NextGen Lasers?

[KitKat]

I'll give you guys a crash course in laser operation here, since there seems to be some interest, but I'll try to be as clear as possible without going into a lot of optical theory about refractive index and electron energy bands.

Basically, all a lens does is change the direction of your light rays. It doesn't change the power, it only affects directionality. You can use lenses to do a lot of different things. If you want a fun way to experiment with this, I recommend the Optics Lab Ray Tracing Software. If you want a free download you might have to look around a bit.

So, let's examine the structure of the laser as outlined on their information page. The first component is a diode. Electrical energy is used to excite electrons to a high energy level and when they drop down, they emit a photon of energy corresponding to the energy gap. Judging from the 808 nm light they give, I'd bet this diode is made of GaAs (Gallium Arsenide, if you're wondering - very toxic btw) or some similar semiconductor. GaAs is a great semiconductor that is an excellent light emitter, but almost always in the infrared. When the light escaped from the diode, it is pointing every which way. The first lens is used to collect this light and make it into a coherent beam. This is then sent to a crystal.

*Terminology* You might often hear physicists talk of 'pumping' a laser. This means supplying energy to it in some form so that it can emit energy in the form of light. So when we were talking about the diode, this was pumped electrically. Crystals cannot be pumped electrically, they need to be pumped with light (photons). This way you can input light of one wavelength and have an output of a different wavelength.

So, there are a couple of crystals used in this laser, and at the end we have our green light produced. However, not all of the infrared light got absorbed along the way. A lot of it travelled right through those two crystals. The danger with infrared is that it can cause you to go blind, but you wouldn't even know it because your eyes can't see it. To get rid of this nasty infrared they have a filter that blocks all of it, but transmits the green light. By now, our nice straight light beam has gotten all messed up from going through all those materials, so another lens is used to straighten it out again.

If you check out the video on the site where it shows the laser burning paper (haha, I just spent so much time watching those videos) you'll notice that the laser is held very close to the paper. The hole it makes is the size of the laser beam at that distance from the output. At farther distances the beam spreads out a bit. Now, judging from the size of that hole, that's pretty small. Realistically, I don't think a lens will be able to focus that beam down too much more. I can't say for sure, but that's just my opinion. It looks pretty close to the minimum spot size.

[Board of Command]

Green light? Why not blue light or is that a little too close to UV for comfort?

[KitKat]

Well, blue light is quite possible although you'd have to use different crystals to produce it. The problem with blue light is actually with our eyes. We see green light the best, because it's right in the middle of our visible range. Blue light is rather near the edge. For a blue laser and a green laser of the same power and intensity, we will percieve the green one to be 3 times brighter (I think 3, but it might be as high as 10....I can't remember the actual value, so don't quote me on this). So to have an equivalently 'bright' laser, you need to use three times the power. This may be one reason why they don't offer blue lasers on their site.

Probably the biggest reason though is cost. The crystals you need to create blue light are super expensive. Check out this site which gives an estimate for blue laser pointers at $2000 minimum cost.

[ChaosK]

green because green is in the middle of our eye's visible color spectrum, where as blue is close to the end.

but now i ask, why red? though red is a big part of the color spectrum, its still at the edge, so why make red?

[KitKat]

That's a good question with a relatively simple answer. Yes, red is on the other end of the spectrum, but you can still see red better than blue. Also, red lasers happen to be extremely cheap and easy to make. That's why you can get red laser pointers at the dollar store these days. Remember all the crystals we had to deal with in the green laser? You can actually produce visible red light directly from a diode, so you can bypass all of those other steps. These lasers are made to be quite low power, usually only a few milliwatts so that anyone can use them and they can be sold anywhere. This has led to red lasers being extremely cheap and available.

[ChaosK]

oh, well okay that solves that. and of course nobody wants to see orange or yellow lasers flying around... i want the phoenix!

[Board of Command]

So green being near the middle of the spectrum makes it the most visible color. Well that answers a lot of my life's questions...

[kaosoner]

that shit is awesome!!!!! half of the ppl here said that kids dont need these right?... HOW ARE THEY GOING TO GET THEM WHEN THEY COST 200.00 U.S DOLLARS...... so we dont have to worry about dumbshit kids shootin us in the eye...unless your like my brother who likes beat the hell out of ppl anyway he can......but anyway ...who wants to point at a star in space (excluding astronomy ppl)......i want to test one of these, but i dont gots 200.00 dollars.....and that means it will replace my lighters and matches if i manage to get one.

[Assertn]

Originally posted by: BOARD_of_command
So green being near the middle of the spectrum makes it the most visible color. Well that answers a lot of my life's questions...

Is that what it said? Considering how small the range of visible light occupies with respect to the spectrum, I'd imagine that a shift from one color to the next would be very minute.

[Kraco]

Originally posted by: AssertnFailure
Is that what it said? Considering how small the range of visible light occupies with respect to the spectrum, I'd imagine that a shift from one color to the next would be very minute.

Colour vision is a bit complicated issue. And if you watch the laser in the dark, you have to add the effect of the night vision. If you have a look at this picture (I don't want to leech it, so click the link), you will notice two things: The colour we perceive as pure red has a disadvantage of being somewhat far from the absorption maximums of the different types of cone cells we have (used to perceive coloured light). And it's also easy to see why green is seen so strongly, like KitKat said. It's not only absorbed by the green cone cells, but by the red as well, and strongly, generating a high signal.

The picture also shows the absorption spectrum of the rod cells, used solely in night vision, and as you can see, it doesn't really absorb red that well. However, it's right there for green light. Well, of course this also explains why red light doesn't impair your night vision...

[KitKat]

Assertn, you're absolutely right that visible light is only a miniscule portion of the electromagnetic spectrum, but as Kraco so nicely demonstrated above, our perception of visible light depends on how well our eyes absorb it. Green just happens to be in the middle of the portion that is visible to us, and we can distinguish many subtle colour variations that represent small wavelength changes.

[ChaosK]

Originally posted by: KitKat
Assertn, you're absolutely right that visible light is only a miniscule portion of the electromagnetic spectrum, but as Kraco so nicely demonstrated above, our perception of visible light depends on how well our eyes absorb it. Green just happens to be in the middle of the portion that is visible to us, and we can distinguish many subtle colour variations that represent small wavelength changes.

jesus i feel like i'm in 8th grade again.

[KitKat]

Originally posted by: Chaoskiddo
jesus i feel like i'm in 8th grade again.

Don't disrespect optics! Or else you shall incur the wrath of KitKat and her arsenal of nuclear-powered quantum laser blasters!!! [img]i/expressions/face-icon-small-frown.gif[/img]

[Board of Command]

Yes the visible spectrum is only a few percent of the entire electromagnetic spectrum, but since our eyes are only able to perceive the visible spectrum, that is the entire spectrum to our eyes. Although going from green to red on the electromagnetic spectrum is an omissible change, it makes a whole world of difference on the visible spectrum.

[ChaosK]

Originally posted by: KitKat

Originally posted by: Chaoskiddo
jesus i feel like i'm in 8th grade again.

Don't disrespect optics! Or else you shall incur the wrath of KitKat and her arsenal of nuclear-powered quantum laser blasters!!! [img][/img]

no i meant the talking about electromagnetic spectrum and the visible spectrum. its earth science all over.