Inventing the World’s First Continuous-Wave Laser

In December 1960, the helium-neon (HeNe) laser, the first laser to generate a continuous beam of light at 1.15 μm, was demonstrated by Ali Javan, William Bennett Jr., and Donald Herriott of Bell Labs. In the 60 years following its invention, the continuous-wave HeNe laser has been used in telecommunications, internet data transmission, holography, barcode scanners, medical devices, and more.

Javan, who was professor emeritus at MIT when he died in 2016 at the age of 89, is also credited with developing the first method for accurately measuring the speed of light and launching the field of high-resolution laser spectroscopy.

Born in Tehran, Iran, in 1926, Javan came to the U.S. in 1949, where he studied and worked at Columbia University with Nobel prize-winning physicist Charles H. Townes. Although he had received neither a bachelor’s nor a master’s degree, Javan earned his doctorate in physics at Columbia in 1954, with Townes serving as his thesis adviser.

Unlike the ruby laser — an invention that preceded the gas laser by about six months — Javan’s approach to lasing did not use optical pumping. For his HeNe laser, Javan used electric currents, not an intense light source, to convert electrical energy into the laser light output. The two laser types are quite different and are used for different purposes: An optically pumped laser creates pulsating bursts of laser light, while a gas laser produces a continuous light beam that is pure in color.

The ruby laser invented by Ted Maiman used optical pumping to create the population inversion necessary to achieve lasing. Javan discovered how a population inversion could be created in a gas discharge through the selective use of resonance energy transfer, and this was key to his invention of the first gas laser.

Javan published a paper on his concept for a gas laser in Physical Review Letters in June 1959. Although he had confidence in his invention, he knew that he had to be certain that the project would succeed before engaging a team in the engineering development phase. Soon after he joined the staff at Bell Telephone Laboratories in Murray Hill, N.J., he was given the go-ahead to do whatever was necessary to test the gas laser technology.

In this image, taken in 1960, Bell Labs researchers Ali Javan, William Bennett Jr., and Donald Herriott work on their helium-neon laser, the world's first laser that was capable of generating a continual light beam at 1.15 microns. The laser was also the first of its kind, an electrical discharge pumped gas laser. Courtesy of Bell Labs.

He assembled a team and designed experiments to measure a set of operating parameters in the gas mixture. An important milestone took place in February and March of 1960 when the team succeeded in demonstrating the amplification of light at the exact light wavelengths that Javan had predicted in his 1959 publication.

Javan’s breakthrough came on Dec. 12, 1960, with his demonstration of a continuous laser light beam emanating from a gas laser apparatus. The following day, members of Javan’s team and his Bell Labs colleagues used the laser light beam to place a telephone call — demonstrating the first application of the continuous-wave HeNe laser. To make the call, the engineers transposed the voice of a team member onto the laser light, transmitted the light beam to a light detector, and hooked the voice signal into the telephone system. Sixty years later, laser telecommunication via fiber optics is still used to transmit high data rates, tens of thousands of times higher than the data rate transmission by microwave that was the technology in use back then.

Dr. Ali Javan in one of his laser laboratories at Massachusetts Institute of Technology, April 1996. Courtesy of Betty Blair.

Here was how the first HeNe laser worked: Inside the laser apparatus, two electrodes sent electric current flowing through the gas. The electrical energy was stored as an internal energy in an energetic state of helium atoms, then transferred to the neon atoms, and then converted into a laser light beam. The laser light was extracted from the laser apparatus by placing two highly reflecting, parallel mirrors at both ends of the apparatus. The light, which was reflected back and forth between the two mirrors, increased exponentially at the speed of light, building in intensity and resulting in the laser light output.

The first HeNe laser cost Bell Labs $2 million and took Javan and his team two years to develop. Six decades later and still going strong, it has returned that investment hundreds of times over.

References:

“Scientists Who Made a Difference — Ali Javan: The Gas Laser and Beyond,” Betty Blai, Azerbaijan International, Summer 1996.

“Landmarks: The First Laser to Stay On,” Phys. Rev. Focus 26, 24, Dec. 10, 2010.

Lemelson-MIT, Ali Javan, Helium-Neon Laser.

“Professor Emeritus Ali Javan, Inventor of the First Gas Laser, Dies at 89,” Chuck Leddy, MIT News, Sept. 29, 2016.