Pure angular momentum generator using a ring resonator

High-efficiency one-dimensional metalens for 3D focusing

We demonstrate a high-efficiency on-chip one-dimensional metalens for three-dimensional (3D) light focusing. The metalens consists of a one-dimensional dielectric nano-antenna array, which scatters the evanescent wave of a nano-waveguide into free space and focuses this scattered light into a 3D ring. The corresponding phase profile of the metalens is controlled by the relative locations of antennas in the array. Through antenna-waveguide distance optimization, the designed metalens only scatters 1.5% of propagation light into free space and 55% of the scattered energy is focused into the 3D ring. When we use the antennas with an optimized shape, 50.18% of the focused energy is concentrated in a circular arc of the ring, which subtends an angle of 48°. This high-efficiency on-chip one-dimensional metalens is promising for non-invasive optical signal detection in photonic integrated chips.

Photonic lantern broadband orbital angular momentum mode multiplexer

Optical vortex beams that carry orbital angular momentum (OAM), also known as OAM modes, have attracted considerable interest in recent years as they can comprise an additional degree of freedom for a variety of advanced classical and quantum optical applications. While canonical methods of OAM mode generation are effective, a method that can simultaneously generate and multiplex OAM modes with low loss and over broad spectral range is still in great demand. Here, via novel design of an optical fiber device referred to as a photonic lantern, where the radial mode index ("m") is neglected, for the first time we demonstrate the simultaneous generation and multiplexing of OAM modes with low loss and over the broadest spectral range to date (550 nm). We further confirm the potential of this approach to preserve the quality of studied OAM modes by fusion splicing the end-facet of the fabricated device to a delivery ring-core fiber (RCF).

Integrated photonic emitter with a wide switching range of orbital angular momentum modes

Due to the nature of infinite dimensionality, the orbital angular momentum (OAM) has been considered as a new degree of freedom of light and widely expanded the scopes of substantial optical applications such as optical telecommunication, quantum information, particle manipulation and imaging. In recent years, the integrated photonic OAM emitters have been actively investigated due to both compactness and tunability. Essentially, the number of available OAM modes by dynamic switching should be large enough so that the dimensionality of OAM could be explored as much as possible. In this work, an integrated photonic emitter with a wide switching range of OAM modes is theoretically developed, numerically simulated, and experimentally verified. The independence of the micro-ring cavity and the scattering unit provides the flexibility to design the device and optimize the performance. Specifically, the dynamic switching of nine OAM modes (l = −4 ~ 4) with azimuthal polarization has been demonstrated by electrically controlled thermo-optic effect.

Cavity modes with optical orbital angular momentum in a metamaterial ring based on transformation optics

In this work, we theoretically study the cavity modes with transverse orbital angular momentum in metamaterial ring based on transformation optics. The metamaterial ring is designed to transform the straight trajectory of light into the circulating one by enlarging the azimuthal angle, effectively presenting the modes with transverse orbital angular momentum. The simulation results confirm the theoretical predictions, which state that the transverse orbital angular momentum of the mode not only depends on the frequency of the incident light, but also depends on the transformation scale of the azimuthal angle. Because energy dissipation inevitably reduces the field amplitude of the modes, the confined electromagnetic energy and the quality factor of the modes inside the ring are also studied in order to evaluate the stability of those cavity modes. The results show that the metamaterial ring can effectively confine light with a high quality factor and maintain steady modes with the orbital angular momentum, even if the dimension of the ring is much smaller than the wavelength of the incident light. This technique for exploiting the modes with optical transverse orbital angular momentum may provides a unique platform for applications related to micromanipulation.

Generation of vector beams in planar photonic crystal cavities with multiple missing-hole defects

We propose a novel method to generate vector beams in planar photonic crystal cavities with multiple missing-hole defects. Simulating the resonant modes in the cavities, we observe that the optical fields in each defect have different phase and polarization state distributions, which promise the compositions of vector beams by the scattered light from the defects. The far-field radiation patterns of the cavity modes calculated via the Sommerfeld diffraction theory present vector beams possessing hollow intensity profiles and polarization singularities. In addition, the extraction efficiencies of the vector beams from the cavities could be improved by modifying the air-holes surrounding the defects. This planar photonic crystal cavity-based vector beam generator may provide useful insights for the on-chip controlling of vector beams in their propagations and interactions with matter.