Optimization of TM-Doped Phosphosilicate Glass for High Power Fiber Lasers
Technical Report,08 Oct 2014,28 Apr 2016
Clemson University, Office of Sponsored Programs Clemson United States
Pagination or Media Count:
This work is to investigate the possibilities of further power scaling of fiber lasers by using Tm-doped fiber lasers with much improved efficiency and advanced designs. The resulting optimized Tm-doped glass is critical for the realization of single-mode Tm-doped advanced optical fibers with much increased effective mode areas. They can lead to one to two orders of magnitude improvement in further power scaling of single-frequency fiber lasers, and direct generation of optical pulses with up to 20MW peak powers and pulse energy of many tens of mJ. These fibers are also critical for the generation of ultrafast optical pulses with up to TW peak power and many kW of average powers through fiber chirped pulse amplification FCPA scheme. The resulting ultrafast high power fiber lasers have many applications. The program has focused on finding a glass host which would provide improved laser efficiency. We have been focusing on silica hosts with varying amount of phosphorus and aluminum. Conventional Tm host has been heavily aluminum-doped silica. We have focused on three new key host compositions, 1 high P, low Al, 2, high P and high Al, and 3 low P and high Al. Corresponding passive fibers without Tm are also made for each compositions to test background losses at 2m. During the program, we have set up a test facility for Tm-doped fiber lasers with pump power of 300W at 790nm. We have fabricated a large number of fibers and conducted numerous tests. We have found the high P composition can provide internal efficiency up to 80, near quantum limited efficiency. Our results show the OH level in our fabrication process is adequate. We have found there is evidence of high background loss at 2m being responsible for large part of the efficiency degradation.