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<title>Diffraction efficiency</title>
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<span id="openzim-page-title" class="mw-page-title-main"><span class="mw-page-title-main">Diffraction efficiency</span></span>
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<p>In <a href="Optics" title="Optics">optics</a>, <b>diffraction efficiency</b> is the performance of <a href="Diffractive" class="mw-redirect" title="Diffractive">diffractive</a> optical elements – especially <a href="Diffraction_grating" title="Diffraction grating">diffraction gratings</a> – in terms of <a href="Power_(physics)" title="Power (physics)">power</a> throughput. It's a measure of how much <a href="Optical_power" title="Optical power">optical power</a> is diffracted into a designated direction compared to the power incident onto the diffractive element of grating.
</p><p>If the diffracted power is designated with <span class="texhtml mvar" style="font-style:italic;">P</span> and the incident power with <span class="texhtml"><i>P</i><sub>0</sub></span>, the efficiency <span class="texhtml mvar" style="font-style:italic;">η</span> reads
<span class="mwe-math-element mwe-math-element-block"><span class="mwe-math-mathml-display mwe-math-mathml-a11y" style="display: none;"><math display="block" xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \eta ={\frac {P}{P_{0}}}\ .}">
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<mi>η<!-- η --></mi>
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<mi>P</mi>
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<mi>P</mi>
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<mn>0</mn>
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<annotation encoding="application/x-tex">{\displaystyle \eta ={\frac {P}{P_{0}}}\ .}</annotation>
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<div class="mw-heading mw-heading2"><h2 id="Grating_efficiency">Grating efficiency</h2></div>
<p>In the most common case – the diffraction efficiency of optical gratings (therefore also called <i>grating efficiency</i>) – there are two possibilities to specify efficiency:<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup>
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<ul><li>The <i>absolute efficiency</i> is defined as above and relates the power diffracted into a particular order to the incident power.</li>
<li>The <i>relative efficiency</i> relates the power diffracted into a particular order to the power that would be reflected by a mirror of the same coating as the grating, therefore attributing to inevitable reflection losses at the grating but not caused by inefficient diffraction itself.</li></ul>
<div class="mw-heading mw-heading2"><h2 id="References">References</h2></div>
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<li id="cite_note-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-1">^</a></b></span> <span class="reference-text"><style data-mw-deduplicate="TemplateStyles:r1238218222">
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</style><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.shimadzu.com/products/opt/oh80jt0000001v0w.html">"Diffraction Efficiency & Relationship between Diffraction Efficiency and Polarization"</a>. Shimadzu Corporation. 2012<span class="reference-accessdate">. Retrieved <span class="nowrap">1 November</span> 2012</span>.</cite></span>
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<li id="cite_note-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-2">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://gratings.newport.com/library/technotes/technote10.asp">"Technical Note 10 – Guidelines for specifying diffraction gratings"</a>. Newport Corporation<span class="reference-accessdate">. Retrieved <span class="nowrap">1 November</span> 2012</span>.</cite></span>
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<div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2></div>
<ul><li><cite id="CITEREFChristopher_Palmer2020" class="citation web cs1">Christopher Palmer (2020). <a rel="nofollow" class="external text" href="https://www.gratinglab.com/Information/Handbook/Handbook.aspx">"Efficiency Characteristics of Diffraction Gratings"</a>. <i>Diffraction Grating Handbook (8th edition)</i>. MKS Newport<span class="reference-accessdate">. Retrieved <span class="nowrap">13 March</span> 2020</span>.</cite></li></ul></div><!--htdig_noindex--><div><div class="zim-footer">
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