Solutions | Photonics
This is the platform you choose where loss itself is a design variable. Propagation loss is dominated by scattering from sidewall roughness, so it is taken from measurement, while resonator geometry, coupling conditions, dispersion and the effect on the circuit are settled by analysis.
Design challenges
Long delay lines, high-Q resonators, narrow-linewidth external cavities. Loss is the reason to choose SiN. But the sidewall roughness scattering that sets propagation loss depends heavily on the process and is hard to obtain accurately by analysis. Take loss from measurement, and settle index, group index, dispersion and resonance conditions by analysis. Fixing that division of labor first is the starting point for the design.
Design and simulation workflow
Settle the core and cladding dimensions and solve the guided modes.
Take propagation loss from measurement and fill in index and dispersion by analysis.
Evaluate bend loss and mode mismatch loss separately, and settle the bend radius.
Match the ring geometry and coupling gap to the target free spectral range and Q.
Evaluate third-order nonlinear behavior such as four-wave mixing in the resonator.
Assemble the low-loss circuit and confirm system-level effects such as an external cavity.
The stages differ by project. If you already have measured waveguide data, you can start from there.
Related analysis technologies
The principles and scope of each method are explained on the Analysis Technologies pages.
Related products
The capabilities and coverage of each product are described on its own product page.
Handles waveguide, bend and planar propagation design. FDE, EME and varFDTD are used according to the structure.
Stage / 01-03
Handles rigorous analysis of the resonator. Three-dimensional FDTD gives the coupling gap, free spectral range and Q.
Stage / 04
Handles incorporating the loss data. Measured propagation loss is carried into the model and passed to circuit analysis.
Stage / 02
Handles circuit and nonlinear evaluation. The low-loss circuit is assembled and third-order nonlinear behavior such as four-wave mixing is confirmed.
Stage / 05-06
Foundry and manufacturing
Because propagation loss is dominated by sidewall roughness scattering, the loss figure a design assumes is tied to the process. Before moving to prototyping, confirm that the conditions of the target silicon nitride process match the loss and dimensional assumptions the design has made.
Which processes and prototyping routes are available is judged case by case from the target film thickness and dimensional conditions.
Related technical information
Tell us where the design stands, whether you have measured loss, your target free spectral range and Q, and any prototyping planned, and we will propose a way forward.