RE: Best UV/V bang for buck

Hi Dave...

For UV on a jet-in-air sorter, there are two good options for
solid-state replacements - neither one cheap, unfortunately...

(1)  Newport Spectra-Physics makes the Vanguard, a Nd:YVO4 mode-locked
355 nm solid state laser that emits at 355 nm, with a fixed power level
of 350 mW.  We have one and love it - a 20,000 hour expected lifetime,
no water cooling, and it plugs into a regular 100V 20A outlet.	It can
be readily fitted into one of the laser slots on a Vantage or MoFlo,
although it should probably be considered a permanent replacement, since
it is almost as big as a water-cooled laser.  The power level is too
high for most applications, so we attenuate it down with 50% or 70%
beamsplitters - other labs have used a quarter wave plate optic to
produce the same effect.  The cost is high ($75,000 two years ago), but
I expect it to pay for itself over time with no changes to lab
utilities, no cooling water or chiller, no tube replacement, no
madness-inducing mirror alignments, etc.

(2)  JDS Uniphase makes the Xcyte (formerly made by Lightwave), which
operates on roughly the same principle as the Vanguard, and also emits
at 355 nm.  There are 20, 60, 100 and 150 mW versions of this laser - I
would get at least the 100 mW for a jet-in-air system.	The date sheet
is http://products.jdsu.com/assets/public/pdf/Xcyte_053105.pdf .

Both of the above UV lasers are pulsed lasers, with extremely high pulse
rates (>50 Mhz) - this high frequency level is absolutely necessary for
flow cytometry.  Since their rep rate is so high, they are often
referred at as "quasi-CW" in the product literature.  There are a lot of
other pulsed UV lasers on the market (usually designated Q-switched)
with lower frequencies that are not intended for and will not work for
flow - their rep rates are too low, usually in the 1-100 kHz range. The
Newport Spectra-Physics and JDSU units are the only commercially
available ones I am aware of with adequate rep rates. 

Near-UV or UV diodes are available that emit between 370 and 390 nm, but
the power levels from commercially available diodes appears to have
peaked at 20 mW - marginal for jet-in-air sorters.  I would not go this
route unless you have a cuvette system.

For violet (400 to 410 nm), you can now get single mode violet laser
diodes from Power Technology, Coherent, etc. in the 100 mW range.  This
should be fine for most applications.  Although lower power diodes will
work on jet-in-air system, sensitive applications like CFP-YFP FRET seem
to appreciate the extra power.

All of these lasers will require some baseplate and opto-mechanical mojo
to incorporate them into your cell sorter - hopefully your manufacturer
will be able to help you, or might even have one of them as a
purchasable option.  If you need help with parts and configuration, let
me know.

Enjoy,

Bill


-----Original Message-----
From: Dave Adams [mailto:davadams@med.umich.edu] 
Sent: Wednesday, December 19, 2007 10:27 AM
To: cyto-inbox
Subject: Best UV/V bang for buck

Greetings folks.  My core has a fleet of I-90s and 300s that are older
than my teenage
daughter.  When they go down, timeliness of repair is an issue, so I am
looking to pick
up a small UV (325-350ish, ~15mW) or violet (401-409nm, ~40-50MW) to
drop in whilst
repairs occur.	Anyone have any thoughts on "Best Bang for the Buck" in
the quick and
dirty replacement category?  I've no problem with HeCds or diodes.  

David Adams
University of Michigan Flow Cytometry Core

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