Sharp bend and large FSR ring resonator based on the free-form curves on a thin-film lithium niobate platform.

Sharp bends are crucial for large-scale and high-density photonics integration on thin-film lithium niobate platform. In this study, we demonstrate low-loss (<0.05 dB) and sharp bends (Reff = 30 µm) using free-form curves with a 200-nm-thick slab and a rib height of 200 nm on x-cut lithium niobate. Employing the same design method, we successfully realize a compact fully-etched ring resonator with a remarkably large free spectral range of 10.36 nm experimentally. Notably, the equivalent radius of the ring resonator is a mere 15 µm, with a loaded Q factor reaching 2.2 × 104.

Atomic Layer Deposition of the Geometry Separated Lewis and Brønsted Acid Sites for Cascade Glucose Conversion.

Solid acid catalysts with bi-acidity are promising as workhouse catalysts in biorefining to produce high-quality chemicals and fuels. Herein, we report a new strategy to develop bi-acidic cascade catalysts by separating both acid sites in geometry via the atomic layer deposition (ALD) of Lewis acidic alumina on Brønsted acidic supports. Visualized by transmission electron microscopy and electron energy loss spectroscopy mapping, the ALD-deposited alumina forms a conformal alumina domain with a thickness of around 3 nm on the outermost surface of mesoporous silica-alumina. Solid state nuclear magnetic resonance investigation shows that the dominant Lewis acid sites distribute on the outermost surface, whereas intrinsic Brønsted acid sites locate inside the nanopores within the silica-rich substrate. In comparison to other bi-acidic solid catalyst counterparts, the special geometric distance of Lewis and Brønsted acid sites minimized the synergetic effect, leading to a cascade reaction environment. For cascade glucose conversion, the designed ALD catalyst showed a highly enhanced catalytic performance.