Topological singularities, such as Weyl points and Dirac points, can give rise to unidirectional propagation channels known as chiral zero modes (CZMs) when subject to a magnetic field. These CZMs are responsible for intriguing phenomena like the chiral anomaly in quantum systems. The propagation direction of each CZM is determined by both the applied magnetic field and the topological charge of the singularity point. While counter-propagating CZMs have been observed in 2D and 3D systems, the realization of co-propagating CZMs has remained elusive. Here we present the first experimental observation of co-propagating CZMs in magnetic photonic crystals hosting a single pair of ideal Weyl points WPs. By manipulating the crystal's structural configuration, we spatially alter the locations of the WPs, creating pseudo-magnetic fields in opposite directions between them. This arrangement results in a pair of CZMs that possess the same group velocity and co-propagate. Our work opens up new possibilities for topological manipulation of wave propagation and may lead to advancements in optical waveguides, switches, and various other applications.
Chiral quantum optics has attracted considerable interest in the field of quantum information science. Exploiting the spin-polarization properties of quantum emitters and engineering rational photonic nanostructures has made it possible to transform information from spin to path encoding. Here, compact chiral photonic circuits with deterministic circularly polarized chiral routing and beamsplitting are demonstrated using two laterally adjacent waveguides coupled with quantum dots. Chiral routing arises from the electromagnetic field chirality in waveguide, and beamsplitting is obtained via the…
A chiral near field with a highly contorted electromagnetic field builds a bridge to match the chiral molecules and light wavelengths with large size differences. It significantly enhances the circular dichroism of chiral molecules and has great prospects in chirality sensing, detection, trapping, and other chirality-related applications. Surface plasmons feature outstanding light-trapping and electromagnetic-field-concentrating abilities. Plasmonic chiral nanostructures facilitate light manipulation to generate superchiral near fields. Meanwhile, the nanophotonic structures have attracted sig…
The polarizations of topological edge modes in the vicinity of optical Weyl points were numerically studied in chiral photonic crystals. We investigated two kinds of rotationally stacked woodpile structures in which planar rod arrays were vertically stacked one-by-one with an in-plane rotation angle of 60 or 45 degrees. Both structures showed pairs of optical Weyl points having topological numbers of opposite signs for photonic bands in low orders. Topological edge states derived from the Weyl points appeared below the light line, and were strongly confined at the air interfaces in a length sh…
Photonic Floquet lattices provide an excellent platform for manipulating different topologically protect-ed edge states. However, anti-chiral edge states have not been discussed much in Floquet lattices. Here, we propose a waveguide structure by combining two honeycomb Floquet photonic lattices with oppo-site rotation directions. In this structure, we find that the anti-chiral edge states have the same trans-mission direction on two parallel body edges. With an increasing modulation phase difference between the two sublattices in one direction, the width of the band gap becomes smaller and the…
We experimentally investigate the impact of uncorrelated composite and structural disorder in photonic graphene. We find that in case of structural disorder not only chiral symmetry, but also the vanishing of the density of states at zero energy is preserved. This is in contrast to composite disorder, where chiral symmetry as well as the vanishing of the density of states are destroyed. Our observations are experimentally proven by exciting edge states at the bearded edge in disordered photonic graphene.
Much of the recent enthusiasm directed towards topological insulators as a new state of matter is motivated by their hallmark feature of protected chiral edge states. In fermionic systems, Kramers degeneracy gives rise to these entities in the presence of time-reversal symmetry (TRS). In contrast, bosonic systems obeying TRS are generally assumed to be fundamentally precluded from supporting edge states. In this work, we dispel this perception and experimentally demonstrate counter-propagating chiral states at the edge of a time-reversal-symmetric photonic waveguide structure. The pivotal step…
The optical modes of photonic structures are the so-called TE and TM modes which bring intrinsic spin-orbit coupling and chirality to these systems. This, combined with the unique flexibility of design of the photonic potential, and the possibility to mix photon states with excitonic resonances, sensitive to magnetic field and interactions, allows to achieve many phenomena, often analogous to other solid state systems. In this contribution, we review in a qualitative and comprehensive way several of these realizations, namely the optical spin Hall effect, the creation of spin currents protecte…
Unconventional Weyl points (WPs), carrying topological charge 2 or higher, possess interesting properties different from ordinary charge-1 WPs, including multiple Fermi arcs that stretch over a large portion of the Brillouin zone. Thus far, such WPs have been observed in chiral materials and acoustic metamaterials, but there has been no clean demonstration in photonics in which the unconventional photonic WPs are separated from trivial bands. We experimentally realize an ideal symmetry-protected photonic charge-2 WP in a three-dimensional topological chiral microwave metamaterial. We use field…
Emergence of Propagating Exciton-Polaritons in Hybrid Waveguide-van der Waals Heterostructures
Institute of Physics, University of Rostock（罗斯托克大学物理研究所）；Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik (FBH)（费迪南德·布劳恩研究所，莱布尼茨高频技术研究所）；Research Center for Materials Nanoarchitectonics, NIMS（日本物质材料研究机构纳米结构材料研究中心）；Research Center for Electronic and Optical Materials, NIMS（日本物质材料研究机构电子光学材料研究中心）
We proposed and demonstrated a scheme of surface emitting circularly polarized light source by introducing strong imbalance between left- and right-circularly polarized vacuum fields in an on-waveguide chiral grating structure. We observed circularly polarized spontaneous emission from InAs quantum dots embedded in the wave guide region of a GaAs-based structure. Obtained degree of polarization reaches as large as 25% at room temperature. Numerical calculation visualizes spatial profiles of the modification of vacuum field modes inside the structure with strong circular anisotropy.
The ability to engineer photon emission and photon scattering is at the heart of modern photonics applications ranging from light harvesting, through novel compact light sources, to quantum-information processing based on single photons. Nanophotonic waveguides are particularly well suited for such applications since they confine photon propagation to a 1D geometry thereby increasing the interaction between light and matter. Adding chiral functionalities to nanophotonic waveguides lead to new opportunities enabling integrated and robust quantum-photonic devices or the observation of novel topo…
Observations of thermally driven transverse vibration of a photonic crystal waveguide (PCW) are reported. The PCW consists of two parallel nanobeams with a 240 nm vacuum gap between the beams. Models are developed and validated for the transduction of beam motion to phase and amplitude modulation of a weak optical probe propagating in a guided mode (GM) of the PCW for probe frequencies far from and near to the dielectric band edge. Since our PCW has been designed for near-field atom trapping, this research provides a foundation for evaluating possible deleterious effects of thermal motion on o…
The realization of a quantum interface between a propagating photon used for transmission of quantum information, and a stationary qubit used for storage and manipulation, has long been an outstanding goal in quantum information science. A method for implementing such an interface between dissimilar qubits is quantum teleportation, which has attracted considerable interest not only as a versatile quantum-state-transfer method but also as a quantum computational primitive. Here, we experimentally demonstrate transfer of quantum information carried by a photonic qubit to a quantum dot spin qubit…
Two-electron charged self-assembled quantum dot molecules exhibit a decoherence-avoiding singlet-triplet qubit subspace and an efficient spin-photon interface. We demonstrate quantum entanglement between emitted photons and the spin-qubit after the emission event. We measure the overlap with a fully entangled state to be $69.5\pm2.7\,\%$, exceeding the threshold of $50\,\%$ required to prove the non-separability of the density matrix of the system. The photonic qubit is encoded in two photon states with an energy difference larger than the timing resolution of existing detectors. We devise a n…
We introduce a theoretical formalism to describe disorder-induced extrinsic scattering in slow-light photonic crystal waveguides. This work details and extends the optical scattering theory used in a recent \emph{Physical Review Letter} [M. Patterson \emph{et al.}, \emph{Phys. Rev. Lett.} \textbf{102}, 103901 (2009)] to describe coherent scattering phenomena and successfully explain complex experimental measurements. Our presented theory, that combines Green function and coupled mode methods, allows one to self-consistently account for arbitrary multiple scattering for the propagating electric…
A periodically driven quantum Hall system in a fixed magnetic field is found to exhibit a series of phases featuring anomalous edge modes with the "wrong" chirality. This leads to pairs of counter-propagating chiral edge modes at each edge, in sharp contrast to stationary quantum Hall systems. We show that the pair of Floquet edge modes are protected by the chiral (sublattice) symmetry, and that they are robust against static disorder. The existence of distinctive phases with the same Chern and winding numbers but very different edge state spectra points to the important role played by symmetr…
Nonequilibrium Floquet topological phases due to periodic driving are known to exhibit rich and interesting features with no static analogs. Various known topological invariants usually proposed to characterize static topological systems often fail to fully characterize Floquet topological phases. This fact has motivated extensive studies of Floquet topological phases to better understand nonequilibrium topological phases and to explore their possible applications. Here we present a theoretically simple Floquet topological insulating system that may possess an arbitrary number of counter-propa…
We investigate the helically-propagating edge states associated with pseudo-Landau levels in strained honeycomb lattices. We exploit chiral symmetry to derive a general criterion for the existence of these propagating edge states in the presence of only nearest-neighbour hoppings and we verify our criterion using numerical simulations of both uni-axially and trigonally strained honeycomb lattices. We show that the propagation of the helical edge state can be controlled by engineering the shape of the edges. Sensitivity to chiral-symmetry-breaking next-nearest-neighbour hoppings is assessed. Ou…
Topological insulators host topology-linked boundary states, whose spin and charge degrees of freedom could be exploited to design topological devices with enhanced functionality. We experimentally observe that dissipationless chiral edge states in a spin-orbit coupled anomalous Floquet topological phase exhibit topological spin texture on boundaries, realized via a two-dimensional quantum walk. Our experiment shows that, for a walker traveling around a closed loop along the boundary in real space, its spin evolves and winds through a great circle on the Bloch sphere, which implies that edge-s…
