Optical switches using cholesteric or chiral nematic liquid crystals and method of using same
First Claim
1. An optical switch comprising:
- at least a first layer of a cholesteric or chiral nematic liquid crystal for decomposing an incident light beam into first and second circularly polarized components, one of which is transmitted by said layer, and the second of which is reflected by said layer;
first and second reflector means disposed, one on each side of said layer, for reflecting both of said circularly polarized components back toward said layer to recombine them into a transmitted light beam; and
,means to selectively switch the direction of said transmitted beam comprising means to selectively switch the circular polarization sense of said polarized components before they are recombined in said liquid crystal layer.
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Accused Products
Abstract
Fiber optic switches using layers of cholesteric or chiral nematic liquid crystals (CLCs) are disclosed. The CLC layer acts both as a polarization beamsplitter and as a reflector by decomposing incoming unpolarized light into two orthogonal circularly polarized components. In a number of embodiments, switchable waveplates are employed to controllably switch the polarization direction of each of the polarization components. The components are then reflected back toward the CLC layer where they are recombined into a transmitted unpolarized beam. The direction of transmission depends on the circular sense of the polarized components, and therefore on the state of the switchable waveplates. In other embodiments, the CLCs are used actively by selectively exposing them to electric or magnetic fields or to heat which cause a phase change that temporarily neutralizes the circular polarization effect. In this manner, the CLCs can be used as switch elements themselves.
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Citations
18 Claims
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1. An optical switch comprising:
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at least a first layer of a cholesteric or chiral nematic liquid crystal for decomposing an incident light beam into first and second circularly polarized components, one of which is transmitted by said layer, and the second of which is reflected by said layer; first and second reflector means disposed, one on each side of said layer, for reflecting both of said circularly polarized components back toward said layer to recombine them into a transmitted light beam; and
,means to selectively switch the direction of said transmitted beam comprising means to selectively switch the circular polarization sense of said polarized components before they are recombined in said liquid crystal layer. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 14, 15, 16, 17, 18)
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10. An optical switch comprising:
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at least a first and a second layer of a cholesteric or chiral nematic liquid crystal disposed parallel to, and spaced from, one another for decomposing an incident light beam into circular polarized components; first and second reflector means disposed, one to reflect a circular polarized light beam component reflected by said first layer back toward said first layer, and a second to reflect a circular polarized component transmitted by said second layer back toward said second layer; and
,switchable waveplate means disposed between said first and second layers for selectively changing the circular sense of polarized light components traveling between said layers; whereby, the direction of a transmitted light beam that is formed by recombination of circular polarized light components in said layers is selectively changed by said switchable waveplate means.
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11. An optical switch comprising:
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at least a first layer of a cholesteric or chiral nematic liquid crystal; means to change the phase of said layer whereby an unpolarized light beam can be selectively separated into two circularly polarized components by said first layer; and
,first and second reflector means disposed, one on each side, of said layer to reflect light beams back toward said layer.
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12. A method of switching the direction of beams of light comprising the steps of:
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directing a beam of light to be switched at a layer of cholesteric or chiral nematic liquid crystal at an angle nearly parallel to a helix axis of the crystal, and in so doing, separating said beam of light into first and second circularly polarized components, one of which is transmitted by said layer, and the other of which is reflected by said layer; reflecting both said polarized components back toward said liquid crystal layer, and thereby recombining said polarized components into a transmitted light beam; and
,selectively causing said transmitted light beam to be transmitted in one of two directions by selectively changing the circular polarization sense of said polarized components before they are recombined by said liquid crystal layer.
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13. A method of switching the direction of beams of light comprising the steps of:
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directing a beam of light to at least a first layer of a chiral nematic liquid crystal to an angle nearly parallel to a helix axis of said layer so that the incoming light will be decomposed thereby into first and second circularly polarized components; and selectively changing the phase of said first layer to change its effects on the transmission and reflection of said beam of light.
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Specification