[Webinar] Zemax and Lumerical: Part 2 - From Nano-scale to Macro-scale Optics and Back [Q&A]

Hello All,

Thank you for joining this webinar!

In this thread below, Shin-Sung and I will answer the questions we didn’t get to during the live event.

Besides, you may find a detailed discussion of the workflow and the application example in this Lumerical Knowledgebase article:
Metalens - Zemax Interoperability – Lumerical Support
The sample files used during the webinar are also available for download as an article attachment.

If you have any further questions, please feel free to ask!

Csilla

Q: Is there limitation on the lens radius using Binary 2 surface? When I used a radius larger than 1 mm, the result does not seem to work well. I might not operate it properly though.

A: There is no limitation on the semi-diameter of the lens when using the Binary surface types, however, there is a Normalization Radius parameter, which scales the ray-interception coordinates for the phase polynomial evaluation. If the normalization radius is not set up properly, you might have difficulties determining the additional phase. Using the semi-diameter of the lens as the normalization radius can be good starting point.
You may find further details and sample cases about how to use the Binary 2 surface type in this Knowledgebase article:
How to model diffractive optics using the Binary 2 surface – Knowledgebase (zemax.com)
If you have further questions about a specific file, please feel free to open a new forum thread for a discussion about it or you may send your file over to Zemax Support so that we can take a look at it and help troubleshooting.

@Dmitriy.Strelkov 

Q: How do you figure out the pitch of the pillars (meta-elements)?

A: The choice of the pitch of the pillars (=x/y span of the unit cell simulation region) will mostly depend on the wavelength in consideration. In most metalens designs, it would be desirable to avoid any higher order diffraction as it can complicate the design and the interpretation of the results. For that reason, it might be necessary to set the pitch of the pillas to be smaller than the half-wavelength. With that in mind, you might need to do some sweeps over the pitches to figure out the best choice of pitch that give you the desired phase range and transmission/reflection.

Q: Are there plans to make the RCWA module more user friendly (GUI, easier layer building) in the future?

A: Yes, a dedicated GUI for RCWA is something we are currently working on. We cannot give a firm dates for its release, though.

Q: What is the rule of thumb in choosing mode number in RCWA? What I meant by “mode number” is “k-vector number.”

A: As with any simulation, this is a matter of convergence. To obtain an accurate result that you can trust, you will need to run a convergence test over the key simulation parameters. The number of k-vectors could be one of the key parameters you want to do the convergence test on in RCWA. If you have a tapered cone in the propagation direction, you will need to approximate the structure with a number of cylinders and also do convergence tests on the number of cylindrical layers to faithfully represent the cone structure.
The number of required k-vectors to obtain a converged result will vary depending on the structures, material and sources you are dealing with.

@Yisi.Liu 

Q: Metalens can be designed to be polarization-sensitive. How to include such feature in your design process?

A: The Metalens Webinar and the associated Application Gallery example uses a cylindrical meta-atom, hence polarization insensitive. But the proposed design flow can be easily adapted to address the polarization-sensitive devices. The required changes would typically involve:

• Build the phase and field libraries of unit cell for geometric parameters and the polarization (x- and y-polarized)
• When reconstructing the field for the whole metalens, construct the field for each polarization.
• To obtain a response for the whole lens to an input with an arbitrary polarization (a*E_in_x+a*E_in_y), you simply give an appropriate weighting to the whole lens response to each input polarization and sum them (a*E_whole_out_x+b*E_whole_out_y).

Hope this makes sense.

@Dani.K 

Q1: I would like to ask you if I can design my source in HFSS and then import it to Zemax and how. And how can I change the Y position of my source for example.

A1: Would you please provide more detailed information about i) what you want to achieve with the combined workflow HFSS and Zemax and ii) the source itself (wavelength, the beam shape and how the “source” is defined). With the Webinar being based on the interoperability between Lumerical and Zemax, I wonder what might be the reason behind the use of HFSS in this case. Are you considering taking the workflow learned here and adapt it to something different?

Q2: At the end, I would like to know if it can implement an incoherent detector with a Pixelarray.

A2: Do you have any reference for the application you mentioned? Some sketch of the detector would help us to understand what you might need and whether/how the metalens workflow has any relevance to it.