Power Coupling Efficiency Enhancement in Multimode Step-Index Fiber Using Refractive and Diffractive Microlenses

<table>Power coupling efficiency <svg height="9.875" id="M198" style="vertical-align:-2.29482pt" version="1.1" viewbox="0 0 7.9375 9.875" width="7.9375" xmlns="http://www.w3.org/2000/svg">
<g transform="matrix(1.25,0,0,-1.25,0,9.875)">
<g transform="translate(72,-64.1)">
<text transform="matrix(1,0,0,-1,-71.95,66.44)">
<tspan style="font-size: 12.50px; " x="0" y="0">𝜂</tspan>
</text>
</g>
</g>
</svg> is shown as a function of beam halfwidth <svg height="11.025" id="M199" style="vertical-align:-3.21404pt" version="1.1" viewbox="0 0 22.875 11.025" width="22.875" xmlns="http://www.w3.org/2000/svg">
<g transform="matrix(1.25,0,0,-1.25,0,11.025)">
<g transform="translate(72,-63.18)">
<text transform="matrix(1,0,0,-1,-71.95,66.44)">
<tspan style="font-size: 12.50px; " x="0" y="0">𝜔</tspan>
</text>
<text transform="matrix(1,0,0,-1,-63.44,63.31)">
<tspan style="font-size: 8.75px; " x="0" y="0">2</tspan>
<tspan style="font-size: 8.75px; " x="4.3759999" y="0">𝑥</tspan>
</text>
</g>
</g>
</svg> at the beam waist for different beam halfwidth <svg height="12.925" id="M200" style="vertical-align:-4.74141pt" version="1.1" viewbox="0 0 22.2875 12.925" width="22.2875" xmlns="http://www.w3.org/2000/svg">
<g transform="matrix(1.25,0,0,-1.25,0,12.925)">
<g transform="translate(72,-61.66)">
<text transform="matrix(1,0,0,-1,-71.95,66.44)">
<tspan style="font-size: 12.50px; " x="0" y="0">𝜔</tspan>
</text>
<text transform="matrix(1,0,0,-1,-63.44,63.31)">
<tspan style="font-size: 8.75px; " x="0" y="0">2</tspan>
<tspan style="font-size: 8.75px; " x="4.3759999" y="0">𝑦</tspan>
</text>
</g>
</g>
</svg> at the beam waist. The wave length of the Gaussian beam 0.8 <i>μ</i>m, the fibre parameters are <svg height="14.7875" id="M201" style="vertical-align:-3.13504pt" version="1.1" viewbox="0 0 60.724998 14.7875" width="60.724998" xmlns="http://www.w3.org/2000/svg">
<g transform="matrix(1.25,0,0,-1.25,0,14.7875)">
<g transform="translate(72,-60.17)">
<text transform="matrix(1,0,0,-1,-71.95,63.35)">
<tspan style="font-size: 12.50px; " x="0" y="0">𝑛</tspan>
</text>
<text transform="matrix(1,0,0,-1,-65.74,60.22)">
<tspan style="font-size: 8.75px; " x="0" y="0">1</tspan>
</text>
<text transform="matrix(1,0,0,-1,-57.39,63.35)">
<tspan style="font-size: 12.50px; " x="0" y="0">=</tspan>
<tspan style="font-size: 12.50px; " x="12.027886" y="0">1</tspan>
<tspan style="font-size: 12.50px; " x="18.279387" y="0">.</tspan>
<tspan style="font-size: 12.50px; " x="21.405136" y="0">4</tspan>
<tspan style="font-size: 12.50px; " x="27.656635" y="0">5</tspan>
</text>
</g>
</g>
</svg>, <svg height="11.45" id="M202" style="vertical-align:-0.23827pt" version="1.1" viewbox="0 0 50.287498 11.45" width="50.287498" xmlns="http://www.w3.org/2000/svg">
<g transform="matrix(1.25,0,0,-1.25,0,11.45)">
<g transform="translate(72,-62.84)">
<text transform="matrix(1,0,0,-1,-71.95,63.12)">
<tspan style="font-size: 12.50px; " x="0" y="0">Δ</tspan>
<tspan style="font-size: 12.50px; " x="12.490497" y="0">=</tspan>
<tspan style="font-size: 12.50px; " x="24.530886" y="0">1</tspan>
<tspan style="font-size: 12.50px; " x="30.782387" y="0">%</tspan>
</text>
</g>
</g>
</svg> and <svg height="11.1" id="M203" style="vertical-align:-0.17555pt" version="1.1" viewbox="0 0 69.150002 11.1" width="69.150002" xmlns="http://www.w3.org/2000/svg">
<g transform="matrix(1.25,0,0,-1.25,0,11.1)">
<g transform="translate(72,-63.12)">
<text transform="matrix(1,0,0,-1,-71.95,63.35)">
<tspan style="font-size: 12.50px; " x="0" y="0">N</tspan>
<tspan style="font-size: 12.50px; " x="8.8021116" y="0">A</tspan>
<tspan style="font-size: 12.50px; " x="21.292608" y="0">=</tspan>
<tspan style="font-size: 12.50px; " x="33.332996" y="0">0</tspan>
<tspan style="font-size: 12.50px; " x="39.584499" y="0">.</tspan>
<tspan style="font-size: 12.50px; " x="42.710247" y="0">2</tspan>
<tspan style="font-size: 12.50px; " x="48.961746" y="0">5</tspan>
</text>
</g>
</g>
</svg>.</table>

International Journal of Optics

fig8

Figure 8

Figure 8: Power Coupling Efficiency Enhancement in Multimode Step-Index Fiber Using Refractive and Diffractive Microlenses 