If you wish to technically broach the concept of LASER, the first thing you should probably learn is that LASER is an acronym and it expands to Light Amplification by Stimulated Emission of Radiation. But to a layman, a LASER device is just another light source with a special property. It can be channelized into a single straight line and is visible from a longer distance while normal light sources just fade away into convex beams.
Now, as the book "LASER: Light of a million uses" rightly points out, the uses of a LASER light source are plenty, but what are you buying it for? You may have seen professors dangling a pen during presentations and using it to point at screens. Well, that's the simplest form of a LASER light and it is commonly used as a pointing device at slide shows and presentations. It does not matter if you use red LASER or green LASER as long as it serves the purpose. With the rate of pollution due to fireworks, it would be nice to have a LASER light display instead of smoke and fire all across the sky on the fourth of July or Guy Fawkes' Day. If you're a pyromaniac, you may even choose to use LASER to ignite stuff like paper, cardboard boxes, cotton and matches. Use your creativity to even light a cigarette or a fat Cuban cigar if you are a smoker.
In glass cutting industries, they are used for cutting glass with an impressive amount of precision and accuracy. This has recently been extrapolated to many other industries. If you're in construction, this can be used to even measure distances and depths of structures. Its practical application in science extends to the fields of biology, spectroscopy and chemistry. A regular camper might consider the use of LASER beams to scare away wild animals. Unless you're a soldier, you would not be carrying a high power LASER beam generator of more than 1W power because it becomes a potential weapon. Battlefields usually have a lot to do with LASER where they are used as weapons and beacons.
While you do not have to be a scientist, a little bit of scientific knowledge would help you understand how LASER is generated. The expansion of the term gives a very succinct description of how a LASER beam is created. Let's take you back to the basics of matter; as you know, all matter is made of molecules which in turn are composed of tiny particles called atoms. An atom has a central nucleus made of protons and neutrons; small negatively charged particles called electrons circulate the nucleus in a way similar to that of the sun and the planets in the solar system. This is just a depiction of the balanced state of an atom. Consider that the atom is heated or given a bit of energy in some form – this causes the electrons in its orbit to go to an excited state resulting in the formation of an excited atom. If you extrapolate this concept to an object which contains millions of atoms, you have myriad atoms in their excited state. But how is the beam of red light generated? The answer is simple – the tendency of atoms to go back to their balanced state results in the creation of a light energy packet called a photon. It's something like this – somebody gives you money, you become extremely excited and then you decide that you were better off when you did not have any money, and that there are a million other people like you dumping all their money in a lake. This way, when all the photons come together and travel in a single direction, it forms a LASER beam.
It does not take much to be ignored by small LASER sources. The cool applications that it has joins people from all walks of life – professors, architects, engineers and builders, security forces and even kids. Why? If you have to ask why, it just means that you do not know about LASER beams. What could be cooler than having a LASER light source in your hand? You can have light shows in different colors and have a lot of fun flashing it into your neighbor's house while he struggles to comprehend where the source of the small red dot lies. You can even stand out from the smoking crowd in lighting your cigarette with a LASER light while people are using spirit lighters.
There are different kinds of LASER pointers in the market and their size and structure depends entirely on the application for which they are to be used for. For instance, the smallest points are generally used by lecturers during presentations. Combination lasers can be used in LED torches and even for disco lights. If you are a clubber, you would have seen red, green and blue lights coming out from the ground for special effects while dancing at clubs. They are dual or combination Lasers. Have you seen red dots appearing on a person's chest or forehead in movies when he is being targeted by the SWAT team or other special forces? Well, they are LASER gun-sights.
If you own a LASER pointer, you would probably have shone it into the sky and checked to see if you can see how far it reaches. A small pointer LASER would probably not even be visible, while a larger light source may stretch through a certain distance; the only determinant of the brightness and the distance at which a LASER beam shines is the power of the beam. LASER pointers can vary from 5mW and go up to 300mW – these are available to the common public. Attempts to purchase beams of a higher power capacity require you to get attested documents stating the reason for the purchase. Of course, higher-power LASER beams are expensive. The more powerful cool gadgets get, the more will be the number of questions as to the danger it poses and the legal issues that accompany it. Unless you're a doctor performing a LASER eye surgery, you would not want to shine your LASER beam directly into a person's eyes; This could cause permanent damage and even blindness. Shine a LASER of mediocre power at a single point for too long and you'll notice that the target becomes warm. Shining a higher power beam directly on the skin could cause burns and heat boils. This leads us to the next question of whether it is legal; the answer lies with how you use these beams. You could have arrested for shining LASER beams at airplanes and ships; the list has been recently appended with "football matches" when a fan chose to shine a LASER directly on the ground which affected the course of the game.
If you're just amazed by these things and are just looking to own one of these beauties, eBay or any of these auction sites would be a good choice for you. They come really cheap; however, the catch is that you're not going to get the product in the advertisement. So, if you're a person who can tell between a 5mW beam and a 20mW beam, look somewhere else; if you do not, go ahead and use auction websites. Let's say you are a professor looking to acquire a LASER source for a spectroscopy experiment; in this case, stay away from eBay. Instead, browse through the many online forums that have LASER pointers as the core topic. K-mart, Wal-Mart and Target are good places to start while you can also visit the websites of specialty shops online to order your beam.