[Phys-seminars] 2011-06-14 Lasers Seminar

ilana ibar at bgu.ac.il
Wed Jun 8 21:09:14 IDT 2011


ANNOUNCEMENT==> 

Lasers Seminar 

  DATE: 14-06-2011 

  TIME: 3:30pm (Tue) 

  PLACE: Physics building (#54) room 207 

TITLE: 
Focusing Ultrashort Pulses through Scattering Media 

SPEAKER: 
Mr. Ori Katz, Department of Physics of Complex Systems, Weizmann Institute
of Science, Rehovot 76100 

ABSTRACT/COMMENTS:
Light scattering in inhomogeneous media, such as biological tissues, 
induces wavefront distortions which limit effective focusing in many 
optical applications. Examples range from microscopy and nanosurgery 
to astronomy. In recent years, ongoing efforts in the field of 
adaptive optics have made the correction of spatial distortions 
possible by wavefront shaping techniques. However, when ultrashort 
pulses are employed scattering induces also temporal distortions 
which hinder their use in applications such as in multiphoton 
microscopy and quantum control experiments. I'll show how, quite 
surprisingly, the correction of both spatial and temporal distortions 
can be attained by manipulating only the spatial degrees of freedom 
of the incident wavefront, optimizing a nonlinear signal. Our results 
open up interesting new possibilities for optical manipulation and 
nonlinear imaging in scattering media.

 
Fig. 1: Spatiotemporal focusing and pulse compression by optimizing
two-photon 

fluorescence (2PF) [3]; (a) the experimental setup; optimization: an
ultrashort pulse 

is focused to a 2PF screen placed behind a scattering medium. An SLM
controls 

the incident wavefront, optimizing the 2PF at a selected point imaged by an
EMCCD, 

(F-band-pass filter). Spatiotemporal characterization: utilizing a Michelson
interferometer, 

spatially resolved autocorrelation is measured on the entire field
simultaneously by

imaging the 2PF at different delays, t. The pulse is pre-chirped by a
glass-slab to 

demonstrate temporal compression by spatial wavefront shaping. (b-c)

2PF images before (b) and after (c) optimization at the optimized plane.
(d-e) Maps of the 

temporal 1/e-width of the spatially resolved, background-subtracted
autocorrelation, 

before (d) and after (e) optimization, revealing the temporal pulse
compression around

the optimization point. (f) Measured fringe-averaged, background-subtracted
autocorrelation 

of the chirped input pulse (red, 1/e-width= 715fs), the non-optimized
scattered pulse (green, 

1/e-width=875fs), the optimized pulse (blue, 1/e-width=370fs), and the

transform-limited pulse (dashed-black, 1/e-width=230fs); scale-bars, 25μm;

 

References:

O.Katz, Y.Bromberg, E.Small, and Y.Silberberg, Nature Photonics
doi:10.1038/nphoton.2011.72 (2011).

 

 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.bgu.ac.il/pipermail/phys-seminars/attachments/20110608/37868d87/attachment.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image002.png
Type: image/png
Size: 135994 bytes
Desc: not available
URL: <http://lists.bgu.ac.il/pipermail/phys-seminars/attachments/20110608/37868d87/attachment.png>


More information about the Phys-seminars mailing list