481-7). This was capped by
a spectacular photograph on
the cover of Electronics (S.F.
Jacobs. “The Optical Heterodyne, Key to Advanced Space
Signaling,” Electronics 36,
29-31, 1963).
Also, as Jeff Hecht correctly noted, the mercury ion laser
never found a commercial
market because it didn’t operate continuously. However, it
did offer very high gain in a
large-diameter visible laser.
Earl Bell provided us at the
Optical Science Center with
Brewster-angle gain tubes
so that we could play with a
hand-held corner reflector to
check out Gordon Gould’s
self-aligned resonator idea. See
G. Gould et al. “Self-aligning
Fabry-Perot Interferometer
for Use as a Laser Resonator,”
J. Opt. Soc. Am. 51, 1467
(1961), and P.J. Rabinowitz et
al. “Cube Corner Fabry-Perot
Interferometer,” J. Opt. Soc.
Am. 52, 452-3 (1962).
Steve Jacobs
Tucson, Ariz., U.S.A.
sfjacobs@cox.net
and kicking. It might be in its
senior years, as I am, but it is
not yet ready for a tombstone.
Furthermore, it does not
require the high operating
temperature that Wilk suggests is necessary for metal
vapor lasers. According to the
Physics Today Buyers Guide,
there are three companies
offering helium-cadmium
lasers for sale, and there are
still applications for which this
laser meets the job requirements better than any other
type currently available.
I would also like to make
an addition to the great article
that Jeff Hecht wrote about
the history of continuous wave
(cw) gas lasers in the same
issue. Marvin Klein and I
jointly discovered and developed the cw helium-selenium
laser at Bell Labs in 1973.
William Silfvast
St. Helena, Calif., U.S.A.
silfvast@creol.ucf.edu
Jens Petersen
Metal Vapor Lasers:
Not Dead Yet
I don’t know how someone
would feel if they saw a tombstone with their name on it,
but I note that
Steve Wilk, in
his article on
defunct lasers,
suggested such
a demise for
metal vapor
lasers (
January 2010). I
must inform
him that
the helium-cadmium laser
is still alive
Eyeing Shrimp Eyes
I enjoyed your article on
polarizing shrimp vision
(January 2010). Yvonne
Carts-Powell writes that “no
one knows exactly why the sea
creatures need such complex
eyes; perhaps they use the
added contrast that comes
from polar-
ization to
navigate, find
food or evade
predators.”
optimal polarization vision—
that is, each eye is assessing
Stokes parameters by making
the appropriate combination
of left- and right-circular, as
well as horizontal, vertical,
diagonal, and anti-diagonal
linear polarization measure-
ments from separate cells.
This goes well beyond simple
contrast enhancement: Opti-
mal polarization vision is
analogous to the improvement
afforded by stereo over mono
vision in terms of increased
information capacity.
Please direct all correspondence to the Editor, Optics & Photonics
News, The Optical Society, 2010 Massachusetts Ave., N. W.,
Washington, D.C. 20036. E-mail: opn@osa.org.
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