Process of fabrication of Erbium and Ytterbium-co-doped multi-elements silica glass based cladding-pumped fiber

Patent metadata

Field	Value
Publication number	US-11407671-B2
Application number	US-201916243621-A
Country	US
Kind code	B2
Filing date	Jan 9, 2019
Priority date	Jun 8, 2018
Publication date	Aug 9, 2022
Grant date	Aug 9, 2022

Abstract

The present application provides a process of fabrication of erbium and ytterbium-co-doped multielements silica glass based cladding-pumped fiber for use as a highly efficient high power optical amplifier.

First claim

We claim:

1. A process for fabricating erbium and ytterbium-co-doped multi-elements silica glass based cladding-pumped fiber for use as an optical amplifier, the process comprising the steps of:
a) depositing a pure SiO 2 synthetic cladding within a silica glass substrate tube to obtain match clad structure;
b) forming a porous core layer inside the silica glass substrate tube by depositing a fluorinated-phospho silica porous soot layer using a flow of O 2 /POCl 3 in a range of 800 to 900 sccm and SF 6 in a range of 25 to 35 sccm, at a temperature in a range of 1420-1455° C. and maintaining a burner speed a range of 28-35 mm/min;
c) pre-sintering the deposited fluorinated-phospho silica porous soot layer at a temperature in a range of 1075-1125° C. by keeping the burner speed in a range of 305 - 315 mm/min in a forward direction to maintain a uniform porosity;
d) soaking the pre-sintered fluorinated-phospho silica porous soot layer into an alcoholic solution for one hour, wherein the alcoholic solution comprises AlCl 3 6H 2 O in a range of 0.12 to 0.15 (M), ErCl 3 6H 2 O in a range of 0.02 to 0.023(M), YbCl 3 6H 2 O in a range of 0.25 to 0.28 (M), CeCl 3 7H 2 O in a range of 0.003 to 0.0035(M) and H 3 BO 3 in a range of 0.5 to 0.75(M);
e) drying the soaked fluorinated-phospho silica porous soot layer under flow of an inert Ar gas for 30 to 45 minutes;
f) incorporating Er 2 O 3 , Yb 2 O 3 , P 2 O 5 , F, CeO 2 , Al 2 O 3 and B 2 O 3 into the dried fluorinated-phospho silica porous soot layer in the presence of O 2 and He at a temperature within a range of 700-850° C. for efficient oxidation to form the core layer;
g) dehydrating the core layer at a temperature in a range of 850 to 900° C. in presence of Cl 2 and O 2 to form a porous dried core layer;
h) sintering the porous core layer in presence of a mixture of O 2 and He at a temperature in a range of 1350 to 1890° C. with flow of O 2 /GeCl 4 and O 2 /POCl 3 to form a final core layer;
i) repeating steps (b) to (h) 2-3 times to form the final core layer of a thickness in a range of 10.0-11.5 μm;
j) collapsing the silica glass substrate tube having the final core layer at a temperature in a range of 2000 to 2250° C. with the flow of POCl 3 to obtain an Er/Yb codoped multi-elements silica glass based optical preform of 10.0±0.1 mm diameter;
k) increasing the preform diameter from 10.0±0.1 mm to 18.5±0.1 mm through an overcladding process using a thick silica tube at a temperature in a range of 2200 to 2400° C. to form an overcladded preform;
l) grinding the overcladded preform to a grinding length in a range of 0.72-0.75 mm from a periphery of the overcladded preform at each point of eight positions separated by equal distances followed by polishing of each grinded sides to form an octagonal shaped preform; and
m) drawing an octagonal cladding shaped Er/Yb doped fiber from the octagonal shaped preform using a PC 375L AP compound as a low RI resin coating at a preform feed down speed in a range of 0.6 to 0.7 mm/min and at a fiber drawing speed in a range of 20-25 m/min.

2. The process as claimed in claim 1 , wherein dehydrating the core layer in presence of Cl 2 and O 2 comprises dehydrating with 2:1 to 2.5: 1 of Cl 2 and O 2 , and wherein sintering the porous dried core layer in presence of a mixture of O 2 and He comprises sintering the porous dried core layer with He: O 2 in a ratio of 0.5dehydrating the core layer in presence of Cl 2 and O 2 comprises dehydrating with 2:1 to 2.5: 1 of Cl 2 and O 2 , and wherein sintering the porous dried core layer in presence of a mixture of O 2 and He comprises sintering the porous dried core layer with He: O 2 in a ratio of 0.5.

3. The process as claimed in claim 1 , wherein sintering the porous dried core layer in presence of a mixture of O 2 and He with flow of O 2 /GeCl 4 and O 2 /POCl 3 comprises sintering with the flow of O 2 /GeCl 4 in a range of 5 to 10 sccm and with the flow of O 2 /POCl 3 in a range of 10 to 15 sccm to form a transparent glass layer.

4. The process as claimed in claim 1 , wherein collapsing the silica glass substrate tube having the final core layer comprises collapsing with the flow of O 2 /POCl 3 in a range of 4.0 to 7.0 sccm, and wherein one end of the silica glass substrate tube is nearly closed to avoid central dip formation in refractive index profile (RIP).

5. The process as claimed in claim 1 , wherein increasing the preform diameter from 10.0±0.1 mm to 18.5±0.1 mm through the overcladding process using a thick silica tube comprises using the thick silica tube having a dimension of OD/ID of 20/12 mm to maintain a core diameter of the octagonal cladding shaped Er/Yb doped fiber in a range of 10.0 to 11.81 micron.

6. The process as claimed in claim 1 , wherein incorporating Er 2 O 3 , Yb 2 O 3 , P 2 O 5 , F, CeO 2 , Al 2 O 3 and B 2 O 3 comprises incorporating multi-elements Er, Yb, P, F, Ce, Al and B uniformly along a diameter of an octagonal classing shaped fiber.

7. The process as claimed in claim 1 , wherein the octagonal cladding shaped Er/Yb doped fiber has a numerical aperture (NA) between 0.20±0.01 to 0.24±0.01 and wherein the octagonal cladding shaped Er/Yb doped fiber has a cladding absorption loss in a range from 1.9 to 2.8 dB/m at 915 nm and a core absorption loss in a range from 37 to 52 dB/m at 1530 nm.

8. The process as claimed in claim 1 , wherein the incorporating Er 2 O 3 , Yb 2 O 3 , P 2 O 5 , F, CeO 2 , Al 2 O 3 and B 2 O 3 comprises doping with GeO 2 in a range of 1.5 to 2.5 wt %, CeO 2 in a range of 0.12 to 0.191 wt %, P 2 O 5 in a range of 22.0 to 23.85 wt %, B 2 O 3 in a range of 0.95 to 2.51 wt %, F in a range of 0.025 to 0.030 wt %, Al 2 O 3 in a range of 0.356 to 0.525 wt %, Er 2 O 3 in a range of 0.41 to 0.605 wt %, Yb 2 O 3 in a range of 4.54 to 5.10 wt % and Yb/Er ratio in a range of 7.5 to 11.07.

9. The process as claimed in claim 8 , wherein doping B 2 O 3 along with P 2 O 5 reduces fluorescence life time of 4 I 11/2 level of Er while increasing the fluorescence life time of 4 I 13/2 level of Er; and
wherein Yb/Er ratio in a range of 7.5 to 11.07 suppresses Yb self lasing at 1.0 micron intrinsically.

10. The process as claimed in claim 8 , wherein the erbium and ytterbium (Er/Yb) co-doped multi-elements silica glass based cladding shaped fibers are configured to be used as fiber lasers and high power optical amplifiers generating 5.35 to 20 W power with lasing efficiency above >38%.

11. The process as claimed in claim 8 , wherein the erbium and ytterbium co-doped multi-elements silica glass based cladding shaped fiber is suitable for use in a radiation environment exhibiting <10% degradation of output power under low dose rates of 60 Co gamma radiation up to 6.0 Krad, wherein dose rate varies from 0.35 to 0.70 rad/s, and wherein the dose rate is equivalent to dose rates in free space.

Assignees

• Council Scient Ind Res

Inventors

• Chandra Paul Mukul
• Anirban Dhar
• Shyamal Das
• Mrinmay Pal
• Kumar Bhadra Shyamal

Classifications

• C03C2201/28

  containing phosphorus · CPC title

• H01S3/1618

  ytterbium · CPC title

• H01S3/06729

  Peculiar transverse fibre profile · CPC title

• C03B2207/66

  Relative motion · CPC title

• C03B2201/36

  doped with rare earth metals and aluminium, e.g. Er-Al co-doped · CPC title