Tunable acousto-optic method and apparatus

Claim 2

In an acousto-optic apparatus for diffracting light of a first polarization and first bandwidth into light of a second polarization including, optically birefringent medium means disposed to receive a beam of light having a first optical bandwidth and to be diffracted from a first polarization into a second polarization, means for exciting an acoustic wave in said optically birefringent medium at a frequency related to the optical frequency of the light to be diffracted from the first to the second polarization, such acoustic wave having a path of propagation within said optically birefringent medium which is substantially collinear with the optical beam path for cumulatively collinearly diffracting the light beam on the acoustic wave within the optically birefringent medium to selectively diffract light of the first polarization, and within a second instantaneous passband of optical frequencies narrower than said first bandwidth and related to the frequency of the acoustic wave, into light of the second polarization, and means for developing said light beam to be diffracted with said first optical bandwidth wider tHan said second narrower instantaneous passband.

Claim 3

The apparatus of claim 1 including, means for analyzing the diffracted light beam to separate light of one of said polarizations from the light of the other of said polarizations.

Claim 4

The apparatus of claim 1 including, means for varying the frequency of the acoustic wave within said optically birefringent medium over a band of acoustic frequencies to tune the second instantaneous passband of optical frequencies over an optical bandwidth.

Claim 5

The apparatus of claim 1 including, means for linearly polarizing the light beam to be diffracted in the direction of the first polarization.

Claim 6

The apparatus of claim 1 wherein said optically birefringent medium means is disposed to receive the beam of light to be diffracted with a light beam path through said medium such that the light beam enters said medium at one side, traverses a beam path within said medium, and emerges from said medium as a diffracted light beam on a side of said medium opposite the side of light beam entry.

Claim 7

The apparatus of claim 1 wherein said means for exciting an acoustic wave in said optically birefringent medium includes, acoustic transducer means coupled to said optically birefringent medium means for directing an excited acoustic wave into the medium at such an angle as to be deflected at a boundary of said optically birefringent medium from a path which is inclined to the optical beam path into a path which is generally collinear with the optical beam path within said optically birefringent medium.

Claim 8

The apparatus of claim 1 wherein said means for developing said light beam of first polarization and first bandwidth develops said light beam as a beam of incoherent light.

Claim 9

In a acousto-optic apparatus for diffracting light of a first polarization into light of a second polarization including, optically birefringent medium means disposed to receive a beam of light to be diffracted from a first polarization into a second polarization such beam of light having a beam path through said medium such that the light beam enters the medium at one side, traverses a beam path within the medium, and emerges from the medium as a diffracted light beam on a side of the medium opposite to the side of light beam entry, means for exciting an acoustic wave in said optically birefringent medium at a frequency related to the optical frequency of the light to be diffracted from the first to the second polarization, such acoustic wave having a path of propagation within said optically birefringent medium which is substantially collinear with a substantial component of the optical beam path for cumulatively collinearly diffracting the light beam on the acoustic wave within the optically birefringent medium to diffract light of the first polarization and of an optical frequency related to the frequency of the acoustic wave into light of the second polarization.

Claim 10

In a acousto-optic apparatus for diffracting light of a first polarization into light of a second polarization including, optically birefringent medium means disposed to receive a beam of light to be diffracted from a first polarization into a second polarization such beam of light having a beam path through said medium such that the light beam enters the medium at one side, traverses a beam path within the medium, and emerges from the medium as a diffracted light beam on a side of the medium opposite to the side of light beam entry, means for exciting an acoustic wave in said optically birefringent medium at a frequency related to the optical frequency of the light to be diffracted from the first to the second polarization, such acoustic wave having a path of propagation within said optically birefringent medium which is substantially collinear with a substantial component of the optical beam path for cumulatively collinearly diffracting the light beam on the acoustic wave within the optically birefringent medium to diffract light of the first polarization and of an optical frequency related to the frequency of the acoustic wave into light of the second polarization.

Claim 11

The apparatus of claim 8 including, means for analyzing the diffracted light beam to separate light of one of said polarizations from light of the other of said polarizations.

Claim 12

The apparatus of claim 8 including means for varying the frequency of the acoustic wave in said optically birefringent medium to vary the optical frequency of the light diffracted from the first polarization into the second polarization.

Claim 13

The apparatus of claim 8 including, means for developing said light beam to be diffracted with an optical bandwidth wider than the instantaneous passband of the light which is diffracted from the first polarization to the second polarization.

Claim 14

The apparatus of claim 8 including, acoustic transducer means for exciting and directing the acoustic wave into said optically birefringent medium at such an angle as to be deflected at a boundary of said optically birefringent medium from a path which is inclined to the optical beam path into a path which is generally collinear with the optical beam path within said optically birefringent medium.

Claim 15

The apparatus of claim 8 wherein said birefringent medium means is a birefringent crystal.

Claim 16

The apparatus of claim 29 including, means for linearly polarizing the incident light beam in the direction of the first polarization.

Claim 17

In an acousto-optic apparatus, a light beam of a first polarization and bandwidth which is to have only a portion of its total handwith diffracted into light of a second polarization, optically birefringent medium means disposed to receive the beam of light having a first optical bandwidth and to be diffracted from a first polarization into a second polarization, means for exciting an acoustic wave in said optically birefringent medium at a frequency related to the optical frequency of that portion of the bandwidth of the light to be diffracted from the first to the second polarization, such acoustic wave having a path of propagation within said optically birefringent medium which is substantially collinear with a substantial component of the optical beam path within said birefringent medium for cumulatively collinearly diffracting the light beam on the acoustic wave within the optically anisotropic medium to diffract light of the first polarization, and within a second instantaneous passband of optical frequencies narrower than said first bandwidth of light and related to the frequency of the acoustic wave, into light of the second polarization, means for varying the frequency of the acoustic wave within said optically birefringent medium over a band of acoustic frequencies having a bandwidth in excess of 10 percent to tune the second instantaneous passband of optical frequencies for light diffracted from the first polarization to the second polarization over a comparable optical bandwidth in excess of 10 percent.

Claim 18

In an acousto-optic apparatus, a light beam of a first polarization and bandwidth which is to have only a portion of its total handwith diffracted into light of a second polarization, optically birefringent medium means disposed to receive the beam of light having a first optical bandwidth and to be diffracted from a first polarization into a second polarization, means for exciting an acoustic wave in said optically birefringent medium at a frequency related to the optical frequency of that portion of the bandwidth of the light to be diffracted from the first to the second polarization, such acoustic wave having a path of propagation within said optically birefringent medium which is substantially collinear with a substantial component of the optical beam path within said birefringent medium for cumulatively collinearly diffracting the light beam on the acoustic wave within the optically anisotropic medium to diffract light of the first polarization, and within a second instantaneous passband of optical frequencies narrower than said first bandwidth of light and related to the frequency of the acoustic wave, into light of the second polarization, means for varying the frequency of the acoustic wave within said optically birefringent medium over a band of acoustic frequencies having a bandwidth in excess of 10 percent to tune the second instantaneous passband of optical frequencies for light diffracted from the first polarization to the second polarization over a comparable optical bandwidth in excess of 10 percent.

Claim 19

The apparatus of claim 15 wherein said means for varying the frequency of the acoustic wave includes an acoustic transducer means having a bandwidth in excess of 10 percent for exciting acoustic waves over a relatively wide band of acoustic frequencies.

Claim 20

The apparatus of claim 15 wherein said means for varying the frequency of the acoustic wave over a band of acoustic frequencies includes, tunable radio frequency generator means for generating an electrical signal tunable over a band of frequencies as wide as the band of acoustic frequencies to be generated within said optically birefringent medium, and acoustic transducer means responsive to the tunable electric signal for exciting the acoustic waves to be excited in said birefringent medium means.

Claim 21

The apparatus of claim 15 including, means for developing said light beam to be diffracted with said first optical bandwidth wider than said second instantaneous passband of light which is diffracted from the first polarization to the second polarization.

Claim 22

The apparatus of claim 15 including, means for analyzing the diffracted light beam to separate light of one of said polarizations from light of other of the said polarizations.

Claim 23

The apparatus of claim 15 wherein said light beam of first polarization is a beam of incoherent light.

Claim 24

An acousto-optic apparatus comprising, means for developing a first light beam having a first band of frequencies with a predetermined polarization, an anisotropic crystal disposed to receive said beam, said crystal being selected and arranged to propogate said light beam as a particular wave in a birefringent system, said crystal being further capable of diffracting and propagating a second light beam with a second band of frequencies within said first band and being of orthogonal polarization to said first beam, as another wave of said birefringent system in response to acoustical waves in the medium, means coupled to said crystal for developing acoustical waves of predetermined frequency in said anisotropic crystal, the frequency of said acoustical wave being selected to define a phase-matched relationship with said first light beam such that the vector sum of the momentum vectors of said second band of frequencies narRower than and within said first band of frequencies of the incident light beam and the acoustical wave are equal to that of said second light beam orthogonally oriented to said input light beam, whereby said second narrower band of frequencies of said incident light beam satisfying said phase-matched relationship for a given acoustical wave frequency is diffracted into said orthogonal polarization, and an output analyzer aligned to selectively pass the light waves orthogonally related to the polarization of said input light beam.

Claim 25

An acousto-optic apparatus comprising, means for developing a first light beam having a first band of frequencies with a predetermined polarization, an anisotropic crystal disposed to receive said beam, said crystal being selected and arranged to propogate said light beam as a particular wave in a birefringent system, said crystal being further capable of diffracting and propagating a second light beam with a second band of frequencies within said first band and being of orthogonal polarization to said first beam, as another wave of said birefringent system in response to acoustical waves in the medium, means coupled to said crystal for developing acoustical waves of predetermined frequency in said anisotropic crystal, the frequency of said acoustical wave being selected to define a phase-matched relationship with said first light beam such that the vector sum of the momentum vectors of said second band of frequencies narRower than and within said first band of frequencies of the incident light beam and the acoustical wave are equal to that of said second light beam orthogonally oriented to said input light beam, whereby said second narrower band of frequencies of said incident light beam satisfying said phase-matched relationship for a given acoustical wave frequency is diffracted into said orthogonal polarization, and an output analyzer aligned to selectively pass the light waves orthogonally related to the polarization of said input light beam.

Claim 26

An acousto-optic apparatus as in claim 21 in which said crystal is provided with end faces forming an acoustic resonator, a reflective surface carried on one of said end faces for internally reflecting light waves from within said crystal.

Claim 27

An acousto-optic apparatus as in claim 21 in which said crystal has a pair of end faces, one of said end faces being constructed and arranged to admit said first light beam into said crystal, light reflective means being provided at said other end face for internally reflecting light impinging thereon.

Claim 28

An acousto-optic apparatus as in claim 22 wherein said means for developing acoustical waves is coupled to said end face having said light reflective means.

Claim 29

The apparatus of claim 21 wherein said means for developing said first light beam develops a first light beam as a beam of incoherent light.

Claim 30

An acousto-optic apparatus including a first light beam having a first band of frequencies and predetermined polarization, an anisotropic crystal medium disposed to receive said first light beam, said crystal being selected and arranged to propagate said first light beam as a particular wave in a birefringent system, said crystal being further capable of diffracting and propagating a second light beam having a second band of frequencies within and narrower than said first band of frequencies at orthogonal polarization to said first beam as another wave of said birefringent system in response to acoustical waves, means coupled to said medium for developing acoustical waves of predetermined frequency in said anisotropic medium, the frequency of said acoustical waves being selected to define a phase-matched relationship such that the vector sum of the momentum vectors of said second narrower band of frequencies of said incident light beam and the acoustical wave are equal to that of said second band of frequencies of said second light beam orthogonally oriented to said first input light beam, whereby said second band of frequencies of said incident light beam satisfying said phase-matched relationship for the given acoustical wave frequencies are diffracted into said orthogonal polarization.

Claim 31

An acousto-optic apparatus including a first light beam having a first band of frequencies and predetermined polarization, an anisotropic crystal medium disposed to receive said first light beam, said crystal being selected and arranged to propagate said first light beam as a particular wave in a birefringent system, said crystal being further capable of diffracting and propagating a second light beam having a second band of frequencies within and narrower than said first band of frequencies at orthogonal polarization to said first beam as another wave of said birefringent system in response to acoustical waves, means coupled to said medium for developing acoustical waves of predetermined frequency in said anisotropic medium, the frequency of said acoustical waves being selected to define a phase-matched relationship such that the vector sum of the momentum vectors of said second narrower band of frequencies of said incident light beam and the acoustical wave are equal to that of said second band of frequencies of said second light beam orthogonally oriented to said first input light beam, whereby said second band of frequencies of said incident light beam satisfying said phase-matched relationship for the given acoustical wave frequencies are diffracted into said orthogonal polarization.

Claim 32

The apparatus of claim 26 wherein said first light beam is a beam of incoherent light.

Claim 33

An optical filter for deriving a narrower band of frequencies from a light beam having a first band of frequencies comprising, means for developing an input light beam having a first band of optical frequencies and having a predetermined first polarization, an optically anisotropic medium disposed to receive said light beam, said medium being selected and arranged to propagate said light beam as particular light waves in a birefringent system, said medium being further capable of diffracting and propogating a second band of optical frequencies narrower than and within said first band of optical frequencies, of orthogonal polarization to said first band as another wave of said birefringent system, in response to an acoustical wave in said medium, means coupled to said medium for developing acoustical waves of predetermined frequency in said anisotropic medium, the predetermined frequency of said acoustical waves being selected to define a phase-matched relationship such that the vector sum of certain momentum vectors of the incident light beam and the acoustical wave are substantially equal to the momentum vector of said second narrower band of light waves, whereby said second narrower band of optical freqUencies of the incident light beam satisfying said momentum vector condition for a given acoustical wave frequency is diffracted into said orthogonal polarization to provide said second narrower band of optical frequencies, an output analyzer aligned to analyze the light waves orthogonally related to the first polarization of said input light beam, and means for varying the frequency of the acoustical waves to vary the frequency of said second narrower band of the light waves being diffracted into said orthogonal polarization.

Claim 34

An optical filter for deriving a narrower band of frequencies from a light beam having a first band of frequencies comprising, means for developing an input light beam having a first band of optical frequencies and having a predetermined first polarization, an optically anisotropic medium disposed to receive said light beam, said medium being selected and arranged to propagate said light beam as particular light waves in a birefringent system, said medium being further capable of diffracting and propogating a second band of optical frequencies narrower than and within said first band of optical frequencies, of orthogonal polarization to said first band as another wave of said birefringent system, in response to an acoustical wave in said medium, means coupled to said medium for developing acoustical waves of predetermined frequency in said anisotropic medium, the predetermined frequency of said acoustical waves being selected to define a phase-matched relationship such that the vector sum of certain momentum vectors of the incident light beam and the acoustical wave are substantially equal to the momentum vector of said second narrower band of light waves, whereby said second narrower band of optical freqUencies of the incident light beam satisfying said momentum vector condition for a given acoustical wave frequency is diffracted into said orthogonal polarization to provide said second narrower band of optical frequencies, an output analyzer aligned to analyze the light waves orthogonally related to the first polarization of said input light beam, and means for varying the frequency of the acoustical waves to vary the frequency of said second narrower band of the light waves being diffracted into said orthogonal polarization.

Claim 35

An optical filter as in claim 28 wherein said means for developing an acoustical wave includes an electro-acoustical transducer, means coupling an acoustical output of said transducer to said anisotropic medium and wherein said means for varying the frequency of the acoustical waves includes a source of time varying electrical signals coupled to said transducer to drive same, said source including means for varying the frequency content of the output electrical signals delivered to said transducer.

Claim 36

An optical filter as in claim 28 wherein said anisotropic medium is a crystal of lithium niobate.

Claim 37

Optical filters as in claim 30 wherein said crystal of lithium niobate is oriented to propagate the input broad band light beam as an extraordinary wave along the axis of said crystal, the diffracted wave being an ordinary narrower band wave along the axis, the momentum vectors of said waves satisfying the condition ke + ka ko, where ke is the momentum vector of said narrower band of the extraordinary wave, ka is the momentum vector of he acoustic wave and ko is the momentum vector of the narrower band ordinary wave.

Claim 38

An optical filter as in claim 30 wherein said crystal is provided with a face inclined at an angle to said input light beam and against which the acoustic waves are directed to reflect from the inside of said inclined face to travel collinearly with said input light beam.

Claim 39

An optical filter as in claim 32 wherein said acoustical waves are initially longitudinal, and are converted into shear waves by reflection from said surface.

Claim 40

An optical filter as in claim 28 in which said narrower band output light beam and acoustic wave propagate collinearly through said anisotropic medium.

Claim 41

Optical filter as in claim 28 wherein said anisotropic medium is a birefringent crystal.

Claim 42

An optical filter as in claim 28 wherein said medium is a birefringent crystal having an input inclined face and a reflective surface at opposite ends.

Claim 43

An optical filter as in claim 36 in which said means for developing acoustical waves is coupled to said reflective surface.

Claim 44

The apparatus of claim 28 wherein said means for developing said input light beam comprises means for developing an incoherent input light beam.

Claim 45

An optical filter comprising, a light beam having a first band of frequencies polarized in a first polarization orientation direction, an isotropic medium disposed to receive said beam, said medium being selected and arranged to propagate said light beam as particular waves having said first polarization orientation in a birefringent system, said medium being further capable of diffracting and propagating a light beam with a second band of frequencies narrower than and within said first band and polarized in a second polarization orientation different from said first beam as another wave of said birefringent system in response to acoustical waves, means coupled to said medium for developing an acoustical wave of predetermined frequency in said anisotropic medium, the frequency of said acoustical wave being selected to define a matched relationship such that the vector sum of the momentum vectors of the narrower second band of frequencies within and of said first band of frequencies of the incident light beam and the acoustical wave are equal to that of the narrower frequency band of light oriented at said second polarization, wherEby said narrower second band of said incident light beam satisfying said matched relationship for a given acoustical wave frequency is diffracted into said second polarization orientation, an output analyzer aligned to analyze the light waves of said second polarization, and means for varying the frequency of the acoustical wave to vary the frequency of light waves being diffracted into said second polarization orientation.

Claim 46

An optical filter comprising, a light beam having a first band of frequencies polarized in a first polarization orientation direction, an isotropic medium disposed to receive said beam, said medium being selected and arranged to propagate said light beam as particular waves having said first polarization orientation in a birefringent system, said medium being further capable of diffracting and propagating a light beam with a second band of frequencies narrower than and within said first band and polarized in a second polarization orientation different from said first beam as another wave of said birefringent system in response to acoustical waves, means coupled to said medium for developing an acoustical wave of predetermined frequency in said anisotropic medium, the frequency of said acoustical wave being selected to define a matched relationship such that the vector sum of the momentum vectors of the narrower second band of frequencies within and of said first band of frequencies of the incident light beam and the acoustical wave are equal to that of the narrower frequency band of light oriented at said second polarization, wherEby said narrower second band of said incident light beam satisfying said matched relationship for a given acoustical wave frequency is diffracted into said second polarization orientation, an output analyzer aligned to analyze the light waves of said second polarization, and means for varying the frequency of the acoustical wave to vary the frequency of light waves being diffracted into said second polarization orientation.

Claim 47

An optical filter as in claim 39 in which said first polarization orientation is linear in a predetermined direction, and in which said second polarization orientation is linear in a direction orthogonal to the first.

Claim 48

The apparatus of claim 39 wherein said light beam of first bandwidth and first polarization is a beam of incoherent light.

Claim 49

In an acousto-optic method the steps of, exciting an acoustic wave in an optically birefringent medium selected and arranged to propagate light of a first polarization and of a first bandwidth as particular waves in the medium cumulatively and substantially collinearly diffracting said light of said first polarization and first bandwidth on the acoustic wave within the optically birefringent medium to selectively cumulatively diffract only a narrower instantaneous bandwidth portion of said first band of frequencies of said light of said first polarization into light of said second polarization.

Claim 50

In an acousto-optic method the steps of, exciting an acoustic wave in an optically birefringent medium selected and arranged to propagate light of a first polarization and of a first bandwidth as particular waves in the medium cumulatively and substantially collinearly diffracting said light of said first polarization and first bandwidth on the acoustic wave within the optically birefringent medium to selectively cumulatively diffract only a narrower instantaneous bandwidth portion of said first band of frequencies of said light of said first polarization into light of said second polarization.

Claim 51

The method of claim 42 including the step of analyzing the diffracted light beam to separate light of one of said polarizations from light of the other of said polarizations.

Claim 52

The method of claim 42 including the steps of varying the frequency of the acoustic wave in the optically birefringent medium to vary the center frequency of the narrower band of optical frequencies cumulatively diffracted to the second polarization within the wider bandwidth of light of the first polarization.

Claim 53

The method of claim 42 wherein the step of collinearly diffracting the light beam on the acoustic wave includes the step of directing the light beam to the diffracted through the optically birefringent medium such that the light beam to be diffracted passes into the birefringent medium on one side thereof and the diffracted light beam emerges from the medium at a side opposite to the first side.

Claim 54

The method as in claim 45 including the steps of analyzing the light beam which emerges from the medium at the side opposite the first side to separate light of one of said polarizations from light of the other of said polarizations.

Claim 55

The method of claim 42 wherein said light of first polarization which is selectively cumulatively collinearly diffracted on the acoustic wave into light of said second polarization is incoherent light.

Claim 56

In an acousto-optic method for selectively diffracting only a portion of the bandwidth of light of a first polarization into light of a second polarization the steps of, exciting an acoustic wave in an optically birefringent medium selected and arranged to propagate light as a particular wave in the birefringent medium, such acoustic wave being of an acoustic frequency related to the optical frequency of the portion of the bandwidth of the light to be diffracted from the first to the second polarization, and cumulatively and substantially collinearly diffracting a beam of light having a first optical bandwidth and the first polarization on the acoustic wave within the optically birefringent medium to selectively cumulatively diffract light of the first polarization and substantially only within an instantaneous optical passband less than said first bandwidth into light of said second polarization.

Claim 57

In an acousto-optic method for selectively diffracting only a portion of the bandwidth of light of a first polarization into light of a second polarization the steps of, exciting an acoustic wave in an optically birefringent medium selected and arranged to propagate light as a particular wave in the birefringent medium, such acoustic wave being of an acoustic frequency related to the optical frequency of the portion of the bandwidth of the light to be diffracted from the first to the second polarization, and cumulatively and substantially collinearly diffracting a beam of light having a first optical bandwidth and the first polarization on the acoustic wave within the optically birefringent medium to selectively cumulatively diffract light of the first polarization and substantially only within an instantaneous optical passband less than said first bandwidth into light of said second polarization.

Claim 58

The method of claim 48 including the step of analyzing the diffracted light beam to separate light of one of said polarizations from light of the other of said polarizations.

Claim 59

The method of claim 48, including the step of varying the frequency of the acoustic wave in the optically birefringent medium to vary the center frequency of the instantaneous passband of optical frequencies cumulatively diffracted to the second polarization within said wider first optical bandwidth of light to be diffracted.

Claim 60

The method of claim 48 including the step of linearly polarizing the light beam to be diffracted in the direction of the first polarization.

Claim 61

The method of claim 48 wherein the step of collinearly diffracting the light beam on the acoustic wave includes the step of, directing the light beam to be diffracted through the optically birefringent medium such that the light beam to be diffracted passes into the birefringent medium on one side thereof and the diffracted light beam emerges from the medium at a side opposite the first side.

Claim 62

The method of claim 48 including the step of directing the excited acoustic wave relative to the medium at such an angle as to be deflected at a boundary of the medium from a path which is inclined to the optical beam path into a path which is generally collinear with the optical beam path within the optically birefringent medium.

Claim 63

The method of claim 48 wherein the light of first polarization which is diffracted into the second polarization is incoherent light.