There is an increasing interest in using graphene , for optoelectronic applications. − However, because graphene is an inherently weak optical absorber (only ≈2.3% absorption), novel concepts need to ...be developed to increase the absorption and take full advantage of its unique optical properties. We demonstrate that by monolithically integrating graphene with a Fabry-Pérot microcavity, the optical absorption is 26-fold enhanced, reaching values >60%. We present a graphene-based microcavity photodetector with responsivity of 21 mA/W. Our approach can be applied to a variety of other graphene devices, such as electro-absorption modulators, variable optical attenuators, or light emitters, and provides a new route to graphene photonics with the potential for applications in communications, security, sensing and spectroscopy.
The increasing demand of rapid sensing and diagnosis in remote areas requires the development of compact and cost-effective mid-infrared sensing devices. So far, all miniaturization concepts have ...been demonstrated with discrete optical components. Here we present a monolithically integrated sensor based on mid-infrared absorption spectroscopy. A bi-functional quantum cascade laser/detector is used, where, by changing the applied bias, the device switches between laser and detector operation. The interaction with chemicals in a liquid is resolved via a dielectric-loaded surface plasmon polariton waveguide. The thin dielectric layer enhances the confinement and enables efficient end-fire coupling from and to the laser and detector. The unamplified detector signal shows a slope of 1.8-7 μV per p.p.m., which demonstrates the capability to reach p.p.m. accuracy over a wide range of concentrations (0-60%). Without any hybrid integration or subwavelength patterning, our approach allows a straightforward and cost-saving fabrication.
We provide a comprehensive DFT investigation of the mechanistic details of CO2 fixation into styrene oxide to form styrene carbonate, catalyzed by potassium iodide–tetraethylene glycol complex. A ...detailed view on the intermediate steps of the overall reaction clarifies the role of hydroxyl substances as co-catalysts for the alkali halide-catalyzed cycloaddition. The increase of iodide nucleophilicity in presence of tetraethylene glycol is examined and rationalized by NBO and Hirshfeld charge analysis, and bond distances. We explore how different alkali metal salts and glycols affect the catalytic performance. Our results provide important hints on the synthesis of cyclic carbonates from CO2 and epoxides promoted by alkali halides and glycol complexes, allowing the development of more efficient catalysts.
Abstract
Mid-infrared spectroscopy is a sensitive and selective technique for probing molecules in the gas or liquid phase. Investigating chemical reactions in bio-medical applications such as drug ...production is recently gaining particular interest. However, monitoring dynamic processes in liquids is commonly limited to bulky systems and thus requires time-consuming offline analytics. In this work, we show a next-generation, fully-integrated and robust chip-scale sensor for online measurements of molecule dynamics in a liquid solution. Our fingertip-sized device utilizes quantum cascade technology, combining the emitter, sensing section and detector on a single chip. This enables real-time measurements probing only microliter amounts of analyte in an in situ configuration. We demonstrate time-resolved device operation by analyzing temperature-induced conformational changes of the model protein bovine serum albumin in heavy water. Quantitative measurements reveal excellent performance characteristics in terms of sensor linearity, wide coverage of concentrations, extending from 0.075 mg ml
−1
to 92 mg ml
−1
and a 55-times higher absorbance than state-of-the-art bulky and offline reference systems.
Deep learning control of THz QCLs Limbacher, Benedikt; Schoenhuber, Sebastian; Kainz, Martin Alexander ...
Optics express,
07/2021, Letnik:
29, Številka:
15
Journal Article
Recenzirano
Odprti dostop
Artificial neural networks are capable of fitting highly non-linear and complex systems. Such complicated systems can be found everywhere in nature, including the non-linear interaction between ...optical modes in laser resonators. In this work, we demonstrate artificial neural networks trained to model these complex interactions in the cavity of a Quantum Cascade Random Laser. The neural networks are able to predict modulation schemes for desired laser spectra in real-time. This radically novel approach makes it possible to adapt spectra to individual requirements without the need for lengthy and costly simulation and fabrication iterations.
We grew wafer-scale, uniform nanolayers of gallium telluride (GaTe) on gallium arsenide (GaAs) substrates using molecular beam epitaxy. These films initially formed in a hexagonal close-packed ...structure (h-GaTe), but monoclinic (m-GaTe) crystalline elements began to form as the film thicknesses increased to more than approximately 90 nm. We confirmed the coexistence of these two crystalline forms using x-ray diffraction and Raman spectroscopy, and we attribute the thickness-dependent structural change to internal stress induced by lattice mismatch with the substrate and to natural lattice relaxation at the growth conditions.
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