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I'll look into it. I remember something about LBO being water sensitive, but not as much as BBO, I'll see what I can find. I'm finding lots of conflicting info. Also, I stand corrected on this one. My melles 561 does say it uses an LBO but does have dessicant. However digging into this other 577 there is only an oxygen absorber, as well as in the green. there are two in each. I thought one was silica gel, it is not.
Edit:
Found this:
Laser Focus World - March, 2003
BBO, LBO
The introduction of beta barium borate (BBO)
and lithium triborate (LBO) in the late 1980s
provided a combination of nonlinear
efficiency and high damage
threshold that significantly
accelerated NLO development. Both materials are
transparent well into the ultraviolet. Lithium
triborate has the highest damage threshold of
all commonly used NLO crystals, making it the
material of choice for high-a
verage-power applications.
Both materials are used to produce wavelengths
shorter than 300 nm, but LBO has a lower
birefringence that limits its UV phase-matching
to certain combinations of longer wavelengths. It
is often "temperature tuned" for phase-matching;
that is, heating the crystal to a temperature at
which its refractive index is the same for the
fundamental and harmonic light. Compared to BBO,
it has a significantly wider acceptance angle.
The birefringence of BBO gives it excellent phase-match
capabilities, enabling it to produce
tunable radiation from the near infrared into the
UV. It is commonly used in parametric conversion,
and for the generation of higher harmonics of neodymium
lasers. Both crystals are slightly hygroscopic, and are relatively soft.
Adding cesium to LBO produces CLBO, a soft a
nd hygroscopic material that nevertheless has
grown in popularity for producing shorter wavele
ngths. The combination of CLBO properties
allows a severalfold improvement in NLO efficiency.
