Does the color of the laser make any difference?

Hi arduino Forum

I wanted to know if the color of a laser pointer has anything to do with how strong it is ( mW, W, MW, dont know strong lasers can be ). Many people say that red lasers are the weakest and blue or green ones the strongest. But I have already seen green ones with 5mW and red ones with 250mW. And what about purple an Infra red lasers? I think the element to color them is called Yttrium so does maybe have effect on the wavelenght?

The colour of a laser is not directly related to the power.

However, given lasers of the same optical output power, the more towards the blue end of the spectrum you are the more energy each photon carries.

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

Red = long wavelength = lower energy photons Blue = shirt wavelength = higher energy photons.

For lasers individual photon energy is less relevant as the beam consists of groups of photons where each photon is in an identical quantum state - sort of like a mega-photon with corresponding higher electric field strength - this is why laser pulses can rip molecules and atoms apart in a way normal light cannot I think. For a given number of photons the blue end of the spectrum is higher energy.

Individual ultra-violet photos have sufficient energy to ionise atoms and molecules for instance.

Grumpy_Mike: The colour of a laser is not directly related to the power.

However, given lasers of the same optical output power, the more towards the red end of the spectrum you are the more energy each photon carries.

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

I think it's the other way round. Higher frequency (shorter wavelength) photons carry more energy. Ultraviolet are much higher energy than infrared. That's why IR can make things vibrate and get warm, but UV can break bonds in organic molecules.

EDIT: For the OP, at this point we're talking energy and not power. As far as power is concerned, Mike's first statement is right on. Power isn't related to color. But getting the same power at a bluer color takes more energy.

There is one more consideration not mentioned here. UV and IR lasers are dangerous because they are invisible... But a 10 mW blue Laser can and will Permanently damage the Retina in the eye, If directed at the Eye, green isn't quite so bad butt great damage can be done quickly. On a regular basis I see both Green and Blue lasers > 20 mW for sale on Ebay for about $10.00 to $15.00. Spare eyeballs are (Working ones) Pure Unobtanium for ANY money. So I don't play with lasers, Period. I don't like to make things that have any possibility of causing unintended damage to anything, Period.

Doc

green isn't quite so bad butt great damage can be done quickly

So never shine a green laser on your butt. :)

Absolutely... because you migght need a mirror and that is a good wa7y to miss...

Doc Thank you, I was in a hurry and forgot to re-read before I hit the post button, I'm Not a touch typist...

Docedison: So I don't play with lasers, Period. I don't like to make things that have any possibility of causing unintended damage to anything, Period.

Well - that just basically comes down to knowing laser safety, just like any other pursuit with any level of "danger"; in the case of lasers, any time you are going over about 5 mW, or dealing with IR (no blink response), you should wear proper laser safety glasses/goggles for the wavelength of the laser being used. Such goggles are fairly easily available (though the quality ones can be rather pricey).

Red = long wavelength = lower energy photons Blue = shirt wavelength = higher energy photons.

What if I have a red shirt?

Your wavelength is only dependent on your mass at rest and your velocity, there's no variable for object/shirt color in de Broglies ? = h/mv

I would not advise wearing a red shirt while working with lasers - I've seen enough star trek to know how that works out. ;)

Seriously though, I think there's a bit of irrational fear about lasers on many forums. Same as HV projects. IF you are aware of the risks, and IF you wear the right protective gear and use your common sense, then there's no reason not to have a go.

I have no need to play with lasers (yet) as I haven't thought of a project I want to work on that requires them. But if I was going to, I would definitely make sure I had some protective goggles intended for the laser wavelength I was working with, and I would probably run any experiments remotely and observe the results indirectly, perhaps from outside the room on a monitor. I would think with those safety measures in place even an amateur would have a hard time causing themselves serious injury.

In testing terms, I had a similiar 5mw red and 5mw blue llaser the blue one would actually warm my upper lip just noticeably (most temperture sensitive area on the body) while the red would not

winner10920: In testing terms, I had a similiar 5mw red and 5mw blue llaser the blue one would actually warm my upper lip just noticeably (most temperture sensitive area on the body) while the red would not

I think this might have more to do with absorbance spectra of different molecules in your lip than it does with the actual power of the laser.

What color are your lips? Hopefully they are absorbing more blue light and reflecting more red. If not, you need to put the lasers down and take a breath.

Lol I meant the regular skin part just above the lip, which I imagine would still absorb blue and reflect red more, I wonder if that is really why tho

Someone else posted the clue.. .

Red = long wavelength = [u]lower energy photons[/u] Blue = shirt wavelength = [u]higher energy photons[/u].

For this quote...

In testing terms, I had a similiar 5mw red and 5mw blue llaser the blue one would actually warm my upper lip just noticeably (most temperture sensitive area on the body) while the red would not

Doc

But do you think it was the energy difference or the absorption difference that made one noticable?

http://www.ebay.com/itm/170881810414

A 10mw 405nm (near UV) laser module. For four bucks I couldn't pass it up. I expect it to be amusing to use it to fluoresce various items and other oddball fun.... Interesting things happen :D

otzi: Hi arduino Forum

I wanted to know if the color of a laser pointer has anything to do with how strong it is ( mW, W, MW, dont know strong lasers can be ).

What do you mean by strong? The "brightness"?. 1 mW is 1 mW but a 1mW green laser appears brighter to people than 1mW in blue or red because the human retina is more sensitive to green light.

At moderate to bright light levels where the cones function, the eye is more sensitive to yellowish-green light than other colors because this stimulates the two most common (M and L) of the three kinds of cones almost equally. At lower light levels, where only the rod cells function, the sensitivity is greatest at a blueish-green wavelength.

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

Is there a certain point where red Lasers can not get stronger (mesuared in mW) but blue Lasers can put out more mW. Is there like a rank order ? Bsp: 5. IR Laser 4. purple Laser 3. green Laser 2. blue Laser 1. UV Laser

I dont mean the brightness because you can see IR and they still put out mW.

anyway Thx for all your replies. XD

Is there a certain point where red Lasers can not get stronger

No.