of the magnetic field at the resonant frequency is shown in Fig. 6.…”

Multifunctional topological photonic crystal device for multichannel frequency routing and highly sensitive refractive index sensing

“…Among these devices, PCs with topological edge states (TESs) have emerged as promising candidates for next-generation optical applications due to their exceptional properties, such as immunity to backscattering and robust propagation along edges [7,8]. In the domain of optical communication systems, the ability to transmit multiple channels simultaneously is crucial for achieving high bandwidth and data transfer rates [9]. Multichannel frequency routing, the process of guiding multiple frequencies through distinct paths, has traditionally been challenging to implement using conventional optical components [10].…”

“…However, PCs with TESs offer a promising solution to this challenge. These edge states, which exist at the boundaries of the PC structure, can propagate multiple frequencies without interference, enabling the realization of multichannel optical devices [9][10][11][12]. Refractive index (RI) sensing is a critical technique in various fields, including biosensing, chemical detection, and environmental monitoring [13][14][15].…”

Controllable Pseudospin Topological Add-Drop Filter Based on Magnetic–Optical Photonic Crystals

“…In recent years, photonic crystal ring resonators (PCRRs) have attracted great attention due to their excellent characteristics such as low loss, high quality factor, as well as flexible configurations. Because of their efficient resonant coupling nature, various PCRR-based optical devices, such as ultra-high-Q optical filter [ 17 ] and topological ADF [ 18 , 19 , 20 ], have been proposed. Especially noteworthy is an add-drop filter (ADF), which allows the transfer of one or several frequency channels from the bus waveguide through a resonator system to the drop waveguide without disturbing the other channels, playing an important role in many application fields, such as wavelength division multiplexing systems.…”