Difference between revisions of "Second-order Material Characterization"

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β, the first nonlinear polarizability depends on molecular structure, environment and measurement frequency. There are several tools that help us characterize the materials.
β, the first nonlinear polarizability depends on molecular structure, environment and measurement frequency. There are several tools that help us characterize the materials.


=== Hyper Rayleigh Scattering (HRS) ===
[[Hyper Rayleigh Scattering]]
 
Hyper Rayleigh Scattering (aka Harmonic Light Scattering) is one method for measuring β.
 
[[Image:Hrs.png|thumb|300px|The Hyper Rayleigh Scattering - Test best schematic]]
 
An incident laser generates a second harmonic signal, specifically the frequency double signal. This can be related to the beta of the sample using this formula:
 
:<math>\frac {I_{sample}} {I_{solvent}} =  \frac {N_{sample} \langle \beta^2 _{sample} \rangle  + N_{solvent} \langle \beta^2_{solvent}\rangle}  {N_{solvent} \langle \beta^2_{solvent}\rangle}\,\!</math>
 
[[Image:Tcp1_chcl3.png|thumb|300px|HRS spectrum for 1.5 &mu;m TCP1 in CHCl<sub>3</sub>]]
 
See Firestone 2004 <ref>K. A. Firestone, P. Reid, R. Lawson, S. H. Jang, and L. R. Dalton, “Advances in Organic Electro-Optic Materials and Processing,” Inorg. Chem. Acta, 357, 3957-66 (2004)</ref>.
 
 
 
See also [[Density Functional Theory]]
<br clear='all'>
 
=== Electro-optic coefficient measurements ===
[[Image:Tang_mann_r33.png|thumb|400px|Teng-Man Testing configuration]]
We use the Teng - Man method to measure R<sub>33</sub>.
R<sub>33</sub> is an elipsometric measurement. You apply a voltage to the film while making the elipsometric measurements and looking for changes in the signal. You have to be careful with the kind of glass and the kind of tin oxide that is used. These measurements are made with the materials in a device configuration. The formula for R<sub>33</sub>
 
:<math>r_{33}= \frac {3\lambda I_m (n^2 - sin^2 \theta) ^{1/2}} {4 \pi V_{poly}I_c n^2 sin^2 \theta}
\,\!</math>
where
 
:<math>I_m\,\!</math> is the amplitude of modulation
:<math>V_{poly}\,\!</math> is the modulation voltage across EO polymer
:<math>I_c\,\!</math> is the half intensity point
:<math>n\,\!</math> is the refractive index of the polymer
 
and
 
:<math>V_{poly}= V_{ACtot}  \frac {d_{poly}}  {d_{poly} + d_{clad}}  \cdot \sqrt {\frac {\epsilon_{clad}} {\epsilon _{poly}}}\,\!</math>
 
 
 
See Khanarian 1996 <ref>Khanarian, et. al., JOSA B13, 1927 (1996)</ref>
 
See STC-MDITR research project 1.1 [http://stc-mditr.org/research/oeoaomd/projects/1.111.cfm Measuring R33 with Interferometry]


[[Teng-Mann Method]]


[[Attenuated_Total_Reflectance]]
[[category:second order NLO]]
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Latest revision as of 11:01, 9 August 2010

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Characterization

β, the first nonlinear polarizability depends on molecular structure, environment and measurement frequency. There are several tools that help us characterize the materials.

Hyper Rayleigh Scattering

Teng-Mann Method

Attenuated_Total_Reflectance

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