We simulate and experimentally demonstrate deep ultraviolet generation from a 1550 nm laser source in a fully fiberized system by cascading second- and third-harmonic generation using a periodically poled silica fiber and an optical sub-micron diameter fiber. Harmonic generation is achieved by harnessing intermodal phase matching in optical microfibers and a permanent χ induced via thermal poling. As a result, efficient nonlinear processes can be observed, despite the low third-order nonlinear susceptibility of silica glass.
We report a form of double edge-diffraction (DED) for the first time, in which successive diffractive effects between two opaque objects leads to a virtual shadow of one object that protrudes from the shadow of the other. Analogous to classic edge and slit diffractions, the method to observe DED is simple, yet its effect is intriguingly different. Existing sensing techniques cannot measure the distance of highly reflective or absorptive opaque objects. To address this problem in certain scenarios, we propose a new technique based on DED that is the first to work for all opaque objects with welldefined edges.
Most distributed optical fiber sensors rely on commercially available telecom fibers, which are low-loss, inexpensive, and standardized. In the last few years, significant effort has been made to develop optical fibers optimized for specific sensing applications, with the view of improving the signalto-noise ratio (SNR) or extending the distance over which distributed optical fiber sensors (DOFS) operate. This tutorial reviews the efforts made by the scientific community towards the development of enhanced backscattering fibers and enhanced backreflection fibers, with a focus on DOFS.
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