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Q & A: Laser Colors

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Most recent answer: 10/22/2007
Q:
What are the differences between green and red laser? Why is green more expensive than red?
- michel vieira (age 18)
chelsea MA USA
A:
The difference between a red laser and a green laser light is that the red laser light has a longer wavelength (about 650 nanometers) than does the green (about 532 nanometers).

The mechanism behind making them is also different. Red lasers use a diode, optics, and some electronics. These are fairly easy to make and assemble, so red lasers are cheap.

The green laser, on the other hand, requires a special diode (an 808 diode for those who know their lasers), a second infrared laser crystal, and a frequency-doubling crystal. These have to be very carefully aligned in order for the laser to function properly. Because it takes lots of work to make a green laser, and because there is not much demand for green lasers, their cost is much higher right now than for a red laser. (For a more complete description, see http://en.wikipedia.org/wiki/Laser_pointer.)

Having different colors of laser light is neat because they have different properties. The small hand-held green lasers tend to look much brighter than similar red lasers . Also, green light bends more than red when it enters a glass lens, for most typical glasses.


If you are interested in looking at some specifications for different kinds of lasers and their uses, you can check out http://www.lasermate.com/

I hope this answers your question.

dk (minor modifications by mike w)

(published on 10/22/2007)

Follow-Up #1: Speed of colored light

Q:
do the different colors of lasers affect the velocity of the laser light?
- Omer (age 22)
Columbus, Oh, USA
A:
No, the speed of light in a vacuum doesn't depend on the color (i.e. the wavelength or the frequency). The different colors will travel at slightly different speeds through materials such as glass.
Mike W.

(published on 10/22/2007)

Follow-Up #2: different lasers

Q:
but is the red any hotter or what and blue and yellow. is it just the colour that makes some more expensive then others.
- Sam
Ireland
A:
The light doesn't really have a temperature. The price of a laser depends not only on what color light it puts out but also how it generates it. For example, many old red lasers used tubes of mixed helium and neon gas. Those were moderately expensive to build. The high-power versions had big gas tubes and were quite expensive. Now you can get low-power red lasers (almost the same wavelength of red) using just solid-state diodes, much cheaper to build. Likewise green lasers can be built with argon gas tubes, or with solid-state diodes. The price is very different depending on the type and the power. Also, some lasers have polarized outputs and other are unpolarized, etc., and the price depends a bit on those features too.

Mike W.

(published on 05/16/2013)

Follow-Up #3: Watts, color, and heating

Q:
I was curious as to the difference in power between the colors, and if there is a limit to that power depending on each color. I have watched lasers melt through things, depending on wattage and nanometers, and was wondering about the relation of colors to wattage and nanometers, if there was any at all. Mostly I just want to know if a blue laser would be more effective at melting stuff than a green or red would be, or if it's completely unrelated.
- Dave (age 22)
Ames IA US
A:
It's the Watts that count, not the color.  There is, however, a relationship between the energy of a single photon of a certain color, E = hf where h is Plank's constant and f is the frequency of the photon.  So in that sense it takes fewer photons per second to make up one Watt for higher frequency (shorter wavelength) light.   However, the power specification takes that fact into account making the color irrelevant. 

LeeH

(published on 09/03/2009)

Follow-Up #4: powerful light sources

Q:
I don't want to make a laser, but a light with high energy output, while comsuming the least possible energy. I am thinking of using Fiber optics, and some sort of lighting source. I read in the last answer that it is the wattage, not the color, of a laser that makes it stronger, but what about regular light? I need strong light, and am wondering how to increase the frequency of the light I will be putting out.
- jack warren (age 19)
Powell,WY,US
A:
The key stage in making a lot of light with little power input is the device that generates the light. In any such device, only a fraction of the power comes out as light. LED's are probably the most efficient type of device you can easily get. (see http://en.wikipedia.org/wiki/Light-emitting_diode) I'm not sure why you want to increase the "frequency". Is that really what you mean? You can get blue LEDs, but it's easier and cheaper to get the lower-frequency (red) ones.

You can then use mirrors, lenses, and fiber optics to direct the light with fairly small losses.

Mike W.

(published on 09/21/2011)

Follow-Up #5: blue and yellow lasers

Q:
can we obtain different colors in laser like blue ,yellow other than red and green, is it so what will be the process.
- fathima (age 22)
dindigul
A:
You can purchase blue or yellow diode lasers, easily found by a Web search. They are typically made with solid-state diodes. Argon ion lasers also have  a bluish (488 nm) line. There may be others too.

Mike W.

(published on 02/28/2013)

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