3D-Printed Scanning-Probe Microscopes with Integrated Optical Actuation and Read-Out

Scanning‐probe microscopy (SPM) is the method of choice for high‐resolution imaging of surfaces in science and industry. However, SPM systems are still considered as rather complex and costly scientific instruments, realized by delicate combinations of microscopic cantilevers, nanoscopic tips, and macroscopic read‐out units that require high‐precision alignment prior to use. This study introduces a concept of ultra‐compact SPM engines that combine cantilevers, tips, and a wide variety of actuator and read‐out elements into one single monolithic structure. The devices are fabricated by multiphoton laser lithography as it is a particularly flexible and accurate additive nanofabrication technique. The resulting SPM engines are operated by optical actuation and read‐out without manual alignment of individual components. The viability of the concept is demonstrated in a series of experiments that range from atomic‐force microscopy engines offering atomic step height resolution, their operation in fluids, and to 3D printed scanning near‐field optical microscopy. The presented approach is amenable to wafer‐scale mass fabrication of SPM arrays and capable to unlock a wide range of novel applications that are inaccessible by current approaches to build SPMs

Slice-Less Optical Arbitrary Waveform Measurement (OAWM) in a Bandwidth of More than 600 GHz Using Soliton Microcombs

We propose and demonstrate a novel scheme for optical arbitrary waveform measurement (OAWM) that exploits chip-scale Kerr soliton combs as highly scalable multiwavelength local oscillators (LO) for ultra-broadband full-field waveform acquisition. In contrast to earlier concepts, our approach does not require any optical slicing filters and thus lends itself to efficient implementation on state-of-the-art high-index-contrast integration platforms such as silicon photonics. The scheme allows to measure truly arbitrary waveforms with high accuracy, based on a dedicated system model which is calibrated by means of a femtosecond laser with known pulse shape. We demonstrated the viability of the approach in a proof-of-concept experiment by capturing an optical waveform that contains multiple 16 QAM and 64 QAM wavelength-division multiplexed (WDM) data signals with symbol rates of up to 80 GBd, reaching overall line rates of up to 1.92 Tbit/s within an optical acquisition bandwidth of 610 GHz. To the best of our knowledge, this is the highest bandwidth that has so far been demonstrated in an OAWM experiment

Optical properties of highly nonlinear silicon-organic hybrid (SOH) waveguide geometries

Geometry, nonlinearity, dispersion and two-photon absorption figure of merit of three basic silicon-organic hybrid waveguide designs are compared. Four-wave mixing and heterodyne pump-probe measurements show that all designs achieve high nonlinearities. The fundamental limitation of two-photon absorption in silicon is overcome using silicon-organic hybrid integration, with a five-fold improvement for the figure of merit (FOM). The value of FOM = 2.19 measured for silicon-compatible nonlinear slot waveguides is the highest value published. (C) 2009 Optical Society of Americ

Freeform terahertz structures fabricated by multi-photon lithography and metal coating

Direct-write multi-photon laser lithography (MPL) combines highest resolution on the nanoscale with essentially unlimited 3D design freedom. Over the previous years, the groundbreaking potential of this technique has been demonstrated in various application fields, including micromechanics, material sciences, microfluidics, life sciences as well as photonics, where in-situ printed optical coupling elements offer new perspectives for package-level system integration. However, millimeter-wave (mmW) and terahertz (THz) devices could not yet leverage the unique strengths of MPL, even though the underlying devices and structures could also greatly benefit from 3D freeform microfabrication. One of the key challenges in this context is the fact that functional mmW and THz structures require materials with high electrical conductivity and low dielectric losses, which are not amenable to structuring by multi-photon polymerization. In this work, we introduce and experimentally demonstrate a novel approach that allows to leverage MPL for fabricating high-performance mmW and THz structures with hitherto unachieved functionalities. Our concept exploits in-situ printed polymer templates that are selectively coated through highly directive metal deposition techniques in combination with precisely aligned 3D-printed shadowing structures. The resulting metal-coated freeform structures offer high surface quality in combination with low dielectric losses and conductivities comparable to bulk material values, while lending themselves to fabrication on planar mmW/THz circuits. We experimentally show the viability of our concept by demonstrating a series of functional THz structures such as THz interconnects, probe tips, and suspended antennas. We believe that our approach offers disruptive potential in the field of mmW and THz technology and may unlock an entirely new realm of laser-based 3D manufacturing

Quercetin Protects Primary Human Osteoblasts Exposed to Cigarette Smoke through Activation of the Antioxidative Enzymes HO-1 and SOD-1

Smokers frequently suffer from impaired fracture healing often due to poor bone quality and stability. Cigarette smoking harms bone cells and their homeostasis by increased formation of reactive oxygen species (ROS). The aim of this study was to investigate whether Quercetin, a naturally occurring antioxidant, can protect osteoblasts from the toxic effects of smoking. Human osteoblasts exposed to cigarette smoke medium (CSM) rapidly produced ROS and their viability decreased concentration- and time-dependently. Co-, pre- and postincubation with Quercetin dose-dependently improved their viability. Quercetin increased the expression of the anti-oxidative enzymes heme-oxygenase- (HO-) 1 and superoxide-dismutase- (SOD-) 1. Inhibiting HO-1 activity abolished the protective effect of Quercetin. Our results demonstrate that CSM damages human osteoblasts by accumulation of ROS. Quercetin can diminish this damage by scavenging the radicals and by upregulating the expression of HO-1 and SOD-1. Thus, a dietary supplementation with Quercetin could improve bone matter, stability and even fracture healing in smokers

Wireless THz link with optoelectronic transmitter and receiver

Photonics might play a key role in future wireless communication systems that operate at terahertz (THz) carrier frequencies. A prime example is the generation of THz data streams by mixing optical signals in high-speed photodetectors. Over previous years, this concept has enabled a series of wireless transmission experiments at record-high data rates. Reception of THz signals in these experiments, however, still relied on electronic circuits. In this paper, we show that wireless THz receivers can also greatly benefit from optoelectronic signal processing techniques, in particular when carrier frequencies beyond 0.1 THz and wideband tunability over more than an octave is required. Our approach relies on a high-speed photoconductor and a photonic local oscillator for optoelectronic downconversion of THz data signals to an intermediate frequency band that is easily accessible by conventional microelectronics. By tuning the frequency of the photonic local oscillator, we can cover a wide range of carrier frequencies between 0.03 and 0.34 THz. We demonstrate line rates of up to 10 Gbit/s on a single channel and up to 30 Gbit/s on multiple channels transmitted over a distance of 58 m. To the best of our knowledge, our experiments represent the first demonstration of a THz communication link that exploits optoelectronic signal processing techniques both at the transmitter and the receiver

Wireless THz link with optoelectronic transmitter and receiver

Photonics might play a key role in future wireless communication systems that operate at terahertz (THz) carrier frequencies. A prime example is the generation of THz data streams by mixing optical signals in high-speed photodetectors. Over previous years, this concept has enabled a series of wireless transmission experiments at record-high data rates. Reception of THz signals in these experiments, however, still relied on electronic circuits. In this paper, we show that wireless THz receivers can also greatly benefit from optoelectronic signal processing techniques, in particular when carrier frequencies beyond 0.1 THz and wideband tunability over more than an octave is required. Our approach relies on a high-speed photoconductor and a photonic local oscillator for optoelectronic downconversion of THz data signals to an intermediate frequency band that is easily accessible by conventional microelectronics. By tuning the frequency of the photonic local oscillator, we can cover a wide range of carrier frequencies between 0.03 and 0.34 THz. We demonstrate line rates of up to 10 Gbit/s on a single channel and up to 30 Gbit/s on multiple channels transmitted over a distance of 58 m. To the best of our knowledge, our experiments represent the first demonstration of a THz communication link that exploits optoelectronic signal processing techniques both at the transmitter and the receiver

Brain Deletion of Insulin Receptor Substrate 2 Disrupts Hippocampal Synaptic Plasticity and Metaplasticity

Diabetes mellitus is associated with cognitive deficits and an increased risk of dementia, particularly in the elderly. These deficits and the corresponding neurophysiological structural and functional alterations are linked to both metabolic and vascular changes, related to chronic hyperglycaemia, but probably also defects in insulin action in the brain. To elucidate the specific role of brain insulin signalling in neuronal functions that are relevant for cognitive processes we have investigated the behaviour of neurons and synaptic plasticity in the hippocampus of mice lacking the insulin receptor substrate protein 2 (IRS-2)