|
|
|
|
|
|
| Home » Laser Crystals » Nd:Yag Laser Crystal » Nd:Yag Laser Rod Manufacture » Request Quote | Search Roditi |
Click here - Immediately Available Stock Specifications >>
Laser rod "blanks" are extracted from completed boules using a diamond core drill; for slabs, a slicing saw is used tocut out the rough rectangular shape. In either case, the rough finished blanks are then sent out for the finishing operations of precision grinding to final size, polishing, and anti-reflection coating. There is the option of purchasing finished rods directly, or purchasing unfinished "blanks" and using the fabricator of your choice.
When single mode (TEM00)
operation is required, the selection of the proper dopant concentration is critical
to the system's operation. Generally, the optimum laser rods for such systems
have Nd doping concentrations in the range of 0.5 to 0.8 atomic percent. The
final selection is based on many specific system design factors such as lamp
versus diode pumping, mode stability, polarisation, beam divergence, etc.
In any design
calculation or evaluation of the
Nd:YAG laser, the thermal loading
of the rod must be considered.
The objective is a careful balance
of output power requirements versus
the tolerance for thermal effects.
Years of experience in
Nd:YAG and other laser materials
enables us to offer useful assistance
with the material selection to
create a successful beam profile
and optimise the performance of
your laser.
One of the most important advances in Nd:YAG production in recent years has been the trend toward larger diameter boules.Internal strain in the grown boule is the principle cause of optical distortion in finished laser rods more than a few tens ofmillimeters in length (in shorter rods, the quality of the end finish is more important). Larger boules have significantly lower strain levels over much of their cross section resulting in significantly lower optical distortion in finished rods.An additional advantage of larger boules is reduced cost. The cross-sectional area is increased while the linear growth rateremains comparable, resulting in an increased rate of material growth.
At large diameters, Nd:YAG is more sensitive to process parameter fluctuations and obtaining high yields of good product is more difficult. But as a result of improved control electronics and computerization of the growth process, growth rate fluctuations can be maintained well within tolerance to provide high yields of good product at large diameter.
In neodymium doped yttrium aluminum garnet, neodymium substitutes for yttrium in the crystal lattice. However, because neodymium is larger than yttrium, this substitution does not
occur readily. In fact, the concentration of neodymium in thecrystal is only a small fraction of its concentration in the melt. Since the growing crystal is continually rejecting neodymium, the concentration of the melt (and hence the crystal) increases as the growth progresses. To minimize this effect it is necessary to use a large crucible and to pull only a small fraction (typically20-30%) of the total material available.
The upper graph shows the concentration of neodymium increases as a function ofmelt fraction pulled. Most boules are grown with an average Nd concentrations of 0.80%Nd and 1.10%Nd. However, other average concentrations are available and we are able to offer material for most specialist applications
The Nd concentration profile for each is illustrated in the lower graph. The composition is engineered to provide the specified average concentrationin 200 mm lengths. Lengths up to 250 mm can be provided with slightly higher average Nd concentrations. For material less than 200 mm, the average concentration will vary depending on from where in the boule the material is cut.
Each individual laser rod shipped is supplied with data including the average Nd concentration and the change in concentrationover the rod's length. Standard tolerances for various rod lengths are published.