Study on the single-mode condition for x-cut LNOI rib waveguides based on leakage losses.

Lithium niobate-on-insulator (LNOI) has recently emerged as a promising material platform for high-density and advanced photonics integrated circuits (PICs). And single-mode waveguides (SMW) are the most basic building blocks for structuring various PICs. In this paper, single-mode conditions (SMCs) for shallowly etched LNOI rib waveguides in x-cut LNOI wafer are investigated with the finite element method (FEM) in consideration of the lateral leakage and the magic width for the first time, to our best knowledge. Our results indicate that due to the lateral leakage and the magic width these shallowly etched x-cut LNOI rib waveguides have unique and complex SMCs. Our method and results provide a guidance in designing low-loss LNOI SMW and high-performance PICs.

[UV-Visible Spectra Properties of DOM from Taizi River in Benxi City Section by Multivariable Analysis].

This study investigated the ability of ultra violet-visible (UV-Visible) spectroscopy to analyze the origin,compositions,structure and humification level of dissolved organic matter(DOM). Seven surface water samples were collected from the Benxi City section of mainstream in Taizi River. Nine indices (SUVA254, E2/E3, E2/E4, E4/E6, S275-295, S350-400, A2/A1, A3/A1 and A3/A2), deduced from elemental analysis and UV visible spectroscopy of DOM, were used to assess the humification degree. The results showed that the characteristics of DOM were distributed along urban river and industrial wastewater discharge, and the DOM of waste water from Benxi steel plant contained a low degree of condensation of small organic molecules. E2/E3 showed positive correlation with E2/E4, and negative correlations with S275-295, S350-400, A2/A1,indicating that humification degree of DOM was not only concerned with the degree of condensation of organic molecules, but also closely associated with the ratio between humic acid and fulvic acid. Composition structure of DOM showed significant positive correlations with A2/A1, SUVA254 and S275-295, and significant negative correlations with E2/E3 and E2/E4. Based on the loadings of DOM component and scores plot of sampling sites in Taizi River (Benxi City section),the characteristics of DOM were distinctly distributed along urban river and industrial wastewater discharge, proving that the river was deeply influenced by human activity.