Knowledge of optical constants, i.e. refractive index n and extinction coefficient k , and light scattering properties of optical polymers are required to optimize micro-optics for light-emitting diodes in terms of efficiency, color properties and light distribution. We present here a model-based diagnostic approach to determine the optical properties of polymers, which should be particularly useful in the development of plastics for optical applications. Optical constants and scattering coefficients were obtained from transmission and reflection measurements in a wavelength range from UV to NIR taking into account scattering effects due to rough surfaces and volume inhomogeneity. Based on the models for the dielectric function, the molecular optical transition energies E g , critical point energies, Urbach energies and exciton transition energies were determined. Rayleigh and Mie scattering model and van de Hulst's anomalous diffraction theory were applied to characterize scattering due to volume inhomogeneities. Scalar diffraction theory was applied to account for surface roughness scattering. Atomic force microscopy with nanomechanical characterization was used to characterize domains in size and shape and to assign optical scattering to a suitable morphological model. The combined optical and mechanical characterization help to improve the qualification of new polymer materials for optical applications.

In recent decades, much research effort has been invested in the development of photonic integrated circuits, and silicon-on-insulator technology has been established as a reliable platform for highly scalable silicon-based electro-optical modulators. However, the performance of such devices is restricted by the inherent material properties of silicon. An approach to overcoming these deficiencies is to integrate organic materials with exceptionally high optical nonlinearities into a silicon-on-insulator photonic platform. Silicon–organic hybrid photonics has been shown to overcome the drawbacks of silicon-based modulators in terms of operating speed, bandwidth, and energy consumption. This work reviews recent advances in silicon–organic hybrid photonics and covers the latest improvements to single components and device concepts. Special emphasis is given to the in-device performance of novel electro-optical polymers and the use of different electro-optical effects, such as the linear and quadratic electro-optical effect, as well as the electric-field-induced linear electro-optical effect. Finally, the inherent challenges of implementing non-linear optical polymers on a silicon photonic platform are discussed and a perspective for future directions is given.

Polytetrafluoroethylene (PTFE), polyhexafluoropropylene (PHFP) and polychlorotrifluoroethylene (PCTFE) were heated to their decomposition temperature in a high vacuum. The emitted fragments passed an electron cloud, condensed on a substrate and formed fluoropolymer film. Growth rate of PTFE and PHFP films increased up to a factor five in the presence of the electron cloud. Mass spectrometry revealed changes in the mass spectra of fragments generated by thermal decomposition only and formed under electron activation. The observed changes were different for each fluoropolymer. Infrared spectroscopy (IRS) showed that the structure of the films was close to the structure of the bulk polymers. Atomic force microscopy (AFM) has revealed different morphologies of PTFE, PHFP and PCTFE films, suggesting a Volmer–Weber growth mechanism for PTFE and PHFP but a Frank-van der Merwe one for PCTFE. All films were smooth at nanoscale and transparent from ultraviolet to near-infrared region. Additional radio frequency (RF) plasma ignited in the emitted fragments at a low pressure increased mechanical characteristics of the films without losing their optical transparency and smoothness.

In this work, we report on the observation of the electric field-induced linear electro-optical effect in a silicon-based slot waveguide ring resonator covered by the nonlinear optical polymer Poly[(methyl methacrylate)-co-(Disperse Red 1 methacrylate)]. The device is fabricated in a photonic integrated circuit technology and intensity modulation is demonstrated to work in a direct-detection setup. As unique feature, the electric field-induced linear electro-optical effect allows to modulate the optical carrier wave with a time-varying electric field, while a static electric field can control its amplitude with no need for additional photonic components. Here, a linear tuning of the modulation-amplitude as function of the applied static electric field is demonstrated. This work paves a way toward novel integrated photonic device concepts.

Photonic integrated circuits (PIC) based on silicon-on-insulator technologies play a crucial role for the development of large-scale on-chip optical devices [1]. They address a variety of applications in optical sensing [2] and signal processing [3]. Many research efforts have been undertaken to develop a wafer-scale PIC platform by making use of well-established semiconductor fabrication processes. Active photonic devices based on standard silicon-on-insulator based PICs rely typically on the plasma dispersion effect in silicon to induce a refractive index change as function of an applied voltage. In this case, the silicon waveguide is doped in such a way that it forms a pn-junction. This is, however, accompanied by optical losses due to absorption and fundamental speed restrictions are related to carrier injection and removal. To overcome these limitations, it is desirable to integrate materials with large off-resonant electro-optical (EO) effect, which allows a change of refractive index by applying a dc or modulated electric field. In this way, no carrier transport is necessary giving rise to ultra-high speed data communication. Here, the silicon waveguide is structured like a capacitor. It consists of two silicon rails in which the active EO material is located in between. Functionalized organic materials are from great interest since they exhibit extraordinary high EO effects. In particular, they can exhibit both, a linear and quadratic EO effect [4]. The advantage of organic EO materials is twofold. First, they exhibit strong EO effects and are highly transparent in the telecommunication wavelength range. Second, they exhibit off-resonant EO effects avoiding unwanted non-parametric processes like two photon absorption and free carrier absorption. The combination of organic materials with silicon-on-insulator based waveguides is known as silicon-organic hybrid (SOH) technology. Recent research has demonstrated a high-speed SOH phase shifter having bandwidths above 100 GHz [5]. Besides that, EO modulators with energy consumption in the atto-Joule per-bit regime have been realized, and also higher modulation formats have been demonstrated [6]. These results show clearly the potential of SOH devices for a next generation of signal processing. However, the integration of organic materials into a well-established silicon-on-insulator technology is still challenging because typical semiconductor fabrication processes are used with relatively high process-temperatures destroying the organic materials. To tackle this issue, an integration approach was proposed in which the organic material is deposited in a post-process. In this work, we review recent results on the hybrid integration of organic EO materials in a silicon-on-insulator technology. We outline some of the identified challenges regarding process compatibility and present preliminary results on the integration of organic materials in a photonic integrated circuit (PIC) technology. Here, we are focusing on EO applications for high speed data transfer employing the linear and quadratic EO effect. As an example, we demonstrate an intensity modulator fabricated in a 0.25 µm SiGe BiCMOS pilot line using 200 mm silicon-on-insulator wafers. This approach gives perspective for monolithically hybrid-integrated photonic devices in an electronic PIC (EPIC)-technology. References [1] D. Knoll et al., "High-performance photonic BiCMOS process for the fabrication of high-bandwidth electronic-photonic integrated circuits," 2015 IEEE International Electron Devices Meeting (IEDM), Washington, DC, 2015, pp. 15.6.1-15.6.4. [2] P. Steglich et al., "Optical biosensors based on silicon-on-insulator ring resonators: A review," Molecules 24.3 (2019): 519. [3] G. Alimonti, et al. "Use of silicon photonics wavelength multiplexing techniques for fast parallel readout in high energy physics," Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment (2018). [4] P. Steglich et al., "Quadratic electro-optic effect in silicon-organic hybrid slot-waveguides," Optics letters 43.15 (2018): 3598-3601. [5] L. Alloatti et al., "100 GHz silicon–organic hybrid modulator," Light: Science & Applications 3.5 (2014): e173. [6] S. Wolf et al., "Coherent modulation up to 100 GBd 16QAM using silicon-organic hybrid (SOH) devices," Optics express 26.1 (2018): 220-232.

On-chip integrated photonic biosensors can lead to major advances in medical diagnostics, food and environmental monitoring through the rapid, and precise analysis of various substances. This offers the prospect of a cost effective lab-on-achip-platform and a reliable point-of-care-diagnostic. One research focus for future on-chip integrated biosensors is directed towards the combination of photonic devices with silicon microelectronics technology. A preferable approach for this new generation of photonic biosensors is based on optical ring resonators. In this article, concepts and functionality of such on-chip integrated ring resonators are described. In addition, we present latest research results and approaches to increase the light-matter interaction by optimized waveguide structures.

Recent developments in optical biosensors based on integrated photonic devices are reviewed with a special emphasis on silicon-on-insulator ring resonators. The review is mainly devoted to the following aspects: (1) Principles of sensing mechanism, (2) sensor design, (3) biofunctionalization procedures for specific molecule detection and (4) system integration and measurement set-ups. The inherent challenges of implementing photonics-based biosensors to meet specific requirements of applications in medicine, food analysis, and environmental monitoring are discussed.

A novel method to determine the dispersion of the quadratic electro-optic effect in nonlinear optical materials by using a silicon-on-insulator microring resonator is presented. The microring consists of a silicon slot waveguide enabling large dc electric field strength at low applied voltages. The dispersion of third-order hyperpolarizability of a linear conjugated dye is approximated by using a two-level model for the off-resonant spectral region. As an example, the dispersion of the resonance wavelength of the resonator filled with a dye doped polymer was measured in dependence of the applied dc voltage. The polymer was poly (methylmethacrylate) doped with 5 wt% disperse red 1 (DR1), and the measurements have been carried out at the telecommunication wavelength band around 1550 nm (optical C-band). The described measurements represent a new technique to determine the dispersion of the third-order susceptibility and molecular hyperpolarizability of the material filled into the slot of the ring-resonator.

In this work, we report on the integration of functionalized organic materials in a photonic integrated circuit technology for electro-optical modulators. We outline some of the identified challenges in the hybrid integration of organic materials in a photonic integrated circuit technology and present an electro-optical modulator with ultra-low energy consumption. In a second part, we present a simulation study and provide a design guideline to achieve an optimized slot waveguide structure for the integration of a lightsource consisting of Erbium doped quinoline.

For the first time, an integrated electro-optical RF modulator based on the quadratic electro-optical effect with CMOS compatible sub-volt driver voltages is presented. As unique feature, this modulator provides an amplitude tuning of the modulated carrier wave. The silicon-based modulator was fabricated using process steps of an established photonic integrated circuit technology and covered by a nonlinear optical polymer in a post-process. We demonstrate a device tunability of up to 350 pm/V, surpassing state-of-the-art silicon modulators with an order of magnitude. Moreover, the ring resonator is designed to have an ultra-low per-bit energy consumption of 87 aJ/bit demonstrating the potential for high-performance photonic devices with low energy consumption.

In unserer hochtechnologisierten Gesellschaft spielt die optische Datenübertragung aufgrund der stetig wachsenden Informationsvielfalt eine immer bedeutendere Rolle. In den Anfängen der Nachrichtentechnik waren Datenraten von wenigen bit/s realisierbar. Heute werden mittels optischer Technologien Übertragungsraten von mehreren Gbit/s umgesetzt. Möglich wird dies durch neue Entwicklungen in der Chip-integrierten Photonik. Beispiele dafür sind Chip-integrierte elektrooptische Modulatoren und Schalter. In diesem Artikel werden neue Entwicklungen in der Chip-integrierten Photonik diskutiert und die experimentelle Charakterisierung der Bauelemente in Form eines Ringresonators beschrieben. Für die Experimente wird exemplarisch ein photonisches Bauelement genutzt, das aus einem hybriden Silizium-Polymer-Materialsystem besteht. Die Ergebnisse zeigen, dass diese Materialkombination vielversprechend für zukünftige Chip-integrierte photonische Bauelemente mit extrem geringem Energiebedarf ist.

This paper proposes a hybrid-waveguide ring resonator for on-chip biochemical sensing. Consisting of a low-loss strip-waveguide and a highly sensitive slot-waveguide integrated in a silicon photonic platform, it combines advantages of both waveguide types. In this way, it provides the unique feature to increase the sensitivity while maintaining low optical losses. Thus, this resonator structure may represent a promising alternative approach for future integrated biochemical sensing applications. This is suggested by a theoretical analysis, involving numerical simulation of the hybrid-waveguide ring resonator and an optimization of the slot-waveguide structure with regard to light-analyte-interaction. It is demonstrated that the hybrid-waveguide concept may overcome limitations in terms of overall resonator sensitivity, which is described by a figure of merit, connecting the optical losses with the resonator sensitivity.

Es wurde ein dreidimensionales Polymerfasernetzwerk aufgebaut, charakterisiert und anschließend daran das Enzym Pyrrolochinolinchinon-abhängige Glukosedehydrogenase (PQQ)GDH gebunden. Das Polymerfasernetzwerk wurde durch Elektrospinnen einer Mischung des Polymers Polyacrylnitril und verschiedener leitfähiger Polymere der Polyanilin-Familie auf Indium-Zinn-Oxid-Elektroden aufgebracht. Die so hergestellten Fasermatten erwiesen sich bei mikroskopischen Untersuchungen gleichförmig präpariert und die Faserdurchmesser bewegten sich im Bereich weniger hundert Nanometer. Das Redoxpaar Kaliumhexacyanoferrat (II/III) zeigte an diesen Polymer-Elektrodenstrukturen eine quasi-reversible Elektrochemie. Bei weitergehenden Untersuchungen an den enzymmodifizierten Fasern ((PQQ)GDH) konnten unter Substratzugabe (Glukose) bioelektrokatalytische Ströme nachgewiesen werden. Das Fasernetzwerk fungiert hier nicht nur als Immobilisierungsmatrix, sondern als auch als Teil des Signalwandlers.

Electrospinning is known as a fabrication technique for electrode architectures that serve as immobilization matrices for biomolecules. The current work demonstrates a novel approach to construct a conductive polymeric platform, capable not only of immobilization, but also of electrical connection of the biomolecule with the electrode. It is produced upon electrospinning from mixtures of three different highly conductive sulfonated polyanilines and polyacrylonitrile on ITO electrodes. The resulting fiber mats are with a well-retained conductivity. After coupling the enzyme pyrroloquinoline quinone-dependent glucose dehydrogenase (PQQ-GDH) to polymeric structures and addition of the substrate glucose an efficient bioelectrocatalysis is demonstrated. Depending on the choice of the sulfonated polyanilline mediatorless bioelectrocatalysis starts at low potentials; no large overpotential is needed to drive the reaction. Thus, the electrospun conductive immobilization matrix acts here as a transducing element, representing a promising strategy to use 3D polymeric scaffolds as wiring agents for active enzymes. In addition, the mild and well reproducible fabrication process and the active role of the polymer film in withdrawing electrons from the reduced PQQ-GDH lead to a system with high stability. This could provide access to a larger group of enzymes for bioelectrochemical applications including biosensors and biofuel cells.

Carbon nanotubes (CNTs) arranged in 3 dimensional structures represent an interesting material for the development of biocatalytic electrodes. Due to their architecture they can provide docking places for enzymes and after modification of the surface properties often a direct electrochemistry can be observed. The direct electron transfer where the catalytic starts near the E0 of the enzymes redox center can avoid a loss of in cell potential and allows the development of efficient enzymatic biofuel cells (EBFC). Also the membrane-less construction of the EBFCs is advantageous for high power output. With this respect the pyrroloquinoline quinone dependent glucose dehydrogenase ((PQQ) GDH) is an interesting enzyme since it is insensitive towards oxygen which is the terminal electron acceptor at the cathode. Here two types of carbon nanotubes materials - bucky paper (BP) and vertically aligned carbon nanotubes (vaCNTs) - are used for the development of glucose/oxygen biofuel cells. For the anode development these materials are modified with poly(3-aminobenzoic acid-co-2-methoxyaniline-5-sulfonic) acid (PABMSA) for covalent coupling of the glucose oxidizing (PQQ) GDH. The cathode is based on the oxygen reducing Bilirubin oxidase (BOD) which is covalently coupled to PQQ modified BP and vaCNTs electrodes. For the electrochemical characterisation of the individual electrodes voltammetric measurements are performed. The voltammograms for the different anode preparations show that the modification of both carbon nanotube materials with an aniline-based polymer film (PABMSA) and covalent enzyme coupling result in an direct enzyme-electrode contact. The influence of the polymer concentration during the electrode preparation and the impact of the buffer composition on the current density are investigated. Both electrode materials show the highest current density in 100 mM citrate phosphate (CiP) buffer containing 10 mM glucose and applying 5 mg/ml PABMSA for CNTs modification. For the BP-based anode current densities up to 0.75 mA/cm2 can be detected while electrodes made of vaCNTs reveal a maximum current density of 1.3 mA/cm2 at +0.1 V vs. Ag/AgCl. The cathode construction with PQQ as interlayer and a covalent attachment of the BOD to the carboxylic groups shows the highest electrocatalytic activity under air saturated conditions – for bucky paper about 1 mA/cm2 at 0.1 V vs. Ag/AgCl. Applying vaCNTs for the BOD-cathode development a local maximum current of 1.3 mA/cm2 and a steady-state catalytic current of 0.55 mA/cm2 at +0.1 V vs. Ag/AgCl can be obtained. A combination of the BP-based (PQQ)GDH/PABMSA and BOD/PQQ electrodes in a biofuel cell application achieves a power output of 107 µW/cm2 at a cell potential of 490 mV. The same modification procedures and enzymes applied in a vaCNTs fuel cell lead to a power density of 122 µW/cm2 at cell potential of 540 mV. The separate evaluation of both carbon nanotubes based materials reveal a better stability of the vaCNTs-based enzyme electrodes.

A nanohybrid consisting of poly(3-aminobenzenesulfonic acid-co-aniline) and multiwalled carbon nanotubes [MWCNT-P(ABS-A)]) on a gold electrode was used to immobilize the hexameric tyrosine-coordinated heme protein (HTHP). The enzyme showed direct electron transfer between the heme group of the protein and the nanostructured surface. Desorption of the noncovalently bound heme from the protein could be excluded by control measurements with adsorbed hemin on aminohexanthiol-modified electrodes. The nanostructuring and the optimised charge characteristics resulted in a higher protein coverage as compared with MUA/MU modified electrodes. The adsorbed enzyme shows catalytic activity for the cathodic H2O2 reduction and oxidation of NADH.

A feasible approach to construct multilayer films of sulfonated polyanilines - PMSA1 and PABMSA1 containing different ratios of aniline, 2-methoxyaniline-5-sulfonic acid (MAS) and 3-aminobenzoic acid (AB), with the entrapped redox enzyme pyrroloquinoline quinone-dependent glucose dehydrogenase (PQQ-GDH) on Au and ITO electrode surfaces, is described. The formation of layers has been followed and confirmed by electrochemical impedance spectroscopy (EIS), which demonstrates that the multilayer assembly can be achieved in a progressive and uniform manner. The gold and ITO electrodes subsequently modified with PMSA1:PQQ-GDH and PABMSA1 films are studied by cyclic voltammetry (CV) and UV-Vis spectroscopy which show a significant direct bioelectrocatalytical response to the oxidation of the substrate glucose without any additional mediator. This response correlates linearly with the number of deposited layers. Furthermore, the constructed polymer/enzyme multilayer system exhibits a rather good long-term stability, since the catalytic current response is maintained for more than 60% of the initial value even after two weeks of storage. This verifies that a productive interaction of the enzyme embedded in the film of substituted polyaniline can be used as a basis for the construction of bioelectronic units, which are useful as indicators for processes liberating glucose and allowing optical and electrochemical transduction.

Sulfonierte Polyaniline erwiesen sich bereits als geeignete Polymere für den Aufbau von Biosensoren. Aus diesem Grund setzten wir unterschiedlich substituierte Polymerformen für die Untersuchungen der direkten Elektronenübertragung zum Redoxenzym PQQ-GDH (Pyrrolochinolinchinon-abhängige Glukosedehydrogenase) ein. Dafür wurden zuerst neue Copolymere synthetisiert. Als Basis für die Synthesen wurden 2-Methoxyanilin-5-Sulfonsäure (MAS), 3-Aminobenzensulfonsäure (ABS), 3-Aminobenzoesäure (AB) und Anilin (AN) ausgewählt und deren Verhältnisse variiert. Alle Copolymere wurden hinsichtlich der direkten Reaktion mit PQQ-GDH untersucht. Diese Wechselwirkung wurde zunächst in Lösung, anschließend auch auf Elektroden beobachtet. Die Ergebnisse zeigen, dass nur die aus MAS- und AN-Einheiten bestehenden Copolymere in der Lage sind, mit dem Enzym in Lösung direkt zu interagieren, was wahrscheinlich dem Emeraldin Salz (ES) Redoxzustand des Polymers zuzuschreiben ist. Immobilisiert man die Polymere und das Enzym auf Kohlenstoffnanoröhrenbasierten Elektroden, generiert man direkte Bioelektrokatalyse auch im Falle der aus ABS/AB- und MAS/AB-Einheiten bestehenden Copolymere, die sich nach der Synthese im Pernigranilin Base (PB) Redoxzustand befinden. Im Gegensatz zur Situation in Lösung kann auf Elektroden das Potential zusätzlich genutzt werden, um Elektronen vom Enzym auf das Polymer zu übertragen. Solche Polymerbasierten Enzymelektroden besitzen Anwendungspotential in der Sensorik, aber auch in Biobrennstoffzellen.

Polymer-multiwalled carbon nanotube (MWCNT) nanohybrids, which differ in surface charge have been synthesized to study the bioelectrocatalysis of adsorbed cellobiose dehydrogenase (CDH) from Phanerochaete sordida on gold electrodes. To obtain negatively charged nanohybrids, poly(3-amino-4-methoxybenzoic acid-co-aniline) (P(AMB-A)) was covalently linked to the surface of MWCNTs while modification with p-phenylenediamine (PDA) converted the COOH-groups to positively charged amino groups. Fourier transform infrared spectroscopy (FTIR) measurements verified the p-phenylenediamine (PDA) modification of the polymer-CNT nanohybrids. The positively charged nanohybrid MWCNT-P(AMB-A)-PDA promoted direct electron transfer (DET) of CDH to the electrode and bioelectrocatalysis of lactose was observed. Amperometric measurements gave an electrochemical response with KMapp = 8.89 mM and a current density of 410 nA/cm2 (15 mM lactose). The catalytic response was tested at pH 3.5 and 4.5. Interference by ascorbic acid was not observed. The study proves that DET between the MWCNT-P(AMB-A)-PDA nanohybrids and CDH is efficient and allows the sensorial detection of lactose.

The development of a new surface architecture for the efficient direct electron transfer of positively charged redox proteins is presented. For this reason different kinds of polyaniline terpolymers consisting of aminobenzoic acid (AB), aminobenzenesulfonic acid (ABS) and aniline (A) with different monomer ratios were synthesized. The P(AB-ABS-A) were grafted to the surface of multiwalled carbon nanotubes (MWCNTs). FTIR measurements prove the covalent binding to the carboxylic groups of the MWCNTs while conductivity tests show an increase in the conductivity of the nanohybrid in comparison to the polymers. The [MWCNT-P(AB-ABS-A)] nanohybrids were used for the immobilization of redox active cytochrome c (cyt.c). The positively charged protein can electrostatically interact with the negatively charged nanohybrid. Cyclic voltammetry (CV) shows an increase in the protein loading on [MWCNT-P(AB-ABS-A)] coupled to cysteamine modified gold electrodes in comparison to non-grafted MWCNTs. A further increase in the sulfonation degree of P(AB-ABS-A) leads to an enhanced current output of the modified electrodes. The redox activity of the polymer decreases after the immobilization of the cyt.c on the nanohybrid. For the first time polymers covalently grafted to the surface of MWCNTs are used in a biosensor.