FWM IN SILICON NANOWIRE & MULTICORE FIBER COUPLING Kéven Bédard (keven.bedard.2@ulaval.ca) Benoît Filion (benoit.filion.2@ulaval.ca) Université Laval

Four-Wave Mixing Wavelength conversion technique : modulation format transparency. A strong pump at ω0 and a weaker signal at ω1 = ω0 – Ω are injected at the input of the nonlinear medium. A new optical field is generated at ω2 = ω0 + Ω through the third-order polarization term : 𝑃 𝑡 ∝ 𝜒 1 𝐸 𝑡 + 𝜒 2 𝐸2 𝑡 + 𝜒 3 𝐸3 𝑡 +… Ω NL Medium Pump Signal Idler ω1 ω2 ω0

FWM in Silicon Nanowires The high index contrast of SOI waveguides allows for a tight confinement inside the waveguide. SOI waveguides exhibit larger third-order nonlinearity than that of an optical fiber. The dispersion of the SOI waveguides is mostly governed by its shape and dimensions : dispersion can be engineered to get a large conversion bandwidth.

Design Challenges Conversion efficiency (CE) FWM conversion bandwidth → CE = Idler output / Signal input → Must be as high as possible over a wide wavelength conversion range → The efficiency is tightly related to the effective mode area of the waveguide. FWM conversion bandwidth → Phase-matching condition : dispersion engineering → Single mode or multimode waveguide? Polarization diversity ?

Dispersion Engineering 𝜅 z =Δβ 𝜔 0 , 𝜔 1 , 𝜔 2 +2γ𝑃 𝑝 𝑒 (− 𝛼+ 𝛼 𝑓𝑐𝑎 𝑧) The phase mismatched is dependent on the linear loss (𝛼) and the free carrier absorption induced loss ( 𝛼 𝑓𝑐𝑎 ). Single mode operation in a multimode waveguide? Waveguide Dispersion Phase-Mismatch Condition Input Powers Conversion Efficiency Conversion Bandwidth linear phase-mismatch non-linear phase-mismatch The conversion efficiency and bandwidth are dominated by the phase-mismatched condition, which is determined by the dispersion of the SOI waveguide and the input pump powers.

FWM conversion Bandwidth Etched Waveguide 700nm x 220nm Pump at 1550nm

Polarization Diversity ? Figure from Lukas presentation!!!

Multicore fiber coupling Figures from: Silicon Photonics Core-, Wavelength-, and Polarization-Diversity Receiver, C. R. Doerr and T. F. Taunay, IEEE Photonics Technology Letters, Vol. 23, No. 9, May 1, 2011

Vertical grating coupler Figures from: Fabrication-Tolerant Waveguide Chirped Grating Coupler for Coupling to a Perfectly Vertical Optical Fiber, Xia Chen, Chao Li, and Hon Ki Tsang, IEEE Photonics Technology Letters, Vol. 20, No. 23, December 1, 2008

Thank you!