This project demonstrates the design and generation of photonic integrated circuit (PIC) layouts using the DemoFab PDK within the Nazca Design framework. The workflow progresses from basic passive structures such as straight waveguides and routing bends, through MMI-based splitters, ring resonators, and splitter networks, and concludes with active and foundry-level components including SOA amplifiers and DBR-based semiconductor laser structures.
All layouts were exported to GDS-II format and validated in KLayout using an appropriate .lyp layer property file to closely reflect fabrication-realistic visualization.
| Stage | Technology Used |
|---|---|
| Layout generation | Nazca Design (Python, DemoFab PDK) |
| Layout inspection | KLayout + .lyp layer configuration |
| Optical layers | waveguide core, etch region, annotation layers |
| Component types | MMI, curved waveguides, ring resonators, MZI, DBR, SOA |
This layout represents a basic optical routing structure consisting of a straight waveguide section followed by a gradual bend and a semi-circular curvature with a bend radius selected to minimize propagation losses. The final segment transitions back into a vertically oriented straight waveguide. The hatch pattern distinguishes the optical core layer from the surrounding etch region that defines the physical confinement of the guided mode.
The ring structure forms a closed optical path that may function as a resonator, filter, or coupling element depending on the waveguide spacing and fabrication process parameters. A straight bus waveguide is placed adjacent to the ring to enable evanescent coupling. The adopted layer coloring and hatch patterns distinguish between the optical core, etch region, and auxiliary process layers defined by the DemoFab PDK.
The repeated patterned areas correspond to multiple instantiated layout cells, illustrating the hierarchical design approach enforced by the PDK. The overlapping geometry at this stage is intentional - it results from generating a grid of instances for the purpose of studying naming conventions, port propagation, and geometry inheritance mechanisms within Nazca Design.
This structure contains Multimode Interferometer (MMI) elements connected via waveguides. Each MMI cell includes defined input and output optical ports and technology-specific metadata. Routing between ports forms a functional 1×2 optical splitter. The visible layers include the waveguide core, etch boundary, and PDK annotation layers.
The optical path begins with a single input waveguide connected to a 1×2 MMI splitter. The signal is subsequently cascaded through multiple MMI stages, forming a branching architecture comparable to a tree topology. Such structures are representative of PIC designs used in WDM systems, multi-channel sensors, and interferometric measurement networks.
The rectangular blocks correspond to predefined foundry-validated components such as DBR lasers, thermal phase sections, and amplifier segments. Unlike earlier parameterized structures, these are fixed standard cells supplied by the PDK and include embedded metadata such as process versioning, component type, and ownership. Input/output optical ports are factory-defined and follow the foundry’s interface constraints.
This layout shows a complete semiconductor laser architecture composed of sequential elements: SOA → phase control section → DBR reflector. All modules expose standard optical interface ports, and routing elements ensure optical mode continuity and low-loss coupling. The structure reflects an industrial PIC design flow where system-level circuits are built from reusable foundry-qualified blocks.
Two full MZI configurations are shown and connected via a waveguide. Each MZI includes input and output couplers (MMI or directional), controlled optical path-length difference via two parallel arms, and active tuning components (e.g., dcopm_dc). PDK textual identifiers embedded into the layout allow unambiguous tracking of configuration and fabrication attributes.
The final architecture contains two MZI stages interconnected by a straight optical link. The 2×2 MMI couplers provide phase-coherent splitting and recombination, while the active tuning elements allow phase modulation and calibration of interference output. Proper bend radii, core continuity, and spacing constraints ensure compliance with DemoFab design rules for fabrication.
This project enabled practical exploration of:
- optical routing rules including bend radius, spacing, and port alignment,
- hierarchical cell usage within a foundry-style PDK environment,
- integration of passive structures with active semiconductor photonic components.
The resulting designs trace a full progression from basic guided-wave structures to complex functional subsystems characteristic of modern integrated photonic circuits.