a 15-m tube to generate 150 mW from
helium-neon.
Optical pumping of alkali-metal
vapors proved a disappointment.
Townes’s students at Columbia quickly
abandoned their cesium laser project
after Bell demonstrated the helium-neon
laser. The Pentagon didn’t think TRG’s
metal-vapor laser research was worth
classifying, so it was the only project
that Gould could work on after having
been denied a security clearance. After
painstakingly measuring population
inversions and optical amplification in
cesium, Steve Jacobs and Paul Rabinowitz detected oscillation on a 7.18-µm
cesium line in early 1962. Gould read
success on their faces when he walked
into his office one Monday morning,
saying, “Well, I’ll be damned. You
made it work!”
Molecular gas lasers
In 1963, Patel realized that molecular
lasers might convert more input energy
into light than atomic lasers because
molecular transitions were much closer
to the ground state. He started studying carbon dioxide because he thought
the multiple series of vibrational states
in three-atom molecules should allow
metastable states. He calculated that
CO2 should lase near 10 µm. “It did the
first time we tried,” he remembered in
a 1985 interview, recalling surprise that
his calculations were so close to the measured results. “It worked marvelously
well,” he said. “We got tens of milliwatts
on the first shot.” He then realized that
diatomic molecules should also work,
and he tried carbon monoxide, which
also lased.
Molecular nitrogen soaks up discharge energy efficiently, so Patel added
it to CO2, hoping for energy transfer
from the long-lived first excited state
of N2 to an upper level of CO2. Power
jumped from 10 mW with pure CO2 to
10 W from the gas mixture, the highest
CW power that had then been seen from
a laser. Adding helium also helped. “By
mid-1965, I had a 200-watt continuous-wave CO2 laser, which was more than
After painstakingly
measuring population
inversions and optical
amplification in ces-
ium, Steve Jacobs
and Paul Rabinowitz
detected oscillation on
a 7.18-µm cesium line
in early 1962.
enough power for anything you wanted
to do in the laboratory,” he recalled.
Reaching that power level and 20
percent efficiency was enough to interest
military laser-weapon developers because
it promised much better efficiency,
power and heat dissipation than solid-state lasers could deliver. The Pentagon
began classifying high-power CO2
research, so Patel, a non-citizen lacking
a clearance, decided to stay with spectroscopic research.
Laser companies and ion lasers
Gas laser development quickly spread
beyond Bell Labs, which, under terms
of a 1950s consent decree, had to license
its inventions to other companies. Soon
after being founded in September 1961,
Spectra-Physics teamed with the well-established Perkin-Elmer to manufacture
helium-neon lasers. They exhibited a
1.15-µm version selling for about $8,000
in March 1962, and sales jumped after
they introduced a red version six months
later. In June 1963, they sold their 75th
laser, and the two companies went their
separate ways.
Industry was also quick to recognize
the potential of 10.6-µm CO2 lasers for
noncontact cutting and drilling of nonmetals. Spectra-Physics founder Eugene
Watson saw the possibilities the first
time he saw a CO2 laser at a 1965 meeting, and when the Spectra-Physics board
refused to approve his plans to develop
CO2, Watson quit to establish Coherent
Radiation Laboratories (now Coherent
Inc.). The new company landed a contract to build a 100-W laser and set up
shop in Watson’s home. Within months,
they had the laser up and running, and
they demonstrated it by cooking paint
on the garage door of an obnoxious
neighbor across the street.
Laser companies contributed their
own innovations. Early helium-neon
lasers could be short-lived, so Spectra-Physics co-founder Earl Bell tried adding mercury vapor to the gas mixture
to extend the laser’s lifetime. He saw
a green glow near the cathode, which
hadn’t appeared in ordinary He-Ne
lasers, and he thought that might lead
