The full vector nature of light provides an additional degree of freedom, namely, the angular momentum (AM) which includes both spin angular momentum (SAM) and orbital angular momentum (OAM). This full AM space holds a great promise for multi-dimensional high capacity data modulation and multiplexing in both classical and quantum regimes, confronting the exploding demands for information. The dynamical generation and control of optical vortices carrying SAM-OAM states mainly rely on tabletop optics. Vortex microlasers offer more compact and robust solution. However, the recently developed vortex microlasers either lack reconfigurability or require extremely low temperature operation environment, limiting the potential real world applications. By harnessing the properties of total angular momentum conservation, spin-orbit interaction and optically controlled non-Hermitian symmetry breaking, we demonstrate an on-chip integrated SAM-OAM-tunable vortex microlaser at room temperature, providing up to 5 different SAM-OAM states at a single telecom wavelength. Moreover, by utilizing fast transient optical gain dynamics in semiconductor materials, we experimentally demonstrate the ultrafast control of fractional OAM emission continuously from 0 to +2 in less than 100 ps. Our toolbox of flexible generation and control of vortex emission at a single wavelength provides a feasible route for the development of the next generation of multi-dimensional high capacity information system in both classical and quantum regimes.
The landmark discovery of photonic topological insulators has opened a unique route for disorder-immune light transport with unprecedented possibilities of practical applications. Flexible reconfiguration of topological light pathways can enable a completely new paradigm for high-density photonics routing, sustaining the growing demand for data capacity. By strategically interfacing non-Hermitian and topological physics, we demonstrate arbitrary robust light steering in reconfigurable non-Hermitian junctions, where novel chiral non-Hermitian topological states can propagate at an interface of the gain and loss domains. In contrast to previously studied topological states confined only at the static boundary/interface of the structure, the new non-Hermitian-controlled topological state can enable robust transmission links of light inside the bulk, fully utilizing the entire footprint of a photonic topological insulator.
The growing demand for high-capacity optical-transmission technologies sparked the growth of integrated and silicon photonics. Efficient on-chip manipulation of optical signals requires development of high-fidelity Y-junctions, photonic lanterns, mode filters and multiplexers, and interferometers.
The concept of supersymmetry (SUSY) originated in the fields of particle physics and enabled treatment for bosons and fermions on equal footing. Supersymmetry has expanded to quantum mechanics, and optics where it can be used, for instance, to design (de)multiplexing arrays of waveguides. To date, the majority of optical applications employed the unbroken SUSY that relates partners supporting the same set of eigenstates with the exception of the fundamental state.
We propose a design of a mode sorter made of fully iso-spectral permittivity profiles related by a continuous SUSY transformation in the broken regime. This ensures that the propagation constants of the all the modes to be sorted are preserved along the length of the device. As a result of this global matching of the propagation constants, the SUSY design allows for reduction of the modal cross-talk by two orders of magnitude compared with a standard asymmetric Y-splitter. Moreover, the SUSY mode sorter operates for both transverse-electric and transverse-magnetic light polarization, and it shows low losses and modal cross-talk over a broad wavelength range (1300-1700 nm). Compared with the previous SUSY based modes sorters, our design offers similar performance with an order of magnitude smaller sorter length and can separate modes without losing energy via radiative modes.
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