Electronics

Optical electronics involve combined applications of optical (light) signals and electronic signals. Optoelectronics have a number of uses, but the three general classifications of these uses are to detect light, to convert solar energy to electric energy, and to convert electric energy to light. Like radio waves and microwaves, light is also a form of electromagnetic radiation except that its wavelength is very short. Photodetectors allow light to irradiate a semiconductor that absorbs the light as photons and converts these to electric signals. Light meters, burglar alarms, and many industrial uses feature photodetectors.

Solar cells convert light from the sun to electric energy. They use single-crystal doped silicon to reduce internal resistance and metal contacts to convert over 14% of the solar energy that strikes their surfaces to electrical output voltage. Cheaper, polycrystalline silicon sheets and other lenses are being developed to reduce the cost and improve the effectiveness of solar cells.

Light-emitting diodes (LEDs) direct incoming voltage to gallium-arsenide semiconductors that, when agitated, emit photons of light. The wavelength of the emitted light depends on the material used to construct the semiconductor. The LED is used in many applications where illuminated displays are needed on instruments and household appliances. Liquid crystal displays (LCDs) use very low power levels to produce reflected or scattered light; they cannot be seen in the dark like LED displays because they do not produce light. Conductive patterns of electrodes overlie parallel-plate capacitors that hold large molecules of the liquid crystal material that works as the dielectric.

Like microwaves, optical electronics use waveguides to reflect, confine, and direct light. The most familiar form of optical waveguide is the optic fiber. These fine, highly specialized glass fibers are made of silica that has been doped with germanium dioxide.