Active gain fiber is a critical component to realize fiber laser sources for various applications such as cutting, welding and other material processing. To meet the requirement for various laser applications, the power scaling of fiber lasers is still concern, where active gain fiber is very important. There are several fabrication technologies for active fibers with low NA, large core diameter and high absorption, which characteristics for high power lasers are typically required. Here, novel fabrication technology based on VAD (Vapor Axial Deposition) for active fibers is introduced.
VAD technology for laser fibers are offering the extremely large rare-earth doped core, which makes it possible to improve the productivity and reproducibility of laser fibers. At the previous report, Yb:Ce co-doped fibers have shown relatively large background loss and the issues of surface crystallization. In this report, the additional process development for the reduction of the loss and the efficiency improvement has been successful. Based in that, Yb:Ce codoped aluminosilicate PM fiber has been fabricated and it used for power amplification of narrow linewidth source. The slope efficiency was 72.8% w.r.t the absorbed pump power and the output power has been reached to 124W at the initial experiment. The further power scaling will be performed and SBS characterization will be reviewed.
In this study, Cylindrical Diffusing Optical Fiber Probe (CDOFP) is used for tumor treatment using Photolon-based photodynamic therapy induced apoptosis and necrosis in thyroid papillary carcinoma (BCPAP) cells. In conclusion, owing to multiple advantageous properties of Photolon as a PDT agent, including preferential accumulation in tumor, biodegradability and unprecedented photosensitizer packing, we evaluate Photolon mediated PDT as a minimally invasive, tumor specific treatment for thyroid cancer. the Photolon-PDT inhibited the growth of human papilloma thyroid cancer cells and effectively decreased xenograft tumor progression in both 10mm and 15mm diffusing length probe. Therefore, this study preliminarily suggests the use of CDOFP and Photolon-PDT for more effective treatment of human thyroid cancer.
VAD technology has been proposed for laser fiber fabrication to improve its productivity and reproducibility. Rare-earth ion, Yb3+ has been incorporated with Ce3+ and Al3+ by the conventional solution doping process. In order to obtain a transparent Yb-doped core rod, the pre-sintering and consolidation process for the large volume of silica soot deposited by VAD has been significantly investigated. In addition, 20/400μm Yb-doped fiber with octagonal cladding has been fabricated. The cladding absorption was 0.44dB/m at 915nm, which corresponds to ~ 0.2mol% of Yb concentration and the slope efficiency with respect to absorbed pump power at 976nm was 66.7%.
We have proposed the systematic measurement of coating geometry for specialty fibers based on dark field illumination technique. The measured dark-field projection image shows clear interfaces between different refractive index materials. Using own developed image processing tool, the interfaces automatically detected and analyzed. Every degree of measurements provides circularity of each layer and then shows the center point of individual layer. Using this technique, coating diameter, coating non-circularity and coating ellipticity for double clad fiber were successfully measured and high resolution camera also detected some of existing coating defect and delamination.
In this study, cylindrical diffusing optical fiber probe (CDOFP) used for tumor treatment using PDT method is developed and analyzed. Diffusing beam profile of 5mm to 40mm tip length probe is produced and analyzed using laser scribing equipment developed in a previous research. Ball tip at the tip of CDOFP was developed for easier infiltration of tissues and the beam profile of such tip is reviewed. Additionally, CDOFP for PDT tumor treatment was used for laser coagulation test on animal tissue. CDOFP with diffusing tip length 5mm and 15mm was infiltrated inside a cow's liver tissue to process laser coagulation test. Coagulation and thermal damage was measured with twice the maximum intensity of laser, where maximum intensity in-vivo test is 1W 200J.
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