fluoride fiber ZBLAN fiber AlF3-based fiber

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Fluoride Fiber(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.
However, 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.

>IR transmission

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.
Fig.1 shows loss spectra among three different kinds of glass fibers. Compared to silica fiber, minimum losses of FF are much higher, but they cover much wider wavelength ranges. Thus, FF is applied to optical guides for NIR and IR spectroscopies.. 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.

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.

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
Optical	Refractive index(nd)	1.46	1.51
Thermal	Glass transition temperature(Tg)	367°C	265°C
Thermal	Thermal expansion(a)	186x10-7/°C	200x10-7/°C
Chemical	Water solubility(Dw)	0.27wt%	29.2wt%
Chemical	Acid solubility(Da)	0.69wt%*	32wt%*
Physical	Density	3.85g/cm3	4.50g/cm3
Mechanical	Young's modulus(E)	66GPa	53GPa
Mechanical	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.
Fig.2 shows emission wavelengths of rare-earth element doped fiber. Silica fiber gives out emission but limited to the range only in near infrared region, as we marked "

".
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. Besides, ZBLAN fiber covers the wider range of infrared lights and visible lights.
Also, emission of both 1.3 um and 1.4 um wavelength band is available by using none but ZBLAN fiber. Both wavelength bands are popular and major in optic fiber communication field.
To achieve better performance of emission characteristic, we, FL, have been developing glass composition and the best design of fiber parameters.

Our Value Proposition

Development of optical devices based on rare-earth doped fluoride fibers
(PROCEEDINGS OF SPIE Vol.4645)
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