How to Build a Laser Death Ray

Fiber Optics

In the section on lenses, you learned about refraction, and how when going from a material with a high index of refraction to a lower index of refraction the light gets bent away from the direction perpendicular to the boundary between the two materials. If the light is already travelling at a grazing angle to the boundary, it can't get bent far enough to satisfy the demands of refraction. In this case, it cannot be transmitted through that boundary at all - all of the light gets reflected back into the original material. This is called total internal reflection.

This phenomenon can be used to direct light in arbitrary directions. Make a fiber core, and put a cladding around the core made of a material with a higher index of refraction. Light which is traveling in the direction the fiber is going hits the interface between the core and cladding at a grazing angle, and is reflected back into the core.

Since fibers can be bent and twisted, the light follows the bends and twists and shines out the far end of the fiber. If you use fibers to direct your death ray, you will probably want to use additional optics at the ends of the fibers to collect and collimate the beam, so that the beam doesn't end up shining out in all directions and rapidly attenuating away once it elaves the fiber.

Back to main death ray page