Infrared and visible light waves, like radio waves, propagate from a source that generates an alternating electric current. However, the mechanism of propagation and the structures used to transmit these waves differ from traditional antennas used for radio waves.
In the case of infrared and visible light waves, the primary method of propagation is through optical fibers or through free space. Here are the two main scenarios:
Optical Fiber Transmission: Optical fibers are used to transmit infrared and visible light signals over long distances, similar to how electrical cables are used for transmitting electricity. Optical fibers are made of a transparent material, typically glass or plastic, with the ability to guide light through total internal reflection. They consist of a core surrounded by a cladding layer. Infrared or visible light signals, usually generated by lasers or LEDs, are coupled into one end of the fiber and guided along the length of the fiber by repeatedly reflecting off the internal walls of the core. This enables the transmission of information encoded in light signals over long distances with minimal loss.
Free Space Transmission: In the case of free space transmission, infrared or visible light waves can be emitted directly into the air or vacuum and travel without the need for a physical medium like an optical fiber. Light sources such as incandescent bulbs, fluorescent lamps, LEDs, lasers, or natural sources like the Sun emit infrared or visible light waves in various directions. These waves then propagate in straight lines until they encounter an obstacle or are absorbed by a material.
While there is no traditional antenna structure analogous to those used for radio waves, specific devices can be used to enhance and direct the transmission of infrared or visible light waves. For example:
LEDs (Light Emitting Diodes): LEDs are semiconductor devices that emit light when an electric current is applied. They are commonly used in applications such as lighting, displays, and optical communication.
Laser Diodes: Laser diodes emit a coherent and focused beam of light. They are widely used in various fields, including telecommunications, barcode readers, laser pointers, and medical equipment.
Optical Reflectors and Lenses: These components can shape and manipulate the path of infrared or visible light waves, redirecting or focusing them to achieve specific objectives, such as increasing the range or intensity of the light signal.
In summary, while there isn't an antenna structure directly analogous to radio wave transmission, infrared and visible light waves can be propagated through optical fibers or free space, utilizing light sources, such as LEDs or lasers, and various optical components to enhance and control the transmission of light.