Optical modulators using semiconductor nano-structures: Difference between revisions

Revision as of 21:05, 6 July 2009

Revision as of 21:06, 6 July 2009

Line 2:

== Optical modulators using semiconductor nano-structures ==

An [[optical modulator]] is a 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 methodmethods to manipulate this device depending on the parameter of a light beam like [[amplitude modulator]] (majority), [[phase modulator]], polarization modulator etc.

The easiest way to obtain modulation is modulation of intensity of a light by the current driving the light source ([[laser diode]]). This sort of modulation is called direct modulation, as opposed to the external modulation performed by a light modulator. For this reason, light modulators are called external light modulators.

According to manipulation of the properties of material modulators are divided into two groups, absorptive modulators ([[absorption coefficient]]) and refractive modulators ([[refractive index]] of the material). [[Absorption coefficient]] can be manipulated by Franz-Keldysh effect, Quantum-Confined [[Stark Effect]], excitonic absorption, or changes of free carrier concentration. Usually, if several such effects appear together, the modulator is called electro-absorptive modulator. Refractive modulators most often make use of [[electro-optic effect]] (amplitude & phase modulation), other modulators are made with [[acousto-optic effect]], [[magneto-optic effect]] such as Faraday and Cotton-Mouton effects. The other case of modulators is [[spatial light modulator]] (SLM) which is modified two dimensional distribution of amplitude & phase of an optical wave.