Component design for metasurfaces
With the right arrangement of nano-structures the metasurface can produce any optical reponse. With PlanOpSim software metasurfaces are defined easily and their response calculated. The software collects the full-wave results for each meta-atom. The behaviour of an entire surfac is then calculated using physical optics models. Components can be made both in a forward design where the structures are direclty choosen and placed or by inverse design where the target behaviour of the component is entered and the software determines the metasurface which produces that behaviour. Through combination of meta-atom design and placement, metasurfaces deliver characteristics that are impossible with conventional materials. Any classical optical component can be reproduced on a planar substrate as a metasurface as well.
Metalenses focus light through the co-operation of millions of sub-wavelength structures which individually manipulate the incident light locally. When the nano-structures are arranged to form a spherical wavefront a ‘perfect‘ (i.e. diffraction limited) lens is made. By traditional full wave modeling even a small 0.5x0.5 mm metalens is barely possible. With PlanOpSims combination of full wave and physical optics this task can be accomplished in a matter of minutes.
Above is an example of a metalens and its simulated intensity in the focal plane. The intensity profile shows the metalens produces a diffraction limited focus. The meta-atoms were simulated as Silicon Nitride pillars with diameter of 340nm and below on a glass substrate.
Inverse design: optimizing the projection of a holographic image
In real applications the intensity, polarization and spectrum you need, usually isn’t one where a textbook formula for the corresponding wavefront is easily found. PlanOpSim allows you to enter the target behaviour, the optimizer will then iterate through designs until the component matches the target behaviour.
Let’s say you want a diffractive optical element that projects the image of a cat when illuminated by a laser pointer. The optimization algorithm only needs to know the location and intensity of the image to calculate a nanostructure arrangement. Starting from a random first guess, the animation below shows how each trial solution approximates he target behaviour.
Integrated nano-structure calculation
PlanOpSims component level calculation is directly integrated with the full wave solutions of the nano-structures that make up the metasurface. When a meta-atom that was not known yet is discovered the model uses the full wave Maxwell equation solver to determine its response. The result is a powerful and versatile program to design metasurfaces. The method is fast enough to scan the design paramaters space in multiple directions. Tens of metalenses can be calculated in a matter of minutes.
Thanks to high speed computation and the integrated full wave solver, PlanOpSim software was able to perform sensitiviy analysis on a metalens where each of the meta-atoms underwent random deformations. Taking the average of multiple lenses reveals critical knowledge for the fabrication of metalenses.