US4968136A — Ring laser gyro and magnetic mirror therefor

Claim 1

Independent Claim 247 words

Laser gyro comprising a gyro block including a block of material having bores therein at least partially defining a closed laser beam path lying in a plane; means for completing the laser beam path entirely enclosed within said block including a plurality of mirrors, each of which is contacted to the gyro block at the intersection of said bores to form a closed optical cavity therewith and laser beam path entirely enclosed within the block and mirrors and sealed to the block to form a laser gas containment cavity; and means for generating counter-rotating laser beams within the cavity; said path being free of intracavity elements so that the beam travels unimpeded through the bores by reflection from the mirrors; one of said mirrors or said block including means for discriminating against S-polarization with respect to P-polarization without using Brewster angle windows; one of said mirrors being constructed and arranged to form a magnetic mirror comprising a magnetic, saturable, fast-switching layer and a magneto-optic layer coupled to said magnetic layer to introduce a non-reciprocal phase shift between said counter-propagating light beams while maintaining negligible non-reciprocal losses, said last named mirror including a substrate; conductors disposed within said substrate for generating rapidly switchable magnetic fields; said magnetically saturable layer having a well defined easy axis of magnetization perpendicular to said plane and disposed on the substrate; said separate magneto-optic layer disposed directly on the magnetically saturable layer; and a multilayer dielectric reflective stack disposed over the magneto-optic layer.

Claim 2

Dependent Claim 247 words

Laser gyro comprising a gyro block including a block of material having bores therein at least partially defining a closed laser beam path lying in a plane; means for completing the laser beam path entirely enclosed within said block including a plurality of mirrors, each of which is contacted to the gyro block at the intersection of said bores to form a closed optical cavity therewith and laser beam path entirely enclosed within the block and mirrors and sealed to the block to form a laser gas containment cavity; and means for generating counter-rotating laser beams within the cavity; said path being free of intracavity elements so that the beam travels unimpeded through the bores by reflection from the mirrors; one of said mirrors or said block including means for discriminating against S-polarization with respect to P-polarization without using Brewster angle windows; one of said mirrors being constructed and arranged to form a magnetic mirror comprising a magnetic, saturable, fast-switching layer and a magneto-optic layer coupled to said magnetic layer to introduce a non-reciprocal phase shift between said counter-propagating light beams while maintaining negligible non-reciprocal losses, said last named mirror including a substrate; conductors disposed within said substrate for generating rapidly switchable magnetic fields; said magnetically saturable layer having a well defined easy axis of magnetization perpendicular to said plane and disposed on the substrate; said separate magneto-optic layer disposed directly on the magnetically saturable layer; and a multilayer dielectric reflective stack disposed over the magneto-optic layer.

Claim 3

Dependent Claim 31 words

The magnetic mirror of claim 1 wherein said conductors comprise a first pair of parallel conductors and a second pair of parallel conductors disposed orthogonally to said first pair of conductors.

Claim 4

Dependent Claim 16 words

The laser gyro of claim 1 wherein the magnetically saturable layer is a low magnetostriction alloy.

Claim 5

Dependent Claim 28 words

The laser gyro as in claim 3 wherein said low magnetostriction alloy has magnetostriction values of less than about 5 ppm and preferably less than about 1 ppm.

Claim 6

Dependent Claim 30 words

The laser gyro of claim 3 wherein the magnetically saturable layer is nickel-iron alloy of composition between 80-84 atomic percent nickel and the balance iron and preferrably 83 percent nickel.

Claim 7

Dependent Claim 23 words

The laser gyro of claim 1 wherein the magnetically saturable layer is a magnetic Ni-Fe alloy having a thickness of from 400-2,000 Angstroms.

Claim 8

Dependent Claim 24 words

The laser gyro of claim 1 wherein said magnetically saturable layer is a metal alloy consisting of Ni-Fe alloys of composition 80-84 percent nickel.

Claim 9

Dependent Claim 49 words

The laser gyro of claim 1 wherein said magneto-optic layer is made of a metal alloy selected from the group consisting of (a) Co/Fe or composition about 45+/-5 atomic percent cobalt, (b) Si/Fe or composition about 10+/-5 atomic percent silicon, (c) iron, and (d) Ni/Co approx 50/50 atomic percent.

Claim 10

Dependent Claim 29 words

The laser gyro of claim 1 wherein the magneto-optic layer is made of an iron or iron silicon alloy of between 10+/-5 atomic percent silicon and the balance iron.

Claim 11

Dependent Claim 20 words

The laser gyro of claim 1 wherein the magneto-optic layer is iron and is less than about 200 Angstroms thick.

Claim 12

Dependent Claim 33 words

The laser gyro of claim 1 wherein the magneto-optic layer is a cobalt/iron alloy of approximate composition of 45+/-5 atomic percent cobalt, with the balance iron and a thickness of about 100-300 Angstroms.

Claim 13

Dependent Claim 31 words

The laser gyro of claim 1 wherein the magneto-optic layer is an iron/silicon alloy of approximate composition of about 12+/-5 atomic percent silicon and a thickness of about from 100-400 Angstroms.

Claim 14

Dependent Claim 51 words

Magnetic mirror comprising: a substrate; conductors disposed in said substrate for generating rapidly switchable magnetic fields; a magnetically saturable layer having a well defined easy axis of magnetization disposed on the substrate; a magneto-optic layer disposed directly on the magnetically saturable layer; and a multilayer dielectric stack over the magneto-optic layer.

Claim 15

Dependent Claim 51 words

Magnetic mirror comprising: a substrate; conductors disposed in said substrate for generating rapidly switchable magnetic fields; a magnetically saturable layer having a well defined easy axis of magnetization disposed on the substrate; a magneto-optic layer disposed directly on the magnetically saturable layer; and a multilayer dielectric stack over the magneto-optic layer.

Claim 16

Dependent Claim 16 words

The magnetic mirror of claim 13 wherein the magnetically saturable layer is a low magnetostriction alloy.

Claim 17

Dependent Claim 12 words

The magnetic mirror of claim 13 wherein the magneto-optic layer is iron.

Claim 18

Dependent Claim 14 words

The magnetic mirror of claim 13 where the magneto-optic layer is a cobalt/iron alloy.

Claim 19

Dependent Claim 20 words

The magnetic mirror of claim 13 wherein the magneto-optic layer is an iron/silicon alloy of about 10+/-5 atomic percent silicon.

Claim 20

Dependent Claim 31 words

The magnetic mirror of claim 13 wherein said conductors comprise a first pair of parallel conductors and a second pair of parallel conductors disposed orthogonally to said first pair of conductors.

Claim 21

Dependent Claim 12 words

The magnetic mirror of claim 14 wherein the alloy is Ni-Fe alloy.

Claim 22

Dependent Claim 76 words

The magnetic mirror of claim 13 wherein the multilayer dielectric stack includes a first stack of alternating high and low index of refraction materials separated from the magneto-optic layer by a matching layer; a second stack of alternating layers of a high and a low index of refraction material; and an additional layer separating said stacks, said additional layer being adjusted to cooperate with said two stacks to selectively discriminate against the S-polarization mode of propagation.

Claim 23

Dependent Claim 22 words

The magnetic mirror of claim 20 wherein the alternating high and low index of refraction materials are titanium dioxide and silicon dioxide.

Claim 24

Dependent Claim 42 words

The magnetic mirror of claim 20 wherein the layers in the first stack have an optical thickness of 0.2653 and the layers in the second stack have an optical thickness of 0.2228 and the separating layer has an optical thickness of 0.0689

Claim 25

Dependent Claim 194 words

Laser gyro comprising: a gyro block including a block of material having bores therein at least partially defining a closed laser beam path lying in a plane; means for completing the laser beam path entirely enclosed within said block including a plurality of mirrors, each of which is contacted to the gyro block at he intersection of said bores to form a closed optical cavity therewith and laser beam path entirely enclosed within the block and mirrors and sealed to the block to form a laser gas containment cavity; means for generating counter-rotating laser beams within the cavity; said path being free of intracavity elements so that the beam travels unimpeded through the bores by reflection from the mirrors; said block including means for discriminating against S-polarization with respect to P-polarization without using Brewster angle windows and including an odd number of mirrors and having a perimeter selected to produce a large frequency splitting between S- and P modes whereby S mode lasing is suppressed, and one of said mirrors being constructed and arranged to form a magnetic mirror to introduce a non-reciprocal phase shift between counter-propagating light beams while introducing negligible non-reciprocal losses.

Claim 26

Dependent Claim 194 words

Laser gyro comprising: a gyro block including a block of material having bores therein at least partially defining a closed laser beam path lying in a plane; means for completing the laser beam path entirely enclosed within said block including a plurality of mirrors, each of which is contacted to the gyro block at he intersection of said bores to form a closed optical cavity therewith and laser beam path entirely enclosed within the block and mirrors and sealed to the block to form a laser gas containment cavity; means for generating counter-rotating laser beams within the cavity; said path being free of intracavity elements so that the beam travels unimpeded through the bores by reflection from the mirrors; said block including means for discriminating against S-polarization with respect to P-polarization without using Brewster angle windows and including an odd number of mirrors and having a perimeter selected to produce a large frequency splitting between S- and P modes whereby S mode lasing is suppressed, and one of said mirrors being constructed and arranged to form a magnetic mirror to introduce a non-reciprocal phase shift between counter-propagating light beams while introducing negligible non-reciprocal losses.

Claim 27

Dependent Claim 28 words

The magnetic mirror of claim 23 having a perimeter less than 30 centimeters and operating on the 1.15 micron transition of neon in a helium neon lasing medium.

Claim 28

Dependent Claim 113 words

In a ring laser gyro with no intracavity elements a polygonal block, means forming mirror supporting facets formed at the apexes of the polygon, means forming a plurality of passages between facets to define a planar path cavity whose length is such that the frequency separation between S and P modes is at least greater than the half width of the laser gain curve for the P mode, means forming a plurality of mirrors mounted to said facets one of which is a pathlength control mirror, one of which is a magnetic mirror which utilizes the transverse Kerr magneto-optic effect to achieve a magnetic bias; and one of which is a readout mirror.

Claim 29

Dependent Claim 113 words

In a ring laser gyro with no intracavity elements a polygonal block, means forming mirror supporting facets formed at the apexes of the polygon, means forming a plurality of passages between facets to define a planar path cavity whose length is such that the frequency separation between S and P modes is at least greater than the half width of the laser gain curve for the P mode, means forming a plurality of mirrors mounted to said facets one of which is a pathlength control mirror, one of which is a magnetic mirror which utilizes the transverse Kerr magneto-optic effect to achieve a magnetic bias; and one of which is a readout mirror.

Claim 30

Dependent Claim 15 words

The ring laser gyro of claim 25 further including: means to control the laser polarization.

Claim 31

Dependent Claim 32 words

The ring laser gyro of claim 26 further including a polarizer between the pathlength control beam and the pathlength control detector; the polarizer is oriented parallel to the plane of the laser.

Claim 32

Dependent Claim 28 words

The ring laser gyro of claim 26 further including a polarization selective mirror whose reflectance for P polarized light is greater than the reflectance for S polarized light.

Claim 33

Dependent Claim 29 words

The ring laser gyro of claim 25 in which said magnetic mirror has its magnetization vector set normal to the laser plane and in the plane of the mirror.

Claim 34

Dependent Claim 64 words

The ring laser gyro of claim 25 further including magnetic mirror means including magnetic coils located in close proximity to the coating of the magnetic mirror to act on the material of the magnetic mirror but located external to the cavity, said coils being constructed and arranged to give a magnetic field primarily parallel to the mirror plane, and perpendicular to the laser plane.

Claim 35

Dependent Claim 34 words

The ring laser gyro of claim 30 in which the magnetic field of one coil is perpendicular to the laser plane and the magnetic field of another coil is parallel to the laser plane.

Claim 36

Dependent Claim 29 words

The ring laser gyro of claim 30 in which the magnetic field of the coil is skew to the easy axis of the magnetic mirror to facilitate rotational switching.

Claim 37

Dependent Claim 42 words

The ring laser gyro of claim 30 further including an electronic drive system to provide a current sufficient to drive the magnetic coating into saturation in a direction perpendicular to the plane of the laser and in the plane of the mirror.

Claim 38

Dependent Claim 37 words

The ring laser gyro of claim 30 further including current which produces a field greater than the coercive force so as to switch the magnetization of the coating to both the positive and negative direction of magnetization.

Claim 39

Dependent Claim 50 words

The ring laser gyro of claim 30 further including a periodic or aperiodic pulsed current which produces a field less than the coercive force perpendicular to the laser plane, and simultaneously a pulse in another coil which produces a transverse field so as to induce rotational switching of the magnetization.

Claim 40

Dependent Claim 57 words

The ring laser gyro as in claim 35 including a polarization selective mirror the dielectric coating of which has two sets of layer pairs separated by a spacer layer such that at the laser wavelength and at the gyro angle of incidence the reflectance for P polarized light is greater than the reflectance for SL polarized light.

Claim 41

Dependent Claim 18 words

The ring laser gyro as in claim 25 further including means for controlling the off-axis S mode polarization.

Claim 42

Dependent Claim 33 words

The ring laser gyro as in claim 37 in which said controlling means includes means forming an elliptical aperature placed around the beam path so as to block said off-axis S mode beam.

Claim 43

Dependent Claim 175 words

Laser gyro comprising: a gyro block including a block of material having bores therein at least partially defining a closed laser beam path lying in a plane; means for completing the laser beam path entirely enclosed within said block including a plurality of mirrors, each of which is contacted to the gyro block at the intersection of said bores to form a closed optical cavity therewith. The laser beam path entirely enclosed within the block and mirrors and sealed to the block to form a laser gas containment cavity; means for generating counter-propagating laser beams within the cavity; said path being free of intracavity elements so that the beam travels unimpeded through the bores by reflection from the mirors; one of said mirrors having high reflectance and including constructive and destructive interference means for discriminating against S-polarization with respect to P-polarization without using Brewster angle windows; one of said mirrors being constructed and arranged to form a magnetic mirror to introduce a non-reciprocal phase shift between said counter-propagating light beams while maintaining negligible non-reciprocal losses.

Claim 44

Dependent Claim 175 words

Laser gyro comprising: a gyro block including a block of material having bores therein at least partially defining a closed laser beam path lying in a plane; means for completing the laser beam path entirely enclosed within said block including a plurality of mirrors, each of which is contacted to the gyro block at the intersection of said bores to form a closed optical cavity therewith. The laser beam path entirely enclosed within the block and mirrors and sealed to the block to form a laser gas containment cavity; means for generating counter-propagating laser beams within the cavity; said path being free of intracavity elements so that the beam travels unimpeded through the bores by reflection from the mirors; one of said mirrors having high reflectance and including constructive and destructive interference means for discriminating against S-polarization with respect to P-polarization without using Brewster angle windows; one of said mirrors being constructed and arranged to form a magnetic mirror to introduce a non-reciprocal phase shift between said counter-propagating light beams while maintaining negligible non-reciprocal losses.

Claim 45

Dependent Claim 83 words

The laser gyro of claim 39 wherein the high reflectance mirror comprises a first multilayer dielectric stack including alternating layers of a high and a low index of refraction material, a second stack of alternating layers of high and low index of refraction material, and an additional layer separating the first and second stacks, said additional layer being adjusted to cooperate with said stacks to constructively and destructively interfere with the passing beams to thereby selectively discriminate against the S-polarization mode of propagation.

Claim 46

Dependent Claim 42 words

The laser gyro of claim 40 wherein the layers of the first stack have an optical thickness of 0.285 and the layers of the second stack have an optical thickness of 0.25 separated by a layer having an optical thickness of 0.114.

Claim 47

Dependent Claim 24 words

The laser gyro of claim 40 wherein the first stack includes seven pairs of layers and the second stack includes eight pairs of layers.

Claim 48

Dependent Claim 186 words

Laser gyro comprising: a gyro block including a block of material having bores therein at least partially defining a closed laser beam path lying in a plane; means for completing the laser beam path entirely enclosed within said block including a plurality of mirrors, each of which is contacted to the gyro block at the intersection of said bores to form a closed optical cavity therewith and laser beam path entirely enclosed within the block and mirrors and sealed to the block to form a laser gas containment cavity; means for generating counter-propagating laser beams within the cavity; said path being free of intracavity elements so that the beam travels unimpeded through the bores by reflection from the mirrors; one of said mirrors including constructive and destructive interference means for discriminating against S-polarization with respect to P-polarization without using Brewster angle windows; one of said mirrors being constructed and arranged to from a magnetic mirror comprising a magnetic, saturable, fast-switching layer and a magneto-optic layer coupled to said magnetic layer to introduce a non-reciprocal phase shift between said counter-propagating light beams while introducing negligible non-reciprocal losses.

Claim 49

Dependent Claim 186 words

Laser gyro comprising: a gyro block including a block of material having bores therein at least partially defining a closed laser beam path lying in a plane; means for completing the laser beam path entirely enclosed within said block including a plurality of mirrors, each of which is contacted to the gyro block at the intersection of said bores to form a closed optical cavity therewith and laser beam path entirely enclosed within the block and mirrors and sealed to the block to form a laser gas containment cavity; means for generating counter-propagating laser beams within the cavity; said path being free of intracavity elements so that the beam travels unimpeded through the bores by reflection from the mirrors; one of said mirrors including constructive and destructive interference means for discriminating against S-polarization with respect to P-polarization without using Brewster angle windows; one of said mirrors being constructed and arranged to from a magnetic mirror comprising a magnetic, saturable, fast-switching layer and a magneto-optic layer coupled to said magnetic layer to introduce a non-reciprocal phase shift between said counter-propagating light beams while introducing negligible non-reciprocal losses.

Claim 50

Dependent Claim 109 words

The laser gyro of claim 43 wherein the magnetic mirror comprises a substrate including conductors for generating rapidly switchable magnetic field; said magnetically saturable layer being disposed on the substrate; said magneto-optic layer being disposed directly on the magnetically saturable layer; and further including a first stack of alternating layers of a high and a low index of refraction dielectric material disposed on the magneto-optic layer; a second stack including alternating layers of a high and a low index of refraction material; and an additional layer separating said stacks, said additional layer being adjusted to cooperate with said two stacks to selectively discriminate against the S-polarization mode of propagation.

Claim 51

Dependent Claim 47 words

The laser gyro of claim 44 wherein the stacks of alternating layers are made of silicon dioxide and titanium dioxide and wherein the layers in the second stack have an optical thickness of 0.2228 separated by a layer of titanium dioxide having an optical thickness of 0.0689.

Claim 52

Dependent Claim 70 words

The laser gyro of claim 43 wherein the magnetic mirror comprises a substrate; conductors disposed within said substrate for generating rapidly switchable magnetic fields, said magnetically saturable layer having a well defined easy axis of magnetization perpendicular to said plane and disposed on the substrate, said magneto-optic layer disposed directly on the magnetically saturable layer, and said interference means comprising a multilayer dielectric reflective stack disposed over the magneto-optic layer.

Claim 53

Dependent Claim 17 words

The laser gyro as in claim 16 wherein the magnetically saturable layer is a low magnetostriction alloy.

Claim 54

Dependent Claim 13 words

The laser gyro as in claim 46 wherein the magnetic-optic layer is iron.

Claim 55

Dependent Claim 15 words

The laser gyro as in claim 46 where the magneto-optic layer is a cobalt/iron alloy.

Claim 56

Dependent Claim 21 words

The laser gyro as in claim 46 wherein the magneto-optic layer is an iron/silicon alloy of about 10+/-5 atomic percent silicon.

Claim 57

Dependent Claim 15 words

The laser gyro as in claim 46 wherein the magnetically saturable layer is Ni-Fe alloy.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1993-11-05	1994-05-07	1994-11-06	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1997-11-05	1998-05-07	1998-11-06	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2001-11-05	2002-05-07	2002-11-06	$7700.00	Window Closed / Lapsed

Ring laser gyro and magnetic mirror therefor

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