The Research and Development of Glass-Cladding Single-Mode YAG Crystal Fiber
Date Issued
2015
Date
2015
Author(s)
Xu, Ya-Qin
Abstract
Single-mode fibers are the key components in applications such as high gain active component, high efficient laser and high brightness light source. As for fiber amplifier, single-mode propagating is an essential way to get rid of the impact from gain competing. Thus in order to get larger gain at a typical wavelength, single mode Cr4+:YAG crystal fiber need to be developed. High concentration glass-cladding Cr4+:YAG crystal fibers were made. The concentration of Cr4+ ions was increased to 1.023×〖10〗^24 m^(-3), improving more than 3 times compared to previous fibers. Within a normal case, fiber length of 4.5 cm, core diameter of 25 µm and a maximum pump power of 450 mW, a maximum gain of 1.69 dB can be get. The improved model is fiber length of 10 cm, core diameter of 20 µm Cr4+ concentration of 2×〖10〗^24 m^(-3) and pump power of 20 W, in which the gain can be improved to 23.43 dB. The gain saturation signal power is about 7 dBm. A single-mode pure YAG crystal fiber was successfully fabricated. The cores of crystal fibers were grown by laser-heated pedestal growth (LHPG) method, and the cladding made of glass by the co-drawing LHPG process. The high-refractive index glass, N-LasF9 from Schott has been chosen as the most proper cladding material to decrease the transverse mode numbers. The cut-off wavelength of this N-LaSF9-cladding pure YAG SCCF can be tuned from 1381 to 941 nm by varying the cladding co-drawing speed from 2 to 50 mm/min in the CD-LHPG process. With a cladding speed larger than 10 mm/min, an N-LaSF9-cladding pure YAG SCCF begins to guide at 1064 nm. The maximum refractive index drop of N-LaSF9 glass cladding induced by the LHPG process can reach about 0.009 with the cladding speed of 50 mm/min. Corresponding to our LHPG fabrication process, a 12-µm core diameter and a cladding speed of 13 mm/min is needed to develop an N-LaSF9-cladding YAG fiber which is single-mode guiding at the whole emission bandwidth. In addition, the mode pattern of an N-LaSF9-cladding YAG fiber which is designed to be single-mode guiding beyond 1400 nm is fabricated.
Subjects
single mode
N-LaSF9 cladding
YAG
crystal fiber
fiber amplifier
Type
thesis
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