Diffraction efficiency

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

Light diffraction from volume phase holograms in electrooptic photorefractive crystals

Abstract: Basic peculiarities of anisotropic volume phase holograms in photorefractive electrooptic crystals of LiNbO3 and Bi12SiO20 types are discussed. General methods of analysis of diffraction phenomena in these media are considered. Theoretical calculations of diffraction efficiency and polarization of the diffracted beam obtained in dynamic approximation for a strongly birefringent as well as a cubic crystal are presented. Original experimental results on the amplitude and polarization of light diffracted from holograms in LiNbO3:Fe and Bi12SiO20 crystals are in good agreement with the theoretical considerations.

Binary Lenses For Use At 10.6 Micrometers

Abstract: By combining advances in lithography and electromagnetic grating theory, we recently have demonstrated the ability to produce highly efficient binary gratings and binary lenses for use at 10.6 um. Electromagnetic theory predicts that binary gratings with the proper parameters can achieve a first-order diffraction efficiency of nearly 100%. If the periodicity of the grating is on the order of the radiation wavelength, all of the orders become evanescent except for the zero and positive first orders. By choosing the depth-to-period ratio and duty cycle properly, the zero order can be suppressed, placing virtually all of the incident radiation into the first diffracted order. Theoretical calculations have been done only for constant period gratings. However, assuming a lens pattern to be a minor perturbation of a grating, we succeeded in producing an f/5 binary lens with a diffraction efficiency of 96% at 10.6 um. Furthermore, because of the high efficiency of these elements, it becomes practical to consider using more than a single diffractive element in a system. We have constructed a simple afocal telescope from two binary lenses. The telescope has a 2 in. entrance aperture and a magnification of 5. A final point to be considered is the wavefront quality of these elements. Electron beam machines, which are used to write the lens patterns, are designed to draw the pattern in a raster fashion. This quantization sets a limit on the quality of the lens pattern.

Planar-optic-disk pickup with diffractive micro-optics.

Abstract: An integrated optical-disk pickup with a diffractive planar micro-optic system is proposed. In this device, the beam follows a zigzag optical path inside a glass substrate that is used as a light guide. To fabricate off-axis diffractive optical elements, we have recently developed an electron-beam writing system with a curve-pattern generator. It is demonstrated that a transmission off-axis objective microlens, a reflection twin-focusing beam splitter, and reflection layers were integrated on a glass substrate, and such a diffractive planar micro-optic system exhibited an excellent focusing performance and operated for focus-error signal detection, as designed.

Replication technology for holograms and diffractive optical elements : Holography I

Abstract: Replication technologies such as embossing, molding and casting are highly attractive for the fabrication of surface relief hologram and diffractive optical element (DOE) microstructures. They have very high resolution, typically in the nanometer range, and allow the fabrication of a large area, complex microstructure by low cost, high volume industrial production processes. Their use is already well established for gratings, white light holograms, and diffractive foil with typical relief structure shallower than 1 μm and the extension to the fabrication of deeper and higher aspect ratio microstructure is underway. The combination of replication technology with other processes such as dry etching and thin film coating can also offer new possibilities in the design of DOEs suitable for mass production. Replication is expected to become a key technology for the microfabrication of a wide range of DOEs in the future. We review the major hologram and DOE replication techniques and describe recent work and results.