Laser Basics
by TigerhawkT3

1. Do I need some sort of safety equipment?

1.
Q: Do I need some sort of safety equipment?
A: Yes. You should use appropriately-speced eye protection when using lasers over 5mW, of any color.

Lasers come in various colors. The most common and inexpensive color is red, with a wavelength of around 650nm. A popular, relatively new color is green, usually at 532nm. Because the human eye is more sensitive to green light than to red, a green laser will look significantly brighter than a red laser of equal power. There are also lasers of other colors, such as blue, violet, yellow, and more, but they are much rarer and more expensive. Red lasers are pretty simple and robust, but green lasers have a number of delicate internal components and are thus susceptible to damage from bumps and falls.

In the U.S., a Class II laser radiates less than 1mW (one-thousandth of one watt) of power, a Class IIIa laser radiates between 1 and 5mW of power, a Class IIIb laser radiates between 5 and 500mW of power, and anything more than 500mW is considered Class IV. The system has recently changed, with Class II now being called Class 2, Class IIIa being called Class 3R, Class IIIb being called Class 3B, and Class IV being called Class 4. More detailed class ratings and other safety information can be found at http://en.wikipedia.org/wiki/Laser_safety .

You can find lots of cheap green lasers on eBay, but as a rule of thumb, these lasers will be cheaply made, with inferior parts or dangerous attributes. One such characteristic of a common eBay laser is the lack of an infrared, or IR, filter. Simply put, most green lasers create green light by first creating infrared light, and then converting it into green. Even after this conversion, however, there can still be IR radiation in the beam, so the better lasers have an IR filter. This is what makes unfiltered eBay lasers both disappointing and dangerous: a laser can truthfully be advertised as having 100mW of output, but without an IR filter, it could be radiating only 10-15% of that as green light, with the rest leaving the unit as invisible but still hazardous IR radiation.