Laser Pointer - Hazards - Infrared Hazards of DPSS Laser Pointers

Infrared Hazards of DPSS Laser Pointers

Lasers classified as pointers are intended to have outputs less than 5 mW total power (Class 3R). At such power levels, an IR filter for a DPSS laser may not be required as the infrared (IR) output is relatively low and the brightness of the visible wavelength of the laser will cause the eye to react (blink reflex). However, higher-powered (> 5 mW) DPSS-type laser pointers have recently become available, usually through sources that do not follow laser safety regulations for laser packaging and labeling. These higher-powered lasers are often packaged in the same pointer-style housings as regular laser pointers, and usually lack the IR filters found in professional high-powered DPSS lasers, because of costs and additional efforts needed to accommodate them.

Though the IR from a DPSS laser is less collimated, the typical neodymium-doped crystals in such lasers do produce a true IR laser beam. The eye will usually react to the higher-powered visible light; however in higher power DPSS lasers the IR laser output can be significant. What poses a special hazard for this unfiltered IR output is its presence in conjunction with laser safety goggles designed to only block the visible wavelengths of the laser. Red goggles, for example, will block most green light from entering the eyes, but will pass IR light. The reduced light behind the goggles may also cause the pupils to dilate, increasing the hazard to the invisible IR light. Dual-frequency so-called YAG laser eye-wear is significantly more expensive than single frequency laser eye-wear, and is often not supplied with unfiltered DPSS pointer style lasers, which output 1064 nm IR laser light as well. These potentially hazardous lasers produce little or no visible beam when shown through the eye-wear supplied with them, yet their IR-laser output can still be easily seen when viewed with an IR-sensitive video camera.

In addition to the safety hazards of unfiltered IR from DPSS lasers, the IR output of unfiltered lasers may also be unscrupulously included in power figures for lasers, including the ability for lasers to burn.

Though green (532 nm) lasers are most common, IR filtering problems may also exist in other DPSS lasers, such as DPSS red (671 nm), yellow (589 nm)and blue (473 nm) lasers. These DPSS laser wavelengths are usually more exotic, more expensive, and generally manufactured with higher quality components, including filters, unless they are put into laser pointer style pocket-pen packages. Most red (635 nm, 660 nm), violet (405 nm) and darker blue (445 nm) lasers are generally built using dedicated laser diodes at the output frequency, not as DPSS lasers. These diode-based visible lasers do not produce IR light.