Optical switches using cholesteric or chiral nematic liquid crystals and method of using same

An optical switch comprising:

• 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.

An optical switch comprising:

• 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.

A method of switching the direction of beams of light comprising the steps of:

• 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.