Photonic Integrated Circuit

What is a photonic integrated circuit? 

An integrated circuit is chip containing electronic components that form a functional circuit, such as those embedded inside your smart phone, computer, and other electronic devices; a photonic integrated circuit (PIC) is a chip that contains photonic components, which are components that work with light (photons).

In an electronic chip, electron flux passes through electrical components such as resistors, inductors, transistors, and capacitors; in a photonic chip, photons pass through optical components such as waveguides (equivalent to a resistor or electrical wire), lasers (equivalent to transistors), polarizers, and phase shifters.

Photonic integrated circuit | Synopsys

How does a photonic integrated circuit work and what problem does it solve?

PICs use a laser source to inject light that drives the components, similar to turning on a switch to inject electricity that drives electronic components. Using light instead of electricity, integrated photonic technology provides a solution to the limitations of electronics like integration and heat generation, taking devices to the next level, the so-called “more than Moore” concept to increase capacity and speed of data transmission. PICs offer advantages such as miniaturization, higher speed, low thermal effects, large integration capacity, and compatibility with existing processing flows that allow for high yield, volume manufacturing, and lower prices. Applications for integrated photonics are broad – from data communications and sensing to the automotive industry and the field of astronomy.  

What industries and applications would PICs be good for?

One of the key application fields for PICs is data communications, followed by sensing (for agriculture and autonomous driving, for example), and biomedical applications such as lab-on-a-chip devices, as well as applications in the defense and aerospace industries and the field of astronomy. Improvements and additional applications for PICs continue to emerge as designers take on additional technological challenges for which integrated photonics may be useful and for which feasibility studies can determine whether it holds the promise of a solution. Services for such studies are provided by PIC consortia, design houses, and even some universities around the world.

What is the significance of developing PICs now?

With electronic integrated circuits arriving at the end of their integration capacity, PICs have the potential to be the preferred technology for data communications (inter- and intra-datacenter communications), LiDAR solutions for autonomous driving, sensing for aerospace and aeronautics, and untold future applications in a new technological era.

How do you develop and model a PIC?

A proper design and PIC process flow can be complex. Specific steps will vary depending on the application and foundry, but the basic steps are:

  • Identify your idea or requirement
  • Perform a feasibility study of your application
  • Design (considering PIC testing and packaging from the beginning):
    • Device level (optical, thermal, and material simulations)
    • Circuit level (virtual lab to test performance)
    • System level (PIC connected to a communications link)
    • Layout level (generate the design intent)
    • Verification (DRC and LVS for manufacturing compliance and high yield assurance)
    • GDS (check generated mask and replace black/white boxes if needed)
  • Process flow
    • Simulation of each process step
  • Fabrication
  • Testing
    • Wafer level
    • Chip level
  • Packaging
Process for modeling and developing a photonic integrated circuit | Synopsys

Synopsys’ Photonics Solutions tools offer a seamless PIC design flow to help model and design PICs at all required levels.

  • The RSoft Photonic Device Tools can be utilized stand-alone and are integrated with Synopsys Sentaurus TCAD products to provide streamlined, multi-disciplinary simulations of complex optoelectronic devices. Sentaurus TCAD geometry can be imported into RSoft photonic design tools such as FullWAVE FDTD for finite-difference time-domain (FDTD) analysis, BeamPROP BPM for rapid analysis of silicon photonics devices, and DiffractMOD RCWA for diffractive optical structure analysis.  Read this feature close-up for details.

  • At the circuit and layout levels, Synopsys’ PIC Design Suite offers circuit simulation with the capability of electro-optic simulation (using H-SPICE, for example) and mask layout implementation and verification capabilities for PICs, providing modular and synergistic integration toward first-time-right fabrication. 
The Synopsys PIC Design Suite – photonic integrated circuit design software that includes the OptSim Circuit and OptoDesigner tools – offers a seamless PIC design flow from concept to manufacturable design, as well as access to a single, world-class support channel. | Synopsys

A real world example of PIC design

The following steps describe the workflow used by a customer to design a PIC for an optical transceiver. 

  1. Install the foundry’s process design kit (PDK) for Synopsys tools.
  2. Make a schematic design in OptSim Circuit.
  3. Simulate the electrical part of the circuit with HSPICE and use the result in OptSim Circuit for optical simulation.
  4. Simulate the circuit and optimize the optical performance in OptSim Circuit.
  5. Use the Custom PDK utility to design custom devices when the standard PDK from the foundry doesn’t meet the design request. These custom devices can be used together with the foundry PDK components.
  6. Translate the schematic design into a layout by implementing it in OptoDesigner via the OptSim Circuit and OptoDesigner bi-directional interface. 
  7. Adjust the layout in OptoDesigner based on the footprint requirement.
  8. Back-annotate the layout change to the schematic design via the OptSim Circuit and OptoDesigner bi-directional interface.
  9. Re-simulate the circuit in OptSim Circuit to evaluate the impact of the changes.
  10. Adjust the schematic design in OptSim Circuit if necessary.
  11. Repeat steps 4 to 10 until both the performance and layout are optimized.
  12. Run a design rule check (DRC) on the layout implementation in IC Validator or OptoDesigner.
  13. Extract the netlist from the layout and implement and compare the netlist of the schematic design in IC Validator.
  14. Send the required files (such as the design in .gds format, DRC report, etc.) to the foundry for tape out.
PIC Design Example | Synopsys

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