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Optical modulator
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<h2 id="classification-of-optical-modulators">Classification of optical modulators</h2> <p>According to the properties of the material that are used to modulate the light beam, modulators are divided into two groups: <i>absorptive modulators</i> and <i>refractive modulators</i>. In absorptive modulators the <a href="/facts/Absorption_coefficient/ppCIsSGw">absorption coefficient</a> of the material is changed, in refractive modulators the <a href="/facts/Refractive_index/yjkzvgeE">refractive index</a> of the material is changed. </p><p>The absorption coefficient of the material in the modulator can be manipulated by the <a href="/facts/Franz%E2%80%93Keldysh_effect/HVNUpL3G">Franz–Keldysh effect</a>, the <a href="/facts/Quantum-confined_Stark_effect/PMDFSPtX">Quantum-confined Stark effect</a>, excitonic absorption, changes of Fermi level, or changes of free carrier concentration. Usually, if several such effects appear together, the modulator is called an electro-absorptive modulator. </p><p>Refractive modulators most often make use of an <a href="/facts/Electro-optic_effect/FNXrlPS2">electro-optic effect</a>. Some modulators utilize an <a href="/facts/Acousto-optic_effect/mlSxzC7m">acousto-optic effect</a> or <a href="/facts/Magneto-optic_effect/kJnv2D05">magneto-optic effect</a> or take advantage of polarization changes in <a href="/facts/Liquid_crystal/ehCCST89">liquid crystals</a>. The refractive modulators are named by the respective effect: i.e. electrooptic modulators, acousto-optic modulators etc. The effect of a refractive modulator of any of the types mentioned above is to change the phase of a light beam. The phase modulation can be converted into amplitude modulation using an interferometer or directional coupler. </p><p>Separate case of modulators are spatial light modulators (SLMs). The role of SLM is modification two dimensional distribution of amplitude and/or phase of an optical wave. </p> <h2 id="see-also">See also</h2> <ul><li><a href="/facts/Acousto-optic_modulators/mjsK4cGj">Acousto-optic modulator</a></li> <li><a href="/facts/Electro-absorption_modulator/LkFLL6RW">Electro-absorption modulator</a></li> <li><a href="/facts/Electro-optic_modulator/0qFT00Lf">Electro-optic modulator</a>, exploiting the <a href="/facts/Electro-optic_effect/FNXrlPS2">electro-optic effect</a></li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>"A magneto-optic modulator could facilitate the development of next-generation superconductor-based computers". September 26, 2022. <a href="https://techxplore.com/news/2022-09-magneto-optic-modulator-next-generation-superconductor-based.amp" target="_blank">https://techxplore.com/news/2022-09-magneto-optic-modulator-next-generation-superconductor-based.amp</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> </ol>