1. Robustness of temporally focused pulses in scattering media E. Papagiakoumou 2, A. Begue 2, Ben Leshem 1, O. Schwartz 1, B. Stell 2, J.Bradley 2, V. Emiliani 2, D. Oron 1 1 Weizmann Institute of Science 2 Paris Descartes University

2. Optogenetics Controlling neurons using light!

3. 3-D confined 2- photon excitation Papagiakoumou et al. (2010). 3-D confinement is achieved using temporal focusing (TF) and generalized phase contrast (GPC) method.

4. What is temporal focusing? Time lens? Δt

5. Geometrical picture of TF f1 f2 f1 Image plane Grating In the image plane the pulse is of the original temporal length – Fermat principle! Geometrical separation of different colors causes temporal broadening. Dan Oron et al. Opt. Express (2005)

6. Grating Image plane Time lens

7. Temporal focusing with two-photon excitation Sample Image plane Imaging system Focusing in time replaces scanning in the x-y plane.

8. Focusing light patterns through scattering medium

9. Some properties of speckles

10. What happens when we use temporal focusing through scattering medium? Papagiakoumou et al. Accepted (2013) Two apparent effects – overall smoothening and anisotropic smoothening

11. Different colors propagate, effectively in different realizations of the random medium Image plane: Image plane Grating Focal plane

12. First effect: summing up speckle patterns of different colors results in overall smoothening Image plane: Reduces Contrast:

13. Second effect: summing adjacent colors results in x-direction smoothening Wider x-correlations:

14. Simulations

15. Wider x-correlation - Simulations

16. Contrast dependence on image size

17. Image patterns with and without temporal focusing Papagiakoumou et al. Accepted (2013)

18. Measurement of the action potential

19. Photo-activation deep inside brain tissue Papagiakoumou et al. Accepted (2013)

20. Thank you! E. Papagiakoumou 2, A. Begue 2, B.Leshem 1, O. Schwartz 1, B. Stell 2, J.Bradley 2, V. Emiliani 2, D. Oron 1 “Functional patterned multiphoton excitation deep inside scattering tissue”. Nature photonics. Accepted. 1 Weizmann Institute of Science 2 Paris Descartes University