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High-efficiency apodized-imaging chip-fiber grating coupler for silicon nitride waveguides
Optics Letters
|November 3, 2016
Summary
This study introduces an advanced silicon nitride grating coupler for improved optical fiber coupling. It achieves a record 86% efficiency, overcoming limitations in silicon nitride waveguides.
Area of Science:
- Photonics
- Materials Science
- Optical Engineering
Background:
- Chip-fiber grating couplers are crucial for optical interconnects.
- Silicon nitride waveguides face challenges with lower index contrast, impacting coupling efficiency and directionality.
Purpose of the Study:
- To propose and design an apodized self-imaging grating coupler in silicon nitride.
- To enhance coupling efficiency and directionality for in-plane waveguide to fiber coupling.
Main Methods:
- Utilizing amplitude and phase apodization to engineer the grating's transfer function.
- Employing two-step etch staircase grating teeth for improved directionality.
- Performing 3D finite-difference time-domain (FDTD) simulations for performance analysis.
Main Results:
- Achieved a directionality of 93% using staircase grating teeth.
- Demonstrated a record calculated coupling efficiency of 86% (0.66 dB loss) to an SMF-28 fiber.
- Obtained a 3 dB bandwidth of 40 nm near 1550 nm wavelength.
Conclusions:
- The proposed apodized self-imaging grating coupler significantly enhances performance in silicon nitride photonic integrated circuits.
- This design overcomes previous limitations, offering a pathway to higher efficiency optical fiber coupling.
