RSoft & Photonic Solutions Enewsletter

Quick Tip: Using OptSim Circuit and OptoDesigner for Electrical Autorouting

When designing photonic integrated circuits (PICs), there is often a need for active components that require electrical connections in addition to optical waveguides. With the introduction of the PIC Design Suite version 2019.09, OptoDesigner is now able to generate electrical ports and automated electrical routes when driven from OptSim Circuit with the bi-directional interface. This capability was supported in previous versions of the software for optical waveguides and works in a similar way for electrical connections. The main difference is that the composite elements (such as bends, straights, and vias) that define electrical routes are not stored as individual components in the shared design file.

In most PDKs provided by our foundry partners, the electrical autorouter is preset to route on two metal layers. One layer is used for horizontal routing and the other is used for vertical routing. When a route needs to go from the horizontal layer to the vertical layer, a via is automatically placed to connect the two layers completing the connectivity.

Figure 1. Autorouting feature creates optical and electrical connections in the generated layout

Opening the sample circuit as shown on the left in Figure 1 (the example file is available for download) generates the layout on the right. Note that the modulators now have both electrical and optical ports.

Adaptive Routing Layer Selection

In the example shown in Figure 2, the light blue layer is used for the metal that routes vertically and the dark blue layer is used to route horizontally. The latest release of OptoDesigner includes an enhancement that allows the initial and final sections of the route to be done in a different layer by using a via to transfer to the standard horizontal or vertical layer. Because the electro-optic modulator has its metal pads on the dark blue metal layer, the routing must start on this same layer. The electrical autorouting function takes care of this automatically.

Figure 2. Example of horizontal and vertical routing transfer

Please contact our technical support team at pic_support@synopsys.com for more information. The example design files featured in this tip are available on the Customer Support Portal.

RSoft Photonic Device Tools Feature Highlight: Polarization Analysis Plots

Because of the vectorial nature of light, most photonic devices are polarization sensitive. Version 2019.09 of the RSoft Photonic Device Tools includes a new feature that accurately analyzes a device’s polarization state by displaying the spatial variance in the polarization ellipse. You can access the feature with the complex vector option in WinPLOT: /vectc. Polarization analysis requires two 2D complex data profiles and displays the polarization ellipse within the plot.

As an example, we take the Q-plate for orbital angular momentum to show how a right-handed-polarization (RHP) Gaussian beam is converted into left-handed-polarization (LHP). The Q plate example is described in detail in this application note.

Figure 1(a) shows the nylon Q-plate with carved ring grooves on both sides of a disc [1]. A circularly RHP Gaussian beam is incident on it, as shown in Figure 1(b). With a full vectorial (3D) FullWAVE FDTD simulation, the complex Ex and Ey fields are recorded at different positions along the propagation direction (Z). The polarization plot and its magnitude at the end of the 10 mm thick disc is shown in Figure 1(c).

Figure 1: (a) the schematic Nylon Q-plate structure; (b) the polarization state at the input side; (c) the polarization state at the output side.

The following WinPLOT commands are used to create the plot in Figure 1(c):

/zw0
/cont -------------------------------- plot the magnitude of E field
/w-2e4, 2e4, -2e4 ,2e4
/vectc ------------------------------- plot polarization state of the field
/vectnum25 ------------------------ defined the number of polarization ellipses plotted with the data file
/vectbase1 ------------------------- #1 let the ellipses in plot based on the same size
/tt"Mon at (0,0,1e+004)"
/aspect1
NewQ_Output_monitor1_f0_ex.dat ---- complex Ex field data file
NewQ_Output_monitor1_f0_ey.dat ---- complex Ey field data file

The complex data files can be field or mode profiles obtained from the BeamPROP BPM, FullWAVE FDTD, DiffractMOD RCWA, ModePROP EME, or FemSIM MODE tools. Figure 2 is an animated polarization plot at different positions along the propagation axis from the input position at Z=0 to the end at Z=19mm. The polarization states and its change through the device are intuitively shown in this plot.

Figure 2. The polarization state changes along the device to outside of device.

Please contact our technical support team at rsoft_support@synopsys.com for more information. The example design files featured in this tip are available on the Customer Support Portal.

Reference:
[1] S. Maccalli, et al., "Q-plate for millimeter-wave orbital angular momentum manipulation," Applied Optics, Vol. 52, No.4, February 1, 2013. 

PDK Updates

Synopsys Photonic Solutions has the most comprehensive Photonic IC foundry support in the industry, with Process Design Kits (PDKs) available from foundries around the world for photonic processes such as silicon, silicon nitride, indium phosphide, polymers, and silica-on-glass. Our PIC Design Suite has enabled more than 1,500 tapeouts.

All supported PDKs for Multi Project Wafer runs are listed on our Customer Support Portal, including details about supported tool versions and how to access them. Recently the following PDKs have been updated:

  • TowerJazz PH18 PDK 18.4 for OptSim Circuit and OptoDesigner
    • Now includes the following processes: PH18MA, PH18MB, PH18MC, PH18MD
    • The die template was updated to be parametrized
    • New pad device was added
    • Design rules extended
  • AIM PDK 3.5 for OptSim Circuit and OptoDesigner
    • Now includes the silicon interposer process
    • Updated the cells of the layout geometry abstracts
    • Updated existing DRC and added DRC rules, added DRC grouping (to quickly enable or disable groups of rules for shorter runtimes
    • Added the parameters to enable default "Optical" and "Electrical" auto-routing

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