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Thulium-Doped Optical Fiber

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Thulium-Doped Single Mode and Large-Mode-Area Optical Fibers




  • Thulium-Doped Fiber for Fiber Lasers and Amplifiers
  • Broad 1.9 - 2.1 µm Emission Region
  • Core-and Cladding-Pumped Versions for up to 500 W Output
  • Single mode or Large-Mode-Area fibers Available

Features

  • Thulium-Doped Silica Fiber for ~2 µm Fiber Lasers and Amplifiers
  • Single Mode (SM) and Large-Mode-Area (LMA) Options Available
  • Core- and Cladding-Pumped Designs for 10 W - 500 W Operation
  • 793 nm, 1180 nm, and 1550 nm Absorption, 1900 - 2100 nm Emission Wavelengths

 

Applications

  • Plastics and Polymer Cutting, Engraving, and Welding
  • Excitation of Biological and Water-Based Samples
  • Industrial and Medical Lasers
  • Lidar Systems
  • Pumping Solid State Crystal Lasers

Thulium (Tm) is an excellent gain medium for 793 nm, 1180 nm, or 1550 nm pumping with emission at wavelengths above 1.9 µm. Hence, Thulium-doped silica fibers can be used to construct fiber lasers and amplifiers operating in the 1.9 - 2.1 µm wavelength range. Wavelengths above 2 µm are readily absorbed by water and polymers, making thulium-based lasers ideal for biological applications as well as cutting, engraving, and welding plastics.

These fibers have a high thulium concentration with additional doping that provides high efficiencies and prevents photodarkening. Thulium is unique in that a higher doping concentration improves efficiency through cross-relaxation, which is the excitation of adjacent ions for longer wavelength emission (see figure to the right). This property provides higher slope efficiencies as the dopant concentration increases. Thulium-based fiber lasers have been constructed with a maximum slope efficiency of 65%. The high Tm concentration also allows short device lengths while the low NA (single mode or few moded) core design provides robust beam quality. Additional dopants decrease the photodarkening usually observed with high thulium concentrations.

For additional information on the theory of thulium-doped fibers, see "Tm-Doped Fiber Lasers: Fundamentals and Power Scaling". The Publications tab above provides more information about active fibers.

We also offer polarization-maintaining versions of these fibers.

Connectorization and Splicing
We do not recommend connectorizing thulium fibers due to the high operating powers and potential for heat build-up. Matched passive fibers are available for splicing into these active fibers. Contact Thorlabs' tech support for more information.

TMSS single-clad fiber can be spliced similarly to standard single-mode fibers. The TMSD and TMLMAD double-clad fibers feature a pedestal design to provide a low NA core, preventing multimode operation. When splicing to a standard passive fiber, core alignment is critical, as the light must be confined to the core and not leak into the pedestal and first cladding. Many splicing machines can misinterpret the pedestal as the core, leading to alignment errors and high signal losses at the splice.

Item #TMSSTMSDTMLMAD
Nufern Item # SM-TSF-9/125 SM-TDF-10P/130-HE LMA-TDF-25P/400-HE
Optical Specifications
Core/Clad Type Small Core Single Mode, Single Clad Single Mode, Double Clad Low NA Large Mode Area, Double Clad
Operating Power 10 - 500 W
Pumping Method Core Pumping Cladding Pumping Cladding Pumping
Core Absorption 27.0 dB/m @ 793 nm
9.00 ± 2.00 dB/m @ 1180 nm
N/A N/A
First Cladding Absorption N/A 3.00 dB/m @ 793 nm
1.00 ± 0.30 dB/m @ 1180 nm
1.80 dB/m @ 793 nm
0.60 ± 0.10 dB/m @ 1180 nm
Emission Wavelength 1900 - 2100 nm
Cutoff Wavelength 1750 ± 100 nm - -
Mode Field Diameter (nominal) 10.5 µm @ 2000 nm - -
Core Numerical Aperture (NA)(nominal) 0.150 0.150 0.09
First Cladding NA N/A ≥0.46 ≥0.46
V Number at 2 µm 2.1 2.35 3.5
Operation at 2 µm Single Mode Single Mode 2 Modes
Geometrical and Mechanical Specifications
Core Diameter 9 µm 10 ± 1.0 µm 25 ± 2.5 µm
First Cladding Diameter 125 ± 1 µm 130 ± 2 µm (Flat to Flat)a 400 ± 15 µm (Flat to Flat)a
Coating Diameter 245 ± 15 µm - -
Second Cladding / Coating Diameterb - 215 ± 10 µm 550 ± 20 µm
Core-Clad Offset ≤0.50 µm - -
Coating Concentricity --
Coating Material Dual Acrylate Acrylate / Low Index Polymer Mixb
Proof Test Level >100 kpsi (0.7 G/m2)
Strip Toolb T06S13 T06S13 T18S25
  • These fibers feature a hexagonal cladding. Diameter is specified from the center of opposite segments of the hexagon.
  • For double-clad fibers, the second cladding / coating is a single layer of mixed acrylate / low index polymer, which is removed during stripping.

 


Core-Pumped SM Thulium Fiber, Single Clad,

  • Ø9 µm Core with Single Cladding
  • Core-Pumped Design for up to 10 W Output Power
  • Splicing Similar to Standard SM Fibers
  • 0.15 NA, Single Mode Operation

TMSS (Nufern Item # SM-TSF-9/125) is a single-clad, core-pumped thulium-doped fiber. It is ideal for lower-power fiber lasers with up to 10 W of output power. The core-pumped design with single cladding makes this fiber easy to splice.

 

Cladding-Pumped SM Thulium Fiber, Double Clad,

  • Ø10 µm Core with Pedestal and Double Cladding
  • Cladding-Pumped Design for up to 50 W Output Power
  • 0.15 Effective Core NA, Single Mode Operation
  • First Cladding with 0.46 NA for Pumping

TMSD (Nufern Item # SM-TDF-10P/130-HE) is a double-clad, cladding-pumped thulium-doped fiber. A pedestal design ensures a low NA and single-mode operation in the core, while the first cladding with 0.46 NA allows for easy pump light coupling. Extra care must be taken when splicing so that the light stays confined to the core or first cladding, and not the pedestal.

 

Cladding-Pumped LMA Thulium Fiber, Double Clad, 10-500 W Output

  • Ø25 µm Core with Pedestal and Double Cladding
  • Cladding-Pumped Design for 10 - 500 W Output Power
  • 0.09 Effective Core NA, Single Mode Operation
  • First Cladding with 0.46 NA for Pumping

TMLMAD (Nufern Item # LMA-TDF-25P/400-HE) is a double-clad, cladding-pumped thulium-doped fiber. A pedestal design provides a low NA for large mode area operation with approximately two modes in the core, while the first cladding with 0.46 NA allows for easy pump light coupling. Extra care must be taken when splicing so that the light stays confined to the core or first cladding, and not the pedestal.

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