Maser and Laser in

The term MASER stands for Microwave Amplification by Stimulated Emission Radiation 

Both processes involve the generation of radiation which is unidirectional, highly monochromatic and coherent. The latter feature describes the in-phase nature of the wavelets and, hence the high intensities that can be achieved with solid lasers 

It is expected that some day LASER beams will be powerful enough to be used as death-rays and also to be used against missiles by heating them to melting point of metal 

A brief description of recent LASER devices is given in Refs 8,9 8c 11 

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Note Lasers are briefly described under Detonation, MASER AND LASER in in Vol 4, pp D436-L to D441-L... 

Lamb, W. E. Jr. (1975). Physical concepts in the development of the maser and laser. In Impact of basic research and technology (ed. B. Kursunogly and A. Perlmutter). Plenum Press. 59-111. 

The maser and the laser, I m delighted to say, have been very useful scientific tools. And that was my primary interest, to get a good scientific tool to do new things. Since the Nobel Prize in 1954 there have been twelve other Nobel Prizes that used masers or lasers as tools. That doesn t mean that the masers and lasers produced the Nobel Prize, but the person who did the Nobel Prize work was able to do things that he couldn t do otherwise, using masers and lasers as tools. 

Prof. Townes, who is presently with the University of California, Berkeley, California, kindly consented to not only attend the ceremony, but also to give the keynote address. His remarks capture the excitement and energy of the early days of maser and laser research, and also touch on the breadth of applications today. He also points out that 2004 is also the 50th year of the operation of the first maser, making this a threefold anniversary. Prof. Townes talk is included in these Proceedings under the title Birth of the Maser and Laser . 

In a celebrated paper, Einstein (1917) analyzed the nature of atomic transitions in a radiation field and pointed out that, in order to satisfy the conditions of thermal equilibrium, one has to have not only a spontaneous transition probability per unit time A2i from an excited state 2 to a lower state 1 and an absorption probability BUJV from 1 to 2 , but also a stimulated emission probability B2iJv from state 2 to 1 . The latter can be more usefully thought of as negative absorption, which becomes dominant in masers and lasers.1 Relations between the coefficients are found by considering detailed balancing in thermal equilibrium... 

MASER and LASER. Accdg to Time magazine of July 12, 1968, pp 42—9, physicists A. Schawlon C. Townes described in 1958 a device which was a variation of Townes earlier Nobel prizewinning invention named MASER. 

Use Production of tantalum rare-element optical glass intermediate in preparation of tantalum carbide piezoelectric, maser, and laser applications dielectric layers in electronic circuits. 

S. Spin-spin interactions in insulators 351 9. Maser and laser experiments 389... 

What has not been included As mentioned, the lines of CO2 and N2O lasers themselves are not included. They are very numerous, and are already catalogued in a number of references (see Chapter 5). TEA-laser pulsed lines, or any others with pulse lengths less than 1 /iS, are not included. Stark-shifted and multiple photon lines are excluded, as are molecular beam masers and lasers relying on chemical reactions for their excitation. 

Townes s academic life continued. He served as provost of MIT from 1961 to 1966. In 1964, Townes received the Nobel Prize in physics for work in quantum electronics leading to construction of oscillators and amplifiers based on the maser-laser principle. He was named university professor at the University of California-Berkeley in 1967. There he worked for more than 20 years in astrophysics. Ironically, this field is one of many that were transformed by die laser, and Townes often tised lasers in his subsequent research. 

First, let s look at what current lasers and masers do. Lasers vary in size from single atoms, or submicroscopic size, to lasers as big as tall buildings. Well, the single atoms in small lasers produce fantastically small amounts of power - let s say, 10 16 watts. The big ones have produced as much as 10+16 watts - that is, ten million billion watts, more than we have from any other kind of source. Now, that lasts for a short time, because it would be too expensive to have it on all the time, of course. Nevertheless, it s very powerful, and that great power produces an intensity which allows us to study and to understand new states of matter with very high energy concentration. 

Now today, we have found about a hundred different masers in space and some lasers. The difference between a maser and a laser is of course only in the wavelength. But there are some astronomical systems where infrared is getting amplified. Now as has been pointed out, amplification in interstellar space doesn t involve resonances, but it does involve stimulated emission. You know, somebody could have seen these interstellar masers in the radio regions of the spectrum many years ago. Anybody who used the radio technology of 1936, and looked up into the sky, could have detected this water frequency. They didn t bother to look, but it was there all the time. So now we know, lasers have been there for billions of years. Masers have been there billions of years. So that s another way we might have discovered them, but we didn t. Now I emphasize this to indicate that we need to search, we mustn t be too confined by what we think is going to work, we ve got to explore. 

It is especially fitting that this Course on Optical Chemical Sensors should be the occasion to recollect the early days of the laser and honor those whose vision and brilliance opened up such a rich and productive area of science. Laser-based chemical sensors serve as valuable research tools while at the same time they have found many practical applications - in this sense, they offer a representative snapshot of the entire field of masers and... 

Soon after the first successful experimental verification of an optical maser the search for possible new laser media began and, especially in the infrared region, numerous stimulated transitions were discovered many of them had not even been observed previously in spontaneous emission... 

Samarium is used to dope calcium fluoride crystals for use in optical masers or lasers. Compounds of the metal act as sensitizers for phosphors excited in the infrared the oxide exhibits catalytic properties in the dehydration and dehydrogenation of ethyl alcohol. It is used in infrared absorbing glass and as a neutron absorber in nuclear reactors. The metal is priced at about 3.50/g (99.9%). Little is known of the toxicity of samarium therefore, it should be handled carefully. 

G. Rempe, H. Walther, The one-atom maser and cavity quantum electrodynamics, in Methods of Laser Spectroscopy, ed. by Y. Prior, A. Ben-Reuven, M. Rosenbluth (Plenum, New York, 1986)... 

The idea of amplification of EM radiation by stimulated emission was first realized for microwaves. The MASER (microwave amplification by stimulated emission of radiation) was developed in the Soviet Union in the early part of the 1950s, particularly by N. Basov and A. Prokhorov. At the same time, it was developed by C. H. Townes, A. L. Schawlow, and others in the United States. Originally, the laser was called light-maser, but the name was changed to LASER (light amplification by stimulated emission of radiation). 

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