Thermo‐optical Tunable Ultracompact Chip‐Integrated 1D Photonic Topological Insulator

Abstract

study of topological physics for bulk-edge correspondence. It is difficult to directly observe the topological properties of the bulk band, but instead one can explore it by probing the TES. [28][29][30] Although the topological edge state in 2D-and 3D-topological systems can transport unidirectionally, this requires complex design and fabrication processes; hence, very few of these structures have an experimentally observed TES at optical or communication frequencies. [30,31] Chan [1] et al. first used the Zak phase [32] to predict the photonic TES in the 1D PC heterostructure system. The method they proposed was convenient for designing a TES in different bandgaps of the 1D PC heterostructure. [2,4,5] The edge local TES can induce photons to transmit through the PCs at frequencies in the bandgap, which offers a new way to control photon transportation. However, the use of a PC heterostructure to control photon transportation in 1D PCs means that the light should propagate normal to the films, which is unsuitable for integrated photonic circuits.To extend applications of photonic topology in integrated photonic circuits, we propose the use of 1D-grating heterostructures to generate topological edge states. The grating resembles the 1D PC according to the similarity of the Bragg scattering effect when photons propagate along lattice periods. The 1D-grating heterostructure has advantages in terms of both ease of design and the relatively simple fabrication processes compared with those for 2D-and 3D-topological systems. Furthermore, the film-parallel transportation, communication wavelength range design and the compact size might allow for practical integration of 1D photonic topology with on-chip platforms. We first designed grating heterostructures from a 1D PC heterostructure and showed their similarity and the feasibility of constructing a TES in the grating heterostructure. We then fabricated the Si/SiO 2 grating heterostructure to verify the TES transmission peak in an experiment. Finally, we realized a thermally tunable topological grating heterostructure with a metalinsulator transition material vanadium dioxide (VO 2 ), enabling control of the TES and photon propagation in the bandgap. From 1D PC to GratingWe start from the TES in a two joint 1D-perfect photonic crystal and then show that the grating structures on the chip An on-chip integrated one-dimension topological insulator in the optical communication range is realized directly in an integrated photonic circuit. The system takes on a configuration of a 220 nm thick 1D photonic crystal heterostructure sandwiched between two gold films. A photonic topological edge state centered at 1550 nm is obtained for the chip-integrated onedimension topological insulator made of a silicon/SiO 2 photonic crystal heterostructure with a feature size of only 2.25 µm integrated with a silicon waveguide. On/off switching of the photonic topological edge state was also achieved in a 1D topological insulator made of a VO 2 /SiO 2 photonic crystal heterostructure based o...

Recent advances in 2D, 3D and higher-order topological photonics

“…Therefore, reconfigurable topological systems that support topological phase transitions that can be manipulated are essential. Dynamic control of topological phase transitions has been achieved using liquid crystals 228 , a phase-change material under temperature variation 229,230 and transparent conducting oxides under optical pumping 231 . A reconfigurable photonic topological system that supports selective propagation of topological edge modes under mechanical modulation was demonstrated using a bianisotropic photonic crystal 150 .…”

Quantum Topological Photonics

“…The SSH model provides a simple and convenient way to study the topological properties of photonic systems and dielectric and metal pillars have been used for the localized photonic mode [ 46 ] and the local surface plasmon resonance (LSPR) mode, [ 47 ] respectively. However, the topological edge states in this case cannot be detected directly through transmission in the manner of 2D structures, and thus researchers generally use near‐field observation technologies such as the scanning near‐field optical microscope (SNOM) [ 47,48–50 ] or the atomic force microscope (AFM).…”

Dynamically reconfigurable topological edge state in phase change photonic crystals

“…Recently, a photonic topological insulator (PTI) with mechanical reconfigurability was demonstrated in the GHz region [4,6], where they tuned the TES by adjusting the geometric parameters of PTI that slows the tuning speed of the TES; very few of dynamically reconfigurable PTI were undertaken. Very recently, switching of the TES by both liquid crystal orientation and temperature were reported [23,24]; moreover, researchers experimentally demonstrated the nonlinearity-engineered topological transition in electric circuits [25] and electromagnetic resonators array [26], which paves the way for active controlling of the TES. However, most of the techniques discussed above are limited by the switching speed of TESs.…”