Critical Question

HalimBishoyHalimBishoy Member Posts: 6

I have a crucial question regarding " Metalens - Zemax Interoperability"

The focal length in this example is 100um

The radius of the metalens is 11.5um

How did they calculate those values?????

link example:

Metalens - Zemax Interoperability – Lumerical Support


  • kjohnsonkjohnson Posts: 91Ansys Employee

    Hello @HalimBishoy ,

    The focal length of 100 um was not calculated, this was the focal length that was targeted in the design. The actual focal length was determined with a plot of the electric field result from the FDTD simulation along the direction of propagation:

    As mentioned in the example:

    The calculated focal distance is somewhat off the target value of 100 um. This can be mostly attributed to the small lens size, hence the small number of nanorods to map the 2π  change over the lens radius. Increasing the lens size might help improve the results together with optimizing other parameters such as the period.

    The radius of the lens was also not calculated, this was chosen as a design constraint. As mentioned in the quote above, a larger lens could be used, which would likely give a better result. I'm not sure exactly how this lens size was chosen, but I would guess it was picked because this is roughly the radius required to give a full 2π phase change between the center and edges of the lens:

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