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There are still very strong interests for power scaling in high power fiber lasers for a wide range of applications in medical, industry, defense and science. In many of these lasers, fiber nonlinearities are the main limits to further scaling. Although numerous specific techniques have studied for the suppression of a wide range of nonlinearities, the fundamental solution is to scale mode areas in fibers while maintaining sufficient single mode operation. Here the key problem is that more modes are supported once physical dimensions of waveguides are increased. The key to solve this problem is to look for fiber designs with significant higher order mode suppression. In conventional waveguides, all modes are increasingly guided in the center of the waveguides when waveguide dimensions are increased. It is hard to couple a mode out in order to suppress its propagation, which severely limits their scalability. In an all-solid photonic bandgap fiber, modes are only guided due to anti-resonance of cladding photonic crystal lattice. This provides strongly mode-dependent guidance, leading to very high differential mode losses. In addition, the all-solid nature of the fiber makes it easily spliced to other fibers. In this paper, we will show for the first time that all-solid photonic bandgap fibers with effective mode area of ~920?m 2 can be made with excellent higher order mode suppression.

Atmospheric pressure plasmas have been used as a therapy for cancer. However, the fairly large size and rigidity of present plasma-delivery systems obstructs the precise treatment of tumors in harder-to-reach internal organs such as the lungs, pancreas, and duodenum. In order to improve the targeted delivery of plasmas a highly flexible microplasma jet device is fabricated using a hollow-core optical fiber with an inner diameter of either 15 μm, 55 μm, or 200 μm. Described herein, based on this device, are results on lung carcinoma therapy using a microplasma cancer endoscope. Despite the small inner diameter and the low gas flow rate, the generated plasma jets are shown to be sufficiently effective to induce apoptosis, but not necrosis, in both cultured mouse lung carcinoma and fibroblast cells. Further, the lung carcinoma cells were found to be more sensitive to plasma treatment than the fibroblast cells based on the overall plasma dose conditions. This work enables directed cancer therapies using on highly flexible and precise hollow optical fiber-based plasma device and offers enhancements to microplasma cancer endoscopy using an improved method of plasma targeting and delivery., (Copyright © 2011 Elsevier B.V. All rights reserved.)

The authors report laser oscillation in what appears to be a single transverse mode with very large mode area in optical fibers having heavily Nd-doped 100 μm diameter cores with refractive index significantly lower in the core than in the surrounding cladding. Since fibers of this type cannot support conventional index-guided modes, their results appear to confirm a recent analysis which predicts gain-guided single-mode propagation in index antiguided fibers, provided the gain coefficient in the core exceeds a threshold value. Fibers of this type may be of significant interest for amplifiers and oscillators having large power outputs and/or small nonlinear pulse distortion. [ABSTRACT FROM AUTHOR]

Atmospheric-pressure microplasma jets from a linear array of five hollow-core optical fibers are described. All plasma plumes from the array were quite narrow but long enough to apply the direct treatments to a very small object. The optical intensities from five individual plasma jets were also stable and had a good uniformity. The variation of the optical intensities of individual plasma plumes was within 15%. This plurality of the small-sized plasma jets can be utilized to target some groups of different cells simultaneously in an in vitro biomedical application. [ABSTRACT FROM AUTHOR]

Abstract: Crystalline semiconductor core optical fibers have received growing attention as greater understanding of the underlying materials science, coupled with advances in fiber processing and fabrication, have expanded the quality and portfolio of available materials. In a continued effort to better understand the nature of the crystal formation this work studies the role of the cross-sectional geometry on the resultant core crystallography with respect to the fiber axis. More specifically, a molten-core approach was used to fabricate silicon optical fibers clad in silica tubes of either circular or square inner cross-sections. In both geometric cases, the silicon core was found to possess regions of single crystallinity where specific crystal orientations persisted along a fiber length of about 4–5mm prior to transitioning through polycrystalline regions. However, the rotation and tilting angular combination needed to align a given crystallographic axis with the fiber axis was more constant over the single crystalline region in the case of the square-core fiber while more significant variations were observed in the round-core case. This work begins to elucidate some of the microstructural features, not present in conventional glass optical fibers, that could be important for future low-loss single crystalline semiconductor optical fibers. [Copyright &y& Elsevier]