We present a new concept of three-dimensional (3D) polymer-based 1x4 beam splitter for wavelength splitting around 1550 nm. The beam splitter consists of IP-Dip polymer as a core and polydimethylsiloxane (PDMS) Sylgard 184 as a cladding. The splitter was designed and simulated with two different photonics tools and the results show high splitting ratio for single-mode and multi-mode operation with low losses. Based on the simulations, a 3D beam splitter was designed and realized using direct laser writing (DLW) process with adaptation to coupling to standard single-mode fiber. With respect to the technological limits, the multi-mode splitter having core of (4x4) μm2 was designed and fabricated together with supporting stable mechanical construction. Splitting properties were investigated by intensity monitoring of splitter outputs using optical microscopy and near-field scanning optical microscopy. In the development phase, the optical performance of fabricated beam splitter was examined by splitting of short visible wavelengths using red light emitting diode. Finally, the splitting of 1550 nm laser light was studied in detail by near-field measurements and compared with the simulated results. The nearly single-mode operation was observed and the shape of propagating mode and mode field diameter was well recognized.

In order to increase the corrosion resistance of magnesium alloy AZ91 in corrosion environments containing chlorides, the alloy surface has been modified by plasma electrolytic oxidation (PEO). The chemical composition of electrolyte in the PEO process consisted of 12 g/L Na₃PO₄·12 H₂O and 1 g/L KOH, and a direct current was applied to the sample. The corrosion resistance of PEO coating and as-cast AZ91 (sample without PEO coating) was assessed using two different electrochemical methods: electrochemical impedance spectroscopy (EIS) and potentiodynamic polarisation (PDP) in 0.1 M NaCl at laboratory temperature. In addition to the electrochemical methods, the morphology of the oxidic coating was observed in the cross-sectional and top surface view by using the SEM technique. For better determination of the microstructure and PEO coating, chemical composition EDX analysis was used. The results of the experiments show that the formation of the PEO coating on AZ91 alloy has a more positive effect on the corrosion resistance in 0.1 M NaCl based on electrochemical methods than in the case of the formed coating on AZ31 alloy from the previous study. Based on electrochemical measurements in the selected environment, the formation of PEO coating on AZ91 was accompanied by a significant increase in polarisation resistance after short-term exposure compared to the as-cast surface. The EIS results showed a 73 times higher R_p value for PEO coated AZ91 when compared to the as-cast AZ91. Correspondingly, a 27 times lower i_corr value was observed for PEO coated AZ91 than in the case of substrate AZ91 in 0.1 M NaCl. At the same time, the typically porous and inhomogeneous structure of the formed PEO coating on the magnesium alloy AZ91 was demonstrated.

We demonstrate an ultrahigh-sensitive plasmonic sensing of gas, employing a two-dimensional (2D) dielectric grating fabricated by laser interference lithography. The 2D grating was designed with the period of 500 nm and prepared in an AZ1505 photoresist layer on a gold film of 20 nm thickness deposited on a fused silica glass substrate. The surface plasmon resonance (SPR) in the Kretschmann configuration with spectral interrogation was utilized to measure the response of the sensor to vapors of aqueous solution of ethanol. Based on measurement of the gas refractive indices with the reference Au/Cr/SF10 sample, the resonance wavelength dependence was obtained. The SPR response of the structure in a spectral range of 1.68–1.85 µm with a sensitivity of 8200–111,000 nm/RIU was revealed. The sensor provides significantly higher sensitivity in comparison to conventional and grating-based SPR sensors.