Cylindrical computer-generated hologram for displaying 3D images.

This paper is dedicated to the development of synthesis methods for diffractive optical elements (DOEs) on non-planar surfaces. To form 3D images, a set of color 2D frames is used, visible to an observer from different observation points. The developed DOEs can be called a stereogram with a 360-deg view when the DOE is illuminated with white light. Methods are developed for computing the phase function of the DOE and are applicable to a wide range of convex surfaces. However, the manufacturing technology used limits this range to conical and cylindrical surfaces. The microrelief of the flat DOE is produced using electron-beam lithography. A video recorded using optical elements produced demonstrates the capabilities of the technologies developed. These DOEs can be used to protect brands against counterfeit.

Optical lithography with its 193nm technology is pushed to reach and shift its limits even further. There is strong demand on innovations in illumination part of exposure tools. Current illumination systems consisting of diffractive and refractive optical elements offer numerous benefits such as optimized laser beam shape with high homogeneity and high numerical aperture enabling high efficiency. LIMO's unique production technology is capable to manufacture free form surfaces on monolithic arrays larger than 250mm with high precision and reproducibility. Different kinds of intensity distributions with best uniformities or customized profiles have been achieved by using LIMO's refractive optical elements. Recently LIMO pushed the limits of this lens production technology and was able to manufacture first diffractive optical elements (DOE) based on continuous relief's profile. Beside for the illumination devices in lithography, DOEs find wide use in optical devices for other technological applications, such as optical communications and data processing. Up to now DOE designs follow the principle of phase diffraction gratings. Its diffraction structure with a periodic phase profile performs a superposition of beams with predefined energy ratios. Due to the application for high precise laser-beam shaping and beam splitting in optical technologies and optical fiber networks, number of grating orders is increased up to some tens or even hundreds. Classic lithographic technologies lead to quantized (step-like) profiles of diffractive micro-reliefs, which causes a decrease of beam splitter's diffractive efficiency. The newest development of LIMO's microlens fabrication technology allows us to make a step from free programmable microlens profiles to diffractive optical elements with high efficiency. Our first results of this approach are demonstrated in this paper. Diffractive beam splitters are presented. A special mathematical method is used to design diffractive optical elements with continuous surface profiles. Comparison between theoretical simulations and experimental results shows very good correlation.

Optical microsensors for fluid flow diagnostics

Recent advances in compression molding of glass optical elements for mass production offer the potential of extending this technology to elements with micro and nano scale features. In this research, glass diffractive optical elements (DOEs) with lateral features in the order of 10 µm and vertical height of 330 nm were fabricated using a fused silica glass mold and a special low Tg (glass transition temperature) glass material K-PG325. Molded DOEs were studied using an atomic force microscope (AFM) and scanning electron microscope (SEM) to evaluate the glass molding process capability. Optical testing of the molded DOEs was a further demonstration of the effectiveness of the molding process for high volume micro and diffractive optical component fabrication. The combination of two high-precision, high-volume processes, i.e., semiconductor batch process for optical mold making and glass molding for DOE replication, is an effective alternative manufacturing method for high-quality, low-cost optical components. The reported experiment is a detailed illustration of the glass molding process capability. With further process optimization a robust manufacturing process can be developed for mass production of diffractive and micro glass optical elements.

In recent years surface-relief Diffractive Optical Elements (DOEs), a specialized class of diffractive optical elements, have revolutionized design of optical systems and instruments. Surface-relief diffractive optical components improve performance of the existing optical systems and increase systems compactness and reliability. Surface-relief DOEs can be fabricated as multilevel binary optical elements, or as continuous surface-relief optical elements. A surface-relief DOE is being designed such that incident light interacts with the topography of the surface-relief microstructure including the size and shape characteristics of surface profile features such as indentations and projections as well as their dimensional relationship, to perform a desired optical function. Binary optical elements are being made by the same microlithographic and ion etching techniques used to produce VLSI circuits. Computer-generated continuous surface-relief DOE is recorded by direct laser-beam or e-beam writing in photoresist. Continuous surface-relief DOE can be also recorded in photoresist by interferometric (holographic) technique. After development recorded in photoresist surface-relief microstructures are being ion-beam etched into quartz or other inorganic optical substrates.

Fabrication of optical transmission elements in an SiN x membrane

Diffractive optical array element for realizing uniform spot on the plane non-perpendicular to the optical axis with geometrical shape transform

Diffractive optical elements (DOEs) and computer generated holograms (CGHs) can be fabricated with microelectronic technology. Therefore, they can play important roles in the packaging of optically interconnected multi-chip-modules as well as other electronic systems. In this paper, we will identify the varieties of DOEs and CGHs needed in single- and multi-stage optoelectronic interconnection networks, and present several fabricated examples. >

Dedicated diffractive VUV- and X-ray optical elements are essential for future developments in synchrotron instrumentation and methods like e.g. time-resolved spectroscopy. The quality of optical components like gratings or diffractive focusing elements matters directly to the results achievable. On the other hand the availability of such optical components is very limited at present. In this contribution we report on the development of new methods of time-resolved x-ray spectroscopy based on novel 3D diffractive optical elements (DOE) with a unique combination of properties. Such optical elements are of highest interest for application in modern synchrotron facilities like Free Electron Lasers (FELs) as well as for laboratory facilities with high harmonic generators (HHG). The project includes theoretical work as well as the development of a dedicated technology, including metrology, to manufacture such type of optics for applications in atomic, molecular and condensed matter physics. The here discussed type of optics was successfully implemented for soft-X-ray-application at the femto-second-slicing beamline at BESSY II storage ring of the Helmholtz Zentrum Berlin. DOE are expected to be important components in beamlines at upcoming new high brilliance X-ray sources such as FELs. The application of DOE`s allows to reduce the number of optical elements in a beamline. Thus allow to provide the highest possible transmission and flux as well as preserving the unique properties of FEL´s, like wave-front and coherence.

Large field-of-view lensless holographic dynamic projection system with uniform illumination and U-net acceleration

Diffractive optical elements capable of transforming the wavefront in a predetermined manner, with high efficiency may be apply in recording systems and reading information, and also its transmission in the optical range. To improve the efficiency use of diffractive optical elements is expedient to determine the requirements for their adjustment and the accuracy of beam setting parameters forming. As an example, considered the use of a diffractive optical element for transmitting high-power laser beam for the purpose to conducting the appropriate heat treatment of the process object. It was determined that the permissible error of alignment of the optical element is no more ΔU1 = ΔV = 0.18·10-3 m, the accuracy of the focused beam parameters should not be lower ΔrΦ/rΦ = 3.1 %; ΔRΦ/RΦ = 2%, and the permissible value of rotation angle Φ error of the diffractive optical element is ΔΦ = 2.30. To solve this problem a diffractive optical element is characterized by adequate values of allowable errors. Keywords: diffractive optical element, laser beam, adjustment, accuracy

State-of-the-art diffractive optical elements (DOEs) and computer generated holograms (CGHs) are fabricated using e-beam lithography and dry etching techniques to achieve multi-level phase elements with very high diffraction efficiencies. Electron beam lithography allows DOEs/CGHs with smaller feature sizes (e.g. for off-axis diffractive lenses with small f-number) to be fabricated. Dry etching techniques, especially chemically assisted reactive ion beam, allows DOEs/CGHs be fabricated in a variety of materials. Multi-level phase DOEs/CGHs, especially those of sixteen or more phase levels, mean their surface profiles are fabricated with high accuracy / quality. It is not only the e-beam system which dictates the feature size limitations, but also the alignment systems (mask aligner) and the materials (e-beam or photo resists). In order to allow DOEs/CGHs to be used in new optoelectronic systems, it is necessary also to fabricate the elements in different materials economically. Since the cost of a multi-level phase DOE/CGH is determined by the e-beam writing time, the number of etching steps for fabricating the master, and the technology for replication, we need to decrease the writing time and etching steps for the master and to develop a low cost replication technology for mass production without affecting the quality of the DOEs/CGHs. In this Chapter, we will review three DOE/CGH fabrication techniques and CAD development required, considering the overall design and fabrication time for multi-level phase DOEs.

This paper discusses the precise pressing technology for the fabrication of diffractive optical elements (DOEs). The new established fabrication process allows mass production of DOEs in high homogeneous optical glasses. Our precise pressing process guarantees a very constant quality over the complete production chain. Glass DOEs made by SCHOTT AG are planar optical phase elements with highly accurate shape and efficiency. The blazed profile of the diffractive optical elements was approximated by a stepped profile with up to sixteen phase levels. The highest measured diffraction efficiency for sixteen level gratings was 95%.

Diffractive optical elements (DOEs) have demonstrated applicability to a wide range of optical problems which cannot be solved with conventional optical elements. DOEs are increasingly becoming solutions for numerous nonconventional imaging tasks such as fan-out gratings and extended imagers. Applications include product marking, machining, robotics, medical diagnostic instruments, alignment instruments, optical computers, and fiber optic switches, to list only a few. However, the phase functions provided by most commercial lens design codes for DOE design lack the generality needed for these nonconventional imaging tasks. The solution taken in the past, of pixelating the aperture and independently varying the phase of every pixel, requires writing a specialized wavefront propagator code since such a phase function is unsuitable for ray tracing codes. We show here new phase functions which are more general than those currently provided in commercial lens design codes but which remain easily adaptable to these codes. Example designs, demonstrating the increased flexibility of these new phase functions, are also shown.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Low-cost near infrared spectrometers have a potentially wide market used in material characterization, material sorting and food quality control (fat and proteins measurement). Such applications have relaxed demands for high diffraction efficiency and spectral resolution. The number of wavelengths used in the final calibration is often limited as seen in commercial solutions that comprise filter wheels or grating spectrometers. A standard grating can be replicated to a very low cost in large numbers [1]. The cost of detector arrays, optics for light collimation and the final production cost connected to careful alignment of a number of optical elements, will typically be much larger than the cost of a replicated grating. So, if we want to make a low-cost near infrared scanning spectrometer, we need to replace the detector array with a single detector and a scanning mechanism and integrate the functions of grating, collimating lenses and wavelength references into a Diffractive Optical Element (DOE). The design is based on the properties of diffractive lenses [2,3] and DOEs for multi-wavelength imaging [4].