Hello all my A2Z challengers and blog followers. I’m still here following my theme for the month and today is the letter “L”. For this letter I’m choosing an invention which is considered one of the top 20 greatest inventions and technological achievements in the 20th century. It is the LASER.
LASER is an acronym for “Light Amplification by Stimulated Emission of Radiation”. I’ll start with a brief of the laser importance in our lives which makes it in the top 20 achievements of the 20th century. The laser’s presence in the world is ubiquitous. Its continual expansion of the boundaries of science, medicine, industry, and entertainment has resulted in fiber-optic communication, CDs, CD-ROMs, and DVDs. Without the laser, millions would be blind who now see. There would be no smart bombs, supermarket bar code readers, certain life-saving cancer treatments, or precise navigation techniques for commercial aircraft. New and popular procedures that enable one to be rid of eyeglasses, remove unsightly moles, wrinkles, and tattoos, and even streamline bikini lines, would have never come to be. The laser is now the basis for laser fusion developments at the National Ignition Facility at the Lawrence-Livermore Labs in California as well as the Pan European HiPer (High Power Laser Energy Research) Facility to produce inexhaustible, inexpensive and carbon-free energy. There are few areas in technology not influenced by the laser.
Since ancient times, people believed that rays of light carry grand and mysterious powers. As
we can find in the most famous novel from the father of Science Fiction (H. G. Wells). In “War of The Worlds” we can find aliens attacking us with “Death Rays” that can create a hell of destruction.
The laser’s history can be traced back to 1900, when Max Plank published his work on the law of radiation, which explained the relationship between energy and the frequency of radiation, essentially saying that energy could be emitted or absorbed only in discrete chunks. His theory marked a turning point in physics and inspired Albert Einstein, who in 1905 released a paper on the photoelectric effect- which proposed that light also delivers its energy in chunks, now called photons.
In 1917, Albert Einstein established the theoretical foundations for the laser and the maser in the paper Zur Quantentheorie der Strahlung (On the Quantum Theory of Radiation); via a re-derivation of Max Planck’s law of radiation, conceptually based upon probability coefficients (Einstein coefficients) for the absorption, spontaneous emission, and stimulated emission of electromagnetic radiation; in 1928, Rudolf W. Ladenburg confirmed the existences of the phenomena of stimulated emission and negative absorption; in 1939, Valentin A. Fabrikant predicted the use of stimulated emission to amplify “short” waves; in 1947, Willis E. Lamb and R. C. Retherford found apparent stimulated emission in hydrogen spectra and effected the first demonstration of stimulated emission; in 1950, Alfred Kastler (Nobel Prize for Physics 1966) proposed the method of optical pumping, experimentally confirmed, two years later, by Brossel, Kastler, and Winter.
Already in the 1930s scientists could have built a laser. They had the optical techniques and theoretical knowledge — but nothing pushed these together. The push came around 1950 from an unexpected direction. Short-wavelength radio waves, called microwaves, could make a cluster of atoms vibrate in revealing ways (a technique called microwave spectroscopy). Radar equipment left over from World War II was reworked to provide the radiation. Many of the world’s top physicists were thinking about ways to study systems of molecules by bathing them with radiation.
In 1954, Charles Townes and Arthur Schawlow invented the maser (Microwave Amplification by Stimulated Emission of Radiation), using ammonia gas and microwave radiation – the maser was invented before the (optical) laser. The technology is very close but does not use a visible light.
On March 24, 1959, Charles Townes and Arthur Schawlow were granted a patent for the maser. The maser was used to amplify radio signals and as an ultrasensitive detector for space research.
In 1958, Charles Townes and Arthur Schawlow theorized and published papers about a visible laser, an invention that would use infrared and/or visible spectrum light, however, they did not proceed with any research at the time.
Townes was not alone in his line of thought. Joseph Weber of the University of Maryland expressed similar ideas independently in 1952. And Robert H. Dicke of Princeton worked toward the same goal along a different path. Neither tried to build a device. In Moscow, A.M. Prokhorov and N.G. Basov were thinking in the same direction, and they built a maser in 1955.
Townes thought about the problems intensively. One day in 1957, studying the equations for amplifying radiation, he realized that it would be easier to make it happen with very short waves than with far-infrared waves. He could leap across the far-infrared region to the long-familiar techniques for manipulating ordinary light. Townes talked it over with his colleague, friend and brother-in-law Arthur Schawlow.
Schawlow found the key — put the atoms you wanted to stimulate in a long, narrow cavity with mirrors at each end. The rays would shuttle back and forth inside so that there would be more chances for stimulating atoms to radiate. One of the mirrors would be only partly silvered so that some of the rays could leak out. This arrangement (the Fabry-Pérot etalon) was familiar to generations of optics researchers.
The same arrangement meanwhile occurred to Gordon Gould, a graduate student at Columbia University who had discussed the problem with Townes. For his thesis research, Gould had already been working with “pumping” atoms to higher energy states so they would emit light. As Gould elaborated his ideas and speculated about all the things you could do with a concentrated beam of light, he realized that he was onto something far beyond the much-discussed “infrared maser”. In his notebook he confidently named the yet-to-be-invented device a LASER (for Light Amplification by Stimulated Emission of Radiation).
Gould, Schawlow and Townes now understood how to build a laser — in principle. To actually build one would require more ideas and a lot of work. Some of the ideas were already in hand. Other physicists in several countries, aiming to build better masers, had worked out various ingenious schemes to pump energy into atoms and molecules in gases and solid crystals. In a way they too were inventors of the laser. So were many others clear back to Einstein.
In 1960, Theodore Maiman invented the ruby laser considered to be the first successful optical or light laser.
Many historians claim that Theodore Maiman invented the first optical laser, however, there is some controversy that Gordon Gould was the first.
After the ruby laser, there were many achievements till today like the Gas Laser, Semiconductor Injection Laser, Carbon Dioxide Laser, Laser Telemetry, …. etc.
At the beginning I listed the importance of Laser in brief, now I will list some major fields that marks its importance. Of Course we can begin mentioning the famous LASIK surgery to correct your vision (I wear glasses so excuse me for this).
Revolutionizing Communications: In the 1980’s telecommunication systems relied on bulky copper cable, which was at the limits of its signal-carrying capacity and had filled the duct space under city streets with no room for expansion. Laser light beamed through a single strand of glass optical fiber, thinner than a human hair, can carry more than half a million telephone conversations, or thousands of computer connections and TV channels. Without fiber optics the internet that brings you this exhibit would not exist.
Improving Commerce, Industry and Entertainment: One of the earliest uses of lasers was in surveying. For example, to tunnel under the English Channel, separate tunnels were started from the English and French sides of the Channel. Laser surveying brought the two together with a misalignment of only a few inches over 15 miles. Today, supermarket checkout scanners, CDs, DVDs, laser holograms for security on credit cards, and laser printers are just a few of the countless consumer products that rely on lasers. Industrial lasers cut, drill and weld materials ranging from paper and cloth to diamonds and exotic alloys, far more efficiently and precisely than metal tools.
Pain free Surgery: Used in millions of medical procedures every year, lasers reduce the need for general anesthesia. The heat of the beam cauterizes tissue as it cuts, resulting in almost bloodless surgery and less infection. For example, detached retinas cause blindness in thousand of people each year. If caught early, a laser can “weld” the retina back in place before permanent damage results. Optical fibers can also deliver laser beams inside the body to reduce the need for more invasive surgery.
Advancing Science: Before any other application, lasers were used for scientific research. At first, like masers, they were used to study atomic physics and chemistry. But uses were soon found in many fields. For example, focused laser beams are used as “optical tweezers” to manipulate biological samples such as red blood cells and microorganisms. Five researchers have shared Nobel Prizes for using lasers to cool and trap atoms and to create a strange new state of matter (the Bose Einstein condensate) that probes the most fundamental physics. Over the long run, none of the uses of lasers is likely to be more important than their help in making new discoveries, with unforeseeable uses of their own.
And we even use it for connecting with the past. In June 17, 2013, airborne laser revealed hidden city in Cambodia.
LASER deserved to be our invention for the day.
If you want to learn more about Laser and how it is created, I recommend you this website. It illustrates the process very simply.