Periodic dielectric waveguide for backward parametric interactions

Claim 2

A parametric device for traveling electro-magnetic waves comprising: a dispersive waveguide supportive of electro-magnetic wave energy having at least the angular frequencies omega 1, omega 2, and omega 3, where, omega 3 omega 1 + omega 2; a uniform, non-linear material extending longitudinally along at least a portion of said guide in the direction of wave propagation; said material having a periodic index of refraction variation in the direction of wave propagation, said variation having a period d given by: d 2 pi m/ Beta 1 + Beta 2 + Beta 3 where m is an integer, and where Beta 1, Beta 2 and Beta 3 are, to a first approximation, the propagation constants in the guide respectively corresponding to electro-magnetic waves having the angular frequencies omega 1, omega 2 and omega 3.

Claim 3

The device according to claim 1 where omega 1 omega 2 and Beta 1 Beta 2.

Claim 4

The device according to claim 1 wherein the periodic index of refraction variation in said material is produced by a fixed grating in said material.

Claim 5

The device according to claim 1 further comprising means For launching an acoustic surface wave along said material thereby to induce said periodic index variation.

Claim 6

The device according to claim 4 wherein said launching means comprises: a piezo-electric transducer coupled to said material; and means for supplying an energizing potential to said transducer from an external source.

Claim 7

A waveguide for parametric interactions, said waveguide supporting electro-magnetic wave propagation at at least three angular frequencies, omega 1, omega 2, and omega 3, where omega 1 + omega 2 omega 3, said waveguide comprising: a substrate of dielectric material having an index of refraction ns; and a film of non-linear dielectric material overlaid on said substrate, said film having an index of refraction nf where ns< n f, at least a portion of said film having a periodic index of refraction variation in a direction in which electro-magnetic radiation propagates in the guide, said variation having a period d given by d 2 pi m/ Beta 1 + Beta 2 + Beta 3 where m is an integer, and where Beta 1, Beta 2 and Beta 3 are respectively, to a first approximation, the propagation constants of the three electro-magnetic waves in the guide, the period of the variation also satisfying the equation d < lambda i/(ne + ns) where lambda i is the shortest wavelength of electro-magnetic radiation involved in the parametric interaction and ne is its effective index of refraction in the guide.

Claim 8

A waveguide for parametric interactions, said waveguide supporting electro-magnetic wave propagation at at least three angular frequencies, omega 1, omega 2, and omega 3, where omega 1 + omega 2 omega 3, said waveguide comprising: a substrate of dielectric material having an index of refraction ns; and a film of non-linear dielectric material overlaid on said substrate, said film having an index of refraction nf where ns< n f, at least a portion of said film having a periodic index of refraction variation in a direction in which electro-magnetic radiation propagates in the guide, said variation having a period d given by d 2 pi m/ Beta 1 + Beta 2 + Beta 3 where m is an integer, and where Beta 1, Beta 2 and Beta 3 are respectively, to a first approximation, the propagation constants of the three electro-magnetic waves in the guide, the period of the variation also satisfying the equation d < lambda i/(ne + ns) where lambda i is the shortest wavelength of electro-magnetic radiation involved in the parametric interaction and ne is its effective index of refraction in the guide.

Claim 9

The waveguide according to claim 6 wherein said periodic variation is induced by a corrugation in the upper surface of the film.

Claim 10

The waveguide according to claim 6 wherein said periodic variation is induced by a grating in the upper surface of the film.

Claim 11

The waveguide according to claim 6 wherein said periodic index variation is induced by a plurality of discontinuities longitudinally spaced along the upper surface thereof, said discontinuities being spaced apart by the distance d.

Claim 12

The waveguide according to claim 6 wherein said periodic variation comprises a periodic variation in the non-linear or linear susceptability of said non-linear material.

Claim 13

The waveguide according to claim 6 wherein said periodic index variation is induced by a corrugation at the boundary between said substrate and said film.

Claim 14

The waveguide according to claim 6 wherein said periodic index variation is induced by a grating at the boundary between said substrate and said film.

Claim 15

The waveguide according to claim 6 wherein said periodic index variation is induced by a plurality of longitudinally spaced discontinuities at the boundary between said substrate and said film, said discontinuities being spaced apart by the distance d.

Claim 16

The waveguide according to claim 6 further including means for launching an acoustic surface wave in said film, said wave having a wavelength given by the equation Lambda 2 pi m/ Beta 1 + Beta 2 + Beta 3 thereby inducing said periodic index variation.

Claim 17

The waveguide according to claim 6 further including: means for introducing into said waveguide the electro-magnetic waves to be parametrically interacted; and means for extracting from said waveguide the results of said interaction.

Claim 18

The waveguide according to claim 15 wherein said introducing and extracting means comprise a prism coupler mounted to said film.

Claim 19

The waveguide according to claim 15 wherein said introducing and extracting means comprise a grating.

Claim 20

A waveguide for parametric interactions, said waveguide supporting electro-magnetic wave propagation at at least three angular frequencies, omega 1, omega 2, and omega 3, wheRe omega 1 + omega 2 omega 3, said waveguide comprising: a substrate of non-linear dielectric material having an index of refraction ns; and a film of linear dielectric material overlaid on said substrate, said film having an index of refraction nf where ns < nf, at least a portion of said film having a periodic index of refraction variation in a direction in which electro-magnetic radiation propagates in the guide, said variation having a period d given by d 2 pi m/ Beta 1 + Beta 2 + Beta 3 where m is an integer, and where Beta 1, Beta 2 and Beta 3 are respectively, to a first approximation, the propagation constants of the three electro-magnetic waves in the guide, the period of the variation also satisfying the equation d < lambda i/(ne + ns) where lambda i is the shortest wavelength of electro-magnetic radiation involved in the parametric interaction and ne is its effective index of refraction in the guide.

Claim 21

A waveguide for parametric interactions, said waveguide supporting electro-magnetic wave propagation at at least three angular frequencies, omega 1, omega 2, and omega 3, wheRe omega 1 + omega 2 omega 3, said waveguide comprising: a substrate of non-linear dielectric material having an index of refraction ns; and a film of linear dielectric material overlaid on said substrate, said film having an index of refraction nf where ns < nf, at least a portion of said film having a periodic index of refraction variation in a direction in which electro-magnetic radiation propagates in the guide, said variation having a period d given by d 2 pi m/ Beta 1 + Beta 2 + Beta 3 where m is an integer, and where Beta 1, Beta 2 and Beta 3 are respectively, to a first approximation, the propagation constants of the three electro-magnetic waves in the guide, the period of the variation also satisfying the equation d < lambda i/(ne + ns) where lambda i is the shortest wavelength of electro-magnetic radiation involved in the parametric interaction and ne is its effective index of refraction in the guide.

Claim 22

The waveguide according to claim 18 wherein said periodic variation is induced by a corrugation in the upper surface of the film.

Claim 23

The waveguide according to claim 18 wherein said periodic variation is induced by a grating in the upper surface of the film.

Claim 24

The waveguide according to claim 18 wherein said periodic index variation is induced by a plurality of discontinuities longitudinally spaced along the upper surface thereof, said discontinuities being spaced apart by the distance d.

Claim 25

The waveguide according to claim 18 wherein said periodic variation comprises a periodic variation in the susceptability of said non-linear material.

Claim 26

The waveguide according to claim 18 wherein said periodic index variation is induced by a corrugation at the boundary between said substrate and said film.

Claim 27

The waveguide according to claim 18 wherein said periodic index variation is induced by a grating at the boundary between said substrate and said film.

Claim 28

The waveguide according to claim 18 wherein said periodic index variation is induced by a plurality of longitudinally spaced discontinuities at the boundary between said substrate and said film, said discontinuities being spaced apart by the distance d.

Claim 29

The waveguide according to claim 18 further including means for launching an acoustic surface wave in said film, said wave having a wavelength given by the equation Lambda 2 pi m/ Beta 1 + Beta 2 + Beta 3 thereby inducing said periodic index variation.

Claim 30

The waveguide according to claim 18 further including: means for introducing into said waveguide the electro-magnetic waves to be parametrically interacted; and means for extracting from said waveguide the results of said interaction.

Claim 31

The waveguide according to claim 27 wherein said introducing and extracting means comprise a prism coupler mounted to said film.

Claim 32

The waveguide according to claim 27 wherein said introducing and extracting means comprise a grating.

Claim 33

The device according to claim 1 wherein the propagating electro-magnetic waves are confined in one transverse direction.

Claim 34

The device according to claim 1 wherein the propagating electro-magnetic waves are confined in two transverse directions.

Claim 35

The device according to claim 1 wherein said device is a clad optical fiber.