Lasers in Communication

Fiber optic cables are a major mode of communication partly because multiple signals can be sent with high quality and low loss by light propagating along the fibers. The light signals can be modulated with the information to be sent by either light emitting diodes or lasers. The lasers have significant advantages because they are more nearly monochromatic and this allows the pulse shape to be maintained better over long distances. If a better pulse shape can be maintained, then the communication can be sent at higher rates without overlap of the pulses. Telephone fiber drivers may be solid state lasers consuming power of only half a milliwatt. Yet they can sent 50 million pulses per second into an attached telephone fiber and encode over 600 telephone conversations.

Albert Einstein

Albert Einstein was born in Germany, on March 14, 1879. Later his family moved to Italy and then to Switzerland. In 1896 he entered the Swiss Federal Polytechnic School in Zurich to be trained as a teacher in physics and mathematics. In 1901, the year he gained his diploma, he accepted a position as a technical assistant in the Swiss Patent Office. In 1905 he obtained his doctor's degree.

During his stay at the Patent Office, and in his spare time, he produced much of his remarkable work. For his researches in Relativity he was awarded the Nobel Prize in 1921. In 1933 he renounced his citizenship for political reasons and emigrated to America to take the position of Professor of Theoretical Physics at Princeton. He became a United States citizen in 1940 and retired from his post in 1945.

At the start of his scientific work, Einstein realized the inadequacies of Newtonian mechanics and his special theory of relativity stemmed from an attempt to reconcile the laws of mechanics with the laws of the electromagnetic field. He dealt with classical problems of statistical mechanics and problems in which they were merged with quantum theory: this led to an explanation of the Brownian movement of molecules. He investigated the thermal properties of light with a low radiation density and his observations laid the foundation of the photon theory of light.

In his early days, Einstein postulated that the correct interpretation of the special theory of relativity must also furnish a theory of gravitation and in 1916 he published his paper on the general theory of relativity. During this time he also contributed to the problems of the theory of radiation and statistical mechanics.

In the 1920's, Einstein embarked on the construction of unified field theories, although he continued to work on the probabilistic interpretation of quantum theory, and he persevered with this work in America. He contributed to statistical mechanics by his development of the quantum theory of a monatomic gas and he has also accomplished valuable work in connection with atomic transition probabilities and relativistic cosmology.

After his retirement he continued to work towards the unification of the basic concepts of physics, taking the opposite approach, geometrisation, to the majority of physicists.

Einstein's researches are, of course, well chronicled and his more important works include Special Theory of Relativity (1905), Relativity (English translations, 1920 and 1950), General Theory of Relativity (1916), Investigations on Theory of Brownian Movement (1926), and The Evolution of Physics (1938).

Albert Einstein received honorary doctorate degrees in science, medicine and philosophy from many European and American universities. During the 1920's he lectured in Europe, America and the Far East and he was awarded Fellowships or Memberships of all the leading scientific academies throughout the world. He gained numerous awards in recognition of his work, including the Copley Medal of the Royal Society of London in 1925, and the Franklin Medal of the Franklin Institute in 1935.

Arthur L. Schawlow

Arthur L. Schawlow was born in New York, U.S.A. on May 5, 1921. His father had come from Europe a decade earlier from Riga. His mother was a Canadian and the family moved to Toronto in 1924. Schawlow attended public schools there, and Vaughan Road Collegiate Institute (high school).

As a boy, Schawlow was always interested in scientific things, electrical, mechanical or astronomical, and read nearly everything that the library could provide on these subjects. He intended to try to go to the University of Toronto to study radioengineering. Unfortunately his high school years, 1932 to 1937, were in the deepest part of the great economic depression. His father's salary as one of the many agents for a large insurance company could not cover the cost of a college education for Schawlow.

There were, at that time, no scholarships in engineering, but Schawlow and his sister were both fortunate enough to win scholarships in the faculty of Arts of the University of Toronto. Schawlow’s sister was for English literature, and his was for mathematics and physics. Physics seemed pretty close to radio engineering, and so that was what Schawlow pursued. Physics has given him a chance to concentrate on concepts and methods, and he has enjoyed it greatly.

A scientific career was something that few of them even dreamed possible, and nearly all of the entering class expected to teach high school mathematics or physics. In 1945 Schawlow returned to the University. It was by then badly depleted in staff and equipment by the effects of the depression and the war, but it did have a long tradition in optical spectroscopy. There were two highly creative physics professors working on spectroscopy, Malcolm F. Crawford and Harry L. Welsh. Schawlow took courses from both of them, and did his thesis research with Crawford. It was a very rewarding experience, for he gave the students good problems and the freedom to learn by making their own mistakes. Moreover, he was always willing to discuss physics, and even to speculate about where future advances might be found.

A Carbide and Carbon Chemicals postdoctoral fellowship took Schawlow to Columbia University to work with Charles H. Townes. There were no less than eight future Nobel laureates in the physics department during his two years there. Working with Charles Townes was particularly stimulating. Not only was he the leader in research on microwave spectroscopy, but he was extraordinarily effective in getting the best from his students and colleagues.

From 1951 to 1961, Schawlow was a physicist at Bell Telephone Laboratories. There his research was mostly on superconductivity, with some studies of nuclear quadruple resonance. On weekends he worked with Charles Townes on their book Microwave Spectroscopy, which had been started while he was at Columbia and was published in 1955. In 1957 and 1958, while mainly still continuing experiments on superconductivity, Schawlow worked with Charles Townes to see what would be needed to extend the principles of the maser to much shorter wavelengths, to make an optical maser or, as it is now known, a laser. Thereupon, Schawlow began work on optical properties and spectra of solids which might be relevant to laser materials, and then on lasers.

Since 1961, Schawlow has been a professor of physics at Stanford University and was chairman of the department of physics from 1966 to 1970.

Charles H. Townes

Charles Hard Townes was born in Greenville, South Carolina, on July 28, 1915. He attended the Greenville public schools and then Furman University in Greenville, where he completed the requirements for the Bachelor of Science degree in physics and the Bachelor of Arts degree in Modern Languages, graduating in 1935, at the age of 19. He was also interested in natural history while at Furman, serving as curator of the museum, and working during the summers as collector for Furman's biology camp. In addition he was busy with other activities, including the swimming team, the college newspaper and the football band.

Townes completed work for the Master of Arts degree in Physics at Duke University in 1936, and then entered graduate school at the California Institute of Technology, where he received the Ph.D. degree in 1939 with a thesis on isotope separation and nuclear spins.

A member of the technical staff of Bell Telephone Laboratories from 1933 to 1947, Dr. Townes worked extensively during World War II in designing radar bombing systems and has a number of patents in related technology. From this he turned his attention to applying the microwave technique of wartime radar research to spectroscopy, which he foresaw as providing a powerful new tool for the study of the structure of atoms and molecules and as a potential new basis for controlling electromagnetic waves.

At Columbia University, where he was appointed to the faculty in 1948, he continued research in microwave physics, particularly studying the interactions between microwaves and molecules, and using microwave spectra for the study of the structure of molecules, atoms, and nuclei. In 1951, Dr. Townes conceived the idea of the maser, and a few months later he and his associates began working on a device using ammonia gas as the active medium. In early 1954, the first amplification and generation of electromagnetic waves by stimulated emission were obtained. Dr. Townes and his students coined the word "maser" for this device, which is an acronym for microwave amplification by stimulated emission of radiation. In 1958, Dr. Townes and his brother-in-law Dr. A.L. Schavlow, showed theoretically that masers could be made to operate in the optical and infrared region and proposed how this could be accomplished in particular systems. This work resulted in their joint paper on optical and infrared masers, or lasers (light amplification by stimulated emission of radiation). Other research has been in the fields of radio astronomy and nonlinear optics.

Having joined the faculty at Columbia University as Associate Professor of Physics in 1948, Townes was appointed Professor in 1950. He served as Executive Director of the Columbia Radiation Laboratory from 1950 to 1952 and was Chairman of the Physics Department from 1952 to 1955.

In 1966, he became Institute Professor at M.I.T., and made intensive research, particularly in the fields of quantum electronics and astronomy. He was appointed University Professor at the University of California in 1967. In this position Dr. Townes was participating in teaching, research, and other activities on several campuses of the University.

Dr. Townes has served on a number of scientific committees advising governmental agencies and has been active in professional societies.