This PDF file contains the front matter associated with SPIE Proceedings Volume 7716, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

Diamond machining originates from the 1950s to 1970s in the USA. This technology was originally designed for machining of metal optics at macroscopic dimensions with so far unreached tolerances. During the following decades the machine tools, the monocrystalline diamond cutting tools, the workpiece materials and the machining processes advanced to even higher precision and flexibility. For this reason also the fabrication of small functional components like micro optics at a large spectrum of geometries became technologically and economically feasible. Today, several kinds of fast tool machining and multi axis machining operations can be applied for diamond machining of micro optical components as well as diffractive optical elements. These parts can either be machined directly as single or individual component or as mold insert for mass production by plastic replication. Examples are multi lens arrays, micro mirror arrays and fiber coupling lenses. This paper will give an overview about the potentials and limits of the current diamond machining technology with respect to micro optical components.

Replication technology for microstructures is an essential issue for transforming expensive microstructures to cheap polymer replicas. Hot embossing has proven to be a suitable technology to fulfil the requirements of industrial applications and to fill the gap between the laboratory and the consumer market. Compared to injection moulding, hot embossing creates microstructures with lower internal stress and is therefore highly suitable for the replication of stress sensitive components, as required, e. g., for optical applications. This paper gives an overview over the hot embossing process, the technology, and shows the potential for the replication of optical components and systems.

Laser beam shaping is a key issue for the photonic integration of VCSEL sources. Most of the techniques proposed to integrate micro-optics elements onto VCSEL devices imply either a hybrid assembly or a photolithography step, whose precision limits the accuracy of lens alignment relatively to the VCSEL source. We present here a new method for self-fabrication of microtips on Vertical-Cavity Surface-Emitting Lasers (VCSELs) by means of Near Infra- Red (NIR) photo-polymerization. This approach is based on a single fabrication step, implementing novel photopolymers sensitive at the lasing wavelength. Consequently the process is triggered by the laser source itself and can be applied easily to VCSEL devices during their electro-optic characterization. The method we have developed for tips fabrication is detailed as well as corresponding optical properties. The applications of this new and simple method concern laser light focusing and collimation for integrated micro-systems, coupling to fibers for optical communications as well as novel micro-probes fabrication for near-field optical microscopy.

The recent developments in optics and photonics require novel, simple and fast methods of fabrication of miniaturized integrated devices with well controlled optical functions. Among other optical elements, microlenses or microcavities integrated on optical fibers, waveguides of miniaturized laser sources revealed of great interest due to their applications for coupling, focusing of collimating light. A simple and low cost technique to implement a polymer micro-component at the extremity of optical fiber was proposed. The process is based on a spatially controlled photopolymerization that is induced by a laser beam emerged from the optical fiber. Thus, the microlens is directly aligned with the fiber core. The polymer tips have shown to exhibit various shapes as a function of the photonic parameters and the chemical composition of formulation. In this paper, we will detail the mechanisms leading to the building up of the polymer microtips by self-guiding polymerization and we will illustrate the great flexibility of this process in terms of materials, geometry and writing wavelength. Then we will focus on some applications in optical coupling between fibers and sensors in order to demonstrate the interest of this simple and flexible approach for polymer micro-optics implementation.

Nowadays novel micro-fabrication and wafer-based manufacturing approach allows realizing micro-optics in a way scientists have dreamt for generations, in particular, utilizing nano-imprint lithography as fabrication tooling enables greatly accelerating the micro-optics technology to its frontier. In this report, we present wafer-scale fabrication of various types of micro-optical elements based on photoresist, benzocyclobutene, photocurable imprint resist, and semiconductor materials by using thermal reflow, reactive ion etching, and imprint techniques. Especially, several concave or convex 3-dimensional micro-optical structures shaped by imprint method are detailed. These micro-optical elements can be monolithically or hybrid integrated onto optoelectronics devices, such as photodetectors and emitters as optical beam focuser, collimator, filter, or anti-reflectance elements. As application examples, polymer microlenses were integrated directly on the top of UV dual functional devices and quantum dot long wavelength infrared photodetectors, respectively.

Femtosecond laser photo-polymerization of zirconium-silicon based sol-gel photopolymer SZ2080 is used to fabricate micro-optical elements with a single and hybrid optical functions. We demonstrate photo-polymerization of the solid immersion and Fresnel lenses. Gratings can be added onto the surface of lenses. The effective refractive index of polymerized structures can be controlled via the volume fraction of polymer. We used woodpile structure with volume fraction of 0.65-0.8. Tailoring of dispersion properties of micro-optical elements by changing filling ratio of polymer are discussed. Direct write approach is used to form such structures on a cover glass and on the tip of an optical fiber. Close matching of refractive indices between the polymer and substrate in visible and near infra red spectral regions (n_SZ2080 = 1.504, n_glass = 1.52) is favorable for such integration. The surface roughness of laser-polymerized resits was ~30 nm (min-max value), which is acceptable for optical applications in the visible range. For the bulk micro-optical elements the efficiency of 3D laser polymerization is increased by a factor ~ (2 - 4) × 10² times (depends on the design) by the shell-formation polymerization: (i) contour scanning for definition of shell-surface, (ii) development for removal of nonfunctional resist, and (iii) UV exposure for the final volumetric polymerization of an enclosed volume.

Liquid lenses are becoming important optical devices for a wide range of applications, from mobile-phone cameras to biological imaging modalities. Their biggest advantage is their potential to have a variable focus that can be changed to obtain a different radius of curvature and thus optical power. The tunability of such micro-lenses could be of great interest to the field of micro-optics thanks to the possibility to achieve focus tuning without moving parts and thus favouring the miniaturization of the optical systems. A special class of tunable liquid micro-lenses is presented here. They are generated by electro-wetting effect under an electrode-less configuration. The lensing effect is induced by the pyroelectric effect on polar dielectric crystals we named pyroelectric-electrodeless-electro-wetting (PEEW). If a thin liquid film is spin coated on a z-cut lithium niobate wafer, the pyroelectric effect causes surface-charges at the liquidsolid interface when the substrate suffers temperature changes. Electric charges build up on the substrate's surface by pyroelectricity and are responsible for the variation of the liquid contact angle, thus forming liquid micro-lenses. The temperature variation can generate a pattern of electric charges onto the surface of the crystal when ferroelectric domain pattern is micro-engineered. Different types of lenses: spherical, cylindrical and toroidal have been formed. Any temperature change allows the liquid layer to become a tunable micro-lens array, showing a strong focusing effect. A digital holography technique is used to characterize the transmitted wavefront during focusing and focal length variation in the millimetre range is observed. Formation process is illustrated while interferometric characterization and imaging properties are analyzed and discussed.

We describe the electro-optical behavior of polymer stabilized liquid crystal (PSLCs) networks used for the development of electrically variable focus lenses. We start with a short review of mechanisms influencing the performance of those lenses, including the most important one : the light scattering. Then the role of the polymer chain morphology in electrically controllable molecular reorientation and formation of orientation defects in PSLCs is investigated. We use two non mesogene monomers, with respectively one and two functionalities, to create two different degrees of cross-linking in PSLCs. By using optical polarimetry and scattering experiments, we investigate the defect formation in those PSLCs, outline the presence of 3D orientational defects and show that the PSLCs with higher crosslinking demonstrate better electro-optical reversibility.

We present measurements and simulations of membrane-based micro-lens stacks, tunable in focal length in the range of 10mm to 50mm without chromatic aberration. The pressure-actuated, liquid-filled, membrane-based micro-lenses are fabricated by an all-silicone molding approach and consist of three chambers separated by two highly flexible silicone-membranes. Based on the idea of the classical achromatic Fraunhofer doublet, two different liquids with suitable optical properties are used. Pressure-dependent surface topologies are measured by profilometry for determining the correlation between refraction and applied pressure. The profiles are fit to polynomials; the coefficients of the polynomials are pressure-dependent and fit to empirically determined functions which are then used as an input for optical ray-tracing. Using this approach, the focal length is tunable while compensating for chromatic aberration by suitably applied pressures.

An innovative approach for voltage-tunable optical gratings based on dielectric elastomer actuators (DEAs) using electro active polymers is presented. Sinusoidal surface gratings, holographically written into azobenzene containing films, are transferred via nanoimprinting to DEAs of different carrier materials. We demonstrate that the surface relief deformation depends on the mechanical and geometrical properties of the actuators. The tested DEAs were made using commercially available elastomers, including a tri-block copolymer poly-styrene-ethylene-butadiene-styrene (SEBS), a silicone polydimethylsiloxane rubber (PDMS) and commonly used polyacrylic glue. The polyacrylic glue is ready to use, whereas the SEBS and the PDMS precursors have to be processed into thin films via different casting methods. The DEA material was pre-stretched, fixed to a stiff frame and coated with stretchable electrodes in appropriate designs. Since the actuation strain of the DEA depends strongly upon the conditions such as material properties, pre-stretch and geometry, the desired voltage-controllable deformations can be optimized during manufacturing of the DEA and also in the choice of materials in the grating transfer process. A full characterization of the grating deformation includes measurements of the grating pitch and depth modulation, plus the change of the diffraction angle and efficiency. The structural surface distortion was characterized by measuring the shape of the transmitted and diffracted laser beam with a beam profiling system while applying an electro-mechanical stress to the grating. Such surface distortions may lead to decreasing diffraction efficiency and lower beam quality. With properly chosen manufacturing parameters, we found a period shift of up to 9 % in a grating with 1 μm pitch. To describe the optical behavior, a model based on independently measured material parameters is presented.

We have recently reported a novel approach to producing voltage programmable optical devices in which static wrinkles are created at the surface of a thin film of oil [Nature Photonics 3(7), 403 (2009)]. The oil coats a 2d electrode pattern and dielectrophoretic forces created from the non-uniform fringing electric field profiles near to the electrodes determine how this pattern is "imprinted" at the remote oil/air interface. Sinusoidal wrinkles have been created on the surface of decanol oil with pitch lengths of between 20 and 240 micrometers and have been rapidly switched on in less than 40 microseconds. Non-sinusoidal surface wrinkles with higher harmonics appear when electrodes with the larger pitches are used in conjunction with an oil that has a lower dielectric constant, for example hexadecane. It is found that the higher Fourier components of the shape of the periodic wrinkle decay faster than the fundamental component as the thickness of the oil film is increased.

A new generation of liquid lenses based on electrowetting has been developed, using a multi-electrode design, enabling to induce optical tilt and focus corrections in the same component. The basic principle is to rely on a conical shape for supporting the liquid interface, the conical shape insuring a restoring force for the liquid liquid interface to come at the center position. The multi-electrode design enables to induce an average tilt of the liquid liquid interface when a bias voltage is applied to the different electrodes. This tilt is reversible, vanishing when voltage bias is cancelled. Possible application of this new lens component is the realization of miniature camera featuring auto-focus and optical image stabilization (OIS) without any mobile mechanical part. Experimental measurements of actual performances of liquid lens component will be presented : focus and tilt amplitude, residual optical wave front error and response time.

Up to now, multi channel imaging systems have been increasingly studied and approached from various directions in the academic domain due to their promising large field of view at small system thickness. However, specific drawbacks of each of the solutions prevented the diffusion into corresponding markets so far. Most severe problems are a low image resolution and a low sensitivity compared to a conventional single aperture lens besides the lack of a cost-efficient method of fabrication and assembly. We propose a microoptical approach to ultra-compact optics for real-time vision systems that are inspired by the compound eyes of insects. The demonstrated modules achieve a VGA resolution with 700x550 pixels within an optical package of 6.8mm x 5.2mm and a total track length of 1.4mm. The partial images that are separately recorded within different optical channels are stitched together to form a final image of the whole field of view by means of image processing. These software tools allow to correct the distortion of the individual partial images so that the final image is also free of distortion. The so-called electronic cluster eyes are realized by state-of-the-art microoptical fabrication techniques and offer a resolution and sensitivity potential that makes them suitable for consumer, machine vision and medical imaging applications.

We present design and realization concepts for thin compound eye cameras with enhanced optical functionality. The systems are based on facets with individually tunable focus lengths and viewing angles for scanning of the object space. The active lens elements are made of aluminum nitride (AlN)/nanocrystalline diamond (NCD) membranes. This material system allows slow thermally actuated elements with a large deformation range as well as fast piezoelectric elements with a smaller deformation range. Due to the extreme mechanical stability of these materials, we are able to realize microoptical components with optimum surface qualities as well as an excellent long-term stability. We use facets of microlenses with 1 mm in diameter and a tunable focusing power to compensate for the focus shift for different viewing angles during the scanning procedure. The beam deflection for scanning is realized either by laterally shifting spherical elements or by a tunable microprism with reduced aberrations. For both actuators we present a design, fabrication concept and first experimental results.

The integration of camera modules in portable devices is increasing rapidly. At the same time, their size is shrinking due to the need for mobility and reduction of costs. For this purpose, an ultra-compact imaging system has been realized, which adapts the multichannel imaging principle of superposition compound eyes known from nocturnal insects. The application forms an erect image by using a pair of microlens arrays with slightly different pitches, which is also known as "Gabor superlens". The microoptical design was optimized by using numerical ray tracing methods with respect to the capabilities of state-of-the-art microoptics fabrication technology. Additional aperture/diaphragm layers and a field lens array had to be introduced in order to avoid channel cross talk. As a result, the optical performance is comparable to that of miniaturized conventional lens modules. However, the fabrication of the microoptical Gabor superlens is kept simple and scalable in terms of wafer-level technology due to the use of microlens arrays with low sag heights and small microlens diameters.

The availability of miniature imagers enables endoscopic systems with simplified integration. Here, the optical elements together with the imager are located at the distal end of these so called video endoscopes. The overall system can be flexible since no relaying optics is required in order to image the object at a remote position. Compared to conventional flexible systems based on light guiding fiber bundles, higher spatial resolutions can be achieved due to the ever decreasing pixel size in CMOS imager fabrication technology. We propose system designs and prototypes for f/4, 3mm outer diameter endoscopes with 70° and 110° field of view using a CMOS imager with 650x650 pixels of 2.8μm pitch. The systems are based on a simplified and rugged integration using a single polymer lens made by injection molding, a GRIN lens and a dispensed lens made of UV curing material allowing for high performance paired with low fabrication cost allowing for the usage as a disposable unit. Additionally, a side view system angled at 30° is presented based on a tilting reflection prism requiring minimum construction space allowing for an outer diameter of 3mm.

Today's infrared focal plane arrays concentrate in a small volume of typically 1 cm³ the results of three decades of research in microelectronics and packaging. Several technological breakthroughs have already been achieved leading to the development of infrared focal plane arrays (IRFPA's) for high-performances applications requiring spatial and thermal resolution, also for low-cost and high-manufacturing volumes (technology of uncooled micro-bolometers). The next step is to reduce the optics and make it compatible with the successful IRFPA's fabrication technology. This paper presents some methods and technologies we are exploring for high-performance and small infrared systems. These developments have led to a tool box of micro-concepts described by an optical function (imagery or spectrometry) integrated in the vicinity of the IRFPA. For this, old optical concepts have been revisited (pinhole optics, Talbot effect) and first demonstrations of original IRFPA-based micro-optical assemblies will be given.

Programmable liquid-crystal devices for high-resolution spatial shaping of ultrashort-pulsed laser beams promise to be an alternative approach to passive microoptical structures. In former experiments we demonstrated that depositionfabricated nanolayer lenses and axicons can serve as low-dispersion, damage resistant, ultrabroadband microoptical components. With small-angle layer microaxicons, robust wavefront sensors and 2D autocorrelators were built up with them which took advantage of stable and tilt-independent nondiffracting propagation. The flexibility of the thin-film design, however, was limited with respect to the dynamic range. For adaptive applications, information encoding, image transfer and data storage, addressable and phase variant components are required. Recently, phase-only reflective liquidcrystal- on-silicon spatial light modulators (LCoS-SLMs) became available. By analyzing the pulse transfer behavior in spectral and temporal domain it was shown that selected versions of LCoS-SLMs are capable to shape 10-fs pulses with marginal distortion. Variable arrays of pulsed Bessel-like beams and nondiffracting complex patterns were shaped experimentally and related applications are discussed. The adaptive correction of aberrations in nondiffracting tubular beams on microscale is demonstrated. The unique properties of programmable beam patterns of well controlled propagation promise the coverage of fields of entirely new photonic applications.

Optically pumped polymer photonic crystal band-edge dye lasers are presented. The photonic crystal is a rectangular lattice providing laser feedback as well as an optical resonance for the pump light. The lasers are defined in a thin film of photodefinable Ormocore hybrid polymer, doped with the laser dye Pyrromethene 597. A compact frequency doubled Nd:YAG laser (352 nm, 5 ns pulses) is used to pump the lasers from above the chip. The laser devices are 450 nm thick slab waveguides with a rectangular lattice of 100 nm deep air holes imprinted into the surface. The 2-dimensional rectangular lattice is described by two orthogonal unit vectors of length a and b, defining the ΓP and ΓX directions. The frequency of the laser can be tuned via the lattice constant a (187 nm - 215 nm) while pump light is resonantly coupled into the laser from an angle (θ) depending on the lattice constant b (355 nm). The lasers are fabricated in parallel on a 10 cm diameter wafer by combined nanoimprint and photolithography (CNP). CNP relies on a UV transparent quartz nanoimprint stamp with an integrated metal shadow mask. In the CNP process the photonic crystal is formed by mechanical deformation (imprinting) while the larger features are defined by UV exposure through the combined mask/mold.

Currently, one may find a wide variety of approaches for integrated lab-on-chip systems developed for applications in the biomedical field. Our contributions within the area of polymer based photonic systems are presented here. We are utilizing mass production techniques and head for lab-on-a-chip systems with solely optical and fluidic interfaces, avoiding electrical interconnects. Fluidic structures are implemented in the chips mainly by using the same technologies, which are chosen to create the optical elements. While photonic structures may require dimensions in the sub-100 nm range, microfluidic channels are more than one order of magnitude above this regime. Nevertheless, our approach allows for a limited number of process steps by simultaneous multiscale fabrication. Organic semiconductor lasers are generated by evaporating a thin film of photoactive material on top of a distributed feedback (DFB) grating. Gratings are replicated by hot embossing into poly(methyl methacrylate) (PMMA) bulk material. The lasing wavelength in the visible light regime of the on-chip lasers is selected by altering the thickness of the vacuum deposited organic semiconductor active material or the DFB grating period. Waveguides are monolithically integrated in PMMA via photodegradation through deep ultraviolet irradiation. The coupling of laser light into these waveguides is optimized. Hence, laser light is guided to an interaction zone with a biological sample in the microfluidic channel on chip. Micro-optical cavities are designed and processed to be functionalized for detecting biological binding events in the channel. Surface functionalization, e.g. by Dip-Pen Nanolithography, is carried out for integrated label-free detection as well as for fluorescence excitation.

Fluorescence detectors are applied for various applications in biomedical research, e.g. for pH-sensoring or single-cell detection. Free space optical systems offer the advantage of compact and efficiently integrated systems with benefits in the terms of systems alignment and optical functionality. On the other hand, due to the lab-on-a-chip character many fluidic systems, such as segmented flow systems, are very compact and thus compatible with integrated optical systems. We discuss the potential of the integration of the segmented flow approach in complex free space optical microsystems. The design and realization of a highly integrated fluorescence detector is demonstrated. The system is fabricated by ultra precision micromilling which allows one to monolithically integrate freeform optical elements for optimized optical performance.

We present our research on integrated optical Talbot interferometers for particle mass concentration measurements. For optimum integration of highly sensitive optical measurement systems we apply a planar emitter-receiver-unit with a vertical cavity surface emitting laser (VCSEL) at 850 nm as light source. The optical system is integrated into a planar transparent PMMA (polymethylmethacrylate) substrate. We suggest a planar integrated free-space optical system for monitoring the particle mass concentration of polydisperse suspensions. Thorough simulations of the optical sensor show that for the required regime of particle concentration and particle size distribution (PSD) turbidity measurements where the attenuation of a light beam is evaluated for example at different wavelengths do not provide the required measurement precision. We therefore propose a system where the probe beam even though sent through the system is blocked before reaching the detector by an interferometric setup. The stray light originating from the particles is exploited for the measurement. For our application we focus on particles with sizes in the range 1 - 120 μm and particle mass concentrations in the range of 1-10 mg/L. In this case significant strength of the scattering signal only appears in small angles relative to the incident probe beam (forward scattering). The probe beam and the stray light thus overlap to a large extent. Our sensor concept is based on a monolithically integrated Talbot interferometer. Two properly aligned diffraction gratings are used to remove the primary beam. We use a stripe detector as second grating. The stray light causes perturbations within the formation of the self image of the grating. These perturbations are visualized as speckles on a detector and exploited for particle concentration measurements. The potential of the sensor concept is presented on the example of a modular Talbot interferometer using a HeNe laser at 633 nm to measure particle mass concentrations between 1 mg/L and 250 mg/L of Arizona test dust. We present the results of our investigations concerning the generation of Talbot self images in the planar configuration using a diverging multimode VCSEL light source. Furthermore we discuss the design and demonstrate the fabrication of a planar optical test system containing the integrated passive optical elements necessary for forming an integrated Talbot interferometer. Light source and sensor are positioned on a separate chip.

We report the design and fabrication of a novel single cell electroporation biochip fabricated by the Proton Beam Writing technique (PBW), a new technique capable of direct-writing high-aspect-ratio nano and microstructures. The biochip features nickel micro-electrodes with straight-side walls between which individual cells are positioned. By applying electrical impulses across the electrodes, SYTOX® Green nucleic acid stain is incorporated into mouse neuroblastoma (N2a) cells. When the stain binds with DNA inside the cell nucleus, green fluorescence is observed upon excitation from a halogen lamp. Three parameters; electric field strength, pulse duration, and the number of pulses have been considered and optimized for the single cell electroporation. The results show that our biochip gives successfully electroporated cells . This single cell electroporation system represents a promising method for investigating the introduction of a wide variety of fluorophores, nanoparticles, quantum dots, DNAs and proteins into cells.

One of the important challenges for the deployment of the emerging breed of nanotechnology components is interfacing them with the external world, preferably accomplished with low-cost micro-optical devices. For the fabrication of this kind of micro-optical modules, we make use of deep proton writing (DPW) as a generic rapid prototyping technology. DPW consists of bombarding polymer samples with swift protons, which results after chemical processing steps in high quality micro-optical components. The strength of the DPW micro-machining technology is the ability to fabricate monolithic building blocks that include micro-optical and mechanical functionalities which can be precisely integrated into more complex photonic systems. In this paper we give an overview of the process steps of the technology and we present several examples of micro-optical and micro-mechanical components, fabricated through DPW, targeting applications in optical interconnections and in bio-photonics. These include: high-precision 2-D fiber connectors, out-of-plane coupling structures featuring high-quality 45° and curved micro-mirrors, arrays of high aspect ratio micro-pillars, and fluorescence and absorption detection bio-photonics modules. While DPW is clearly not a mass fabrication technique as such, one of its assets is that once the master component has been prototyped, a metal mould can be generated from the DPW master by applying electroplating. After removal of the plastic master, this metal mould can be used as a shim in a final microinjection moulding or hot embossing step. This way, the master component can be mass-produced at low cost in a wide variety of high-tech plastics.

The highest efficiency silicon solar cells are fabricated using defined texturing schemes by applying etching masks. However, for an industrial production of solar cells the usage of photolithographic processes to pattern these etching masks is too consumptive. Especially for multicrystalline silicon, there is a huge difference in the quality of the texture realized in high efficiency laboratory scale and maskless industrial scale fabrication. In this work we are describing the topography of a desired texture for solar cell front surfaces. We are investigating UV-nanoimprint lithography (UV-NIL) as a potential technology to substitute photolithography and so to enable the benefits resulting of a defined texture in industrially feasible processes. Besides the reduced process complexity, UV-NIL offers new possibilities in terms of structure shape and resolution of the generated etching mask. As mastering technology for the stamps we need in the UV-NIL, interference lithography is used. The UV-NIL process is conducted using flexible UV-transparent stamps to allow a full wafer process. The following texturisation process is realized via crystal orientation independent plasma etching to tap the full potential of the presented process chain especially for multicrystalline silicon. The textured surfaces are characerised optically using fourier spectroscopy.

The half-tone lithography using pixilated chromium masks in a projection stepper is an established technology in micro-optics fabrication. However, the projection lithography tool is comparably expensive and the achievable lateral resolution is typically limited. By using pixel diffraction effects, binary and continuous profile lithography with submicron resolution can be installed on a conventional mask aligner. To achieve this goal the control of both, the angular spectrum of the illumination and the mask features is essential. We used a novel micro-optics based illumination system referred as "MO Exposure Optics System" in a SUSS MicroTec MA6 mask aligner for the dedicated shaping of the angular illumination distribution. In combination with an adapted lithography mask the formation of a desired intensity distribution in the resist layer is possible. A general mathematic model describes the relation between the angular spectrum of the mask illumination, pixel size and pitch in the mask, proximity distance and propagated field, which also includes special cases like Talbot imaging. We show that a wide range of different micro-optical structures can be optimized by controlling the light diffraction in proximity lithography. Parameter settings were found for submicron binary pattern up to continuous profile structures with extensions up to several tens of microns. An additional interesting application of this approach is the combination of binary and continuous profiles in single elements, e.g. micro lenses with diffractive correction or AR structures. Experimental results achieved for blazed gratings with a period of 2 microns are presented.

Laser lithography on non-planar surfaces is a technology which has been investigated at the IOF for more than 5 years. A special lithography system was developed for this purpose, allowing to structure spherical substrates with radii of curvature of ≥ 10mm. Binary or gray scale exposures with a minimum feature size of about 1μm covering a field of view (FOV) of ±10° are possible in standard operation mode. We present two approaches which will overcome certain disadvantages of the writing strategy at the expense of an increase in minimum feature size. First, we propose an exposure strategy which allows for an extension of the FOV to up to ±20° with satisfying accuracy of the structures. The according data is decomposed into concentric circles and projected onto the sphere so the exposure is not perpendiculary to the surface any more. Here we make use of the ability of our laser lithography system to adapt to a wide range of possible substrate thicknesses. On substrates with a flat edge, even layer to layer alignment for the curved structures is possible with an accuracy of ≤ 2μm. Example structures as well as prospects and limitations of this exposure strategy are presented. Secondly, similar to planar lithography, the use of a mask to produce multiple copies of a master sample is possible. Evidently the spherical mask needs to have the opposite radius of curvature than the desired substrate, and additional problems arising from the curved geometry have to be taken into consideration. Despite a lowered contrast due to back reflections and a varying distance between mask and substrate exposure results of sufficient quality are achieved with the help of an adapted aperture.

Cost efficient and purpose build microsystems for technical applications become more and more relevant. In the field of optical devices we developed an adaptive modular micro-optical system based on a Mach-Zehnder Delay Interferometer to show the feasibility to fabricate active optical microsystems adaptive to different measurement and data communication network applications. To realize such an adaptive modular micro-optical system with an active tuning device, a construction kit was designed and realized to combine different types of signal routing and system tuning, for example by choosing an optical or electronical signal output and different microactuators suitable for several applications, with special designed micro-optical benches (MOB) including the respective optical structures or hybrid integrated components. It is based on automated passive alignment of the optical components and has to be designed by using well defined interfaces. Different types of this modular system have been set-up and the application as a Fourier transformed wavemeter are shown as an example.

In this contribution we are focusing on two challenges concerning the development of new spectrometer concepts. First, we present different concepts to adjust or even to increase the detection efficiency of spectrometer modules over a broad spectral range. The discussion involves a spectral recycling loop, a reflective multilayer approach for efficiency achromatization and a concept based on spectral pre-selection. The second focus of this contribution concerns the miniaturization of spectrometer setups. We present a highly compact imaging miniature spectrometer module for applications that allow a very limited installation volume. The miniature spectrometer has an optical volume of just 11 x 6 x 5 mm³. The implementation of the spectroscopic "multi-order principle", which exploits successive diffraction orders, means that the central stress field between high spectral resolution and a large bandwidth can be dissolved. The manufacturing process of the spectrometer includes the mastering of the concave grating by interference lithography, the tooling and the replication process by injection molding.

The potential of fibre-optic connectivity based on micro-optical components for deployment at particular nodes of telecom access networks will be addressed. Low-cost micro-optic components which can be manufactured by high volume replication techniques can provide new functionalities or lead to optical performance improvements of permanent or demateable fibre connections. Some of the most interesting applications involving refractive micro lenses and new fibre alignment structures will be highlighted. Numerical simulations will be presented showing that expanded beam connectors are more robust to pollution than physical contact ferrule-based connectors. The advantages and drawbacks of expanded beam fibre coupling versus physical contact connectivity based on existing and micro-optical structures are discussed.

The Anteryon WaferOptics® Technology platform contains imaging optics designs, materials, metrologies and combined with wafer level based Semicon & MEMS production methods. WaferOptics® first required complete new system engineering. This system closes the loop between application requirement specifications, Anteryon product specification, Monte Carlo Analysis, process windows, process controls and supply reject criteria. Regarding the Anteryon product Integrated Lens Stack (ILS), new design rules, test methods and control systems were assessed, implemented, validated and customer released for mass production. This includes novel reflowable materials, mastering process, replication, bonding, dicing, assembly, metrology, reliability programs and quality assurance systems. Many of Design of Experiments were performed to assess correlations between optical performance parameters and machine settings of all process steps. Lens metrologies such as FFL, BFL, and MTF were adapted for wafer level production and wafer mapping was introduced for yield management. Test methods for screening and validating suitable optical materials were designed. Critical failure modes such as delamination and popcorning were assessed and modeled with FEM. Anteryon successfully managed to integrate the different technologies starting from single prototypes to high yield mass volume production These parallel efforts resulted in a steep yield increase from 30% to over 90% in a 8 months period.

In this contribution, we show that micro-optical elements are well suited to exploit the potential of organic light-emitting diode (OLED) based light sources. They may not only increase the OLED efficiency significantly but also enable for tailoring the common Lambertian-like emission pattern of OLEDs in order to reach desired light distributions corresponding to application demands. An OLED beam-shaping scheme is demonstrated utilizing thin micro-optical arrays where each channel consists of a half-ball lens and an adapted reflective/absorptive aperture. The combination of (a) light recycling, (b) distorted and arrayed imaging of the apertures, and (c) potential substrate-mode-outcoupling allows for efficient tailoring the light emission pattern of large area OLEDs. By means of such a beam-shaping concept, several different illumination patterns (e.g. circular, triangular beams or even more complex light distributions like letters) with various divergence angles below ±40° are demonstrated. Furthermore, a reduction of the divergence angle down to about ±10° accompanied by a stray light level minimization to <1% at larger angles is presented. In either case, intensity enhancements by a factor of >2 can be realized while the thickness of the optics remains below 2 mm.

State-of-the-art high brightness LEDs offer optical powers of about one watt and span a wide wavelength range - clearly outperforming usual single mode laser diodes. Thus, LEDs excel in applications where beam quality - the main advantage of lasers - is not the decisive criteria and/or speckle are critical. For a LED illuminated spot array generator a pupil splitting design approach with a lens-array is presented. Contrary to usual laser diode spot array generators with diffractive beamsplitters this design enables individually colored spots, suppresses unwanted speckle and increases beam quality with increasing spot number. Design rules and scaling laws are established, then the resulting system is analyzed with respect to useful transmission, beam quality and chromatic aberrations. We realized a 21x21 spot array generator with 40°x40° FOV using a simple plano-convex lens as projection optics. A chirped lens array with varying focal widths and pre-distorted lenslet positions corrects field curvature and distortion of the projection optics. Additional buried apertures and color filters suppress unwanted straylight and enable individually colored spots, respectively. The lens array is fabricated by replication of reflow master structures into polymer on glass.

Biaxial scanning single MEMS-mirrors are a promising approach to build strongly miniaturized laser projectors. This technology enables projection engines with a total height of about 5 mm and integration into slim mobile devices. Further advantages are high overall wall-plug efficiency and high display resolution. Important parameters which determine the optical performance of a laser projection device will be discussed. We studied the influence of mirror flatness errors, occurring during mirror motion, on the point spread function (PSF) and compare the results with optical and mechanical simulations. Based on the analysis of optical design limitations we explain capabilities to optimise the optical performance of such projection devices. Speckle pattern in the projected image are a problem that degrades the picture quality when using laser illumination sources. While speckle suppression is successfully integrated in laser illuminated imagers (like DMD or LCoS), it is still a serious problem for scanning beam applications. We present speckle reduction techniques for a miniaturized projection system and evaluate consequences on the optical performance. We developed a RGB-laser projection module with a total size of 60 × 36 × 10 mm³. It enables VGA resolution with luminous flux of about 10 lumens. All three lasers are coupled into separate multimode fibres. The light that leaves the three fibres is jointly collimated with an achromatic lens and combined with a dispersion prism to illuminate the MEMS-mirror.

Common projection optics use a single aperture approach to create a magnified image on a screen. The transmitted flux of such systems always scales with their system dimensions thus preventing the realization of ultra compact devices along with a high lumen output. We introduce a new multi-channel approach that breaks this rule and enables the realization of ultra slim, laterally extended projection devices with high flux and integrated homogenization. Array projection optics consists of a regular two-dimensional arrangement of projective microlenses superposing their images on the screen. First we derive the scaling laws of such a multi-channel projector in contrast to common single aperture optics and analyze the system parameters of a single projection channel by Seidel aberration theory. Based on the application of these results to a variable array size the array projection optics are specified. The technological realization of a sample system with still image projection is shown and characterized with respect to modulation transfer and flux.

Refractive X-ray lenses can be used effectively, to focus or collimate X-rays with photon energies clearly above 10 keV. On the one hand parabolic Compound Refractive Lenses (CRLs) are suitable as imaging optics in high resolution X-ray microscopy. The most recent developments are nanofocusing refractive X-ray lenses (NFLs). These show focal spot sizes of less below 100 nm. On the other hand refractive X-ray lenses can provide a high photon flux when used as large aperture condenser optics. Two types of refractive condenser optics made out of structures with triangular profile have been developed at the Institute for Microstructure Technology (IMT) at the Karlsruhe Institute of Technology (KIT) and have been tested at synchrotron sources in recent years. One type of special interest is the Rolled X-ray Prism Lens (RXPL). These lenses are made of a rolled polymer foil structured with micro grooves with triangular profile. The combination of such condenser optics and NFLs provides a basis for future hard X-ray microscopes.

As both data storage interconnect speeds increase and form factors in hard disk drive technologies continue to shrink, the density of printed channels on the storage array midplane goes up. The dominant interconnect protocol on storage array midplanes is expected to increase to 12 Gb/s by 2012 thereby exacerbating the performance bottleneck in future digital data storage systems. The design challenges inherent to modern data storage systems are discussed and an embedded optical infrastructure proposed to mitigate this bottleneck. The proposed solution is based on the deployment of an electro-optical printed circuit board and active interconnect technology. The connection architecture adopted would allow for electronic line cards with active optical edge connectors to be plugged into and unplugged from a passive electro-optical midplane with embedded polymeric waveguides. A demonstration platform has been developed to assess the viability of embedded electro-optical midplane technology in dense data storage systems and successfully demonstrated at 10.3 Gb/s. Active connectors incorporate optical transceiver interfaces operating at 850 nm and are connected in an in-plane coupling configuration to the embedded waveguides in the midplane. In addition a novel method of passively aligning and assembling passive optical devices to embedded polymer waveguide arrays has also been demonstrated.

The increased demand of broadband communication services like High Definition Television, Video On Demand, Triple Play, fuels the technologies to enhance the bandwidth of individual users towards service providers and hence the increase of aggregate bandwidths on terrestial networks. Optical solutions clearly leverage the bandwidth appetite easily whereas electrical interconnection schemes require an ever-increasing effort to counteract signal distortions at higher bitrates. Dense wavelength division multiplexing and all-optical signal regeneration and switching solve the bandwidth demands of network trunks. Fiber-to-the-home, and fiber-to-the-desk are trends towards providing individual users with greatly increased bandwidth. Operators in the satellite telecommunication sector face similar challenges fuelled by the same demands as for their terrestial counterparts. Moreover, the limited number of orbital positions for new satellites set the trend for an increase in payload datacommunication capacity using an ever-increasing number of complex multi-beam active antennas and a larger aggregate bandwidth. Only satellites with very large capacity, high computational density and flexible, transparent fully digital payload solutions achieve affordable communication prices. To keep pace with the bandwidth and flexibility requirements, designers have to come up with systems requiring a total digital througput of a few Tb/s resulting in a high power consuming satellite payload. An estimated 90 % of the total power consumption per chip is used for the off-chip communication lines. We have undertaken a study to assess the viability of optical datacommunication solutions to alleviate the demands regarding power consumption and aggregate bandwidth imposed on future satellite communication payloads. The review on optical interconnects given here is especially focussed on the demands of the satellite communication business and the particular environment in which the optics have to perform their functionality: space.

To realize a high density matrix of pressure sensors, mainly electrical approaches are reported. The proposed highdensity optical pressure sensor is based on a matrix of 2 stacked layers of crossing multimode waveguides. When pressure is applied on a crossing point, the distance between the waveguides from the upper and lower layer will decrease and power is transmitted between these waveguides. The sensor consists of polymer waveguides embedded in polydimethylsiloxane (PDMS) which is a very flexible material. Therefore, it is ideally suited to be applied on irregular or moving surfaces especially for applications which require covering small areas with high density pressure sensors.

This paper presents the optical and mechanical characterization of fully embedded optical links. The flexible optical links consist of ultra thin opto-electronic transceivers, multimode polymer optical waveguides, optical coupling structures and galvanic interconnections, all embedded inside a thin (145 μm) flexible foil. The embedded GaAs transceivers (VCSELs and Photodiodes) are first mechanically thinned down to 20 μm thickness, enabling the unobtrusive embedding inside the foil and allowing the chips to be bent with the foil due to their very low thickness. The embedded links are tested for their flexible behavior by means of several measurements: the optical bending losses of the flexible waveguides, the minimum bending radius before link failure and the bending endurance. The emitted optical modes of the ultra thin VCSEL's were characterized and compared before and after thinning and before and after embedding of the VCSEL's to determine the effect of these actions on the behavior of the VCSEL power and modes. The optical power budget of the complete optical VCSEL-to-Photodiode VCSEL is investigated by simulations and measurements of the different optical loss contributors. Also crosstalk behavior between two neighboring waveguides and links is measured. A proof of principle demonstrator of an embedded optical link on a rigid substrate using standard 50 Ohm test equipment and a basic galvanic lay-out shows a clear open eye diagram at a speed of 1.2 Gb/s. Reliability of the flexible optical link foil was demonstrated with temperature (-40 to 125 degrees Celsius) and humidity (85 rh/85 °C for 1000 hours) fastened aging cycling with good results.

One of the most important challenges in multiple-fiber connectors is to achieve accurate fiber positioning, i.e. to ensure that the fiber end facets coincide with the front facet of the connector plate. Therefore, it is crucial to increase the accuracy of the assembly process of fiber connectors. We present the population of a plastic multi-fiber connector designed for optical interconnect applications with silica fiber, with a good uniformity of fiber protrusion across the array of ±2.5-μm. To this end, an interferometric setup for in situ monitoring of fiber tip positions during the insertion phase was developed. It ensures an accurate fiber tip position at the fiber connector's front facet and across the fiber array in cases where post-insertion polishing is not possible. Furhermore, our setup can provide us with insight into the influence of the curing process (e.g. shrinkage) on the tip position during the fiber fixation step and allows us to assess the fiber facet quality. We compare the fiber tip position measured in situ using our setup with the position measured off-line using a commercial white light interferometer, showing a deviation smaller than 5%.

When a new technology is integrated into industry commodity products and consumer electronic devices, and sold worldwide in retail stores, it is usually understood that this technology has then entered the realm of mainstream technology and therefore mainstream industry. Such a leap however does not come cheap, as it has a double edge sword effect: first it becomes democratized and thus massively developed by numerous companies for various applications, but also it becomes a commodity, and thus gets under tremendous pressure to cut down its production and integration costs while not sacrificing to performance. We will show, based on numerous examples extracted from recent industry history, that the field of Diffractive Optics is about to undergo such a major transformation. Such a move has many impacts on all facets of digital diffractive optics technology, from the optical design houses to the micro-optics foundries (for both mastering and volume replication), to the final product integrators or contract manufacturers. The main causes of such a transformation are, as they have been for many other technologies in industry, successive technological bubbles which have carried and lifted up diffractive optics technology within the last decades. These various technological bubbles have been triggered either by real industry needs or by virtual investment hype. Both of these causes will be discussed in the paper. The adjective ""digital"" in "digital diffractive optics" does not refer only, as it is done in digital electronics, to the digital functionality of the element (digital signal processing), but rather to the digital way they are designed (by a digital computer) and fabricated (as wafer level optics using digital masking techniques). However, we can still trace a very strong similarity between the emergence of micro-electronics from analog electronics half a century ago, and the emergence of digital optics from conventional optics today.

Different earth-observation and scientific space missions have the need for special spectrometer gratings. As satellite instruments typically operate close to the technologically accessible limits also the realization of the respective gratings is extremely demanding. Critical parameters are the diffraction efficiency and its polarization dependency, the wavefront error introduced by the grating, stray-light performance, and usability in a space environment. We show that it is necessary to include technological considerations into the design and specification of the grating in order to achieve the optimal performance of the complete optical system. We demonstrate this approach by two examples. The first one is the design and fabrication of the grating for the Radial-Velocity-Spectrometer of the GAIA-mission of the ESA using a novel approach based on an effective medium sub-structure within one grating period. The second example is a high dispersion NIR-spectrometer grating for an earth observation mission. Such gratings are typically realized as immersed structures in order to maximize the dispersion. We show that the same optical performance can be achieved with gratings operating in the resonance domain which can be realized by electron-beam lithography as well.

The design and the fabrication of a multilevel blazed grating in resonance domain for first order high efficiency applications are presented. The design shows that a 3 phase level grating is sufficient to achieve efficiency of 90% in the minus first diffraction order. The standard technology for the fabrication of multilevel grating consists in multistep electron beam lithography and reactive ion beam etching of the grating profile into the fused silica substrate. Typical fabrication errors of this technology approach, e.g. misalignment, reduce the theoretical reachable efficiency of the grating. Two new technological approaches were investigated to avoid these typical fabrication errors and to improve the multi level fabrication process. The designed grating has been fabricated by three different technological solutions and the geometrical characterization as well as the diffraction performance are presented and discussed.

A new type of achromatic phase mask is presented which creates an interferogram of single spatial frequency regardless of the ratio between the interferogram period and the exposure wavelength. The functional demonstration of this monolithic phase mask was made in the case of a long grating of period as large as 2 μm by mean of an exposure beam at 442 nm wavelength, i.e., more than four times smaller. The monolithic element performs one first splitting function exerted by a central transmission grating of period Λ1 which diffracts the incoming beam in two diffracted beams in the substrate which are then reflected to the backside of the substrate. The element performs a second diffractive function by means of two identical side-grating of period Λ2 placed at either side of the first grating. This function is the redirection of the two said beams under the monolith substrate at an angle which creates an interferogram of the desired period.

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

We demonstrate upconversion lasing and fluorescence from active microspheres fabricated from a novel fluorozirconate, Er³⁺-doped glass, ZBNA, when pumped around 978 nm through a tapered optical fibre. An ultralow, green lasing threshold of ~3 μW for 550 nm emissions is measured. This is one order of magnitude lower than that previously obtained for ZBLAN microspheres. Optical bistability effects observed within the microspheres indicate that this material is suitable for low-frequency, all-optical switching. The bistable mechanism is discussed and attributed to shifts of the resonances due to thermal expansion of the sphere, where the heat is generated by phonon transitions excited after optical pumping around 978 nm. We also report multiple bistability loops within the microspheres. In a separate experiment, the latching behaviour of the microspheres is illustrated.

The advent of Plastic Optical Fibre (POF) opened perspectives for numerous applications in the field of datacommunications. POF is increasingly popular in the automotive industry as a robust, lightweight, electromagnetic interference free, easy and cheap to install alternative to electrical wiring for high-speed entertainment, navigation and data acquisition systems in cars. The main challenge for the introduction of datacommunication systems based on POF is imposed by the working conditions of automotive applications: systems should remain fully functional in a temperature range from -40 °C to +115 °C . Furthermore, standardisation and mechanical design considerations put a number of other boundary conditions. We designed a misalignment-tolerant optical coupling system according to the Media Oriented Systems Transport standard (MOST) to convey the divergent beam from a Resonant Cavity Light Emitting Diode (RCLED) into a Step-Index (SI) multimode POF mounted in a detachable ferrule. In this contribution we describe the methodology to synthesize the dimensions and tolerances on the optical components in the coupling system. A Monte Carlo optimisation algorithm on the full three-dimensional (3D) description of the complete RCLED package and detachable POF ferrule was used to allow a realistic modelling of all misalignments that could occur in the production chain. We select the best suited system according to manufacturing and assembly capabilities as well as its suitability for automotive applications.

Optical interconnections have gained interest over the last years, and several approaches have been presented for the integration of optics to the printed circuit board (PCB)-level. The use of a polymer optical waveguide layer appears to be the prevailing solution to route optical signals on the PCB. The most difficult issue is the efficient out-of-plane coupling of light between surface-normal optoelectronic devices (lasers and photodetectors) and PCB-integrated waveguides. The most common approach consists of using 45° reflecting micro-mirrors. The micro-mirror performance significantly affects the total insertion loss of the optical interconnect system, and hence has a crucial role on the system's bit error rate (BER) characteristics. Several technologies have been proposed for the fabrication of 45° reflector micro-mirrors directly into waveguides. Alternatively, it is possible to make use of discrete coupling components which have to be inserted into cavities formed in the PCB-integrated waveguides. In this paper, we present a hybrid approach where we try to combine the advantages of integrated and discrete coupling mirrors, i.e. low coupling loss and maintenance of the planararity of the top surface of the optical layer, allowing the lamination of additional layers or the mounting of optoelectronic devices. The micro-mirror inserts are designed through non-sequential ray tracing simulations, including a tolerance analysis, and subsequently prototyped with Deep Proton Writing (DPW). The DPW prototypes are compatible with mass fabrication at low cost in a wide variety of high-tech plastics. The DPW micro-mirror insert is metallized and inserted in a laser ablated cavity in the optical layer and in a next step covered with cladding material. Surface roughness measurements confirm the excellent quality of the mirror facet. An average mirror loss of 0.35-dB was measured in a receiver scheme, which is the most stringent configuration. Finally, the configuration is robust, since the mirror is embedded and thus protected from environmental contamination, like dust or moisture adsorption, which makes them interesting candidates for out-of-plane coupling in high-end boards.

In this paper, we investigate a novel fast and reliable method to check the bonding quality of silicon wafers. It is based on illuminating the wafers with a high frequency waves (110 - 170 GHz) using quasi-optical technique. The reflected energy is used to evaluate the bonding strength. The reported experimental study is compared with the Infrared images.

In the recent years fundamental research involving the nanodimensional materials has received enormous momentum for observing and understanding new types of plasmonic materials and their physical phenomena occurring in the nanoscale. Mechanical and optical properties of these polymer based nanocomposite structures depend not only on type, dimensions and concentration of filler material, but also on a kind of polymer matrix used. By proper selection of polymer matrix and nanofillers, it is possible to engineer nanocomposite materials with certain favorable properties. One of the most striking features of nanocomposite materials is that they can expose unique optical properties that are not intrinsic to natural materials. In these researches, nanocomposite structures were formed using polymer (PMMA) as a matrix, and silver nanoparticles as fillers. By hot embossing procedure a diffraction grating was imprinted on formed layers. The effect of UV exposure time on nanocomposite structures morphology, optical (diffraction effectiveness, absorbance) and mechanical properties was investigated. Results were confirmed by UV-VIS spectrometer, Laser Diffractometer, PMT- 3 and AFM. Investigations proposed new nanocomposite structures as plasmonic materials with improved optical and mechanical properties, which may be applied for a number of technological applications: micro-electro-mechanical devices, optical devices, various plasmonic sensors, or even in DNA nanotechnology.

Fluorescent droplet cavities were created in elastomer by using an ink-jet method. A solution for creating droplets was composed of fluorescent rhodamine, alcohol, and surfactant. Polysiloxane was used as a matrix, since its elasticity allowed droplet deformation that caused resonance-wavelength shift. The injected dye solution self-formed a sphere in the raw liquid of polysiloxane due to surface tension. The polysiloxane matrix solidified in 8 h after adding a curing agent. The droplet exhibited whispering-gallery-mode emission when it was excited by a frequency-doubled Nd:YAG laser pulse. The resonance peaks shifted to either short or long wavelengths as the droplet deformed by pressing the elastomer.

Embossed holographic tags for security and anti-counterfeiting applications are being used by industry since many years. However, such elements are not very effective since the detector is usually the human eye, and provides therefore around 80% effective counterfeiting protection of the tag. We present a novel holographic anticounterfeiting technology which provides 99.999% protection against tag counterfeiting. Horus Technologies develops such holographic tags, which include several layers of increasingly secure optical features, from standard visual holographic patterns and OVIDs (Optical Variable Imaging Devices), to micro-holographic text, down to covert features such as encrypted high resolution holographic 1d, 2d and 3d bar codes. We also demonstrate the potential of providing anti-tamper functionality on the same tag, for packaging security (especially for medical packaging). Finally, we demonstrate that more than 1Mb/square mm of digital data can be stored and encrypted on these same tags. A specific low cost laser based reader is developed to read the various security feature of such hybrid universal holographic tags. We also present a way to change and update the encrypted data in the tag in a similar way to RFID tags. Finally, we show a cost effective technique to replicate these structures in volume by roll-to-toll embossing, and even direct by glass molding within the package itself (bottle, vial, etc,..).

We present here two approaches for the fabrication of 2D and 3D optical structures. The first one is a step-by-step fabrication process of 3D structures using thin relief gratings (stacks of thin 1D or 2D gratings). Azobenzene containing materials for the surface relief inscription have been used in the step-by-step procedure, where after holographic inscription of desired relief structure and coverage with spacer layer another correlated relief structure has been written in the next active layer etc. The method provides full flexibility of the structure type and parameters including different gratings in different layers (hierarchical structures). A technique to produce hexagonal relief gratings of enlarged diameter which can be used for layer-by-layer photonic structures is developed. The second approach is a multi-beam holographic recording using special phase masks. Such mask consists of three phase gratings arranged in plane equilateral triangle geometry with gratings vectors at 120° to each other. A simple method of fabrication of well-adjusted mask with rather high diffraction efficiency is developed. Hexagonal 2D surface relief and 3D volume phase structures were fabricated by a single laser beam exposure using UV or visible wavelengths (depending on the material) through the mask. Azobenzene containing materials and photopolymers, including new specially designed one, were used as holographic materials.

The article describes application of Level Set method for two different microfabrication processes. First is shape evolution of during reflow of the glass structure. Investigated problem were approximated by viscous flow of material thus kinetics of the process were known from physical model. Second problem is isotropic wet etching of silicon. Which is much more complicated because dynamics of the shape evolution is strongly coupled with time and geometry shapes history. In etching simulations Level Set method is coupled with Finite Element Method (FEM) that is used for calculation of etching acid concentration that determine geometry evolution of the structure. The problem arising from working with FEM with time varying boundaries was solved with the use of the dynamic mesh technique employing the Level Set formalism of higher dimensional function for geometry description. Isotropic etching was investigated in context of mico-lenses fabrication. Model was compared with experimental data obtained in etching of the silicon moulds used for micro-lenses fabrication.

The paper deals with the preparation and characterization of whispering-gallery-mode (WGM) microresonators. Three types of materials were used for the preparation of these microresonators, namely silica optical fibers, polydimethylsiloxane polymer and UV-acrylate polymer. In the case of the silica fibers microspheres were prepared by heating the fiber tip with a miniburner or CO₂ laser. Polymer microresonators were applied onto tips of fiber substrates when they were dipped into polymer and immediately cured. Microresonators with a diameter ranging from 70 to 1000 μm were prepared. Transmission properties of the prepared microresonators were investigated in experiments where a microresonator was excited by a red laser at 660 nm by using evanescent field of a coupling element, namely a glass or silica fiber prism. The output power from the coupling element was detected. Temporal changes of the output power caused by heating the microresonators were also measured and explained in terms of the microresonator quality factor.

In this work, we demonstrate the existence of abnormal pulse propagation regimes in linear and passive multiple-beam interferometers, where the group velocity can be tuned from subluminal to superluminal values by simply changing the length of one of the interferometer's arms. Experiments are performed in the radiofrequency range by using coaxial transmission lines. The interferometers group delay is characterized both in the frequency and in the time domain. Group velocities of 2c and tunnelling with negative group velocity of -0.11c were measured for electromagnetic wave packets of 2 μs width travelling through a Mach-Zehnder interferometer. In a 4-beam interferometer, the group velocity of a 5 μs wide pulse was reduced to only 0.3c (compared to the usual value of 0.67c). The system is scalable to other frequency ranges and its implementation for narrowband optical pulses could be feasible by means of micromachining technologies. A scaling approach for advancing/delaying optical pulses at 1.55 μm is discussed. These systems are proposed as an alternative for controlling the group velocity without the need of using photonic crystals or periodically microstructuring, doping or using non-linear media.

In this work we present the fabrication and characterization of high-Q microresonators made of low loss, thermoplastic polymer poly(methyl methacrylate) (PMMA), which are directly processed on a silicon substrate. Using this polymer-on-silicon material in combination with a thermal reflow step enables cavities of conical shape and ultra smooth surface, dramatically reducing the optical losses caused by surface scatting of the whispering-gallery-modes (WGMs). The cavity Q factor is above two million in the 1300 nm wavelength range and can theoretically reach values up to ten million in the visible. Finite element simulations show the existence of a variety of higher order radial and axial WGMs explaining the complexity of the transmission spectra measured using a tunable diode laser coupled to a tapered optical fiber waveguide.

Active control of VCSELs beam properties is a key issue to improve their integration in microsystems. We have designed a micro-optical system that allows for a dynamic displacement of the VCSEL beam. It consists of a polymer microlens associated to a SU-8 membrane vertically moved by means of a thermal actuator. This approach is suitable with laser sources arrays. We present results on optical design demonstrating that a small deflection of the membrane (2μm) could lead to a large displacement of the beam waist vertical position (in the millimetric range). Thermomechanical modelling is performed to evaluate the maximum membrane displacement achievable with this system. Finally, first feasibility results are presented.

We present the application of glass microlenses for the fabrication of inspection systems based on interferometric measurements. The microlenses are molded from wet etched silicon by using microfabrication techniques. The concerned system requires lenses to be used in a Mirau interferometer configuration. The principle of the system is presented, as well as different choices of lenses to be integrated. The use of glass microlenses monolithically molded on a substrate is proven as the proper technology to be used in the system.

The laser performances of silica microspheres functionalized by neodymium doped gadolinium oxide nanocrystals are investigated. First, we have developed a new method to identify and selectively excite small mode volume WGMs using a tapered fiber coupler. The electromagnetic-field distribution ofWGMs is mapped by the excitation efficiency, providing a measurement of the near field intensity. Moreover a method to characterize the ultra-low threshold microlaser is presented here, which relies on the use of the thermal bistability effect: the thermal drift of the resonance line which slows down the power scanning help us to detect the onset of laser effect on the emitted light. Finally, a single mode lasing at 1088.2 nm with threshold as low as 65 nW is achieved, for a quality factor at lasing wavelength of 1.4 × 10⁸.

We demonstrate that light can be used to create microchannels in ice. We make use of free space and fiber coupled infrared laser light to produce microchannels with diameters down to 100 microns in diameter. We demonstrate that the channels can be created in a timescale of seconds and that by controlling the input power that they can be stabilized over a timescale of several minutes using powers as low as 30mW. We compare the fiber coupled geometry, using both single mode and multimode fiber and free space coupling and show that fiber coupling produces optimal results. We demonstrate that liquid samples can be inserted into the channels and particle movement is observed using a combination of optical and thermally induced forces. We also present data looking at droplet freezing within the microchannels. We present preliminary results looking at dual beam coupling into such optofluidic channels and examine prospects for using such channels as rapid microfluidic prototypes. We further discuss the possibility of using optically shaped ice channels as a means to study aerosol nucleation processes and the ability of ice to act as a template for microfluidic devices.

We modify the former dynamical model of drying process of polymer solution coated on a flat substrate to deal with drying process of solution having two kinds of solvents. As a result, we see that there is no essential difference between solute's distribution after drying in case of having two kinds of solvents and that in case of having only one kind of solvent and when there are over two kinds of solvents, solute's distribution after drying obeys the mean value of over two kinds of solvents' parameters, that is, it resembles one simulated numerically based on the mean value in case of having only one kind of solvent.

We propose mode division multiplex communication technique that can split a specific spatial mode in light from a spatial mode multiplexed in an optical fiber by fusion of a phase conjugation technique with spatial filtering processing by multiplexed volume holograms and random diffusers. In mode division multiplexing, the optical signal outgoing from the multimode optical fiber is in a condition that optical information of plural spatial modes is overlapped, therefore it is difficult to de-multiplex electrically after light detection. Our technique enables to split it into each mode all optically and to compensate temporal modal shift dynamically. Mode de-multiplexing is realized by multiplexed holographic arithmetic device and phase matching of a wave surface for the spatial mode orthogonal to time. Therefore, if we use indices in conventional electronic processing, a very high-speed operation equivalent to that of 10-100PFLOPS can be realized without causing any delay in light information to be transmitted. Moreover, it can realize constructions of a system that can dynamically respond to temporal mode variations and distortions with fiber transmissions by using a photorefractive medium. Separating of around 60-70% was achieved in an experiment of separating three multiplexed spatial modes by controlling a volume type dynamic reconfigurable device based on LiNbO₃. It was clarified that the separation performance improved by an appropriate random phase mask in the numerical analysis.

Optical interconnect technology is discussed as a way to more power efficient tele- and data-communication systems. That is well confirmed for long reach optical interconnects but can be gained also from inter and intra system optical interconnects. Besides component and system architecture issues it is assumed that advanced photonic packaging approaches cause power efficiency advantages at multi chip module level. Transparent thin glass substrates are used for high frequency electrical interconnects and integrated optical waveguides for chip to chip optical communication. A generic approach called "glassPack" is discussed and some relevant technologies are presented in more detail.

All-organic chips with integrated optical waveguides and microfluidic channels were built for fluorescence excitation of biological samples. These optofluidic systems were made out of poly (methyl methacrylate) (PMMA) with lithographically generated or micro machined fluidic structures. Integration of the waveguides was based on photodegradation of PMMA through deep ultraviolet (DUV) radiation. Two types of demonstrators were created in order to show the applicability of the integrated optical waveguides. In one set free space illumination via the waveguide and thus fluorescence excitation of biological samples located inside or flowing through a microfluidic channel could be shown. In another set fluorescence excitation via evanescent field coupling of biological samples located on top of an embedded optical waveguide was simulated and could be experimentally proven. As biological samples stained living animal cells (L929 mouse fibroblasts with DiD membrane staining), fluorophore labeled proteins (Cy3), or phospholipids (rhodamine) were used with the optofluidic micro systems. Emitted fluorescence was observed with a microscope. The experiments serve as a proof of concept for the layout of a cell based optofluidic microsensor built as a monolithic polymer device with potential use as a Lab-on-a-Chip system.

This study deals with a design, fabrication and characterization of compact optoelectronic oscillators (OEO). Resonator behaves as a sphere because energy is trapped in whispering-gallery-modes in the equatorial region. For this purpose, Fused-silica and MgF₂ are suitable, due to their mechanical characteristics and their low attenuation at 1.55 μm wavelength. In fact, 6-7 degrees Mohs hardness of these materials allows us to obtain a quite easy precision-processing. Our prototype owns a quality factor of approximately 3×10⁸, which is certainly limited by the available technology. Resonator is coupled to an optical fiber including a taper-waveguide-based on a nm-position resolution. Microwave carrier is generated by locking optical phase modulation to a free-spectral-range (FSR) resonator, which occurs in the X-band. Moreover, this carrier is detected by a standard low-noise InGaAs p-i-n telecom photodiode. Oscillator prototype is assembled on a 0.12 m² optical breadboard. In principle, this surface can be reduced to those of the oscillator main parts (resonator, laser, photodiode, amplifier and optical modulator). Oscillator phase noise measured by a dual-delay-line instrument, which has been developed in Besançon, corresponds to -90 dBrad²/Hz at 10 kHz off carrier. According to this result, oscillator suffers from severe noise-limitations due to several reasons: the thermal coefficient of the resonator, the low power that the resonator can accept, and the small volume of the energy-confinement region in the resonator (≈2×10¹⁴ m³) but our oscillator is packaged in a small volume, contrarily to classic OEO based on an optical fiber of a few km.

In this paper we discuss the design of a novel miniaturized image sensor based on the working principle of insect facet eyes. The main goals are to design an imaging system which captures a large field of view (FOV) and to find a good trade-off between image resolution and sensitivity. To capture a total FOV of 124°, we split up this FOV into 25 different zones. Each of these angular zones is imaged by an isolated optical channel on our image sensor. There is an overlap between the zones to cover the full FOV but the different zones are imaged on separated regions at the image sensor. Every optical channel in the designed component consists of two lenses that are tilted with respect to each other and the optical axis. Because of this tilt of the lenses, we are able to minimize field curvature and distortion in the obtained images at the detector, and have an angular resolution below 1°. The optical system was implemented and optimized in the ray-tracing program ASAP. The parameters (in one channel) that are optimized to obtain this large FOV with a good image resolution and sensitivity are the radius of curvature of the two lenses, their conical factor and their tilt in two directions with respect to the optical axis of the complete system. The lenses are each placed on a pedestal that connects the lens to a planar substrate. We also add absorbing tubes that connect the two lenses in one channel to eliminate stray-light between different optical channels. The obtained image quality of the design is analyzed using our simulation model. This is determined by different parameters as there are: modulation transfer function, distortion, sensitivity, angular resolution, energy distribution in each channel and channel overlap. The modulation transfer function shows us that maximum contrast in the image is reached up to 0.3LP/°, distortion is maximal 21% in one of the 25 different channels, the sensitivity is 0.3% and the resolution is better than 1°.

A new configuration of micro-spectrometer based on an infrared stationary Fourier transform (FTIR) interferometer has been developed at ONERA. Our device is based on a classic infrared focal plane array (FPA) of HgCdTe technology with a built-in two-wave wedge-like interferometer. This new architecture generates research works in several domains. Technological researches are conducted in collaboration with the CEA to optimize the manufacturing process and reduce the technological defects. In parallel, researches in optical design are conducted to implement the FTIR-FPA in a complete system. For this, theoretical work is needed to understand and describe the fringes formation inside the detection structure when illuminated by a wave which is not ideal, i.e. emitted by an extended source positioned at a finite distance from the detection plane. The results of this theoretical study are presented. These results are exploited to design a compact spectrometer with a very simple optical architecture. First experimental data are presented and discussed.

Optical interconnects replace electrical links increasingly at shorter distances. At printed circuit board (PCB) level highly multimodal polymer channel waveguides are the chosen approach to meet bandwidth-length and bandwidth-density requirements. One important challenge of board integrated waveguides is the coupling problem. The manufacturing process of PCBs leads to relatively high placement tolerances which cause poor optical coupling efficiency due to mechanical misalignment between separate components, e.g.: 1) Coupling between a VCSEL and the board integrated waveguides; 2) Coupling between waveguides in two separate boards. This paper deals with the deployment of tapered dielectric multimode waveguides for increasing the optical coupling robustness towards mechanical misalignments in these two coupling applications. A coupled mode approach for calculation of the mode coupling and power loss in a taper with decreasing width has been presented before [5]. In [6], the two above mentioned coupling applications for tapered dielectric waveguides have been dealt with, but only the coupling efficiency in case of longitudinal misalignment has been calculated. In this paper, results of advanced analysis of the two applications are presented. The coupling efficiency in case of transverse misalignment is simulated by a ray-optical approach. Furthermore the results of measurements of the coupling behaviour of board integrated tapered waveguides are presented. The results show that tapered multimodal dielectric waveguides have the capability to increase the coupling efficiency significantly if some conditions are fulfilled.

This paper reports on the functional and spectral characterization of a microspectrometer based on a CMOS detector array covered by an IC-Compatible Linear Variable Optical Filter (LVOF). The Fabry-Perot LVOF is composed of 15 dielectric layers with a tapered middle cavity layer, which has been fabricated in an IC-Compatible process using resist reflow. A pattern of trenches is made in a resist layer by lithography and followed by a reflow step result in a smooth tapered resist layer. The lithography mask with the required pattern is designed by a simple geometrical model and FEM simulation of reflow process. The topography of the tapered resist layer is transferred into silicon dioxide layer by an optimized RIE process. The IC-compatible fabrication technique of such a LVOF, makes fabrication directly on a CMOS or CCD detector possible and would allow for high volume production of chip-size micro-spectrometers. The LVOF is designed to cover the 580 nm to 720 spectral range. The dimensions of the fabricated LVOF are 5×5 mm². The LVOF is placed in front of detector chip of a commercial camera to enable characterization. An initial calibration is performed by projecting monochromatic light in the wavelength range of 580 nm to 720 nm on the LVOF and the camera. The wavelength of the monochromatic light is swept in 1 nm steps. The Illuminated stripe region on the camera detector moves as the wavelength is swept. Afterwards, a Neon lamp is used to validate the possibility of spectral measurement. The light from a Neon lamp is collimated and projected on the LVOF on the camera chip. After data acquisition a special algorithm is used to extract the spectrum of the Neon lamp.

We report on the fabrication of a one-dimensional micro-retroreflector array with a pitch of 100 micrometers. The array was fabricated by X-ray lithography and the LIGA process in a 1 mm thick PMMA layer and subsequently covered with Au. The area of the array is 1 mm x 10 mm. The high precision of the LIGA-based fabrication process allows one to use the element in spectrometers. Here, it is suggested to use it for the implementation of a transversal filter for femto-second pulses.

We propose a structured light micro-opto electromechanical system (MOEMS) projector specially designed to display successively a set of patterns in order to extract the 3-D shape of an object using a CCD cameras module and a small ARM-based computer for control, registration and numerical analysis. This method consists in a temporal codification using a modified Gray code combined with a classical phase shifting technique. Our approach is to combine the unambiguous and robust codification of the Gray code method with the high resolution of the phase shifting method to result in highly accurate 3D reconstructions. The proposed MOEMS is based on an array of vertical-cavity surface-emitting laser (VCSEL) combined with two planar static diffractive optical elements (DOEs) arrays. DOEs masters on quartz substrate have been fabricated using photolithography therefore replication in polycarbonate is possible at low cost. The first DOE array is designed to collimate the VCSEL light (Fresnel-type element) and the second one to project the codification patterns. DOEs have been designed and fabricated by surface etching to achieve a good diffraction efficiency using four phase levels. First we introduce the MEOMS principle and the features of the different components. We present the layout design of the DOEs and describe the issues related to the micro-fabrication process. An experimental study of the topography of the DOEs is presented and discussed. We then discuss fabrication aspects including the DOEs integration and packaging.

The rigorous vector-based simulation methods for subwavelength diffractive lenses are methods of growing importance. In this paper, we introduce a rigorous vector-based method to compute the electromagnetic propagation. It includes the Finite-Difference Time-Domain (FDTD) for the near field simulation, and the Radiation Spectrum Method (RSM) for the far field propagation. This approach is then proposed to design effective medium cylindrical diffractive lenses. This kind of component, made up of binary features that behave as an effective medium, can achieve an higher diffraction efficiency than conventional diffractive optical elements. The layout design of the component is realised thanks to the FDTD simulation by estimating the phase difference introduced by subwavelength binary gratings. Then, the whole modeling of the component, whose minimum feature size can be smaller than 100 nm, is done with the RSM algorithm. Because of their subwavelength, aperiodic, finite and high spatial frequencies characteristics, these devices conception methods prevent the use of scalar modeling or coupled wave theory. The proposed method overcomes these limitations. First, the principle of the rigorous vector-based method is introduced. Then, we present the design of the subwavelength structures by means of the FDTD method, followed by the design of the subwavelength element. Finally, the simulation method of the subwavelength lens by use of the FDTD method for the near field propagation and the RSM for the far field calculation is also presented. Finally, we discuss the comparison between a subwavelength lens and its multilevel counterpart.

In this paper we study the optical properties of GRIN lens arrays used in the writing heads of LED-based digital colour presses for 600 dpi printing. The goal of our study was to determine the most critical parameters for achieving a good image quality and to optimise the parameters of these arrays to improve the image quality. The writing head of a colour press consists of a row of LEDs and the light of these LEDs is focused by the GRIN lens array onto a photosensitive drum. The GRIN lens array is used as an imaging system with unit magnification. We started with optical raytracing simulations to determine the optimal working distance of commercial GRIN lens arrays and to evaluate their image quality. Furthermore, we carried out a tolerancing analysis of possible misalignments in the writing head and compared the results from our simulations with the results of an experimental tolerancing study. Finally we explored the possibilities for using the same GRIN lens arrays for 1200 dpi printing.

A new generation of micromirror arrays (MMAs) with torsional actuators is being developed within the European research project MEMI in order to extend the usable spectral range of diffractive MMAs from deep ultraviolet into the visible and near infrared. The MMAs have 256 x 256 pixels reaching deflections above 350 nm at a frame rate of 1 kHz, which enables an operation in the target wavelength range between 240 nm and 800 nm. Customized driver electronics facilitates computer controlled operation and simple integration of the MMA into various optical setups. Tests in the visible wavelength range demonstrate the functionality and the high application potential of first MMA test samples.

Direct patterning of Polydimethylsiloxane (PDMS) thin film is demonstrated. A procedure is implemented to induce PDMS self-patterning in one and two dimensional geometries based on surface-charge lithography by means of the photorefractive properties of iron doped Lithium Niobate (LN) crystal. Linear periodic and radial arrays of microchannels are fabricated by changing the wettability on the LN crystal surface. The substrate is x-cut Fe+ doped LN crystal, the covering substance is PDMS. Fabrication process is divided in three stages: PDMS spinning on the substrate, PDMS reshaping and PDMS curing. After spinning step the sample is inserted in an optical setup. We employ an Argon laser whose wavelength is 514nm. Light passes trough an amplitude grating that is imaged by a lens. The sample is positioned in the conjugate plane of the grating. Light impinging on the lower LN surface is spatially inhomogenous and excites the charge carriers inside the crystal. The space-charge field generate inside the material modulate the refractive index via electro-optic effect and cause lateral forces near the upper surface able to manipulate and trap liquids. PDMS moves on the crystal surface trapping itself and gathering up in stripes to form geometries with the same period of the phase grating written inside the crystal. While the light source generate the PDMS structure, a thermal treatment applied to the crystal, induces the cross-linking of the PDMS, leading to a stable and reliable PDMS pattern. We propose an alternative one step patterning process based on light driven self assembly.

Spherical whispering gallery mode (WGM) resonators can be used in a broad range of applications from bio-sensing to laser engineering. Beyond the interest for applied studies, such resonators are also of interest for more fundamental studies, e.g. cavity QED. A key requirement for many applications is the ability to tune the resonator to an energy transition of the atomic species (or material) under investigation. Heretofore, heating the cavity with an external heater, or deforming the cavity mechanically, have been the two main approaches used to tune the cavity size. We demonstrate thermo-optical methods of tuning the WGM resonance frequencies of doped glass microspheres over a very large dynamic range. Er:Yb phosphate glass (IOG2) microspheres are pumped at 978 nm via a tapered optical fibre. This causes internal heating of the microsphere and the temperature of the mode volume can reach temperatures higher than 800°C. With the heat concentrated in the optical mode volume, the resonance frequency has been tuned by ~700 GHz nonlinearly. Alternatively, we show that large linear tuning up to ~488 GHz is achievable if the microsphere is separately heated by coupling laser light into its support stem.

Numerous optical imaging techniques have been developed for clinical diagnostics; among these, optical coherence tomography (OCT) has proven to be of considerable utility due to its ability to non-destructively image below the surface of tissue. Endoscopic OCT systems will further extend the capabilities of this approach but require an additional means for scanning in two or three dimensions. We present an integrated optical microsystem which allows scanning of an optical beam in three dimensions (an area scan combined with dynamic focus) suitable for an endoscopic OCT probe. The system is defined by a tunable pneumatically-actuated micro-lens combined with an electrostatically-actuated two-axis micro-mirror, allowing functionality hitherto not achievable.