Discussion Forum

Hello, there!

I am attempting to replicate the blue-filter nanoarray composed of square-shaped nanostructures found in a paper by Yang et al 1. However, where the paper saw a peak resonance in reflectance at ~470 nm, I am seeing no peak resonance in between the wavelengths of 380 nm and 800 nm. Notably, this paper built their simulations in Lumerical, while I'm trying to replicate them in COMSOL 5.6.

I'm unsure why my attempt fails to replicate the results of the paper. I wrote down a summary of how I built the model at the end of this post, in case there's a glaring flaw that someone better-acquinted with COMSOL can spot. I also attached my .mph file for anyone's convenience.

I would appreciate help and insight! Thank you!

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I built my model by:

1. Creating a block layer under "Geometry", setting the width, depth, and height as appropriate.
2. Sectioning of the created block into three layers using the "Layers" subsection to denote (1) a substrate layer, (2) a layer for the nanoarray structures, and (3) a layer for air.
3. Creating a work plane layer under "Geometry".
4. Navigating to an automatically created sub-layer called "Plane Geometry" wherein I inputted coordinates to create a diamond with a circumradius of 1.
5. Applying the rotate, scale, and move transformations to (1) turn the diamond into a square, (2) expand the square to an appropriate width & length (195 nm each, as defined in the paper), and (3) position the square in the centre of the block layer created in step 1.
6. Updating the z-coordinates to have the square be on the boundary between the air and substrate layers.
7. Creating an extrude layer under the work plane layer to give the square a thickness (270 nm, as defined in the paper), transforming it into a three-dimensionsal nanostructure.

I used a physics-controlled mesh (attempted both the normal and fine options), and I defined different domains of the simulation as their appropriate material (materials were chosen from the in-built library in COMSOL 5.6). I created two periodic ports at either end of the model and used periodic boundary conditions.

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1 Yang, J.-H., Babicheva, V. E., Yu, M.-W., Lu, T.-C., Lin, T.-R., & Chen, K.-P. (2020). Structural Colors Enabled by Lattice Resonance on Silicon Nitride Metasurfaces. ACS Nano, 14(5), 5678–5685. https://doi.org/10.1021/acsnano.0c00185