Re: Large Fused Silica Lenses


"Farsang" <youzpalang@xxxxxxxxxxxx> wrote in message
news:1185240931.164593.66280@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Hi:

We'd like to expand 12 mm dia. beam to 50 mm dia beam using a Galilean
beam expander
configuration (high power beam). Wavelength = 1.064 um

Are there catalog lenses with dia.> 50 mm made of Fused Silica? I
searched but couldn't find
any.

Is there a better method to do this and what other material beside F-
Silica we could use.? The wavefront should be good to give us a good
beam quality 7Km away.
(Beam Quality = 1/SQRT(Strehl Ratio).


If you need to guarantee a good beam quality, then it is best to use custom
lens elements, not catalog elements, as the manufacturing tolerances on the
latter are usually inadequate. For very high pulse energies, fused silica
is generally considered the best material to avoid damage problems. If you
aren't at that limit, then using a higher index material will make it easier
to correct aberrations. Aberrations get worse as you need to make the beam
expander shorter -- if you can make it very long, then maybe you will have
no problem with aberrations other than from manufacturing errors.

Of course, for your larger lens, damage considerations are most likely
irrelevant. If you haven't yet done so, look at what CVI Laser offers in
the way of high damage threshold lenses for the negative element of your
Galilean. They could make your large lens, or your whole beam expander, but
so could lots of others.


.

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