Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userTopological Photonics on a Small Scale
221
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
The study of topological phases of light suggests novel opportunities for creating robust optical structures and on-chip photonic devices which are immune against scattering losses and structural disorder. However, many recent demonstrations of topological effects in optics employ structures with relatively large scales. Here we discuss the physics and realisation of topological photonics on small scales, with the dimensions often smaller or comparable with the wavelength of light. We highlight the recent experimental demonstrations of small-scale topological states based on arrays of resonant nanoparticles and discuss a novel photonic platform employing higher-order topological effects for creating subwavelength highly efficient topologically protected optical cavities. We pay a special attention to the recent progress on topological polaritonic structures and summarize with our vision on the future directions of nanoscale topological photonics and its impact on other fields.
rate research
Read More
Topological photonics has emerged as a novel route to engineer the flow of light. Topologically-protected photonic edge modes, which are supported at the perimeters of topologically-nontrivial insulating bulk structures, have been of particular interest as they may enable low-loss optical waveguides immune to structural disorder. Very recently, there is a sharp rise of interest in introducing gain materials into such topological photonic structures, primarily aiming at revolu-tionizing semiconductor lasers with the aid of physical mechanisms existing in topological physics. Examples of re-markable realizations are topological lasers with unidirectional light output under time-reversal symmetry breaking and topologically-protected polariton and micro/nano-cavity lasers. Moreover, the introduction of gain and loss provides a fascinating playground to explore novel topological phases, which are in close relevance to non-Hermitian and parity-time symmetric quantum physics and are in general difficult to access using fermionic condensed matter systems. Here, we review the cutting-edge research on active topological photonics, in which optical gain plays a pivotal role. We discuss recent realizations of topological lasers of various kinds, together with the underlying physics explaining the emergence of topological edge modes. In such demonstrations, the optical modes of the topological lasers are deter-mined by the dielectric structures and support lasing oscillation with the help of optical gain. We also address recent researches on topological photonic systems in which gain and loss themselves essentially influence on topological prop-erties of the bulk systems. We believe that active topological photonics provides powerful means to advance mi-cro/nanophotonics systems for diverse applications and topological physics itself as well.
Two-dimensional (2-D) materials are of tremendous interest to integrated photonics given their singular optical characteristics spanning light emission, modulation, saturable absorption, and nonlinear optics. To harness their optical properties, these atomically thin materials are usually attached onto prefabricated devices via a transfer process. In this paper, we present a new route for 2-D material integration with planar photonics. Central to this approach is the use of chalcogenide glass, a multifunctional material which can be directly deposited and patterned on a wide variety of 2-D materials and can simultaneously function as the light guiding medium, a gate dielectric, and a passivation layer for 2-D materials. Besides claiming improved fabrication yield and throughput compared to the traditional transfer process, our technique also enables unconventional multilayer device geometries optimally designed for enhancing light-matter interactions in the 2-D layers. Capitalizing on this facile integration method, we demonstrate a series of high-performance glass-on-graphene devices including ultra-broadband on-chip polarizers, energy-efficient thermo-optic switches, as well as graphene-based mid-infrared (mid-IR) waveguide-integrated photodetectors and modulators.
Over the past decade, topology has garnered great attention in a wide area of physics. In particular, it has exerted influence on photonics because carefully engineered photonic crystals and metamaterials can help explore the non-trivial state of materials. In this regard, all dielectric metamaterials with large anisotropy, and dipole and multipole Mie resonators have played an increasingly important role in topological photonics. Advantages of Mie resonators make it possible to quest for non-trivial states in three dimensions and theoretical calculation supports its potential. However, it is very difficult to demonstrate this experimentally because it is hard to make the metacrystal by anisotropic meta-atoms despite much effort. Here we report a Dirac metamaterial for 3D topological photonics. It is implemented by a metacrystal self-assembled by a molecule, HYLION-12 which has both anisotropic polarizability and ring current. As its peculiar properties, it has an exotic optical constant that can be used for the electric and magnetic hyperbolic metamaterial, and the double hyperbolic metamaterial in the ultraviolet region. It also showed 142% of reflectance at 242nm as an amplified reflector and asymmetric transmittance up to 30% through the opaque substrate as a Huygens source under 300nm. Furthermore, it demonstrated various phenomena of topological photonics such as Pancharatnam-Berry and waveguide phase merging, wavefront shaping and waveguide on edges as a 3D topological photonic material. The new strategy using polyaromatic hydrocarbons (PAHs) is expected to be an effective way to realize 3D topological photonics.
Topological photonics harnesses the physics of topological insulators to control the behavior of light. Photonic modes robust against material imperfections are an example of such control. In this work, we propose a soft-matter platform based on nematic liquid crystals that supports photonic topological insulators. The orientation of liquid crystal molecules introduces an extra geometric degree of freedom which in conjunction with suitably designed structural properties, leads to the creation of topologically protected states of light. The use of soft building blocks potentially allows for reconfigurable systems that exploit the interplay between light and the soft responsive medium.
Nonlinear optics is an increasingly important field for scientific and technological applications, owing to its relevance and potential for optical and optoelectronic technologies. Currently, there is an active search for suitable nonlinear material systems with efficient conversion and small material footprint. Ideally, the material system should allow for chip-integration and room-temperature operation. Two-dimensional materials are highly interesting in this regard. Particularly promising is graphene, which has demonstrated an exceptionally large nonlinearity in the terahertz regime. Yet, the light-matter interaction length in two-dimensional materials is inherently minimal, thus limiting the overall nonlinear-optical conversion efficiency. Here we overcome this challenge using a metamaterial platform that combines graphene with a photonic grating structure providing field enhancement. We measure terahertz third-harmonic generation in this metamaterial and obtain an effective third-order nonlinear susceptibility with a magnitude as large as 3$cdot$10$^{-8}$m$^2$/V$^2$, or 21 esu, for a fundamental frequency of 0.7 THz. This nonlinearity is 50 times larger than what we obtain for graphene without grating. Such an enhancement corresponds to third-harmonic signal with an intensity that is three orders of magnitude larger due to the grating. Moreover, we demonstrate a field conversion efficiency for the third harmonic of up to $sim$1% using a moderate field strength of $sim$30 kV/cm. Finally we show that harmonics beyond the third are enhanced even more strongly, allowing us to observe signatures of up to the 9$^{rm th}$ harmonic. Grating-graphene metamaterials thus constitute an outstanding platform for commercially viable, CMOS compatible, room temperature, chip-integrated, THz nonlinear conversion applications.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
