Reconfiguring structured light beams using nonlinear metasurfaces

Abstract

Ultra-compact, low-loss, fast, and reconfigurable optical components, enabling manipulation of light by light, could open numerous opportunities for controlling light on the nanoscale. Nanostructured all-dielectric metasurfaces have been shown to enable extensive control of amplitude and phase of light in the linear optical regime. Among other functionalities, they offer unique opportunities for shaping the wave front of light to introduce the orbital angular momentum (OAM) to a beam. Such structured light beams bring a new degree of freedom for applications ranging from spectroscopy and micromanipulation to classical and quantum optical communications. To date, reconfigurability or tuning of the optical properties of all-dielectric metasurfaces have been achieved mechanically, thermally, electrically or optically, using phasechange or nonlinear optical materials. However, a majority of demonstrated tuning approaches are either slow or require high optical powers. Arsenic trisulfide (As2S3) chalcogenide glass offering ultra-fast and large   3  nonlinearity as well as a low two-photon absorption coefficient in the near 2 and mid-wave infrared spectral range, could provide a new platform for the realization of fast and relatively low-intensity reconfigurable metasurfaces. Here, we design and experimentally demonstrate an As2S3 chalcogenide glass based metasurface that enables reshaping of a conventional Hermite-Gaussian beam with no OAM into an OAM beam at low-intensity levels, while preserves the original beam's amplitude and phase characteristics at high-intensity levels. The proposed metasurface could find applications for a new generation of optical communication systems and optical signal processing. The discovery of the fact that photons can carry an orbital angular momentum (OAM) opened a new area of optical physics and led to new understanding of a wide range of phenomena [1-4]. The OAM beams possess an azimuthal phase dependence of    il exp , where the angle  is the azimuthal coordinate and the quantized topological charge is denoted by l ℤ [5]. The OAM beams find important applications, including light-atom interactions [6], manipulation of microscopic objects [7], imaging [8,9], and optical communications [10][11][12][13]. Conventionally, OAM beams are generated using spiral phase plates or spatial light modulators [1]. These bulkoptics based devices suit laboratory experiments, but may not be compatible with integrated optics systems that require ultra-compact and flat optical components. Recently, first steps toward the realization of microscale, planar optical components based on liquid crystal technology (qplates) [14] and optical metasurfaces [16][17][18][19][20][21][22][23][24][25][26][27][28] have been made. While many of the first demonstrations of these devices were designed for generating OAM beams with a specific and fixed topological charge, reconfigurability is one of the desired characteristics allowing switching

Nonlinear Metasurface for Structured Light with Tunable Orbital Angular Momentum

“…In the second experiment, a small angle was introduced between the two beams, and the interference pattern contained fork-like fringes indicating the presence of the OAM, as shown in Figure 4h. In our previous work, the ChG hole metasurface converts an HG beam into an OAM beam by utilizing the guided resonances in a photonic crystal structure and overlapping two guided resonances to realize the desired phase shift in the even quadrants [32]. In contrast, in this experiment, the phase different between different quadrants of the fabricated metasurface is introduced by a single Mie-resonance and according to Figure 2, the resonance close to the wavelength of 1550 nm is the magnetic resonance.…”

“…Photonic metasurfaces attracted significant attention owing to their compact size, flat topology, and compatibility with existing integrated-optics fabrication methods . Recently, we have demonstrated the first step toward the realization of input-intensity-dependent optical metasurfaces capable of converting a beam with no OAM into an OAM-carrying beam in the near infrared range [32]. Here, we describe a nonlinear metasurface with the capability of switching between two opposite topological charges of OAM beams depending the intensity of the input beam.…”

Quantum Topological Photonics

“…There are numerous tuning measures using different properties of materials, including thermal [ 94,95 ] and electro‐optic modulators [ 96–98 ] and nonlinear index modulation techniques. [ 99–101 ] When tuning is realized, both the path entanglement and the frequency entanglement can be freely tuned as required, which will save considerable time and production costs and improve the photon‐pair generation efficiency.…”

Infrared dielectric metamaterials from high refractive index chalcogenides

“…For more details of the multipole analysis, refer to Supplementary Information section I. Such highorder modes supported by the metamaterial [28][29][30] enable strong light localization and confinement, which may be suitable for applications in nonlinear and laser optics, 31,32 Overall, the TI chalcogenide crystal family is an exceptionally versatile material platform for infrared applications based on high-index, low-loss dielectric metamaterial architectures, including ultrathin flat optical elements 33 , sub-diffraction light confinement and waveguiding 34 , and nonlinear optics 35 . Low-loss mid-IR metamaterials are also highly sought for enhanced sensing of molecular fingerprints based on strong light confinement.…”