Jeff Hecht, this week's guest blogger, is at the Solid State and Diode Laser Technology Review of the Directed Energy Professional Society in Newton, Massachusetts.
What does eye safety have to do with laser weapon? A lot if you're thinking seriously about actually deploying them for applications such as defense against rockets, artillery and mortars, as I describe in my feature in the July IEEE Spectrum.
Laser beams at visible or near-infrared wavelengths are hazardous because the eye focuses their parallel rays onto a tiny spot that can damage the retina, the eye's layer of light-sensing cells. The U.S. and most other countries now use lasers emitting at infrared wavelengths of 1.4 micrometers or longer in lasers that measure ranges to targets or designate targets for smart bombs because those wavelengths are blocked by the fluid inside the eyeball.
At the Directed Energy Professional Society meeting in Newton, Massachusetts on July 1, developers described strides toward high-energy versions of two types of fiber lasers with retina-safe output. The US Army Research Laboratory is developing erbium-doped fiber lasers emitting near 1.6 micrometers. Northrop Grumman is developing thulium-doped fiber lasers emitting near 2 micrometers.