Silicon-Organic Hybrid (SOH) and Plasmonic-Organic Hybrid (POH) integration

Silicon photonics offers tremendous potential for inexpensive high-yield photonic-electronic integration. Besides conventional dielectric waveguides, plasmonic structures can also be efficiently realized on the silicon photonic platform, reducing device footprint by more than an order of magnitude. However, nei-ther silicon nor metals exhibit appreciable second-order optical nonlinearities, thereby making efficient electro-optic modulators challenging to realize. These deficiencies can be overcome by the concepts of silicon-organic hybrid (SOH) and plasmonic-organic hybrid integration, which combine SOI waveguides and plasmonic nanostructures with organic electro-optic cladding materials

Capacitively Coupled Silicon-Organic Hybrid Modulator for 200 Gbit/s PAM-4 Signaling

We demonstrate capacitively coupled silicon-organic hybrid (SOH) modulator with a π-voltage-length product of 1.3 V mm and 3 dB EO bandwidth exceeding 65 GHz. The modulator is used for 200 Gbit/s (100 GBd) PAM-4 signaling

Selective Laser Melting of High-strength, Low-modulus Ti–35Nb–7Zr–5Ta Alloy

The state-of-the-art alloys for load-bearing implant applications lack the necessary functional attributes and are largely a compromise between biocompatibility and mechanical properties. While commercial alloys pose long-term toxicity and detrimental stress shielding effects, the newly developed alloys are closing in on the gaps, however, falling short of the desired elastic modulus necessary to rule out stress shielding. In this work, we report the fabrication of a low modulus β-Ti alloy, Ti–35Nb–7Zr–5Ta (TNZT), by selective laser melting (SLM) with optimized laser parameters. The as-prepared SLM TNZT shows a high ultimate tensile strength (~630 MPa), excellent ductility (~15%) and a lower elastic modulus (~81 GPa) when compared to the state-of-the-art cp-Ti and Ti-based alloys. The mechanical performance of the as-printed TNZT alloy has been examined and is correlated to the microstructure (grain structure, phase constitution and dislocation density). It is proposed that a high density of GND (geometrically necessary dislocations), resulting from rapid cooling, in the as-prepared condition strengthens the alloy, whereas the single phase β-bcc crystal structure results in lowering the elastic modulus. High grain boundary area and a preferred crystal orientation of {200} planes within the bcc crystal lattices contribute to an additional drop in the elastic modulus of the alloy. It is shown that the TNZT alloy, processed by SLM, demonstrates the best combination of strength and modulus, illustrating its potential as a promising biomaterial of the future. © 2020.This work was supported by the European Regional Development Fund (ASTRA6-6, ASTRA35-6 and MOBERC15). The authors would like to thank Dr. Vitali Podgurski, Mr. Andrei Bogatov, Mr. Asad Alamgir Shaikh, Dr. Mart Viljus, Dr. Märt Kolnes, Mr. Rainer Traksmaa, Mr. Endel Esinurm and Ms. Laivi Väljaots for extending research facilities and helping to improve the research outcome with stimulating discussions

Quantum cascade laser based hybrid dual comb spectrometer

Four-wave-mixing-based quantum cascade laser frequency combs (QCL-FC) are a powerful photonic tool, driving a recent revolution in major molecular fingerprint regions, i.e. mid- and far-infrared domains. Their compact and frequency-agile design, together with their high optical power and spectral purity, promise to deliver an all-in-one source for the most challenging spectroscopic applications. Here, we demonstrate a metrological-grade hybrid dual comb spectrometer, combining the advantages of a THz QCL-FC with the accuracy and absolute frequency referencing provided by a free-standing, optically-rectified THz frequency comb. A proof-of-principle application to methanol molecular transitions is presented. The multi-heterodyne molecular spectra retrieved provide state-of-the-art results in line-center determination, achieving the same precision as currently available molecular databases. The devised setup provides a solid platform for a new generation of THz spectrometers, paving the way to more refined and sophisticated systems exploiting full phase control of QCL-FCs, or Doppler-free spectroscopic schemes

Superconducting single photon detectors integrated with diamond nanophotonic circuits

Photonic quantum technologies promise to repeat the success of integrated nanophotonic circuits in non-classical applications. Using linear optical elements, quantum optical computations can be performed with integrated optical circuits and thus allow for overcoming existing limitations in terms of scalability. Besides passive optical devices for realizing photonic quantum gates, active elements such as single photon sources and single photon detectors are essential ingredients for future optical quantum circuits. Material systems which allow for the monolithic integration of all components are particularly attractive, including III-V semiconductors, silicon and also diamond. Here we demonstrate nanophotonic integrated circuits made from high quality polycrystalline diamond thin films in combination with on-chip single photon detectors. Using superconducting nanowires coupled evanescently to travelling waves we achieve high detection efficiencies up to 66 % combined with low dark count rates and timing resolution of 190 ps. Our devices are fully scalable and hold promise for functional diamond photonic quantum devices.Comment: 28 pages, 5 figure

Severe warm-rolling mediated microstructure and texture of equiatomic CoCrFeMnNi high entropy alloy: A comparison with cold-rolling

The effect of severe warm-rolling on the microstructure and texture development in FCC equiatomic CoCrFeMnNi HEA was investigated in the present work. For this purpose, the HEA was warm-rolled to 90% reduction in thickness at 600 °C and annealed for 1 h at temperatures up to 1200 °C. To highlight the effect of warm-rolling, a critical comparison was made with similarly deformed and annealed cold-rolled HEA. The warm-rolled HEA showed an ultrafine lamellar microstructure, which was, however, significantly coarser than the cold-rolled HEA. The significantly coarser microstructure in the warm-rolled HEA could be attributed to the dynamic annihilation of dislocations during deformation. Warm-rolled HEA showed a pure metal or copper type texture instead of a predominantly brass type texture in the cold-rolled HEA. The stark differences in the deformation texture could be attributed to the increase in the SFE at the temperature of warm-rolling, which promoted more homogeneous deformation by dislocation slip over twin mediated deformation and extensive shear band formation. The lower stored energy and coarser deformation structure of the warm-rolled HEA resulted in higher recrystallization temperature, and consistently larger recrystallized grain size than the cold-rolled HEA. Annealing also resulted in the weakening of the recrystallization texture owing to the absence of strong preferential nucleation or growth. The HEA warm-rolled and annealed at 750 °C resulted in a fine-grained, completely recrystallized microstructure with the optimum strength-ductility combination. The present results revealed that warm-rolling could be effectively used as a processing route for tailoring microstructure and properties of CoCrFeMnNi HEA

An Electrochemical Approach for Development of Novel Magnetic Multicomponent Alloy Thin Films for Sensor Applications

Magnetic multi-component alloys (MCAs) are the new class of multicomponent alloys where, combination of magnetic properties can be tuned with the composition. Due to their significant performance, MCAs have been proposed as the most appropriate choice of materials for several magnetic based sensor applications such as magnetoresistive sensors, etc. At times, for each application, multilayers with specific combination of magnetic properties or morphology throughout the material is required. In such cases, composition of alloying elements plays a significant role in the magnetic behaviour. Electrochemical approach in aqueous media is the most cost-effective method and favours better control over the composition with the help of pulse parameters. Therefore, major focus of the present work is to replace the non-aqueous/organic electrolytes with aqueous electrolytes for synthesizing the MCAs with five and/or six elements through electrodeposition. To the best of our knowledge, there haven’t been any reports on deposition of five principle alloying elements by an electrochemical approach in a single step using an aqueous media. The present study reveals the details on electrochemical deposition of multicomponent alloy thin films (Fe, Co, Ni, X, Y) for magnetic sensor applications. Firstly, a single step approach to develop nanocrystalline Fe-Co-Ni-X-Y (X, Y: Transition elements) MCA thin films is presented. Subsequently, the control over composition of MCA thin films and preliminary studies on their magnetic behaviour will be discussed. Finally, tuning of the magnetic properties of MCAs, such as saturation magnetization, magnetic permeability, and coercivity with respect to composition will be discussed. Based on the performance, these MCA thin films will be categorized for specific sensor applications. As it is important to understand the microstructure and composition of these MCA thin films, preliminary characterisation has been carried out using X-ray diffraction, scanning electron microscopy. For transmission electron microscopy (TEM), specimens have been prepared using focused ion beam (FIB) and analytical scanning/transmission electron microscopy including energy dispersive spectroscopy and electron energy loss spectroscopy have been carried out. The magnetization reversal curves for the MCA thin films were acquired initially using Kerr microscopy and detailed magnetic characterization will be carried out using physical property measurement system (PPMS) with a vibrating sample magnetometer. All the comprehensive details of this study will be discussed during the presentation