EP0260073A2
Expired / Lapsed
EP
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A method of obtaining optical modulation
Assignee: UK Secretary of State for Defence
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Filing: 1987-09-04
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Granted: —
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Expires: 2007-09-04
Abstract
Abstract An electro-optic modulator consists of a Fabry-Perot etalon (10) containing intra-cavity liquid crystal material (12) between mirror layers (16). Each mirror (16) bears a respective rubbed polyimide layer (18), which provides homogeneous alignment (20) of the liquid crystal molecules. The mirror layers (16) are connected to a bias voltage source (24), 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.
Inventors
- 👤 Frances Carolyn Saunders
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-06 06:05
CPC Classifications
G; G02; G02F; G02F1/00; G02F1/01; G02F1/21; G02F1/216; G02F1/13; G02F1/137; G02F1/139; G02F1/1393; G02F1/1396; G02F1/1397; G02F1/141; G02F2203/00; G02F2203/05; G02F2203/055
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
69 words
An electro-optic modulator comprising a Fabry-Perot etalon (10) containing intra-cavity liquid crystal material (12) and biassing means (16,22,24) for applying a bias voltage to the material (12), characterised in that the biassing means (16,22,24) is arranged to apply a bias voltage variable between two values both of which are above an etalon threshold voltage V T above which the liquid crystal material refractive index is sensitive to electrical bias.
Claim 2
Dependent Claim
69 words
An electro-optic modulator comprising a Fabry-Perot etalon (10) containing intra-cavity liquid crystal material (12) and biassing means (16,22,24) for applying a bias voltage to the material (12), characterised in that the biassing means (16,22,24) is arranged to apply a bias voltage variable between two values both of which are above an etalon threshold voltage V T above which the liquid crystal material refractive index is sensitive to electrical bias.
Claim 3
Dependent Claim
49 words
A modulator according to Claim 1 characterised in that the biassing means (16,22,24) is arranged to apply a bias voltage variable between two values both of which are in the range 2V T to 20V T , and between which the etalon (10) exhibits a monotonically changing optical transmission.
Claim 4
Dependent Claim
27 words
A modulator according to Claim 2 characterised in that the bias voltage is variable between two voltages both in the range 5V T to 10V T .
Claim 5
Dependent Claim
25 words
A modulator according to Claim 2 or 3 characterised in that the etalon (10) has a cavity width in the range 5 to 20 microns.
Claim 6
Dependent Claim
29 words
A modulator according to Claim 4 characterised in that the liquid crystal material (12) is nematic with positive dielectric anisotropy and homogeneous alignment relative to internal etalon walls (18).
Claim 7
Dependent Claim
41 words
A modulator according to Claim 4 characterised in that the liquid crystal material (12) has negative dielectric anisotropy and a tilted homeotropic alignment inclined to the perpendicular to internal etalon walls (18) at an angle in the range 2° to 10°.
Claim 8
Dependent Claim
29 words
A modulator according to Claim 4 characterised in that the liquid crystal material (12) has a positive dielectric anisotropy and hybrid molecular alignment relative to internal etalon walls (18).
Claim 9
Dependent Claim
24 words
A modulator according to Claim 4 characterised in that the liquid crystal material (12) has a positive dielectric anisotropy and a π-cell alignment twist.
Claim 10
Dependent Claim
22 words
A modulator according to Claim 4 characterised in that the liquid crystal material (12) has low birefringence and a 2π alignment twist.
Claim 11
Dependent Claim
36 words
A modulator according to Claim 2 or 3 characterised in that the etalon (10) has a cavity width in the range 1 to 6 microns and liquid crystal material is a ferroelectric smectic with homogeneous alignment.
Claim 12
Independent Claim
97 words
A method of obtaining optical modulation including the steps of: (a) providing a Fabry-Perot etalon (10) containing intra-cavity liquid crystal material (12) and bias electrodes (16) arranged to bias the material (12), (b) passing light (26) through the etalon (10), (c) applying bias voltage to the electrodes (16), characterised in that the light (26) has insufficient intensity to cause optical bistability in the material (12) and the bias voltage is varied between two values both of which are above an etalon threshold voltage above which the refractive index of the material (12) is sensitive to electrical bias.
Claim 13
Independent Claim
97 words
A method of obtaining optical modulation including the steps of: (a) providing a Fabry-Perot etalon (10) containing intra-cavity liquid crystal material (12) and bias electrodes (16) arranged to bias the material (12), (b) passing light (26) through the etalon (10), (c) applying bias voltage to the electrodes (16), characterised in that the light (26) has insufficient intensity to cause optical bistability in the material (12) and the bias voltage is varied between two values both of which are above an etalon threshold voltage above which the refractive index of the material (12) is sensitive to electrical bias.
References Cited (Backward Citations)
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