The Laser Turns 60

FAROOQ AHMED, CONTRIBUTING EDITOR

Six decades ago, in a windowless lab on a hilltop above the Pacific Ocean, Theodore (Ted) Maiman — assisted by Irnee D’Haenens — tested a palm-size device that would upend the scientific establishment. Working at Hughes Research Lab (now HRL Laboratories and formerly the research arm of Hughes Aircraft Co.) in Malibu, Calif., Maiman had built the prototype in less than nine months with a paltry budget of $50,000. It was a fraction of what his competitors working on well-funded projects worldwide at powerhouse facilities had to accomplish the same task, which was to build the world’s first laser (Figure 1).

Figure 1. The first laser consisted of a polished and silvered synthetic ruby rod with mirrors capping both ends, surrounded by a xenon flashlamp. Courtesy of Kathleen Maiman.

Deceptively simple, the device consisted of few parts: a 1- × 2-cm rod of synthetic ruby crystal, meticulously polished and silvered at both ends, capped by mirrors. The rod served as a Fabry-Pérot resonator — essentially an optical cavity — and was slipped inside the coils of a helical, xenon flashlamp.

The ruby laser was antithetical to the thinking of the top laser researchers at the time, particularly Columbia University’s Charles Townes and Bell Lab’s Arthur Schawlow. Schawlow had concluded, incorrectly, that ruby crystals were grossly inefficient for lasing. He, Townes, and others focused instead on exciting gases such as helium and neon¹. In addition, the commercial flashlamp that Maiman had purchased from General Electric was intended for photographic use. The ethos of the time dictated that scientists did not rely on off-the-shelf components for ground-breaking accomplishments.

As Maiman and D’Haenens slowly dialed up the voltage, the lamp flashed with increasing brightness. A pulse of red-tinged light shot out of a pin-size, 1-mm-diameter hole in one of the mirrors. But it wasn’t until they crossed 950 V that the telltale spike appeared on the oscilloscope: a trace that dramatically peaked and then decreased quickly. The pulse lasted for about a millisecond, with a wavelength of 694.3 nm and a linewidth of 0.53 nm. As theorized by Albert Einstein in 1917 and elucidated by Valentin Fabrikant in 1940, the flashlamp had stimulated a population inversion in the ruby rod — a state in which more of the ruby atoms were energetically excited rather than unexcited (Figure 2). The population inversion was the hallmark of amplified light, and on May 16, 1960, the laser was born.

Figure 2. A Polaroid photo of an oscilloscope recording of one of the first laser pulses, from Ted Maiman’s 1960 lab notebook at Hughes Research Lab. Courtesy of Kathleen Maiman.

60th celebrations

This May marked the 60th anniversary of Maiman’s invention of the laser. While the COVID-19 pandemic forced celebrations online, institutions throughout the world recognized the milestone. UNESCO (the United Nations Educational, Scientific and Cultural Organization) celebrated the May 16 International Day of Light, and HRL commissioned a mural on the wall of Maiman’s lab. It joins a plaque placed at the facility by IEEE.

David Chow, chief scientific operator of HRL, said the first laser “spawned a whole generation of scientists here.”

“By the time I arrived 30 years ago, many members of our senior management had come related to that activity,” Chow said.

In the past 60 years, the laser has gone from scientific curiosity to essential tool in countless industries and fields. The laser has transformed not only what and how we see and communicate, but also how we practice science, medicine, engineering, and art. We remove tattoos with lasers and tease our cats with them, and we watch movies, play video games, and listen to music — all courtesy of lasers. In the future, they will help our cars navigate autonomously and may even help us control the weather^2,3.

Solution in need of a problem

While it is now, perhaps, impossible to overstate the first laser’s importance, at the time of its invention the technology was underappreciated (Figure 3). According to science historian Jeff Hecht, “D’Haenens himself remarked that the ‘laser was a solution in need of a problem.’” Hecht’s 2005 book, Beam, details the many groups that tried to invent the laser, and his most recent book reveals the development of military lasers for weaponry^4,5.

Figure 3. A Hughes Research Lab press photo of Maiman and the components of the first laser. Courtesy of HRL Laboratories.

Maiman’s willingness to confront conventional scientific wisdom was not enough to convince others of the worth of his breakthrough. His paper on the ruby laser was rejected without a detailed explanation by the first journal he submitted it to, Physical Review Letters.

“It has to be one of the most famous rejections in scientific history,” Hecht said.

The journal Nature eventually published a shorter version of Maiman’s article in August 1960 after Hughes threw a lavish press conference announcing the invention at the Delmonico Hotel in New York City in July of that year⁶. However, even Hughes did not move to file a patent until a year later, in 1961, when Maiman left to start his own laser company, the Korad Corp⁷. “Ted always had such integrity,” said Kathleen Maiman, his wife.The scientist died from mastocytosis in Vancouver, B.C., in 2007. “And he didn’t like to play politics.”

This refusal to play politics, Hecht said, was a contributing factor as to why Maiman, despite receiving accolades that included the Japan Prize and the Wolf Prize in Physics, never received the Nobel Prize — although he was nominated three times. “Townes certainly deserved a share in the 1964 Nobel Prize in physics,” Hecht said. “But so did Maiman. People didn’t realize what it took to produce the beam.”

Producing the beam

As with all scientific breakthroughs, the ruby laser was a product of theory and research that spanned decades. Or, as Maiman noted in his memoir, The Laser Inventor, “Scientific advances come from building on prior scientific developments.”

As with all scientific breakthroughs, the ruby laser was a product of theory and research that spanned decades.

“Many assume that the [laser] concept evolved from some sudden, inspirational thought. It didn’t happen that way,” Maiman wrote.⁸

Townes’ work developing the maser, which amplifies microwave rather than infrared or visible radiation, contributed immensely to Maiman’s ruby maser, which Hughes had asked him to build under contract from the U.S. Army Signal Corps prior to the laser. Maiman reduced the maser from 2500 kg in weight to about 12 kg, eliminating the need for cryogenic cooling.

At Hughes, Maiman had support from D’Haenens and also from the engineer Charles Asawa, who suggested using the xenon flashlamp to excite the ruby crystal and who helped interpret spectrograph data (Figure 4). “Coming to an industrial research lab isn’t just about the funding itself,” HRL’s Chow said, “but also the availability of the equipment.” The spectrograph Asawa used to measure the laser beam’s linewidth, for example, had been borrowed from a colleague’s lab.

Figure 4. Charles Asawa (left) and Irnee D’Haenens look at the first laser at Hughes Research Lab in 1985. Courtesy of HRL Laboratories.

“Physics at Bell Labs or in Boston works exactly the same as in Malibu,” Chow said. “There’s no particular reason to believe that just because you’ve proven that something can be done, you’ll be the first to demonstrate it. And at that point, I would argue that engineering skill typically becomes more important.”

In the race to the first laser, this was one area that Maiman certainly had an advantage. “Partly because of his father’s influence,” Andrew Rawicz said, “Maiman became both a very good physicist and a good engineer as well.” (Maiman’s father, an electrical engineer, had worked on the Manhattan Project at Bell Labs and had even crossed paths there with a young Townes.) A professor of engineering at Vancouver’s Simon Fraser University, Rawicz helped the laser inventor and his wife, Kathleen, immigrate to Canada from the U.S. in 1999 and considered Maiman to be a mentor.

Maiman’s familiarity with ruby and his initial experiments testing the gemstone gave him the knowledge and confidence to use it for lasing purposes. “By 1959,” Chow said, “they knew [ruby’s quantum efficiency] was much higher [than published]. They had a key piece of information the others didn’t.” Maiman had demonstrated that the quantum efficiency of ruby’s fluorescence was 75%, while others thought it was closer to 1%.

Laser legacy

Within months of the Hughes press conference in July 1960 that announced the invention, scientists around the world were able to re-create Maiman’s ruby laser, often from the press release and photos alone. Even Bell Labs, which had focused on building a gaseous, continuous-wave laser rather than a solid-state pulse laser, quickly replicated Maiman’s work. Laser historian Hecht said, “Schawlow’s group [at Bell] fired a laser pulse a distance of about 25 miles in a couple of months.”

“The fact that it was reproducible is, of course, the most important accomplishment for science,” Rawicz said. The Canadian engineer first used a ruby laser while working at an industrial welding institute in his native Poland in the 1970s.

The ruby laser’s reproducibility helped accelerate laser science. By the end of 1961, Maiman’s former colleague at Hughes, Robert Hellwarth, invented Q-switching, which greatly increased power output. Several manufacturers began selling commercial lasers. And a ruby laser was used medically for the first time — for retinal tumor ablation at Columbia-Presbyterian Medical Center in New York City. Just two years after that, the commercial laser market reached $1 million.

Red sparkle

Despite being called “the inventor of the death ray” by newspapers at the time, Maiman was interested in using lasers for altruistic rather than destructive purposes. In 1969, his company, Korad, helped NASA calculate the distance from Earth to the moon by bouncing a laser beam off a reflector placed on the lunar surface by the crew of Apollo 11. He also spearheaded the use of lasers for biomedical purposes, collaborating with lasik pioneer and ophthalmologist Stephen Joffe, and assisting Rawicz with the design of biomedical engineering courses.

For a biography of Maiman that he wrote for the National Academy of Sciences, Rawicz plotted the year of development of sources of coherent electromagnetic radiation against their frequencies — from the telegraph to radar and the laser (Figure 5)⁹. On a semilogarithmic scale, Rawicz said, “the only outlier is the laser. It shouldn’t have been invented until this year — 2020!”

Figure 5. A historical evolution of the coherent spectrum by Simon Fraser University’s Andrew Rawicz. He plotted the year of development of sources of coherent electromagnetic radiation against their frequencies to discover that the laser is the only outlier. Courtesy of Andrew Rawicz.

In all, Maiman constructed four ruby lasers while at Hughes Research Lab. HRL and the Smithsonian in Washington, D.C., each have possession of one, and Asawa was given one when he left Hughes. Maiman’s wife has the original, which still works. “I am asked to demonstrate it at conferences and special occasions from time to time,” Kathleen said. “Even scientists get a thrill out of seeing its small red sparkle on the wall.”

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Acknowledgments

The author would like to thank David Chow of HRL; Jeff Hecht; Kathleen Maiman; and Andrew Rawicz of Simon Fraser University.

References

1. A. Schawlow and C.H. Townes (1958). Infrared and optical masers. Phys Rev, Vol. 112, p. 1940.

2. H. Lim and A. Taeihagh (2019). Algorithmic decision-making in AVs: understanding ethical and technical concerns for smart cities. Sustainability, Vol. 11, No. 20, p. 5791, www.doi.org/10.3390/su11205791.

3. J.P. Wolf (2018). Short-pulse lasers for weather control. Rep Prog Phys, Vol. 81, No. 2, p. 026001, www.doi.org/10.1088/1361-6633/aa8488.

4. J. Hecht (2005). Beam: The Race to Make the Laser. Oxford, England: Oxford University Press.

5. J. Hecht (2019). Lasers, Death Rays, and the Long, Strange Quest for the Ultimate Weapon. Buffalo, N.Y.: Prometheus Books.

6. T.H. Maiman (1960). Stimulated optical radiation in ruby. Nature, Vol. 187, No. 4736, pp. 493-494.

7. T.H. Maiman (1967). U.S. Patent No. 3,353,115. Washington, D.C.: U.S. Patent and Trademark Office.

8. T.H. Maiman (2018). The Laser Inventor: Memoirs of Theodore H. Maiman. Cham, Switzerland: Springer Biographies.

9. A. Rawicz and N. Holonyak (2014). Theodore H. Maiman: Biographical Memoir. Washington, D.C.: National Academy of Sciences.