Ytterbium aluminum phosphorus fluorine doped silica optical fiber preform core rod and preparation method thereof

Abstract

A preparation method of an ytterbium aluminum phosphorus fluorine doped quartz optical-fiber preform core rod is achieved based on an improved chemical vapor deposition (MCVD) process and by combining with a solution soaking process. First of all, a loose fluorine-containing silicon dioxide nano-particle layer having a certain thickness deposits in a quartz tube based on a chemical deposition process and then is put in an ytterbium chloride and aluminum chloride solution with a certain concentration to achieve even ytterbium and aluminum co-doping, drying and dehydroxylation are performed, then a raw material phosphorus oxychloride is put into the doping quartz tube by utilizing high-purity oxygen, and the ytterbium aluminum phosphorus fluorine doped quartz optical-fiber preform core rod is obtained through high-temperature vitrification and diffusion process. The method can achieve preparation of the large-diameter ytterbium-doped core rod with the refractive index higher than pure quartz, with errors adjustable in the range of 0.0004-0.0008 and having good axial refractive index consistency and with the radial refractive index distributed zigzag.

Description

Technical field [0001] The invention relates to the field of optical fiber preforms, in particular to a ytterbium-aluminum-phosphorus-fluorine doped silica optical fiber preform core rod and a preparation method thereof. Background technique [0002] Ytterbium silica fiber is the core component of 1μm fiber laser. With the rapid development of energy optoelectronic technologies such as semiconductor laser pumping and laser coupling, the power of Ytterbium-doped fiber lasers has also developed from the initial watt level to the 10,000 watt level. However, high-power lasers have the following technical problems that are difficult to solve, such as: The increase in power per unit area leads to non-linear effects of the fiber, which leads to laser wavelength shift and laser mode instability, which seriously affects the laser efficiency and beam quality; secondly, the operation of the fiber under high power conditions will cause photodarkness Chemical effect, resulting in a decrease ...

AI Technical Summary

Problems solved by technology

[0005] The second is aluminum-phosphorus co-doping (Proc.of SPIE, 2008, Vol. 6890, 689016-1). Studies have shown that aluminum-phosphorus co-doping in quartz glass in equimolar proportions can form AlPO 4 The group structure can greatly reduce the refractive index of the core glass, and at the same time, it has a good effect on the anti-light darkening performance of the optical fiber preform, but the results reported in the literature show that due to the volatilization of phosphorus, the cross-sectional refractive index presents an M type The structure is not conducive to maintaining the mode stability of the fiber under high power conditions;

[0006] The third is fluorine doping, which can reduce the refractive index of the preform core rod (patent CN 103864292 A, application number 201410070217.X), which means that higher ytterbium ion doping can be achieved under the same refractive index conditions Concentration, improve the fiber absorption coefficient, the patent did not achieve phosphorus doping, and did not report the longitudinal consistency of the refractive index

[0010] The difference in refractive index of the preform core rod prepared by this method is 0.0006 higher than that of pure quartz, but it is not doped with fluorine. In order to ensure the refractive index difference of 0.0006, only 0.09% molYb can be achieved 2 o 3 The doping concentration is only 50% of the normal commercial ytterbium-doped fiber, which means that a longer fiber is needed to fully absorb the pump light, which is easy to cause nonlinear effects, which is not conducive to the application of fiber at high power

In addition, phosphorus and silicon are deposited at the same time in the process proposed by this method. Due to the different saturated vapor pressures of phosphorus oxychloride and silicon tetrachloride, mixing at the same temperature may cause different sediment components at different positions of the deposition tube, which is not conducive to Controlling the Longitudinal Consistency of Refractive Index of Preform Mandrel

[0011] In summary, the published papers or patents do not solve the problem of the preparation process of the ytterbium aluminum phosphorus fluoride doped silica optical fiber preform core rod with better refractive index distribution by MCVD method

Images