J. Eur. Opt. Society-Rapid Publ. 21, 34( 2025) 43
Fig. 5.( a) Far-field Intensity in terms of angle and wavelength.( b) Transmittance curves at different directions of the structure.
a line located at 1 lm above the grating. The sum corresponds then to the far field intensity.
g TOT ¼
Z L
0
Transmitted intensity at y ¼ 1 lm |
|
|
Z h |
; |
ð6Þ |
Input intensity |
|
|
0
where L is the total length of the grating and h the height of the SiGe guiding layer. The out-coupling efficiency through this long grating is 75 %. The electric field amplitude at 12 lm from the grating surface can be seen from Figure 4b.
The design considers the targeted broadband operation of the device. A variation in wavelength implies a variation in the output angle and in efficiency. Figure 5a shows the far-field intensity as a function of the wavelength and its angle dependence.
The transmission as a function of the wavelength along three characteristic locations of the structure, i. e., above the grating, under the grating, at the waveguide output, can be observed in Figure 5b.
4 Conclusion
We have presented the design and expected properties of a novel vertical grating coupler on thick SOI platform and operating in the telecom C-band. Such a structure is enabled by the use of high refractive index material, i. e., SiGe, deposited on the top side of the waveguide at the selected places for out-coupling. The SiGe layer pulls the mode upwards for an increased overlap of light with grating leading to a better control of the out-coupling efficiency and therefore a control shape of the output beam. The length of the grating is 500 lm and the extraction efficiency is 75 % at the top side of the grating. Such a grating is intended to be performed on the output waveguides of integrated LiDAR for two-dimensional beam steering.
Funding
We would like to acknowledge Research Council of Finland Flagship for Photonics Research and Innovation( PREIN) for funding this based on the lLiDAR applications( funding decisions 346518 and 346545).
Conflicts of interest The authors declare no conflicts of interest.
Data availability statement
Data underlying the results presented in this paper are not publicly available at this time but may be obtained from the authors upon reasonable request.
Author contribution statement
Conceptualization, Matteo, Timo; Design, Sidra, Matteo, Matthieu; Software and simulations, Sidra, Isaac; Analysis, Sidra; Writing, Original Draft Preparation, Sidra; Writing, Review & Editing, Timo and Matthieu; Supervision, Matteo, Timo, and Matthieu.
References
1 Leuthold J, Koos C, Freude W, Nonlinear silicon photonics, Nat. Photonics 4, 535( 2010). https:// doi. org / 10.1038 / nphoton. 2010.185.
2 Zhou X, Yi D, Chan DWU, Tsang HK, Silicon photonics for high-speed communications and photonic signal processing, npj Nanophotonics 1, 27( 2024). https:// doi. org / 10.1038 / s44310-024-00024-7. 3 Baehr-Jones T, et al., Silicon-on-sapphire integrated waveguides for the mid-infrared, Opt. Express 18, 12127( 2010). https:// doi. org / 10.1364 / OE. 18.012127. 4 Geppert T, Schilling J, Wehrspohn R, Gösele U, Siliconbased photonic crystals, Topics Appl. Phys. 94, 295( 2004). https:// doi. org / 10.1007 / 978-3-540-39913-1 _ 9. 5 Leheny RF, Optoelectronic integrated circuits, in International Technical Digest on Electron Devices,( IEEE, 1990), p. 7. https:// doi. org / 10.1109 / IEDM. 1990.237238.
6 Xu C, Liu C, Ding Y, Wang R, Wu A, FMCW LiDAR with a coherent receiver chip based on 3 lm SOI photonics platform, Results Phys. 57, 107327( 2024). https:// doi. org / 10.1016 / j. rinp. 2024.107327.
7 Reed G, in Optical interconnects. Springer Series in Optical Sciences, vol. 119, edited by L. Pavesi, G. Gerard( Springer, Berlin, Heidelberg, 2007), p. 161 – 203. https:// doi. org / 10.1007 / 978-3-540-28912-8 _ 7.
8 Rahim A, Spuesens T, Baets R, Bogaerts W, Open-access silicon photonics: current status and emerging initiatives, Proc. IEEE 106, 2313( 2018). https:// doi. org / 10.1109 / JPROC. 2018.2878686.