When considering a roadmap for technology development, the essence of the problem can be framed by two simple questions: 1) Where have we been? and 2) Where do we need to go? The first question is relatively easy to answer with some research, but answering the second requires significantly more effort. In this paper, we address these questions as they relate to the fabrication of diffractive and refractive micro-optics. A brief historical overview of micro-optics fabrication is presented, followed by our predictions on the future of the field. Examples of future applications, technical challenges, and supporting technologies required for manufacturing of different types of micro-optics are discussed.

We present a novel method for making 2D photonic crystal structures. The method relies on different dissolution rates of various organic materials in the developer. Thus, placing a layer of high dissolution rate material under a layer of low dissolution rate material yields a membrane released from the substrate where the photonic crystal has been patterned. This allows for creation of the entire structure in a single chemical development step. We present structures fabricated with this method.

In many laser diode applications, it is necessary to make a beam shaping or beam transformation. One example is the collimation, but often we wish to achieve additional properties like special shapes of the beam. Such beams can be designed with high efficiency and signal quality by means of refractive beam shaping elements. Frequently, we have to vary the beam propagation parameters significantly to fulfil the beam shaping task. If we want to use refractive beam shaping elements, the design results in an element with a large profile depth. A well suited fabrication method for refractive beam shaping elements is the gray tone lithography, however, it is limited by the achievable depth of profile. This means that design and fabrication methods should be taken into account to achieve the advantages of refractive elements. On the one hand, we have to improve fabrication technique for enlarging the producible profile depth. On the other hand, we have to use all of the design freedoms to reduce the profile depth. We will present results of the design and fabrication of a refractive beam shaping element with a profile depth up to 60micrometers to transform a laser diode beam into a line intensity distribution.

The transformation of a given incoming wave front into a certain intensity distribution is an interesting task for micro optics with applications, for instance, in material processing and display illumination. For the design of a beam shaping element, the amplitude and the phase of the illumination wave have to be known at least in one plane. If the light source for the beam shaping problem is a high power laser or a multi mode fiber, the illumination wave is not the fundamental mode but the superposition of many modes with fluctuating fractions of intensity. This means that the amplitude and the phase of the beam can not be expressed analytically. However, the average amplitude can be calculated using the measured intensity distribution while the phase is unknown. Therefore we applied a method where the phase of the real illumination wave is approximated by a representative phase distribution which can be assumed from the propagation of the multi mode beam. With this approximation, we calculated refractive beam shaping elements using well known numerical methods based on wave optics. The beam shaping elements were fabricated using gray tone lithography which is a well suited technology for the fabrication of continuous surface profiles. We will present results of the application of such an element to shape the beam from a multi mode fiber.

We report on the fabrication of aspherical refractive microlens arrays on 8'' fused silica and silicon wafers at Suss Neuchatel, Switzerland. Refractive, plano-convex microlenses are fabricated by using photolithography, a reflow or melting resist technique and reactive ion etching. Diffraction-limited optical performance of the microlenses is achieved for refractive microlenses from 100 microns to 1.5 mm diameter and 2 to 50 microns sag. Aspherical lens profiles (aspherical constant from k equals -0.5 to -5.2) are obtained by varying the etch parameters during the reactive ion etching transfer. Microlens arrays in fused silica and silicon are fabricated for high-efficient fiber coupling and telecommunication. Densely packed arrays of cylindrical lenses (packing density > 98%, parabolic profile) are fabricated for flattop illumination at UV-wavelengths. Excellent array uniformity of is required for microlenses used within Microlens Projection Lithography systems.

By using modern wave optical design methods elements and systems with complex optical functions, such as beam shapers or phase correctors can be calculated. Often the positioning of the optical elements to each other and to the optical beam axis is extremely critical and requires a considerable effort during assembly. We demonstrate two fabrication methods suitable for the high precision wafer- scale realization of complex microoptical systems comprising different optical functions. These methods are the combination of different optical functions by a special laser lithographic writing technique on reflow lenses and a double sided UV-replication technique. The method is demonstrated by an example system consisting of a single- mode fiber collimation, a beam shaping and a phase correction function.

The commercial success in micro-system technologies depends on a reliable and controlled mass production. Without a good quality assurance and process control it is impossible to guarantee the specifications of the products and to minimize the production costs. Among test equipment for the function of the end product it is necessary to introduce dimensional metrology devices for checking vertical and lateral structures in silicon or PMMA materials close to production machines. Due to the small dimensions of HARMS or MOEMS components, traditional surface testers as mechanical stylus instruments are not able to analyze structures with high aspect ratio. In this paper a new approach to surface measurement technique, the confocal white light microscopy, is described which opens the possibility to measure soft or transparent materials from the nanometer up to the millimetre range. In contrast to other methods, like phase shift interferometry, the confocal measurement technique is nearly free of artefacts due to physical pinhole filter masks.

A review of the current state of the art in optical and electron beam lithography simulation is presented. Basic physical models are described and examples are given. In addition, rigorous electromagnetic simulation for mask topography is shown and the use of statistical modeling to predict feature size distributions in manufacturing is described. Finally, numerous examples of the use of lithography simulation and its impact on the semiconductor industry are offered.

In the last years the application of gray-scale masks (GSM) for diffractive optics manufacturing attracts attention because of cost-effective possibility to produce a lot of diffractive elements on hard and heat-resistant thermally stable substrates. Direct laser writing of GSMs and fabrication of diffractive optical elements are effectively realized with application of LDW-glass (material for Laser Direct Write from CANYON MATERIALS, Inc). An important advantage of this material is the real-time change of transmittance in a single-step process without liquid development. It is shown that optimal transmittance range in which track width is not more than 1 micrometers is from 5-10% (transmittance of unexposed area) to 60-65% for LDW-glass type I having thinner colored layer. Power modulation and surroundings dependent peculiarities of direct laser writing on LDW-glass are discussed. Results of fabrication of diffractive optical elements using LDW-glass masks are presented. Among several types of LDW glasses studied the advantages of new GS-11 glass are elaborated. Application of GS-11 glass for GSMs allowed to fabricate blazed diffractive structures with backward slope width of 0.8 micrometers .

The paper shows a fabrication technology for glass micro lenses. It starts with the fabrication of a boron phosphorus silicate glass (BPSG) layer on a quartz substrate. Pre-forms of BPSG are fabricated using photolithography and dry etching. After that, temper process at a temperature in between the melting temperature of each material changes the surface to the minimal surface. Spherical, cylindrical and even ball lenses are profiles which can be realized. Spherical, cylindrical, and ball lens profiles that can be produced.

We describe development of passive phase correction elements to compensate for static phase errors and prompt thermally induced aberrations in the HELEN laser at AWE. Partial compensation of cooling effects is also included in the design. Phase elements have been fabricated through two processes, an indirect write lithographic process using amplitude masks generated from measured laser wavefronts and a direct write method using a novel wet etch figuring tool.

Large aperture diffractive optics are needed in high power laser applications to protect against laser damage during operation and in space applications to increase the light gathering power and consequently the signal to noise. We describe the facilities we have built for fabricating meter scale diffractive optics and discuss several examples of these.

Aspheric surfaces are becoming interesting for the reduction of elements in optical systems as well as for improving the quality of the image forming system. The fabrication process of aspheric surfaces has been improved. For optical testing of aspheric surfaces computer generated holograms (CGHs) are interesting and already used. To perform aspheric testing in the same accuracy as spherical surface testing, further improvements of the CGH-null test method are required. A new concept for testing aspheric surfaces with CGH-nulls, including a calibration of the system, will be described. To specify and verify CGH quality, systematic errors due to fabrication inaccuracies of the CGHs will be analysed. On the other hand, alternative methods that provide more flexibility but possibly less accuracy than the CGH-null technique are required. Potential alternative testing methods of aspherics will be discussed.

Testing aspheric surfaces by interferometer set-up together with a NULL-Computer Generated Hologram (NULL-CGH) is a well-established method. Nevertheless, this method is used in industrial manufacturing environs only frequently yet due to certification issues, cost dependence on laboratory-intensive equipment and highly specialized skills that are required to perform Null-tests for aspheric surfaces. On the other hand there is no widely accepted alternate method to feedback the aspheric test surfaces's shape error to the workmanship during fabrication of aspherics. This paper deals with results obtained by testing aspheric surfaces in industrial manufacturing environs with CGH of different production accuracy.

Two different methods for the measurement of cylindrical lenses will be presented in this paper. The first method uses the principle of grazing incidence interferometry. A computer generated diffractive optical element (DOE) generates the wave fronts which impinge under grazing incidence onto the surfaces to be tested. The light is reflected at the surfaces and diffracted at a second DOE identical to the first one. The 0-th diffraction order of both DOEs is used as reference wave. The deviations of up to three surfaces (front-side, backside and one of the border sides) of a cylindrical lens from their ideal shape can be measured simultaneously. Additionally, the orientation of these three surfaces with respect to each other are determined. The second method measures the aberrations of a cylindrical lens in transmitted light by using an interferometer of the Mach-Zehnder type. The cylindrical wave of the lens under test is compensated by a DOE which generates a plane wave if the incident wave is an ideal cylindrical wave. So, the wave aberrations of the cylindrical lens can be measured. The set-up is designed for cylindrical lenses with a high numerical aperture of up to 0.8. The principles of both methods and first experimental results will be presented.

For testing of aspheric surfaces, null-CGH were needed in different sizes and numerical apertures. The design of the CGH pattern from the wave front to be produced leads to physical problems and last not least to writing times that can strongly influence the price of the CGH. Due to this problems, we investigated the validity of the thin element approximation (TEA) that is the most usual and most convenient method for CGH pattern design. By using rigorous results for the change of the wave front to be constructed, it is possible to use TEA in an extended range. The investigation of the pattern decomposition has shown its influence on the data volume and writing time as well on the CGH quality. Using this knowledge, CGHs having up to 130mm diameter and numerical apertures of 0.55 have been fabricated.

The importance of complex optical components increases permanently. In the past most applications could be solved by spherical optics. Spherical optics can be manufactured by conventional and established grinding and polishing processes. In the last years aspherical and microstructured optical components became more and more important. These components can only partly be manufactured by conventional processes. One reason is the lack of dimensional accuracy after the polishing process. Precision cutting with diamond tools on ultraprecision machines offers the possibility to manufacture complex optical components in one step. Therefore both high surface quality and dimensional accuracy can be obtained. The ultra precision cutting is suitable for the manufacture of both moulds and optical components itself. In this paper different precision cutting processes and there possibilities and limitations are discussed. Furthermore different types of ultra precision machine tools and there main applications are introduced.

In the past years, ultrashort pulse lasers have been established as precise and universal tools for the microstructuring of solid materials. Since thermal and mechanical influences are minimized, the application of this technology is also suitable for the structuring of optical materials and opens new possibilities. In this paper, the influence of pulse duration, pulse energy (fluence) and polarization on the cutting quality for glass and silicon will be discussed. As a concrete application, the cutting and micromarking of dielectric coated mirrors for high power fiber lasers will be highlighted.

Diffractive optics is a field where the progress is defined by fabrication technology. Diffractive optical elements (DOEs) are generally planar structures, typically fabricated using X-Y image generators designed for semiconductor industry. However there are some kinds of DOEs for which the polar scanning geometry, where the optic rotates under a writing beam, is more preferable. In some cases polar coordinate machines provide the only practical method of fabricating DOEs with the required accuracy. It is necessary to take into account the DOE specification when choosing the fabrication method. The present paper considers peculiarities of polar coordinate laser systems for large size and high precision DOEs fabrication. The specific error sources for these systems are described and compared with those of X-Y systems. An optimal writing strategy is discussed. The wavefront aberrations of rotationally symmetric DOEs caused by fabrication errors were measured interferometrically. Different types of aberrations were identified and can be referred to certain writing errors. Interferometric measurements of the wavefront errors for binary zone plates with a 64 mm diameter and 0.45 numerical aperture have shown that the wavefront root-mean-square error does not exceed 0.009 (lambda) wavelength.

We suggest a new 3D-camera system for integral photography (IP). Our method enables high resolution three-dimensional imaging by employing a low-definition electronic camera. In contrast to conventional IP a moving microlens array (MLA) is used. The intensity distribution in the MLA image-plane is sampled sequentially by using a pinhole array. The inversion problem from pseudoscopic to orthoscopic images is dealt with by electronic means. The new method is suitable for real-time three-dimensional imaging. We verified the new method experimentally. Integral photographs with a resolution of 3760 pixel x 2560 pixel (188 x 128 element images) are presented.

We have developed several kinds of diffractive optical elements with subwavelength structures for optical information and transmission system. This paper describes the optical elements and fabrication technique, such as antireflection structured surface, a high efficiency computer generated hologram, a non-polarizing resonant grating filter, and a micro retarder array for the real-time polarimeter.

We report on an optically pumped polymer laser based on a circular grating resonator. The circular gratings were fabricated by electron beam lithography into a fused silica substrate. Due to the importance of a precise circularity of the grating we used a Leica LION LV1 electron beam writer allowing for smooth curved grating lines. A thin film of a methyl-substituted ladder-type poly(p-phenylene), spin-coated onto the gratings, acts as active material. Since the grating period satisfies the second-order Bragg condition it provides a true 2D feedback for the emitted photons of the polymer. At the same time surface emission is achieved via first order diffraction normal to the sample surface. Using short pulse laser systems for optical pumping we observe a clear lazing threshold, highly directed emission and a narrow spectral linewidth. By changing the grating period one can tune the emission wavelength over the entire gain region of the polymer.

An index matching fluid has been used to minimize the effect of interference fringes which develop when contact printing diffraction gratings on silicon wafers. These fringes are the result of interference effects when there is a small but uneven gap between the photomask and resist surface. They are especially troublesome when printing and etching large area, coarse diffraction gratings on the surface of silicon wafers and silicon disks.

The spatial coherence of optical gratings fabricated by means of a step & repeat camera is characterized by a diffractive interferometric displacement sensor using the grating under test as the grating scale. The displacement sensor head comprises two readout gratings at a definite distance from each other which allows the determination of the local deviation of the grating period with a resolution of 0.001 nanometer.

Ion beam figuring (IBF) using inert gas (e.g. Ar) and (Reactive) ion beam etching [(R)IBE] gain growing interest in precision optical surface processing, RIBE mainly for proportional transfer of 3D-resist masks structures in hard optical materials and IBF for finishing and nanometer precision surface figuring in high performance optics technology. Ion beam and plasma jet etching techniques related to different optical surface figuring requirements have been developed at IOM during the last decade. Some of these techniques have been proven to be mature for application in industrial production. The developmental work include material related process tuning with respect to enhance the processing speed and to improve surface roughness and waviness, further various processing algorithms related to different surface figure requirements and processing related equipment modification. Plasma jet assisted chemical etching is under development with respect to efficient machining techniques for precision asphere fabrication. The paper gives an overview of precision engineering techniques for optical surface processing focusing on the status of ion beam and plasma techniques. The status of the proportional transfer of 3D micro-optical resist structures (e.g. micro-lens arrays, blazed fresnel lens structures) into hard optical and optoelectronic materials by (reactive) ion beam etching will be summarized.

Fabrication of a fine diffractive optical element on a Si chip is demonstrated using imprint lithography. A chirped diffraction grating, which has modulated pitched pattern with curved cross section is fabricated by an electron beam lithography, where the exposure dose profile is automatically optimized by computer aided system. Using the resist pattern as an etching mask, anisotropic dry etching is performed to transfer the resist pattern profile to the Si chip. The etched Si substrate is used as a mold in the imprint lithography. The Si mold is pressed to a thin polymer (poly methyl methacrylate) on a Si chip. After releasing the mold, a fine diffractive optical pattern is successfully transferred to the thin polymer. This method is exceedingly useful for fabrication of integrated diffractive optical elements with electric circuits on a Si chip.

We present an approach towards design and fabrication of optical microsystems based on UV-replication techniques using Ormocer materials. An integration of the structures on chip level is demonstrated for Vertical Surface Emitting Lasers (VCSEL). VCSEL's are of increasing interest for various fields such as telecommunications, optical sensing and optical interconnects. In terms of optical system integration, high technological requirements are imposed. UV-replication techniques using Ormocer materials offer a cost-effective way of integrating micro-optical elements directly on the chip with reduced assembly effort. Structures up to several hundred microns thickness and alignment tolerances in the order of few microns can be produced. The method is suitable for the fabrication of single elements, arrays and is extendable to wafer-scale processing. Here, we give an example for the coupling of VCSEL arrays into multimode optical fibers using two different approaches: Focusing of the VCSEL output into the fiber using replicated microlenses and fiber butt-coupling of the VCSEL lasers with help of replicated fiber alignment/guiding structures. Origination of the structure elements is accomplished by direct laser writing into photoresist and resist reflow techniques, respectively. Specific limitations of the corresponding fabrication method are already taken into account during element design and modeling. Results for the replicated lenses show a total fiber launch efficiency better than 70% over the laser operational range with alignment tolerances of approximately +/- 10 micrometers , which can be met by passive fiber alignment. In case of the replicated fiber alignment/guiding structures, fiber launch efficiencies better than 50% over the operation range and peak values better than 80% are reported.

The photolithography using gray-scale masks (GSM) with multilevel transmittance is now one of promising ways for manufacturing of high efficiency diffractive optical elements and microoptics. Such masks can be most effectively fabricated by laser or electron-beam writers on materials with a transmittance changing under influence of high-energy beams. The basic requirements for adaptation of existing and developed scanning laser writers are formulated. These systems create an image by continuous movement of a writing beam along one coordinate and overlapping of adjacent written tracks along another coordinate. Several problems must be solved at the GSM manufacturing: the calibration of the influence of the laser beam on a recording material without transferring the gray-scale structure into photoresist; the transmittance at the current exposed pixel depends on surrounding structures generated before recording of the current track and a character of the laser beam power modulation; essential increasing of the computed data in comparison with binary elements. The offered solutions are based on the results of investigations of the materials with variable transmittance (LDW-glass, a-Si film) and takes into account the specificity of diffractive blazed microstructures. The reduction of data amount for fabrication of multi-level DOEs is effectively performed using offered vector-gradient data format, which is based on piecewise-linear approximation of phase profile. The presented approaches to adaptation of laser writers are realized in software and hardware, and they allow to solve the basic problems of manufacturing GSMs.

Proximity correction is an important technique to fabricate diffractive optical elements with the direct-writing electron-beam lithography. For the precise proximity correction, the absorbed energy distribution is calculated with an electron scatter simulator based on the Monte Carlo method, and a resist profile is estimated with a resist development simulator based on the cell removal model. In this paper, we calculated the optimum electron dosage for a chirped-period diffraction grating by use of such a precise proximity correction. To reduce the calculation time, we set the cell size 200nmx200nm. The resultant resist profile, however, was much more precise than the cell size because of the interpolation. It took 24 hours to optimize the electron dosage of a grating with a width of 5mm and the minimum grating period of 4micrometers . Moreover the grating, which was fabricated according to the calculated dosage, had a profile that agreed well with the calculated profile.

Optical tweezers have been used to trap and manipulate tiny particles including biological cells, viruses and microorganism in the biology field. By modifying the shape of the trapping object the rotation of the objects using radiation pressure was reported. Usually, these micro-objects are fabricated through complicated ion beam etching process. In this work, windmill-shaped micro-rotators are fabricated by simple photolithographic method and rotation properties are examined. The negative photoresist which is spin coated on the glass is placed in contact with photomask and illuminated with ultraviolet light from Hg lamp. The micro-rotator has four arms of 10 micrometers length and side surface area of each arm are different to surrounding medium. Because of the asymmetrical structure, rotational torque is generated when incident laser beam passes through the side walls of the micro-rotator. The rotation speed of the micro-rotator depends on the intensity of incident laser beam, thickness of rotator and focused position of laser beam. When the laser beam is focused slightly above the upper surface of the rotator, the maximum rotation torque is obtained. The rotation speed increases in proportion to incident laser power. For a micro-rotator of 10 microns thick, maximum rotation speed, 24 rpm is attained with a Ar laser power of 75mW.

This research concerns a thin illumination device to be used by mounting between a Reflection-type liquid crystal display device (LCD) and a viewer. Because, the brightness of display is highly dependent on the surrounding environment, an auxiliary illumination is needed to provide against cases when surrounding light is insufficient. We investigated theoretically and experimentally into a grating for monochromatic illumination. First, the requirements of illumination were calculated and a grating shape for illumination was developed. The antireflection effect of the grating was confirmed. In this paper, the diffraction efficiency of the grating was calculated by a rigorous analysis method. It is structured the right triangular profile with the subwavelength period to project light onto the display object by using diffraction effect. Therefore, the light guide of length/thickness equals 50, with the grating, gets an illumination efficiency of 90%. Not occurring reflected light from the illumination device by an antireflection effect prevents that the contrast of display becomes low. Next, the fabrication method by using a reactive ion etching (RIE) that makes the grating of high precision was developed.

We made a form birefringent micro-retarder array for the real-time imaging polarimetry. The polarimetry system is composed of an imaging lens, the retarder array, a polarization film, and an image sensor. We fabricated a 92x70 retarder array by the electron-beam lithography and the reactive ion etching. Each retarder was a TiO₂ subwavelength grating of 0.15(mu) nm in a period on a silica substrate. Some polarization images of four Stokes parameters were obtained with the polarimetry system.

Infrared spectrometers using silicon immersion gratings and prisms can have substantial performance advantages over conventional instruments. The immersion gratings and grisms share a common geometry: prism-shaped pieces of silicon with blazed grooves along one side. The grooves can either be machined directly into substrates or the grooves can be machined into thin wafers which are then bonded to flat-surfaced prisms. Chemical micromachining currently is the best method of ruling grooves directly into silicon surfaces. The tolerances for near-IR diffraction gratings make direct machining of the grooves onto one surface of a bulky, prism-shaped substrate very difficult. We encountered a number of issues that we had to resolve when we tried to etch precisely positioned grooves into massive pieces of silicon: silicon substrate purity, lithography mask alignment, photoresist thickness uniformity, temperature control, wet etching vs. reactive-ion etching. We have successfully manufactured 7 line / mm gratings on 15 mm thick substrates. We performed optical tests with these gratings used as front-surface devices to determine efficiency and diffraction limited performance. Our echelle gratings have 70\% efficiency in 365th-368th order at 632.8 nm. Testing shows that the grating preserves a diffraction-limited point-spread function making them good dispersing elements for applications requiring high spectral resolving power.

The paper presents a physical representation of different stages in the kinetics of the evolution of the instability of dissipate periodical structures with square and hexagonal symmetry of the crater type deformations, called rosettes. The conditions of evolution and construction of an embossed periodical relief of superficial deformations with square symmetry and of the superficial deformation with hexagonal symmetry were deduced. In conformity with the experimental investigations carried out, it was established that on the free electrically charged surface of a viscous rheological medium the generation of superficial periodical deformations possesses a shock character and corresponds with the passing of the free electrically charged surface in a new embossed state which we call phase superficial crystallization. Generation of periodical superficial deformations is reduced to hexagonal symmetry of the crater type deformations in case of supercritical weak values, which correspond with the hard excitation in soft recording regime. The superficial deformation with square symmetry is characteristic for the hard recording regime in strong energetic fields.

This article presents results on surface cleaning with VUV radiation from dielectric barrier discharge-driven Xe₂* excimer VUV light sources at 172 nm in oxygen-containing gases. The basic mechanism for the generation of excited rare gas and rare gas/halogen dimers in dielectric barrier discharges is described, which is utilized to generate powerful and efficient, incoherent excimer (V)UV light sources. After a brief discussion of the formation of atomic oxygen and ozone by irradiation of molecular oxygen with VUV light at 172 nm, the dominant chemical reaction scheme in the advanced oxidation of hydrocarbons on surfaces is outlined. Following to a comparison of the reaction rates of atomic oxygen and ozone with hydrocarbons, as well as a discussion of the mean free pathlength of atomic oxygen at or near atmospheric pressure, results on surface cleaning in air with VUV radiation at 172 nm will be presented.