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Ferroelectric Thin Films for Optical Signal Processing

IP.com Disclosure Number: IPCOM000074259D
Original Publication Date: 1971-Apr-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 2 page(s) / 13K

Publishing Venue

IBM

Related People

Scott, BA: AUTHOR [+3]

Abstract

An optical waveguiding ferroelectric thin-film structure for signal processing is composed of a thin-ferroelectric film on a substrate of identical crystal structure and lattice constants. The structure employs dielectric compositions derived from ABO3 structures of the pseudo-illemenite Li(Nb, Ta)O(3), perovskite and tungsten bronze types to form both the film and the substrate. The required refractive index difference for optical waveguiding is obtained in one or more of the following ways: Class I: Variation of A/B cation ratio in ABO(3)-type structure between film and substrate. Class II: Variation in number and/or types of A cations between film and substrate. Class lII: Variation in number and/or types of B cations between film and substrate.

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Ferroelectric Thin Films for Optical Signal Processing

An optical waveguiding ferroelectric thin-film structure for signal processing is composed of a thin-ferroelectric film on a substrate of identical crystal structure and lattice constants. The structure employs dielectric compositions derived from ABO3 structures of the pseudo-illemenite Li(Nb, Ta)O(3), perovskite and tungsten bronze types to form both the film and the substrate. The required refractive index difference for optical waveguiding is obtained in one or more of the following ways: Class I: Variation of A/B cation ratio in ABO(3)-type structure between film and substrate.

Class II: Variation in number and/or types of A cations between film and substrate.

Class lII: Variation in number and/or types of B cations between film and substrate.

The structure may be formed by single crystal substrate growth by melt techniques and subsequent poling if ferroelectric, deposition of thin-film composition on the substrate by sputtering, vapor deposition or liquid phase epitaxy, followed by annealing of the thin film to reoxidize it, and reduce small strains, if necessary.

Some examples of the three classes are set forth below.

Class I

xLi(2)O.(1-x)Nb(2)O(5) System

Composition: Film x = 0.48

Substrate x = 0.50

Lattice Constants: (pseudo-illmenite structure) Film a = 5.151 c = 13.864

Substrate a = 5.149 c = 13.862 n(f) - n(s) = 0.03, where nf and n are the extraordinary refractive indices of the film and substrate, respectively. Device Functions: Electrooptic modulation and deflection. Nonlinear optical effects such as second

harmonic generation and frequency shifting.

Class II

xNaNbO(3).(1-x)BaNb(2)O(6) System

Composition: Film x = 0.22

Substrate x = 0.33

Lattice Constants: (tungsten bronze-type structure) Film a = 17.62 b = 17.65 c = 4.000

Substrat...