Polarization-Insensitive Cross Correlation Using Two-Photon Absorption in a Silicon Photodiode

Pape Sylla

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

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

Limitation of the existing method It is polarization dependant, which makes it

unpractical for most application

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

Normalized Stokes vectors are located on a unit sphere

11

0

Ss

S 2

20

Ss

S 3

30

Ss

S

Poincare’ sphere:

2 2 21 2 2

0

S S SDOP

S

Observation: in Silicon, TPA is polarization dependent

In theory

Experiment

Results