MadSci Network: Physics

Re: How are lasers likely to change in the future?

Date: Wed May 30 13:13:45 2001
Posted By: Karl Kolbus, Staff, Data processing, Mequon Consulting Corp.
Area of science: Physics
ID: 991075658.Ph

Hi Alex!

To answer your question, I must say that the future is NOW! Many things 
have been affected, mostly in a positive way, by use of the laser. 

To fully understand the impact the laser has on society in general, we 
must first understand what a laser is and what it can (and can't) do. The 
term LASER stands for Light Amplified by Stimulated Emission of Radiation. 
To understand this concept, let's look at a "Neon" sign. It is nothing 
more than a glass tube that contains the gas Neon (chemical symbol Ne). 
Neon gas, when energized (excited) by a high voltage, causes the gas to 
glow. This glow is produced because the high voltage raises the energy 
charge on the Neon molecules to a higher level, called the E3 level. Not 
all of the molecules of Neon can remain at this level; some drop back down 
to level 1, (E1) the starting point, and others drop back to level 2 (E2). 
When molecules drop back to the E2 level, they emit a 'packet of light' 
called a photon. Because this photon vibrates back and forth at a 
particular rate ( much like the ripples in a pond when you throw a stone 
into it), your eye sees these ripples as the color orange. Other 
gasses 'ripple' at a different rate, and our eye sees them as different 
colors. Argon (Ar) will look purple, Sodium (Na) will look yellow, etc. 
Now let's compare this to a regular lightbulb. They contain a filament 
that heats up when electricity is passed through it. This heat causes 
electrons to become excited and make photons, creating light. Like 
the Neon tube, the light coming from a regular lightbulb goes off in many 
different directions. That is why a single lightbulb or Neon sign can 
illuminate a whole room.

Here is where the laser is different. Like the Neon tube, a laser tube is 
straight and contains one or more gasses. It could be Neon, Argon, 
Krypton, Helium, or others. At one end of the tube there is a curved 
mirror that reflects nearly all of the photons. At the other end is a flat 
mirror that reflects about 95 percent of the photons; in other words, it 
is partially transparent. When the electricity is turned on, some of the 
molecules of the gas are raised to the E3 level. Some fall back to E1 
immediately; others fall back to E2 and emit a photon in the process. This 
photon is reflected by the walls of the tube and the mirrors at both 
ends. A single photon will probably not pass through the 
partially transparent flat mirror at the output end, so it bounces back 
and forth between the two mirrors. When it does so, it may hit another 
excited molecule causing it to drop to the E2 level, causing it to emit another 
photon. Now we have 2 photons bouncing back and forth. This process 
continues and eventually we have enough photons that it is very probable
for some of them to exit the flat mirror, creating a pulse of light.
The thing that makes a laser special is that because the photons bounce
back and forth along the length of the tube, and the photons were
"stimulated" by other photons, the photons in a given pulse are
all in phase, and the light coming out of the end travels in a 
straight line. This is called coherent light. Unlike the regular lightbulb 
which spews light in every direction, the laser produces a very thin, 
straight line of light. Unless you are looking directly into the end of 
YOURSELF!!), you would see nothing. This beam of 'light' (I'll explain why 
I put the word 'light' in quotes later), is usually no more than 1-2 cm. 
in diameter, and can be thinner than a human hair! 

So, now that you know what it is, how do you use it? Many ways!

COMMUNICATIONS: Like your voice travelling through a telephone wire, a 
laser beam can carry your voice and data and pictures through a fibre 
optic strand; a very thin glass fibre. A
single fibre optic cable can carry many thousands of telephone calls at 
the same time and at very high speed. Because it is light that is being 
transmitted, it is immune to interference that would otherwise make your 
voice sound scratchy or staticy. The music and videos you watch on CD's 
were created by lasers burning small pits into the surface of a thin metal 
foil imbedded within the CD. Because the pits it creates are so small, a 
CD can hold vast amounts of music or data (or movies). A laser in your CD 
player 'reads' these pits by shining a laser beam onto the CD and detects 
the reflection changes caused by the pits, and converts them back into 
music, or whatever.

BUILDING AND ARCHITECTURE: One major part of putting up a building is 
being able to make a wall straight. I mean, how would it look if all our 
skyscrapers looked like the Leaning Tower of Pisa?? In the not to distant 
past, one person would have to look through a telescope-like device at one 
point and signal to a person at another point to raise or lower the marker 
on a stick to 'draw' a level line. Now a laser beam is aimed at the stick, 
and the point of light hitting it is easily seen by the other person. 
Besides being easier and quicker, it is far more accurate. If the stick at 
the far end has a retro-reflector mounted on it (a retro-reflector is a 
special mirror that will reflect light directly back to its source), the 
time it takes from the sending of the laser beam until it returns can be 
measured, and this tells you the exact distance between the two points. 
Try that with a flashlight!

MEDICINE AND MANUFACTURING: I'm grouping these together because they use 
special types of laser 'light'. Here's why I put 'light' in quotes before: 
Light, as we normally think about it, is something we can see with the 
human eye. There are other types of light that we cannot see, like 
infrared and ultraviolet light. Some insects, like moths, CAN see 
ultraviolet light, while we can feel infrared light as heat. Surgeons use 
invisible lasers to perform surgery on the body and the eyes. Like a 
scalpel, the laser can burn an incision into the body, and burn away 
tumors. But, unlike a scalpel, the heat of the laser beam can immediately 
seal any blood vessels, leaving the operating area relatively free of 
blood and sterilizing the area at the same time, thus reducing the chance 
of infection. The laser is especially useful in eye surgery because the 
beam can be focused on the exact desired spot within the eye without 
affecting the surrounding area. At this point you may ask "If the beam is 
invisible, how do you aim it?" Simple. You use two lasers, one which is 
visible, for aiming the one which is not. You first position the fibre 
optic probe using the visible laser then, without changing the position of 
the probe, you switch to the invisible laser and perform your surgery. In 
manufacturing, very high power carbon dioxide (CO2) or Ytterbium Gallium 
Arsenide (YAG) lasers are used to very accurately cut metal, drill tiny 
holes, weld parts together, trim microscopic-sized electronic components, 
measure and align parts, and many other chores that require extreme 
LAW ENFORCEMENT AND SECURITY: Lasers are replacing radar in catching 
speeders, they are used to read, catalog, and identify fingerprints, and 
are used to set up security perimeters. A single laser beam can secure a 
whole house. Remember that a laser beam can be reflected by a mirror? If 
you set up a laser to point at a mirror across a room, and that mirror 
reflects the beam to another mirror somewhere else in the room, and so on 
until the last mirror reflects the beam to a receiver, then, if someone 
steps through the beam, the receiver does not receive the beam and an 
alarm goes off. You could literally cover your house (or any other 
structure) with a virtual spiderweb of laser light!

MILITARY: Without going into the morality of the matter, many present-day 
weapons use lasers to guide them to their target. Bombs can detect the 
laser beam reflected by a target, lock onto it, and adjust its course to 
make an almost direct hit. The laser illuminates the target by either 
someone on the ground or by another aircraft. The same technology is used 
when firing rockets against tanks and other mobilized vehicles. Soldiers 
can use laser illuminators to 'light up' their target at night and use 
special glasses to see this invisible light. The so-called "Star Wars" 
program was designed to put extremely high-power lasers into orbit around 
our planet to shoot down enemy missles.

POWER GENERATION: Currently still in the experimental stage, high-power 
lasers (many of them) are focused on a Hydrogen (H) pellet. With enough 
power (heat), the hydrogen will fuse to become Helium (He) and release a 
tremendous amount of power. So far, scientists have achieved fusion, as it 
is called, but the energy required exceeds the amount of energy released. 
Someday, perhaps soon, they will succeed and we will have an almost 
unlimited supply of energy. Even though the Lithosphere (Earth's crust) is 
only made up of 0.127 percent Hydrogen, we have LOTS of water (H2O) which 
could be electrolyzed into its components of 2 parts Hydrogen and 1 part 
Oxygen (O). As Albert Einstein once said, "If all the energy contained in 
the head of one matchstick could be released, we would have enough energy 
to supply all the earth for 100 years". Of course, that was many years 
ago. Now, it might take 2 matchsticks! 

These are just a few of the current uses of lasers; others are sure to 
quickly follow. One possibilty I forsee for the betterment of all mankind 
is the use of the MASER. A maser is like a laser but, instead of working 
with visible light, it works with microwaves. Microwaves are also "light"
but are at frequencies invisible to our eyes.  A large solar collector would be 
placed in orbit around our planet. This collector would gather the Sun's 
energy and power the maser, creating vast amounts of microwave power. This 
power would then be aimed at a receiver on Earth and converted to 
electricity, thereby eliminating or reducing our reliance on fossil fuels. 
The reason for using a maser is that the transmission of microwave power 
is not affected by our atmosphere nearly as much as visible light is.

Alex, the possibilities are endless. God has given you a brain that is 
more powerful than any computer that has ever been created or will be 
created. Use it to its fullest extent. Read, listen, learn, and 
experiment - then share your knowledge with others. Who knows? You could 
be the next Alex Einstein!!

Good Luck!

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