Publications by authors named "Frank Schrempel"
Article Synopsis
- Nonlinear optical nanoscale waveguides enable effective wavelength conversion, making them useful in microscopy for delivering light while minimizing biological tissue damage.
- A novel high-precision fabrication method for these waveguides uses lithium niobate, known for its strong nonlinearity and wide transparency range.
- The developed waveguides, measuring 5 to 50 μm in length and 50 to 1000 nm in width, were successfully tested, demonstrating effective second-harmonic generation.
Nanoscale waveguides are basic building blocks of integrated optical devices. Especially, waveguides made from nonlinear optical materials, such as lithium niobate, allow access to a broad range of applications using second-order nonlinear frequency conversion processes. Based on a lithium niobate on insulator substrate, millimeter-long nanoscale waveguides were fabricated with widths as small as 200 nm.
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- The study explores the nonlinear optical properties of lithium niobate (LiNbO(3)) nanowires (NWs) created using an ion beam etching method.
- It demonstrates the generation and propagation of second-harmonic (SH) light in NWs and shows how this light can locally excite a fluorescent dye (DAPI) at concentrations relevant for biological uses.
- The research concludes that a small amount of SH light power is required for detectable dye excitation, and it models the optimal NW dimensions to minimize potential cell damage while still enabling effective fluorescence excitation.
After annealing at 540°C, NiTi is covered by a characteristic oxide layer with an Ni-containing outer and an Ni-free inner titanium oxide region. To elucidate details of the yet unclear formation process, samples were annealed in an atmosphere containing different oxygen isotopes at a time and analyzed by nondestructive ion beam techniques at different stages of the oxidation. During the heating stage, an oxygen permeable "low Ni" titanium oxide forms, and the oxide layer grows inward.
View Article and Find Full Text PDFIon-beam enhanced etching is used to pattern a bulk lithium niobate crystal with ultrathin membranes. By the implementation of an air gap beneath the membrane, high index contrast is achieved. A buried amorphous layer, created by irradiation with He ions, is removed by means of wet chemical etching in hydro-fluoric acid.
View Article and Find Full Text PDFWe present results on the fabrication and characterization of ridge waveguides in zinc-substituted lithium niobate. High-quality waveguides were fabricated by a combination of liquid-phase epitaxy and multiple applications of ion-beam enhanced etching. The two major demands on ridge waveguides, a very low side-wall roughness and a rectangle shape with side-wall angles close to 90 degrees , were realized simultaneously by using this technique.
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