Direct Generation of Tunable Orbital Angular Momentum Beams in Microring Lasers with Broadband Exceptional Points

Abstract

Non-Hermitian exceptional points (EPs) represent a special type of degeneracy where not only the eigenvalues coalesce, but also the eigenstates tend to collapse on each other. Recent studies have shown that, in the presence of an EP, light–matter interactions are profoundly modified, leading to a host of unexpected optical phenomena ranging from enhanced sensitivity to chiral light transport. Here we introduce a family of unidirectional resonators based on a novel type of broadband exceptional points. In active settings, the resulting unidirectionality exhibits resilience to perturbations, thus, providing a robust and tunable approach for directly generating beams with distinct orbital angular momenta (OAM). This work could open up new possibilities for manipulating OAM degrees of freedom in applications pertaining to telecommunications and quantum information sciences, while at the same time may expand the notions of non-Hermiticity in the orbital angular momentum space.

Focused vortex-beam generation using gap-surface plasmon metasurfaces

“…Importantly, this approach has been extended to realize a dual-focal metasurface with distinctly engineered intensity profiles by using segmented metasurfaces, where an orthogonalpolarized beam with Gaussian-distributed intensity and a vortex-beam with intensity singularity have been experimentally implemented. Owing to the compactness and remarkable multifunctional performance, such metasurfaces enable easy integration with the existing photonic technology and sophisticated application in plasmonic and photonic circuits and systems [28][29][30][31]. and Grant No.…”

Coherent Perfect Absorption Laser Points in One-Dimensional Anti-Parity–Time-Symmetric Photonic Crystals

“…The spatial GH shift is highly sensitive to the refractive index of dielectric and angular frequency of incident light, as shown in Figure 6b-d around the CPA-LP. However, the applications in sense at the exceptional point appear to be rather challenging, such as the effect of fluctuations and noise [67][68][69].…”

Topological states at exceptional points

“…Model and discussion-Let us start with a semi-infinite photonic lattice made of coupled microring lasers each capable of vector vortex generation. Such microrings can be fabricated utilizing breaking rotation symmetry and asymmetric loss using an S-shape waveguide with adiabatically tapered ends embedded at the center of a microring [16]. A tapered S-shaped waveguide makes it possible to create a unidirectional coupling between two adjacent microrings by breaking the time-reversal symmetry and chirality.…”

“…Using the coupled-mode theory, we can write the modal field amplitudes in the clockwise and counterclockwise directions (E CW , E CCW ) T m = (ψ,φ) T m (T stands for transpose) at the m(∈ odd)th microring as [16]:…”

“…Recently an effort has been made to reduce the size of the optical structures used to create orbital angular momentum (OAM) beams and make it possible to generate OAM on chip-scale [16][17][18][19][20]. Despite all these achievements in the creation of OMA beams, there is no study on the dynamics of OAM beams in discrete lattices.…”