How to Build a Laser Death Ray


Windows are barriers that block matter but let light through. This can be useful to let your death ray out into the world without letting the nasty elements of the environment back into the innards of your death ray.

Windows need to be made from a material that is transparent to the light emitted by your death ray. Glass works well for near infrared and visible light. As you go farther into the ultraviolet you need to use particular kinds of crystals, such as sapphire or fused quartz. In the mid and far infrared glass is also opaque, zinc selenide or barium fluoride can be used for windows at these wavelengths.

In the vacuum ultraviolet and shorter wavelengths, no matter is transparent and you can't use windows of solid material. One option is to use a plasma window. A very hot and low density plasma is confined by a magnetic field. Air cannot pass through the plasma, and the plasma cannot leak out of the field. This effectively separates outside air from the inside, allowing, for example, a vacuum inside. Electromagnetic radiation can pass through the plasma and into the air.

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