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Maser-to-Laser Man

Charles Townes sketched out the basic design for the maser in 1951. It was not until 1953 that Townes, James Gordon and Herbert Zeigler arrived at the first maser; it operated at 24 GHz using ammonia. It found initial use as a UHF oscillator and precision clock. He immediately wanted to go to much shorter wavelengths.

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Townes (left) and Gordon (right)

Townes teamed up with his brother-in-law, Arthur Schawlow, and they generated the framework for infrared and optical masers.[1]

“The extension of maser techniques to the infrared and optical region is considered. It is shown that by using a resonant cavity of centimeter dimensions, having many resonant modes, maser oscillation at these wavelengths can be achieved by pumping with reasonable amounts of incoherent light. For wavelengths much shorter than those of the ultraviolet region, maser-type amplification appears to be quite impractical. Although use of a multimode cavity is suggested, a single mode may be selected by making only the end walls highly reflecting, and defining a suitably small angular aperture. Then extremely monochromatic and coherent light is produced. The design principles are illustrated by reference to a system using potassium vapor.”

Reflecting on the state of the art back in the late 1950’s is instructive. For example, “For a wavelength equal to 104 A, it was seen above that spontaneous emission produced a few milliwatts of power in a maser system of dimensions near one centimeter, assuming refectivities which seem attainable at this wavelength. Thus in the ultraviolet region at
wavelength equal to 1000A, one may expect spontaneous emissions of intensities near ten watts. This is so large that supply of this much power by excitation in some other spectral line becomes very difficult. Another decrease of a factor of 10 in wavelength would bring the spontaneous emission to the clearly prohibitive value of 100 kilowatts. These figures show that maser systems can be expected to operate successfully in the infrared, optical, and perhaps in the ultraviolet regions, but that, unless some radically new approach is found, they cannot be pushed to wavelengths much shorter than those in the ultraviolet region”

Townes in 2015, at 89 years, during an interview by Bonnie Azab Powell, “[The maser] was a new idea, a sudden visualization I had of what might be done to produce electromagnetic waves, so it’s somewhat parallel to what we normally call revelation in religion. Whether the inspiration for the maser and the laser was God’s gift to me is something one can argue about. The real question should be, where do brand-new human ideas come from anyway? To what extent does God help us? I think he’s been helping me all along. I think he helps all of us – that there’s a direction in our universe and it has been determined and is being determined. How? We don’t know these things. There are many questions in both science and religion and we have to make our best judgment. But I think spirituality has a continuous effect on me and on other people.”

A very nice and detailed obituary on Townes appeared in IEEE Spectrum on 28 January 2015, and it’s linked here.

References

1 A. L. Schawlow and C. H. Townes, “Infrared and Optical Masers,” Phys. Rev. 112, p.1940, 15 December 1958.

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A History of Military Mapping Camera Development – 1964

“For many years the Army’s Corps of Engineers has held the prime responsibility for the military development of map plotting equipment and for topographic mapping techniques in general. With the advent of the airplane, responsibility for the development of mapping cameras and other airborne mapping and surveying equipment was placed with the Army Air Corps. As a result, in 1920, the Army organized, at what is now Wright-Patterson Air Force Base, the Wright Field Military Detachment. This group was assigned as a branch of the Engineer Board at Fort Belvoir, Virginia, in the early part of World War II. The Engineer Board was reorganized several years later to form the U. S. Army Engineer Research and Development Laboratories. The present aerial mapping liaison group at Wright-Patterson Air Force Base is now a part of the U. S. Army Engineer Geodesy, Intelligence and Mapping Research and Development Agency, Fort Belvoir, Virginia, which operates directly under the Chief of Engineers.

The past forty years has seen the development in the Air Force of two lines of aerial cameras: the reconnaissance series and the mapping series. This division in development was influenced by the differing needs of the Army and the Air Force. In its prime responsibility for targeting, charting and reconnaissance interpretation, the Air Force has insisted that the major consideration in the development of reconnaissance cameras be the enhancement of photographic resolution. Hence, work in this area has included the development of lenses with high resolving power, films capable of producing high resolution, film magazines with image-motion compensation capabilities, and gyroscopically stabilized aerial camera mounts which reduce vehicle vibrations and acceleration effects.

The prime requisite of the Corps of Engineers for a mapping camera is a high degree of dimensional stability in the camera-lens-film
combination to produce photography capable of direct application to map compilation. Therefore, mapping camera development has been characterized by the production of frame-type cameras having low-distortion lenses, lens cones fabricated from alloys providing high structural stability and with fiducial markers placed on the lens cone
rather than on the magazine, also between-the-lens shutters, and appropriate data recordings which appear on the film negative
between frames. The cameras are stocked with low differential distortion, topographic base films, and are installed in stabilized aerial camera mounts. Development of mapping cameras is accomplished by the Air Force upon imposition of Corps of Engineers requirements. This work has been supported actively through the years by the previously mentioned Corps of Engineers personnel who have been assigned to duty at Wright-Patterson Air Force Base.

As early as 1955, Dr. James Baker was commissioned by the Air Force to design a low distortion mapping lens which would have a higher amount of photo resolution than the current Metrogon and Planigon lenses; these average about 22 and 24 lines/mm, respectively, in AWAR. The resulting Type T-ll lens, later called the Geocon I, proved to have lens distortions of less than 10 microns; its resolution measured 52 lines/mm on-axis and 35 lines/mm AWAR. The lens was mounted in a T-ll camera body for flight testing. The full F/5.6 speed of the lens, however, could not be realized in the prototype camera, which produced a maximum aperture of only F/8. This camera subsequently was used in high-speed, high-altitude flight tests.”

Reference: ROBERT G. LIVINGSTON, “A History of Military Mapping Camera Development,” Photogrammetric Engineering, p. 97-110, January 1964.

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From Optical Tables to The Terminator’s Sidearm

Let’s begin with the end, which is depicted nicely in the following video:

From Newport…Newport Research Corporation was founded in a garage in 1969 by graduates of the California Institute of Technology, John Matthews and Dennis Terry, who were looking for industrial applications for lasers. Just a few years earlier, in 1960, physicist Theodore Harold Maiman had invented the first operable laser, spurring worldwide interest in the technology. Another Cal Tech graduate, Milton Chang, soon joined the company. At school he had worked with Matthews and Terry, and they had become all too aware of a glaring need for equipment specifically designed for laser work. The optical tables at the school were so unstable that the graduate students had to conduct experiments late at night because during the day the building shook too much. Although not noticeable to most people, the building’s elevators caused vibrations while traveling up and down in the shafts. The third-shift experiments proved fruitful, however, as the young researchers developed some important techniques that would be put to use at Newport. In the meantime, Chang graduated and worked in the research laboratory at Northrop Corp. for two years before Matthews recruited him to head up Newport’s marketing. Given their encounters with troublesome elevators, it was little wonder that Newport’s first commercial product was a steel-clad, honeycomb core table for laser experiments, essentially a stabilized platform that counteracted the vibrations emanating from the floor. In the first year of operation, Newport generated sales of $46,000, a modest number, yet the company was now able to move out of the garage and lease industrial space in Fountain Valley, California.

Newport also took advantage of its stabilized table business to launch a catalog in 1971. Newport Catalog became a wish book for high-tech clientele, a source for precision optic, electro-optic, and opto-mechanical products. During its first decade Newport pursued opportunities in whatever direction laser research took, such as holography and interferometry. In 1978 the company went public.

In addition to following the leads of others, Newport pursued its own interests. Matthews, for instance, was an avid shooter, and during the 1970s he began developing a laser sight for firearms. He received a patent on a laser sight in 1979, but the initial version was far too cumbersome to have commercial value. Because refining the sight would require far more funds than Newport could invest, Matthews asked the board to sell the laser sight business to him and some staff members (Peter Hauk and Ed Reynolds) who wanted to branch off. After the board agreed, Matthews resigned as Newport’s president, replaced by Chang, and founded a new company, Laser Products, which later adopted the name Sure-Fire LLC, makers of the SureFire WeaponLight, a weapon-mounted flashlight for the law enforcement and military markets. In addition, Matthews’ company would produce laser sights, shield lights, and baton lights so powerful they could blind and temporarily disable an opponent.

Laser Products introduced the first commercially available laser sighting system, the LPC Model 7, in 1979. It was mounted to a Colt Trooper .357 Magnum revolver and sold as a complete, laser-aimed weapon, powered by a huge battery built into the gun’s custom Pachmayr grip.

Fast forward to 1982-83. Ed Reynolds received a call from one of the prop houses to make a laser-aimed weapon for The Terminator, which was released in 1984. They wanted a laser mounted to an AMT Longslide .45…and they were unwilling to pay for it. Since there was no money for a custom power supply, there was a line running from the laser to a cable that connected to an external power supply. To fire the laser, Arnold Schwarzenegger had to reach into his coat pocket with his other hand and flip a switch.

The weapon with the cable shown, leading to the power supply.

Later, Reynolds mentioned that he did receive a T-shirt and some other promotional items from the movie in recognition of a job well done. There seems to be no doubt that The Terminator helped SureFire in the marketplace, which helped to advance John Matthews’ continuing passion for lasers and optics.