For increasing the data rates in digital communication networks, high-speed signal generation is required. To generate these high-speed signals, electronics-based arbitrary waveform generators (AWGs) are the key components. However, most of the commercially available high-speed electronic AWGs are subject to linearity and resolution limitations. Photonics-based AWG, instead, might offer high bandwidth with better resolution and phase noise. Several photonic techniques have been proposed in recent years but with increased system complexity and limited dynamic range. We have recently proposed a photonics based architecture for high-speed arbitrary waveform generation using low-speed electronics, which is based on optical Nyquist pulse sequences and time-domain interleaving to obtain high-quality waveforms. Within this system, a single laser source is split into N branches. A Nyquist pulse sequence is generated by an integrated modulator driven by a single electrical sinusoidal frequency in each branch. Subsequently, they are modulated and multiplexed to obtain the targeted waveforms. The time delay between the pulse sequences is realized by a simple electrical phase shift of the sinusoidal driving signal. Here, a theoretical validation for the N channel system is presented along with simulation and experimental results for a three-branch photonic AWG. Using an integrated silicon Mach-Zehnder modulator saw-tooths, sinusoidal and some bandwidth-limited analog waveforms are generated. With available 100 GHz integrated modulators, the maximum possible sampling rate of 300 GS/s can be achieved. The mathematical proof validates that this simple concept can generate bandwidth limited user-defined waveforms with very high precision.
Semiconductor metal oxide (SMO) sensors have been utilized as oxygen sensors in industry and research for decades. Oxygen molecules adsorb to the SMO surface which leads to a measurable increase of resistivity [1]. Those sensors are valued for their high accuracy, but they operate at high temperatures [2]. Therefore, heating circuits inside the sensors are required, increasing size and power consumption of the sensors. This paper investigates the applicability of zinc oxide nanoparticle (ZnO) structures as low-cost oxygen detectors for measurements at room temperature. The main advantage of ZnO nanoparticle-based electronics is their low production cost since the nanoparticles can be deposited by cheap process techniques like spray-coating, spin-coating, inkjet-printing or the doctor blade process. Furthermore, they provide a high surface area to volume ratio which leads to higher sensitivity to oxygen. The most critical disadvantage is the high inhomogeneity of particle size and shape which causes nanoporous ZnO layers with low conductivity and nonuniform electrical characteristics. Therefore, gate structures were integrated into the sensors, so that the ZnO nanoparticle conductivity can be adjusted by applying a gate voltage. ZnO nanoparticle transistors with different electrode geometries and channel length were manufactured and analyzed. In different oxygen concentrations ZnO layer resistance, dependent on the applied gate voltage, was measured. Based on the results, a new layout for low-cost sensors without heating structures was developed. Since this work is part of a project, in which a low-cost water quality sensor is developed, the sensors are designed for oxygen concentration measurements in liquids as well.
Inkjet-printing supports environmentally friendly manufacturing of printed electronics and enables rapid prototyping with low material waste. In this work, inkjet-printed conductive tracks on ethyl 2-cyanoacrylate (superglue) is compared to tracks printed on paper. This work will provide solutions for disposable biosensing, where the biocompatibility of versatile superglue is important. The emphasis throughout the work is on developing a biocompatible device. Dog-bone structures with different line widths were printed on paper and superglue, providing comparative results obtained from dimensional and electrical characterisation. On average the tracks printed on superglue have a 2.6 times higher resistivity than those printed on paper, but are acceptable for printed electronics networks. When considering a lumped component ac model, the 500 μm tracks on superglue have a series inductance of 2.6 nH, while the 4-point Kelvin probe characterisation of the 100 μm and 250 μm tracks printed on superglue show a capacitive equivalent impedance with capacitance values of 2.8 μF and 2.6 μF respectively. The 100 μm, 250 μm and 500 μm tracks printed on paper have inductance values of 1.20 nH, 11.30 nH and 14.8 nH, respectively. All printed tracks have linear frequency operational ranges larger than 1 MHz. A biocompatibility test was performed with Escherichia coli (E. coli) O157:H7. The silver nanoparticle ink proved to be antibacterial, while paper, superglue and gold nanoparticle ink was biocompatible. These results provide information assisting the design process for bio applications that require conformal and multi-substrate printing.
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