Problems of ion treatment in diffraction optical elements (DOE) technology with ion beam and reactive ion beam systems are discussed. Etching is carried out with particular screening of ion beam on contact protecting masks, which are films of organic (light sensitivity composition on the novolac base) and inorganic (vacuum deposited films of Al, ZnS, Nd2O3, As-S) materials. DOE microstructure parameters and optical-technical characteristics of DOE produced on the surface of optical glasses (binary synthesized holograms, phase filters, phase modulating elements of kinoform type with high efficiency) are reported.

In our work we dealt with holographic lenses recorded on quadrics of revolution. According to third order aberration theory, we derived the expressions for the aberration coefficients in the case of holographic lenses with shifted pupil. We show that the aberration coefficients for such system could be expressed by the combination of aberration coefficients for the holographic lens with pupil in contact. We also show that ellipsoidal and hyperboloidal holographic lenses can be replaced by spherical lenses. We examine some possibilities of aberration correction by the substrate geometry and pupil position change.

The possibility of application of a holographic lens for Fourier spectrum analysis is discussed. A set of parameters describing a holo-lens, including location of its input pupil and curvature of its surface, are proposed according to the results of III order aberration analysis. Recording holo-lens on spherical surface creates the possibility of coma correction. The assumption that the input pupil is not in contact with the lens (as it is the case of Fourier transforming setup) enables change in astigmatism, field curvature, and distortion; the latter being very important for the lens used in Fourier spectrum analysis. The imaging quality of the proposed lens was investigated numerically by evaluating aberration spots for different spatial frequency components.

This paper presents results of research activities devoted to preparing optical diffraction elements for space waves by use of electron-beam lithography. It is shown that the orthogonal electron-beam drawing can increase irregularities and flaws. Relations between the zone area inaccuracy and properties of the relief binary phase transparent screens are described. From these relations, the demands for setting the necessary edge drawing quality of the electron beam exposition are derived.

This paper presents an analytical method for determining the grating vector distribution of holographic Fourier transform lens (FTL) recorded on a curved substrate. The design method is based on analytic ray-tracing procedure that exploits the minimization of the mean-squared difference of the propagation vectors between the actual output and desired output rays. This minimization yields an analytic solution for the optimal grating vector. The simulation of spot diagrams has allowed us to state that the designed grating vector distribution is optimal for a sufficiently wide spatial frequency range.

Holographic optical elements (HOEs) become more and more important in modern optics. The most important application of HOEs is a holographic lens working as an imaging element. It is often used in monochromatic light because in polichromatic light the image location strongly depends on wavelength, which is usually a great disadvantage. However, in some cases this drawback can be changed into an advantage when a spectral device is regarded. This single diffractive lens can be applied as a basic element of monochromator or spectroscope. In a spectroscope, an input slit is illuminated by polichromatic light of which the spectral content is to be investigated. Each wavelength is focused into a different point and can be observed at the same time. For spectroscopy of good quality all light spots should be small and spatially separated. There are some difficulties in obtaining such spots sensibly separated along direction different from an optical axis. This difficulty disappears when we regard a monochromator. In a monochromator an input slit is illuminated by the light of continuous spectrum. Each wavelength is focused in a different point along optical axis. By moving an output slit one can choose an image of proper wavelength. For reasons stated above our investigations are limited to the monochromator. To establish optimum geometry parameters of this device it is necessary to analyze the sphero-chromatic aberration of a single holo- lens.

The preliminary design of optical systems with kinoform element (KE) in the field of second and fourth order wave aberrations is considered taking into account the highest order spherochromatism. The results of balancing of highest-order aberrations are discussed. The choice of the optimum aberration balance is shown. On the basis of this method, the apo-lens F/1.8/300 with KE is designed. The theoretical and experimental characteristics of this lens are presented.

The spectral diffraction efficiency of phase holograms depends on refractive index modulation, grating spacing, and the thickness of a holographic grating, e.g., the refractive index modulation of the dichromatic gelatin grating (DCG) can be increased so that the diffraction efficiency of 90% measured in Bragg angle without refractive index matching can be achieved in the recording wavelength. The use of the same holographic grating in longer wavelength regions in accordance with the Bragg condition demands the refractive index matching. In our applications, holographic phase gratings in hololens form (HOL) are used as a wavelength selective elements in conventional optical multi-/demultiplexing (mux/demux) applications, where various wavelengths are multiplexed to the detectors needed. On the other hand, the novel applications of the HOL element used as a monochromator in the external cavity construction of a semiconductor laser according to the refractive index matching the Bragg condition are theoretically investigated in the wavelength region from 1.3 micrometers to 1.5 micrometers .

The conventional computer generated holograms (CGH) presented in literature are calculated with the discrete Fourier transform (FFT). In optical reconstruction of the CGH the spatial components diffracted from a photographically reduced hologram are collected by a lens to produce a reconstructed picture. The angles between the diffracted spatial components and the optical axis are typically in the range of milliradians. On the other hand, computer generated diffraction gratings can be calculated without any Fourier transformation by using discrete wavefront theories. The reduction of the holograms to the right scale can be made, e.g., by using focused electron beam, focused laser beam, or photographic process. In our applications some diffraction gratings are calculated with the aid of the Stardent 3040 system with four MIPS R3000 parallel processors (64 MB) and reduced by using photographic processes to complete the diffraction gratings into optical range applied by the conventional holography.

Silver halide sensitized gelatin has proven to be an alternative to dichromated gelatin as a recording material in the production of transmission holographic optical elements (HOEs). In this paper we discuss the possible applications of this process to the production of reflection HOEs as well as the possible use of one of them in the construction of a hybrid refraction- diffraction system that could be used to copy transmission HOEs using partially coherent light.

The stationary phase method introduces a new insight into imaging by means of holographic diffraction structures. The loss of information about the object, connected with diminishing hologram size, is directly related to the high value of the boundary wave amplitude. It is important when the holograms are to be coupled with the systems of integrated optics.

Crossed gratings are analyzed from the point of view of their holographic recording. For the theoretical description of the diffraction efficiency, the Rayleigh model of shallow line profile is used. Applications to metrological gratings for determination of position and to antireflection gratings are presented.

In terms of achievable spatial resolutions, the most successful optics used to date for x-ray imaging have been zone plates that can be now be made with outermost zone widths of less than 25 nm. Techniques for the manufacture of these optical elements are reviewed and potential future improvements are considered. Some recent applications of zone plate optics are discussed.

In a computer experiment we prove shift and scale invariant pattern recognition abilities of an elliptic coordinate transformed phase-only filter. The filter is built in the following way: from the classical matched filter we take the phase component only and then the elliptic coordinate transformation is made. We analyze performance of the filter for different semiaxes ratios and on-axis stops of several diameters. Discrimination ability of the filter is calculated. The filter allows good recognition of objects with change of scale by a factor of 1.5.

The hybrid micro-objective lens with the kinoform corrector has been developed and fabricated. Kinoform corrector is made by the photorastering technology. The numerical aperture of the micro-objective is 0.6 and 0.7; the focal length is 9.1 and 5.9 mm. The micro- objective can find its applications for various laser interferometers to collimate radiation of diode lasers and for date recording and read-out optical and magneto-optical disks.

A compact and scalable two-dimensional optical crossbar based around a matrix-matrix multiplier has been designed. Low cross-talk is obtained by the use of high efficiency computer generated holographic fanout elements in a multiple imaging architecture. The methods by which the necessary holographic elements are designed and fabricated are discussed and a two-dimensional design technique is employed. The results of preliminary experiments using these elements in this architecture are obtained and the viability of the scheme is assessed.

If we record a hologram on a light—sensitive material which reacts on act.inic light polarization so that the corresponding anisotropy and gyrotropy appear in it, in the reconstruction process the full reconstruction of an object field both by phase,amplitude and freguency and by the polarization state is possible [1,2]. For the first time the effect of the anisotropy (photoanisotropy) induced by a linearly polarized light was discovered by F.Veigert in 1919 (3]. The similar effect of the gyrotropy (photogyrotropy) induced by a circularly polarized light was discovered by Zoher and Coper in 1928 (4]. The presence in the absorbing medium on the wavelength of the actinic radiation distinguishes photoanisotropy and photogyrotropy from the similar effects caused by nonlinearity of medium sus— ceptibility (Kerr,Faraday optic—optical effects, etc.). At present in a number of laboratories intensive investigations on development and improving vector characteristics of such media are being carried on [5—7].

There are given equations describing the basic grids, which superimposed with themself, create the moire pattern in the form of the spherical, equilateral hyperbolic, and linear zone plates. All cases are derived for mutual displacements performed by translations along the axes of the coordinate system and by rotations. A family of basic grids set up a complete set of solutions. Moire zone plates can serve as imaging elements with very long, variable focal length, and have an application in alignment in the technique of three points.

Theoretical study of the general order Hermite-Gaussian beam transformation by a phase circular zone hologram, classifies the phase circular zone hologram as a multiple laser beam splitter, if the incidence is off axial. Each of the split components is of the same mode-order and orientation as the incident beam, but are described by different complex parameters. Their waist locations and magnifications are dictated by the position of the manyfold foci of the zone hologram, and for a given diffracting order, satisfy the Self's relations, typical for the beam transformation by ordinary lens. From the theoretical results the Kogelnik's ABCD rules and ray transfer matrices for the circular hologram are defined.

An important diffraction problem in modern optics is to design gratings that are able to produce given output power distributions from a given input. In this paper the coupled multiwave diffraction approach, together with an optimization method, is applied to design gratings, which diffract one incoming beam into N output beams with a given power distribution. Several gratings have been designed. We show that by choosing the material parameters properly relatively simple continuous grating profiles having better diffraction characteristics than binary gratings or kinoforms can be found.

The purpose of this paper is more to stimulate a discussion than to set out well proven and undisputed facts. A great many papers are being published on the subject of diffracting optics and these usually fall into one of two classes: those concerned with bulk or with surface relief components. In most cases the authors have experience with one or other technology and often tend to describe the benefits of their own advances without fully putting them into the context of what is offered by alternative technologies. When comparing different forms of diffracting component it is also necessary to compare them with the equivalent conventional ones and to compare all relevant aspects of performance and cost. This critique is intended to be as impartial as possible but it must be admitted that the author's main experience is with surface relief technology.

This paper describes the manufacture and performance of two forms of zone plate blazed for use in the infrared and assesses their potential value. The first operates on axis in transmission and is made in germanium. The second operates in reflection and is electroformed in nickel.

An optical beam shaping system based on a single Computer Generated Hologram has been realized. It focuses a laser beam with Gaussian profile to a square area with uniform intensity. In order to achieve a rectangular focal spot which is as close as possible to the size of the diffraction spot, we investigated two different hologram calculation methods. The first is based on a ray tracing approach, while the second one uses an iterative Fourier transform algorithm. Computer simulations and experimental results are shown.

Questions concerning stigmatic imaging by means of holographic optical elements (HOEs) are discussed. Several aplanatic systems, in particular holographic doublets, were designed and analyzed. The doublets are generated by both spherical and aspherical recording wavefronts. The imaging properties of a single HOE, single aplanatic HOE, and aplanatic holographic doublets are compared and the superiority of the aplanatic doublets and high degree of astigmatism suppression are demonstrated. The HOE designs and the presented analysis were performed using the HADES computer ray-tracing program.

Short-range optoelectronic interconnection systems not only between, but also within, data processing systems have often been proposed in recent years. They handle high-data rates, eliminate ground loops, avoid crosstalk along the length of the line, allow parallel communications, and will, in the future, dissipate less heat than purely electronic data links, thus allowing higher packing densities. Diffractive optical elements (DOEs) are well suited for application in parallel array interconnects, because of flexibility in design, the possibility to manufacture array-optics (arrays of lenses, deflectors, beam splitters), small size, and light weight. DOEs can be miniaturized, they may integrate several different functions (focusing, deflection, and beam splitting) into one component, and they often can be fabricated by planar technologies and replicated, once one master has been made. How to fabricate light efficient DOEs is discussed. Several system experiments are presented: (1) parallel one-to-one array connections; (2) interconnections based on a light guiding glass plate with holographic coupling elements; (3) permutation elements for optoelectronic switching systems; and (4) bus- type interconnections (many-to-many interconnection) based on multiple beam splitters.

The main techniques for optical pattern recognition are based on the correlation methods. In the past few years several correlation filters related to classical matched spatial filters have been proposed1'2 and different measures of performances have been introduced3. Recent works have shown that the problem of low light efficiency of optical correlators can be avided with the help of several types of pure phase-only filters . They have also good features for recognition process such as high discrimination capability and high sharp correlation peaks. Optical realization of the phase-only5flters (POF) based on holographic recording method is very difficult ' . Using digital methods one cn easily codify and modify the filter depending on the applications. The binary encoding of the phase-only filter (or its binary version) is the best candidate for recent applications in pattern recognition. Nevertheless most of graphic devices controlled by computer such as plotter, laser printer or the majority of spatial light modulators can only modulate the amplitude. For such a reason several methods have been recenly proposed to obtain amplitude encoded phase-only filters (AEPOF) , which can be written on an amplitude modulating device. However, amplitude modulation does not provide high light efficiency of the optical correlator. The use of phase materials for spatial filters recording allows better utilization of laser light in recognition systems and keeps laser power requirements lower. One of the more popular conventional phase materials is the bleached holographic emulsion. Bleaching removes the attenuation giving more light in the output correlation plane, but also in the case of classical matched filtering distortion and increased scattering noise occur in the reconstructed avefront which degrades the recognition capability of the filter . Binary amplitude encoded computer generated holograms do not suffer from distortion after bleaching11, because in this case the distribution of the phase hologram is identical to the distribution of the amplitude hologram without bias. The reconstruction is not more disturbed than the reconstruction of the amplitude hologram. In this paper we analyze the usefulness for pattern recognition of the bleached mplitude encoded phase-only filters based on Burckhardt's method . The silver halide (sensitized) gelatine (SHSG)12 is proposed to record computer generated phase-'only filter. The SHSG provides higher signal to noise ratio (SNR) that conventionally bleached eiitulsions because of absence of scattering centers after processing.

A diffractive optical element (DOE) consists essentially of a microstructure with (2D) local variation of grating period and (3D) relief or phase profile. The 2D-design, which can be performed by optical raytracing, determines the optical function of the element, the 3D-design determines its diffraction efficiency. A great number of promising system concepts with DOE are known, but the critical point still remains the masterizing of manufacture methods suitable for industrial applications of DOE. Different DOE manufacture methods are under investigation at CSEM. They have already been applied to the manufacture of test and prototype elements. Well masterized technologies, like the interferometric recording of transmission type holographic optical elements (HOE) in dichromated gelatin or photoresist are currently used to fabricate application specific elements. Typical spatial frequencies are 1700 - 2000 1/mm with an efficiency ranging from 50 to 90%, where the best values were still achieved with DCG elements. First elements were also recorded in photopolymer, a very promising photosensitive material for HOE. For reflection type elements the preference has been given to technologies derived from microelectronics silicon wafer processing. CSEM's electron-beam writer is routinely used for generating basic (2D) DOE patterns in the form of standard chromium-on-glass masks, which are, in optical terminology, binary computer generated holograms (CGH). These 2D patterns were transferred onto several types of substrates (silicon, quartz, glass, copper) by contact copy photolithography and subsequent wet or dry etching in order to obtain a 3D profile. The highest spatial frequency routinely transferable with this standard process is presently limited to 500 1/mm. For higher spatial frequencies (up to 1500 1/mm) the basic pattern is directly written by e-beam on the photoresist coated substrate and subsequently processed. Ion exchange in glass is an interesting technology for DOE because the diffractive structure is imbedded in the substrate and thus protected from dirt and dust. For this process, compatibility with a microelectronic environment is much more difficult to achieve. First results already show that a considerable technology effort would be necessary in order to overcome the observed limited spatial resolution of 200 1/mm.

In this paper the relation between recording and reconstruction geometries for maximum diffraction efficiency in thick holographic lenses is analyzed. Theoretical expressions are presented when variations in recording material due to processing are taken into account. A particular holographic lens is studied in both theoretical as well as experiment terms, finding the optimized reconstruction geometry for maximum diffraction efficiency and the aberration that appear.

This paper reviews some results of the modern investigations on holographic spectral elements based on volume phase gratings recorded in sensitized gelatin films. Physical principles, fabrication techniques, and main characteristics of the holographic spectral elements are discussed. Some applications of the holographic spectral elements for tunable laser sources are demonstrated.

The effect of the following factors degrading the resolution of the reconstructed holographic image have been studied: the angular misadjustment of the hologram or that of the reconstruction wave at reconstruction, the thickness variations of the hologram substrate, the Gaussian intensity profile of the auxiliary waves, and the finite spatial resolution of the recording medium. The above effects have been studied in five recording geometries with point and line sources. Practical tolerances of certain parameters for maintaining image quality were given where is was applicable. It was the unevenness of the substrate that proved to be the cause of the most serious degradation of the reconstructed image. Some experimental demonstrations are also shown. In conclusion, practical rules for recording high resolution holograms are given.

This paper presents the investigation results of a new photolithographic fabrication method of highly effective diffractive optical elements (DOE). The method, unlike the well-known multilevel one, does not require a set of masks prepared and aligned. It is demonstrated that the application of half-tone image binarization technique allows one to fabricate a DOE with continuous phase profile and high diffractive efficiency, which can be achieved with a single raster mask and an optical projection system of a photolithography setup used as low-pass spatial filter. Using the algorithm of pulse-width modulation experimental samples of DOE aberration correctors and kinoform lens array with the numerical aperture NA equals 0.1 were fabricated. The diffraction efficiency of these elements, fabricated with conventional photolithography equipment, was more than 80%.

The diffractive elements of the anisotropic structure can transform and separate light according to its population state. From this point of view the zone plate of an anisotropic profile is a diffractive optical element of a new type. In the present contribution the possibility of creating zone plates of different anisotropic profiles of registering on the polarizationally sensitive material of two differently polarized spherical waves is shown both theoretically and experimentally.

A new version of DEMOS program is presented. DEMOS (design, evaluation, and modeling of optical systems) is an integrated dialog system for modeling, evaluation, and design of optical systems with conventional and hologram optical elements (HOE). Theoretical principles and modern state-of-the-main possibilities and application principles of DEMOS program for optical systems with HOE design on personal computers are discussed.

A new approach to the optimization of the optical systems is described. This approach consists in the construction of the Merit Function on the basis of the higher order aberrations at the initial stage of the correction.

Reflection holograms and holographic optical elements fabricated by the Denisyuk method are spectrally selective. In certain applications there may be a need for the development of holographic structures that are not selective in terms of the spectral composition of the reconstructing light. This paper describes the possibility of creating spectral nonselective optical elements and reflection holograms on a dichromate gelatin layer (DGL). The essential condition for achieving nonselectivity in this case is a strong absorption of actinic radiation in the initial emulsion layer conditioning the strongly damping character of the summary field in thickness.