{"id":305236,"date":"2023-09-07T06:50:33","date_gmt":"2023-09-07T06:50:33","guid":{"rendered":"\/forum\/forums\/topic\/issue-in-plotting-the-farfield-polarization-ellipse-for-a-quater-waveplate\/"},"modified":"2023-09-07T06:58:11","modified_gmt":"2023-09-07T06:58:11","slug":"issue-in-plotting-the-farfield-polarization-ellipse-for-a-quater-waveplate","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/issue-in-plotting-the-farfield-polarization-ellipse-for-a-quater-waveplate\/","title":{"rendered":"Issue in plotting the farfield polarization ellipse for a quarter waveplate"},"content":{"rendered":"

I designed a quarter waveplate and I used a circular polarized source to test whether it could transform the source back to a linear polarized light. I tried to plot the far-field polarization ellipse and analyzed the result. However, I met a problem when I set the theta angle and the phi angle to be 15 degrees and 45 degrees, respectively. The far-field polarization ellipse passed through this quarter waveplate is different from that of the source. I also tried other settings of angles, which are shown at the end of this post. From these settings, it seems that the passing light can be transformed back to the direction of the original source except in this setting “theta=15 and phi=45”. <\/span><\/p>\n

How should I understand these polarization ellipses and why does the result of the case “theta=15 and phi=45” look like this?<\/span><\/p>\n

As you can see from the following two results, if I set the phase difference between two sources to be 0, the polarized light is 45 degrees, while the circularly polarized light is transformed to 90 degrees polarized light after passing through the waveplate.<\/span><\/p>\n

(1)    <\/span><\/span>Source1<\/span>\uff1atheta=15<\/span>\uff0cphi=45<\/span>\uff0cpol=0<\/span>\uff0cphase=0; <\/span>Source2<\/span>\uff1atheta=15<\/span>\uff0cphi=45<\/span>\uff0cpol=90<\/span>\uff0cphase=0<\/span><\/p>\n

<\/a><\/a><\/span><\/p>\n

(2)    <\/span><\/span>Source1<\/span>\uff1atheta=15<\/span>\uff0cphi=45<\/span>\uff0cpol=0<\/span>\uff0cphase=0; <\/span>Source2<\/span>\uff1atheta=15<\/span>\uff0cphi=45<\/span>\uff0cpol=90<\/span>\uff0cphase=90<\/span><\/p>\n

<\/a><\/a><\/span><\/p>\n

 <\/p>\n

The structure is shown in the following pictures. The material of the meta-atom is “Si (Silicon) – Palik”, and that of the substrate is “SiO2 (Glass) – Palik”. The working wavelength is 850nm and the propagation direction is backward. The structure size of the meta-atom is 100nm in x width, 178nm in y width, 485nm in height, and 357nm in period.<\/span><\/p>\n

<\/a><\/span><\/p>\n

 <\/p>\n

Some other tests:<\/span><\/strong><\/p>\n

\uff081<\/span>\uff09Because the vector sum of two sources is along the y direction of the meta-atom, it only adds a global phase to the source. The direction of the polarization remains the same as that of the source.<\/span><\/strong><\/p>\n

Source1<\/span>\uff1atheta=15<\/span>\uff0cphi=45<\/span>\uff0cpol=0<\/span>\uff0cphase=0; <\/span>Source2<\/span>\uff1atheta=15<\/span>\uff0cphi=45<\/span>\uff0cpol=90<\/span>\uff0cphase=0<\/span><\/p>\n

<\/a><\/a><\/span><\/p>\n

Source1<\/span>\uff1atheta=15<\/span>\uff0cphi=45<\/span>\uff0cpol=0<\/span>\uff0cphase=0; <\/span>Source2<\/span>\uff1atheta=15<\/span>\uff0cphi=45<\/span>\uff0cpol=90<\/span>\uff0cphase=0<\/span><\/p>\n

<\/a><\/a><\/span><\/p>\n

\uff082<\/span>\uff09Because the vector sum of two sources is 45 degrees to the y direction, the circularly polarized light (ssource1 phase=0, ssource2 phase=90) is transformed back to a linear polarized light, whose direction is the same as that of a linear source (source1 phase=0, ssource2 phase=0).<\/span><\/strong><\/p>\n

Source1<\/span>\uff1atheta=15<\/span>\uff0cphi=90<\/span>\uff0cpol=0<\/span>\uff0cphase=0; <\/span>Source2<\/span>\uff1atheta=15<\/span>\uff0cphi=90<\/span>\uff0cpol=90<\/span>\uff0cphase=0<\/span><\/p>\n

<\/a><\/a><\/span><\/p>\n

Source1<\/span>\uff1atheta=15<\/span>\uff0cphi=90<\/span>\uff0cpol=0<\/span>\uff0cphase=0; Source2<\/span>\uff1atheta=15<\/span>\uff0cphi=90<\/span>\uff0cpol=90<\/span>\uff0cphase=90<\/span><\/p>\n

<\/a><\/a><\/span><\/p>\n

 <\/p>\n

\uff083<\/span>\uff09Because the vector sum of two sources is 45 degrees to the y direction, the circularly polarized light (ssource1 phase=0, ssource2 phase=90) is transformed back to a linear polarized light, whose direction is the same as that of a linear source (source1 phase=0, ssource2 phase=0). <\/span><\/strong><\/p>\n

Source1<\/span>\uff1atheta=15<\/span>\uff0cphi=45<\/span>\uff0cpol=45<\/span>\uff0cphase=0; Source2<\/span>\uff1atheta=15<\/span>\uff0cphi=45<\/span>\uff0cpol=135<\/span>\uff0cphase=0<\/span><\/p>\n

<\/a><\/a><\/span><\/p>\n

Source1<\/span>\uff1atheta=15<\/span>\uff0cphi=45<\/span>\uff0cpol=45<\/span>\uff0cphase=0; Source2<\/span>\uff1atheta=15<\/span>\uff0cphi=45<\/span>\uff0cpol=135<\/span>\uff0cphase=90<\/span><\/p>\n

<\/a><\/a><\/span><\/p>\n","protected":false},"template":"","class_list":["post-305236","topic","type-topic","status-closed","hentry","topic-tag-circular-polarization-1","topic-tag-polarization"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t