A novel electro‐optic effect has been observed in thin homeotropic nematic layers. Electrodes, such as a pair of parallel lines, are located on a planar surface in contact with the liquid. Deformation of the homeotropic ordering occurs when the applied field exceeds a threshold strength. Induced optical birefringence and diffraction have been observed, and electrically controlled optical transmission and reflection have been attained. Experimental data are given for a cyano‐aniline mixture with ε − ε > 0 and for negative‐anisotropy materials.

1.
R. A.
Soref
and
M. J.
Rafuse
,
J. Appl. Phys.
43
,
2029
(
1972
).
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M.
Hareng
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G.
Assouline
, and
E.
Leiba
,
Proc. IEEE
60
,
914
(
1972
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3.
“Positive” means Δε>0, and “negative” means Δε<0, where Δε is the dielectric anisotropy Δε = ε−ε.
4.
The surfaces were prepared as in Ref. 1.
5.
We use the notation of F. J. Kahn in which d is the nematic sample director, z is the normal to the sample plates, E is the applied field in the liquid, and d0 is the orientation of d at E = 0.
6.
M.
Schadt
and
W.
Helfrich
,
Appl. Phys. Lett.
18
,
127
(
1971
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M.
Schadt
,
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56
,
1494
(
1972
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8.
Synthesized by M. J. Rafuse of our laboratory.
9.
Eastman organic chemical No. 11 643.
10.
These small d values were measured using a Babinet‐Soleil compensator and a homeotropic sample (same nematic) of known thickness, e.g., 25 μm. The known sample is tilted between crossed polarizers and the induced δ determined with the compensator. The δ‐vs‐tilt measurement is repeated with the unknown (d′) sample. Then the phase comparison d′/d = δ′/δ is used.
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