Creating custom waveguides in KLayout with SiEPIC

Creating custom waveguides in KLayout with SiEPIC

Once installed over KLayout the AIM PDK with SiEPIC tools includes the most frequently used waveguide materials and widths for the AIM MPW foundry. However, sometimes other widths may be desired for custom designs. In order to take advantage of the SiEPIC tools additional waveguides need to be defined in the WAVEGUIDES.xml file, as outlined below.
PLEASE NOTE: if or when you upgrade to a newer version of the AIM PDK these these updates would be overwritten. Therefore, you would need to make these changes again, or save a copy of your WAVEGUIDES.xml file and merge it after upgrading.

  1. Navigate to the AIM Photonics KLayout “tech” folder, typically installed here:


    C:/Users/[username]/KLayout/tech/AIMPhotonics_PDK



  2.   In the tech folder, open the WAVEGUIDES.xml file using a text editor (e.g., Notepad++)
  3. The WAVEGUIDES.xml file contains the specifications for each waveguide. To create a new custom waveguide, select the code for an existing waveguide. This will be from the <waveguide> tag to the </waveguide> tag, as in Figure 1.


    Figure 1. The code for the 1.2um FNAM waveguide has been selected.
  4. Copy and paste the code on new lines.
  5. Edit the code as desired (see Figure 2). The parameters in this code refer to the following:
    1. wg_width: The width of the waveguide
    2. CML: The library from which the model will be drawn (if a model exists, otherwise this line can be removed)
    3. Model: The specific model to use (if a model exists, otherwise this line can be removed)
    4. Component
      1.   Layer: The layer within the component that you are going to be specifying parameters for, where the layers are:
        1. REAM, SEAM, FNAM, or SNAM: This is the actual GDS layer that will be used for the waveguide
        2. Waveguide: This is the SiEPIC layer that lets SiEPIC know this is a waveguide component
        3. DevRec: This is the “Device Recognition” layer used by SiEPIC for pin snapping
      2. Width: The width of the layer
        1.   For the Si/SiN layer and the Waveguide layer, this parameter should equal the waveguide width
        2.   For the DevRec layer, this parameter should be a few microns larger than the waveguide width
      3. Offset: The offset of the layer from the center of the waveguide (should be 0 except for when making a rib waveguide with REAM at a nonzero offset)


        Figure 2. The code from Figure 1 has been copied, pasted, and edited to create a 1.0um-wide FNAM waveguide.
  6. Save the file.
  7. Test the file by opening a layout, drawing a path, selecting the path, and pressing hotkey “2” (Path to Waveguide, GUI) to verify that the new waveguide option appears in the configuration list, as in Figure 3.

         



Figure 3. Verifying that the new 1.0um-wide FNAM waveguide appears in the Configuration drop-down.




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