Metasurfaces are two-dimensional structures enabling complete control on light amplitude, phase, and polarization. Unlike plasmonic metasurfaces, silicon structures facilitate high transmission, low losses, and compatibility with existing semiconductor technologies. We experimentally demonstrate two examples of high-efficiency polarization-sensitive dielectric metasurfaces with 2π phase control in transmission mode (45% transmission efficiency for the vortex converter and 36% transmission efficiency for the beam steering device) at telecommunication wavelengths. Silicon metasurfaces are poised to enable a versatile platform for the realization of all-optical circuitry on a chip.
Recent developments in the field of metamaterials have revealed unparalleled opportunities for “engineering” space for light propagation; opening a new paradigm in spin- and quantum-related phenomena in optical physics. Here we show that unique optical properties of metamaterials (MMs) open unlimited prospects to “engineer” light itself. We propose and demonstrate for the first time a novel way of complex light manipulation in few-mode optical fibers using optical MMs. Most importantly, these studies highlight how unique properties of MMs, namely the ability to manipulate both electric and magnetic field components of electromagnetic (EM) waves, open new degrees of freedom in engineering complex polarization states of light at will, while preserving its orbital angular momentum (OAM) state. These results lay the first steps in manipulating complex light in optical fibers, likely providing new opportunities for high capacity communication systems, quantum information, and on-chip signal processing.
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
Orbital angular momentum (OAM) beams may create a new paradigm for the future classical and quantum communication systems. A majority of existing OAM beam converters are bulky, slow, and cannot withstand high powers. Here, we design and experimentally demonstrate an ultra-fast, compact chalcogenide-based all-dielectric metasurface beam converter which has the ability to transform a Hermite–Gaussian (HG) beam into a beam carrying an OAM at near infrared wavelength. Depending on the input beam intensity, the topological charge carried by the output OAM beam can be switched between positive and negative. The device provides high transmission efficiency and is fabricated by a standard electron beam lithography. Arsenic trisulfide (As 2 S 3 ) chalcogenide glass (ChG) offers ultra-fast and large third-order nonlinearity as well as a low two-photon absorption coefficient in the near infrared spectral range.
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