Laser-heated pedestal growth
Laser-heated pedestal growth (LHPG) or laser floating zone (LFZ) is a
Advantages
The main advantages of this technique are the high pulling rates (60 times greater than the conventional
The geometric shape of the crystals (the technique can produce small diameters), and the low production cost, make the single-crystal fibers (SCF) produced by LHPG suitable substitutes for bulk crystals in many devices, especially those that use high-melting-point materials.[6][7] However, single-crystal fibers must have equal or superior optical and structural qualities compared to bulk crystals to substitute for them in technological devices. This can be achieved by carefully controlling the growth conditions.[8][9][10]
Optical elements
![](http://upload.wikimedia.org/wikipedia/commons/thumb/1/1b/LFZ.svg/300px-LFZ.svg.png)
Until 1980, laser-heated crystal growth used only two laser beams focused over the source material.[11] This condition generated a high radial thermal gradient in the molten zone, making the process unstable. Increasing the number of beams to four did not solve the problem, although it improved the growth process.[12]
An improvement to the laser-heated crystal growth technique was made by Fejer et al.,
Convection speed
A feature of the LHPG technique is its high convection speed in the liquid phase due to Marangoni convection.[15][16] It is possible to see that it spins very fast. Even when it appears to be standing still, it is in fact spinning fast on its axis.
See also
References
- ISBN 978-0-444-86919-7.
- ISBN 978-3-540-74182-4.
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- S2CID 250907003.
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- S2CID 95249182.
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- doi:10.1063/1.88172.
- ^ Haggerty, J.S. (1972). "Production of fibers by a floating zone fiber drawing technique, Final Report". NASA-CR-120948.
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(help) - ISBN 978-0-89252-355-9.
- PMID 20125635.
- S2CID 120615103.
- ^ The video presented in the following reference shows the liquid phase convection during lithium niobate (LiNbO3) fiber pulling using a very small piece of platinum wire inside the liquid that is allowed to spin. "Convection in Laser Heated Pedestal Growth technique". YouTube. 23 July 2008.