1. Polarization-Insensitive Cross Correlation Using Two-Photon Absorption in a Silicon Photodiode Pape Sylla

2. Cross-correlation in fiber optics Used for sampling, pattern recognition, demultiplexing So far, done using a nonlinear effect called sum-frequency generation which takes place in χ² crystals

3. Quick overview of nonlinearity We are use to linear material response of materials, which manifest itself in the index of refraction. There are nonlinear material response

4. Limitation of the existing method It is polarization dependant, which makes it unpractical for most application

5. Remediation: Two photon absorption They want to use a quantum nonlinear effect called two photon absorption (TPA) in silicon, which is χ³ susceptible. It is based of the fact that two photons are simultaneously absorbed by the material to produce current

6. Normalized Stokes vectors are located on a unit sphere Poincare’ sphere:

7. Observation: in Silicon, TPA is polarization dependent

8. In theory

9. Experiment

10. Results