Understanding the Basics of Lasers: A Comprehensive Walkthrough

[QuantumTheory]

Greetings, my name is Kevin.

Ever wonder how a laser works? Well, this short essay here is for you then!


I will be posting several 'papers', if you will, about science to all who are interested.

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First, lasers.

Laser is actually an acronym for L.A.S.E.R, or "Light ampified by stimulated eletro-magnetic radiation."

Now, this may sound tough to swallow, but let me explain it another way:
Light is composed of several different frequences. There are very high frequences, and very low freqences. These frequences act like waves, (and particles, but more on that later) which travel over distance.

Light can also be called Eletromagnetic Radiation.

Ah ha! So that's what that means.

Like I said, light is composed out of several different frequences and wavelengths.

So when you see a rainbow, it is actually the entire spectrum of light.

A prism separates the light into its corresponding frequences and wavelengths.

At any rate, now that we know this information, we can move onto lasers.

A laser has the following properties:
1) It is coherant.
2) It it concentrated.
3) It has successive 'steps'.

Coherant means that is comprised of a single wavelength. (Instead of light that is in every spectrum, laser is only a small portion of all spectrums of light)

There are 2 or more types of lasers. 2 that I can think of right now are:
1) Semi-conductor lasers. (Uses chips to produce LED light)
2) Gas lasers. (Very strong)

Semi-conductor lasers are the pen pointer lasers, and the light is red.
Gas lasers can be powerful enough to melt though things. (Like the stuff you see in the movies!)

Part II) Componets.

We will now cover the componets of a gas laser.
It can be separated in the following parts:
1) Flourescent glass tube with tungsten filament.
2) Lasing medium filled with gas. (Fig 1.0)
__________________________
|_________________________ | <-- (This is the flourescent glass tube with tungsten filament. similar to the "Open" signs you see in restaurants.)
(Fig 1.1)
|----------------------|
| | <-- (This is called the lasing me-
|----------------------| -dium.)


And finally, this is how a basic gas laser works:

Step 1) The flourescent light goes on. The light is directed downward.

Step 2) The light stimulates the atoms in the lasing medium (and there is gas within this chamber). Each atom goes from ground state, to a higher exited energy level. Then, the atom(s) go back to their orginal ground level. In the process, they emit a photon.

Step 3) A photon is a particle of light. Together, billions of photons create the visible spectrum of light we all see today. However, the laser light that comes out is only a single part of the total spectrum of light.

Step 4) On the left side of the lasing medium, there is a reflective mirror. On the right side, there is a reflective mirror but half silvered. The photons travel to the left mirror, bounce off and go to the right, and the photons that make it out, together, make laser light that you see.



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Note: For all of you brainiacts out there, please do not humilate me. I'm 16 years old, and I just want to help spread knowledge to people who want to know more about lasers. I'm sure something similar has been constructed like this before, but I really want to help and it sums it up nicely. I am dsylexic, so if you see any errors please let me know via Private Message.

 

[chroot]

QuantumTheory,

Since you felt the need to apply a disclaimer at the bottom of your post, why did you even post it at all? It is, quite frankly, riddled with errors. You're doing the community more of a disservice than a service by writing essays full of misinformation.

Here are just a handful of your errors:

1) You didn't even get the acronym right. LASER stands for "light amplification by stimulated emission of radiation."

2) Semiconductor lasers are not all red. They do not produce "LED light."

3) You attempted to describe a specific kind of laser pump. All lasers have pumps, which are used to create the necessary energy-state population inversion. You never called it a pump, or described what it was actually doing. In fact, it seems to me that your essay completely fails to explain what makes a laser a laser.

4) You misspelled a number of words, including the word "coherent."

No offense intended, but your essays will not be welcome here until they are much better. You are young, and still have a lot to learn. Please refrain from trying to teach others until your own knowledge is more developed.

In the meantime, someone interested in lasers would be better off reading a page like this one:

http://en.wikipedia.org/wiki/Laser

- Warren

 

[Laser Jock]

chroot, I think you are being a little harsh. Yes, QT's essay is far from perfect, but his understanding of lasers is far better than I had at that age. Also, I'm not concerned at all about any misspellings in QT's post.

QT, if you’re interested, here are a few more corrections that jumped out at me.

1. Coherent does not mean that it is "comprised of a single wavelength." You can have light that is monochromatic, but is not coherent. In addition, light can be coherent, but made up of many wavelengths. Coherence means that all of the light waves that make up the light beam are in phase with each other. FYI, light can vary from incoherent to coherent continuously. However, even the best of lasers are not purely coherent.

2. You appear to be only familiar with laser pointers and (I'm guessing here) HeNe gas lasers. However, the types of lasers are far more diverse than you indicate. You can even make a laser out of Jello. Also, some of the more important lasers are pulsed and don't shine a continuous beam.

3. You sort of missed the whole stimulated part of the laser. The pump light excites (not stimulates) the atoms in the gain medium. It is the photons that are bouncing back and forth in the cavity that stimulates the atoms. It acts like a feedback process. What happens when you put a microphone next to a speaker? I tiny amount of sound (maybe static) coming from the speaker is picked up by the microphone. That sound gets amplified by the electronics and comes out of the speaker. It gets picked up again by the microphone and gets amplified again. The result: a very loud (and very annoying) screech is produced. Light coming from a laser is very much like that screech. A random photon will hit an excited atom to cause it to emit a photon. Now you have two photons instead of one. In addition, those photons are in phase (coherent). Those two photons hit two more excited atoms and now you have four coherent photons traveling together. This process (called stimulated emission) is repeated until (a) you have no more excited atoms, or (b) an equilibrium is reached between atoms going to a lower energy level and atoms being excited by the pump.

So QT, I encourage you to keep learning. You'll get it yet.

 

[Gonzolo]

I agree with chroot that such an article is not valuable to the forums.

I agree with Laser Jock that QuantumTheory is knowledgeable for his age.

Perhaps QuantumTheory could write such articles in his journal or blog, clearly mentionning his age and disclaimers on each one.