taper in two dimensions


#1

Hello all

Can I draw a taper in 2 dimensions like the following figure

The z min for start and end facets is zero. The start facet has height of .5 um and width of 2 um.
The end facet has height of 0.25 um and width of 0.75 um.

I tried addpoly; but it cannot do this.
addpyramid; also dos not give the desired result.

Any help will be appreciated.


#2

Hi,

“Structures” -> “pyramid” (https://kb.lumerical.com/en/ref_sim_obj_structures_pyramid.html)
should suit your needs.


#3

I tried addpyramid; command but it tapers the upper and down walls with the same ammount. It is not my case. The lower wall has 90 degree with the vertical while the above wall tapers down with angle theta=atan((0.5-0.25)/L), where L is the length of the taper.

My design is not symmetric.


#4

Then override the undesirable part of the polyhedron (“1”+“2”) with a volume with the same optical properties as of the ambient material (“2”):


#5

I do not understand what is polyhedron?

Can you explain that?


#6

the pyramid from “structures”


#7

Dear msaygin

your structure still has discontinuity in y direction between the two blocks you used. Please see the following figure.

The input and output waveguide should have the same cross section as the taper input and output facets. It looks like 3d taper.


#8

@omnia.nawwar,

why don’t you like the approach I suggested before for this structure?
You can cross-section the very same way the following compound:


#9

The problem is I am not tapering to the middle of the structure, like the figure above. I am tapering to one side.


#10

Dear @omnia.nawwar,

As I wrote in my previous post, the structure from the figure can be cross-sectioned by a half-space (with ambient material parameters) to obtain that is seen in your sketch. If it does not suit you, then I do not understand what you want. In that case, please, re-draw the sketch.


#11

Dear @omnia.nawwar

I think the geometry that @msaygin proposed answers your question. All he did, which is a smart approach, is to build a full pyramid (from structure tab) and then override the half with an etched material. Here is the simulation file that contains the geometry in your first post:

half_pyramid.fsp (276.5 KB)

Please let us know if you still have any questions.

Thanks


#12

I see it now. Really smart approach indeed. I could not see it before till I saw the 3D-structure you provide, so thank you.

@msaygin Thank you very much. Indeed smart and simple work