Teng-Man Method

Teng-Man Method for Measuring Electro-optic coefficient

Teng-Man Testing configuration

The Teng - Man method can measure R₃₃ as the sample is being poled. R₃₃ is an elipsometric measurement. A poling voltage is applied to the film while making the elipsometric measurements and looking for changes in the AC signal generated by incident light. The stage can be heated until the film reaches its melting point T_g. These measurements are made with the materials in a device configuration. The formula for R₃₃

<math>r_{33}= \frac {3\lambda I_m } {4 \pi V_{poly}I_c n^2 } \frac {(n^2 - sin^2 \theta) ^{1/2}}{sin^2 \theta} \approx I_m/ I_c

\,\!</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>

Data from Teng-Mann measurement

The measured quanitities are:

<math>I= 2I_M\,\!</math> Modulated Intensity

<math>I_0 = 2I_C\,\!</math> Output intensity

<math>V_m = V_0 sin\omega t\,\!</math> Modulation Voltage

Real time optimization of r₃₃

Teng_Man techniques allows real-time optimization of processing conditions because you can evaluate r₃₃ during the poling process. It is used to confirm that a sample has been poled. The R33 measurement is best used as a relative measure because it can be inaccurate. Use attenuated total reflection ATR to get an accurate absolute measure.

See Khanarian 1996

See STC-MDITR research project 1.1

Technique

Part 1 Teng Man Setup

Part 2 Teng Man Measurement

In the prism coupling technique the sample is pressed between a prism and light pipe connected to a detector. The "wet spot" is the point where the light pipe is in perfect contact with the sample so they behave as a single unit.

References

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