Learning Forum

[uzmayaqoob1960]

focusing spot at 0 degree appears to be somewhat strectched like,Why it is so? Same is the case when we are interested to focus light at (-r,180degree) plz help to understand it .Would it due to comatic aberration ?if it is so then plz help me to understand it.

[Guilin Sun]

I believe it is not due to comatic aberration. It might be due to the polarization. Please check if the two sports are due to the two linearly polarized light sources: use linear polarization (eg, Ex and Ey) as the source and check the images. are they angled incidence? does the metalens has 90deg rotation symmetry ?

you may also check if the simulation is wide enough to reduce the diffraction effect caused by PML truncation to the incident plane wave. 

please provide some screenshots about the device and settings.

[uzmayaqoob1960]

Dear sir 

its basically under the normal incidence of light. We have used rotation of nanobars under Pancharnam Berry phase concept to realize inplane rotation of nanobars of same dimensions to develop a metasurface.But when we find FWHM Full width half maximum for the spot located at 0deg that is bit compromized rather than the spot focused at 90 degree.

[Guilin Sun]

Understood.

I guess 0 deg mean x=0,y=0. right?

So the two spots rotated. 

Without more details of simulation settings it is hard to tell if there is a problem. It seems normal. As suggested previously, you may try to simulate two orthogonal polarization light sources and see what happens.