Optical modulators using semiconductor nano-structures: Difference between revisions

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== Optical modulators using semiconductor nano-structures ==

An [[optical modulator]] is an optical device which is used to modulate a beam of light with a perturbation device. It is a kind of transmitter to convert information to optical binary signal through [[optical fiber]] ([[optical waveguide]]) or transmission medium of optical frequency in fiber optic communication. There are several methods to manipulate this device depending on the parameter of a light beam like [[amplitude modulator]] (majority), [[phase modulator]], polarization modulator etc.

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An electro-optic modulator is a device which can be used for controlling the power, phase or polarization of a laser beam with an electrical control signal. It typically contains one or two [[Pockels cell]]s, and possibly additional optical elements such as polarizers. The principle of operation is based on the linear [[electro-optic effect]] (the [[Pockels effect]], the modification of the [[refractive index]] of a nonlinear crystal by an electric field in proportion to the field strength).

The crystal which is covered by electrode may be considered to be a voltage-variable wave-plate. When a voltage is applied, the retardation of laser polarization of the light would be changed while a beam passes through an ADP crystal. This variation in polarization results in intensity modulation downstream from the output polarizer. The output polarizer converts the phase shift into an [[amplitude modulation]].

Micrometre-scale silicon electro-optic modulator<ref>Nature 435, 325–327 (19 May 2005)</ref>