Masers and Lasers, 1951–1960
- Mario Bertolotti, Masers and Lasers: An Historical Approach (Bristol: A. Hilder, 1983).
- Joan Lisa Bromberg, The Laser in America, 1950–1970 (Cambridge, Mass.: MIT Press, 1991).
- Paul Forman, "Inventing the Maser in Postwar America," Osiris 7 (1992): 105–134.
- Paul Forman, "Into Quantum Electronics: The Maser as 'Gadget' of Cold-War America," in National Military Establishments and the Advancement of Science and Technology: Studies in Twentieth-Century History, eds. Paul Forman and José M. Sánchez-Ron (Kluwer Academic: Dordrecht, 1996), pp. 261–326.
- Jeff Hecht, Beam: The Race to Make the Laser (New York: Oxford University Press, 2005).
- Online: AIP Web Exhibit: Bright Idea: The First Lasers.
As with the transistor, which was invented in 1947, the maser (microwave amplification by stimulated emission of radiation) was created out of interest in applying novel physical effects to amplify signals. Where the transistor amplified signals in electronics, the maser amplified electromagnetic radiation. World War II-related radar technology development had already driven electromagnetic signal transmission into the microwave range of the electromagnetic spectrum with devices such as the klystron and the cavity magnetron. The maser was designed to drive transmission into still smaller wavelengths. Those applications did not immediately emerge, but the novel effects that made masers work in more accessible parts of the spectrum were nevertheless of interest. By the end of the 1950s, these effects were exploited to create coherent radiations in the visible part of the spectrum, which warranted the separate name, laser (light amplified by stimulated emission of radiation).
Some Pre-Maser Research
- 1947: Working at Columbia University, Willis Lamb and Robert Retherford note during a study of electrical discharge through hydrogen gas that a net negative absorption of microwaves resulting from an "inversion" of the population of molecules could occur at frequencies corresponding to a transition between energy levels in the gas. A population inversion means that more molecules are in a higher than in a lower energy state. Although his work is better known for producing a measurement of the "Lamb shift" in hydrogen, its concerns intersect those that led to the theory of the maser in that population inversion is a prerequisite for sustaining stimulated emission of electromagnetic radiation.
- 1950: At Harvard University Edward Purcell and Robert Pound demonstrate population inversion in the population of molecules in a crystal of lithium fluoride placed in a magnetic field.
- 1950: French physicist Alfred Kastler introduces the method of "optical pumping", which raises molecules into a high-energy state, in order to study microwave resonances. The method would become a standard technique in maser and laser construction.
- Online Resource: Alfred Kastler's Nobel Prize biography
Maser Theory and Development
- 1951: In April, Columbia University physicist Charles Townes, while attending an Office of Naval Research conference on millimeter wave generation, considers stimulating molecules to emit radiation using an input radiation, thereby amplifying the initial input. Most often radiation is absorbed by molecules; however, by using molecules already in a high-energy state, emission could, in principle, become the dominant effect. In the fall, he sets postdoctoral researcher Herbert Zeiger (who would leave for the MIT Lincoln Laboratory in February 1953) and graduate student James Gordon to work on this idea, using a beam of gaseous ammonia to supply the emitting molecules.
- 1952: University of Maryland electrical engineer Joseph Weber submits a similar idea for a molecular amplifier to a vacuum tube research conference, based on an idea he had had while learning about stimulated radiation in a course he took at Catholic University of America in 1948-49. Weber did not, however, proceed to construct the device.
- 1953: At Princeton, and consulting for RCA, Robert Dicke develops an idea for using an initiating pulse that would result in coherent "superradiant" spontaneously-emitted electromagnetic pulses (see abstract).
- 1953: By the end of the year Townes and Gordon are able to demonstrate amplification effects.
- 1954: In April, Townes and Gordon complete an "oscillating" maser where emitted radiation stimulates further radiation, thereby creating a continuous amplification effect.
- 1955: Rudolf Kompfner, head of electronics research at Bell Laboratories, recruits James Gordon to work on masers as a possible receiver in the satellite communications research program headed by John Pierce.
- 1955: Robert Dicke's student James Wittke begins work for RCA on microwave amplifiers based on stimulated emission called the "hot cell", to no avail.
- 1955: Townes's group constructs a second maser and demonstrates an exceptional purity of frequency, making the ammonia maser a candidate for setting frequency standards.
- 1955: Harold Lyons moves from the Microwave Standards Section of the National Bureau of Standards, where he had consulted with Townes, to the Hughes Research Laboratories, where he heads a maser research program.
- 1956: At Harvard, Nicolaas Bloembergen proposes a three-level solid-state maser, where emission (from level 3 to 2 and 2 to 1) occurs separately from pumping (from level 1 to 3).
By the mid-1950s, maser research and development had begun to expand markedly. Key efforts included:
- Harvard University, which was led by Nicolaas Bloembergen and included research fellow Joseph Artman and graduate student Sidney Shapiro. This team worked in conjunction with MIT Lincoln Laboratory.
- MIT Lincoln Laboratory, which included Benjamin Lax, James Meyer, and Alan McWhorter.
- Bell Laboratories, which included James Gordon, George Feher, and Harry Seidel, all working in Rudolf Kompfner's electronics research area, and Derrick Scovil who worked in the Solid State Device Development area.
- University of Michigan Willow Run Laboratory, which included Weston Vivian and Chihiro Kikuchi.
- Hughes Research Laboratories, which was run by Harold Lyons, and included George Birnbaum and Robert Hellwarth.
- Stanford University Electronics Laboratory, which included Hubert Heffner, Anthony Siegman, and Glen Wade.
Laser Theory and Realization
- 1957: In September, Charles Townes begins sketching ideas for an infrared and optical maser; in October, he establishes a partnership on the optical maser problem with his brother-in-law and occasional collaborator, Bell Laboratories researcher Arthur Schawlow.
- 1957: In late October, Townes consults with Columbia University graduate student, R. Gordon Gould (who was working under Polykarp Kusch) about lamps for optically pumping thallium. Gould had himself been considering the problem of the optical maser, and these conversations made him aware of Townes' work in that direction.
- 1957: In November, Gould compiles his ideas for the design and applications of a "laser" in his notebook, which he has notarized. In March 1958, Gould leaves Columbia, before receiving his PhD, to work at TRG, Inc., a military contractor. TRG grants Gould time to work on his invention ideas.
- 1958: In August, Schawlow and Townes submit a patent application for their optical maser design with Bell Laboratories as assignor, then submit a paper to the Physical Review, which is published in December (see the abstract and full paper).
- 1959: In April, Gould submits an extensive series of laser-related patent claims.
- 1960: In March, the Schawlow and Townes Bell Laboratories patent is granted (US Patent 2,929,922). Gould challenges the patent, setting off a famous, decades-long legal dispute over the intellectual property rights to the laser.
Following the publication of the Schawlow-Townes theory in 1958, a number of laboratories began working on the production of a functioning laser. Key efforts included:
- Bell Laboratories, which included Arthur Schawlow, Ali Javan, visiting Oxford physicist John Sanders, Yale spectroscopist William Bennett (who soon joined Bell Labs), Gary Boyd, and Amnon Yariv. Albert Clogston supervised and coordinated research.
- Columbia University, which was led by Charles Townes*, and included graduate students Herman Cummins and Isaac Abella. They worked toward a laser that used potassium as the active medium, and coordinated their efforts with Bell Laboratories.
- *Online Resource: Listen to an audio clip of Charles Townes discussing his reasons for dropping out of laser work at Bell Laboratories and Columbia to take up the position of vice president at the Institute for Defense Analyses.
- TRG, Inc., where Gordon Gould worked after his departure from Columbia. However, Gould was restricted from TRG's development effort, because he could not obtain the security clearance to work on the military-contracted project.
- IBM, which included Peter Sorokin and Mirek Stevenson working under the direction of William Smith in the Physics Section of IBM's new Research Division.
- Hughes Research Laboratories, where Theodore Maiman worked.
- 1960: In May and June, Theodore Maiman completes the first working pulsed-beam laser, using pink ruby as the active medium. In late June he sends an article to Physical Review Letters, which is rejected. The accomplishment is published in Nature in August (see citation).
- 1960: In August, Schawlow's team at Bell Laboratories builds their own ruby laser and publishes an article, which appears in Physical Review Letters in October (see citation).
- Online Resource: Listen to an audio clip of Schawlow discussing his decision to work on building a laser using red ruby as the active medium.
- 1960: In November, Sorokin's group at IBM completes a laser using a uranium-doped calcium fluoride crystal as the active medium; they soon repeat the feat using a samarium-doped crystal.
- 1960: In December at Bell Laboratories, Ali Javan, William Bennett, and Donald Herriot successfully operate a continuous-beam laser, using a helium-neon gas as the active medium.