laser dyes. As Schawlow noted, sodium
fluorescein isn’t very toxic. Neither, for
that matter, are coumarin dyes. One
expert I spoke with noted that some
dyes, such as the sulforhodamines, exit
the body quickly and would arguably be
a better choice if you were determined
to drink your dye. (I want to emphasize that I am NOT advocating this. I
strongly insist that you do not try this
at home.)
All of these dyes are soluble and
lasable in ethanol, so you could, in principle, drink them. In fact, a droplet of
alcohol containing the dye would itself
constitute a complete laser, as Hänsch
showed. With the light totally internally reflecting from the interior droplet
surfaces, the entire laser is edible. The
actual toxicity of these dyes has not been
fully established, however. Certainly
most laser dyes are toxic, especially the
cyanide-based ones. Also, these examples of laser dyes in gelatin or ethanol
don’t stray far from the work of Hänsch
and Schawlow.
Salty lasers
One new possibility is a color-center
laser, which uses point defects in crystal
lattices as broadband, tunable laser sources. Granted, many of these crystals are
minimally soluble, indigestible crystals
such as lithium fluoride or even diamond.
But most of the lasing defects are in
potassium chloride or sodium chloride.
Two of the crystals used by the only
commercial color center laser were
potassium chloride, which is certainly
edible when ground up or licked; in
fact, it’s used as a salt substitute. Most
of the color centers involve impurities
introduced into the crystals, but these
are at low concentrations—typically
about 1 percent—and most are benign,
being other alkali metal ions. However,
both KCl and NaCl crystals are host to
defects that don’t involve impurities.
Besides defect lasers, there are also
laser materials in which the salt crystal
acts as a host medium for lasing molecular ions. My own work on superoxide
ions in salt crystals is an example.
“One-Drop-Only” dye laser, a precursor of
the edible laser.
One new possibility is
a color-center laser,
which uses point
defects in crystal
lattices as broad-band,
tunable laser sources.
Unfortunately, there aren’t too many
other edible crystals. However, there are
alkali halide crystals, and other color
centers in some of those (such as rubidium chloride or potassium bromide).
No one, to my knowledge, has reported
laser properties in defects or impurity
centers in, say, rock candy, or crystallized
proteins. Perhaps this column will spur
someone to take up the challenge.
Liquid lasers
What about liquids? Our choices here
are limited as well. Water and ethanol are potable, but most other fluids,
including organic liquids, are not. You
can drink small amounts of glycerine,
but I haven’t been able to lase them,
even with the inclusion of dyes. Aside
from organic compounds and their
perhalogenated analogs, and silicones,
most substances that are liquid at room
temperature are either highly toxic or
highly reactive in the presence of organic
liquids and water.
However, water and alcohol in vapor
form meet my guidelines: Although you
can’t consume them as a vapor, you can
condense and drink them without making any other alteration. There are about
two dozen lines on which water vapor
will lase continuously between 2 and
350 µm. And ethyl alcohol has been
found to lase at 396 µm. There must be
others. Methyl alcohol has more than
100 lasing lines in the infrared. Perhaps
this is a fruitful area for future research.
And what about the fabled gin-and
tonic laser, another rumor I’d heard during my graduate school days? According
to D.A. Jennings, K.M. Evenson and
J.J. Jimenez, all working at the NIST
laboratory in Boulder, Colo., U.S.A.,
in 1975, the “…ethyl alcohol line lased
very well on vodka, gin and rum, but it
lased on only one line and rather weakly
compared with methyl alcohol. It is quite
obvious that there are better uses of ethyl
alcohol.” I’ll drink to that. t
Stephen Wilk ( swilk@comcast.net) is an optical
engineer based in Saugus, Mass., U.S.A.
[ References and Resources ]
>> W.S. Benedict et al. “The water vapor
laser,” IEEE J. Quantum Electron. 5( 2),
108-24 (1969).
>> T. W. Hänsch et al. “Laser action of dyes
in gelatin,” IEEE J. Quantum Electron. 7,
45-6 (Jan. 1971).
>> J.G. Kepros et al. “Experimental evidence
of an X-ray laser,” Proc. Natl. Acad. Sci.
USA, 69( 7), 1744-5 (1972).
>> D.A. Jennings et al. “New CO pumped
2
CW far-infrared laser lines,” IEEE J.
Quantum Electron. 11, 637 (1975).
>> A. Kues and G.A. Lutty. “Dyes can be
deadly,” Laser Focus 11( 5), 59–61 (May
1975).
>> S.R. Wilk et al. “Laser characteristics
of KNL:O ,” Opt. Comm. 47( 6), 404-6
2
(1983).
>> J.F. Pinto et al. “Stable color-center
laser in K-doped NaCl tunable from 1. 42
to 1.76 µm,” Opt. Letters 10( 8), 384-6
(1985).
>> T. W. Hansch et al. “Edible lasers and
other delights of the 1970s,” Opt. Photon.
News 16( 2), 14-6 (2005).
