KLayout to FDTD to INTERCONNECT integration

[lukasc-ubc]

Objective: run a 3D-FDTD simulation for a KLayout component to generate the S-Parameters; automatically import them into INTERCONNECT to enable circuit simulations.

Concept based on 2014 UBC-Mentor Graphics project by Shiyu Stephen Liang, Trammy Nguyen, and Phuong Tran.

Approach:

• User defines a cell in KLayout (fixed or parameterized PCell), including DevRec and PinRec
  • Lumerical_INTERCONNECT_component=gds2fdtd: KLayout will treat this as regular component, with a Spice command that will ask INTERCONNECT to load the simulated S-parameters
  • Configuration for the FDTD simulation in KLayout (text label within the cell; alternatives: a global GUI - how do you save settings?, hardcoded):
    • wavelength range
    • polarization
    • FDTD mesh accuracy
    • PCell parameters
    • example: Spice_param:"load from file"=true "s parameters filename"="wraparoundDC_1550nm_100nm_TE_mesh3_PCellParam1_1e-6_PCellParam2_50e-9.dat" (for an example component called "wraparoundDC") (no equal signs allowed in the Spice file parameters)
• Menu for SiEPIC - Simulation - Simulate component using FDTD:
  • if one component selected, simulate only that one; if none selected, find all gds2fdtd components which don't have an S-Param file on disk and simulate them all.
  • determine a cell name from the cell text (including simulation parameters and PCell parameters); use this for the GDS export, the S-parameter file to be created, and for INTERCONNECT to load the S-param file.
  • export the cell as a GDS, saved in the project folder
  • FDTD script (.lsf) embedded within KLayout Python macro. Call FDTD with LSF script to: load GDS, solver configuration, Ports (using Lumerical's new S-param ports), save S-Param file in the same project folder using the above filename
• SiEPIC - Verification:
  • extra functionality to error-check that the S-Param file for the gds2fdtd component exists.
• KLayout-INTERCONNECT: run circuit simulations.
  • create netlist as usual, with a special function to deal with the gds2fdtd component. (unless we can just use the component name = SPAR, and the Spice_param parameters used to pass the filename to load)
  • Implement as an N-port SPAR import with a specified file

Double-check if this will work / figure out:

• check that a netlist can include an N-port SPAR import with a specified file.

  • doesn't work on the SPAR built-in, but created a component gds2fdtd which is a copy of the SPAR. Successfully loads S-Params and changes the number of ports via the syntax:
    spar N100 N101 gds2fdtd library="Custom/ebeam_v1.2" sch_x=50 sch_y=10 "load from file"=true "s parameters filename"="/Users/lukasc/SiEPIC_EBeam_PDK/Lumerical_EBeam_CML/ebeam_v1.2/source_data/bdc_TE_source/EBeam_1550_TE_BDC.sparam"
  • added gds2fdtd component to CML: lukasc-ubc@41a45ef

• Figure out the port ordering, and make sure KLayout/FDTD/INTERCONNECT are consistent.

  • changing the name of the ports in the S-Param.dat file (e.g,. from "port 1" to "port A") doesn't change the name of the ports in the INTERCONNECT component. (added a question on Lumerical: https://kx.lumerical.com/t/optical-ports-extracting-s-parameters/3773/2)
  • maybe just do what already do for the other components: sort the KLayout pins in alphabetical order, and export these into FDTD in order where FDTD/INTERCONNECT will use the default "port 1", "port 2" and so on. Then they will be correctly connected.

• FDTD settings:

  • material model: configure to fit Silicon - Palik over a range of 1.2 to 1.7 (hard coded)
  • use PMLs with reduced reflections (say -50 dB)
  • use metal for z-min z-max

Also, stop using /tmp for the spice & ICP files? Instead, put the in the folder where the GDS is saved, which will make it easier to keep track of all the project files (including the new S-parameters, which should be permanently saved for future simulations).