Electronically tunable acousto-optic filter having selected crystal orientation

Claim 2

An acousto-optic filter body of crystalline quartz with an aconsto-optic interaction axis along which an optical beam and the group velocity vector of an acoustic wave are to be directed, said axis lying in the Y-Z crystal plane at an angle of approximately -11.2* from the crystalline Y axis.

Claim 3

An acousto-optic flter body of crystalline lithium niobate with an aconsto-optic interaction axis along which an optical beam and the group velocity vector of an acoustic wave are to be directed, said axis lying in the Y-Z crystal plane at an angle of approximately 4* from the crystalline Y axis.

Claim 4

Apparatus for diffracting light from a first polarization to a second polarization, said apparatus comprising an acoustically anisotropic, optically birefringent body of quartz having a longitudinal axis lying in the Y-Z crystal plane at an angle of approximately -11.2* from the crystalline Y axis, means for passing light of the first polarization into said body along said longitudinal axis, means for producing an acoustical wave in said body, and means for directing the acoustical wave and the light in said body such that the group velocity vector of the acoustical wave is substantially collinear with the path of the light in said body, thereby diffracting light of the first polarization to the second polarization within said body.

Claim 5

Apparatus as in claim 5 wherein said means for producing an acoustical wave in said body comprises an acoustical transducer bonded to said body.

Claim 6

Apparatus for diffracting light from a first polarization to a second polarization, said apparatus comprising an acoustically anisotropic, optically birefringent body of lithium niobate having a longitudinal axis lying in the Y-Z crystal plane at an angle of approximately 4* from the crystalline Y axis, means for passing light of the first polarization into said body along said longitudinal axis, means for producing an acoustical wave in said body, and means for directing the acoustical wave and the light in said body such that the group velocity vector of the acoustical wave is substantially collinear with the path of the light in said body, thereby diffracting light of the first polarization to the second polarizaion within said body.

Claim 8

The method of claim 8 wherein said medium is quartz and said longitudinal axis lies in the Y-Z crystal plane of the quartz medium at an angle of approximately -11.2* from the crystalline Y axis of the quartz medium.

Claim 9

The method of claim 8 wherein said medium is lithium niobate and said longitudinal axis lies in the Y-Z crystal plane of the lithium niobate medium at an angle of approximately 4* from the Y axis of the lithium niobate medium.

Claim 10

Apparatus for diffracting light from a first polarization to a second polarization, said apparatus comprising an acoustically anisotropic, optically birefringent crystal body having a longitudinal axis oriented at a selected non-zero angle from the X-Y plane of said crystal body, means for passing light of the first polarization into said crystal body along said longitudinal axis, means for producing an acoustical wave in said crystal body, and means for directing the acoustical wave and the light in said crystal body such that the group velocity vector of the acoustical wave is substantially collinear with the path of the light in said crystal body, the light of the first polarization being diffracted to the second polarization in said crystal body, said selected angle being determined by simultaneous solution of the two equations (1/ Delta n) delta / delta Alpha 1 ( Delta n ( Alpha 1)) -tan theta gp and delta / delta Alpha 2 ( Delta n ( Alpha 2)) 0 , where Alpha 1 is the angular variation from said longitudinal axis in the plane formed by the group and phase velocity vectors of the acoustical wave, Alpha 2 is the angular variation from said longitudinal axis in the plane containing said longitudinal axis and lying normal to said last-mentioned plane, theta gp is the angle between the group and phase velocity vectors of the acOustical wave, and Delta n is the birefringence of said crystal body.

Claim 11

Apparatus as in claim 11 wherein said crystal body comprises quartz and said selected angle is approximately (zyw) -11.2*, where z indicates that the direction of the thickness of said quartz body is along the crystalline Z axis of said quartz body before any rotations have been made, y indicates that the direction of the length of said quartz body is along the crystalline Y axis of said quartz body before any rotations have been made, and w indicates that the direction of the width of said quartz body is the axis of first rotation.

Claim 12

Apparatus as in claim 11 wherein said crystal body comprises lithium niobate and said selected angle is approximately (zyw) 4*, where z indicates that the direction of the thickness of said lithium niobate body is along the crystalline Z axis of said lithium niobate body before any rotations have been made, y indicates that the direction of the length of said lithium niobate body is along the crystalline Y axis of said lithium niobate body before any rotations have been made, and w indicates that the direction of the width of said lithium niobate body is the axis of first rotation.

Claim 13

Apparatus for diffracting light from a first polarization to a second polarization, said apparatus comprising an acoustically anisotropic, optically birefringent crystalline medium, means for directing light of the first polarization into said medium along an axis thereof, means for producing an acoustical wave having noncollinear group and phase velocity vectors in said medium and for directing the group velocity vector of the acoustical wave substantially collinearly with the light along said axis to diffract light of the first polarization to the second polarization, the frequency fo of the light and the frequency fa of the acoustical wave being related by the relationship fo c fa/V Delta n , where C/V is the ratio of the velocity of light in a vacuum to the group velocity of the acoustical wave in said medium and Delta n is the birefringence of said medium, said medium having a crystal orientation along said axis for which the effect upon the optical bandwidth of said apparatus due to the acoustical anisotropy of said medium is offset by the effect upon the optical bandwidth of said apparatus due to a variation in the optical birefringence of said medium in the direction of propagation of the light along said axis.

Claim 14

Apparatus as in claim 14 wherein said medium is quartz, and said axis lies in the Y-Z crystal plane of said quartz medium at an angle of approximately -11.2* from the crystalline Y axis of said quartz medium.

Claim 15

Apparatus as in claim 14 wherein said medium is lithium niobate, and said axis lies in the Y-Z crystal plane of said lithium niobate medium at an angle of approximately 4* from the Y axis of said lithium niobate medium.

Claim 16

Apparatus as in claim 14 wherein said axis is oriented at a non-zero angle from the X-Y plane of said medium, and said angle is determined by simultaneous solution of the following two equations: (1/ Delta n) ( delta / delta Alpha 1) ( Delta n ( Alpha 1)) - tan theta gp delta / delta Alpha 2 ( Delta n ( Alpha 2)) 0, where Alpha 1 is the angular variation from said axis in the plane formed by the group and phase velocity vectors of the acoustical wave, Alpha 2 is the angular variation from said axis in the plane containing said axis and lying normal to said last-mentioned plane, theta gp is the angle between the group and phase velocity vectors of the acoustical wave, and Delta n is the birefringence of said medium.

Claim 17

An acousto-optic filter comprising an acoustically anisotropic, optically birefringent crystalline medium, means for directing light of a first polarization into said medium along an axis thereof, mean for producing an acoustical wave having noncollinear group and phase velocity vectors in said medium and for directing the group velocity vector of the acoustical wave substantially collinearly with the light along said axis to diffract at least some light of the first polarization to a second polarization, said medium having a crystal orientation along said axis for which the effect upon the optical bandwidth of said filter due to the acoustical anisotropy of said medium is offset by the effect upon the optical bandwidth of said filter due to a variation in the optical birefringence of said medium in the direction of propagation of the light along said axis, and means for separating light of the first and second polarizations.

Claim 18

An acousto-optic filter as in claim 18 wherein said medium is quartz, and said axis lies in the Y-Z crystal plane of said quartz medium at an angle of approximately -11.2* from the crystalline Y axis of said quartz medium.

Claim 19

An acousto-optic filter as in claim 18 wherein said medium is lithium niobate, and said axis lies in the Y-Z crystal plane of said lithium niobate medium at an angle of approximately 4* from the Y axis of said lithium niobate medium.

Claim 20

An acousto-optic filter as in claim 18 wherein said axis is oriented at a non-zero angle from the X-Y plane of said medium, and said angle is determined by simultaneous solution of the following two equations: (1/ Delta n) ( delta / delta Alpha 1) ( Delta n ( Alpha 1)) - tan theta gp delta / delta Alpha 2 ( Delta n ( Alpha 2)) 0 , where Alpha 1 is the angular variation from said axis in the plane formed by the group and phase velocity vectors of the acoustical wave, Alpha 2 is the angular variation from said axis in the plane containing said axis and lying normal to said last-mentioned plane, theta gp is the angle between the group and phase velocity vectors of the acoustical wave, and Delta n is the birefringence of said medium.

Claim 22

An acousto-optic filter body of crystalline quartz having an acousto-optic interaction axis lying in the Y-Z crystal plane at an angle of approximately -11.2* from the crystalline Y axis.

Claim 23

An acousto-optic filter body of crystalline lithium niobate having an acousto-optic interaction axis lying in the Y-Z crystal plane at an angle of approximately 4* from the crystalline Y axis.

Claim 24

An acousto-optic filter body of crystalline quartz as in claim 23 also having a longitudinal axis lying in the Y-Z crystal plane at an angle of approximately -11.2* from the crystalline Y axis.

Claim 25

An acousto-optic filter body of crystalline lithium niobate as in claim 24 also having a longitudinal axis lying in the Y-Z crystal plane at an angle of approximately 4* from the crystalline Y axis.