Laser pointers have been around since visible red laser diodes have been on the market which means they’re older than most of the teenagers who buy them. Laser pointers are typically made from direct laser diodes or diode pumped solid state ( DPSS ) lasers. Direct diode pointers are available in red or violet (made from Blu-Ray lasers at 405 nm WL “nanometers wavelength”) and direct diode green will likely soon be available thanks to a company called KAAI who developed them for the laser projector market.
Red laser pointers are available in a variety of wavelengths such as 635 nm, 650 nm, 660nm, 670 nm.
DPSS laser pointers are typically available at the following wavelengths, (blue) at 473 nm, (green) at 532 nm and (yellow) at 589 nm and (orange) at 593 nm. Since the human eye is most sensitive to the color green with a peak apparent brightness at 555 nm this means all other visible colors appear less bright despite the same power level. The difference in apparent color brightness is basically expressed in this ratio with green at 514 nm being (1) then blue at 488 nm being (2.6 times less than green) and red at 647 nm being (4.6 times less than green). The previous ratios and wavelengths can all be found in an Ion mixed gas Argon/Krypton, white light laser used by professional laser show companies. The color brightness ratios will vary according to the wavelengths but the above ratios provided would give you proper white light color balance. To sum it up a 1 watt green laser at 514 nm appears to be as bright as a 2.6 watt blue laser at 488 nm and as bright as a 4.6 watt red laser at 647 nm. You would have to consult a color chart to compare apparent brightness of other laser wavelengths.
A few things to consider If you want to buy a DPSS laser pointer is the power level and the way the diodes are operated. What I mean about power levels, is the actual power level measured at the operating wavelength. Since a typical green DPSS laser pointer has several laser wavelengths involved to generate a frequency doubled visible output, unless the manufacturer provides good filtering, the power you measure at 532 nm might also be from the other 2 IR laser wavelengths. You can actually get cheap laser pointers that output infra-red light (808 nm and 1064 nm) almost as high as visible light, which can be very dangerous and deceiving to someone who thinks they bought a paper burning power house. The other thing about DPSS laser pointers is the way the pump diodes are operated, which can be pulsed (turned on and off at a fixed frequency) or CW constant wave (on constantly). It’s very easy to determine If you bought a pulsed DPSS laser pointer as you will see a chopped up line if you move the beam quickly across the wall or ceiling.
The last concern with laser pointers is the biggest, which is safety due to the ever increasing power output available today. Typically laser pointers are limited to 5 milliwatts but there are manufacturers that seem to cater to clients who want more power like Wicked Laser in China who provide pointers which are more like flashlights, outputting power levels as high as 500 milliwatts in green or red. It also doesn’t take a rocket scientist to buy a raw laser diode and driver to make their own higher than legal laser pointer.
To provide a perspective on power levels, a 5 milliwatt green laser at 532 nm would be enough to dazzle your night adjusted vision and possibly cause an automotive accident at say a hundred feet from the source. In contrast a 500 milliwatt green laser could easily cause permanently damage to your vision, start fires by burning paper or other combustible materials at short range and definitely distract an airline pilot approaching a runway at a distance of a mile or two. Safety is everything when it comes to laser pointers.
Since laser applications are so widespread, we cannot outlaw them but rather try to apply better controls over their use and distribution. Lasers are strictly controlled by the Food and Drug Administration, FDA in the United States and other governing bodies associated with countries that manufacture and sell them.
To be sure, lasers were inspired by science fiction and laser pointers attract not only Trekkies and Star Wars fans but people from all walks of life. Be it over zealous sports fans wanting to affect the outcome of a home game or granny getting her exercise and cheap entertainment while playing follow the red dot with her 10 cats, lasers are everywhere.
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