2020, Azkune, Mikel, Frosch, Timea, Arrospide, Eneko, Aldabaldetreku, Gotzon, Bikandi, Iñaki, Zubia, Joseba, Popp, Jürgen, Frosch, Torsten

This work reports the development and application of two liquid-core microstructured polymer optical fibers (LC-mPOF) with different microstructure sizes. They are used in a fiber-enhanced Raman spectroscopy sensing platform, with the aim of detecting glucose in aqueous solutions in the clinically relevant range for sodium-glucose cotransporter 2 inhibitor therapy. The sensing platform is tested for low-concentration glucose solutions using each LC-mPOF. Results confirm that a significant enhancement of the Raman signal is achieved in comparison to conventional Raman spectroscopy. Additional measurements are carried out to obtain the valid measurement range, the resolution, and the limit of detection, showing that the LC-mPOF with 66-µm-diameter central hollow core has the highest potential for future clinical applications. Finally, preliminary tests successfully demonstrate glucose identification in urine. © 1983-2012 IEEE.

2020, Crespo, Helder M., Witting, Tobias, Canhota, Miguel, Miranda, Miguel, Tisch, John W.G

In laser-matter interaction experiments, it is of paramount importance to characterize the laser pulse on target (in situ) and at full power. This allows pulse optimization and meaningful comparison with theory, and it can shed fundamental new light on pulse distortions occurring in or on the target.Here we introduce and demonstrate a new technique based on dispersion-scan using the concurrent third harmonic emission from the target that permits the full (amplitude and phase), in situ, in-parallel characterization of ultrashort laser pulses in a gas or solid target over a very wide intensity range encompassing the 1013-1015Wcm-2regime of high harmonic generation and other important strong-field phenomena, with possible extension to relativistic intensities presently inaccessible to other diagnostics. © 2020 OSA - The Optical Society. All rights reserved.

2020, Kuznetsov, Alexander S., Dagvadorj, Galbadrakh, Biermann, Klaus, Szymanska, Marzena H., Santos, Paulo V.

The spatially varying strain field of the wave induces state-dependent energy shifts of discrete polariton levels with the appropriate symmetry for OPO triggering. The robustness of the dynamic acoustic tuning is demonstrated by the synchronous excitation of an array of confined OPOs using a single wave, which thus opens the way for the realization of scalable nonlinear on-chip systems. © 2020 Optical Society of America

2020, Bauer, Joachim, Gutke, Marko, Heinrich, Friedhelm, Edling, Matthias, Stoycheva, Vesela, Kaltenbach, Alexander, Burkhardt, Martin, Gruenefeld, Martin, Gamp, Matthias, Gerhard, Christoph, Steglich, Patrick, Steffen, Sebastian, Herzog, Michael, Dreyer, Christian, Schrader, Sigurd

In this work we present a novel optical polymer system based on polyurethane elastomer components, which combines excellent UV transparency with high thermal stability, good hardness, high surface tension and long pot life. The material looks very promising for encapsulation and microlensing applications for chip-on-board (CoB) light-emitting diodes (LED). The extinction coefficient k, refractive index n, and bandgap parameters were derived from transmission and reflection measurements in a wavelength range of 200-890 nm. Thermogravimetry and differential scanning calorimetry were used to provide glass transition and degradation temperatures. The surface tension was determined by means of contact angle measurements. As proof of concept, a commercial InGaN-CoB-LED is used to demonstrate the suitability of the new material for the production of microlenses. © 2020 Optical Society of America.

2020, Richter, Maria, Lytova, Marianna, Morales, Felipe, Haessler, Stefan, Smirnova, Olga, Spanner, Michael, Ivanov, Misha

In standard lasers, light amplification requires population inversion between an upper and a lower state to break the reciprocity between absorption and stimulated emission. However, in a medium prepared in a specific superposition state, quantum interference may fully suppress absorption while leaving stimulated emission intact, opening the possibility of lasing without inversion. Here we show that lasing without inversion arises naturally during propagation of intense femtosecond laser pulses in air. It is triggered by the combination of molecular ionization and molecular alignment, both unavoidable in intense light fields. The effect could enable inversionless amplification of broadband radiation in many molecular gases, opening unusual opportunities for remote sensing. © 2020 Optical Society of America

2020, Lindner, F., Kriltz, A., Scheffel, A., Dellith, A., Dellith, J., Wondraczek, K., Bartelt, H.

The incorporation of phosphorus into silica soot material strongly changes during the multistep preparation process of the MCVD technology in combination with solution doping for Al and rare earths. We report on the influence of various process parameters on the phosphorus concentration, the bond types of phosphorus atoms and the relative density of the soot material. By optimization of the process the phosphorus concentration of the presintered soot could be increased by around 10% in comparison to the conventional treatment. The understanding of the interdependencies allows an improvement of the preparation process of phosphorus co-doped RE doped silica laser fibers with MCVD technology.