Lynn Savage, Features Editor, email@example.com
For millennia, scholars in the old
and new worlds have realized that their efforts depend largely on the works of those
who came before. The “eureka!” moments experienced by scientists and
other observers of nature do arise, but there must exist first a foundation of knowledge
that has been passed down from earlier investigators.
This has never been more true than in the world of laser technology,
celebrated globally on the 50th anniversary of the firing up of the first ruby beauty.
It would be shocking to find someone in the field who is unaware of names such as
Maiman, Townes, Schawlow and Basov, but the pioneering developments of today depend
on the efforts of many more innovators who toiled at the same time, or even earlier.
Entire books have been given over to untangling the web of published
papers, patents (submitted, approved or contested), conference presentations, lab
tests and handwritten, notarized paper journals that comprise the forensic evidence
of who did what, when. The following is a brief tour of some of the bright lights
who, over the past five decades, have brought the laser to prominence. For a comprehensive
timeline of the laser’s history, see “A Trip Through the Light Fantastic,”
Though no one could have known it at the
time, Charles Fabry and Alfred Perot became forever tied to the story of the laser
through the creation of the interferometer in the late 19th century. Two perfectly
parallel mirrors were the key to stimulating both solid and gaseous molecules to
produce an inverted population. Without the Fabry-Perot device, you’re just
exciting particles randomly and to no avail.
Charles Fabry (Library of Congress)
A couple of decades later, in 1917, while
he was tinkering with other concepts that also caused a stir, Albert Einstein became
the first theoretician to stipulate ways in which atoms might interact with photons,
including the practicality of producing the stimulated emission of light.
Alfred Perot (Wikimedia Commons)
Scientists in the US, Europe and the Soviet
Union picked at the edges of light-and-matter interactions for several years, with
two global wars causing deep distractions. In 1940, the young physicist Valentin
A. Fabrikant of the Moscow Power Institute described how population inversion –
having more molecules excited than not – would necessarily lead to “molecular
amplification,” aka stimulated emission. He applied for a patent (in the USSR)
for “a method for the amplification of electromagnetic radiation,” on
June 18, 1951. The application was rejected at first, but was eventually approved
in 1959 – too late for most of the acclaim he deserved.
Albert Einstein (Wikimedia Commons)
While Fabrikant’s patent churned
through the Soviet bureaucracy, Joseph Weber of the University of Maryland made
the first public description of coherent microwave radiation in 1952.
Nikolai G. Basov (Wikimedia Commons)
Then, from within the heavy-laboring crowd
of microwave specialists, came Charles Hard Townes, who, in 1954, conceived and
built the very first operating maser, using ammonia gas as the excitation material.
He also coined the term, which is an acronym for “microwave amplification
by the stimulated emission of radiation.” Townes, who cut his teeth on microwave
technologies while working for Bell Telephone Laboratories from 1933 to 1947, got
his maser ideas into operation after moving from Bell to Columbia University in
1948. Herbert Zeiger and James Gordon were his assistants on the maser development
project, but he had others, who also went on to carve their niches in the maser
and, ultimately, laser fields. Among these were Isaac Abella, Herman Cummins, Ali
Javan and Arthur Schawlow.
Arthur L. Schawlow, who ultimately shared
the 1981 Nobel Prize in physics for his breakthroughs in laser-based spectroscopy,
worked very closely with Townes during the hectic early years of masers and lasers.
Not only did they become close friends, but Schawlow married Townes’ sister,
Alexander M. Prokhorov (Wikimedia Commons)
Among those working feverishly in the nascent
maser field at about the same time period as Townes in 1954 were Alexander M. Prokhorov
and Nikolai Basov of the Lebedev Physics Institute in Moscow. Together, but independently
of Townes, they made pioneering steps toward a working ammonia maser. After Townes,
Zeiger and Gordon produced the first working model, Prokhorov and Basov theorized
the first three-level maser system. Although they never built a working device,
the concepts they brought forth set up exciting new leaps in several fields, especially
spectroscopy. In 1964, Townes, Prokhorov and Basov were jointly rewarded with the
Nobel Prize for their maser efforts. Basov later went on to become the first to
apply lasers to the creation and study of thermonuclear plasmas as well as to the
initiation of chemical processes.
Nearly two years later, Nicolaas Bloembergen
of Harvard University produced the second description of a three-level maser, but
this scheme differed in that it used solid matter instead of ammonia gas. Bloembergen,
who had already established himself as the builder of the first operating nuclear
magnetic resonance (NMR) device, used some of those principles to outline the three-level
solid-state maser, but he wasn’t the first to make one. Later, he would share
the 1981 physics Nobel with Schawlow and Kai Siegbahn.
Derrick Scovil, working with George Feher
and Harold Seidel at Bell Telephone Labs, beat Bloembergen to the first operating
three-level maser. The three constructed their device using lanthanum ethyl sulfate
doped with gadolinium ions and published their results in 1957.
Also in 1957, several years before the
first operating laser was turned on, another of Townes’ assistants, Gordon
Gould, coined the term laser, obviously based on maser, with the first letter standing
for “light.” Gould’s coinage, along with his technical notes,
ultimately helped him gain several important patents for the technology 20 years
after the fact. (For more, see “Gordon Gould’s Scientific ‘Patent’ Method,” October 2008 Photonics Spectra, p. 131.)
Masers, of course, create coherent radiation
out of long microwaves. But even as the technology became established, many scoffed
that you could get the same results with more compact infrared or – heaven
forfend! – visible wavelengths. This didn’t stop others from trying,
with various levels of support or funding. Of those making the wild dash toward
the modern laser, Theodore H. Maiman of Hughes Research Laboratories was the ultimate
“winner of the race.” Maiman built the first laser, using synthetic
pink ruby, in May 1960. From there, the field exploded, as did tempers over who
created the laser.
Within months, research groups all over
were attacking “optical masers.” Ali Javan, whose efforts at Columbia
University and Bell Labs led him to work on three-level masers also, turned his
interest in population inversions within gases into the development of the first
helium-neon laser on Dec. 12, 1960. This was also the first laser to emit coherent
light continuously rather than in pulses. Javan was aided by William R. Bennett
Jr., who moved on to Yale University and the subsequent development of the first
chemical laser, and by Donald R. Herriott.
Since the initial flurry of attempts simply to observe lasing
action, the race has continued in many directions – some toward new useful
laser media, some toward new applications. Perhaps not too astonishingly, most of
the researchers circa 1960 already suspected that coherent light would be a uniquely
potent tool for communication, spectroscopy, imaging, surgery and even displays.
They did not disappoint.
Laser Science Doesn't Sleep
Listed here are some of the breakthroughs that followed the first
ruby laser demonstration. Nearly all of the devices mentioned here have played major
roles in science or everyday life right through today.
“Father of fiber optics” – coined the term in
Scientific American, 1960
Leo Johnson, Kurt Nassau,G.D. Boyd and R.R. Soden, Bell Labs
Demonstrated first continuous-wave laser that operated at room
temperature (no cooling necessary) – a 1.06-μm device made with Nd-doped
calcium tungstate (CaWO4), 1961
Peter Franken, A.E.Hill, C.W. Peters and G. Weinrich, University of Michigan
Discovered second harmonic generation, 1961
Alan D. White and J. Dane Rigden, Bell Labs
Developed first HeNe laser at visible wavelength (632.8 nm), 1962
Perkin-Elmer and Spectra Physics collaborated to make the early HeNe
laser (left) in 1963. Perkin-Elmer modified the design to create the model shown
on the right in 1966. (Photos: Lynn Savage)
Robert W. Hellwarth and R.J. McClung, Hughes Labs
First demonstration of Q-switching, 1962
Robert N. Hall, GE Research and Development Laboratories
First semiconductor (GaAs) diode laser, 1962
Marshall I. Nathan,IBM Watson Research Center
Second semiconductor laser, 1962
C. Kumar N. Patel, Bell Labs
First high-power gas laser (CO2), 1964
J.E. Geusic, H.M. Marcos and L.G. Van Uitert, Bell Labs
First Nd:YAG laser, 1964
Earl Bell and Arnold Bloom, Spectra-Physics Inc.
First pulsed ion laser (Hg+), 1964
William Bridges, Hughes Aircraft
Invented pulsed argon-ion laser, 1964
Hughes Corp. made the first argon-ion laser in 1964. Shown here is
one of the first commercial models (left), with its power supply (right). (Photos: Lynn Savage)
George C. Pimentel, UC Berkeley
With J.V.V. Kasper, developed first chemical laser (3.7 μm,
Peter Sorokin, IBM
Developed, with Mirek Stevenson, first uranium-doped and samarium-doped
First pulsed, fixed-wavelength dye laser, 1966
Bernard H. Soffer and B.B. McFarland, Korad Inc.
First wavelength-tunable pulsed dye laser, 1967
William Silfvast, Bell Labs
First continuous-wave HeCd laser, 1967
Izuo Hayashi, Bell Labs
First room-temperature continuous-wave semiconductor laser, 1970
Nikolai Basov, V.A. Daniely-chev, Yu M. Popov, and D.D. Khodkovich
First excimer laser (176 nm, Xe2), 1970
John M.J. Madey, Stanford University
First free-electron laser, 1971
Stuart Searles et al, Naval Research Lab
First rare-gas halide (XeBr) laser, 1975
Dennis Matthews Lawrence Livermore National Laboratory
First laboratory x-ray laser, 1984
Willis Lamb Jr. and R.C. Retherford
Came close to pursuing induced emissions, but didn’t.
Joseph Weber/A.M. Prokhorov and Nikolai G. Basov
Weber, at the University of Maryland, and the Russians, at Lebedev
Physics Institute in Moscow, separately pursued construction of a maser at the same time as Charles Townes, but Townes got there first.
Robert H. Dicke
In 1954, Dicke proposed an “optical bomb” that would
use a short excitation pulse to produce a population inversion, which in turn would
create an intense burst of spontaneous emission. In a 1958 patent, he suggested
that parallel mirrors would form a resonant optical cavity, but he didn’t
In 1907, Round saw electroluminescence when he applied an electric
field to silicon carbide, which is a semiconducting material. However, the first
semiconductor maser wasn’t developed until 1962.