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Silicon Photonic 2 X 2 Power
Splitter with S-Bend Configuration
Erica C. Graham1*, Nicholas M. Fahrenkopf 2 Nathaniel C. Cady2
1Colleges of Nanoscale Science and Engineering, University at Albany (SUNY), Albany, NY, USA2Colleges of Nanoscale Science and Engineering, SUNY Polytechnic Institute, Albany, NY, USA
Outline
❑Introduction❑What is Si Photonics
❑Si Photonic Components
❑Power Splitters
❑Simulation Set-Up
❑Results❑Variation of coupling length
❑Variation of coupling gap
❑Lumerical Mode Solutions comparison
❑Summary/ Future Works
October 3rd, 2019
Introduction
ELECTRICAL
TRADITIONAL PHOTONICS
October 3rd, 2019 [1] Liehr, Michael. 16 Nov. 2017, Albany.
❑Utilizes semiconductor infrastructure and supply chain
❑Delivers low cost solutions ❑Applications:
❑Performance Computing❑Data Centers❑Defense❑Life Sciences
[1]
3.
Si Photonic Components
October 3rd, 2019
❑ High refractive index contrast ❑ Low loss propagation❑ Light confinement❑ Compact footprint❑ Small bend radii
[1] “Intel® Silicon Photonics.” Intel, http://www.intel.com/content/www/us/en/ architecture-and -technology/silicon-photonics/silicon-photonics-overview.html. 4.
Electrical
Logic Cell
Electrical
Logic Cell
Driver Amplifier
Modulator Optical InterconnectPhoto
detector
Transmitter Receiver
Electrical Components
Optical Components
IC Chip IC Chip
Driver Amplifier
Modulator WaveguideLaserPhoto-
detector
Photonic Link
Laser
Laser
Laser
Laser
LASER: Light Amplification by Stimulated Emission of RadiationIC Chip: Integrated Circuit Chip
Waveguides
October 3rd, 2019
gc
lc
Input port
Cross port
S-bends
Through port
S-bends
Input port
Top-down view
SiO2 Cladding
400 nm 400 nm
220 nm
gcSi Core Si Core
Waveguide 1 Waveguide 2
Cross-section view
BOX
Si Substrate
❑Design Parameters:❑Coupling Gap (gc): separation distance between waveguides❑Coupling Length (lc): length of the parallel coupling region❑S-bends: compact footprint and controlling coupling region
5.
❑Objective❑Validate COMSOL’s ability to reproduce results from
Lumerical Mode®, a popular optical modeling software❑Parametric sweep of lc and gc❑Compare power splitting ratio
Modeling of Power Splitter
October 3rd, 2019
❑Wave Optics Module
❑Electomagnetic Waves,
Beam Envelope (ewbe)
❑Model Solutions
❑ 2.5D varFDTD (Finite
Difference Time
Domain)
6.
❑Wavelength Dispersion
❑Port Excitation ❑TE Mode propagation
❑Unidirectional
Model Set-Up: Boundary Conditions
October 3rd, 2019
Power Input
Scattering Boundary
Power Through
Power Cross
Port Boundary
7.
Model Set-Up: Meshing
October 3rd, 2019
❑Max mesh element size must be a fraction of a wavelength❑Max: 0.4 um
Fine transition region meshLower curvature factor:0.3
Large # of edge elements
8.
E-field Coupling Gap (gc)
October 3rd, 2019
❑ Normalized E-field profiles @1550 nm:
❑ Parametric sweep from 0.1 um to 0.4 um
gc: 0.3 um
gc: 0.2 umgc: 0.4 um
gc: 0.1 um
9.
Power Splitting Separation Gap (gc)
October 3rd, 2019
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.5 1.52 1.54 1.56 1.58 1.6
Through g=0.4 um Cross g=0.4 um
Through g= 0.3 um Cross g= 0.3 um
Through g=0.2 um Cross g=0.2 um
Through g=0.1 um Cross g=0.1 um
Po
wer
Sp
litt
ing
Ra
tio
Wavelength (um)
Waveguide Gap vs Wavelength
𝑃𝑡ℎ𝑟𝑜𝑢𝑔ℎ
𝑃𝑡ℎ𝑟𝑜𝑢𝑔ℎ + 𝑃𝑐𝑟𝑜𝑠𝑠
Through Port:
𝑃𝑐𝑟𝑜𝑠𝑠𝑃𝑡ℎ𝑟𝑜𝑢𝑔ℎ + 𝑃𝑐𝑟𝑜𝑠𝑠
Cross Port:
10.
COMSOL & Lumerical Comparison
October 3rd, 2019
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0.1 0.15 0.2 0.25 0.3 0.35 0.4
Po
we
r S
pli
ttin
g R
ati
o
Gap (um)
Comsol: Through
Comsol: Cross
Lumerical: Through
Lumerical: Cross
Coupling Gap
(um)
COMSOL
Multiphysics®
Lumerical
Mode
Solutions®
Through Port
0.1 0.711 0.684
0.2 0.481 0.2937
0.3 0.935 0.829
0.4 0.993 0.966
Cross Port
0.1 0.288 0.314
0.2 0.519 0.704
0.3 0.065 0.170
0.4 0.007 0.033
COMSOL vs Lumerical: Separation Gap
* 1550 nm wavelength
11.
~0.12 um ~0.2 um ~0.24 um
~0.15um
~0.4 um
E-field Coupling Length (lc)
October 3rd, 2019
❑ Normalized E-field profiles @1550 nm:
❑ Parametric sweep from 0 um to 30 um
lc: 10 um
lc: 20 umlc: 0 um
gc: 30 um
12.
Power Splitting Coupling Length (lc)
October 3rd, 2019
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.5 1.52 1.54 1.56 1.58 1.6
Through l = 0 um Cross l=0 um
Through l= 10 um Cross l = 10 um
Through l = 20 um Cross l = 20 um
Through l = 30 um Cross l = 30 um
Po
wer
Sp
litt
ing
Ra
tio
Wavelength (um)
Coupling Length vs Wavelength
𝑃𝑡ℎ𝑟𝑜𝑢𝑔ℎ
𝑃𝑡ℎ𝑟𝑜𝑢𝑔ℎ + 𝑃𝑐𝑟𝑜𝑠𝑠
Through Port:
𝑃𝑐𝑟𝑜𝑠𝑠𝑃𝑡ℎ𝑟𝑜𝑢𝑔ℎ + 𝑃𝑐𝑟𝑜𝑠𝑠
Cross Port:
13.
COMSOL & Lumerical Comparison
October 3rd, 2019
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 5 10 15 20 25 30
Po
we
r S
plitt
ing
Rati
o
Length (um)
Comsol: Through
Comsol: Cross
Lumerical: Through
Lumerical: Cross
Coupling
Length (um)
COMSOL
Multiphysics®
Lumerical
Mode
Solutions®
Through Port
0 0.995 0.993
10 0.897 0.903
20 0.734 0.718
30 0.538 0.482
Cross Port
0 0.004 0.005
10 0.102 0.096
20 0.266 0.280
30 0.461 0.514
COMSOL vs Lumerical: Coupling Length
* 1550 nm wavelength
14.
~30 um
❑Simulations show results from COMSOL and Lumerical are in good agreement
❑Characterize stress induced fabrication shifts
❑Couple Structural Mechanics Module❑Solid Mechanics Interface
❑Fabrication using 300mm wafer processing facility
Through-Oxide-Via (TOV)
15.
Summary/ Future Work
References
16.
[1] Z. Lu et al., “Broadband silicon photonic directional coupler using asymmetric-waveguide based phase control,” (eng), Optics express, vol. 23, no. 3, pp. 3795–3806, 2015.
[2] R. K. Gupta, S. Chandran, and B. K. Das, “Wavelength-Independent Directional Couplers for Integrated Silicon Photonics,” J. LightwaveTechnol., vol. 35, no. 22, pp. 4916–4923, 2017.
[3] G. F. R. Chen et al., “Broadband Silicon-On-Insulator directional couplers using a combination of straight and curved waveguide sections,” (eng), Scientific reports, vol. 7, no. 1, p. 7246, 2017.
[4] COMSOL Multiphysics, "The Wave Optics User's Guide", 2019
[5] Lumerical Solutions," Stress and Strain", 2019.
Acknowledgments
❑Nicholas Fahenkopf, Ph.D. (Co-Advisor)❑Nathaniel Cady, Ph.D. (Co-Advisor)❑Douglas Coolbaugh, Ph.D. ❑Eng Wen Ong, Ph.D. ❑COMSOL Technical Support
October 3rd, 2019
