Liquid crystal electro-optic modulator in a fabry-perot interferometer
First Claim
1. An electro-optic modulator including a Fabry-Perot etalon containing intra-cavity liquid crystal material and biasing means for applying a bias voltage to the material, the bias voltage being variable between two values both of which are above an etalon threshold voltage VT above which the liquid crystal material refractive index is sensitive to electrical bias.
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Abstract
An electro-optic modulator consists of a Fabry-Perot etalon containing intra-cavity liquid crystal material between mirror layers. Each mirror bears a respective rubbed polyimide layer, which provides homogeneous alignment of the liquid crystal molecules. The mirror layers are connected to a bias voltage source, which provide an electrical bias variable between two values both above the threshold for refractive index sensitivity to applied voltage. For nematic materials, this is the Freedricks threshold or transition. The bias variation provides optical modulation of the etalon transmission with a time constant which is much shorter than devices switching between voltages either side of the threshold.
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Citations
10 Claims
- 1. An electro-optic modulator including a Fabry-Perot etalon containing intra-cavity liquid crystal material and biasing means for applying a bias voltage to the material, the bias voltage being variable between two values both of which are above an etalon threshold voltage VT above which the liquid crystal material refractive index is sensitive to electrical bias.
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10. A method of obtaining optical modulation including the steps of:
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(1) providing a Fabry-Perot etalon containing intra-cavity liquid crystal material and bias electrodes arranged to bias the material, (2) passing light through the etalon cavity, the light having an intensity below that at which optical bistability would occur in the liquid crystal material, and (3) applying bias voltage to the bias electrodes, the bias voltage being variable between two values both of which are above an etalon threshold voltage above which the liquid crystal material refractive index is sensitive to electrical bias.
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Specification