Diffraction efficiency

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

Electron-beam writing system and its application to large and high-density diffractive optic elements.

Abstract: An electron-beam writing system that is characterized by a stationary electron beam and a continuously spinning table is proposed and developed for diffractive optic elements with axisymmetric patterns. This system allows us to fabricate continuously concentric or radialized high-density microgratings with effective areas over the electron-beam deflection limits. For a fine electron-dose distribution, we adopted multiple-revolution writing and electron-beam modulation. Several test gratings, including a rotary encoder disk with a 1.57-μm grating pitch and a 15-mm diameter and a blazed micro-Fresnel lens with a 4.5-mm diameter and a N.A. of 0.45, are successfully demonstrated with real-time data processing.

Patterning Liquid-Crystal Alignment for Ultrathin Flat Optics.

Abstract: Liquid-crystal (LC)-based ultrathin flat optical elements (FOEs) exhibit several attractive properties, such as a high degree of optical tunability, strong polarization selectivity, nearly 100% diffraction efficiency, and a simple fabrication process. Investigating the alignment patterning of LC-FOEs to diversify their performance has attracted broad interest in the optics field. In this mini-review, we start from the photoalignment (PA) process and then dive into device structures and performances. By generating and recording the desired polarization fields on the PA layer, the LC molecules will follow the recorded patterns and establish the phase profiles for different functionalities, such as gratings and lenses. Because of the polarization dependency, LC-FOEs have found useful applications in near-eye displays. Understanding the interactions between the PA mechanism and LC molecules helps to optimize the device performance for novel optical systems.

Plane gratings for high-resolution grazing-incidence monochromators: holographic grating versus mechanically ruled varied-line-spacing grating

Abstract: Comparative studies have been made on the holographic plane grating and the ruled varied-line-spacing (VLS) plane grating designed for two kinds of objective Monk–Gillieson type high-resolution grazing incidence monochromator, I and II. The ray-traced performance of monochromator types I and II on a synchrotron radiation beam line was evaluated in terms of resolving power and spectral purity by the introduction of new concepts of effective Gaussian line and purity profiles. The resolving power defined on the basis of the effective Gaussian profile is consistent with the spectral purity of the beam emerging from the exit slit and is more realistic as compared with those defined in the conventional manner, especially when spectral images have asymmetric profiles. It is concluded that holographic plane gratings recorded with a spherical and an aspheric wave front are capable of providing high resolution with high spectral purity and are fully interchangeable with the corresponding ruled VLS plane gratings. This interchangeability provides more flexibility for users in choosing a proper grating for a high-resolution grazing incidence monochromator of the Monk-Gillieson type.

Optical self-alignment system

Abstract: An optical self-alignment system comprises a laser source (12). a substrate (A) with a first diffraction grating for receiving laser beams (L) from the laser source (12), a substrate (B) with a second diffraction grating disposed within Fresnel zone of the first diffraction grating (A), and a photoelectric detector (C) for detecting Fraunhofer diffraction ray of Oth order by the second diffraction grating (B). In order to adjust the relative position between the two substrates (A,B) in orthogonal directions to the laser beams (L) at high accuracy, the first (A) and second (B) diffraction gratings are provided with two groups of combined diffraction gratings so that phase difference of 180° is produced in the Moire signals, maximum displacement point of Moire signal is detected with respect to relative position displacement of the diffraction gratings, and the substrates (A,B) are positioned at maximum intensity displacement of two groups of the Moire signals.

Diffraction properties of two-dimensional photonic crystals

Abstract: We show that the envelope of the diffraction efficiency of a two-dimensional photonic crystal can exhibit spectral regions of very small diffraction efficiency (<5×10−3), while in other regions, the diffraction efficiency is near unity. The experimental results on higher bands of hexagonal, silicon-based photonic crystals agree well with corresponding numerical calculations and highlight the prominent role of the surface termination, an aspect which cannot be described by the photonic band structure alone. We speculate about possible applications of such additional spectral filters in Raman and photoluminescence spectroscopy.