Letters from Readers
Beam self-focusing was known earlier
To follow up on Roger P. Main's letter (April, p. 36) concerning laser beam self-guiding or self-focusing, the concept was known even earlier (by two years), and in the open scientific literature, than Main states. As I point out in a paper co-authored with my dissertation advisor, Tom Roberts, in Applied Optics (Appl. Opt. 26, 4570, November 1987), self-focusing was first introduced by Charles Townes and coworkers in 1964. Independently, and in the same year, the Russian researcher V. I. Talanov published on the same phenomenon. Thereafter, a number of Russians continued self-focusing research, notably S. A. Akhmanov, R. V. Khokhlov, A. P. Sukhorukov and G. A. Askaryan, and published openly on (at least part of) their work, although the published papers did not deal explicitly with self-focusing in the atmosphere.
I am grateful to Main for calling attention to Brueckner's work. Although I worked for the U.S. Army and had access to DARPA research at the time I was working on self-focusing, I saw no reference to Brueckner's work in the literature searches I was able to do in the early 1980s. Most of the U.S. research on self-focusing up to that point was done by Dept. of Energy scientists concerned with the damage effects caused by self-focusing filaments in solid-state laser media (for inertial-confinement fusion machines), where the power threshold for the phenomena is lower than in gasses. I do take issue with Main's terminology when he quotes Brueckner as saying that thermal blooming should produce "similar guiding effects in dielectrics." There is a thermally induced self-focusing or guiding effect, but it is the opposite of thermal blooming, wherein the beam spreads nonlinearly as opposed to contracting nonlinearly.1
Ronald I. Miller
1. R. I. Miller, Theoretical Investigation of Laser Beam Self-Focusing in the Atmosphere, Doctoral Dissertation, Southeastern Institute of Technology, Huntsville, AL (1985).
Gould is true inventor of the laser
I read with interest your article, " 'Faster, smaller, cheaper' drives laser and O/E product development" ("Optoelectronics Outlook 2002"; March 2002, p. S12), but was stunned by the first paragraph. The first paragraph mentions Charles Townes, Arthur Schawlow, and Ted Maiman as the laser forefathers and asks "Who would have thought then that lasers would one day be used to . . . transmit data, fabricate . . . restore vision, reshape tissue . . . and help keep the bad guys at bay?"
The answer of course is Gordon Gould, the actual inventor of the laser, whose patent application claimed all those applications and more in 1959. His own eyes were reshaped by laser, and after 30 years of patent wars, he eventually gained priority for most of his inventions over Townes, who had actually signed his notebooks, reviewed his government grant proposals, and who testified against him to block his patents. That story is covered in an interesting book, Laser: The Inventor, the Nobel Laureate, and the Thirty-Year Patent War by Nick Taylor (Simon and Schuster).
As the inventor of at least one of the applications mentioned in your article, I'm conscious of how easy it is when the money and accolades fly for the inventor to get lost in the shuffle. We all should tip our hats to Gould, one of the last of the independent inventors, who fought the government, the big boys, and left his mark for us all to follow.
New Business Development Manager
Ireland Imaging Operation
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