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Gas Laser

    We hear about DVD, CD, Laser eye surgery, etc. or use them everyday and without a doubt Laser has been one of the greatest scientific inventions. But did you ever wonder who invented this great technology? Did you know an Iranian invented laser? The first type of laser was Gas Laser (which is being widely used in medical systems & industry) and it was invented by Ali Javan an Iranian physicist in MIT.  Let us learn more about this invention from his own words, parts of his interview with Betty Blair. For more information read his biography.

The Laser and World War II | The Helium - Neon Gas Laser | The First Laser Telephone Experiment

The Laser - A Possibility in the 1930s
    In the scientific world, they always say that when the time comes for an invention or a discovery to be made, if you don't do it, someone else will. To a large extent, that's true. But it's not always the case. People can miss a good idea.

    When it comes to the laser-my kind of laser, the Gas Laser-I'm convinced it could have been invented in the 1930s, not thirty years later in 1960 when I managed to do it.

    If you look back into the history of science, you find physicists-mostly in Europe-who had come very close to the idea of lasers by 1937 and 1938. Scientists back then were studying how atoms emit light waves and they came very close to the laser idea (light amplification in gases by stimulated emission of radiation). From the literature you can see that they were just about to grasp the idea but then they moved away from it, and the idea faded. Had I been around in the 1930s, I'm sure I would have invented the laser then. I'm not exaggerating. I know I would have done it.

    I know why these scientists missed it. They were deeply preoccupied with the properties of matter in thermal equilibrium. In lasers, however, atoms have to be in a non-thermal equilibrium state. But that becomes a bit too involved for our discussion here. Of course, these early scientists are all gone now. But, admittedly, they were pioneers in the field.

The Laser and World War II
    We can only speculate how the laser might have been used in World War II had such technology existed. Laser radar, not microwave radar, might have been the "name of the game." Today the laser has many significant uses in defense. Back then, it's difficult to say what would have happened, as the technology certainly would not have been as advanced as it is today. Without a doubt, had the laser been invented 65 years ago instead of only 35, many laser applications would have been developed a lot sooner.

    Science always develops on the strength of work done in the past. When Newton discovered gravity, he admitted that he had "stood on the shoulders of giants and that's how he had seen farther." Nothing ever develops on its own, isolated from the past. There's always a foundation for our knowledge that others have laid and that we build upon.

    The laser is a product of our knowing the nature of atoms to perfection, specifically their wave nature. Atoms are waves and their particle nature is the property of their own waves. We have discovered the nature of atoms, what they are, by the light they emit. In the 1920s, the science of the wave nature of atoms was known down to the smallest detail. Books had already been written on the subject. There were giants at that time who had made these early discoveries-Neils Bohr, Schrodinger, Einstein-I could go on naming others.

    It's difficult to pinpoint the moment when a creative idea is born. Oh, I suppose there's a beginning somewhere along the line. But who knows? At some moment you know everything about your invention even though you're not aware that you do. And then suddenly it all fits together and the discovery is made.

    When I came up with the idea for the gas laser, much of it, if not all, was based on my intense involvement in the work I was doing. But I knew I could make the laser work; otherwise, I wouldn't have gone after it.

    From the very beginning people who knew of my idea were very skeptical. Even people on my own team who were working on it with me had hesitations and doubts. Over the years I've seen this tendency in a lot of people. Even good physicists are sometimes insecure in their own beliefs; they waver with uncertainty.

    Once when working with one of my students on a new kind of laser, we were ready for the final test and I jokingly said, "Hey, what if we throw the switch and nothing happens!" Suddenly his face turned white in panic. I laughed. "No, no, no. It will work!" I said, trying to reassure him. And then we flipped the switch and everything turned out right. But this often happens with people who are deeply involved in what they do. They're insecure and afraid even when they have no reason to be.

    Of course, sometimes there are experiments of the magnitude that we've been talking about, where uncertainties do exist simply because the scientific basis is not known. As a scientist, you have to push ahead and test your ideas even if you don't know exactly what the ultimate outcome will be. But you had better be certain that the outcome still leads to important scientific results.

    But with something like this-the gas laser-the only thing that mattered was to make it work. Based on my theoretical predictions, I had to be absolutely certain that the project would succeed before engaging a team in the engineering development phase.

    At that time, I had just joined the research staff at the Bell Telephone Laboratory (Murray Hill, New Jersey) and had managed to convince them to give me "an open ticket" to do whatever was necessary to test the gas laser idea.

    At about the same time, two other physicists, Charles H. Townes and Arthur L. Schawlow, had proposed a different approach to lasers. Theirs was based on the principle of what is now known as "Optically Pumped Lasers," which extracts laser light from atoms by pumping them with an intense light source.

    Mine was an entirely different approach. I used electric currents (not an intense light source) to convert electrical energy into the laser light output, a process now known as the "Gas Laser". These two inventions-the "Optically Pumped Laser" and the "Gas Laser" are really very different from each other and are used for entirely different purposes.

    The "Optically Pumped Laser" creates pulsating bursts of laser light but my "Gas Laser" produces a continuous light beam which is so pure in color that it reaches the limits that nature permits. It was Theodore Maiman, a physicist at Hughes Aircraft Laboratory in Malibu, California, who first succeeded with the Townes and Schawlow laser. Maiman used a synthetic Ruby crystal and a flash lamp to achieve the optical pumping. His "Optically Pumped Laser" preceded my "Gas Laser" by about six months.

Sketch depicting the principles of Dr. Ali Javan's Gas Laser. "Smithsonian" Magazine, April 1971.

The Helium - Neon Gas Laser
    For highly technical reasons when I first tested my laser idea, I selected two inert gases, Helium and Neon. Here's how it works. Inside the laser apparatus, two electrodes send electric current flowing through the gas, then a sequence of events takes place in the gas mixture. The electrical energy is first 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. It took me two years and two million dollars of Bell Telephone's money to transform that idea into a practical invention.

    Incidentally, the extraction of the laser light from the laser apparatus is done by placing two highly reflecting and parallel mirrors at both ends of the laser apparatus. The light, which is reflected back and forth between the two mirrors, increases exponentially at the speed of light and builds up in intensity, resulting in the laser light output from the laser apparatus.

    I published my idea for the laser in "Physical Review Letters" in June 1959 at a time when I was already deeply involved with the project. I had already 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 our team succeeded in demonstrating the amplification of light at the exact light wavelengths that I had predicted in my 1959 publication. But it would take a few more months to assemble a working laser apparatus that could extract the laser light from the atoms. It turns out that I had calculated the progress of our work so carefully that I was able to forecast when we would succeed in producing the laser light. I predicted the middle of December. I wanted to succeed before Christmas.

Ali Javan, William Bennett, and Donald Herriott adjust the
 helium neon laser, the first laser to generate a continuous
 beam of light at 1.15 microns and the first of many electrical
 discharge pumped gas lasers.

    And that's when it happened-right on schedule-December 12, 1960. It was the first time in the history of science that a continuous laser light beam had emanated from a gas laser apparatus. I remembering looking at my watch. It was 4:20 pm. It had been snowing heavily that day.
How do I know it was 4:20 pm? Well, it was a such momentous occasion and I realized the impact that moment would have upon the future of science and technology.

Today, telecommunications are among the foremost uses of the continuous laser light beam.

The First Laser Telephone Experiment
    We knew that lasers could be used in telecommunications back when we produced the first gas laser beam. In fact, we tried it out the very next day. I was living in Greenwich Village, New York City at the time, and driving back and forth to my lab at Bell in New Jersey, about an hour's commute. The day we succeeded in creating the Gas Laser beam I stayed late at the Lab driving home in the wee hours of the morning. That was usual for me. The next day when I awoke around noon, I put in a call to the lab. One of the team members answered and asked me to hold the line for a moment. Then I heard a voice, somewhat quivering in transmission, telling me that it was the laser light speaking to me. It was the voice of Mr. Balik, now Professor at McAlaster University in Canada. We were ecstatic-all of us. It was the first time in history that a telephone conversation had been transmitted by a laser beam. The date was December 13, 1960.

    It turns out that members of my team together with Bell engineers had jury-rigged what was needed to transpose the voice onto the laser light, transmit the light beam across my lab to the far end of the room to a light detector and then hook the voice signal into the telephone system. Now, 35 years later, laser telecommunication via fiber optics is commonplace because of its superiority in transmitting high data rates, tens of thousands of times higher than the data rate transmission by microwave which was the technology in use back then. Laser communication is still expanding and is the key technology used in today's "information super highway"-the Internet.

    In academics, particularly the sciences, there's a tradition of first announcing significant breakthroughs in scientific journals before releasing the news to the media. By Christmas, I had written what is now considered an historical letter for the "Physical Review Letter" (January 30, 1961) reporting our success. The letter was co-authored with two key members of the team, William Bennett and Don Herriott.

    The day after the letter was published, a News Conference was held at the Park Plaza Hotel in New York City. Bell Lab engineers had set up the same voice transmission system on the Helium-Neon Laser beam for the reporters to see and play around with. It made the news the next morning. AT&T shares on the stock market shot up. Back then Bell Lab provided the research arm of AT&T. The $2 million costs of the laser project was essential paid for by the nickels (5 cents) and dimes (10 cents) generated from telephone calls. The invention of the gas laser has turned out to be an incredibly far-reaching and worthwhile investment.

    AT&T along with the rest of telecommunication industry is no longer involved with research. Today, universities are doing that job. Hundreds of gas lasers have been made to operate at thousands of different colors in the spectrum, both in the visible (red, green and blue), and at near ultraviolet and infrared. All of them are based on the same principle that I established and used in my original electric Helium-Neon laser.

    A number of other important gas lasers have since evolved including the well-known carbon dioxide gas laser (CO2 laser) which can generate a very high-powered laser light beam, and which is used in laser radar as well as precision metal-welding in manufacturing for items such as pace-makers which are implanted in heart patients to regulate their heartbeats.

    The Helium-Neon Laser itself turned out to be an immensely valuable instrument. Millions of them are being used both in research laboratories as well as for a wide range of practical uses. One of the most widespread uses of the Helium-Neon Gas Laser is something many people probably take for granted in their everyday lives. It's the scanner that reads the bar codes on shopping items at the check-out counters in supermarkets. That red beam is a laser light which is based on exactly the same principles as my original laser.

    In the few short years that have followed my invention, laser research at industrial labs and universities has grown in various directions, as has the laser industry itself. The principle of converting electrical energy to laser light beam has been extended to extracting the laser light from semi-conductor elements, which is a whole new invention in itself and a huge industry as it provides the lasers used in Compact Discs (CD's) and other applications.

    More recently, the chemical energies in gases are being converted to laser lights to produce chemical lasers. The light outputs from a variety of gas lasers is being used as the light sources for "optically pumped" lasers.

    Academically, the field has mushroomed. At the early conferences, there used to be only a few hundred of us participating. In April 1995 at the International Laser Conference in Baltimore on the occasion of the 35th Anniversary of the First Gas Laser, I was invited to speak about the early history of the field. I gave a presentation entitled, "Gas Lasers: How Did They Come About." Thousands attended.

Ali Javan and  Donald R. Herriott, left, work with the helium-neon optical gas maser.

More of this interview is available here .

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