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Douglas L. Jamerson, Jr. & USF
Written by USF's Dr. Barger & Dr. Gilbert
The Engineering Edge
Article 2, Vol 6
LASERS are in the Engineering Tool Box
 News this month from Stockholm Sweden is focused on Nobel Prize Winners. This year’s winners in Physics are Roy Glauber, John Hall and J. Robin Warren. The prize was awarded for their investigation of the source, properties, and interaction of Light Amplified by Stimulated Emission of Radiation (LASER) light with atoms. This effort summarizes the systematic and scientific investigation of light that began with Isaac Newton (1666) almost 350 years ago.
Once a scientific curiosity, LASERs soon were put to many uses. The listing of engineering accomplishments based on this ever increasing understanding of light continues to keep pace with this expanding knowledge base. These accomplishments also mirror the level of that knowledge at the same point in history. For example, no self-respecting late 17th or early 18th century pirate would be caught dead without his trusty “spy-glass” telescope tucked in his braided belt. In addition, 100 years after Newton studied light rays and light colors, Benjamin Franklin developed the first pair of bifocal glasses.
Today, the engineering applications of LASER light are almost endless. Civil engineers use LASER transits for survey work. Electrical engineers use LASER light to send messages through fiber optic cables. Chemical engineers use LASAR beams to selectively react specific types of molecules within a solution of many different types of molecules to make a life saving drug. Mechanical engineers use LASERs to position robotic arms to pick up a load without damaging it. Actually, engineers have only begun to explore the applications of LASERs as a way to solve problems.
From a practical perspective, it is a bit hard for Jamerson students to develop engineering application for LASERs. The engineering development of the materials still uses expensive tricky-to-work with equipment. In addition, the actual incorporation of a LASER beam into an application requires a mathematics and science background that is still beyond most college students. It is one thing to imagine a LASER curtain that protects the Declaration of Independence when it is on display, and quite another thing to complete the engineering requirements to actually build such a protection system. However, this reality recognition does not diminish in any sense the importance of Jamerson students understanding the properties of materials that cause LASER beam creation.
As suggested earlier the quest for the LASAR began 350 years ago without a hint that LASERs were even possible. In 1666, Newton began experiments with a thick triangular piece of glass called a prism. He discovered that if he let a bright ray of sunlight shine through a hole in a shade that is covering a window. The light would separate into rainbow colors after passing through a prism in a dark room but, no arrangement of prisms would reduced the number of colors within the rainbow display to a single (monochromatic) color light. However, Newton did discover that if he simply inserted a second prism upside down in that rainbow light stream he could convert that rainbow colored light back into its original beam of white light. By 1801 Thomas Young had expanded Newton ’s observations and believed that the rainbow light was a collection of individual light waves with each light wave representing a different shade of color. He realized that there were many, many more shades of rainbow colors in the light that came through a prism than humans could see. (There are many human beings that do not see all of the color shades within a rainbow that most of us do see, while some animals see light waves that we cannot see.) Today, we call all of the light waves we can  and can not see the electromagnetic spectra. The visible spectra is the subset collection of light waves we can see.
Even with all of this background knowledge about light waves, it was not until the middle of the 1960’s before a LASER light beam was discovered. This 160 year delay from Young’s investigations was due to our lack of knowledge about the atom. It took over 50 years after Niels Bohr proposed an idea (model) in 1913 for the structure of an atom before a LASER was created.
The Bohr model for an atom seems simple today. He believed that an atom was made of positive particles, protons, in the nucleus and an equal number of negative particles, electrons, in various orbits surrounding this nucleus. Atoms are different from each other if they have different numbers of protons in their nucleus. Using these ideas and others developed in the first half of the 20th century, scientist finally figured out how to generate a LASER light beam. They used an atom that possessed many protons and therefore also had electrons in many of its orbits. They knew that electrons do not always stay in their own orbits. If energy was available, an electron could absorb that energy and move to an orbital further from the atom’s nucleus. If that same electron returned to its original orbital, it could emit the excess energy it possessed as light. When a lot of electrons from a lot of orbitals moved to orbitals closer to nucleus, many different colors (light waves) of light can be detected. Finally, they figured out how to have electrons from just one outer orbital move back to the same inner orbital every time. When that occurs, only one color (one wavelength) of light is emitted and a LASER light beam that consists of thousands of waves of the same color (and therefore, having the same amount of energy) of light is the result.
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