Light has been recognized as a source of energy and healing since the early days of recorded time. Ancient Greeks, Romans and Egyptians practiced heliotherapy, or healing by sunlight to treat various ailments.
In the 17th century, Sir Isaac Newton identified the visible spectrum of light when he separated light with a prism.
Albert Einstein first explained the theory of stimulated emission in 1917, which became the basis of Laser.
Photo: Albert Einstein Source: Physics Today
He postulated that, when the population inversion exists between upper and lower levels among atomic systems, it is possible to realize amplified stimulated emission and the stimulated emission has the same frequency and phase as the incident radiation.
However, it was in late 1940s and fifties that scientists and engineers did extensive work to realize a practical device based on the principle of stimulated emission. Notable scientists who pioneered the work include Charles Townes, Joseph Weber, Alexander Prokhorov and Nikolai G Basov.
Initially, the scientists and engineers were working towards the realization of a MASER (Microwave Amplification by the Stimulated Emission of Radiation), a device that amplified microwaves for its immediate application in microwave communication systems. Townes and the other engineers believed it to be possible create an optical maser, a device for creating powerful beams of light using higher frequency energy to stimulate what was to become termed the lasing medium.
Despite the pioneering work of Townes and Prokhorov it was left to Theodore Maiman in 1960 to invent the first Laser using ruby as a lasing medium that was stimulated using high energy flashes of intense light.
Hungarian physician Endre Mester was a pioneer of laser medicine, including the use of low level laser therapy (LLLT). In 1967, only a few years after the first working laser was invented, he started his experiments with the effects of lasers on skin cancer. He is credited as the discoverer of positive biological effects of low power lasers.
Photo: Endre Mester, Hungary, “Father of LLLT” and his two sons. Source: Laser World
By the end of the 1960′s, Endre Mester was reporting an improved healing of wounds through low level laser radiation. Since then scientists and doctors have understood more about the nature of light and its positive effects on the body, developing new techniques and devices for use in medicine.
|1916||Albert Einstein||Theory of light emission. Concept of Stimulated Emission.|
|1928||Rudolph W Landenburg||Confirmed existence of stimulated emission and Negative Absorption.|
|1940||Valentin A Fabrikant||Noted possibility of Population Inversion|
|1947||Willis E Lamb |
R C Retherford
|Induced Emission suspect in Hydrogen Spectra. First demonstration of stimulated emission.|
|1951||Charles H Townes||The inventor of the MASER (Microwave Amplification of Stimulated Emission of Radiation) at Columbia University – First device based on stimulated emission, awarded Nobel prize 1964.|
|1951||Joseph Weber||Independent inventor of MASER at University of Maryland.|
|1951||Alexander Prokhorov |
Nikolai G Basov
|Independent inventors of MASER at Lebedev Laboratories, Moscow. Awarded Nobel prize 1964|
|1954||Robert H Dicke||“Optical Bomb” patent. Based on pulsed population inversion for superradiance and separately Fabry-Perot resonant chamber for “Molecular Amplification and Generation system”.|
|1956||Nicolas Bloembergan||First proposal for a three-level solid state MASER at Harvard University.|
|1957||Gordon Gould||First document defining a LASER; notarised by a candy store owner. Credited with patent rights in the 1970s.|
|1958||Arthur L Schawlow |
Charles H Townes
|First detailed paper describing “Optical MASER”. Credited with invention of LASER. From Columbia University.|
|1960||Arthur L Schawlow |
Charles H Townes
|LASER patent No. 2,929,922.|
|1960||Theodore Maiman||Invented first working LASER based on Ruby. May 16th 1960, Hughes Research Laboratories.|
|1960||Peter P Sorokin |
|First Uranium LASER – Second LASER overall. Nov. 1960 IBM Labs.|
|1961||A G Fox and T Li||Theoretical analysis of optical resonators at Bell Labs.|
|1961||Ali Javan |
William Bennet Jr.
|Invented Helium Neon (HeNe) LASER at Bell Labs.|
|1962||Robert Hall||Invention of semi-conductor LASER at General Electric Labs.|
|1964||J E Geusic |
H M Markos
L G Van Uiteit
|Inventor of first working Nd:YAG LASER at Bell Labs.|
|1964||Kumar N Patel||Inventor of CO2 LASER at Bell Labs.|
|1964||William Bridges||Invention of Argon Ion LASER a Hughes Labs.|
|1965||George Pimentel |
J V V Kasper
|First chemical LASER at University of California, Berkley.|
|1966||William Silfvast |
Grant Fowles and Hopkins
|First metal vapour LASER – Zn/Cd – at University of Utah|
|1966||Peter Sorokin, John Lankard||First Dye Laser action demonstrated at IBM Labs.|
|1969||G M Delco||First industrial installation of three lasers for automobile application.|
|1970||Nikolai Basov’s Group||First Excimer LASER at Lebedev Labs, Moscow based on Xenon (Xe) only.|
|1974||J J Ewing and Charles Brau||First rare gas halide excimer at AvcoEveret Labs.|
|1977||John M J Madey’s Group||First free electron laser at Stanford University.|
|1980||Geoffrey Pert’s Group||First report of X-ray lasing action, Hull University, UK.|
|1981||Arthur Schawlow |
|Awarded Nobel Physics Prize for work in non-linear optics and spectroscopy.|
|1984||Dennis Matthew’s Group||First reported demonstration of a “laboratory” X-ray laser from Lawrence Livermore Labs.|
Ref. Steen, W. M. “Laser Materials Processing”, 2nd Ed. 1998
Microlight Corporation of America received the first clearance for an LLLT device in 2002. They performed a randomized placebo-controlled study for temporary relief of hand and wrist pain associated with Carpal Tunnel Syndrome by the ML830(R) laser. Microlight came in as a PMA because it did not have a predicate, but was changed to a Class 2 because it was not a significant safety risk. The Microlight study showed a relatively small difference between the placebo and device. However, the FDA considered the ML830(R) laser as an alternative to drugs and physical therapy that may work for some people
Avicenna Laser Technology, Inc. received the first clearance for a LLLT device with a Class IV power level on December 11, 2003. This laser was a 7.5 watt therapy laser, a significant development from Class IIIa (5mW) and Class IIIb (500mW) therapy lasers. Since 2003, a number of companies have received FDA 510k marketing clearance for both Class III and Class IV therapy lasers.
Prof. Einstein, the scientific thinker, was born in Ulm, Germany, on March 14, 1879. He joined Swiss Federal Technical University in 1896, graduating in 1900. While working at Swiss Patent office, he produced a number of brilliant research papers without the benefit of any literature facilities and discussion with theoretical physicists. A single paper, submitted by him to the University of Zurich, was sufficient for the award of Ph.D, in 1905. University of Bern appointed him as a lecturer, for his second paper and soon after University of Zurich made him Associate Professor of Physics. With in a year he was holding professorship at Swiss Federal Technical University and the German University of Prague. Soon after he was appointed to the then most prestigious post of Professor at Kaiser Wilhelm University, in Berlin. The paper on photoelectric effect was published in 1905 and the special theory of relativity in 1915. The concept of stimulated emission, which paved the way for the invention of laser, appeared in 1917. Early forties found new results in the general theory of relativity. He supported the unified field theory till the end of his life. Einstein received Nobel Prize in Physics for photoelectric effect in 1921. He passed away on April 18, 1955.
Prof. Prokhorov was born in Australia on July 11, 1916. The family moved to Russia (Former USSR) in 1923. He graduated from Leningrad State University and did his post-graduate studies at P.N.Lebdev Physical Institute, Moscow, where from he obtained Ph.D for his thesis ” Coherent Radiation of Electrons in the Synchrotron Accelarator”, in 1954. In 1955, he proposed a method for production of negative absorption, with Prof. N. G. Basov. His interests continued in microwave spectroscopy and Electron Paramagnetic Resonance (EPR). Prof. Prokhorov, constructed masers using various materials and in 1957, suggested Ruby as possible material for lasers and in 1958, prophesied lasers in the infrared region. Later, Prof. Prokhorov continued his work in solid-state lasers, multi-quantum processes and many other related areas. For his immense contribution in the area of lasers he was awarded Nobel Prize in Physics in 1964, along with Prof. N.G. Basov and Prof. C.H. Townes. He passed away on January 6, 2002.
Prof. Schawlow was born in 1921, USA and moved to Canada later. He obtained Ph.D. in Physics, from Toronto University in 1949. Soon after he joined Bell Labs in 1955, and co-authored a book, “Microwave Spectroscopy” with his brother-in-Law, C.H.Townes. In 1958, they published a paper giving the principle of a maser system that could produce output in the optical region, and subsequently received a patent for the invention of laser in 1960. Soon after, Prof. Schawlow joined the Physics Department of Stanford University, started working on molecular spectroscopy. In 1981, Prof. Schawlow received Nobel Prize for his contribution in the development of laser spectroscopy. He died on April 28, 1999 at Stanford.
Prof. Bloembergen was born on March 11, 1920 in Netherlands. He graduated from the university of Utrecht. After completing the master’s degree, he went to Harvard University, USA, after the Second World War, where he worked on nuclear magnetic resonance (NMR) in solids, liquids and gases. He received his Ph.D on his thesis on “Nuclear Magnetic Relaxation” from University of Leiden, Netherlands in 1948. He continued his research work on various aspects and phenomena of NMR and in 1956 brought out a proposal for a three level solid-state maser. From 1961 onwards, he started a new research programme at Harvard employing laser instrumentation, which later came to be known as “Non-linear Optics”. His work on non-linear optics is very widely quoted. In 1981, he received Nobel Prize in Physics for his contribution in the development of laser spectroscopy along with Prof. Schawlow and with Prof Kai Siegbahn, who pioneered electron spectroscopy.
Prof. Basov was born in Usman, Russia (former USSR) on December 14, 1922. After the Second World War in 1945, he joined Moscow Institute of Physical Engineers and studied theoretical and experimental physics. He joined P.N Lebadev Physical Institute, Moscow in 1950, where he worked under the guidance of Prof, Leontovich and Prof. A.M. Prokhorov and was awarded Ph.D. on his thesis ” A molecular Oscillator” in 1956. With his colleagues, he made tremendous contribution in the frequency stability of molecular oscillators and its dependence on various parameters and suggested methods of increasing the frequency stability. He achieved a frequency stability of 10-11 in 1962. Prof. Basov worked on the construction of quantum oscillators, investigated the production of states with a negative temperature in semiconductors, proposed different methods of achieving the same under varying conditions, developed injection semiconductor lasers using GaAs crystals. His group also made semiconductor lasers with electronic as well as optical excitation. His contribution in the development of high power short pulse (10-11sec) Nd:Glass lasers and high energy multichannel lasers, in the field of opto-electronics, study of neutron emission from laser produced deuterium plasma, proposal of a method for the thermal laser excitation giving the impetus for the development of gas dynamic lasers, laser emission in the vacuum UV range, in the development of chemical lasers employing on a mixture of deuterium, fluorine and CO2 at atmospheric pressure etc. are highly commendable. Prof. Basov was awarded Nobel Prize in physics in 1964, along with Prof. Prokhorov and Prof. Schawlow. He passed away in July 1, 2001.
Prof. Javan was born in 1928, in Tehran, Iran and came to USA in 1949. He received his Ph.D. from Columbia University in 1954 and was with Bell Telephone Laboratory, before he joining Massachusetts Institute of Technology, USA, in 1961, where he is continuing ever since, teaching and conducting research. At Bell Telephone Lab, he developed the theory of three level masers, bringing out the importance of phase coherence in microwave devices. He introduced the concept of masers without population inversion and to use stimulated Raman effect to achieve gain. During this phase of his life, he conceptualized the principle of gas laser and developed the first gas laser, namely He-Ne laser, in a continuous operation mode. This invention laid the foundation of a fantastic amount of scientific work in almost every area of physical sciences, hitherto unmatched. Prof. Javan’s contributions in the field of quantum electronics, development of gas phase non-linear laser spectroscopy, use of lasers in accurate testing the special theory of relativity and the isotropy of space, laser atomic clocks, to mention just a few, made his laboratory as the largest university research laboratory for years to come. Prof. Javan is a world leader in the field of lasers and quantum electronics.
Prof. Gabor was born in Budapest, Hungary, on June 5, 1900. In 1927, he acquired Doctorate in electrical Engineering from TechnischeHochschule, Berlin, for the development of high-speed cathode ray oscillograph. Soon after he joined Siemens &Halske AG, where he made his first successful inventions; the high-pressure mercury lamp with super heated vapor and the molybdenum tape seal. Later he, himself was stating that actually he was not after mercury lamp but after cadmium lamp, and that was not a success. In 1934 he went to England and worked with British Thomson-Houston Co, Rugby, where he started to work on gas discharge tube with a positive feed back. He developed a system of stereoscopic cinematography. It is in 1948 that he carried out basic experiments in wave front reconstruction, which later became holography and published the results. He joined Imperial College of Science and Technology, London in 1949, first as reader in Electronics and later as Professor of Applied Electron Physics. Till his retirement in 1967 he continued there and worked on the development of holographic microscope, electron velocity spectroscope, a flat thin colour TV tube, a new type of thermionic converter etc. He worked on communication theory, plasma theory, magnetron theory etc. He was awarded Nobel Prize in 1971 for holography. He passed away on February 8, 1979.
Prof. Townes was born in Green Ville, South Carolina, USA in 1915. He graduated from University of Furman, in 1935. After completing his Ph.D. in Physics from the California Institute of Technology, he joined Bell Labs in 1939 and he took the position of Associate professor of physics at Columbia University in 1948. Along with A.L. Schawlow, he conceived the idea of maser and built maser with J. P. Gordon and H.J.Zieger, in 1953. With Schawlow, he co-authored a book “Microwave Spectroscopy” and both expounded the principles of a device, which could function at wavelengths much less than maser and in 1958 proposed that stimulated radiation can be extended to the optical region, employing an incoherent source as the pump source. Subsequently, in 1960 they received a patent for the invention of laser. Soon after T.H. Maiman built the first working laser at Hughes Aircraft Company with ruby as the active laser medium, lasing at 0.6943 micron. Prof. Townes was awarded Nobel Prize in 1964, sharing the same with Profs. A.M.Prokhorov and N.G.Basov, for “fundamental work in the field of quantum electronics which has lead to the construction of oscillators and amplifiers based on the maser-laser principle”. He became Institute Professor at MIT in 1966 and University Professor of Physics at University of California, at Berkely, retiring as Emeritus professor in 1986.
Dr. Maiman was born in 1927 at Los Angeles, California, USA. His father encouraged him to love electronics and by the age of 14, he was running the company’s shop. Maiman graduated in engineering physics from University of Colorado in 1949. He wanted to study in the physics Department of Stanford University, but was rejected twice. Eventually he joined the electronic engineering department and later joined physics department, which he always wanted. His graduation work was under Nobel Laureate W. Lamb. He completed his Ph.D. from Stanford in 1955. While working under Lamb, he learnt a lot about optical experimentation, which was of immense help in his later work on lasers. The 1958, the prediction of Schawlow and Townes of Bell Labs regarding the possibility of laser operation in the visible region have made many Labs put in a lot of effort in this direction and Maiman, now working at Hughes, was no exception. Limited funding and lack of support from leading scientists did not deter him and started working on the development of ruby laser. But he had to abandon ruby as a probable laser medium since his own assistant has measured the fluorescence of ruby as just one percent, which was not encouraging at all. The other materials he tried did not have any prospects and he turned his attention to ruby again. He measured the quantum efficiency of ruby himself and the result was astounding – i.e. about 75% and once again ruby was a hot candidate. Most of the labs were trying to generate continuous wave (CW) laser and Maiman’s calculation showed that with the above results he can build a CW laser, but even with the brightest lamp available at that time could give him a safety margin of 10%, at best. At this time, he decided to use photographic strobe lamp with a brightness temperature of more than 8000 K, where as the CW DC arc lamp has a brightness temperature of 4000 K only. His calculation with the new lamp gave him encouraging results and he was convinced that the strobe lamp would give enough optical gain. He got a ruby rod from Union Carbide and silvered its faces properly, as he could ill afford expensive multiplayer coating. He surrounded the ruby rod with the helical lamp and arranged a reflector to collect the light on to the ruby rod. His efforts were well rewarded on May 16, 1960 with the appearance of the bright red ruby laser spot. With a very small budget of US $ 50,000 (which included the salary of his assistant and himself), he has beaten Lincoln Labs, IBM, Siemens, Westinghouse, RCA Labs, GE, Bell Labs, TRG and others, for the race for the invention of laser in the visible region. His research paper on the development of ruby laser was rejected by the Physical Review Letters and he submitted the same as a short paper “Stimulated optical radiation in ruby ” in Nature, which appeared on 6th August 1960. Dr. Maiman’s success was due to his strong background in electronics and physics (which was very unusual in the case of many researchers), his unconventional approach, his perseverance in spite of him being a junior employee with very limited funding and his strong beliefs in himself without following the traditional thinking on how to make a laser.
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