Metal optics is an inherent part of space instrumentation for years. Diamond turned aluminum (Al6061) mirrors are widely used for application in the mid- and near-infrared (mid-IR and NIR, respectively) spectral range. Aluminum mirrors plated with electroless nickel (NiP) expand the field of application towards multispectral operating instruments down to the ultraviolet wavelengths. Due to the significant mismatch in the coefficient of thermal expansion (CTE) between aluminum and NiP, however, this advantage occurs at the cost of bimetallic bending. Challenging requirements can be met by using bare beryllium or aluminum beryllium composites (AlBeMet) as a CTE tailored substrate material and amorphous NiP as polishable layer. For health reasons, the use of beryllium causes complications in the process chain. Thus, the beryllium approach is subjected to specific applications only. Metal optics has proven to be advantageous in respect of using conventional CNC and ultra-precision fabrication methods to realize complex and light-weighted instrument structures. Moreover, the mirror designs can be effectively optimized for a deterministic system assembly and optimization. Limitations in terms of dimensional stability over temperature and time are mainly given by the inherent material properties (figures of merit) of the substrate material in interaction with the polishing layer.
To find an optimal compromise, a thermal matched aluminum-silicon alloy (silicon contents ≈ 40 wt%) plated with NiP (AlSi40/NiP ) was investigated in a joined project of the Max Planck Institute for Astronomy MPIA and the Fraunhofer Institute for Applied Optics and Precision Engineering IOF. The main tasks of the project were the minimization of the bimetallic bending, the development of reliable stabilizing and aging procedures, and the establishment of a proven fabrication method.
This paper describes fundamental results regarding the optimization of the athermal material combination. Furthermore, the developed production chain for high quality freeform mirrors made of AlSi40/NiP is pointed out.
In 2017 the new hyperspectral DLR Earth Sensing Imaging Spectrometer (DESIS) will be integrated in the Multi-User-System for Earth Sensing (MUSES) platform  installed on the International Space Station (ISS).
The Gravity Recovery and Climate Experiment Follow-On (GRACE FO) is a space borne mission to map variations in the earth’s gravity field with an even greater accuracy than the first GRACE mission. GRACE FO is a collaborative project of NASA (USA) and GFZ (Germany) scheduled for launch in 2017. On GRACE the gravity field is reconstructed from a measurement of the distance variation between two satellites following each other in 200 km distance by use of a microwave ranging instrument. On GRACE FO a laser ranging interferometer (LRI) is added as a demonstrator in addition to the microwave. Moving from microwave range to optical wavelengths provides an improvement in distance measurement noise from some μm/√Hz to 80 nm/√Hz down to 0.01 Hz frequency. The criteria on the beam delivery system are demanding, in particular with respect to laser beam quality, wave front deviation and pointing as well as thermal and mechanical stability. Conventionally such a system can be manufactured with at least two special mounted lenses or an aspheric lens aligned with respect to the fiber end. However, the alignment of this optical system must be maintained throughout the mission, including the critical launch phase and a wide temperature range in orbit, leading to high alignment effort and athermal design requirements. The monolithic fiber-collimator presented here provides excellent optical and thermal and mechanical performance. It is a part of the LRI and located on the Optical Bench Assembly (OBA) which has already been described in [1, 3].
The optical system of the hyperspectral imager of the Environmental Mapping and Analysis Program (EnMAP) consists of a three-mirror anastigmat (TMA) and two independent spectrometers working in the VNIR and SWIR spectral range, respectively. The VNIR spectrometer includes a spherical NiP coated Al6061 mirror that has been ultra-precisely diamond turned and finally coated with protected silver as well as four curved fused silica (FS) and flint glass (SF6) prisms, respectively, each with broadband antireflection (AR) coating, while the backs of the two outer prisms are coated with a high-reflective coating. For AR coating, plasma ion assisted deposition (PIAD) has been used; the high-reflective enhanced Ag-coating on the backside has been deposited by magnetron sputtering. The SWIR spectrometer contains four plane and spherical gold-coated mirrors, respectively, and two curved FS prisms with a broadband antireflection coating. Details about the ultra-precise manufacturing of metal mirrors and prisms as well as their coating are presented in this work.
For optical systems consisting of metal (in general freeform) mirrors there exist several diamond turning fabrication approaches. These are distuingished by the effort in manufacturing and integration of the later system. The more work one puts into the manufacturing stage the less complicated is the alignment and integration afterwards. For example the most degrees of freedom have to be aligned in integration phase if every mirror of the system is fabricated as a single optical component. For a three mirror anastigmat with three freeform mirrors the degrees of freedom sum up to 18. Therefore the mirror fabrication itself is more or less easy, but the integration is very difficult. There are three major parts in the design and manufacturing process chain to be considered for tackling this integration problem. At the first position in the process chain there is the optical design occuring. At this stage a negotiation between manufacturing and design could improve manufacturability because of more possible integration approaches. The second stage is the mechanical design. Here the appropriate manufacturing approach is already chosen, but may be revisited due to incompatiblities with, e.g., stress specifications. The third level is the manufacturing stage. Here are different clamping approaches and fabrication methods possible. The current article will focus on an approach ("snap-together") where two mirrors are fabricated on one substrate and therefore a reduction of the number of degrees of freedom to be aligned are reduced to six. This improves the amount of time needed for the system integration significantly in contrast to a single mirror fabrication.
Proc. SPIE. 9346, Components and Packaging for Laser Systems
KEYWORDS: High power lasers, Crystals, Atomic force microscopy, Sapphire, Finite element methods, Laser crystals, Harmonic generation, Frequency conversion, Nonlinear crystals, Laser systems engineering
Lasers used for diverse applications from industry to fundamental science tend to increasing output powers. Some
applications require frequency conversion via nonlinear optical crystals, which suffer from the formation of temperature
gradients at high power operation which causes thermal lensing or destruction of the crystal due to tensile stresses. To
avoid these unwanted effects we joined a beta barium borate (BBO) crystal with sapphire disks serving as effective heat
spreaders due to their high thermal conductivity (thermal conductivity κ = 42 W/Km). Therefore, smooth and flat crystal
surfaces were joined by plasma-activated bonding. The joining relies on covalent bonds, which are formed via a
condensation reaction of the surfaces which are first connected by Van der Waals forces. The cleaned surfaces are
activated by plasma and brought into contact, pressed together and heat treated at a temperature of about 100°C. Special
attention has been paid to the cleaning of the surfaces. Therefor the surfaces have been evaluated before and after
treatment by means of atomic force microscopy. A stable connection has been formed successfully, which has been
tested in a proof of principle experiment and demonstrated efficient second harmonic generation at up to 253 W of input
power. Compared to a bare single BBO crystal it could be shown that the temperature within the crystal compound is
significantly reduced. Such hybrid structures pave the way for frequency conversion at kilowatts of average power for
future high power lasers.
Optical freeforms are increasingly gaining interest for optical systems like telescopes and spectrometers. This is a key topic of discussions for many years; however, the manufacturing process of freeform optics remains a challenging task whose complexity derives from the missing symmetry in freeform surfaces.
Ultra-precise manufacturing with diamond tools is an appropriate method to realize optical freeforms. Aspherical off axis mirrors machined similar to freeform or classical freeform mirrors like anamorphic mirrors can be fabricated in a deterministic process by using reference structures and correction loops. Diamond machining offers an excellent technology to meet the requirements regarding small values of surface deviation and low tolerances of position accuracy. Nevertheless, the typical micro-roughness of approximately 5 nm rms and the periodic turning structure set the limitation for diamond machined surfaces. The surfaces fulfill requirements for application in the Near Infrared (NIR) and Infrared (IR) spectral ranges, respectively. For smoothing the periodic structure, the diamond turning is combined with post polishing techniques like MRF (Magnetorheological Finishing) or computer assisted polishing. Therefore, the aluminum mirror has to be coated with amorphous nickel-phosphorous or silicon. Thus, the specification of applications in the visible (VIS) spectral range is reached. This process chain is interesting for a growing number of multi- and hyperspectral imaging devices such as telescopes and spectrometers based on all reflective metal optics.
The paper summarizes the fabrication of an optical bench for a high resolution IR telescope, discusses the results of post polishing mirrors for VIS telescopes, and shows an efficient and easy snap-together alignment strategy. The optical function of the TMA demonstrator built is an afocal imaging for a Limb-Sounder Instrument with a magnification of 4.5:1. Besides the design and manufacturing approach, the snap-together integration of the optical bench is presented, too. The presentation is finished with a forecast of a freeform IR telescope based on anamorphic mirrors.
We report on theoretical models of the interaction of ultra-short laser pulses with multilayer structures used in thin-film solar cells. A finite-difference based optical model of light propagation within the thin-film system is used to determine the 3D-distribution of absorbed laser power in the structure. The model includes the evolution of the density of charge carriers which may be driven either by direct absorption of the laser radiation or multi-photon absorption and impact ionization of highly excited carriers.
Depending on the excitation wavelength and pulse energy absorption occurs in different depths of the structure which has a large effect on the efficiency of the laser ablation process.
We report on theoretical and experimental investigations into electrostatic chuck designs for use in future e-beam
lithography on 450 mm Silicon wafers. Ultra-low thermal expansion glass (ULE) and Si infiltrated Silicon Carbide
(SiSiC) designs were evaluated by finite element modeling, subject to a mass budget of 8 kg. In addition to massive
chucks, light-weight designs were created by applying bore holes through the chuck body below its surface.
Considerable chuck bending under gravity is observed with classical kinematic 3-point mounts. Out-of-plane distortions
of about 1250 (650) nm and 400 (200) nm for the massive and light-weight designs of ULE (SiSiC), respectively, were
calculated. The corresponding surface in-plane distortions for a chucked Si wafer of standard thickness 925 μm amount
to about 3 (1.6) nm for the massive and 1 (0.5) nm for light-weight designs of ULE (SiSiC), respectively. By using the
standard 6th order polynomial correction upon e-beam writing, these values can be reduced to ≤0.7 nm for the massive
designs with both materials. Various pin-pattern configurations for an ideally flat chuck surface were adopted to
determine resulting wafer bending under the influence of electrostatic forces. At a typical electrostatic pressure of about
18 kPa, a square pin pattern of pin-pitch 3.5 mm and pin-diameter 0.5 mm results in wafer in-plane distortions <0.5 nm,
which is considered tolerable for obtaining the desired total overlay accuracy of <4 nm. The pin structure manufacturing
process for a corresponding ULE chuck surface was experimentally tested and verified. A nearly elliptic ULE plate,
slightly larger than the wafer, was structured with a Chromium hard-mask and subjected to low pressure reactive ion
etching to generate the pin-pattern. A homogeneity of about 7 % was obtained for the etching process, which is fully
sufficient with respect to resulting variations in electrostatic attraction.
We report on Finite Element Modeling (FEM) of the influence of heat load due to the lithographic exposure on the inplane
distortion (IPD) of 450 mm Si-wafers and hence on the effect of the heat load on the achievable image placement
accuracy. Based on a scenario of electron beam writing at an exposure power of 20 mW, the thermo-mechanical
behavior of the chuck and the attached Si wafer is modeled and used to derive corresponding IPD values. To account for
the pin structured chuck surface, an effective layer model is derived.
Different materials for the wafer chuck are compared with respect to their influence on wafer IPD and thermal
characteristics of the exposure process. Guidelines for the selection of the chuck material und suggestions for its cooling
and corrective strategies on e-beam steering during exposure are derived.
The objective of this paper is a new accommodating opto-mechanical model of the aging human eye for basic
simulations of presbyopia, especially of the lens. The lens, consisting of cortex and nucleus, of the aging human eye is
mechanically simulated by a FEM model with the program ANSYS. The model results in physiologically correct
parameters, and is used as input for a complete optical eye model, implemented in the software ZEMAX. The optical
performance of the model corresponds fully with clinical data and the model represents the changes in the mechanical
and optical parameters during accommodation and due to the aging process. It is suitable for optical and mechanical
simulation; therefore, for example, different possible treatments for presbyopia can be simulated. Furthermore first
investigations of stray light due to the laser treatment and their impact on visual performance are presented.
We report on measurements of the breaking stress of glass substrates welded with ultrashort laser pulses. Femtosecond
laser pulses at repetition rates in the MHz range are focused at the interface between two substrates, resulting in
multiphoton absorption and heat accumulation from successive pulses. This leads to local melting and subsequent
resolidification results in the formation of strong bonds at the interface. The achievable breaking stress of this flexible
and local bonding process is discussed in detail in dependence of the processing parameters.
The major challenge in the development of monolithic kW class CW fiber lasers is the efficient conversion of pump
photons into a high brightness laser beam under the constraints of heat management, long term stability and
nonlinearities. This article reviews the interaction of some fiber related aspects as e.g. fiber core composition,
photodarkening and modality, as well as their influence on system complexity and power scalability. Recent work on
active fibers, pump couplers, mode field adaptors and other fiber-optic components will be presented.
This paper describes a new athermal approach for high performance metal optics, particularly with regard to extreme
environmental conditions as they usually may occur in terrestrial as well as in space applications. Whereas for mid
infrared applications diamond turned aluminium is the preferred mirror substrate, it is insufficient for the visual range.
For applications at near infrared wavelengths (0.8 μm - 2.4 μm) as well as at on cryogenic temperatures (-200°C)
requirements exist, which are only partially met for diamond turned substrates. In this context athermal concepts such as
optical surfaces with high shape accuracy and small surface micro-roughness without diffraction effect and marginal loss
of stray light, are of enormous interest.
The novel, patented material combination matches the Coefficient of Thermal Expansion (CTE) of an aluminium alloy
with high silicon content (AlSi, Si ≥ 40 %) as mirror substrate with the CTE of the electroless nickel plating (NiP).
Besides the harmonization of the CTE (~ 13 * 10-6 K-1), considerable advantages are achieved due to the high specific
stiffness of these materials. Hence, this alloy also fulfils an additional requirement: it is ideal for the manufacturing of
very stable light weight metal mirrors.
To achieve minimal form deviations occurring due to the bimetallic effect, a detailed knowledge of the thermal
expansion behavior of both, the substrate and the NiP layer is essential. The paper describes the reduction of the
bimetallic bending by the use of expansion controlled aluminium-silicon alloys and NiP as a polishing layer. The
acquisition of CTE-measurement data, the finite elements simulations of light weight mirrors as well as planned
interferometrical experiments under cryogenic conditions are pointed out. The use of the new athermal approach is
Aspherical surfaces for imaging or spectroscopy are a centerpiece of high-performance optics. Due to the high
alignment sensitivity of aspheric surfaces, reference elements and interfaces with a tight geometrical relation to
the mirror are as important as the high quality of the optical surface itself.
The developed manufacturing method, which accounts for the shape and also for the position of the mirror
surfaces, allows controlling and precisely correcting not only the form, but also the alignment of reference marks,
interfaces or even other mirrors in the sub-assembly using diamond turning. For Korsch or TMA telescopes it is
also possible to diamond turn whole sub-assemblies containing two or more mirrors with a relative position error
as low as the machine precision. Reference elements allow the correction of the shape and position of mirrors as
well as the position of interfaces for system integration. The presented method opens up a novel manufacturing
strategy to enhance the relative positioning accuracy of optic assemblies by one order of magnitude.
In extreme ultraviolet lithography (EUVL), the mask hangs on an electrostatic chuck and is moved laterally during
exposition. For proper control of the chucked mask under corresponding inertial forces, static friction of the mask on
the chuck is critical and an important input parameter for reliable theoretical modelling.
To determine static and dynamic friction values, measurements were performed in vacuum on a mask blank with a test
chuck, smaller than a real EUVL mask chuck, but otherwise nearly identical in its characteristics. Experimental results
were obtained at various voltages for a materials combination of Low Thermal Expansion Glass (LTEM) for the pin chuck surface and a mask blank with a chromium metal backside metallisation, respectively. Dynamic friction was found to be only marginally smaller than static friction and values in the range from 0.27 to 0.33 were determined for the static friction coefficient under vacuum conditions.
Laser structuring of different types of thin film layers is a state of the art process in the photovoltaic industry. TCO layers
and molybdenum are structured with e.g. 1064 nm lasers. Amorphous silicon, microcrystalline silicon or cadmium
telluride are ablated with 515/532 nm lasers. Typical pulse durations of the lasers in use for these material ablation
processes are in the nanosecond range.
Up to now the common process for CIS/CIGS cells is needle structuring. Hard metal needles scribe lines with a width of
30 to 60 μm into the semiconductor material. A laser technology would have some advantages compared to mechanical
scribing. The precision of the lines would be higher (no chipping effects), the laser has no wear out. The dead area
(distance from P1 structuring line to P3 structuring line) can be significantly smaller with the laser technology.
So we investigate the structuring of CIS/CIGS materials with ultra short pulse lasers of different wavelengths. The
ablation rates and the structuring speeds versus the repetition rates have been established. For the different layer
thicknesses and line widths we determined the necessary energy densities. After all tests we can calculate the possible
reduction of the dead area on the thin film module. The new technology will result in an increase in the efficiency per
module of up to 4 %.
We report on the high power amplification of narrow linewidth laser radiation with close to diffraction limited beam
quality using a large mode area photonic crystal fiber amplifier. The observation of threshold-like higher order mode
amplification by transverse spatial-hole burning at the highest power level is reported. The measured M² stays below 1.3
but increases at the critical power level, where the fundamental mode turns into the next higher order mode. At the
maximum power of 1.2 kW a linewidth of <80 pm limited by self-phase modulation is obtained.
We report on a novel concept for monolithic pump combining technology to integrate efficiently multi pump fiber
channel into a double clad ytterbium doped fiber. The proposed structure consists of a dichromatically coated planar
convex lens spliced to an Ytterbium-doped double-clad photonic crystal fiber surrounded by multiple pump fibers. The
lens is also used as a protecting end cap where the laser beam expands before exiting the surface. The pump fibers are
also attached in this lens circularly surrounding fibers. The lens images these pump fibers end facets into the pump
core, where the lens surface is coated by a dichroic mirror (reflective for 980 nm, transmissive for >1030 nm). The allglass
structure, assembled by laser splicing, makes the system stable, efficient and suitable for high power operation.
We selected 5 channels as testing channels among 14 pump channels (200 μm, NA=0.12) in order to confirm reliability
of the system. The coupled pump power efficiency into the 500 μm core with NA=0.5 was over 80% and typical slope
efficiency of the laser output is over 70%. Theoretical analysis was discussed in order to get optimized parameters and
scaling this type of coupler to higher average powers is considered. With the monolithic pump combining technologies,
we confirmed that the proposed device has a potential application not only in kW range high power fiber lasers but also
compact photonic devices.
This paper reports on a novel construction of a deformable mirror for laser beam shaping. The deformable mirror is
actuated by screen-printed thick film piezoceramic unimorphs based on lead zirconate titanate (PZT). Different actuator
layouts are realized and will be presented. We use Low Temperature Cofired Ceramics (LTCC) as a substrate material
with a metallization as reflective surface. LTCC offers easy integration of holding structures. The reflective mirror
surface is electroplated copper. After deposition, the copper layer is diamond machined to achieve excellent optical
surface quality <10 nm (rms). We build deformable mirrors with 1, 13 and 19 actuators and a total stroke of more than
20 μm and characterize them with a wave front sensor.
The design limits of grating array spectral sensors are discussed. The limit of a grating spectrometer with respect
to the resolution is given by the diffraction limit of the grating. To approach the limit for the visible spectral region the entrance slits should reach a width of 2 μm and larger depending on wavelength and numerical aperture. The detector pixel sizes should be in the same range, which is achieved virtually by the discussed double array arrangement with a transmissive, static slit array and detector array. A number of techniques are applied for optimizing the performance as well as for miniaturization. A sub-pixel imaging including a sub-pixel analysis based on the double array arrangement virtually reduces the detector pixel sizes down to about 20%. To avoid the imaging aberrations the spectra is imaged from different entrance positions by the entrance slit array. The throughput can be increased by using a two dimensional entrance slit array, which includes a multiplex pattern or a fixed adaptive pattern. The design example of a UV-Raman spectral sensor is presented including spectral measurements.
Modern telescopes for space applications use complex optical elements like aspheres or freeforms. For the multispectral
pushbroom scanner for spaceborne Earth remote sensing the Jena-Optonik GmbH has developed a Jena-Spaceborne-
Scanner JSS product line. The optic of JSS-56 imager is realised by a Three-Mirror-Anastigmat (TMA) telescope
designed in aluminium . For brilliant pictures, mirrors with high shape accuracy and very smooth surfaces are
required. The combination of precise diamond turning and post polishing techniques enables the classical infrared
application for the visible and ultra-violet range. A wide variety of complex mirror shapes are feasible. A special new
solution for lightweight design was applied. Ultra precise metal mirrors with aspherical surface are developed at the
Fraunhofer IOF from design to system integration.
This paper summarizes technologies and results for design, fabrication and surface finish of ultra lightweight aspherical
metal mirrors for novel TMA telescopes.
A PZT thick-film is printed on an Al2O3-Substrate, generating a cantilever monomorph. A task of positioning with two
degrees of freedom is successfully fulfilled. It is realized by two parallel arranged cantilevers that are mechanically
combined with a bar with solid hinges. The solid hinges allow flexibility for different amounts of bending of the two
cantilevers, while the bar permits a stiff support for a lens. As the bar underlies very small torsion there is no stress
induced change in the index of refraction of the lens. Different combinations of hinges are simulated and practically
tested. In the presented work, a lens is successfully positioned in front of a laser diode. The loss of the coupling
efficiency due to the shrinking of the adhesive joint can be scaled down. The paper presents the theoretical work
including the report on analytic and FEM simulation of both deflection and stress. The practical validation is also
presented. A simple sensor system is used to find an optimized position of the lens in front of the diode. This position is
automatically held over a long period of time. With the fabrication of the actuator using thick-film printing and laser
cutting a low cost device is built.
Diffraction limited 20x Schwarzschild objectives have been fabricated for various applications at 13.5nm wavelength. For this purpose the major parts of the whole technology chain for the realization of diffraction limited reflective optical systems working in the EUV spectral region have been established. This chain includes: optical design of the system, mechanical construction of mounting structures on the basis of extensive stress and thermal analysis, development of adhesive free mountings, high-reflective Mo/Si multilayer coatings for use at 13.5nm wavelength, assembly of the whole objective system, development of adapted semiconductor detectors for 13.5nm. The realized Schwarzschild objectives with a numerical aperture of NA=0.2 have been integrated into different optical set-ups such as a table top scanning micro exposure tool and an EUV microscope. The EUV micro exposure tool is currently used for various EUVL-related applications such as investigations of resolution limiting factors and EUV resist sensitivity test stand. Properties and performance of both the Schwarzschild objective and the optical set-up are presented in the paper.
The different concepts of combining fiber lasers for power-scaling are discussed. We report on three combined fibers with an output power of 100 W. Several proposals are made for further power scaling and the capacitance of a grating is tested in a simulation-experiment.
A 21x Schwarzschild microscope lens for the EUV spectral range with a numerical aperture of 0.2 was designed and fabricated. The mechanical design of the lens had to comply with high requirements on surface figure amounting to 0.4 nm r.m.s. error for both mirrors. An optimized mirror mount was developed which is based on solid state hinges. In particular, gravity load, intrinsic stresses of the multilayer reflective coating as well as mounting forces and possibilities for mirror adjustment had to be considered. To provide a completely hydro-carbon free design the hinges were connected to the mirror by flux-less soldering.
Most recently the output power of fiber lasers with diffraction limited beam quality has been significantly increased. Further power scaling is usually limited by damage of the fiber end facets, thermo-optical problems or nonlinear effects. Microstructuring the fiber adds several preferable features to the fiber to overcome these restrictions. We review the advantages of rare-earth-doped photonic crystal fibers for power scaling of fiber lasers to the multi kW range with excellent beam quality.
Precise adjustment of the optical components may be achieved by stepped transfer of momentum via special stroke actuators (impulse hammers), which act onto a pre-stressed fiber- optical component. The motion of the component is controlled by a computer and a measurement device. The present paper discusses theory and experiment of this adjustment method, in particular motion behavior of pushed components under the influence of applied momentum, pre-stressing and frictional forces. Additionally it describes generically the wide application range of this adjustment method. In particular the article describes an innovative, automatic adjustment machine (robot) for the alignment of a single- mode fiber assembly, which was developed by the German Fraunhofer-Institute for Applied Optics and Precision Engineering (IOF) in collaboration with Agilent Technologies Inc., a global technology leader in communications, electronics and life sciences. The achieved adjustment accuracy for the fiber optical assembly is in a low micron range for the focusing motion and in a sub-micron for entering of the optics.
As a part of the Acquisition and Guidance Unit for the Gemini project a light-weight, 50 cm flat mirror has been designed at the Fraunhofer Institute for Applied Optics and Precision Mechanics in Jena as a subcontractor of the Carl Zeiss Jena company. A light-weight design of the mirror and its mount was essential since the total mass of the whole assembly including the positioning system was limited to 50 kg while interferometric quality of the mirror surface was required for arbitrary orientation. The overall surface error was below 54 nm r.m.s. while 27 nm was achieved in the central part. The mirror was fabricated from low-expansion glass ceramics to avoid thermally induced deformations. By milling pockets into its rear surface the mass of the mirror was reduced by 70%. The mirror is mounted cinematically via six solid-state hinges to three steel levers. The levers are connected to the mount frame at their centers via ball-and- sphere joints. This arrangement determines the position of the mirror uniquely while it allows for the thermal expansion of the mount frame. The position of the mirror as well as its tilt around an axis perpendicular to the optical one may be controlled a precision of 20 micrometers and 3 arcsec, respectively. The tilt axis is driven directly by two high- torque motors. To avoid an excessive power consumption of the motors the torque of the mirror head to be compensated for by a counterweight mechanism. The mirror may be deployed into the optical path using spindle driven linear rails.
During the development of a low cost industrial optical sensor an unexpected drift phenomenon has shown to be critical to performance. The sensor is based on LED's as light sources and the main source of error could be tracked to the instability of the spatial radiation pattern of the LED's. This instability due to the construction of the sensor introduced an error in the intensity feedback loop. Alternative designs including a Y-coupler, a scattering arrangement and a mirror beam splitter have been investigated and the results are presented.
In the next few years a new chip-generation with structure sizes well below 100 nm and high complexity will require novel, so-called 'future lithography' processes. One of these new technologies is the Ion Projection Lithography. Within the framework of a large European project lead by SIEMENS, the necessary technologies are developed and the first pilot system will be built. In this system, one of the most important units is a high precision wafer stage. The heart of the stage system is the so-called metrology - plate with integrated electrostatic wafer chuck and handling unit. The design of this novel stage system is described in this contribution. Extensive FEM-simulations from the basis of the present design. All major components are made from glass-ceramics to guarantee the highest possible thermal and mechanical stability. Not only in the field of lithography many modern precision mechanical systems require position tolerances in the sub-micrometer and seconds of arc range. Strong systems solutions can be developed by the effort of glass-ceramics and new and traditional manufacturing processes.
Using a drop-on-demand print head allows for PC-controlled production of various types of microlenses as well as lens arrays. The possibility to place microlenses on arbitrarily shaped substrates allows for novel optical elements like beam splitters or non-planar scattering discs. Another interesting possibility opened by pre-shaped substrates is the production of concave lenses, which are key elements for aberration correction in micro-optical systems.
We show that dispersion compensation over 70 km of a standard optical fiber at 20 Gbit/s can be achieved by using a strip waveguide configuration which consists of two dissimilar guides and is only a few centimeters long. Moreover, any required amount of third-order dispersion can also be compensated for.