Wavelength Variable Optical Filter With Transparent Surface Electrodes

The patent transitions from a conventional planar electrode configuration to a three-dimensional folded electrode structure. The electrodes are arranged in a zigzag or serpentine pattern within the crystal, effectively reducing the interelectrode distance in the light propagation direction while maintaining adequate spacing for beam passage. This dimensional reconfiguration allows the electric field to be concentrated in a shorter path, reducing the required drive voltage from kilovolt levels to more manageable voltages.

The electrode structures are nested within the crystal boundaries, with the folded electrodes contained inside the crystal volume. This nesting allows the electrodes to be positioned closer together in the effective field direction while still providing sufficient physical space for the light beam to pass through the crystal without obstruction. The electrodes are essentially embedded or nested within the crystal structure rather than being placed on opposite external surfaces.

By folding the electrodes into a three-dimensional configuration within the crystal, the patent decouples the interelectrode distance from the crystal's external dimensions. This allows the effective electrode spacing to be small (reducing drive voltage) while the crystal's external dimensions remain large enough to accommodate standard beam diameters and provide optical design flexibility. The folded structure adds an extra dimension to the electrode arrangement, enabling independent optimization of electrical and optical parameters.

The electrode structure exhibits local variation in spacing and configuration. In regions where the electric field is needed, the electrodes are closely spaced to generate sufficient field strength at low voltage. In other regions, particularly along the light propagation path, there is adequate space for beam passage. This local differentiation of electrode spacing allows simultaneous optimization of both power consumption and optical performance.

The folded electrode configuration resolves the conflict between using standard optical components (which produce several mm beam diameters) and maintaining low drive voltage. By arranging electrodes in a three-dimensional folded pattern within the crystal volume, the patent enables both standard beam sizes and low voltage operation to coexist. The effective interelectrode distance is reduced through the folded geometry rather than by reducing the beam diameter, allowing compatibility with conventional optical systems.

The electrode structure is segmented into multiple sections or segments that are folded back on themselves. Rather than having two large electrodes on opposite crystal surfaces, the electrode structure is divided into multiple smaller segments arranged in a folded configuration. This segmentation reduces the maximum interelectrode distance while still providing adequate space for standard beam diameters, enabling low voltage operation with conventional optics.