One stop on our Baltic cruise a couple weeks ago was
Stockholm, where we took an afternoon water tour of this
impressive city and its surroundings. The tour boat passed by the
hall where the Nobel Prizes ceremonies are held. Our guide said
that when Alfred Nobel died there was an understandable
reluctance on the part of his relatives to accept the provisions of
his will, which dictated that his estate be used to set up a fund to
award prizes “… to those who, during the preceding year, shall
have conferred the greatest benefit on mankind.” According to
our guide, the local politicians also were not impressed and
considered it a stupid idea and it took six years before the Nobel
Prizes became a reality. The winner of the first Nobel Prize in
physics in 1901 was Wilhelm Roentgen, for his discovery of X-
rays. Coincidentally, after our cruise, we were in the famed
Concertgebouw in Amsterdam and I noticed that encircling the
concert hall in large letters, under the upper level of seats, were
the names of famous composers, e.g., Wagaanar (sic),
Tchaikowsky, Dvorak, etc. Strangely, among these composers
was the name Roentgen. I believe that this is the same Roentgen
and there must be a story behind his inclusion in this unusual
setting. If anyone knows the answer please let me know.
In April, another Nobelist, Arthur Schawlow, died at the age of 77.
Schawlow was born in Canada and, after getting his doctorate in
physics from the University of Toronto, went to Columbia
University to work as a post doc with Prof. Charles Townes.
Townes had invented the MASER, a novel device for producing
“coherent” microwaves. Schawlow proved such a good physicist
that Townes wanted to keep him on at Columbia but Schawlow
crossed him up by marrying Townes” sister. Fortunately for Bell
Labs, Columbia frowned on the nepotism if Townes hired his
brother-in-law and Schawlow left Columbia to join Bell Labs to
work on superconductivity. However, in their spare time, the two
brothers-in-law still got together trying to figure out how to extend
Townes” maser principles from the microwave to the optical region.
They finally came up with an idea for constructing a “LASER”
(Light Amplification by Stimulated Emission of Radiation),
published a paper in 1958 and received a patent in 1960. Since
Schawlow was working for Bell Labs and Townes was also a
consultant for Bell Labs (he had worked there earlier), neither
received royalties for their invention. I imagine, however, that
Schawlow got a good raise that year. In 1964, Townes got a
Nobel Prize for his maser and laser work and in 1981 Schawlow
received his for contributions to laser spectroscopy. Of course,
the Nobel Prizes added some spare change to the Schawlow and
Townes family coffers.
Why all the fuss about the laser? Essentially, the laser involves
generating a beam of light composed of photons which are all in
sync, kind of like a bunch of soldiers marching in step, all in the
same direction. The laser design of Schawlow and Townes involved
a long tube of a material with mirrors on both ends. In this
arrangement, the photons bounce back and forth between the
mirrors. When one of these photons hits an atom that has been
“pumped up” by an external light source, the pumped up atom emits
another photon of the same wavelength or color. (This is the
“stimulated emission of radiation”, a concept traceable back to none
other than Einstein, who received his own Nobel Prize for his work
on photons and light emission, not for E=mc2 or his theory of
relativity!) One consequence of this mirror arrangement is that the
number of photons marching in step keeps multiplying (the “light
amplification”), while those that are not in step wander off in
different directions and are lost. How does the laser light get
out? One of the mirrors is made to be partially transparent and a
light beam of in-step photons emerges from this end. The laser
light beam does not spread out like the light from ordinary light
bulb but stays focused in a narrow beam. Another feature of the
laser is that the light can be very “pure” in color, that is, the
photons all have pretty much the same wavelength. Also, by
concentrating the light in a narrow beam, the energy can be quite
intense. This is kind of like when as kids we used a magnifying
glass to focus the sun”s rays to start a fire with a piece of paper or
wood; easier than the Boy Scout method of rubbing two sticks
together.
Schawlow and Townes only published the principles for laser
operation but had not actually constructed one. Workers at Bell
Labs and many other laboratories were feverishly trying to be the
first to make a laser. Many different approaches were tried and it
was Theodore Maiman at Hughes Research Laboratories, working
on his own, who in 1960 first demonstrated laser action, in a ruby
crystal. (Those of you who think of ruby as a gemstone would be
impressed to see synthetic ruby crystals a foot or two in length and
over an inch in diameter!) Maiman”s laser operated only in pulses
and there followed a contest to see who would make the first
laser to operate continuously. In 1960 and 1961, workers at Bell
Labs demonstrated continuous laser action in a helium neon gas
laser and in calcium tungstate as well as in ruby. Over the years all
kinds of materials and structures have been used to make lasers
including modifications of the light emitting diode structures we
discussed in an earlier column. In these semiconductor lasers the
pumping is done not by light but by an electric current.
Today, we all know or have heard of the multitude of uses to which
the laser has been put. We discussed in an earlier column lasers in
your compact disk player. The applications in the medical field are
myriad. I myself have had laser surgery on one eye and have
suffered no ill effects (though a retinal specialist later informed me
that my surgery was not needed!). There are many laser treatments
for various skin problems, most of which rely on the selectivity of
the reaction of the particular skin problem to particular colors of
the laser beam. The sale of the ubiquitous red laser pointer used
by speakers is now being restricted in some localities because of
the possibility of inflicting eye damage in the hands of a careless
youngster or even a criminal type. Surveyors can now measure
distances to remarkable precision with laser devices. Just
beginning to emerge is the use of lasers in the dental chair. If
successful, the amount of pain and apprehension that will no
longer exist for dental patients will be worth every cent spent in
laser development! The silicon chip may become even faster
when tiny lasers are incorporated on the chips and the signals are
carried at the speed of light around the integrated circuits.
Back to Schawlow, who left Bell Labs in 1961 to go to Stanford
University. He had a good sense of humor and I remember him
giving a lecture on lasers at Bell Labs in which he answered a
question about the possibility of using lasers as death rays.
Schawlow”s reply was that it was indeed possible but that he had
perfected the anti-laser defense. He then showed a picture of a
knight in his shining armor, which would reflect the light beam
with no damage to the wearer! One obituary mentioned that
while at Stanford he loved to give popular demonstrations of the
laser. One of these involved shooting the beam from a “ray gun”
laser through a transparent balloon and popping another, darker
balloon inside the first one. This illustrates the selectivity of the
interactions of laser light of different wavelengths (colors). For
example, if the outer transparent balloon is green and a green
laser is used, the green light is not absorbed by the green balloon;
otherwise the balloon would not be green! If the balloon inside is
deep red, this means that red light is not absorbed but the green
light is. This heats up the balloon and it pops.
A very interesting sidebar on the laser story is the patent controversy
that erupted after the Schawlow-Townes patent of 1960. Gordon
Gould, a 37-year-old graduate student working with another
professor at Columbia, claimed that he had in his notebook a
notarized entry in 1957 describing the laser idea prior to the
Townes-Schawlow work. Gould apparently was under the
impression that he had to come up with a working laser before he
could file for a patent and did not file until 1959, after leaving
Columbia to join TRG to concentrate on developing his laser.
Gould”s efforts to sustain his claim were turned down by the courts
in the 1960s. However, he did not give up and his fight to prove his
claim became a well-publicized media event as a David and Goliath
encounter. Finally, in 1977, Gould did indeed receive a patent on
optical pumping of lasers. Ironically, this was some 17 years after
the 1960 patent of Townes and Schawlow and their patent
presumably was expiring! Over the next decade or so, Gould was
awarded three more patents dealing with various laser designs and
also with laser applications. I”m not sure what the situation is today,
but we used to joke that a patent attorney wasn”t very good if he got
the patent granted on the first try, the reason being that the sooner
the patent was granted, the sooner it expired. Certainly, from that
standpoint, Gould had the best of all possible worlds with some of
his patents still in force today and the burgeoning use of lasers
worldwide. If he is still living, Gould will be 79 on July 17 and I
would imagine still benefiting from laser royalties.
Today, laser research is still alive and well. Bell Labs, for
example, is working on the “quantum cascade” laser (likened to
an electronic waterfall) and “bow-tie” lasers so small that
hundreds can fit on the proverbial head of a pin! Another
amazing development involves the demonstration of a system in
which a single laser generates pulses of 206 different “colors,”
each pulse lasting less than a trillionth of a second. Because
different colors travel at different speeds, the result is a bunch of
“rainbows”, packets of 206 colors, traveling down an optical fiber
with the potential to carry enormous amounts of information (TV,
movies, data, etc.), all on a single line. Now, if only my feeble
brain could be programmed to handle the information already
inundating me!
Allen F. Bortrum
