Abstract: A segmented article is disclosed which has selected Bragg reflection characteristics for a selected input wavelength. The article includes alternating sections of optical materials which are aligned and have refractive indexes different from adjacent sections to form at least one superperiod consisting of a plurality of segments such that each segment consists of a section of a first optical material and a section of a second optical material. At least one segment of the superperiod is different in optical path from another segment of the superperiod, and the interfaces between sections of the superperiod create backward travelling waves of complex amplitude at the selected input wavelength. The sequentially odd interfaces in the superperiod form a first set of interfaces and the sequentially even interfaces in the superperiod form a second set of interfaces.

Abstract: There is disclosed an optical waveguide comprising a K.sub.1-x Rb.sub.x TiOmO.sub.4 single crystal substrate, wherein x is from 0 to 1 and M is P or As, having at least one optically smooth surface wherein sufficient K.sup.+ and/or Rb.sup.+ have been replaced by ions selected from at least one of H.sup.+ and NH.sub.4.sup.+ and, optionally, at least one monovalent ion selected from Rb.sup.+, Cs.sup.+, Tl.sup.+, and/or at least one divalent ion selected from Ba.sup.+2, Sr.sup.+2, Ca.sup.+2 and Pb.sup.+2 to chance the surface index of refraction at least a 0.00025 with respect to the index of refraction of the single crystal substrate. One process disclosed for producing an optical waveguide comprises the steps of contacting at least one optically smooth surface of a single crystal of K.sub.1-x Rb.sub.x TiOmO.sub.4 with an ion exchange medium capable of supplying said replacement ions, at a temperature of from about 100.degree. C. to about 600.degree. C.

Abstract: There is disclosed an optical waveguide comprising a K.sub.1-x Rb.sub.x TiOMO.sub.4 single crystal substrate, wherein x is from 0 to 1 and M is P or As, having at least one optically smooth surface wherein sufficient K.sup.+ and/or Rb.sup.+ have been replaced by ions selected from at least one of H.sup.+ and NH.sub.4.sup.+ and, optionally, at least one monovalent ion selected from Rb.sup.+, Cs.sup.+, Tl.sup.+, and/or at least one divalent ion selected from Ba.sup.+2, Sr.sup.+2, Ca.sup.+2 and Pb.sup.+2 change the surface index of refraction at least about 0.00025 with respect to the index of refraction of the single crystal substrate. One process disclosed for producing an optical waveguide comprises the steps of contacting at least one optically smooth surface of a single crystal of K.sub.1-x Rb.sub.x TiOMO.sub.4 with an ion exchange medium capable of supplying said replacement ions for sufficient time at a temperature of from about 100.degree. C. to about 600.degree. C., and cooling the resulting crystal.