Diffraction efficiency

About: Diffraction efficiency is a research topic. Over the lifetime, 10320 publications have been published within this topic receiving 158298 citations.

Design of diffractive phase elements for beam shaping: hybrid approach

Abstract: Hybrid approaches that combine genetic algorithms (GA’s) with traditional gradient-based local search techniques are proposed for the optimization design of diffractive phase elements (DPE’s) for laser beam shaping. These hybrid methods exploit the global nature of the GA’s as well as the local improvement capabilities of the gradient-based local search techniques and will perform a more improved search in comparison with each of the individual approaches. The incorporated local search technique that we used here is the Davidon–Fletcher–Powell method. A cost function that can directly control the performance of the final solutions is also used. By performing the DPE design with different desired diffraction efficiencies, we obtain a set of results that approximately reflect the trade-off between the design objectives, namely, signal-to-noise ratio (SNR) and diffraction efficiency. Reasonable solutions can be chosen on the basis of the knowledge of the problem. Simulation computations are detailed for two rotationally symmetric beam-shaping systems, in which an incident Gaussian profile laser beam is converted into a uniform beam and a zero-order Bessel beam. Numerical results demonstrate that the proposed algorithm is highly efficient and robust. DPE’s that have high diffraction efficiency and excellent SNR can be achieved by using the algorithm that we propose.

Visualization of low-frequency liquid surface acoustic waves by means of optical diffraction

Abstract: A technique for low-frequency liquid surface acoustic wave (LFLSAW) visualization is developed based on the light diffraction. The technique is capable of real-time characterization of wave amplitude, and it produces highly visible stationary diffraction pattern for a low-frequency wave (a few hundreds Hz). The disappearance of the zero-order diffraction fringe, which corresponding to the 100% diffraction efficiency, was experimentally observed for using this technique. The correlation of the diffraction pattern to the LFLSAW amplitude is also experimentally established.

Method and apparatus for profiling surfaces using diffractive optics which impinges the beams at two different incident angles

Abstract: Optical system for measuring surface topography, comprised of a light source (30), a diffractive optical assembly (70, 72, 73) comprised of two or more diffraction gratings, holograms or like diffractive optics (120, 130; 122, 132; 123, 133), electronic detection means and digital signal processing means (10, 110) for determining surface height from interference data. The diffractive optical assembly (70, 72, 73) divides the incident light into two beams (150, 160; 152, 162; 153, 163), which subsequently impinge upon the object (20) at the same place on The object surface (70) but at two different angles of incidence. After reflection from the object surface, the beams pass separately back through the diffractive optical assembly (70, 72, 73), after which they combine once again and form an interference pattern representative of the surface topography. The equivalent wavelength of the resultant interference pattern is much greater than the illumination wavelength.

Design and analysis of broadband high-efficiency pulse compression gratings

Abstract: We report on two effective methods, multiparameter optimization and local optimization combined with the diffraction bandwidth merit function, to design a broadband pulse compression grating (PCG), and we present broadband, high-efficiency PCGs based on both the multilayer dielectric grating (MDG) and metal-multilayer dielectric grating (MMDG) models. For MDG, the average diffraction efficiency is higher than 97.5% for TE polarization light over the 100nm bandwidth centered at 800nm. Moreover, a novel multilayer structure, which comprises higher index material in the high-reflectivity mirror and relatively lower index material on top, is first proposed to yield higher average efficiency, broader bandwidth, and excellent fabrication tolerance. For MMDG, it exhibits an ultrabroadband top-hat diffraction spectrum with average efficiency exceeding 97% over the 200nm wavelength wide centered at 1053nm. In addition, the MMDG structure, which has the best tolerance for grating fabrication, is determined by investigating characteristics of MMDGs with different thin-film structures.

Electrochemically tunable surface-plasmon-enhanced diffraction gratings and their (bio-)sensing applications

Abstract: Electrochemistry was combined with surface-plasmon-enhanced diffraction (ESPD) to investigate a redox-switchable polymer grating and its (bio-)sensing applications. Patterned arrays of polyaniline (PANI)/poly(styrenesulfonate) (PSS) were fabricated by the combination of electropolymerization and micromolding in capillaries (MIMIC) and were used as an optical grating for surface-plasmon-enhanced diffraction experiments. The diffraction efficiency (DE) could be tuned by changes in the applied potential, and by changes in the pH of the surrounding solution (dielectric medium). The response of the DE to the pH depends strongly on the redox state of the PANI/PSS grating. If the polymer grating is mainly in its reduced state, the DE shows a linear dependence on the pH. The DE of the PANI/PSS grating can also be modulated by an electrocatalytic event: by keeping PANI/PSS in its oxidized form, the addition of β-nicotinamide adenine dinucleotide (NADH) increases the DE with the increase of NADH concentration, whi...