OptoDesigner Photonic Chip and Mask Layout

Lattice Filter Design Module

As integrated photonic designs become more complex, there is a need to move the design process to higher levels of abstraction to manage the complexity. The first step in this process was the development of process design kits (PDKs) that include standard photonic building blocks as well as enough information about the manufacturing process to enable designers to design their own specialized components. PDKs have advanced in this regard, with many foundries now supplying extensive information on their waveguide characteristics such as effective index, group index, dispersion and loss, and their dependence on waveguide width and bending radius. Additionally, PDK building blocks can have known or user-defined optical specifications; for example, a directional coupler with a given coupling ratio. This enables algorithms that use PDK information to synthesize a layout with a desired optical function. 

The OptoDesigner Lattice Filter Design Module automatically synthesizes optical filters given a user-directed optical specification. The software uses optimization algorithms to calculate a set of coupling ratios and phase shifts for a technology-agnostic filter based on a concatenated Mach-Zehnder Interferometer architecture. Once generated, the software can then synthesize a technology specific instance of the filter using information from the targeted foundry PDK. The filter is generated using PDK-based photonic building blocks and waveguides tuned with correct group and optical lengths.


The Lattice Filter Design Module enables designers to think of the filter as a technology-agnostic building block that can be synthesized to any target foundry process. This saves designers a considerable amount of time that would have been required to design and implement the filter by hand. It also gives designers the ability to map designs quickly to different foundry processes by simply using the building blocks already available in the foundry-supported PDK. 


Filters are used in a large number of photonic applications, such as interleavers or gain equalizers for long-haul telecommunications or excitation light suppression in biosensing. 


  • Automatic optimization of the coupling ratios, time delays, and phase shifts to best approximate the desired filter function
  • Filter is first synthesized to a technology-agnostic form which can then be retargeted to different foundry PDKs/processes
  • The order of the filter can be specified by the user. Designers can quickly evaluate trade-offs between higher-order filters that better approximate the desired spectrum versus the filter layout size and sensitivity to fabrication variance
  • Any free spectral range
  • Manhattan-style or sine-bend-style delay lines
  • Linear and folded layouts for different aspect ratio layouts
  • Integrated S-matrix simulation of synthesized layout
  • Semi-automatic generation of mode info data for storage in your own PDK


Figure 1. Gain equalizer: Desired and simulated spectrum

Figure 2. Folded layout

Figure 3. 6th order interleaver spectrum

Figure 4. Linear sine-bend layout implementation of an interleaver