Christoph Wächter

• Fraunhofer Institute for Applied Optics and Precision Engineering

We report on the fabrication and physical characterization of optical biosensors implementing simultaneous label-free and fluorescence detection and taking advantage of the excitation of Bloch surface waves at a photonic crystal’s truncation interface. Two types of purposely designed one-dimensional photonic crystals on molded organic substrates wi...

Periodic arrays of high refractive index structures are arranged below the anode of a white, bottom-emitting Organic LED. Significant enhancement of the emission into air and substrate is achieved without introducing pronounced chromatic effects.

For high quality optical coatings the knowledge of the losses of the deposited materials is essential. A precise measurement of low Im(n+ik )≤ 10-6 at an intended operation wavelength and with low intensity can be achieved in waveguide configurations, whereby leaky waveguide configurations allow one to analyze losses of high- and low-index media of...

Bloch surface wave (BSW) sensors to be used in biochemical analytics are discussed in angularly resolved detection mode and are compared to surface plasmon resonance (SPR) sensors. BSW supported at the surface of a dielectric thin film stack feature many degrees of design freedom that enable tuning of resonance properties. In order to obtain a figu...

Grating waveguide structures have been prepared by the deposition of a high refractive index broadband antireflection coating onto a patterned fused silica substrate. Aluminum oxide and hafnium oxide as well as mixtures thereof have been used as coating materials. Optical reflection measurements combined with atomic force microscopy have been used...

We present a systematic experimental study on the impact of disorder in advanced nanophotonic light-trapping concepts of thin-film solar cells. Thin-film solar cells made of hydrogenated amorphous silicon were prepared on imprint-textured glass superstrates. For periodically textured superstrates of periods below 500 nm, the nanophotonic light-trap...

Highly efficient state of the art organic light-emitting diodes (OLED) comprise thin emitting layers with thicknesses in the order of 10 nm. The spatial distribution of the photon generation rate, i.e. the profile of the emission zone, inside these layers is of interest for both device efficiency analysis and characterization of charge recombinatio...

Micro- and nanostructures enable specific optical functionalities, which rely on diffractive effects or effective medium features, depending on pattern dimension and wavelength. Performance predictions of optical systems which make use of nanostructured materials require having an accurate description of these materials ready to hand within the opt...

The emission pattern of large area organic LED sources needs to be adapted to intended applications. Different approaches using thin micro optical arrays are discussed to obtain significant deviations from the well-established Lambertian shape.

Highly efficient beam splitters are important for a variety of high power laser applications. We prove different approaches like aperture and amplitude splitting for practicability for single- and multimode laser sources. Combining of micro- and macro-optical fabrication technologies allows novel monolithic free form splitting components with imple...

The application of large area OLEDs for lighting and signage purposes potentially requires essential changes of the common Lambert-like emission pattern. We demonstrate an array based micro optical approach for pattern shaping of area light sources based on distorted Fourier imaging of an aperture array with a micro lens array. Narrow angular emiss...

This chapter reports concepts and realizations of integrated optical circuits, i. e., the concept of optical waves which are traveling through planar circuits and confined in one or two directions. Integrated optical components such as array waveguide gratings (AWGs) turned out to be a key enabler for modern broadband optical communications based o...

We report on the fabrication and optical simulation of a plasmonic light-trapping concept for microcrystalline silicon solar cells, consisting of silver nanostructures arranged in square lattice at the ZnO:Al/Ag back contact of the solar cell. Those solar cells deposited on this plasmonic reflection grating back contact showed an enhanced spectral...

Metallic inclusions in layered structures can have noticeable effects onto scattering and absorption due to the coupling of the external electromagnetic field and local charge oscillations. These effects are strongly related to both the geometry of the individual particle as well as to the array structure. Having in mind the efficiency improvement...

Metallic thin films and metallic nanoparticles give rise to peculiar optical effects in frequency regions where an external electromagnetic field can couple to charge oscillations resonantly. Plasmons localized at interfaces and closed surfaces give rise to huge local field enhancements which can be used for a great variety of applications based o...

In this contribution, we show that micro-optical elements are well suited to exploit the potential of organic lightemitting 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 co...

One major performance parameter for organic light-emitting diodes (OLEDs) in display and illumination applications is the overall efficiency of the device, which is directly affected by the emitter's internal luminescence quantum efficiency q. It is very desirable to determine q of the emitter in-situ, i.e. in electrically driven operation, since p...

The optical performance of organic LED can be optimized by using diffractive and/or refractive structures. Simulation of such complex systems requires mixed modeling of the emission from thin film stacks, diffractive, and refractive elements.

The optical properties of OLEDs can be tailored by optimization of the layer stack and by implementation of micro- and/or nano-optical structures. But the effect of changing the OLED configuration on the device performance crucially depends on the optical properties of the emissive layer. The aim of this contribution is twofold. First, we will prop...

The efficiency of organic light emitting diodes is known to be optically limited by different light trapping effects within the device structure. Several approaches have been suggested to enhance the transfer of radiation generated within the device into free space radiation. These approaches include nanoscale wave optical effects to optimize the s...

Organic light emitting diodes are deemed to be valuable light sources for displays and general illumination in the future. In the last decade remarkable progress was made concerning materials, lifetime, and production techniques. One of the remaining challenges is to increase the light extraction efficiency of these devices. Due to the internal str...

Adapting the concept of solid immersion lenses, we numerically study a micro-optical scheme for conventional high-index and photonic-crystal waveguide coupling by using a combination of different numerical methods such as ray tracing, angular-spectrum propagation, finite-difference time-domain simulations, and finite-element-method simulations. The...

Direct coupling from fibres to waveguides requires field matching to achieve high coupling efficiency. 3D on-chip tapers are well suited in principle, but practicability may depend on materials and geometrical structures used for the waveguide chip, especially when photonic crystal defect waveguides are involved. To adapt the spot size of the fibre...

Current software simulation tools in integrated optics allow to tackle directly a multitude of complex problems which occur in high index contrast waveguiding. Appropriate eigenmode solvers and propagation schemes account for the vectorial character of the fields, and transmissive and reflective device properties can be derived. For the fibre-chip...

The paper presents a short review of the theoretical basics of modeling techniques in integrated optics, essentially mode solving and field propagation, and some of the underlying numerical approaches in short. To meet the requirements of an effective design process of a potentially complex waveguide circuitry different levels of abstraction are us...

There is a great potential of microring-resonators as optical add/drop-multiplex modules in photonics with very large scale integration. The area consumption per ring is incredibly small, and complex circuitry seems feasible. But, en route to application the production of ring resonators has to ensure specifications which can compete with those of...

A reciprocity theorem was derived from Maxwell's equations for Photonic crystal waveguides (PCW). Starting from a strict orthogonality relations for PCWs, a set of simple evolution equations was derived to determine the field distribution in a PCW for a fixed frequency and for given initial conditions. The influence of dispersion of a two level sys...

We present the investigation of 3D micro-optical structure formation in photopolymerizable polymers due to controlled self-writing processes. A locally deposited amount of energy during the material exposure leads to a local non-linear change of the refractive index. This results in self-focusing and self-guiding effects. The influence from a set o...

In the field of active phased array antenna applications, the needs for high frequency carriers and very wideband communication and radar systems technologies with low volume, e.g., for airborne applications, drives the development of new concepts for all components of such networks. One building block for the beamforming in active antennas is the...

Integrated passive and active optical devices are the key components in current and future data transfer technologies. In order to fulfill future requirements in miniaturization for diffractive, refractive and integrated optical devices, new materials with higher thermal stability and a better compatibility to processing techniques used in conventi...

A local exposure of UV-sensitive polymers leads to a local curing. This corresponds to a saturable and irreversible nonlinear change of the refractive index, which evidently leads to a filamentation of the hardening polymer. This paper investigates the physical background of these effects and analyzes how the different influencing factors could be...

The exposure of UV-sensitive polymers leads to a saturable and irreversible change of the refractive index up to 0.1 due to the polymerization generated changing material density. This non-linear phenomenon has a strong impact on the structure formation in the UV-assisted fabrication of thick micro-optical elements. E.g., appearing self-focusing ef...

Starting from Maxwell"s equations we derive a new orthogonality relation and a recirpocity theorem for photonic crystal waveguide modes. The orthogonality relation implies an integration over a plain nonparallel to the waveguide direction. This is in contrast to the common orthogonality relations where an integration over the whole photonic crystal...

Starting from Maxwell"s equations we derive a new orthogonality relation and a recirpocity theorem for photonic crystal waveguide modes. The orthogonality relation implies an integration over a plain nonparallel to the waveguide direction. This is in contrast to the common orthogonality relations where an integration over the whole photonic crystal...

The rapid growing demands on the number of data transport channels in integrated optical circuits are hitting the border of the integration density, which is realizable with the currently used planar technologies due to the limited wafer size. An approach to overcome this problem by the stacking of optical single-mode waveguides is presented. This...

The booming telecom market pushes the development towards highly integrated optical devices. For a breakthrough in the increase of packaging densities, a bypass of the limited horizontal dimension of a waveguide chip is necessary. This leads to an introduction of a vertical integration scheme which needs an adapted fabrication method to meet the re...

The rapid growth of communication continuously demands an increasing number of data transport channels. We present an approach towards a substantial growth of channel numbers within the integrated optical waveguide chip. This is accomplished by introducing a vertical integration scheme, which is implemented with stacked polymer waveguides. To meet...

The booming telecom market pushes the development towards highly integrated optical devices. For a breakthrough in the increase of packaging densities, a bypass of the limited horizontal dimension of a waveguide chip is necessary. This leads to an introduction of a vertical integration scheme which needs an adapted fabrication method to meet the re...

In the present paper we review the state of the art of two complementary propagation techniques with applications for integrated optics device modeling: the Finite-Difference Time-Domain and the Beam Propagation Method. In both cases we focus on their main features such as the types of propagation schemes and the material effects that can be modele...

We present a recently developed technology for the stacking of optical waveguides using hybrid inorganic-organic polymers (ORMOCER(R)s). Among advantages with respect to the use of low-cost conventional processing methods (e.g. photopatterning, spin coating), this material system offers high thermal stability and low optical attenuation at telecom...

The UV-reaction molding technology enabling for the fabrication of microoptical elements with rectangular, triangular or circular cross-sections (waveguides, prisms, lenses) in optical polymers is described. Multimode waveguide optical interconnects, coupling prisms and holding structures for fibers can be fabricated in one step. A three-dimensiona...

The potential of 3D integrated optics based on different technological schemes is investigated. Theoretical and experimental results for waveguide geometries with stacked waveguide layers and with waveguide circuits prepared on topological structures are reported as well. Within waveguide geometries including individual guides in a sequence of stac...

An off–on switching scheme is introduced which blocks a waveguide path in the passive off-state and transmits the signal in the active on-state. The operating principle is based on the self-diffraction of a narrow guided beam when it escapes from a waveguide with two-dimensional confinement into a region of appropriate length with basically one-dim...

A new off-on switching scheme is introduced which blocks a waveguide path in the passive off-state and transmits the signal in the active on-state. The operating principle is based on the self-diffraction of a narrow guided beam when it escapes from a waveguide with two dimensional confinement into a region of appropriate length with at most one di...

A new off-on switching scheme is introduced which blocks a waveguide path in the passive off-state and transmits the signal in the active on-state. The operating principle is based on the self-diffraction of a narrow guided beam when it escapes from a waveguide with two dimensional confinement into a region of appropriate length with at most one di...

The level of integration within standard waveguide devices is usually restricted to the use of a single plane per wafer containing waveguides. Recently, concepts for waveguide structures with several planes of waveguides gain some special interest. They are mainly due to intentions to increase the number of channels per chip, to reduce the chip siz...

The level of integration within standard waveguide devices is usually restricted to the use of a single plane per wafer containing waveguides. Recently, concepts for waveguide structures with several planes of waveguides gain some special interest. They are mainly due to intentions to increase the number of channels per chip, to reduce the chip siz...

A new directional coupler device using a three-dimensional structure is presented. It consists of two stacked directional couplers (4 × 4-coupler as doubly stacked directional couplers). Coupling occurs both in horizontal and vertical direction. The device is intended to be the first of several devices employing three-dimensional structures. The pr...

We present the optimized design and the fabrication of an integrated-optic 1 by 32 multifunnel power splitter and the extension to a 2 by 32 splitter of the same type which we are the first to report. This splitter type operates by receiving the radiated input power at the end of a slab waveguide by funnel shaped waveguides of increasing width to c...

The beam propagation method (BPM) as a design tool for integrated optics is usually implemented with respect to waveguide configurations. When single interfaces and arbitrary refractive index distributions are used to define the geometry, the remaining limitations are due to the approximation of the Helmholtz-operator and the neglect of reflection....

We present a new coupler device consisting of two stacked directional couplers (4 X 4-coupler as doubly stacked directional couplers). Coupling occurs in both, horizontal and vertical direction. The structure was fabricated by UV- patterning of a stack of spin-coated polymethylmethacrylate layers. It serves as a basic element to study the accuracy...

We show that dispersion compensation over 70 km of a standard optical fiber at 20 Gbit/s can be achieved by using a strip waveguide configuration which consists of two dissimilar guides and is only a few centimeters long. Moreover, any required amount of third-order dispersion can also be compensated for.

Micro- and integrated-optical devices in glass and polymers are integrated increasingly in microsystems. Design and simulation of such optical elements are well developed. Ray tracing and a manifold of propagation and field calculation methods are available. First steps to CAD have been done. Using Ag+−Na+ ion exchange in special optical glasses, o...

Almost a decade ago a novel guiding scheme which relies on resonance effects such as one finds in Fabry-Perot resonators could be identified1. Those so-called Anti-Resonant-Reflecting-Optical-Waveguides (ARROWs) did not attract a considerable attention among the waveguide community until recently. They exhibit several striking peculiarities as quas...

We show that remote coupling in rib Antiresonant-Reflecting-Optical-Waveguide couplers can be achieved. It turns out that fully vectorial methods have to be used in order to determine both the field profiles and the propagation constants of the guided modes and to model the evolution of the fields, respectively. A reasonably agreement between theor...

In the conventional waveguiding concept the coupling distance between two waveguides is limited in order to ensure a sufficient overlap of the evanescent tails of the modal field profiles. The Anti-Resonant Reflecting Optical Waveguide (ARROW) scheme provides modal fields exhibiting an oscillating nature in the coupling region too, thus allowing fo...

Electro-optic waveguide elements are fabricated in the polymer-on-silicon technology. Measured field distributions of the inverted rib waveguides show excellent agreement with vectorial FEM calculations. This method is also used for electro-optic phasemodulator design. The dynamics of electrode poling is studied by reflectrometry. An integrated wav...

A properly tailored semiconductor multifilm configuration may be viewed as an effective waveguide with arbitrarily small refractive index differences. For the first time we report that strongly nonlinear effects as the existence of nonlinear guided waves can occur in materials with weak, off-resonant Kerr nonlinearities. This result is expected to...

Novel waveguiding schemes basing on resonance effects like the Bragg-reflection waveguide and the Anti-Resonant-Reflecting Optical Waveguide (ARROW) have attracted an increasing interest within the last few years. This is due mainly to the fact, that some drawbacks are inherent in the conventional waveguiding concept. This concerns for instance the...

Conventional waveguiding which relies on total-internal reflection (TIR) has been well established for several decades. A great variety of devices as single waveguides, directional couplers, Y-and X-beam splitters, Mach-Zehnder interferometers have been implemented. Although many applications, based on the conventional scheme, work very successfull...

The prismless excitation of guided waves in a Bragg reflection waveguide is investigated. We show that the guided modes can be directly excited by a plane wave that is incident from the air. An excellent agreement between the effective index of the guided mode in an ideal Bragg reflection waveguide and the minimum of the reflection curve has been f...

We introduce a novel nonlinear waveguide modulator. In contrast with conventional guides, an antiresonant reflecting optical waveguide that supports leaky waves is the basic element. After a comprehensive analysis of the linear properties of this antiguide we study the wave propagation when some components of the system are endowed with a material...

A novel waveguide coupler configuration consisting of two identical antiresonant reflecting optical waveguides is presented. The coupling length is a periodic function of the waveguide separation, and therefore a remote coupler can be realized.

The determination of the characteristics of multilayer waveguides, a necessity to construct integrated optical elements, is reported in detail, based on the matrix formalism for the description of light propagation in layered structures. Complex refractive indices are included aS well as arbitrary index profiles, for which an approximation method i...

We derive both the dispersion relation and the power flow for waves guided by a linear graded-index film in contact with an arbitrary nonlinear cladding. For an exponential-like graded-index profile and a Kerr-like nonlinearity we present numerical results and compare them with those familar from the step-index profile.

The design of integrated optics (IO) devices requires dedicated numerical algorithms and related software. Today's commercial tools cover a wide range of the needs, and manifold tasks can be solved this way. A short survey on specific IO-design tools and other design software that is related to particular aspects of IO is given. The basic physics a...

1 Abstract Optical microsystems consist of micro-optical, integrated-optical, mechanical and packaging components. Due to the hybrid nature and the high complexity of these microsystems a gen- eral design strategy is required. Here, we pres- ent an approach based on a specification- environment and a design-environment. The specification-environmen...