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Amorphous aluminum oxide (Al2O3) is a key material in optical coatings due to its notable properties, including a broad transparency window (ultraviolet to mid-infrared) and excellent durability. Moreover, its higher refractive index contrast relative to silica cladding layers and high solubility of rare-earth ions make it well suited for optical waveguides and the development of various functionalities in integrated photonics. In many coatings and integrated photonics applications, the substrates are temperature and stress sensitive, while relatively thick (∼1 μm) alumina layers are required; thus, it is crucial to fabricate low optical loss alumina thin films at low deposition temperatures, while maintaining high deposition rates. In this study, plasma-assisted reactive magnetron sputtering, operated in an alternating current mode, is investigated as a reliable, straightforward, and wafer-scale compatible technique for the deposition of high optical quality and uniform Al2O3 thin films at low temperature. One-micrometer-thick amorphous Al2O3 planar waveguides, deposited at 150 °C and a rate of 23.3 nm/min, exhibit optical losses below 1 dB/cm at 638 nm and as low as 0.1 dB/cm in the conventional optical communication band. [ABSTRACT FROM AUTHOR]

Photoelectrochemical (PEC) signal transduction has emerged as a powerful technique for ultrasensitive biosensing with a low background in complex media. However, it remains challenging to create PEC biosensors found on stable materials that are easily biofunctionalized. Herein, we report the development of a one-pot synthesis method for TiO2 nanoparticles (NPs) decorated with Ag NPs. In this nanomaterial synthesis process, TiO2 NPs are modified with hematoxylin (HTX) dye to achieve enhanced photoreduction and direct nucleation of Ag NPs. The resulting TiO2/HTX/Ag NP heterostructure showed significantly enhanced photocurrent generation, necessary for achieving high sensitivity in PEC biosensing, through the combined effects of plasmon resonance and photoelectron injection. TiO2/HTX/Ag NP is very easily biofunctionalized through thiol–metal complexation. This was taken as an advantage to create a multiplexing PEC microRNA sensor for the analysis of urine samples, which demonstrated a low limit of detection of 172 fM and a high dynamic range of 100 fM–100 nM, while showing a high degree of specificity. [ABSTRACT FROM AUTHOR]

This paper reports tunable emission of trivalent (Eu3+) and divalent (Eu2+) europium (Eu) from SiOxNy films fabricated by integrated electron cyclotron plasma enhanced chemical vapor deposition and magnetron sputtering. The photoluminescence (PL) spectra of intense red emission from Eu3+ around 600 nm and blue (cyan) broadband emission from 400 to 750 nm of Eu2+ are observed under daylight conditions with the naked eye. The spectra reveal a strong dependency of the PL on the atomic concentration of the dopant and the silicon/nitrogen ratio. The atomic composition of the films is investigated by Rutherford backscattering spectrometry and elastic recoil detection analysis. Values of the refractive indices are obtained by variable angle spectroscopic ellipsometry. To confirm the presence of crystalline phases of europium silicate Eu4.67(SiO4)3O [Eu2(Si2O7)] and europium silicon oxynitride (EuSi2N2O2) distributed in the amorphous host matrix of SiOxNy, high-resolution x-ray diffraction is used. The findings of this work are promising toward the realization of europium-doped Si-based materials for photonics and lighting technologies. [ABSTRACT FROM AUTHOR]

Systematical studies are conducted on the formation of output spectra of external-cavity semi-conductor lasers (ECSLs), by using different antireflection (AR) coated laser diodes (LDs) with multimode fiber Bragg gratings (MMFBGs). Experimentally it is found, that the SMSR (side mode suppression ratio) change induced by the relative position of the Bragg wavelength and intracavity modes of LD is increased.