This PDF file contains the front matter associated with SPIE Proceedings Volume 6992, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

Micro-optical interferometer systems are requested for optical sensor application as well as for signal monitoring or signal (de)modulation in case of optical data networking. Using the opportunities of LIGA technology with its precision in manufacturing of polymeric microstructures with a high aspect ratio, e.g. for the exact alignment of commercially available optical elements or to realize the micro optical structures itself, offers the possibility to design and fabricate complex modular micro-optical systems. Due to this modular concept the MOEMS are usually composed of a micro-optical bench (MOB) and an external platform with a micro actuator. The combination to a subsystem can be realized by standard assembly technology. A first designed prototype using this advanced modular concept is a micro Mach-Zehnder interferometer based on free space propagation. It was developed to be applied in different fields of c-band applications at 1550 nm up to 40 Gbps.

FTTH networks require implementing a diplexer at each user termination. According to most of the standards, this diplexer detects a download signal beam at 1.49μm and emits an upload signal beam at 1.31μm on the same single mode fibre. Both signals exhibit datarate speed below 2.5Gbps. Today, most of the diplexers are obtained by actively aligning a set of individual optoelectronic components and micro-optics. However, new manufacturing solutions satisfying very low cost and mass production capability requirements of this market would help to speed the massive spreading of this technology. In this paper, we present an original packaging design to manufacture Diplexer Optical Sub-Assembly for FTTH application. A dual photodiode is stacked over a VCSEL and detects both the download signal beam at 1.49μm passing through the laser and one part of the upload signal beam at 1.31μm for monitoring. To satisfy this approach, an innovative VCSEL has been designed to have a very high transmission at 1.49μm. All these components are mounted on a very small circuit board on glass including also integrated circuits such as transimpedance amplifier. So, the device combines advanced optoelectronic components and highly integrated Multi-Chip-Module on glass approach using collective wafer-level assembling technologies. For the single mode fibre optical coupling, active and passive alignment solutions are considered.

To facilitate and speed up the deployment of fiber-to-the-home networks, high-efficiency, low-cost, field installable fiber connectors are one of the key components. We present a novel type of small-form-factor 180°-bend single mode fiber socket, allowing for 0.5-dB coupling loss between two side-by-side positioned fibers, making use of specially designed low bending loss hole-assisted fiber. The components are prototyped in a polymer using Deep Proton Writing and show all the potentialities for low-cost fabrication in different types of plastics.

"glassPack" will be introduced as a novel photonic packaging concept for a wide area of applications like high-speed electronic systems and sensors. The usage of thin glass foils with a thickness of some tens of microns as substrate and interconnection material will be discussed. Photonic packaging in such hybrid optoelectronic systems involves single packages, modules, and subsystems comprising at least one optoelectronic device, micro-optical element or optical interconnection. Thin glass is a commercially available and reliable material with high thermal resistance and excellent optical properties. Because glass is a well known material, many technologies like polishing, plating, etching and refractive index tuning are already known. In combination with newly developed integration technologies, a complete glass based package on wafer level can be realized. The main ideas of the "glassPack" concept are: selection of suitable glass foils as substrate material, realization of microsystem compatible structuring technologies like cutting, drilling and etching, integration of optical waveguides by ion-exchange for single- and multi-mode applications, implementation of optical interconnects between fibres and integrated waveguides by laser fusion, integration of electrical wires and feed throughs, assembly of electronic and optoelectronic components, and bonding of the thin glass foils to 3D-stacks. Furthermore, the integration of micro fluidic channels into a "glassPack" will be supported. A sensor module containing optical waveguides, fluidic channels, electrical wires and components like a laser, two photodiodes and two flip-chips will be presented to demonstrate the suitability of glass as a material for integrated microsystems.

Planar microoptical systems integration is a powerful approach for the fabrication of optical systems and has been demonstrated for a large variety of applications. The folded optical axis in combination with planar fabrication technologies enables highly integrated and rugged optical systems. In this geometry, however, specific care is necessary to avoid aberrations resulting from the oblique optical axis. A purely diffractive implementation of these systems generally leads to an efficiency of only a few percent. Combining classical refractive optics with diffractive correction elements increases the overall efficiency. However, the purely refractive implementation suffered from the lack of fabrication technologies for freeform microoptical elements. We present the results of the first fabrication of freeform refractive correction elements combined with standard off-the-shelf refractive microlenses to form a completely refractive planar integrated optical system using ultraprecision micromilling. Experiments confirm the increased optical performance of the systems by integrating two micromachined reflective correction elements. Both elements have a size of 2.4 x 2.4 mm² with a peak-to-valley surface profile depth of 2.6 μm. They are fabricated with an average roughness height < 40 nm and a surface tolerance < 400 nm.

Microstructured metallic moulding tools or mould inserts are needed for mass production of micro-optical components. These tools are used for hot embossing or injection moulding of micro components in plastic. Because of the extremely tight specifications like small sidewall roughness and high aspect ratios these tools are usually fabricated by lithographic procedures followed by electroforming. In this case the structural geometry is limited to Manhattan-like structures and only a limited number of technologies can be used to fabricate the master structures. Applicable techniques are e.g. X-ray lithography (LIGA technology) or Deep Proton Writing (DPW). However these processes are not suitable for low-cost mass production. They are limited by the exposure area and the design of the microstructures. To overcome these limitations a new process has been developed which allows the transfer of micro-optical structures fabricated by other technologies as well as assembled structures or structures with varying geometries into a moulding tool. The master structures, either plastic, glass, metal or a combination of these materials, serve as sacrificial parts. With electroforming technology, a negative copy of the microstructured master is built up in the metal subsequently used as a moulding tool. Low-cost mass production is possible with these moulding tools. We present the process chain in this paper and demonstrate its feasibility by producing reliable moulding tools from three challenging and different components. The possibility of mass fabrication of the components by replication was demonstrated.

Using our rapid prototyping technology called Deep Proton Writing (DPW), we have in recent years made a wide range of micro-optical components with a large depth (500-μm) for a variety of applications. One of these components is a pluggable out-of-plane coupler for printed circuit board-level optical interconnections. Whereas DPW is capable of rapidly fabricating high-quality master components, the technology is not suitable for low-cost mass fabrication. Therefore, we investigate the replication of out-of-plane coupling components using hot embossing, through the fabrication of a metal mould of the DPW master by applying electroplating. We compare these hot embossed replicas with components replicated using the elastomeric mould vacuum casting technology.

The concept of the fabrication process of glass microlenses integrated with silicon and polymer replicas is presented. These kinds of microlenses are formed using a silicon master which is wet etched in alkaline solutions (anisotropic etching) and/or in acid solutions (isotropic etching). The control of the times and the selection of the solutions, joined with the designs of the mask for conventional photolithography and the quality of the silicon wafers are the key for obtaining the desired shapes and sizes. The fabricated moulds are used to replicate microlenses in polymer by the standard well known replication technologies and also to fabricate glass microlenses integrated on a silicon frame.

The driving force behind combining the nanoimprinting and photolithography is to effectively utilize the advantages of both patterning techniques simultaneously. Conventional shadow-mask UV-lithography can be used to pattern micron-scale structures uniformly over large areas, whereas nanoimprinting enables patterning of nanoscale features, which can also be tilted or round-shaped. We present the work on direct patterning of micro-optical structures by combined nanoimprinting and lithography using modified mask aligner, hybrid mask mold and directly patternable, UV-curable materials. Patterning of structures is carried out in wafer-level fashion. Hybrid mask mold fabrication can be realized for example by modifying conventional shadow-mask using focused ion beam (FIB) milling, or by patterning a mold area on shadow-mask surface by nanoimprinting. One of the advantages of proposed fabrication method is that there is no need for reactive ion etching (RIE) process steps. We present also near-field holography (NFH) as a method of grating mold fabrication. Fabricated micro-optical structures include directly patterned waveguides with light coupling gratings, and also pyramid-shaped gratings which show antireflection properties in the mid-infrared spectral region.

Whereas microelectronic lithography is heading to the 32 nm node and discussing immersion and double-patterning strategies, there is much which can be done with the 45 nm node in microoptics for white light processing. For instance, one of the most demanding applications in terms of achievable period is the LCD lossless polarizer, which can transmit the TM polarization and reflect the TE polarization evenly all through the visible spectrum - provided that a 1D metal grid of 100 nm period can be fabricated. The manufacture of such polarizing panels cannot resort to the step & repeat cameras of microelectronics since the substrates are too large, too thin, too wavy and full of contaminants. There is therefore a need for specific fabrication techniques. It is one of these techniques that a subgroup of partners belonging to two of the Networks of Excellence of the European Community, NEMO and ePIXnet, have decided to explore together.

The addition of nanosized inorganic or organic dopants to polymers allows the modification of the polymers physical properties enabling the realization of functionalized polymers with new application fields e.g. in microoptics. Exemplarily electron rich organic dopants, solved in polymers, cause a pronounced increase of the refractive index. Polymer based reactive resins like PMMA, solved in MMA, or unsaturated polyester, solved in styrene, can be cured to thermoplastic polymers. The resin's low viscous flow behaviour enables an easy composite formation by solving the organic dopants in the liquid up to a dopant content of 50 wt%, followed by solidification to a thermoplastic. The addition of simple organic molecules like phenanthrene or benzochinoline allows a refractive index elevation at 633 nm from 1.56 up to 1.60 retaining the good transmission properties. In comparison the refractive index of PMMA can be increased from the initial value of 1.49 up to values around 1.58 (@633 nm). All composites show an almost linear correlation between dopant content and refractive index. Using these composites devices like 3dB-couplers or an electrooptical modulator applying injection molded or hot embossed substrates have been realized.

Iridescent colors created by sophisticated nanostructured materials are known from nature and attract a lot of attention nowadays. A closer look reveals that such colors are often produced by combination of structures at different lengths scales at the micrometer and nanometer level. While simulation and analysis of such structures can be done with rigorous methods fabrication is seldom attacked because if its complexity. We have chosen a particular design concept that uses Bragg reflectors as dispersive components and microoptical elements to steer the light. We focused on fabrication in organic materials, where compatibility of different process steps is an issue. Fabrication is done by spin-coating of thin films and soft replication of microoptical elements. The structures were entirely fabricated in polymer materials on glass substrates or polymer films that serve as substrates. Microoptical structures with dimensions ranging from 30 to 250 microns are embossed on Bragg reflectors having periods of 160 nm. Of main interest for us were the spectral reflection properties. Reflection properties were measured for white light in a goniometric setup and their behavior is discussed. To understand the basic features modeling is carried out by combining ray tracing and rigorous methods.

Diatoms are monocellular micro-algae provided with external valves, the frustules, made of amorphous hydrated silica. Frustules present patterns of regular arrays of holes, the areolae, characterized by sub-micrometric dimensions. In particular, frustules from centric diatoms are characterized by a radial disposition of areolae and exhibit several optical properties, such as photoluminescence variations in presence of organic vapors and photonic-crystal-like behaviour as long as propagation of electromagnetic field is concerned. We have studied the transmission of coherent light, at different wavelengths, through single frustules of Coscinodiscus Walesii diatoms, a centric species characterized by a diameter of about 150 μm. The frustules showed the ability to focalize the light in a spot of a few μm², the focal length depending on the wavelength of the incident radiation. This focusing effect takes place at the centre of the frustule, where no areolae are present and, as it is confirmed by numerical simulations, it is probably due to coherent superposition of unfocused wave fronts coming from the surrounding areolae. Diatoms-based micro-lenses could be used in the production of lensed optical fibers without modifying the glass core and, in general, they could be exploited with success in most of the optical micro-arrays.

There is an emerging demand for compact infrared instruments, imagers and/or spectrometers, integrated on ground or air vehicles for spatial and spectral data collection. To reach this goal, technological barriers have already been overcome, leading to the development of infrared focal plane arrays (IRFPAs) for high-performance applications (megapixel format, bispectral technology) but also for low-cost and high-volume manufacturing (technology of uncooled micro-bolometers). The next step is to reduce the optics and make it compatible with the successful IRFPAs fabrication technology. This paper presents MULTICAM, a small cryogenic infrared camera. This optical system is composed of multi-level arrays of microlenses integrated in the cryostat and inspired from invertebrate compound eyes. First experimental results will be presented.

Broadband antireflection properties of material surfaces are of primary interest for a wide variety of applications: to enhance the efficiency of photovoltaic cells, to increase the sensitivity of photodetectors, to improve the performance of light emitting diodes, etc... In the past, broadband antireflection multilayer coatings were widely used and recently very low refractive index materials in thin film form have been fabricated by several groups. The research work presented in this paper aims at modeling and fabricating bi-periodic micro-structured silicon surfaces exhibiting broadband antireflection properties in the infrared range. These structures of pyramidal shape, which typical dimensions are smaller than the wavelength, are not in the Effective Medium Theory (EMT) validity domain. The optimization of the optical properties of such patterned surfaces needs a fully Finite Difference Time Domain (FDTD) rigorous description of light propagation phenomena. The influence of various opto-geometrical parameters such as period, depth, shape of the pattern is examined. The antireflective properties of such bi-periodic patterned surfaces is then discussed using the photonic crystal theory and photonic band diagrams description. The structure is considered as a two dimensional periodic structure with a nonuniform third dimension. Correlations between the density of Bloch modes, flatness of dispersion curves and the surface reflectance are presented. The last part of this paper is devoted to the presentation of the fabrication and the characterization of the structures. Low cost and large surface processing techniques are proposed using wet anisotropic etching through a silica mask obtained by photolithography or nanoimprinting.

The unavoidable absorption of thin films used in antireflective coatings forms a permanent bottleneck in the development of optics for high power laser applications. A valid alternative would be the micro-structuring of the optics surface, realizing a diffraction grating which emulates the functioning of an Anti-Reflection thin film layer. Due to the absence of film material, this diffractive structure would not contribute to the overall absorption of the optics. This paper investigates the practical limits of this strategy, applied to zinc selenide as low absorption infrared substrate material.

The restricted field of view of traditional camera technology is increasingly limiting in many relevant applications such as security, surveillance, automotive, robotics, autonomous navigation or domotics. Omnidirectional cameras with their horizontal field of view of 360° would be ideal devices for these applications if they were small, cost-effective, robust and lightweight. Conventional catadioptric system designs require mirror diameters and optical path lengths of several centimeters, often leading to solutions that are too large and too heavy to be practical. We are presenting a novel optical design for an ultra-miniature camera that is so small and lightweight that it can be used as a key navigation aid for an autonomous flying micro-robot. The catadioptrical system consists of two components with a field-stop in-between: the first subsystem consists of a reflecting mirror and two refracting lens surfaces, and the second subsystem contains the imaging lens with two refractive surfaces. The field of view is 10°(upward) and 35°(downward). A field stop diameter of 1 mm and a back focal length of 2.3 mm have been achieved. For low-cost mass fabrication, the lens designs are optimised for production by injection moulding. Measurements of the first omnidirectional lens prototypes with a high-resolution imager show a performance close to the simulated values concerning spot size and image formation. The total weight of the optics is only 2 g including all mechanical mounts. The system's outer dimensions are 14.4 mm in height, with a 11.4 mm × 11.4 mm foot print, including the image sensor and its casing.

A robust optical sensor for liquid control in fluidic channels is reported. The sensor operates on light intensity modulation resulting from alteration of total internal reflection into partial reflection. When a liquid guided in a channel covers an integrated prism, the total internal reflection is changed into a partial reflection, resulting in an intensity modulation of the reflected light. The set-up comprises a fibre which is built in a coupler unit with integrated LED and photodiode as well as a prism micro-machined directly into a micro-fluidic polymeric channel by laser ablation. The Prism is of 45-90-45° type with a dimension of 0.5 mm × 1 mm × 2 mm. In this design the radiation of the LED light source is transmitted and collected from the prism by a 50:50 fibre coupler by means of total or partial internal reflection. The sensor was characterised by filling alternately the channel with water and air. The signal level for the liquid in contact with the prism was determined to be 222 mV while the signal level of the air filled channel was 336 mV. The influence of stray light onto the sensor signal was tested by applying a strong uncollimated illumination of the channel. Only a small increase in the output signal level in the presence of air but a strong increase in case of the presence of water could be detected. However, the discrimination between air and liquid was still possible sufficiently (290 mV for liquid, 340 mV for air). The sensor was also demonstrated to be operated as a micro-refractometer.

The integration of optical components in microfluidic devices is an emerging issue for downscaling analytical processes to lab-on-a-chip systems. Our approach is to build a one compound polymer system, which combines optical waveguides with microfluidic channels in one monolithic device. In addition the entire chip shall be optimized to use optical interfaces only. The processing of channels and waveguides is based on photodegradation of PMMA through deep ultraviolet (DUV) radiation in both cases. In a first step, microfluidic trenches with a depth of 5 μm are structured by DUV lithography with a subsequent developing process dissolving the exposed material. Waveguides, geometrically crossing the channel, get implemented by a second DUV lithography step. In a last step, the transparent optofluidic devices are covered to form channels and sealed with a second PMMA substrate by thermal bonding. The process was optimized to achieve leakage free channels without any disturbance of the waveguide behaviour. The paper discusses the manufacturing process and shows experimental results that serve as preparation for ongoing simulations for sensing applications. In first experiments the optical attenuation of the waveguides decreased by 1.2 dB at a wavelength of λ = 638 nm, when the empty channels were filled with deionised water which corresponds to a change in the refractive index of 0.33.

Computer generated holograms (CGH) are used to transform an incoming light distribution into a desired output. Recently multi plane CGHs became of interest since they allow the combination of some well known design methods for thin CGHs with unique properties of thick holograms. Iterative methods like the iterative Fourier transform algorithm (IFTA) require an operator that transforms a required optical function into an actual physical structure (e.g. a height structure). Commonly the thin element approximation (TEA) is used for this purpose. Together with the angular spectrum of plane waves (APSW) it has also been successfully used in the case of multi plane CGHs. Of course, due to the approximations inherent in TEA, it can only be applied above a certain feature size. In this contribution we want to give a first comparison of the TEA & ASPW approach with simulation results from the Fourier modal method (FMM) for the example of one dimensional, pattern generating, multi plane CGH.

With help of liquid crystal polymers (LCP) a polarization sensitive diffuser has been realized. By using convex microstructures made of LCP and an index matching layer, two distinct functions depending on the orientation of the device and the polarization state of the input light are realized. For one polarization the light pass through the device with no changes and for the perpendicular polarization, the light is diffused by the microstructures.

The authors have developed a new compact integration concept for a green laser emitter. Compact green light sources are of great interest for several applications such as in spectroscopy and mobile displays. The requirements for such sources are low noise, high-frequency modulation capability, compactness, reliability, low power consumption, and low cost. The developed green-light source fulfils these requirements due to its dense integration while allowing larger tolerances within the fabrication processes. The green-laser emission of 30 mW is generated using second harmonic generation (SHG) in a nonlinear crystal. As pumping light source, a reliable GaAs semiconductor laser diode with an emission wavelength at 1060 nm has been developed. This single-wavelength distributed feedback (DFB) laser diode has a sidemode suppression ratio better than 40 dB and an optical power of up to 325 mW. The SHG device is a periodically poled lithium niobate (PPLN) waveguide. The 1060 nm pump light is directly coupled to the passive nonlinear waveguide. To enable the precise operating temperature conditions for DFB and PPLN, both components are mounted on separate temperature controllers. As confirmed also by thermo-mechanical simulations, the presented compact, reliable integration of green-light emitter enhances the overall yield by introducing a fabrication process tolerant integration scheme.

A strongly anisotropic photonic crystal structure was designed using form birefringence. It has a low group velocity close to a split band edge (SBE) and large field enhancements proportional to the fourth power of the number of periods are predicted. Numerical results are presented illustrating the bandgap behavior as a function of anisotropy and an effective negative index property is discussed.

Coupling structures are critical building blocks that have a big influence on the performance of board-level optical interconnections. 45° micro-mirrors deflect the light beam over 90° and are used for out-of-plane coupling in single layer structures and out-of-plane and inter-plane coupling in multilayer structures. Two different approaches are being presented: a micro-mirror that is directly integrated with the multimode waveguides and a discrete coupling element that can be plugged into a cavity in the optical layer. The advantage of the integrated micro-mirror is the high achievable alignment accuracy. The discrete couplers on the other hand have the advantage that they can be characterized and measured prior to the insertion into the optical layer. Both mirror configurations are discussed and the performance is evaluated at wavelength 850nm.

We present an enhanced out-of-plane coupling component for Printed Circuit Board-level optical interconnections. Rather than using a standard 45° micro-mirror to turn the light path over 90° we introduce a curvature in the mirror profile and incorporate an extra cylindrical micro-lens for beam collimation. Both modifications enable an increase in coupling efficiency and are extensively investigated using non-sequential ray tracing simulations in combination with Matlab optimization algorithms. The resulting design is fabricated using Deep Proton Writing and experimental characterization of the geometrical properties and measured coupling efficiencies are presented.

An important challenge that remains to date in board level optical interconnects is the coupling between the optical waveguides on printed wiring boards and the packaged optoelectronics chips, which are preferably surface mountable on the boards. One possible solution is the use of Ball Grid Array (BGA) packages. This approach offers a reliable attachment despite the large CTE mismatch between the organic FR4 board and the semiconductor materials. Collimation via micro-lenses is here typically deployed to couple the light vertically from the waveguide substrate to the optoelectronics while allowing for a small misalignment between board and package. In this work, we explore the fabrication issues of an alternative approach in which the vertical photonic connection between board and package is governed by a micro-optical pillar which is attached both to the board substrate and to the optoelectronic chips. Such an approach allows for high density connections and small, high-speed detector footprints while maintaining an acceptable tolerance between board and package. The pillar should exhibit some flexibility and thus a high-aspect ratio is preferred. This work presents and compares different fabrication methods and applies different materials for such high-aspect ratio pillars. The different fabrication methods are: photolithography, direct laser writing and deep proton writing. The selection of optical materials that was investigated is: SU8, Ormocers, PU and a multifunctional acrylate polymer. The resulting optical pillars have diameters ranging from 20um up to 80um, with total heights ranging between 30um and 100um (symbol for micron). The aspect-ratio of the fabricated structures ranges from 1.5 to 5.

With the ongoing progress in chip scaling, the data flow to and from chip packages is increasing accordingly. The simultaneous increase of channel count and channel speed in an essentially constant form factor becomes a more and more demanding challenge. The resulting I/O-bottleneck is considered to be a major limiting factor for the overall performance of future chip packages and computing systems. Optical interconnects offer both increased channel density as well as longer link reach at high frequencies. Our current work focuses on integrating optical I/O with standard organic packages in order to maximize the aggregate data flow to and from such packages. We present a novel approach for attaching an electro-optical conversion module directly on top of the organic chip package, together with experimental results of a first prototype implementation.

The increasing demand and use of optical fibers for sensor-applications and the increasing use of short distance optical communication on backplanes has been witnessed because of their many advantages. The work described in this paper provides a technology platform to increase the integration and compactness of these optical applications. We present the establishment of a bendable package of optical interconnections and opto-electronic components. Standard commercially available GaAs VCSEL's and GaAs photodetectors are thinned down to a thickness of 30 µm and embedded into a stack of cladding-, core- and Polyimide layers. Multimode waveguides are patterned in the core layer to connect the VCSEL and photodiode array's. Laser ablated 45 degrees micro-mirrors couple the light from the embedded opto-electronic components into- and out of the waveguides. The final layer-stack with embedded active optical interconnections is highly flexible and shows no warpage due to a symmetrical layer build-up. Galvanic fan-out of the contact pads of the VCSEL's and PD's is realized by laser ablated via's and sputtered copper tracks in between the layers. The stand-alone optical foil is only 160 μm thick and can reach a minimum bending radius of 0.5 cm. Optical bending losses of the flexible waveguides are lower than 0.25 dB per cm for a 8 mm bending radius at a wavelength of 850 nm.

We report on the design and fabrication of polymer microlenses fabricated on patterned SU-8 layers in view of integrating microlenses on VCSEL arrays for laser beam shaping. For a standard top-emitting VCSEL, the lens has to be fabricated on a thick intermediate layer (pedestal) whose optimal thickness can be modelled as a function of the initial and of the aimed optical properties of the VCSEL beam. In this work, pedestals are fabricated with SU-8, which is a negative-tone photoresist transparent at the lasing wavelength. Lens deposition is realized using a robotized silicon microcantilever spotter technique after a simple SU-8 photolithography step in order to define high aspect ratio cylindrical pedestals with wide range diameters [30-140μm]. The effect of pedestal diameter on the final contact angle and curvature radius has been investigated using non contact optical profilometry and scanning electron microscopy. We show that this technique leads to a complete delimitation of the polymer droplets and to a better control of the final lens size. Moreover, lens positioning is fully ensured by the self-alignment of the droplet with the pillar center and consequently with the VCSEL source, and allows for meeting the stringent requirements on alignments.

Today a lot of applications (datacommunication, automation, sensing, automotive . . . ) make use of plastic optical fibers (POF) to carry data over short distances. In this paper we will focus on the case study of a resonant cavity light emitting diode (RCLED) in combination with a POF. First we compare the optimal coupling efficiency of different coupling configurations (with ball lens, micro-lens and reflector) using non-sequential ray tracing software. Because we want to involve all specified external perturbations of the complete system we use Monte-Carlo based 3D opto-mechanical tolerancing to obtain the ideal optical system and its dimensions and tolerances. The definition of the best design will be based on a guaranteed minimum coupled power for a system subject to prescribed dimensional and geometrical deviations. To define the source model, we used extensive measurements. We import the measurement data of the light source to obtain realistic simulation results. Therefore we performed a full quantitative characterization of this source. More in particular we measured the total output power, the optical spectrum and the far-field pattern by using an integrating sphere, a spectrum analyzer and a goniometric radiometer respectively at different temperatures. We investigated two different situations, one where the RCLED emits light directly in air and the other where the light of this source first passes through epoxy before being measured in air like it is the case in a lot of coupling configurations.

Integrated optic single mode waveguides in polymer substrates are of interest for several applications especially in the visible wavelength range e.g. to build waveguide components for biophotonic, sensors or passive splitters. The manufacturing process contains DUV or UV lithography and some different pre or post exposure bakes depending on the used type of polymer. Chromium masks offer facile and controllable processing and rapid exposure times. Surface waveguides can be covered with an index matched cladding substrate on top to get buried light guiding. The end faces and also the over all thickness of about 1 mm of the component packages gives the possibility for a stable coupling between fiber arrays and planar waveguide substrates. The paper describes the results of a single mode field analysis and the experimental adjustment of polymer waveguides for wavelengths within the visible range of light to achieve low coupling losses. Some different manufacturing process steps are compared depending on the used polymer material. A comparison between the measured waveguides and fiber mode near field diameters and the nominal calculated numerical apertures are presented. The different insertion loss is measured and illustrated as well.

In this paper we describe the measurement of optical propagation losses in polymer waveguide structures. The fabrication of single mode waveguides using direct laser writing is also presented in the paper. Simulated and experimental results of coupling between two single mode waveguides at varying coupling length are also presented. Finally the concept of using a herringbone structure in a non destructive technique of loss measurement in waveguides is presented with simulation results.

The use of nano-structured elements in the fabrication of micro-optical subwavelength components requires a fully vectorial solution to Maxwell's curl equations. In this paper, we compare the results generated by two of the main methods used in the solution of the curl equations, the Fourier Modal Method (FMM) and the Finite Difference Time Domain (FDTD) method. We address the computational issues surrounding the accurate modelling of nano-structured elements (with features in the 10nm-100nm range) for a range of micro-optical elements, e.g. cylindrical lenses, photonic bandgap reflectors and polarisation dependent beamsplitters. Finally, we show the experimental verification of the nano-structured designs using microwave radiation.

Design of all-optics reconfigurable GRIN (Gradient-Index) planar structure for crossover and parallel interconnects will be presented. Design represents a unique combination of GRIN materials, simple geometry optics and waveguide technology for both parallel and distributed processing and communication networks. The optical analysis is based on-axis and off-axis multiple imaging property of GRIN components. The analysis includes the study of the Point Spread Function (PSF) for describing the performance of the GRIN planar structure and the evaluation of the Space Bandwidth Product (SBP) for estimating the number of channels which can be handled. The dependence of the number of channels on the wavelength of the light and the aperture of the planar interconnect is shown. The results are given for five working wavelengths of Laser Diode (LD) and for four transverse aperture of reconfigurable optical interconnect.

Optical encoders are widely used to detect the position, angle or speed in precise control systems. A rotary optical encoder mainly comprises an optical sensor and an optical grating element with a fine grating pitch. In order to improve the resolution of rotary optical encoders, the grating pitch in the optical grating element should be reduced as small as possible. That is, the pulse per revolution (ppr) in the optical grating element must be increased markedly. However, an optical grating element having over 10,000 ppr is difficult to achieve by traditional methods. In this paper, a novel method is proposed and demonstrated to replicate an optical grating element with a high ppr. Furthermore, the tiny signals generated from fine grating pitches in the optical grating element have been also measured by using a conventional optical pickup head.

POFs (polymer optical fibers) replace the established communication media as copper and glass step by step in short distance communication systems, because of their economical and easy-manageable advantages. POFs are used in various fields of optical communication, e.g. the automotive sector or for "Triple-Play" in the in-house communication. The state of the art technology are single mode communication systems. The using of only one wavelength for communication limits the bandwidth. For future scenarios this technology is the shortage of bandwidth, e.g. for HDTV with IP-TV. One solution to breakthrough this limitation is to use more than one wavelength over one single fiber, this is so-called WDM (wavelength division multiplexing). But this multiplexing technology requires two more technical keyelements: a multiplexer, which combines the multi-wavelengths signals into one fiber and a demultiplexer at the end of the network to separate the colored signals. In this paper computer simulations of the design of different WDM keyelements are shown. The basic concept is a grating on a higher-order mirror to combine and separate the multi-colored channels. The following realization of the demultiplexer is planed to be done with injection molding. This technology offers easy and very economical processing. These advantages make this technology first choice for optical components in the low-cost array. All components can be fabricated by means of injection molding and micro injection molding. First promising prototypes of this manufacturing technology are presented in this paper as well.

This paper reports on the development and validation of a new technology for the fabrication of variable line-spacing non-planar diffraction gratings to be used in compact spectrometers. The technique is based on the standard lithographic process commonly used for pattern transfer onto a flat substrate. The essence of the technology presented here is the lithographic fabrication of a planar grating structure on top of a flexible membrane on a glass or silicon wafer and the subsequent deformation of the membrane using a master shape. For the validation of the proposed technology we fabricated several reflection concave diffraction gratings with the f-numbers varying from 2 to 3.8 and a diameter in the 4 - 7 mm range. A glass wafer with circular holes was laminated by dry-film resist to form the membranes. Subsequently, standard planar lithography was applied to the top part of the membranes for realizing grating structures. Finally the membranes were deformed using plano-convex lenses in such a way that precise lens alignment is not required. A permanent non-planar structure remains after curing. The imaging properties of the fabricated gratings were tested in a three-component spectrograph setup in which the cleaved tip of an optical fiber served as an input slit and a CCD camera was used as a detector. This simple spectrograph demonstrated subnanometer spectral resolution in the 580 - 720 nm range.

The design and performance of a highly miniaturized spectrometer fabricated using MEMS technologies are reported in this paper. Operation is based on an imaging diffraction grating. Minimizing fabrication complexity and assembly of the micromachined optical and electronic parts of the microspectrometer implies a planar design. It consists of two parallel glass plates, which contain all spectrograph components, including slit and diffraction grating, and can be fabricated on a single glass wafer with standard lithography. A simple analytical model for determining spectral resolution from device dimensions was developed and used for finding the optimal parameters of a miniaturized spectrometer as a compromise between size and spectral resolution. The fabricated spectrometer is very compact (11 × 1.5 × 3 mm³), which allowed mounting directly on top of an image sensor. The realized spectrometer features a 6 nm spectral resolution over a 100 nm operating range from 600 nm to 700 nm, which was tested using a Ne light source.

A ray tracing simulation method for integrated optics hollow waveguides has been developed. This method has been tested on Silicon waveguides with good results, providing a suitable design tool for new devices using this type of waveguides. The simulations allow the design of new guiding structures based on hollow waveguides, like input tapers to reduce the insertion losses. The study of the hollow waveguide behavior with different refractive indices opens the way for their use as refractive index sensors.

Provided that suitable materials are available, novel structuring methods, such as two-photon-3D-lithography (2P3DL) and nano-imprint-lithography (NIL) are promising approaches for the fabrication of organic complex 2D and 3D structures. Optical materials based on photopolymerizable resins combined with novel efficient multi-photon photoinitiators can be used for a fast and simple fabrication of μ-optical components for MOEMS. The true 3D capabilities and the high spatial resolution of the 2P3DL permit the fabrication of nearly any optical designs from CAD. With supplementary feedback controlled positioning of the laser focus, a material can be processed at an explicit target position, e.g. on an organic LED or photo cell. The position of fabricated μ-optics relative to such devices is determined by 3D sample registration prior to the structuring process. Therefore, the alignment of laser written structures to existing sample features becomes a part of the fabrication process and no further assembly is required. We demonstrate the design and the fabrication of various μ-optical structures such as waveguides and μ-lenses for photonic μ-systems by means of 2P3DL. Furthermore, μ-lens masters prototyped by means of two-photon-3D-lithography and their replication via a PDMS stamp by means of NIL are presented. In addition, it can be shown that such μ-optical systems can be fabricated in situ on organic LEDs or organic photo cells enabling powerful building blocks for μ-optical systems.

We present a new method for realizing optical connections to multi mode fiber, which eliminates the need for standard connectors. With such a device the fiber termination can be avoided, so that dramatically reducing the cost of installation of an optical network. Moreover the optical connection can be carry out by not specialized personnel. Its main application is in the new deployment of the local area networks (LAN) and the emerging market of the home area networks (HAN). The basic idea is to use advantageously the principle of bending losses for extracting signal from multimode fiber. Conversely the same effect can be used for inserting light into fiber without the need of connector or even without any controlled splicing and polishing operation. Studying the variation of losses versus bending radius, evaluating the reliability of a fiber under stress and considering the fabrication tolerances it's possible to determine the right position and angle for effectively inserting and extracting light. The focusing lenses have been implemented into a mechanical holder. Some prototypes have been realized by plastic molding technique. The optical study, the realization process and the first results are presented in this paper.

Analysis and optimisation of ultra-high-speed Z-cut lithium niobate (LN) electrooptic modulator, operating at a high frequency region, by using full wave finite element numerical technique has been demonstrated. Investigation of the effects of adjusting the buffer layer thickness, the electrode height and the waveguide trapezoidal profile on the microwave effective index (N_m), the characteristic impedance (Ζ_c), the microwave losses (α_c) and the half-wave voltage-length product (V_πL) has been reported. Optimisation of the above parameters yield to a novel design of LN modulator with a low V_πL and high bandwidth operating at a frequency range between 1-100 GHz. The frequency dependent dispersion of the key device parameters with aim to determine the device suitability for high speed operation has been demonstrated.

Over the last decades the significant grow of interest of photonics devices is observed in various fields of applications. Due to the market demands, the current research studies are focused on the technologies providing miniaturized, reliable low-cost micro-optical systems, particularly the ones featuring the fabrication of high aspect ratio structures. A high potential of these technologies comes from the fact that fabrication process is not limited to single optical components, but entire systems integrating sets of elements could be fabricated. This could in turn result in a significant saving on the assembly and packaging costs. We present a brief overview of the most common high aspect ratio fabrication technologies for micro-optical components followed by some characterization studies of these techniques. The sidewall quality and internal homogeneity will be considered as the most crucial parameters, having an impact on the wavefront propagation in the fabricated components. We show the characterization procedure and measurement results for components prototyped with Deep Proton Writing and glass micromachining technology replicated with Hot Embossing and Elastomeric Mould Vacuum Casting technology. We discuss the pros and cons for using these technologies for the production of miniaturized interferometers blocks. In this paper we present the status of our research on the new technology chain and we show the concept of microinterferometers to be fabricated within presented technology chain.

We discuss the micro-integration of an optical write-read head for disk-based volume holographic data storage. A particular approach based on the design principle of planar-integrated free-space optics and on photopolymer storage materials is proposed. Numerical construction parameters are calculated and initial experimental results concerning the performance of the photopolymer are presented.