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What is a fluoride fiber ? (Fluoride Glass Fiber Technology)

to non-doped SMF
to non-doped MMF
to RE-doped SMF
to RE-doped DCF
to AlF3-based FF
 Fluoride Fiber (FF) is multi-composite glass optical fiber composed of several heavy metal fluorides.
ZBLAN fiber ( ZrF4-BaF2-LaF3-AlF3-NaF ) and AlF3-based fiber(AlF3-BaF2-SrF2-CaF2-MgF2-YF3) are well known. Compared with silica fiber, FF has many unique characteristics in wide operating wavelength range and high emission efficiency when rare-earth elements are doped into.
>Fluoride fiber fabrication
 Fabrication of FF with low loss is very difficult, because CVD technique popular in silica fiber manufacturing can not be applied due to lack of gaseous raw materials. Over the long years studying, FiberLab Inc. has established its own techniques to manufacture both kinds of fluoride fiber, ZBLAN fiber and AlF3-based fiber with low loss less than 0.1dB/m. We, FL, have been continuing our R&D activities to improve our own manufacturing technique to achieve further low loss value by removing impurities and other origins.
>ZBLAN fiber for NIR/IR spectroscopy
 Fig.1 shows loss spectra among three different kinds of glass fibers. Compared to other fibers, ZBLAN fiber has the widest transmission range from 0.4 to 4μm. Thus, ZBLAN fiber is applied to optical guides for NIR and IR spectroscopies.
                  Fig.1 Loss spectra of three kinds of fiber
>AlF3-based fiber for 2.9μm Er:YAG laser power delivery
 Though IR transmission range in AlF3-based fiber is not as wide as in ZBLAN fiber, it has low optical loss at 2.94µm, higher laser damage thresholds, better mechanical properties and more excellent durability against moisture(See Table1). Thus, AlF3-based fiber is applied to optical guides for Er-YAG laser delivery.
Table1. Comparison of AIF3-based glass and ZVLAN glass
 Properties AlF3 glass ZBLAN glass
Optical  Transmission range 0.3~3.5µm 0.35~4.0µm
Refractive index(nd) 1.46 1.51
Thermal  Glass transition temperature(Tg) 367°C 265°C
Thermal expansion(a) 186x10-7/°C 200x10-7/°C
Chemical  Water solubility(Dw) 0.27wt% 29.2wt%
Acid solubility(Da) 0.69wt%* 32wt%*
Physical  Density 3.85g/cm3 4.50g/cm3
Mechanical  Young's modulus(E) 66GPa 53GPa
Knoop hardness(HK) 3.1GPa 2.2GPa
>Emission of rare-earth element doped ZBLAN Fiber
 Excellent emission characteristic is huge advantages of ZBLAN fiber, when rare earth element doped into. The pictures show the emission of ZBLAN fibers doped with Tm, Er, or Nd. As seen in the examples, ZBLAN fibers emitt the light at various wavelengths including the visible, near-infrared, and mid-infrared regions. The reason is because the fiber is composed of the heavy metal fluorides which are less susceptible to the influence of non-radiative transition by phonons.
 Fig.2 shows emission wavelengths of rare-earth element doped fiber. While silica fibers emit only near-infrared light as we marked "  ", ZBLAN fiber covers the wider range of infrared lights and visible lights. In particular, the emission of 1.3 and 1.4 μm bands in the near-infrared region, which is significant in optical communication, can be obtained from fluoride fibers. Emissions in infrared region can be obtained only from ZBLAN as well.
To achieve better performance of emission characteristic, we, FL, have been developing glass composition and the best design of fiber parameters.
 Based on this emission characteristic, FL has been providing our own products, such as Optical Amplifiers, ASE Light Sources, Fiber Lasers, and other optical devices.
               Fig2. Emission of rare-earth element doped ZBLAN fiber
Our Value Proposition
Development of optical devices based on rare-earth doped fluoride fibers
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