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•When switching from natalizumab to fingolimod a washout period of 4 weeks is safe.•Number of relapses before switching is associated with the hazard of relapse.•A shorter washout reduces the hazard of relapse.•A shorter washout reduces the risk of disease reactivation over two years.

Long-wavelength VCSELs with emission wavelengths beyond 1.3 m have seen a remarkable progress over the last decade. This success has been accomplished by using highly advanced device concepts which effectively overcome the fundamental technological drawbacks related with long-wavelength VCSELs such as inferior thermal properties and allow for the realization of lasers with striking device performance. In this presentation, we will give an overview on the state of the technology for long-wavelength VCSELs in conjunction with their opportunities in applications for optical sensing. While VCSELs based on InP are limited to maximum emission wavelengths around 2.3 m, even longer wavelengths up to the mid-infrared range beyond 3 m can be achieved with VCSELs based on GaSb. For near-infrared InP-based VCSELs, the output characteristics include sub-mA threshold currents, up to several milliwatts of singlemode output power and ultralow power consumption. New concepts for widely tunable VCSELs with tuning ranges up to 100 nm independent from the material system for the active region are also presented. Today, optical sensing by Tunable Diode Laser Spectroscopy is a fast emerging market. Gas sensing systems are used for a wide range of applications such as industrial process control, environmental monitoring and safety applications. With their inherent and compared to other laser types superior properties including enhanced current tuning rates, wavelength tuning ranges, modulation frequencies and power consumption, long-wavelength VCSELs are regarded as key components for TDLS applications.

We report the investigation of the state of polarization (SOP) of a tunable vertical-cavity surface-emitting laser (VCSEL) operating near 850 nm with a mode-hop free single-mode tuning range of about 12 nm and an amplitude modulation bandwidth of about 5 GHz. In addition, the effect of a sub-wavelength grating on the device and its influence on the polarization stability and polarization switching has been investigated. The VCSEL with an integrated sub-wavelength grating shows a stable SOP with a polarization mode suppression ratio (PMSR) more than 35 dB during the tuning.

We present a micro electro-mechanical system (MEMS) tunable vertical-cavity surface-emitting laser (VCSEL) emitting around 1.55 m with single-mode output power of >2.5mW and high side-mode suppression-ratio (SMSR) of >50dB over the entire tuning range of >50nm. The small-signal modulation technique (S21) has been used to study intrinsic and parasitic influences on the modulation response of the device. Additionally, the static characteristics as well as electrical and thermal design of the device are discussed with respect to its high-speed modulation behavior. The tunable laser shows 3-dB direct modulation frequencies above 6.4 GHz.

In this paper we describe the design and performance of nonlinear quantum cascade laser sources for near-infrared and terahertz applications. Our devices are based on monolithically integrated mid-infrared quantum cascade lasers and passive nonlinear structures which provide a giant nonlinear response for the pumping frequency. Such design concept can be applied for both short-wavelength and long-wavelength generation. In our work, short-wavelength devices were based on the concept of second-harmonic generation whereas long-wavelength devices utilized difference-frequency generation. With this approach we demonstrate room-temperature operation down to 2.7 m for near-infrared devices and up to 70 m at 210 K for terahertz devices. The performance of our nonlinear devices is very sensitive to the resonance condition for the pump and nonlinearity. We demonstrate that, once resonant, nonlinear powers in the mW range are available.

Injectorless quantum cascade lasers are lately getting more and more into focus of research, as they promise lower threshold current densities and higher output powers and efficiencies. Although the research on them started seven years later in 2001 and was less intensive, they have achieved much lower threshold current densities with 0.45 kA/cm2at 300 K compared to injectorbased devices. Additionally injectorless devices reached efficiencies and output powers in the important wavelength range between 8 and 12 m comparable to best performing injectorbased devices. With 2 W per facet and an overall efficiency of 7 % around 9 m, they show a strong potential regarding possible applications.

Bei der Konversion von lignocellulosehaltigen Materialien entstehen neben den gewünschten löslichen fermentierbaren Zuckern oftmals störende, für Mikroorganismen toxische Abbauprodukte wie etwa organische Säuren, Furane oder phenolische Substanzen. Letztere verbleiben nach einer Evaporation und Aufkonzentrierung in der zuckerhaltigen Lösung. Im vorliegenden Beitrag wird das Potenzial einer enzymkatalysierten Detoxifikation dieser phenolischen Substanzen aufgezeigt. Darüber hinaus erfolgt eine reaktionstechnische Beschreibung der Laccasekatalysierten Konversion der phenolischen Komponenten.

Objectives Virtual reality (VR) opens a variety of therapeutic options to improve symptom burden in patients with advanced disease. Until to date, only few studies have evaluated the use of VR therapy in the context of palliative care. This case series aims to evaluate the feasibility and acceptability of VR therapy in a population of palliative care patients.Methods In this single-site case series, we report on six palliative care patients undergoing VR therapy. The VR therapy consisted of a one-time session ranging between 20 to 60 minutes depending on the patient's needs and the content chosen for the VR sessions. A semi-structured survey was conducted and the Edmonton Symptom Assessment System (ESAS) and the Distress Thermometer were performed pre- and post-intervention.Results Overall, VR therapy was well accepted by all patients. Five out of six patients reported having appreciated VR therapy. There were individual differences of perceived effects using VR therapy. The semi-structured survey revealed that some patients felt a temporary detachment from their body and that patients were able to experience the VR session as a break from omnipresent worries and the hospital environment (“I completely forgot where I am”). There was a considerable reduction in the total ESAS score post-treatment (T0 ESASTot= 27.2; T1 ESASTot= 18.8) and a slightly reduction in distress (T0 DTTot= 4.4; T1 DTTot= 3.8). However, two patients were more tired after the intervention. Significance of Results: Our preliminary results demonstrate that VR therapy is acceptable, feasible and safe for use within a palliative care population and appears to be a viable treatment option. Clinical trials are both warranted and necessary to confirm any therapeutic effects of VR therapy, as is the need to tailor VR systems better for use in palliative care settings.

Tin has been introduced into polycrystalline lead iodide during solution growth of thin films. Electrical characterization current vs. voltage measurements as a function of the temperature and thermally stimulated current experiments demonstrates that tin introduces a deep donor level in the PbI2bandgap and compensates the native acceptor defects of lead iodide. © 2008 WILEYVCH Verlag GmbH & Co. KGaA, Weinheim

We present a micromechanically tunable long-wavelength vertical-cavity surface-emitting laser with a buried tunnel junction aperture and a stable half-symmetric cavity for full mode control. The conjunction of the active part 'half-VCSEL' and the curved MEMS-mirror in a two-chip assembly enables high output power singlemode emission exceeding 1 mW. Electrothermal actuation of the micromechanical chip allows us to extend the single wavelength performance to a continuously tunable, selectively wavelength-addressable spectrum of 28 nm. The concave curvature and the resulting long air-gap cavity are designed to favour the resonance of the fundamental mode, i.e. to match the phase front predicted by Gaussian beam theory corresponding to the aperture diameter of 10 µm. The spatial beam profile of the MEMS-VCSEL is measured in the far-field and compared with a conventional VCSEL with a fixed plane top mirror. The polarization is controlled by a dominating mirror asymmetry. High sidemode suppression over the whole tuning range with respect to both the transverse modes (>40 dB) and the polarization modes (>30 dB) is demonstrated.

Hydrogen-terminated diamond surfaces are very attractive for devices based on surface electronics. The hole channel that governs the surface conductivity and the simplicity of the surface patterning are key features which allow a large flexibility for device design. In-plane gate field effect transistors have been fabricated with the conductive channel separated from the ohmic gate contacts by insulating thin lines, obtained by using a combination of electron beam lithography with surface oxidation. Depletion regions spreading from the highly resistive oxidized lines which separate the channel and gate regions can be controlled by applying a voltage to both lateral gate contacts. A wire structure has been designed in such a way that the gate voltage effectively modulates the conductance of the channel. The channel modulation is discussed in terms of a quasi two-dimensional surface carrier density. The effect of surface defects on the transistor properties has also been investigated. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Thermally stimulated current measurements have been performed on lead iodide layers deposited by vacuum evaporation. In addition to a broad TSC band extending from 120–140 K up to 180–200 K, several peaks have been observed close to 100 K, 170 K, 210 K and 270 K. Comparison of the results with data obtained on PbI2 samples fabricated by different methods shows a behaviour somewhat different from polycrystalline layers grown in solution and from single crystals. The total concentration of defects reaches 5 × 10¹⁴–10¹⁵ cm^–3. It is at least one order of magnitude higher than in solution growth layers. It can be noticed that the defect attributed to the lead vacancy is found in evaporated layers as well as in melt grown single crystals while it is not present in solution growth layers.

The highly conductive p-type surface layer that can be induced in diamond by hydrogen termination is very attractive for electrical applications and in particular for the design of in-plane devices. In this paper we will present our work on the characterization of sub-micron in-plane transistors. Two different approaches have been analyzed for the design of the transistor gate. First of all the properties of Al gates on H-terminated diamond will be discussed, focusing on their capacitance–voltage characteristics. As a result of this study it will be shown how the p-type surface layers in H-terminated diamond behaves like a two-dimensional system. However, due to the poor channel control by the Al gates another approach was followed. The gate region is separated from the channel by a thin oxidized line. The channel current is controlled by the voltage applied to the gate, which varies the space charge region width that is formed at the oxidized line. Sub-micron gate structures were generated by using e-beam lithography and a plasma oxidation treatment. The transistor characteristics of the in-plane diamond structures are presented in this paper.

A high-reflection coating for 5.5 4;µm strain-compensated InGaAs/InAlAs quantum cascade lasers is described. Using a high-reflection coating on both facets of a laser cavity, a threshold current density of 0.5 4;kA/cm2 was observed at liquid-nitrogen temperature, whereas for an uncoated structure of comparable length the threshold current density was 1 4;kA/cm2. Laser action for a 2.1 4;mm long and 30 4;µm wide device with coated facets was achieved in pulsed mode up to the record high temperature of 470 4;K. A 2.5 4;mm long and 30 4;µm wide device with uncoated facets shows lasing action up to 440 4;K.

Thermally stimulated current measurements have been performed on polycrystalline layers of lead iodide grown from solution. Several TSC peaks or bands have been observed at temperatures of 100 K, 195–220 K, 230–240 K and 270–300 K. Comparison with PbI2single crystal shows that the polycrystalline structure of the material introduces additional defects. In contrast the defect currently found in single crystal and attributed to the lead vacancy has not been clearly evidenced in the polycrystalline layers. The position and relative intensity of the peaks can be modified by Ag doping and thermal annealing. On the other hand, only small differences resulting from the anisotropy of the material have been observed depending on the orientation of the electric field with regards to the grains orientation.

Thermally stimulated current measurements have been performed on polycrystalline layers of lead iodide grown from solution. Several TSC peaks or bands have been observed at temperatures of 100 K, 195–220 K, 230–240 K and 270–300 K. Comparison with PbI$_2$ single crystal shows that the polycrystalline structure of the material introduces additional defects. In contrast the defect currently found in single crystal and attributed to the lead vacancy has not been clearly evidenced in the polycrystalline layers. The position and relative intensity of the peaks can be modified by Ag doping and thermal annealing. On the other hand, only small differences resulting from the anisotropy of the material have been observed depending on the orientation of the electric field with regards to the grains orientation.

In this paper, we investigate the dynamics of amplified spontaneous emission (ASE) in self-assembled InAs/GaAs quantum dots. Upconversion is used to time-resolve the emission from an edge-emitting waveguide structure at room temperature which is excited by short laser pulses in a stripe geometry. We demonstrate that increases in both the electron–hole pair density and the stripe length significantly decrease the emission decay time from around 2 ns, corresponding to spontaneous emission, to about 0.9 ns, corresponding to stimulated emission or ASE. A simulation of the ASE process in this geometry is in agreement with our experimental results.

The conventional ellipsometry can be applied to determine the optical properties of anisotropic materials only if the measurements are made for in-plane uniaxial anisotropy of the bulk sample with the optic axis parallel or perpendicular to the plane of incidence. For arbitrarily oriented anisotropic materials, the generalized ellipsometry method should be used. The generalized fixed polarizer, rotating-polarizer and fixed analyzer spectroscopic ellipsometry was used. The method is experimentally verified for uniaxial mercuric iodide (HgI2). The normalized Jones matrix and the complex optical functions are extracted from the measured Fourier coefficients at different sample orientations and different polarizer and analyzer angles P and A.

Out of the eight enzymes involved in the biosynthesis of the isoquinoline alkaloid berberine, at least, two enzymes, berberine bridge enzyme and (S)-tetrahydroprotoberberine oxidase, are exclusively located in a vesicle with a specific gravity of ?=1.14 g·cm-3 as shown by direct enzymatic assay as well as immunoelectrophoresis. Electronmicroscopic examination of the enzyme-containing particulate preparation from Berberis wilsoniae var. subcaulialata cultured cells demonstrated that it is composed mainly of membranous vesicles. The protein composition of this preparation reveals the presence of only about 20 separable proteins, of which two major ones are berberine bridge enzyme and (S)-tetrahydroprotoberberine oxidase. Incubation of these vesicles with the substrate (S)-reticuline in the presence and absence of S-adenosyl-l-methionine leads to the formation of a red product which was identified as dehydroscoulerine. If the cytoplasmic enzyme S-adenosyl-l-methionine:(S)-scoulerine-9-O-methyltransferase is added to the vesicle preparation in the presence of (S)-reticuline and S-adenosyl-l-methionine, not dehydroscoulerine but columbamine, the immediate precursor of berberine is formed. Some of the quaternary alkaloids are located inside the vesicles; fusion of these vesicles leads to vacuoles containing the quaternary alkaloids. These vesicles are the first highly specific and unique compartment serving only alkaloid biosynthesis; they are found in members of four different plant families and in cell cultures as well as in differentiated tissue.

A newly developed stripe-geometry injection laser is presented with built-in passive waveguiding produced by an effective refractive-index step between active stripe and adjoining regions. In contrast with the similar CSP laser, however, confinement of the lasing mode is achieved by metal reflection instead of excess absorption loss outside the active stripe. A model for this type of injection laser is established, and a numerical analysis of the waveguiding mechanism is performed. As a result, design curves are obtained that directly determine the technological parameters required for diode preparation.

Suspension cultures of Berberis wilsoniae var. subcaulialata and B. aggregata are a useful source for the detection, partial purification and characterization of a new enzyme which specifically transfers the methyl group from (S)-adenosyl-L-methionine to the 2-OH-position of columbamine, thus producing palmatine. The enzyme was enriched approx. 30-fold; it is situated in a vesicle with the density ?=1.14, has a pH-optimum of 8.9, a molecular weight of 52 kD and shows a high degree of substrate specificity.

We demonstrate a self-starting Kerr-lens mode-locked (KLM) Yb:YAG thin-disk oscillator operating in the regime of positive intracavity group-delay dispersion (GDD). It delivers 1.7 ps pulses at an average power of 17 W and a repetition rate of 40 MHz. Dispersive mirrors compress the pulses to a duration of 190 fs (assuming sech^2 shape; Fourier limit: 150 fs) at an average power level of 11 W. To our knowledge, this is the first KLM thin-disk oscillator with positive GDD. Output powers of up to 30 W were achieved with an increased output coupler transmission and intracavity GDD. We demonstrate increase of the pulse energy with increasing positive intracavity GDD, limited by difficulties in initiating mode-locking.

We demonstrate a power-scalable Kerr-lens mode-locked Yb:YAG thin-disk oscillator. It delivers 200 fs pulses at an average power of 17 W and a repetition rate of 40 MHz. At an increased (180 W) pump power level, the laser produces 270 fs 1.1 μJ pulses at an average power of 45 W (optical-to-optical efficiency of 25%). Semiconductor-saturable-absorber-mirror-assisted Kerr-lens mode locking (KLM) and pure KLM with a hard aperture show similar performance. To our knowledge, these are the shortest pulses achieved from a mode-locked Yb:YAG disk oscillator and this is the first demonstration of a Kerr-lens mode-locked thin-disk laser.

The authors have fabricated InGaAs-InGaAlAs-InP strained quantum well lasers with wavelengths as long as 2208 nm using solid-source molecular-beam epitaxy. A continuous-wave threshold current density of 370 A/cm2 at 20°C and a characteristic temperature of 53 K have been achieved.

A 1.5 µm vertical-cavity surface-emitting laser operating with high efficiency under continous wave conditions at room temperature is demonstrated with threshold current and voltage below 1 mA and 1 V, respectively. The singlemode emission spectrum exhibits stable linear polarisation with a sidemode suppression ratio of 30 dB.