Hi Zack,

I have two ideas on this!

1. Check where MATLAB is defined in OpticStudio. This can be done by navigating to Setup...Project Preferences...Folders:

2. If that looks fine, then you will need to update the Windows Registry. It sounds like when you downloaded Mathematica, the program updated the Windows Registry so that '*.m' files were opened by it as the default program. You know when you right-click a document and select 'Open With...' then 'Always use this program to open this file type'? That is updating the extension information in the Windows Registry. Here is some information on updating your machine's settings so that MATLAB controls *.m files instead: https://www.lifewire.com/how-to-change-file-associations-in-windows-2624477.

Even if neither of those suggestions works, you can just make a new Matlab document with the appropriate boilerplate information. I'm attaching the Standalone and Interactive boilerplate for MATLAB. OpticStudio will usually create this file and store it in the {Zemax}\ZOS-API Projects folder. Standalone applications will have a function title which matches the name of the created file:

Alternatively - navigate to the {Zemax}\ZOS-API Projects folder, find the file, right-click it, and select Open With...:

Best,

Allie