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.

Binary gratings with increased efficiency

Abstract: Coupled-wave analysis is used to design binary gratings with high efficiencies (70-80%). The binary designs have grating periods greater than one wavelength but use subwavelength structures within each period in order to achieve high efficiency.

High resolution imagery systems and methods

Abstract: The current limits of resolution of multi-element optical systems are exceeded by reducing the number of elements while introducing at the critical aperture a blazed transmission grating having grating rings of low bending power defined by multiple plateaus. By illuminating the optical train with monochromatic light that constitutes a multiplicity of distributed sources having a substantial temporal coherence but spatial incoherence and by varying the slopes and widths of the grating rings, local phase delays are introduced that adjust aberrations in the optical system, providing an aligned composite wavefront. The system and method may be used for presenting an image, as for a wafer stepper, or for viewing an image, as in a microscope.

Zero-reflectivity high spatial-frequency rectangular-groove dielectric surface-relief gratings.

Abstract: Using rigorous coupled-wave analysis, high spatial-frequency rectangular-groove surface-relief phase gratings are shown to be capable of exhibiting zero reflectivity. Thus these corrugated surfaces may act as antireflection coatings in a variety of applications. The diffraction characteristics of rectangular-groove surface-relief gratings are presented for several ratios of incident wavelength to grating period as a function of filling factor, groove depth, angle of incidence, and polarization. The conditions for zero reflectivity are identified. Results are compared with single-homogeneous-layer approximate theory results. In the limit of long wavelengths for an electromagnetic wave in a dielectric of refractive index n1 normally incident on a dielectric of index n2, it is determined that for antireflection behavior, the grating groove depth should be λ/4(n1n2)1/2 and the filling factor should be n1/(n1 + n2) or n2/(n1 + n2) for the electric field perpendicular or parallel to the grating vector, respectively. The spectral and angular responses of these gratings are like those of single-homogeneous-layer antireflection coatings. These gratings also exhibit birefringent retardation.

Sub-Wavelength Grating Lenses With a Twist

Abstract: Dielectric high-contrast sub-wavelength grating (SWG) structures have received much attention in recent years, offering a new paradigm for the integration of optical systems. Their nanoscale resonant properties can result in a complex and unintuitive far-field behavior that, if carefully crafted, allows the full control of the optical phase front from a thin sub-wavelength planar layer. To date, experimental demonstrations of these new devices have only been realized with polarized light in a reflective mode, greatly limiting their use for practical systems. In this letter, we demonstrate a highly efficient, sub-wavelength thick, transmissive grating lens configuration using symmetrical resonant posts to achieve polarization-independent operation. Our transmissive SWG lenses are easily fabricated using low-cost scalable semiconductor process technology. To illustrate their performance, we demonstrate the generation of high-order orbital angular momentum beams and their use in an optical mode-isolator application that achieves a suppression ratio of over 25 dB.

X-ray wavefront analysis and optics characterization with a grating interferometer

Abstract: We present an interferometric method to measure the shape of a hard-x-ray wavefront. The interferometer consists of a phase grating as a beam splitter and an absorption grating as a transmission mask for the detector. The device can be used to measure wavefront shape gradients corresponding to radii of curvature as large as several dozens of meters, with a lateral resolution of a few microns. This corresponds to detected wavefront distortions of approximately 10−12m or λ∕100. The device was used with 12.4 keV x rays to measure the slope error and height profile of an x-ray mirror. Surface slope variations with periods ranging from less than 1 mm to more than 1 m can be detected with an accuracy better than 0.1μrad.