Maiman

NAME: Maiman, Theodore H.

ACHIEVEMENT(S): The laser.

NICKNAME/ALIAS: in full, Theodore Harold Maiman

DATE/PLACE OF BIRTH: 11 July 1927, at Los Angeles, CA

DATE/PLACE/AGE AT DEATH: -

DISCIPLINE: Physicist

FIELD: Physics

LANGUAGE: English

PARENTS: ?

SIBLINGS: ?

SPOUSE: ?

CHILDREN: ?

EDUCATION: University of Colorado, 1945-49; University of Stanford, 1949-55

MAJOR WORK: "Stimulated Optical Radiation in Ruby", 'Nature', 6 August 1960,

pp. 493-94

LIFE AND TIMES:   In 1956, on graduating from Stanford, Maiman got a job with the Hughes Research Laboratories at Miami, a division of Hughes Aircraft Company. At Hughes, Maiman became interested in a new device that produced and amplified

electromagnetic radiation in the microwave region of the spectrum (producing coherent, monochromatic beams of microwaves).

The device known as the ‘maser’ ("microwave amplification by stimulated emission of radiation"), had been developed by the American physicist <work related to> Townes* (and independently by two Russian scientists, Nikolai Basov and Aleksandr Prokhorov) in 1953.  

The maser used a static electrical charge to discard the low-energy molecules of ammonia gas and focus (or concentrate) the high-energy molecules, causing them to enter the opening of a resonant cavity.  As molecules inside the cavity returned to a lower energy level (see laser), they released microwave radiation which, reflecting inside the cavity, stimulated additional molecules to radiate energy, a process which amplified (or intensified) the microwave radiation, which was then released.

In Townes' original design, ammonia molecules were stimulated to resonate with and amplify microwaves of the appropriate wavelength. In 1956 Townes and his colleagues theorized that continuous maser action could also occur by a three-level process in some solid paramagnetic crystals containing traces of impurities.

A prototype device to do this was then designed and constructed by Nicolaas Bloembergen at Harvard, who thus produced the first effective solid-state maser. In such a system, a (usually man-made) ruby crystal was used to amplify microwaves using a three energy-level system, in which the atoms are pumped from the ground state to the highest level and then fall to the middle level, during which maser action takes place at the frequency corresponding to that transition, an action which, unlike the two-level type, can be made continuous if the system is cooled.

Maiman was immediately interested in this three-level solid-state maser, and  concentrated his efforts on the use of chromium-doped corundum (i.e. ruby). During his research, Maiman came up with the idea of a "filled cavity", in which the microwave cavity was formed directly on the ruby cavity, resulting in an increase of 10-times the maser bandwidth than had previously been attained. It also allowed the maser to operate at much higher temperature, while the high dielectric constant of ruby resulted in a large reduction in the size of the cavity and allowed a small, internal permanent magnet to be used.

These developments were instrumental in making the solid-state maser a practical

device, and it remains the most common maser amplifier for microwaves. Maiman also developed a parallel-plate maser cavity design, again filled with ruby, and it was this cavity concept which led him to consider the generation of stimulated emission at much higher frequencies.

Meanwhile, in 1958, Townes and Arthur L. Schawlow, had published a theoretical paper suggesting the possibility of making a similar device that would, operating at frequencies in the infrared, optical, and ultraviolet regions, generate beams of visible light rather than microwaves, basing their concept around an alkali (potassium) vapour system as the medium for generating the monochromatic light source.

Maiman  knew of developments made simultaneously by Bloembergen, Sugano, Tanabe and Wieder in which a solid, rather than a gas, was used as the active medium in such an optical maser and, having found his parallel-plate cavity successful at microwave frequencies, he decided to pursue the use of optical fluorescence in solids using ruby-based devices in his experiments.

Others had already experimented with ruby (which is aluminium oxide in which a fraction of a percent of the aluminium ions have been replaced by chromium) but their results had been discouraging, as the amount of amplification obtained with the ruby was

insufficient to produce the desired beam. 

Because of his earlier success, Maiman continued to work with rubies, and in 1959 constructed his own ruby-based optical maser, consisting of a ruby rod with the ends carefully ground flat and parallel, coated with silver to act as reflectors (thus creating a parallel-plate cavity).

When, in May 1960, an intense beam of light from a helical pulsed xenon lamp (fired by discharging a capacitor through it) was fed into the rod, it emitted a coherent, monochromatic beam of visible light  (i.e. providing a successful modification of the maser process in the visible region) in the red portion of the electromagnetic spectrum. Maiman's device was named the <invented> laser* ("light amplification by stimulated emission of radiation").

The light it produced consisted of a very narrow beam of stimulated electromagnetic radiation with a wavelength of precisely 6943 angstroms. This first example of coherent, monochromatic beam of light has since proved to have the ability to travel great distances without dispersing, a property that has made it ideal for measuring the distance from the Earth to the moon, for example, while the high concentration of energy in the beam means that it also produces very high temperatures at the point where it comes into contact with a material, making it useful in welding and cutting, and in surgical procedures.

In 1962, Maiman left Hughes Research Laboratories and established his own company, Konrad Corporation, devoted to the research, development and manufacture of lasers. In 1968, the company was acquired by Union Carbide, and Maiman founded a consultant company, Maiman Associates, to specialize in optical and laser problems.

Four years later, in 1972, Maiman also co-founded the Laser Video Corporation for the development of large-screen, laser-driven colour video display systems, and in 1976 he became vice-president for advanced technology at TRW Electronics.

ASSESSMENT: His work on the laser was a fundamental advance in applied physics.

EXTRA CONNECTIONS: None

ONELINER: Theodore Maiman, inventor of the laser

BIBLIOGRAPHY:

EB

McGraw-Hill Modern Scientists and Engineers (vol. 2, 1980)