Abstract
The numerical simulations of nanogratings integrated with gallium nitride (GaN) planar waveguides as well as the experimental in-coupling results are presented. A simulation tool based on the eigenmode expansion method and advanced boundary conditions provided a rigorous model of 400-nm-period grating couplers. A full-vectorial Maxwell solver allowed performing a number of simulations with varying grating parameters, where coupling efficiency, reflection and transmission characteristics of device were calculated. Gratings with different etch depths and arbitrary shapes were simulated using a staircase approximation, with an optimized number of steps per single slope. For the first time, an impact of dry etch processing on GaN coupler efficiency was evaluated, due to the inclusion of the sloped sidewalls, with regard to the technological constrains. Finally, the experimental results in the visible spectrum region (λ = 633 nm), for 400-nm-deep gratings etched in GaN waveguide, were presented together with theoretical data for binary and trapezoidal profiles of a grating, for different optical mode profiles (\({{\rm TE}_{0}\div {\rm TE}_{3}\,{\rm modes}}\)).
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Abbreviations
- GaN:
-
Gallium nitride
- EEM:
-
Eigenmode expansion method
- PICs:
-
Photonic integrated circuits
- 2-D:
-
Two-dimensional
- LEDs:
-
Light emitting diodes
- CAMFR:
-
CAvity Modelling FRamework
- FDTD:
-
Finite difference time-domain
- PMLs:
-
Perfectly matched layers
- GPL:
-
General public license
- SOI:
-
Silicon-on-insulator
- LT:
-
Low-temperature
- MOCVD:
-
Metaloorganic chemical vapour deposition
- PECVD:
-
Plasma-enhanced chemical vapor deposited
- ff:
-
Filling factor
- SEM:
-
Scanning electron microscope
- ICP:
-
Inductively coupled plasma
- EBL:
-
Electron beam lithography
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Acknowledgments
This work was supported by Polish State Committee for Scientific Research during 2004–2007 under Grant 3 T11B 039 27. This work was supported in part by British Council Young Scientists Programme and EU Leonardo da Vinci Programme Future Engineers in Europe. CAMFR numerical calculations were performed at Wroclaw Centre for Networking and Supercomputing (WCSS), Wroclaw, Poland.
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Open Access This is an open access article distributed under the terms of the Creative Commons Attribution Noncommercial License (https://creativecommons.org/licenses/by-nc/2.0), which permits any noncommercial use, distribution, and reproduction in any medium, provided the original author(s) and source are credited.
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Dylewicz, R., Hogg, R.A., Airey, R. et al. Simulations of nanograting-assisted light coupling in GaN planar waveguide. Opt Quant Electron 42, 619–629 (2011). https://doi.org/10.1007/s11082-011-9485-4
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DOI: https://doi.org/10.1007/s11082-011-9485-4