Effect of the incident light beam conditions, such as the beam profile, the beam size, and the incident angle on the beam propagation and the firing characteristics of the radial-firing optical fiber tip comprised of conically shaped air pocket was investigated by the simulation using the ray-tracing method. Regardless of the different Gaussian profiles of the incident beam, no significant difference in the maximum firing angle but a little increase in the firing power was found with the increase of the axial distance of the Gaussian profile. With the increase of the incident beam size, no significant difference in the maximum firing angle was found but the relative firing power decreased and the extent of the power decrease depended on the numerical aperture (NA) of the fiber. On the other hand, the incident beam angle (BA) dependence of the firing power was significant, decreased to 65.9% and 31.9% for the RFF tip of NA 0.12 and NA 0.22, respectively, with the increase of the incident BA from 0 deg to 12 deg but the maximum firing angles did not show much decrease, smaller than 5 deg. The present modified simulation considering the incident light beam size and angle clearly showed the very close power distribution of the firing beam with respect to the firing angle obtained by the experimental results.
In this study, highly Dy3+-doped germano-borate glasses for different dopant concentrations ranging from 20 to 30 mol% were fabricated and their physical, optical, and MO properties were investigated. The characteristic thermal parameters disclosed good thermal stability of <100 °C against crystallization in the studied glasses. In addition, the glasses showed a high optical transmission of ~ 85% in the NIR region of 1550 nm. A very large Verdet constant of approximately -5.36 rad/(T·m) at 1550 nm was obtained in the glass containing 30 mol% Dy2O3. Therefore, this glass might be a promising MO material for applications in the NIR region.
We report a large-core radial-firing optical fiber tip comprised of conically shaped air-pocket, fabricated by deforming a hollow optical fiber fusion-spliced with the large-core optical fiber (LCF) (core/cladding diameters = 200 / 220 μm) using the arc-discharge method. The effect of the intaglio air-pocket angle and the numerical aperture (NA) of the LCF on the radial-firing characteristics of the fiber tip was investigated. The design of air-pocket of the fiber tip was optimized for an effective radial-firing by simulating the beam profile of the radial-firing optical fiber with the ray-tracing method. The 45 deg of the conical angle with the low NA (0.12) of the LCF has shown the maximum radial-firing angle of 81 deg by the simulation. The fabricated LCF tip with the intaglio conical air-pocket with the 45 deg angle has shown the radial-firing angle up to ±78 deg, which was in good agreement with the simulation results. The present LCF radial-firing tip can be an effective element of medical devices for treatment of tubular shape tissues with the high-power transmission and the ease of operation in vivo.
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