Ken Barat, CLSO (certified laser safety officer)
While a familiar fixture in the lab or workplace, the laser has taken on a different perception with the general public. For many people outside of the photonics industry, the first introduction to laser technology comes from the James Bond film “Goldfinger,” or possibly the Austin Powers parody “Goldmember” for the younger set. These exotic — and wildly exaggerated — renditions aside, the laser pointer made the technology a physical reality in the hands of the public, way before self-checkout.
The exaggerations continued with cartoons showing laser pointers used as presentation tools that burned audience members. But despite these imaginative portrayals of laser power, pointers and handhelds have become akin to the digital watch. They have gone from an expensive novelty to an inexpensive and easily obtainable item.
To be clear, common though they are, laser pointers are not injury-proof and should never deliberately be aimed at people, animals, or vehicles. The risk of injury is difficult to quantify and depends on many factors besides output power, including the laser’s divergence, distance
from the target, and steadiness. But unsafe use in any situation substantially increases the risk of injury.
On the positive side, laser pointers are incredibly useful for lectures and backyard astronomy, as a bird repellent, and even for underwater use — not as shark repellent, but for when archaeologists or scuba divers want to pinpoint items of interest. The devices have also been a boon to cat exercise regimens. (Personal testing has shown that cats will not follow a beam out a window.) Aquarium owners have also reported using the technology
to exercise their fish, though anyone trying this should watch out for back reflections.
While inexpensive red lasers are the most popular pointing tool, green lasers have grown in popularity due, in part, to the human eye’s comparative sensitivity to wavelengths in the green region of the spectrum. This means green beams appear brighter and crisper. Green lasers incorporate a wealth of technology that would have once filled an optical table. Specifically, green pointer output relies on a battery-powered diode pumping an Nd:YAG or similar crystal. The beam strikes a nonlinear crystal before passing through an infrared filter to emit a green beam. All of these components can now fit in a person’s hand.
Pointers versus handhelds
There is a distinction between laser pointers and handhelds. Per the legal definition established by the U.S. Food and Drug Administration (FDA), the continuous-wave output of a pointer cannot exceed 5 mW. And any handheld that outputs more than this limit cannot truly be called a laser pointer.
While such low output powers are reasonably eye safe at a distance, lasers can still become dangerous distractions in the wrong hands and even cause temporary flash blindness. Laser strikes on aircraft pilots have been well documented with astounding frequency: The U.S. Federal Aviation Administration reported 6136 laser incidents in 2019. Injury was avoided in most but not all cases, indicating that strikes on aircraft remain a serious threat to aviation safety. The problem has become so widespread that pilots have developed tested responses to being lased.
Pointers have also become a tool for disruption during street demonstrations in Cairo, Hong Kong, Chile, and, more recently, the U.S. Wielded by protesters, even low-power pointers can distract or temporarily flash-blind police, or temporarily or permanently disable camera sensors.
As a result, U.S. authorities have begun to provide police with helmet shields equipped with tinted strips to reduce the perceived intensity of common laser colors, such as green and blue/violet.
Additionally, the federal government and most states have passed regulatory penalties for people charged with misusing hand-held lasers and pointers, though only a small number of these cases go to court.
Periodically, pointers entering the U.S. to be sold to the public are checked by the FDA’s Center for Devices and Radiological Health (CDRH) for quality control. The most common issue, outside of inaccurate labeling of pointers with outputs over the 5-mW limit, is units missing IR filters, which prevent any IR radiation from exiting the pointer.
It is also possible to buy a correctly labeled handheld that can emit over 5 mW.
Indeed, units outputting blue, green, or red light from anywhere between 25 and
5000 mW are available for purchase on
the web at minimal cost. This puts hand-held devices in the laser categories of Class 3B (avoid eye exposure to the beam) or Class 4 (avoid exposure to eyes or skin from direct or scattered radiation) — levels that are markedly more hazardous, especially in the hands of consumers unversed in basic laser safety practices.
The laser — like its nonionizing cousin, the microwave oven — has become a cornerstone of modern life. No one is looking to ban pointers or handhelds, but users must be smart and consider how they use these marvelous tools. Those of us in the photonics community need to speak up and inform others when we observe laser misuse of any kind.