1. Simulation Project Paper: Resolving the thermal challenges for
silicon microring resonator devices
MyungJin Shin

2. Outline Paper Summary Simulation Target Device Structure
Reducing Thermal Dependence
Device Structure
Simulation Result
Additional Simulation (Heater Simulation)
Conclusion

3. Resolution for Temperature Sensitivity
Reduce thermal dependence (athermal devices)
No additional active power
Difficult to fabricate
Laser source: fixed wavelength & laser stability throughout optical link
Actively maintain local temperature (control based circuit)
Typical control-based systems needed (heaters, PDs etc.)
Additional active power consumption
Laser source: no constraints are needed

4. Athermal Devices
Main idea: decrease temperature-dependence of the microring resonator
Negative thermo-optic coefficient(TOC) cladding
Compensating thermal sensitivity by MZM

5. Simulation Goal & Principle
Reduce temperature dependence using negative thermal-optic material
Effective index of waveguide
Γ: confinement factor for each materials

6. Using Negative Thermal-Optic Material
3 different negative TOC material
Polymer material for cladding
Temperature weakness, chemical instability
Hard to fabricate on CMOS-production cycle
Including photosensitive material with polymer to tune the TO after fabrication
TiO2 for cladding material
CMOS-compatible
2 different ways for temperature variation
Changing room temperature
Changing temperature by heater

7. Device Structure Waveguide width: 250nm ~ 450nm
Waveguide height: 250nm
Etch depth: 150nm ~250nm
TiO2 oxygen content: 12%
nTiO2: 2.42, TOC: x 10-4/k
Ref: Djordjevic SS, Shang K, Guan B, Cheung ST, Liao L, Basak J, Liu HF, Yoo SJ. CMOS-compatible, athermal silicon ring modulators clad with titanium dioxide. Opt Express 2013;21(12):

8. MODE Solution Simulation
New version of MODE Solution include n = nref + δn(t)
Thermal dependent material is added (Si, SiO2, TiO2)
Thermo-optic coefficient
Si: 1.8 x10-4(/K)
SiO2: 1x 10-5(/K)
TiO2(O2_12%): x10-4(/K)

9. Comparison Between SiO2 & TiO2
Room Temperature: 300 ~310K (interval: 0.5K)
Waveguide width: 250nm
Etch depth: 200nm
TiO2 Si
SiO2
SiO2 cladding
TiO2 cladding
1.34x10-4(/K)
-4.5x10-5(/K)

10. Different Etch Depth Waveguide width: 250nm Etch depth ↑  Γcore ↓
Etch depth: 150nm
Etch depth: 200nm
Etch depth: 250nm

11. Different Waveguide Width
Etch depth: 200nm
Waveguide width ↑  Γcore ↑
Width: 250nm
Width: 300nm
Width: 350nm

12. Heater Simulation Workflow

13. Temperature Distribution
300K ~ 310K (0.5K interval) at waveguide
2μm

14. Temperature Imported MODE Solution
Waveguide width: 250nm
Etch depth: 200nm
300K ~ 310K (0.5K interval) at waveguide
Upper cladding experience higher temperature variation compare to WG
 negative TiO2 TOC affects more than Si TOC

15. Summary Effective index variation is simulated with TiO2 cladding
Effective index variation is decided by TOC & Γ for each core & cladding
Optimized athermal waveguide with TiO2 (12% O2) cladding
Waveguide width: 300nm
Etch depth: 200nm
Location of heater can affect temperature dependence of effective index

16. Simulation Project Paper: Resolving the thermal challenges for
silicon microring resonator devices