Photonic Solutions Enewsletter

June 2019

Quick Tip: New GDS File Import/Export Approaches with RSoft CAD

Designs for photonic devices such as photonic integrated circuits (PICs) and diffractive optical elements (DOEs) are commonly represented by one or more graphic data system (GDS) mask files. These files contain information about the design such as the layer layout, shapes, and text labels. This tip describes several ways to import and export GDS files within the RSoft CAD Environment™.

1.       Dynamically Import GDS via Hierarchy

The RSoft CAD is a hierarchical design environment where a design can be a combination of items such as native components, other designs, and GDS files. This tip will focus on using GDS files dynamically within the RSoft CAD with a circuit reference (a component that refers to another design). Figure 1 shows a sample Properties for Circuit Reference dialog box in which a GDS file has been selected by the External File option. By default, all layers within the GDS will be imported in the XZ plane. However, a specific layer can be imported using the file:layer# syntax as shown in Figure 1. Alternatively, you can import the layer to the XY plane using the file:layer#,xy syntax. The material, position, thickness, and other properties of each circuit reference component can be separately controlled, allowing complicated designs to be easily built from one or more layers. Furthermore, you can combine GDS-defined structures with native structures to achieve fully custom structures.

Figure 1. CAD hierarchy import dialog

Figure 2 shows a simple vertical grating coupler imported with two layers. Two circuit reference components were used, one for each layer in the GDS file.

Figure 2. A vertical grating coupler GDS import example with multiple layers

Figure 3 shows a Dammann grating mask imported to both the XZ and XY planes. Note that the GDS import is dynamic; if you change or modify the GDS file, the RSoft layout is updated to reflect the changes. If needed, you can also permanently convert the GDS to an RSoft .ind design file with the gds2ind command-line utility.

Figure 3. A Dammann grating mask imported in the XZ and XY planes via hierarchy

2.       Using GDS Export Options

The RSoft CAD supports GDS export, which is a required step before sending a device for verification and fabrication. GDS files can be exported from either the XY, XZ, and YZ planes for all components in the design or at a specific cut position. Figure 4 shows a Dammann grating exported to a mask in a Z cut specified in the Export GDS dialog box (menu CAD File > Export > GDS). The GDS data can be spatially clipped to a range that defaults to the simulation domain. The GDS export process can be automated via script using the using the ind2gds command-line utility.

Figure 4. A Dammann grating exported to a GDS mask via Z cut plane

For more details about importing and exporting GDS files in the RSoft CAD Environment, refer to Section 6.E in the RSoft CAD User Guide.

Support: OptoDesigner Portal Updates

Expanded Technical Support Information for the PIC Design Suite

We have expanded our PIC Design Suite technical support information on our website at Visit the new page for convenient access to information about obtaining software and license files, installing the tools and Process Design Kits (PDKs), accessing our enewsletters, and more.

Updated OptoDesigner Section on Customer Support Portal

We have also updated and redesigned OptoDesigner product information on our Customer Support Portal. Register now to access OptoDesigner training videos, user guides and online help, PDK installers, and an all-new FAQ section. Learn how our PIC Design Suite, which includes OptoDesigner and OptSim Circuit, is driving the PIC revolution!



This PDK is a plug-in library for OptoDesigner and OptSim Circuit and supports the Multi Project Wafer runs provided by AIM Photonics. The PDK is developed by Analog Photonics and the latest update includes newly implemented chipframes. The update supports the interface between OptSim Circuit and OptoDesigner. In addition to photonic elements from the standard generic design library, this PDK contains technology specific information including:

  • mask layer names
  • design rules
  • validated building blocks
  • s-matrix compact models
  • die sizes
  • GDS file settings 


The AIM PDK will be available for users via MOSIS



This PDK is a plug-in library for OptoDesigner developed by AMF. In addition to the photonic elements from the standard generic design library, the PDK contains technology specific information including mask layer names, design rules, validated building blocks, die sizes, and GDS file settings. The following updates have been added:

  • new Pcells: Via1 and Via2
  • redirected metal connectivity MT1

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