Multiphoton spectroscopy

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					Multiphoton spectroscopy
           When light hits matter


incident light λ
        Shaking electrons




E               0
    r
Linear interactions
      reflection
                     Linear interactions
                         absorption




LUMO
(electronic state)




HOMO
(electronic state)
        Nonlinear response



               ?

E               0
    r
Nonlinear response
Second harmonic generation
Second harmonic generation




                

                         +
                
in quantum terms
Only special molecules
 Two-photon absorption



excited state




                fluorescence




ground state
        Need for pulses

power




              time
power




              time
Nonlinear microscopy
multiphoton fluorescence
General framework




Linear susceptibility: absorption, reflection, refraction


2nd order susceptibility: SHG, SFG


3rd order susceptibility: FWM, CARS, pump-probe
      Second order processes

SHG           SFG          PDC
      Higher order nonlinearities

FWM                 CARS            Photon echo




                    probe    as
          pump
                  Stokes


                       vib
                          CARS




          probe    as
pump
        Stokes


             vib
Photon echos
fiber nonlinear optics
Extreme nonlinear optics
         Extreme nonlinear optics




http://www.nature.com/nature/journal/v453/n7196/images/nature07012-f1.2.jpg

				
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