# SMD PRO vs Published Data

The focusing results of a metalens simulated by SMD PRO is compared with measured data published in [Ref](https://pubs.acs.org/doi/10.1021/acs.nanolett.6b03626). The intensity distribution on the focal plane (Fig. 2e in the Ref.) and FWHM (Fig. 2h in the Ref.) are in good agreement with our results (image below).

* **Results comparison**

{% columns %}
{% column %}

<p align="center"><strong>SMD PRO</strong></p>

<p align="center">FWHM 0.46 µm</p>
{% endcolumn %}

{% column %}
[**Ref**](https://pubs.acs.org/doi/10.1021/acs.nanolett.6b03626)**.**

FWHM 0.497 µm
{% endcolumn %}
{% endcolumns %}

<figure><img src="/files/SVeuvTDdgAQtZl3BSyW2" alt=""><figcaption><p>SMD PRO simulation results. Left: intensity on focal plane (I<sub>xy</sub>). Right: intensity along y-axis (I<sub>y</sub>) on focal plane.</p></figcaption></figure>

* **Lens info**

  * Diameter 300 µm
  * Focal length 200 µm
  * Wavelength 0.532 µm
  * Unit cell shape circle and polarization-independent
  * 1,440,000 unit cells

* **Parameters used in SMD PRO**
  * BUILD module
    * Unit cell: SOI\_TiO2\_FusedSilica\_wvl0.532\_p0.25\_cir\_edge0
    * Unit cell arrangement conditions: transmittance min. 0.9 and phase error max 20 deg.
  * SIMULATE module (focusing)
    * I<sub>xy</sub>: resolution 25 nm
    * I<sub>y</sub>: resolution 5 nm (a separate simulation to pick up FWHM at higher resolution [without simulating I<sub>xy</sub>](#user-content-fn-1)[^1])
    * Circular aperture used with diameter 300 µm
    * Gaussian incident beam used with diameter 300 µm

{% hint style="info" %}
The intensity profile at the focal spot such as FWHM varies with the intensity profile or diameter of the beam incident on the focusing lens.

The authors of the Ref. used a fiber-coupled collimator to collimate a laser beam coming out of an optical fiber (see Fig. S2 in their [supporting document](https://pubs.acs.org/doi/suppl/10.1021/acs.nanolett.6b03626/suppl_file/nl6b03626_si_001.pdf)). This collimated laser beam was incident on their metalens for focusing test. Since the authors do not provide information about their collimated beam, the following assumptions were made for simulation in SMD PRO.

1. The fiber used for laser beam delivery is a single-mode fiber, thus the intensity profile of the beam exiting the fiber is nearly Gaussian.
2. The diameter of the collimated, (nearly) Gaussian beam incident on the metalens is equal to the metalens diameter.
   {% endhint %}

[^1]: This can be done by setting the 'Ixy xy-range' under OPTIONAL SETTINGS to a number close to 0 (e.g., 0.0001).


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