[Laser] Marlin Jones IR laser assembly - looks nice

Fri, 24 Jan 2003 17:32:38 -0500

There are 3 major absorption lines in the near IR ("I Band") and some minor
ones. They are primarily due to
modified harmonic resonances of the 2.7 um fundamental of the OH bond in
H2O:

725 nm major
759.4 and 762.1 nm minor (designated as "760 nm" due to close spacing).
822.85 nm major
940 nm major

I believe there is also a minor line or two around 850 nm (can someone
verify?)

These lines can cause anywhere from minor to substantial path loss over long
paths and being H2O related these losses would be humidity-dependent, just
like at mm-wave; 940 nm is the most significant of these lines in terms of
magnitude, followed by the 823 nm line.
Note that laser diodes can be easily tuned by varying temperature (or
stabilized by controlling same) so it might be wise to use this or some
other method to get your LDs to operate somewhere in the "windows" between
these bands if they don't already do so (exactly where doesn't matter, for
non-heterodyne detection).
In general, outside of these lines, NIR atmospheric transmittance is very
good, better than at visible, and with less scattering than the latter. The
longer wavelengths compared to visible permit somewhat greater penetration
of aerosols and particulates. Daytime insolation is much less than at vis,
although still great enough to require the use of filters.

73 de Jon W2MXW

-----Original Message-----
From: David D. Rea <[email protected]>
To: [email protected] <[email protected]>
Date: Thursday, January 23, 2003 7:40 PM
Subject: Re: [Laser] Marlin Jones IR laser assembly - looks nice

I'm a newcomer to this list, so forgive me if this has been brought up
before...

Does anyone have any good pointers to information regarding IR
propagation in air? I have been told by a friend and optics expert that
certain IR wavelengths don't like to go long-haul in air...

Also, is the primary wavelength mode of this laser module known?

Dave Rea
Rochester, NY

On Thu, 2003-01-23 at 16:26, Bob Williams wrote:
> That's a pretty cool combination.  Of course, they aren't small (4.5" x
4.5")
> nor are they particularly light (maybe a pound each).  But given what they
> have in them, I think they are a great deal if you are interested in, and
can
> work safely with, IR.
>
> Bob, AA1ZC
> FN31xk

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