Lasers wet or dry

Howard Shapiro hms at shapirolab.com
Wed Sep 13 06:26:44 EST 2000


Simon Monard asks:

>Has anyone compared directly air cooled and water cooled lasers for 488
>excitation. I
>am thinking of replacing my aging 100mW ILT with a larger water cooled unit.

In general, water-cooled lasers are less noisy (i.e., the light output
fluctuates less, typically 0.1 or 0.2% RMS versus 1% RMS for air-cooled
argon lasers).  This is a factor in scatter measurement from small
particles; it is easier to detect bacteria above background using the same
power when you use a water-cooled instead of an air-cooled laser.  In
practice, the problem doesn't arise in either scatter or fluorescence
measurement from mammalian cells.  If your system works well with 100 mW
from an air-cooled 488 nm laser, another air-cooled laser with equivalent
or higher power will be fine, and save on plumbing and electricity.  It
will also keep your lab cozy warm on those cold upstate New York winter
days.  Years ago, Mike Loken, Dave Houck et al showed that you could get
full excitation of fluorescein, etc. at 488 in a FACS with 100 mW or less,
so you probably wouldn't need the water-cooled laser for more power at that
wavelength.  Of course, if you need UV from an ion laser, you'll have to
get a large, water-cooled one.

-Howard




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