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Modeling Graded Index lens (GRIN) based 3-port coupler in sequential mode.

  • 2 August 2020
  • 8 replies
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C

I am attempting to model a GRIN TFF based 3 port coupler in zemax non-seqential mode. When using comercially available GRIN lens ZMX files in sequential mode, propagation is sinusoidal as expected for GRIN propagation. When I export to non-sequential mode it seems GRIN lens is no longer; propagation is linear and now this cylindrical lens seems to have uniform index of refraction instead of radially varying index of refraction.


Additionally I hope to model a variety of TFFs. Any resources on these subjects would be apreciated.


-Chris

uniformindexseq.png
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Best answer by Berta.Bernad 3 August 2020, 13:23

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C

Additional info

3portcoupler.png
Berta.Bernad
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Hi Christopher,


All gradient index materials used by non-sequential objects are defined in a separate program called a Dynamic Link Library (DLL), so the convertion from sequential to non-sequential is no direct.


If you have a comercial lens and want to convert it to non sequential, after the conversion, go into the Object Properties for the lens object. On the Gradient Index tab, check ‘GRIN’ and then choose the DLL you wish to use. (The DLLs for grin1-10 correspond to the behavior of the similarly named sequential GRIN type).Then, you will need to take the parameters used to define your gradient surface in the Lens Data Editor of the Sequential file and copied them in to the Object Properties here. 




Regarding the Thin Film question, OpticStudio can model any type of thin-film coating, including multilayer dielectric and metallic coatings. I'd recommend you to have a look at the following articles that explain how to model them:


https://my.zemax.com/en-US/Knowledge-Base/kb-article/?ka=KA-01668


https://my.zemax.com/en-US/Knowledge-Base/kb-article/?ka=KA-01539


Best,


Berta


 

C

Hello, I am not able to preform these functions. I have attached a word document with several screenshots for your review.


While in sequential mode:Under the surface properties in sequential mode you can see that there is no reference to an INDEX tab, and surface type is set to gradient 9.  Note: there is no option to enter deltaT n0 Nr2 for gradient 9. If I experimentally switch to gradient 5 these categories are available as shown below.


I then revert to gradient 9 export to sequential mode, Now note that in in Non-Sequential mode you will see that the index tab is greyed out.


I am not able to select GRIN, or select a index DLL. FYI I am using optics studio  20.2 professional, is this an issue?


Thank you for your help, 


Chris

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Allie
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Hi Chris,


Thank you for sharing that document. Actually, there is nothing wrong with the version you're using! I will list my answers below:


1. Sequential Mode does not have an Index tab in the Surface Properties. Instead, the gradient index data is added as a set of extra data parameters as shown in the first screenshot shared by Berta. In Non-Sequential Mode, the GRIN settings are moved into Object Properties (shown in the second screenshot shared by Berta). 


2. The Gradient 9 surface has different inputs than most other GRIN surfaces in Sequential Mode. Is this the surface type used by the manufacturer? The definition of that surface is given in the Help System file 'The Setup Tab > Editors Group (Setup Tab) > Lens Data Editor > Sequential Surfaces (lens data editor) > Gradient 9':


 



 


You can use the information in the Help System file 'The Setup Tab > Editors Group (Setup Tab) > Non-sequential Component Editor > Non-sequential Overview > Defining GRIN Media for Non-sequential Ray Tracing > Sample GRIN DLLs' to determine which DLL you need to use after converting the file. GRIN9 will be closest, but there are other DLLs available to you beyond that. Here is the information for GRIN9:


 



 


3. In Non-Sequential Mode, the Index tab will not appear for 'surface'-type objects. This is because 'surface' objects are seen as infinitely thin planes which cannot have a material assigned. I see in your document that you are attempting to add the index data to object #5 which is a Grid Sag Surface. This surface is actually being used in conjunction with surface #6 to form the Compound Lens object. That Compound Lens represents your Gradient 9 surface, so that is where you will add your index data. 


 


Let me know if you have any other questions about this!


Best,


Allie

Allie | Team Lead Application Engineering | Zemax, Ansys
C

Sorry for my naivety, I have attached a word document with screenshots for your review. To reiterate, I trying to model a .25 pitch GRIN lens at 1560nm in non-sequential mode. I have taken the ZMX file for .29 pitch GRIN 2915 from Thorlabs repository listed below:


https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=1209


The only modifications I made to this file was changing lens length to 4.818 to make the lens .25 pitch at 1560nm. I also set object at GRIN face as shown. Yes it seems Gradient 9 is what the manufacturer has used.


After making attempts as you have explianed, It seems this it is still not working. 


Thank you for your help


-Chris

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Berta.Bernad
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Hi Chris,


When converting your file to Non-Sequential, you need to add your index data in the Compound Lens object (#6), without changing its parents surface objects (#4 front face and #5 back face):



I attach a sample file so you can check it :)


Best,


Berta

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C

Hi Berta, 


thank you so much for your response, your example works flawlessly! I think I have understood now however it is still not working when I try to convert the lens myself. After I add index data in the Compound Lens object (#7), without changing its parents surface objects #5 and #6 It keeps saying invalid gradient index media. I have attached some screenshots for your review.


Thank you so much,


Chris

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Berta.Bernad
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Userlevel 3
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Hi Chris,


I'm glad we could help! 


You forgot to set parameter 'g' in the 'Grin9.DLL', which is fixed at 2.0 for the sequential surface Gradient9:



It should do the trick

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