Fabrication-Tolerant Non-Linear Waveguide Taper Design
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Solution Overview
Problem
Existing optical waveguide transitions in photonic integrated circuits face challenges in achieving low-loss, compact transitions between silicon and III-V waveguides, particularly due to scattering losses associated with higher-order mode excitation.
Innovation Solution
The design and fabrication of non-linear waveguide tapers, where the taper profile is computed based on the envelope of width-dependent scattering rates for multiple sets of design parameter values, including process corners, to optimize the trade-off between taper length and scattering losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the taper length is increased to reduce scattering losses, then optical transmission is improved, but the device size increases and compactness is lost
Solution Approach 1:
The patent applies parameter changes by transitioning from a linear taper profile to a non-linear taper profile. Specifically, the waveguide width is varied according to a non-linear function of position along the taper, allowing the taper to achieve steeper transitions in certain regions and gentler transitions in others. This non-linear parameter variation enables reduced scattering losses through optimized mode coupling while maintaining a more compact overall length compared to conventional linear tapers.
2Length of moving object
If the taper length is decreased to achieve compactness, then device size is reduced, but scattering losses increase
Solution Approach 1:
The patent employs non-linear parameter changes in the taper profile to achieve compactness without sacrificing optical transmission. By using a non-linear width variation function, the design can pack the tapering function into a shorter distance while maintaining effective mode coupling. The non-linear profile allows for optimized distribution of the tapering effect along the shortened length, reducing scattering losses that would otherwise occur in compact designs.
3Ease of manufacture
If a linear taper profile is used for simplicity, then manufacturing is easier, but optical transmission is suboptimal compared to non-linear profiles
Solution Approach 1:
The patent implements non-linear parameter changes in the taper profile to optimize optical transmission. The waveguide width is defined as a non-linear function of position along the taper axis, allowing for optimized mode coupling and reduced scattering losses. While more complex than linear tapers, the non-linear profile can be implemented using standard photolithographic techniques by appropriately designing the mask patterns and etching processes, achieving superior optical performance with acceptable manufacturing complexity.
Data Source
Figure 1A
Figure 1B
Figure 1C~1D
AI summary
A fabrication-tolerant non-linear waveguide taper for a waveguide transition can be designed by computing the scattering rate associated with the waveguide transition as a function of waveguide width of the waveguide taper for each of multiple sets of parameter values characterizing the waveguide transition (e.g., a set of nominal parameter values and sets of parameter values associated with process corners representing process variations from the nominal parameter values), determining an envelope of the computed width-dependent scattering rates, and computing a non-linear taper profile of the waveguide taper based on the envelope. Light propagation and coupling along the waveguide transition may further be computationally simulated for the multiple sets of parameter values to determine a minimum transmission value associated with the waveguide transition for a specified taper length, and/or to determine a minimum taper length at which the transmission values associated with the waveguide transition exceed a specified threshold transmission value.