DIY Laser Safety: How to Test Pointers and Save Your Eyes

In the last 20 years, green lasers have shrunk from table-size lab equipment to pocket-portable presentation tools. A new study from the National Institute of Standards and Technology reports that some cheap laser pointers can emit more than 10 times as much invisible infrared light as bright green light, making them more likely to blind kids and pets. The trick is to convert two photons of long-wavelength, low-energy infrared light into one photon of short-wavelength, high-energy green light in a process called frequency doubling. First, two AAA batteries fuel a diode laser -- similar to a standard red laser pointer -- which emits infrared light at a wavelength of 808 nanometers. The standard green laser pointer also includes a shield to keep any of the infrared light from escaping.