L A S E R S
Did you know that some laser beams are small enough and powerful enough to drill two hundred holes on a spot as tiny as the head of a pin?
The first major advancement in laser development came in 1954. This was the year that Charles H. Townes, an American physicist, created a device that amplified microwaves. This device was actually called a maser at first, which was short for Microwave Amplification by Stimulated Emission of Radiation Masers. It produced microwaves of just one frequency. Then the laser was developed from the maser.
Several people have been accredited for the development of the laser’s basic design. These people are as follows: American Arthur L. Shcawlow, the Russians Alexander M. Prokhorov and Nikolai G. Basov, and the American Gordon Gould. But the first laser was constructed in 1960 by American physicist T.H. Maiman and it is still one of the most powerful lasers available. This laser used a ruby rod for its active medium, which is its way of producing light. Ali Javan then created the first gas laser later in 1960. Three separate teams of American scientists operated the first semiconductor laser in 1962. Then in 1966, the American physicist Peter Sorokin built the first dye laser.
To begin with, I will explain the definition of a laser: It is a device that produces a very narrow powerful beam of light. A laser light is a narrow beam of light, in which all the waves are traveling exactly at the same length and moving together as one. A laser light is made up of only one wavelength and it is a single pure color, while a normal light has many different wavelengths or colors.
The most common laser has three parts to it. They are energy source, an active medium, and optical cavity. An energy source can be anything that can give energy to the active medium through a process called “pumping.” Lasers often use electricity; usually a device called a flash lamp, as the energy source. An active medium is any material that can be used to create a laser light. The optical cavity is the structure that encloses the active medium. Most cavities have mirrors on both ends, one that fully reflects light and another that partially reflects light. The laser beam actually exits through the mirror that is partially reflecting.
The central process of the laser is called stimulated emission. Stimulated emission works by one photon, which are packets of light energy, produce another photon. This production of the second photon doubles the amount of light energy present, which is called amplification. The only way for stimulated emission to occur is if most of the atoms are in their exited state, which means the atoms have a higher amount of energy than normal. More atoms must exist in the excited state than in the ground state (opposite of exited state) for amplification to occur. When more atoms are in their excited state than in he ground state it is called “popular inversion.” The energy source is the device that helps the laser get popular inversion by pumping energy into the active medium so that the energy excites the atoms. The two mirrors that are located in the optical cavity are reflecting the photons back and forth through the active medium. When the photon and excited atoms meet they produce a chain reaction of stimulated emissions, which will double the amount of light energy present and that will produce a flood of light.
Lasers are use for many different things. They are most valuable in recording, storing, and transmitting information. Lasers are also used in scanning, measuring, heating, and guiding. A lot of lasers are also used in surgery and medical work. It is the purity, intensity, and parallel nature of laser light that makes lasers so useful.
Lasers are most commonly used in the recording of music, motion pictures computer data, and other materials on special disks called a “CD” , which is short for compact disk. Bursts of small light record information in the form of tiny pits. Lasers can also read and play back the information it has recorded on the CD. More lasers are used in CD players than in any other product.
Probably a laser’s greatest uses are in the field of fiber optics. This is used largely in telephones. It changes the electrical signals into tiny bursts of light so that it can carry more information and at a greater speed. It is ideal for this because it can get all of its information into a tiny fiber, which allows a large amount of television, telephone, and other data to be transmitted cheaply.
Scanning is another great use for a laser. Most people have seen a scanner being used to scan their products the grocery store. This involves the movement of laser beams over the surface of an item. Also scanners can keep track of books in libraries, sort mail, and read checks in banks.
A laser beam can produce a large amount of heat also. An industrial laser can produce a beam that has up to a thousand watts of power. In surgery, lasers are used on the eye, because highly focused beams of light can close off broken blood vessels on the retina. Lasers can also reattach the loose retina. Doctors can also use lasers to shatter gallstones, treat skin disorders, and remove birthmarks. They use them as much as possible because they reduce bleeding and damage to healthy tissue.
People also use lasers in measuring and guiding. An object’s distance can be determined by measuring the time pulses of the laser light. They can even use a laser to measure the distance to the moon. Scientist use a high powered laser to determine the distance. People use laser beams in guiding because they produce a straight line, which is a valuable tool for guidance. Construction workers use beams to align walls, ceilings, sewer pipes, and water pipes.
Another thing we use lasers for is to study fusion reactions. In an experiment several ultraviolet beams are shot at a tiny pellet of hydrogen at the same time. This causes some of the hydrogen atoms to fuse together releasing large amounts of energy in the process.
One thing you don’t hear much about in using lasers is isotope separation. Scientist are trying to separate the fissile isotope of uranium called U-235. A dye laser is being used to pump copper vapor to ionize selectively the U-235 isotopes in uranium vapor.
There are four main types of lasers and a couple that aren’t widely used. The main lasers are solid-state, semiconductor, gas, and dye. Solid-state lasers use a rod that is a solid material as the active medium. The most common solid-state laser uses an element called neodymium. Usually solid state lasers use flash lamps for the energy source. ND:glass (ND = neodymium) lasers are a certain type of laser and the world’s largest laser. It is the size of a football field. ND:glass lasers are used widely in industry to cut through pipes and weld together metals. Semiconductor lasers use two layers of semiconductors and the layer that lies in the middle is the active medium. The smallest types of laser beams are the semiconductor beams. One kind is as tiny as a grain of salt, and another type is so small you can only see it will a microscope These are the most commonly used lasers because of their size and because they don’t need as much power. The size makes them ideal for use in CD players and fiber-optic communications.
Gas lasers use a mixture of gases as the active medium. The most commonly used mediums are carbon dioxide, argon, krypton, and a mixture of helium and neon. Gas lasers are used most in entertainment, holography, and eye surgery. The most important and efficient of the gas lasers is the carbon dioxide laser. It converts the most amount of the energy from the energy source into the beam of light. It converts from 5 up to 30 percent of its energy while others only convert around one percent. These are often used to weld metals and cut metals, as well as a scalpel and range finder.
Dye lasers use dye as the active medium. The dye is dissolved in a liquid and the most commonly used liquid to dissolve in is alcohol. To pump the atoms full of dye, a second laser is usually used. The most important property of dye lasers is that they are tunable and they can be adjusted in size and color.
Another type of laser you don’t hear about much is a chemical laser. A gas is created and pumped into atoms by chemical reactions. They usually use a gas-dynamic configuration so that all excess heat is quickly removed so that no damage will occur.
The only laser to use a no-material medium is a free electron laser. These lasers obtain emission by having an electron beam traveling at nearly the speed of light through a magnetic field in a vacuum. Like the dye lasers these lasers can also be tuned by changing the velocity of the electron beam or the period of the magnetic field.
Since the 1970’s laser advances have reached new heights. Lasers are beginning a whole new era in home entertainment, communications, and computer technology. Lasers have also revolutionized many fields of science including spectroscopy, interferometry, holography, and metrology. Researchers think that the most exciting and revolutionary uses of lasers have still not been discovered.
Some good aspects of lasers are that they are making things much easier to do and a lot safer. Like in surgery doctors can be more accurate and not damage healthy skin. It really helps in a lot of cases.
There is at least one bad aspect of lasers. They can be used as weapons. People can cause a lot of harm using lasers, like if they flash it in someone’s eyes. That can either blind them for life or seriously damage their eyes. It can also do damage to a lot of electronical equipment like it can makes computers crash, and shut cars down.
So lasers are a very powerful tool that can be used for good or bad. Lasers are used for a variety of things, and I can’t wait to see what they will do with them next.