Diffraction grating

About: Diffraction grating is a research topic. Over the lifetime, 24884 publications have been published within this topic receiving 372437 citations. The topic is also known as: grating.

Geometric metasurface fork gratings for vortex-beam generation and manipulation

Abstract: In recent years, optical vortex beams possessing orbital angular momentum have received much attention due to their potential for high-capacity optical communications. This capability arises from the unbounded topological charges of orbital angular momentum (OAM) that provide infinite freedoms for encoding information. The two most common approaches for generating vortex beams are through fork diffraction gratings and spiral phase plates. While realization of conventional spiral phase plate requires complicated 3D fabrication, the emerging field of metasurfaces has provided a planar and facile solution for generating vortex beams of arbitrary orbit angular momentum. Among various types of metasurfaces, the geometric phase metasurface has shown great potential for robust control of light- and spin-controlled wave propagation. Here, we realize a novel type of geometric metasurface fork grating that seamlessly combine the functionality of a metasurface phase plate for vortex-beam generation, and that of a linear phase gradient metasurface for controlling the wave-propagation direction. The metasurface fork grating is therefore capable of simultaneously controlling both the spin and the orbital angular momentum of light.

Efficient diffractive phase optics for electrons

Abstract: Electron diffraction gratings can be used to imprint well-defined phase structure onto an electron beam. For example, diffraction gratings have been used to prepare electron beams with unique phase dislocations, such as electron vortex beams, which hold promise for the development of new imaging and spectroscopy techniques for the study of materials. However, beam intensity loss associated with absorption, scattering, and diffraction by a binary transmission grating drastically reduces the current in the beam, and thus the possible detected signal strength it may generate. Here we describe electron-transparent phase gratings that efficiently diffract transmitted electrons. These phase gratings produce electron beams with the high current necessary to generate detectable signal upon interaction with a material. The phase grating design detailed here allows for fabrication of much more complex grating structures with extremely fine features. The diffracted beams produced by these gratings are widely separated and carry the designed phase structure with high fidelity. In this work, we outline a fabrication method for high-efficiency electron diffraction gratings and present measurements of the performance of a set of simple prototypical gratings in a transmission electron microscope. We present a model for electron diffraction gratings that can be used to optimize the performance of diffractive electron optics. We also present several new holograms that utilize manipulation of phase to produce new types of highly efficient electron beams.

Miniaturized spectrometer employing planar waveguides and grating couplers for chemical analysis.

Abstract: Polymeric and metal oxide planar waveguides were used to demonstrate the potential of a miniature spectrometer. Multiwavelength light was transmitted through the substrate and coupled into the waveguide through a diffraction grating located at the substrate/waveguide interface. A second diffraction grating spatially dispersed the light propagated through the waveguide into component wavelengths for rapid analysis with a photodiode array detector. These results suggest that planar waveguides can be used to perform attenuated total internal reflection measurements in the visible and near-IR regions for chemical analysis of weak vibrational overtones and combination modes with effective path lengths of several millimeters.

Experimental evidence of the inverse Smith–Purcell effect

Abstract: Interest in the development of laser-driven linacs has been stimu-lated recently by the advent of the high-power lasers. The use of a laser to accelerate charged particles was first proposed by K. Shimoda in 19621. He noticed that high values of acceleration per metre (acceleration gradient) could be obtained with an intense electric field in the output of a high-power laser. The inverse Smith–Purcell (ISP) effect proposed by us2 is a candidate for laser-driven linacs with a metallic grating as an interaction circuit. In 1953 Smith and Purcell demonstrated that light is emitted when a high-voltage electron beam moves parallel and close to a metallic optical diffraction grating in a direction perpendicular to the grating rulings3. The dispersion relationship is a synchronous condition between the electrons and the wave on the grating. Therefore, the inverse Smith-Purcell effect (ISP), or the extended interaction between electrons and an incident light wave should occur when the same relation is satisfied between the electrons and the incident wave (Fig. 1)2. Lawson pointed out4 that this effect would fail to accelerate relativistic particles. This difficulty was solved by Palmer5, who showed that acceleration is possible either if the particles travel skew to the grating lines, or if the radiation is falling at a skew angle onto the grating. Several authors have described possibilities for producing a grating linac (ISP effect) with accelerating field of a few GeV m−1 in the infrared or optical wave region6. Here we report the first observational evidence for this effect using a submillimetre-wave laser as a driving source. The experimental results give good agreement with theoretical predictions.

Large flexible nanowire grid visible polarizer made by nanoimprint lithography

Abstract: 117 and 150nm pitch polymer gratings were successfully fabricated on plastic substrate over large area by nanoimprint lithography. Nanowire-grid polarizers were made by depositing Al on the sidewalls of the gratings at oblique angles. The effects of grating period, grating linewidth, Al depth, and thickness were studied in detail. Excellent contrast (∼1000:1) and high transmittance (80%–90%) (without antireflection coating) at the wavelength of 500nm and above were demonstrated.