Observation of a Charge-2 Photonic Weyl Point in the Infrared

Observation of Quadratic (Charge‐2) Weyl Point Splitting in Near‐Infrared Photonic Crystals

“…To explain this observation, we perform a coupling analysis similar to refs. [16,40–43] which reveals that the relevant projected bands are nearly of either s‐ or p‐ character and hence couple selectively to light of these polarizations (see Supporting Information). This selective coupling results in the boundary of the projected bands, corresponding to bulk bands, appearing as sharp drops in the transmission of polarized light allowing for the observation of WPs despite the lack of a local bandgap.…”

“…Weyl materials have drawn significant interest over the last decade for their ability to support Weyl points (WPs), which are topologically protected degeneracies in 3D periodic systems. They have been examined in a wide range of physical systems such as conventional solids, [ 1–7 ] photonic systems, [ 8–18 ] acoustic systems, [ 19–22 ] cold atoms, [ 23,24 ] electric circuits, [ 25 ] and coupled resonator arrays. [ 26,27 ] In photonics, WPs are sought for a range of applications such as designing large‐volume single‐mode lasers [ 28 ] and mediating long‐range interactions between quantum emitters, [ 29,30 ] and as such they have been realized in a variety of optical and photonic systems [ 8–18 ] spanning orders of magnitude in wavelength.…”

“…They have been examined in a wide range of physical systems such as conventional solids, [ 1–7 ] photonic systems, [ 8–18 ] acoustic systems, [ 19–22 ] cold atoms, [ 23,24 ] electric circuits, [ 25 ] and coupled resonator arrays. [ 26,27 ] In photonics, WPs are sought for a range of applications such as designing large‐volume single‐mode lasers [ 28 ] and mediating long‐range interactions between quantum emitters, [ 29,30 ] and as such they have been realized in a variety of optical and photonic systems [ 8–18 ] spanning orders of magnitude in wavelength. WPs are quantized sources and sinks of Berry curvature in momentum space, analogous to magnetic monopoles.…”

“…[ 12,32,33 ] In photonics, quadratic WPs were predicted [ 14 ] and observed in all‐dielectric woodpile‐like structures. [ 16 ] Such structures exhibit several additional symmetries and therefore provide an ideal platform for tuning the locations of linear WPs that can form from splitting a quadratic WP due to symmetry breaking. [ 33,34 ] This tunability of WPs could be of importance in the realization of 3D large‐volume, single‐mode lasing devices that rely on the vanishing photonic density of states at frequency‐isolated linear WPs.…”

A Review of Topological Semimetal Phases in Photonic Artificial Microstructures

“…Charge-2 Weyl points can exist in a chiral woodpile photonic crystal with screw symmetry [57]. Recently, a parity-breaking chiral woodpile photonic crystal fabricated by two-photon polymerization was constructed to observe a charge-2 Weyl point in the mid-infrared regime [58]. Each layer rotates 45 + next to the neighboring layer, as shown in Figure 3E.…”