Plasma Outside Deposition Service
Standard Fluosil® preforms are made using our Plasma Outside Deposition (POD) process. This process can also be readily utilized for depositing highly fluorine doped layers onto substrate materials, both solid and tubular.
We offer this flexible process to customers who need a highly fluorine doped cladding outer layer for their own specially designed silica products such as core rods and substrate tubes. The POD service is well suited for the following applications:
- Cladding rods or substrate tubes with special cross sections such as square, hexagonal, or D-shaped
- Producing double and multi cladding structures, e.g., for fiber laser preforms
- Cladding special core materials such as rare earth doped fused silica rods and rods with very high internal stresses
Performance of POD Cladding
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Fluorine content [ppm]
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0 ... 70,000
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Refractive index*
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0 ... -23 x 10-3
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Numerical aperture (NA)**
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up to 0.26
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Cladding to substrate diameter ratio (CCDR)
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no upper limitations
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Minimum diameter of substrate material
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10mm
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Minimum length of substrate material
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substrate diameter dependent
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Maximum length of substrate material
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substrate diameter dependent
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* Difference to un-doped fused silica (Heraeus standard)
** For un-doped silica substrates
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The cladding to core diameter ratio (CCDR) is defined for cylindrical geometries by the ratio of the cladding outside diameter to the substrate material diameter. Though the POD process is very flexible, non-uniformity in cladding thickness for non-circular rods (D-shaped, square, etc.) has been observed. Therefore, customized cladding thickness specifications have to be defined for non-circular geometries prior to the deposition services.
Flexibility in refractive index cladding profiles
Due to the flexibility of the POD process, simple or complex refractive index cladding layers can be deposited on the outer diameter of customer-supplied substrate materials. A uniformly doped cladding, referred to as a “U-type,” can be applied with fluorine concentrations from 0 to 7%. In contrast, double or multiple cladding structures, referred to as “S-type,” consisting of layers of differing indices of refraction, can be deposited to create complex cladding profiles. Customer-specific substrate materials can also be overclad either by an un-doped F300 tube or a fluorine doped Fluosil® tube.
