Download - Dillon Walker
Dillon Walker, Guangyao Li, Ken Singer
Hyper-Rayleigh Scattering
NSF Grant DMR-0850037
IntroductionFiber-optic cables in data transmission
(internet)Need to switch light quickly Nonlinear optical process
Introduction to Nonlinear OpticsNonlinear Effects in All MaterialsSelf-interaction of wave through matterNeed strong coherent light to observeLaser is only good light sourceMode-locked Ti:Sa used in my experiment
Hyper-Rayleigh ScatteringTechnique for measuring second term in
Third Order TensorRequires non-centrosymmetric moleculesFrequency doubles
NN
OO
O
SO
O
O
Chromo1
Hyper-Rayleigh Scattering
Material dissolved in solutionSolutions are symmetricSome incoherent scatteringCollected at 90 degreesVery weak signal
Multi-Photon Fluorescence
Photon energy may be absorbed by electronPhotons released as electron returns to ground
stateMay have same wavelength as Hyper-Rayleigh
400 600 8000.0
0.5
1.0
Ab
so
rb
an
ce
Wavelength (nm)
1
Fluorescence versus Hyper Rayleigh
Hyper Rayleigh Signal
Competing Multi-photon Fluorescence
Instantaneous
Non-Instantaneous
Single Photon Counting Technique
Fluorescence is not instantaneous
Time-Resolved Single Photon Counting can be used to distinguish between the two
Requires thousands of pulses for accuracy
Single-Photon Counting TechniqueSingle-Photon detectors have a dead time
after each photon detection.Can use sync to build a histogram of
photon detections after each pulseOnly works for low detection probabilities
2% Chromophore1 in Acetone
Setup
Photomultiplier
PC
Photo-detector
Sample
Beam-splitter
Titanium: Sapphire
Pump Laser