The ultimate guide to lasers

 

When somebody hears the word laser, it is quite likely that the first thing that comes to their mind will be: a lightsaber! As much as all of us would like to start ranting about the Jedi knights and their adventures when lasers are mentioned, we are not there quite yet. However, that doesn’t mean that this topic can’t be interesting! Lasers are becoming more and more an important part of modern life in different areas of industry. It is likely that the majority of appliances that you use everyday owes their functionality to laser technology in one way or another. If it sounds too unbelievable, keep reading and you will certainly change your mind.

 

What is a laser and how does it work?

To put it as precisely as it goes, the word laser is an acronym and it stands for “light amplification by stimulated emission of radiation”. Naturally, this does not mean a lot for the most of us, so let’s try to figure it out! To put it simply, a laser is a tube that concentrates light and turns it into a beam that can be clearly seen with your bare eyes.  

 

 

Now, how do you make those colourful sensations? First, it is important to understand the difference between laser and regular light. Here, we’ll compare light with water. Regular light is similar to still water. Now, imagine trying to make waves in it, let’s say, with your hand. At first, the waves would be small, but as you repeat the process, they would grow bigger and more powerful. In theory, if you repeated the process enough times (around a million) and had enough water, you would create a giant wave. Similarly, by adding energy to light waves, a laser makes them more concentrated and visible.

 

 

Having the basics covered, let’s go a little bit deeper. It’s time for science! As we have already mentioned, laser beams are precise and concentrated beams of light. They are made when a large number of atoms (measured in billions) emit an even larger number of photons (trillions) at the same time. The way atoms produce light is very important when speaking about lasers, so we’ll briefly take a look at that. Everything around (and including) us is made from atoms. They look like our Solar system, consisting of the nucleus in the middle and electrons which orbit it. Electrons have different levels of energy and the closer the electron is to the nucleus, the less energy it has. When they are in their regular “ground” state, the electrons use their own orbitals, but when an amount of energy is added to the atom, and electrons absorb it, they move further from the nucleus and take the higher energy level orbitals. When this happens, the atom becomes “excited”. However, this state is not stable and the atom tries to return to its ground state as soon as possible. Then, it gives off the energy it absorbed in the form of photons and in this way the atom made light.

 

 

 

 

 

 

 

 

Finally, the making of laser light. Basically, a laser consists of two things: a medium (special crystals, glass, liquid or gas containing electrons that can be stimulated) and a source of energy to stimulate it with (a flash tube or another laser). The source of energy excites the atoms in the medium and they release photons. Some of these photons bounce back and excite the other atoms, and some of them escape. The ones that escaped are, in fact, the laser beams that we see. 

 

 

Now when it’s all crystal clear, we only have one thing left: the lightsabers from the very beginning! Like we all know, they come in many different colors and it is the same with lasers. The very fact that we can see laser beams is because they contain only one wavelength, their light is monochromatic. The wavelength and the color of our laser depend on the amount of energy that is released when the electron leaves its “excited” state and returns to its original place. The most common colors of a laser are: bright red or bright green and invisible (infrared and ultraviolet).

 

The invention of lasers

Like it is the case with many wonderful inventions, a laser wasn’t invented and made by a single person. A lot of theoretical research had to be done until the making of the first practical laser. So, let’s take a look.

 

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The laser invention can be traced to the early 1900s when distinguished scientists like Max Planck and Albert Einstein begin to venture into the world of exploring this fascinating subject. First, Planck published his work where he explored the law of radiation and illustrated how energy can be emitted and absorbed. Einstein followed in his footsteps and published a paper on the photoelectric effect where he explained the concept of photons in 1905, and later in 1917, he gave his contribution by demonstrating how a photon can transfer its energy to an atom and push it into the “excited” state (stimulated emission). 

This theoretical background served as a starting point for Arthur Schawlow and Charles Townes who invented maser in the late 1950s. Masers are important in our story because lasers evolved from them. Masers are very similar to lasers in the way how they function, and the main difference between them is that masers emit microwaves and radio waves. The inventors of a maser both got the Nobel Prize in Physics. 

In 1957, Gordon Gould, Townes’ former student, made a sketch of laser and he was the first one to ever use the acronym “laser”. Unfortunately for him, he didn’t patent it on time and got patent for only a part of the invention. The person who actually built a laser didn’t have luck either. His name was Theodore Maiman and he operated the first functional laser in 1960. However, his article describing the invention was turned down by the Physical Review. But, in the end, he got his place in the National Inventors Hall of Fame in 1984.

 

Practical uses of lasers

Even though it was underestimated when it first came to exist, a laser has a lot of practical applications that make our world the way it is. 

 

Science

The invention of lasers had a revolutionary influence on science in general. For example, one of the primary purposes of lasers was to accurately measure long distances. One of the first practical implementations of a laser as a measuring tool was in 1969 when the Apollo 11 crew left a mirror upon making the first steps on the Moon. That mirror was necessary for the scientists back on Earth in their mission to accurately measure the distance to the Moon with a laser beam.

 

 

Lasers are also crucial for spectroscopy (exploring the structure and properties of various materials), heat treatment (it allows hardening particular areas of surfaces without any damage), photochemistry (initiating chemical reactions with brief but intense laser pulses), laser scanners (reading linear codes quickly), laser cooling (cooling matter on the atomic level), nuclear fusion (by stimulating different atoms with extremely powerful, short pulses of light the scientist hope to improve the fusion process, but it is still in progress), microscopy (lasers are used here to make clear microscopic images).

 

Medicine

Many would argue that medicine is the area where lasers found their most useful purpose. The main advantage of lasers over the traditional methods in medicine is the fact that lasers are less invasive and much faster. They are used in almost every branch of medicine, but probably the most common and well-known usage of lasers is a laser scalpel. The main advantages of a laser scalpel are that it makes the incision of a constant depth without any variations, it cauterizes the incision (large blood vessels not included), and it can be used for very small interventions as it doesn’t damage the surrounding, healthy tissue. 

Lasers are also efficiently used to clear the arteries. They are here used in combination with the optic fibers that make it possible for the doctors to see the inside of an artery. They insert the optic-fiber array in an artery (usually in an arm or a leg) and navigate it slowly to the place of the blockage. Then, they destroy the plaque with the laser.

 

 

Another branch of medicine that has largely benefited from a laser is ophthalmology. Here, lasers are used for removing the blood vessels that can damage the retina, treating glaucoma, or correcting the most common vision problems.

Also, it is worth mentioning that lasers are widely used in cosmetic surgery and cosmetic industry. Some of the most common procedures involving lasers are treating different kinds of birth stains, removing tattoos and hair removal procedures.

Last, but not the least important is the role lasers play in dentistry. They will certainly make the visits to the dentist a lot less stressful and painful. Lasers could replace that hideous sound and well-known sensation of a dentist’s drill. It would all be pain-free and the post-operative swelling would be significantly reduced.

 

Communication

Lasers are the also the starting point of any dimension of modern digital technology. Even though we barely use CDs anymore, they are dearly remembered. When playing or burning CDs and DVDs, a laser beam is used to read or write a pattern of data on the disc which then can be read by a computer or a player.

 

 

With some laser help, the Internet has become a much larger, faster and better place. They enabled transferring much larger amounts of data quickly by sending it via light through special optical fibers made out of glass. This application of lasers is studied by photonics and the scientists are hoping that optical fibers teamed up with lasers will completely replace electrical wires in the years to come, because in this way, they will eliminate shortcomings like interference and heat problems.

 

Commercial and industry

Lasers have found their place in industry and manufacturing. There are two categories of application of lasers in industry depending on their power. The first category is material processing and the second one is micro-material processing. On average, the lasers used in material processing have optical power over 1kW, and those used in micro-material processing are less powerful and their optical power never crosses the threshold of 1kW. The main difference between the two (except their power) is that in material processing the change a laser makes is visible (welding, brazing, hardening) and in micro-material processing the change cannot be seen with the naked eye, the structure of material is changed (production of smartphone screens, tablets and led TVs).

Worth mentioning is also the role of lasers in the printing industry. When it first became popular, laser printing caused quite a turmoil in the printing business: it was faster and more cost-effective. Also, this innovative technology gave its users the precision and flexibility they needed. With laser printing, it is possible to use different materials, the possibilities are almost limitless: from paper and fabric to wood and metal. Another technique that wouldn’t be possible without the laser technology is 3D printing. So now, not only can we print nice images we like, but also make a tridimensional object we sketched. 

Laser cutting has also been an important part of the industry since its first appearance in 1965 when it was used for drilling holes in diamond dies. At present, it is most commonly used in industry and manufacturing, but small businesses and hobbyists are also becoming the regular users. The main advantage of laser cutting is its precision, but it is also valuable because of the fact it is not limited to cutting only flat-sheet material.

Here’s another application of laser that may sound a little bit silly, but it is incredibly efficient and ecology-friendly: lasers are often used as bird deterrents. Since birds see a laser beam as an obstacle, they get scared and fly away. These lasers are usually installed near agricultural land, airports or industrial sites.

 

Military

Lasers can be used in many different ways when it comes to military purposes. The first thing that will probably come to everyone’s minds regarding military and lasers is an energy weapon. There were many attempts of trying to build such weapons like the Boeing YAL-1 which had an airborne laser weapon which was intended to be used as a missile defense system. Another project that was intended to serve as a defense mechanism was the Strategic Defense Initiative (SDI, it had a nickname “Star Wars). It was planned for the SDI to use laser beams and destroy the incoming intercontinental missiles from the ground or from the space. Neither of the two inventions mentioned was accepted by the general public.

However, lasers do have a very important place and multiple purposes in the military. For example, they are used to disorientate, or on the other hand to guide the missiles. When used to improve different kinds of firearms, lasers can be seen in the form of a laser sight or eye-targeted lasers. A weapon with a laser sight is more precise since it has a small, usually red laser diode which shows where the bullet will be fired. An eye-targeted laser is a non-lethal weapon which uses low-power laser light to temporarily impair the enemies’ sight and o disorient them. It causes no permanent damage to the human eye.

 

Entertainment 

And now, one brighter topic: entertainment. Anyone who has been to at least one concert or a show of some other nature must have seen our lasers in practice. The laser technology is very popular in the entertainment industry because of different possibilities it offers: different colors and shapes of laser beams and the very effective combination of lasers and smoke or mirrors.

 

 

Another equally entertaining use of lasers is a game Laser tag. The players use guns that fire infrared laser beams and there is also a certain number of infrared-sensitive targets. The rules are simple: you need to “hit” the infrared sensitive target whether they are located on the vests of your opponents or on some other moving target. This game became popular in the 1980s and it can be played both indoors and outdoors. It is very similar to paintball, but unlike paintball, it is completely painless because there is no physical contact with the “missile”. Since it’s invention in 1979, it has been attracting players of different ages and profiles.

 

Lasers in the movies 

Although it may seem that we mentioned all the possible industries that have ever used lasers, it’s not true. Lasers have always been an endless source of inspiration for the movie makers. If a supervillain needs a tool of intimidation threatening to slice someone in half, look no more, just find a laser, if the whole planet has to be blown up, guess what, the lasers are still the answer, and of course, those lightsabers.

 

Photo credit: http://www.centives.net

 

Upon hearing the words laser and movie in the same sentence, any sci-fi aficionado will definitely say (yell): the Death Star blowing up Alderaan. Even if you don’t particularly enjoy the genre, you would have to admit that this laser specimen was rather impressive (and efficient). Also, this movie is full of impressive laser gun fights and the very useful laser shields that have saved our heroes more times than I can count.

 

Another unforgettable scene with lasers can be seen in Goldfinger where their laser that can “project a spot on the Moon, or at closer range cut through solid metal”. A gold table paid its price for the sake of a very slow demonstration of the laser’s destructive power, but this theatrical streak of our villain gave 007 enough time to talk his way out of this situation before it gets too messy. 

Naturally, we can’t talk about movies and lasers without mentioning a case when a protagonist has to go through a laser net. It can be seen in Oceans 12, but this time it’s even harder: the laser beams are moving! In order to steal the Fabergé Egg, Toulour has to dance his way through a hall equipped with moving lasers and, of course, he makes it.

 

If you are not a fan of slicing and blowing up, you will definitely like the laser from Hitchhiker’s Guide to the Galaxy. There, you can see a laser incredibly similar to a small lightsaber, but here they use it to make a toast. They definitely proved all of us who thought that lasers can only be devices of torture and destruction wrong (and made us hungry while doing it).

 

Lasers in the future

Like everything else nowadays, science and technology are also advancing at an incredible speed. Lasers are an important part of that advancement. They are a useful tool when discovering new knowledge and transferring the newly found information faster. Although it may be difficult to imagine what inventions will be found and how the laser technology will help, there are a few of them that are in the pipeline.

 

 

For example, let’s take holograms. Some scientists claim that we will have a tri-dimensional holographic cinema, and the more ambitious ones say that the television will become holographic, as well. Another potential breakthrough could be holographic telephone system (just like in Star Wars, but hopefully with a better signal). 

Another application of lasers that is already in progress has to do with medicine. Remember how in Star Trek they use light to heal wounds and any other injury? Well, we are not exactly there yet, but lasers are used in surgery and the scientists are working on improving the laser technology to become even more powerful and easy to use.

Another important aspect of our society is energy and how to create it from renewable resources. The scientists offer several options how we could use lasers as sources of unlimited energy, but the most realistic one involves nuclear fusion. They believe that lasers can be employed to facilitate the nuclear fusion, but they need to do much more research and improve the lasers we have today. 

What else can we expect from the laser technology in the future? Who knows, but it will definitely be exciting to see. So, relax and wait for your lightsaber or laser toast maker, the choice is all yours.