EXHIBIT 2165
`EXHIBIT 2165
`
`
`
`

`
`United States Patent
`Wentz
`
`[19]
`
`[54] DIELECTRIC POLARIZER FOR HIGH
`AVERAGE AND HIGH PEAK POWER
`OPERATION
`Inventor:
`John L. Wentz., Ellicott City, Md.
`[75]
`[73] Assignee: Westinghouse Electric Corp.,
`Pittsburgh, Pa.
`Appl. No.: 434,191
`Oct. 13, 1982
`Filed:
`Int. C1.3
`U.S. Cl
`[58] Field of Search
`
`GO2B 5/30
`350/395; 350/164
`350/395, 164, 1.6;
`372/106
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`4,179,190 12/1979 Friedman et al.
`4,229,066 10/1980 Rancourt et al.
`7/1984 Sato et al.
`4,461,532
`Primary ExaminerJohn K. Corbin
`Assistant ExaminerLynn Vandenburgh Kent
`
`350/394
`350/1.6
`350/1.6
`
`Patent Number:
`[11]
`[45] Date of Patent:
`
`4,515,441
`May 7, 1985
`
`Attorney, Agent, or FirmW. G. Sutcliff
`ABSTRACT
`[57]
`A dielectric optical polarizer which is operable at high
`peak and average power, with greater than 95 percent
`transmission of the desired P polarized radiation, and
`also greater than 95 percent reflectance of the S polar-
`ized radiation. The polarizer comprises a radiation
`transmissive substrate with a first dielectric layer dis-
`posed on at least one side of the substrate. The first
`dielectric layer has an index of refraction higher than
`the substrate. A second dielectric layer of low index of
`refraction material is disposed atop the first dielectric
`layer. A third dielectric layer of the same high index of
`refraction material as the first layer, is disposed atop the
`second layer. Each of the dielectric layers is one quarter
`wavelength thick at the operating wavelength. The
`dielectric polarizer operates at a very high Brewster
`angle associated with the dielectric layers rather than
`that of the substrate.
`
`6 Claims, 2 Drawing Figures
`
`79°
`
`IMEn Mg I NM
`
`e,
`
`20
`
`A
`
`26a
`
`24a
`
`22a
`
`22b
`
`24b
`
`26
`
`Masterlmage 3D, Inc. and Masterlmage 3D Asia, LLC - Exhibit 1005
`
`REALD INC.
`Exhibit 2165-1
`MASTERIMAGE 3D, et al. v REALD INC.
`IPR2015-00035
`
`

`
`U.S. Patent
`
`May7,1985
`
`4,515,441
`
`BREWSTER ANCLE
`
`10
`
`16
`
`2
`
`14
`
`FIG.I
`
`20
`
`FIG.2
`
`,
`
`A
`Zi1101 MI LOW
`I 1110 .
` 1 EN I E I II BM 1
`mmmmmm
`
`7E
`
`260-\
`
`24a
`
`22a
`
`22b
`
`24b
`
`26b
`
`MasterImage 3D, Inc. and MasterImage 3D Asia, LLC - Exhibit 1005
`
`REALD INC.
`Exhibit 2165-2
`MASTERIMAGE 3D, et al. v REALD INC.
`IPR2015-00035
`
`

`
`1
`
`DIELECIRIC POLARIZER FOR HIGH AVERAGE
`AND HIGH PEAK POWER OPERATION
`
`4,515,441
`
`2
`quartz or fused silica. The fused quartz substrate mate-
`rial is typically used because of its high optical damage
`threshold and low absorption at visible and near infra-
`red wavelengths. For laser systems which exhibit both
`a high peak power density and a high average power
`density, the prior art dielectric polarizers have been
`found to be consistently damaged during such opera-
`tion. By high peak power density, we are referring to
`power levels in excess of 100 megawatts per square
`centimeter, and for high average power density refer-
`ring to in excess of 100 watts per square centimeter. It is
`believed that such multi-layer dielectric polarizers are
`damaged due to localize heating in the multiple layers
`due to multiphoton absorption.
`SUMMARY OF THE INVENTION
`An optical polarizer is disclosed which operates at
`high peak and high average power operation with a
`high Brewster angle for incident radiation to permit
`such operation without damage to the polarizer. The
`optical polarizer exhibits an efficiency of transmission
`of the polarized radiation at greater than about 95%,
`with the efficiency of reflection for the oppositely or
`orthogonally polarized radiation also being greater than
`about 95%. The optical polarizer comprises an optically
`transmissive substrate having a predetermined index of
`refraction, and has a plurality of quarter wavelength
`thick optically transmissive dielectric parallel layers
`disposed on at least one side of the substrate. A first
`dielectric layer is disposed on the substrate and has a
`high index of refraction relative to the substrate. A
`second dielectric layer is disposed atop the first layer
`and has a relatively low index of refraction relative to
`the index of the first dielectric layer. A third dielectric
`layer is disposed atop the second layer and comprises
`the same dielectric material as the first layer.
`The preferred optical polarizer of the present inven-
`tion utilize a fused quartz substrate with three dielectric
`layers disposed on each side of this optically transmis-
`sive fused quartz substrate. The first and third dielectric
`layers disposed upon the substrate comprising zinc sul-
`fide, and the second dielectric layer sandwiched be-
`tween the first and third dielectric layer comprises mag-
`nesium fluoride. The three dielectric layers are each one
`quarter wavelength thick.
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 is a schematic representation which illustrates
`polarization at the Brewster angle for incident radia-
`tion.
`FIG. 2 is a side elevational view in section of an
`optical polarizaer of the present invention.
`DETALL,ED DESCRIPTION OF THE
`INVENTION
`FIG. 1 illustrates how unpolarized incident radiation
`represented by ray 10 is separated by polarization means
`12 into a P polarized beam 14, which is linearly polar-
`ized parallel to the plane of incidence and is transmitted
`at Brewster's angle, and an S polarized beam 16 which
`is linearly polarized perpendicular to the plane of inci-
`dence and is the reflected polarization at Brewster's
`angle. This illustration presupposes that the mediums on
`either side of the polarization means 12 have differing
`indices of refraction.
`The dielectric polarizer 18 of the present invention is
`illustrated in detail in FIG. 2. The dielectric optical
`polarizer 18 comprises a fused quartz substrate 20,
`
`5
`
`15
`
`The U.S. Government has rights in the present inven-
`tion as a result of work performed under Air Force
`Contract No. F33615-80-C-1055.
`BACKGROUND OF THE INVENTION
`The present invention relates to optical polarizers, 10
`and more particularly polarizers which operate at a
`high peak and average power. Many electro-optical
`systems require polarization of incident radiation to
`permit further processing of the transmitted polarized
`optical radiation.
`Prior art optical polarizers have utilized a wire grid
`disposed on a transmissive substrate for separating the
`two orthogonal components of the unpolarized input
`radiation. Other optical polarizers utilize birefringent
`crystalline materials or multiple dielectric coatings on 20
`transnaissive substrates to obtain efficient polarizer op-
`eration. The Brewster angle of the polarizer is the angle
`of maximum polarization with respect to incident radia-
`tion, and is defined by the equation tan i=n, wherein i
`is the angle of incidence, and n is the index of refraction 25
`of the material. Techniques for polarizing input or inci-
`dent radiation rely for the most part on Brewster's angle
`operation to separate unpolarized optical radiation into
`two orthogonal components. The component of polar-
`ized transmitted radiation which is parallel to the plane 30
`of incidence is termed the P polarization and is transmit-
`ted at Brewster's angle. The orthogonal S component of
`polarization is that which is linear/y polarized perpen-
`dicular to the plane of incidence and is the reflected
`polarization at Brewster's angle.
`Prior art polarizers which utilize dielectric coatings
`are known to be far superior to birefringent crystalline
`polarizers with regard to average power handling capa-
`bility as a result of a lower radiation absorption charac-
`teristic and by virtue of the absence of thermo-optic 40
`distortion. Multi-layered dielectric optical polarizers
`are illustrated in U.S. Pat. No. 3,704,934, which teaches
`a multi-layered dielectric coating between two prisms
`of a beam splitter to assure high reflectance for the S
`polarization component and high transmittance for the 45
`P polarization component. The teaching is to utilize
`about 15 layers of quarter wavelength thick alternating
`layers of high index of refraction material and low index
`of refraction material such as cerium oxide and magne-
`sium fluoride. In another prior art dielectric polarizer as 50
`seen in U.S. Pat. No. 4,009,933, the dielectric coating is
`composed of alternate quarter wavelength thick layers
`of two dielectric materials such as zinc sulfide and tho-
`rium fluoride which have significantly different indices
`of refraction. The teaching is for the dielectric coating 55
`to have a sufficient number of layers to reflect most of
`the light before transmission. This is a reflectivity de-
`sign which is 99% effective for polarization perpendicu-
`lar to a grating which is disposed on a substrate over
`which the dielectric layers are disposed and which is 60
`92% reflective for parallel polarization.
`With the development of high power laser systems
`the need has arisen for dielectric polarizers capable of
`handling high average and high peak power laser radia-
`tion. The prior art dielectric polarizer designs which 65
`have utffized multi-layer coatings of, for example, 15 to
`30 layers serve to enhance the polarization characteris-
`tics of the substrate material which is typically fused
`
`35
`
`Masterlmage 3D, Inc. and Masterlmage 3D Asia, LLC - Exhibit 1005
`
`REALD INC.
`Exhibit 2165-3
`MASTERIMAGE 3D, et al. v REALD INC.
`IPR2015-00035
`
`

`
`5
`
`35
`
`4,515,441
`
`3
`which efficiently transmits the incident radiation which
`is utilized. By way of example the fused quartz substrate
`is about 0.5 mm. thick and the radiation may be infrared
`radiation such as the 1.06 micrometer radiation output
`from a neodymium doped YAG laser. A first dielectric
`layer 224 and 22b is disposed on each side of the quartz
`substrate 20. A second dielectric layer 24a, 24b is dis-
`posed respectively upon the first dielectric layers 22a
`and 22b. A third dielectric layer 26a, 26b is then dis-
`posed respectively atop the second dielectric layers 24a,
`24b. Each of the dielectric layers 22a through 26a and
`22b through 26b are approximately a quarter wave-
`length thick at the input radiation wavelength and inci-
`dent angle. The fused quartz substrate 20 has an index of
`refraction of approximately 1.45 at 1.06 micrometer
`wavelength. The first dielectric layers 22a and 22b are
`formed of relatively high index of refraction material,
`such as zinc sulfide, which has an index of refraction of
`approximately 2.3 at 1.06 micrometer wavelength. The
`second dielectric layers 24a and 24b are formed of rela- 20
`tively low index of refraction material such as magne-
`sium fluoride which has an index of refraction of ap-
`proximately 1.38 at 1.06 micrometer wavelength. The
`third dielectric layers 26a and 26b are again formed of
`high index of refraction material such as zinc sulfide 25
`which matches that of the first dielectric layer and has
`an index of refraction of approximately 2.3 at 1.06 mi-
`crometer wavelength. The provision of a high index of
`refraction dielectric layer determines that the polarizer
`will have a high Brewster angle of operation. For the 30
`embodiment specifically described above, the Brewster
`angle is 79° which is at a high grazing angle of inci-
`dence, which would not normally be expected to be
`utilized where efficient transmission of polarized energy
`is desired. However, for this embodiment, the desired
`transmitted P polarized radiation is better than 95 per-
`cent efficient and the efficiency of reflection of the S
`polarized radiation is also greater than 95 percent.
`The dielectric polarizer of the present invention thus
`utilizes a high Brewster angle for the incident radiation, 40
`and the power density incident on the polarizer is thus
`approximately 3 times less than that incident on prior
`art dielectric polarizers which utilize a low angle of
`incidence. That low angle is approximately 55 degrees
`for commercially available dielectric polarizers which 45
`use fused quartz substrates. The large Brewster angle of
`the polarizer of the present invention results in reduced
`incident power density by virtue of the greatly in-
`creased spot size of the incident beam.
`The dielectric polarizer of the present invention thus 50
`utilizes a significantly larger polarizing angle, i.e., a
`Brewster angle of greater than 750, and a significantly
`fewer number of dielectric layers than the prior art
`designs. The specific embodiment of the present inven-
`tion utilizing only three dielectric layers compared to 55
`the 15 to 30 layers for prior art designs.
`Other dielectric materials such as titanium dioxide
`and silicon dioxide can be substituted for the respective
`high index of refraction first and third dielectric layers
`and the low index of refraction second dielectric layer. 60
`The fused quartz substrate can also be substituted for
`with other radiation transmissive materials that are
`undamaged by the high power operation.
`It should be emphasized that the present invention
`dielectric polarizer operates at the Brewster angle of the 65
`high refractive index dielectric layer rather than the
`
`4
`Brewster angle associated with the substrate. The prior
`art multi-layer dielectric polarizers continued to make
`use of the Brewster angle associated with the substrate
`and thus used a low angle of incidence.
`In the embodiment seen of FIG. 2, the plurality of
`dielectric layers is shown disposed on both sides of the
`substrate, which is the embodiment as tested for appli-
`cation as a four port polarizer. It should be understood
`that a dielectric polarizer per the present invention need
`10 only have the dielectric layers on one side of the sub-
`strate. An anti-reflective means may then be provided
`on the opposed side of the substrate for efficient trans-
`mission of P polarized radiation from the substrate to
`the adjacent medium.
`15 What is claimed is:
`An optical polarizer which operates at high peak
`and average power density operation, with a high
`Brewster angle of greater than 75 degrees for incident
`radiation to permit such operation without damage to
`the polarizer, with the efficiency of transmission of the
`polarized radiation being greater than about 95%, and
`the efficiency of reflection for the orthogonally polar-
`ized radiation being greater than about 95%, which
`polarizer comprises;
`an optically transmissive substrate having a predeter-
`mined index of refraction,
`a plurality of quarter wavelength thick optically
`transmissive dielectric parallel layers disposed on
`at least one side of the substrate, with a first dielec-
`tric layer disposed on the substrate and having a
`high index of refraction relative to the substrate,
`with a second dielectric layer atop the first layer
`and having a relatively low index of refraction
`relative to the index of the first dielectric layer, and
`a third dielectric layer atop the second layer which
`third comprises the same dielectric material as the
`first layer.
`The optical polarizer set forth in claim 1, wherein
`the optically transmissive substrate is fused quartz.
`The optically polarizer set forth in claim 1, wherein
`the three dielectric layers are disposed on each side of
`the optically transmissive substrate.
`The optical polarizer set forth in claim /, wherein
`the first and third dielectric layers comprise zinc sulfide.
`The optical polarizer set forth in claim 1, wherein
`the second dielectric layer comprises magnesium fluo-
`ride.
`An optical polarizer which operates at a high
`Brewster angle of greater than 75 degrees for incident
`radiation to permit reduced incident power density for
`both peak and average power operation, with the effi-
`ciency for the transmitted polarized radiation being
`greater than about 95 percent, and the efficiency of
`reflection for the polarized reflected radiation being
`greater than about 95 percent, which polarizer com-
`prises;
`an optically transmissive fused quartz substrate,
`a first dielectric quarter wavelength layer of zinc
`sulfide disposed on both sides of the substrate,
`a second dielectric quarter wavelength layer of
`magnesium fluoride disposed on the first dielectric
`layers, and
`a third dielectric quarter wavelength layer of zinc
`sulfide disposed on the second dielectric layers.
`*
`*
`*
`*
`*
`
`Masterlmage 3D, Inc. and Masterlmage 3D Asia, LLC - Exhibit 1005
`
`REALD INC.
`Exhibit 2165-4
`MASTERIMAGE 3D, et al. v REALD INC.
`IPR2015-00035