The Active Denial System directs millimeter radio frequencies at a target and causes an intense burning sensation.

Photo courtesy U.S. Department of Defense

Nonlethal and Personal Laser Weapons

Now we know that high-energy lasers are used to shoot down missiles, but do they have nonlethal uses, too? Yes. In fact, one such system has been tested and will soon be operational. It's called the Active Denial System (ADS). The ADS isn't a laser, but a truck-mounted high-energy radio frequency generator and directional antenna. A generator inside creates a 95 GHz millimeter wave. (Millimeter waves have wavelengths of 1 to 10 millimeters and frequencies of 30 to 300 GHz.) The directional antenna focuses the millimeter waves and allows the operator to point the beam. The millimeter beam penetrates the skin of anyone in its path to a depth of 1/64th of an inch, about the thickness of three sheets of paper. Like a microwave oven, the energy of the beam heats water molecules in the skin tissue and causes an intense burning sensation. The beam doesn't permanently injure because it doesn't penetrate very far, and when a person moves out of the beam, the sensation goes away (see How Military Pain Beams Will Work).

Suppose you could momentarily stun or distract an opponent. The Air Force has developed a device that will do just that -- the Personnel Halting and Stimulation Response (PHaSR). The PHaSR incorporates two low-power diode lasers, one visible and one infrared. It's about the size of a rifle and can be fired by an individual. The laser light temporarily distracts or "dazzles" the target person without blinding him.

The Department of Defense is also developing other optical distracter devices that could temporarily impair a target's vision.

You don't have to be a sci-fi fan to be wondering if there are any personal laser weapons on the market for civilians. Maybe something like those you see in science fiction shows? Can an average person purchase or build one? A company called Information Unlimited advertises a laser ray gun. After signing a hazardous equipment affidavit and purchasing the plans, you can purchase the hardware and assemble your very own laser gun.

The Personnel Halting and Stimulation Response (PHaSR) is a rifle-size laser weapon system that uses two nonlethal laser wavelengths to deter an adversary.

Photo courtesy Kirtland AFB/U.S. Air Force

Information Unlimited's laser ray gun is a solid state laser that uses a flash lamp as an energy primer and a neodinium glass rod as the lasing medium. It works much like the ruby laser described in How Lasers Work. It requires 12 volts of DC power, which comes from AA batteries. It emits infrared light of 1.06 micrometer wavelength in short 3 joule pulses for a total of 500 joules of energy. The beam is focused with a collimating lens, which straightens the beams and makes them parallel. It's classified as a hazardous class IV laser, and the company claims that it's capable of burning holes in most materials (infrared lasers can do these things). So you might not want to pick one up for your 9-year-old's birthday.

To learn more about laser weapons, take a look at the links on the next page.