Fabrication and Measurement of Few-Mode Cr4+:YAG Crystal Fibers

• Main Authors: Chih-Wei Chuang, 莊智煒
• Other Authors: Wood-Hi Cheng
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/39633090370771779855

碩士 === 國立中山大學 === 光電工程學系研究所 === 101 === In this study, a few-mode chromium doped yttrium aluminum garnet(Cr4+:YAG) crystalline fiber with high-index glass cladding has been demonstrated by employing laser heated pedestal growth(LHPG) and drawing-tower method. The 38μm single crystal Cr4+: YAG fiber was fabricated by modified LHPG and inserted into a capillary of N-SF57 high-index glass with the inner and outer diameters of 70/260μm fabricated by fiber drawing tower. Then, a CO2 laser beam was focused and shone around the capillary in order to heat it up to collapsing the tightly-fitted glass capillary. The refractive index difference between core and cladding can be reduced below 10-2. Few-mode group LP11 can operate at 1550nm and 1400nm that were verified by far-field pattern. Few-mode propagation can significantly reduce the threshold of pump power that helps to eliminate heat effect and increase fluorescence efficiency in comparison with the multimode propagation. The fluorescent spectrum of few-mode high index glass cladded Cr4+:YAG fiber(HICCDF) show that a near-infrared broadband emission from 1.3-1.6μm which was almost the same as Cr4+:YAG rod. The gross gain of HICCDF in 3.8cm length was 2.1dB with single pumped power of 240mW. The pumping architecture was modified to dual pumping that the fiber can be pumped more efficient. The gross gain of HICCDF can improve to 2.79dB with dual pumped power of 240mW. In comparison with few-mode small core double-clad Cr4+:YAG fiber(DCF), HICCDF was able to grow into longer length. It indicated that HICCDF can improve the gain property by raising the concentration of Cr4+-ion. The insertion loss can also be reduced by larger core diameter of HICCDF. According to the above, HICCDF has potential to be developed as a broadband laser and an optical fiber amplifier.