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Different laser types, green, red, and blue?
All i know about these different lasers is that the green one has doubling crystals and blue one has better doubling crystals. I want a laser that goes very far, but it not harmful. i know green one and blue ones can cut, but can i find a green one that is not destructive or a red one that goes far and is not destructive. in other words what lasers are harmful and cut?
You're right that most green lasers (532 nm) are frequency doubled YAG beams (from the fundamental wavelnegth of YAG @ 1064 nm), but you're mistaken about blue lasers. UV output (what you are calling 'blue') can be generated by third harmonic generation processes which are more like sum-frequency difference generation than actual 'tripling'. The UV @ 355nm is actually a mixture of IR and green outputs, and requires a different crystal after the 2nd harmonic crystal that produces the green, together with the IR the 2 wavelnegth combine in a sort of complex way to generate UV. Blue light can be generated directly in the 400~nm range (which is actually visible blue, not really yet UV) from laser diodes, but the powers are pretty small.
Several factors determine the 'class' of a laser, which is a catergorization of it's danger (class I, II, IIIa, IIIb, and c - from most to least dangerous). Main factors are wavelength and peak power, but also considered are pulsewidth and spot size of the beam. The same energy for different spot sizes will vary energy density on a target (like human flesh or the eye or a piece of steel), so smaller beam sizes may have higher energy densities and be more harmful than larger beams where the energy is spread out over a larger area - like the difference between sitting one's butt on a single nail vs. lying flat on a whole bed of nails - the impact is distributed evenly over the surface of the beam (for some beams). Now, another factor that can determine the danger of a laser is it's pulse shape - is it a Guassian beam (with a peak power in the center) or is it a flat top beam (with equal power levels at each point in the beams 2D cross-section).
UV beams tend to absorb more easily by human skin and tissue, and will hurt more if you get zapped by them. Visible lasers can usually only hurt the eye, but can be damaging so be careful. Always wear safety goggles rated at the optical density of the laser you are using (according to the factors I've mentioned - primarily wavelength and power and spot size).
Later,
johnrainwater@yahoo.com
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