How to Build a Laser Death Ray
Near Infrared Light
Near infrared light is one of the most desirable wavelengths to use for death rays that are to be used in an atmosphere. The air is highly transparent to near infrared in several windows between the visible edge and about 2.5 microns. The transparency of air changes in this region depending on the relative humidity and concentration of various gases such as carbon dioxide, but there are some wavelengths (such as from 0.7 to 1.2 microns) that can pretty regularly propagate through any air that is also clear to visible light. Below is a graph of typical attenuation lengths for near infrared. |
Near infrared does not go through water very well.
However, near infrared light in the most desirable wavelengths of around 1 micron will go through pretty much any material that is also transparent to visible light. You can make lenses and windows for your death ray out of normal glass or quartz, and you can shoot your death ray through windows to burn or blast targets on the other side.
The United States military is building a near infrared heat ray to shoot down missiles in boost phase. It uses a chemical oxygen iodine laser (COIL) mounted aboard a modified Boeing 747, lasing at 1.315 microns. In addition to COIL heat rays, there are a number of efficient and high power solid state lasers that emit beams in the near infrared. The popular neodymium lasers (such as Nd:YAG and Nd:glass) are currently used for machining and welding and are being developed as heat ray weapons by the military. They can also be pulsed, for use as blasters, although the technical challenges of weapons grade blasters are too high for modern technology. The most powerful laser pulses in the world are made by neodymium lasers for use in intertial confinement fusion research, and reach energies of several megajoules delivered in about a nanosecond. Neodymium lases at 1.06 microns. Titanium sapphire lasers are another mid infrared solid state laser. These are popular because the beam can be chirped, allowing chirped pulse amplification techniques to compress laser pulses down to picoscond or femptosecond durations. The Ti:Sapphire lasers commonly reach powers high enough to induce self focusing and filamentation in air. Tisapphire lasers are capable of lasing across a wide frequency band, from about 1.1 microns down to 0.8 microns. High powered free elelctron lasers are being developed that work in the near infrared, such as the FEL at Jefferson labs. These FELs are of considerable interest to the U.S. Navy as death rays deployed on ships for shooting down missiles and lightly armored aircraft.