KR20220097338A - Method for Preparing Continuous-phase Geometric phase Diffractive Optical Elements from Discrete-phase Geometric phase Diffractive Optical Elements - Google Patents

Abstract

In the present disclosure, a discontinuous low-resolution geometric phase diffractive optical element manufactured by applying (or coating) an anisotropic medium to a grating pixel array is used as a mask, and described is a method for mass-manufacturing high-resolution geometric phase diffractive optical elements having high phase freedom and continuous high-resolution polarization patterns generated by interference of beams polarized in left and right circles.

Description

Method for Preparing Continuous-phase Geometric phase Diffractive Optical Elements from Discrete-phase Geometric phase Diffractive Optical Elements

The present disclosure relates to a method of fabricating a continuous geometric phase diffractive optical element from discrete geometric phase diffractive optical elements (GP-DOE). More specifically, the present disclosure uses a discontinuous low-resolution geometric phase diffraction optical element manufactured by applying (or coating) an anisotropic medium to a grating pixel array as a mask, but polarized in left and right circles. The present invention relates to a method for mass-manufacturing a high-resolution geometric phase diffraction optical element with a high degree of phase freedom and continuous high-resolution through a polarization pattern generated as a result of the interference of a beam.

A diffractive optical element (DOE) is an element that uses a diffraction phenomenon by a periodic structure rather than refraction or reflection to control light in an optical system. The implementation principle is based on a phenomenon in which, when a single wavefront is divided into a plurality of small wavefronts, mutual constructive interference occurs when the optical path stop of the merged wavefronts corresponds to an integer multiple of the wavelength. Diffraction optics can be used in kinoform (the phase control plane shows continuous changes), binary optics (binary optics; the phase control plane shows discontinuous changes), and computergenerated holograms (by reducing the interference pattern calculated as a series of phase or magnitude masks). manufactured), HOE (holographic optical elements; manufactured by recording the interference fringes of two wavefronts in a photosensitive material that is typically 5 to 30 μm thick to create an optical component), diffraction gratings, etc. Various forms have been reported.

Conventionally, as a method of manufacturing a diffractive optical element, a method of manufacturing a surface relief diffractive optical element and a geometric phase diffractive optical element is largely known.

In the former case, a shape is formed on the surface by a machining method. Such a geometric phase diffraction optical device is manufactured by orienting the optical axis direction by Mach-Zehnder interferometry, direct-writing method, etc. it is common to be However, in the surface relief diffraction optical device, the manufacturing area is limited to the paraxial region due to processing reasons such as the precision limit of machining and the stability of the lithography process, and the efficiency reduction and high-order noise according to the process are problematic.

In particular, the Mach-Zehnder interference method forms a pattern by allowing a polarized beam to pass through two optical paths perpendicular to each other, and controlling the optical axis rotation in the sample by placing a designed phase distribution in one of the optical paths. This method is excellent in terms of productivity because a pattern can be formed by one exposure, but an arbitrary phase distribution cannot be freely implemented because the achievable optical axis rotation pattern is limited to the phase distribution of the object that can be manufactured.

On the other hand, in the case of the direct recording method, the optical axis rotation is controlled by irradiating different polarized beams onto the sample each time it passes one pixel position while moving the sample to the stage, and a different phase is formed at each pixel position. Therefore, the degree of freedom of the phase distribution is good, but since all positions on the sample are processed sequentially, there is a limitation in that the processing time becomes very long depending on the area.

As a solution to the above-mentioned disadvantages of the surface relief diffraction optical device, a study on a geometric phase diffraction optical device (GP-DOE), which is a device that does not require surface irregularities by forming a phase difference according to the arrangement direction of the birefringent material, is in progress. .

The geometric phase is a phenomenon in which a phase change additionally occurs due to a difference in the optical axis direction in an anisotropic medium or material, rather than a difference in the path of transmitted light depending on the structural shape as in the surface relief diffraction optical device. An optical element using such a geometric phase is referred to as a geometric phase diffraction optical element. In this regard, the geometric phase is twice the rotation angle of the optical axis when the optical axis of the anisotropic material is rotated at a certain angle under the condition that circularly polarized light is incident and the height condition satisfies the half-wave plate. This refers to a phenomenon in which the direction of circularly polarized light is reversed as the phase delay occurs.

In the case of a geometric phase diffraction optical device, it is very thin with a thickness of several μm, and has the advantage of a perfectly planar structure with the same thickness at all locations, and is useful in fields requiring miniaturization and weight reduction.

However, in spite of many advantages, the geometric phase diffraction optical device studied so far still has problems in the manufacturing process, such as problems of the prior art, for example, limitations in productivity improvement, and a solution to this is required.

In one embodiment of the present disclosure, it is intended to provide a manufacturing method capable of overcoming the limitations of the manufacturing process problematic in the prior art, and capable of mass replicating a geometric phase diffraction optical element having continuous and high resolution.

The problems to be solved according to the embodiments of the present specification are not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the description below.

According to the first aspect of the present disclosure,

a) manufacturing a discontinuous low-resolution optical axis rotation pattern master formed by a diffraction grating arrangement;

b) manufacturing a discontinuous geometric phase diffraction optical element of a first resolution by orienting an anisotropic medium to the low-resolution discontinuous optical axis rotation pattern master;

c) using the discontinuous geometric phase diffraction optical element of the first resolution disposed at a predetermined distance on the substrate coated with the first photo-alignment material as a mask, and the period by which the linearly polarized beam is incident thereon manufacturing a continuous optical axis rotation pattern master of a second resolution by engraving a polarization pattern reduced in half into the first light-aligning material; and

d) applying an anisotropic medium to the continuous optical axis rotation pattern master of the second resolution to manufacture a continuous geometric phase diffraction optical element of the second resolution;

In this case, a method of manufacturing a continuous geometric phase diffractive optical element from a discontinuous geometric phase diffractive optical element is provided, wherein the second resolution has an increased value compared to the first resolution.

According to an exemplary embodiment, in step b) and step d), the anisotropic medium may be applied to have a thickness of half a wave plate.

According to an exemplary embodiment, in the step c), the separation distance between the discontinuous geometric phase diffraction optical element of the first resolution and the substrate to which the first photo-alignment material is applied is the formula

(Z is the separation distance, λ is the center wavelength of the irradiated UV light, Λ is the pattern period of the optical axis rotation pattern master, N is the number of diffraction gratings included in one period, and A is 90 or more and 110 or less) can

According to an exemplary embodiment, the anisotropic medium may be a reactive mesogen as a liquid crystal. However, the present invention is not limited thereto, and in some cases, the anisotropic medium may include a reactive mesogen. For example, the anisotropic medium may contain reactive mesogens and other materials that are anisotropic.

According to an exemplary embodiment,

e) using, as a mask, the continuous geometric phase diffraction optical element of the second resolution disposed at a predetermined distance on the substrate coated with the second light-aligning material, and injecting a linearly polarized beam thereto manufacturing a continuous optical axis rotation pattern master of a third resolution by engraving a polarization pattern reduced by ½ to the second light-aligning material; and

f) applying an anisotropic medium to the continuous optical axis rotation pattern master of the third resolution to manufacture a continuous geometric phase diffraction optical element of the third resolution; further comprising,

The third resolution may have an increased value compared to the second resolution.

Details of other embodiments are included in the detailed description and drawings.

The method of manufacturing a continuous high-resolution geometric phase diffraction optical device according to the present disclosure overcomes the disadvantages of the conventional manufacturing methods, such as the Mach-Zehnder interference method, the direct recording method, etc. Optical devices can be mass-produced, and in particular, by using a continuous geometric phase diffraction optical device that exhibits high light efficiency, integration and miniaturization can be achieved by applying it to various fields such as displays and AR glass, where product integration is important. In particular, it is advantageous for commercialization by adopting a relatively simple manufacturing method.

1 is an overall schematic diagram of a process for manufacturing a continuous geometric phase diffractive optical element from a discontinuous geometric phase diffractive optical element according to an embodiment;
2 is a flow chart illustrating a process for fabricating a discontinuous, low-resolution optical axis rotation pattern master using nanoimprinting techniques, in an exemplary embodiment;
Fig. 3 is a diagram schematically showing a discontinuous geometric phase diffractive optical element of a first resolution in an exemplary embodiment;
Fig. 4 is a diagram showing the phase delay when different circularly polarized light is incident on a geometric phase diffraction optical element;
Fig. 5 is a diagram showing the direction of linearly polarized light according to a distance when linearly polarized light is incident on a geometric phase diffraction optical element; and,
6 shows the computational simulation results for the separation distance for obtaining a continuous polarization interference fringe.

The present invention can all be achieved by the following description. It should be understood that the following description describes preferred embodiments of the present invention, but the present invention is not necessarily limited thereto. In addition, the accompanying drawings are provided to aid understanding, and the present invention is not limited thereto, and details regarding individual configurations may be properly understood by the specific purpose of the related description to be described later.

Terms used in this specification may be defined as follows.

“Liquid crystal” may refer to a material having properties such as anisotropic crystals while having fluidity.

A “wave plate” may refer to an optical element that changes the polarization state of light passing therethrough. When an electromagnetic wave passes through the wave plate, the polarization direction becomes the sum of two components (normal ray and extraordinary ray) that are parallel or perpendicular to the optical axis, and the vector sum of the two components changes depending on the birefringence and thickness of the wave plate. The later polarization direction is changed. In this case, a half-wave plate that changes the polarization direction of light by 90° may be referred to as a half-wave plate, and a plate that changes the polarization direction by 180° can be called a cold-wave plate.

Although "contacting" in a narrow sense means direct contact between two objects, it may be understood that any additional element may be interposed in a broad sense.

It may be understood that the expressions “on” and “on” are used to refer to the concept of relative position. Accordingly, not only the case where other components or layers are directly present in the mentioned layers, but also other layers (intermediate layers) or components may be interposed or present therebetween. Similarly, the expressions “under”, “under” and “below” and “between” may also be understood as relative concepts with respect to location. Also, the expression “sequentially” may be understood as a concept of relative position.

In the present specification, when a component is "included", it means that other components and/or steps may be further included, unless otherwise specified.

According to an embodiment of the present disclosure, there is provided a method capable of simultaneously securing a phase distribution with a high degree of freedom and high productivity compared to a conventional manufacturing technique of a geometric phase diffraction optical device.

A schematic implementation principle of a process for manufacturing a continuous geometric phase diffractive optical element from a discontinuous geometric phase diffractive optical element according to an embodiment is shown in FIG. 1 .

Referring to the drawings, first, a discontinuous low-resolution geometric phase diffraction optical element in which an anisotropic medium is oriented on a discontinuous optical axis rotation pattern master in which a grating pixel array is formed on a substrate is manufactured.

According to the illustrated embodiment, the substrate can be selected from a type having characteristics (specifically, transparency) through which light in the UV wavelength band can be transmitted, for example, UV transmission glass (Quartz, Sodalime), a transparent flexible substrate ( For example, it may be a thin glass or a plastic substrate) or the like.

In addition, according to the exemplary embodiment, the thickness of the substrate is not particularly limited, but as the substrate thickness increases, the transmittance of the UV wavelength band decreases, so depending on the UV absorption rate of the substrate, for example, from several hundred μm to several mm, specifically It may be determined in the range of about 01 to 10 mm. In addition, the diffraction grating array may be designed in consideration of the LC alignment force by the grating and the phase distribution to be fabricated.

According to an exemplary embodiment, as the horizontal and vertical (Px, Py) dimensions of one grid are smaller, the phase distribution can be expressed in detail, which is advantageous for device implementation. As an example, the size of the grating may be set in a range of approximately 1 μm to several tens of μm, for example, in a range of about 1 to 30 μm. Since the period and height of the lattice are related to the alignment force of the liquid crystal, the higher the lattice height and the smaller the period, the stronger the alignment force of the liquid crystal.

However, as the height of the diffraction grating increases, the effect of the diffraction grating rather than the effect on the liquid crystal occurs, so it is not preferable to set it unconditionally high. For example, the height of the grating is set to be less than 100 nm to be less than about 1/20 of the height of the liquid crystal, and the grating period can be set according to the orientation force in the range of about several hundred nm, specifically, in the range of about 200 to 800 nm. have.

Meanwhile, one of the advantages of this embodiment is that it is possible to fabricate a low-resolution, discontinuous optical axis rotation pattern master by forming a diffraction grating array on a substrate using a conventional technique known in the art.

In this regard, a schematic process for manufacturing a discontinuous low-resolution optical axis rotation pattern master using the nanoimprinting technique is shown in FIG. 2 .

In order to manufacture a transmissive device, a grating dot array is first formed on an opaque substrate, for example, a silicon wafer. In this case, the grid dot arrangement may be manufactured using a method known in the art, for example, a mechanical method using a diamond turning machine, electron beam (E-beam) lithography, interference lithography, or the like. In a specific embodiment, interference lithography can be applied because it is good in terms of large area and high speed. Since the technical details regarding the formation of the lattice dot arrangement are widely known in the art, the detailed description will be omitted.

Referring to FIG. 2 , a stamp resin (green) is dropped on an opaque substrate on which an opaque grid dot arrangement is formed, and a stamp film is attached. In this case, as the stamp resin, for example, an acrylic resin, a vinyl-ether resin, etc. may be used, and a flexible material such as a PET film may be used as the stamp film. Then, the lattice dot arrangement engraved on the stamp resin can be primarily cured by exposing it to ultraviolet light so that it can be attached to the film. In this case, the UV output may be, for example, about 5 to 30 mW, specifically about 10 to 20 mW, and the exposure time is, for example, about 1 to 10 seconds, specifically about 3 to 8 seconds within the range. Adjustable. Subsequently, after the resin for stamping is detached from the transferred film, secondary curing may be performed under UV irradiation conditions and/or baking conditions used in the primary curing process. As an example, UV irradiation may be performed for, for example, about 2 to 8 hours, specifically, about 3 to 7 hours, and baking is performed, for example, at about 70 to 95° C., specifically at about 75 to 90° C. It may be carried out over 0.5 to 4 hours, specifically, about 1 to 3 hours. As a result, a transferred stamp can be manufactured.

Thereafter, imprinting is performed on the molded resin (blue color) formed on the transmissive substrate (eg, glass substrate) using the transferred stamp, and again primary curing and secondary curing are performed on the impermeable substrate. The lattice dot arrangement structure formed on the lattice can be reproduced on the transmissive substrate.

The process and conditions for manufacturing the optical axis rotation pattern master described above are provided for illustrative purposes, and the present disclosure is not limited thereto. However, it is noteworthy that an optical axis rotation pattern with a high degree of freedom can be formed by adjusting the direction of the grid pattern, and in particular, it is advantageous for large-area and mass production by applying the conventional nanoimprinting technique. However, this master has a discontinuous phase distribution and low resolution.

According to an embodiment, manufacturing a low-resolution (first-resolution) discontinuous geometric phase diffraction optical device by orienting an anisotropic medium on a discontinuous low-resolution optical axis rotation pattern master is performed. In this regard, an example of a low-resolution discontinuous geometric phase diffraction optical element is shown in FIG. 3 .

In the illustrated embodiment, the anisotropic medium is colored red and oriented in a given thickness and direction. In an exemplary embodiment, the anisotropic medium may be a liquid crystal as a birefringent material, and specifically may be a reactive mesogen (RM). Reactive mesogen may refer to a material having a functional group that responds to light or heat at the terminal of the mesogenic molecule, that is, a mesogenic vinyl monomer, and specifically includes at least one mesogenic group and at least one polymerizable functional group bonded thereto It can mean a molecule that When the reactive mesogen is irradiated with light of a specific wavelength (eg, ultraviolet light), a chemical reaction such as a polymerization reaction occurs, thereby fixing optical anisotropy. Therefore, ultraviolet curing or the like can be performed after orientation. According to an exemplary embodiment, the reactive mesogen may be, for example, at least one compound selected from calamitic mesogen, discotic mesogen, and the like.

In this regard, as the anisotropic medium is rotated by ? from the optical axis, light passing through the anisotropic medium induces a geometricalphase delay by 2?. That is, when the polarized light passes through the reactive mesogens arranged in the grating direction, a phase delay of π may occur between the 0° and 90° directions.

Specifically, when light perpendicular to the x-axis and y-axis planes of an isotropic medium is incident, only a general phase delay occurs because there is no difference in refractive index with respect to the x-axis and y-axis directions of the medium (dynamic phase delay). When light is incident on an isotropic medium, a difference in refractive index occurs with respect to the major axis direction and the minor axis direction of the medium, and a term related to a dynamic phase as well as a term related to a geometric phase occurs according to the degree of rotation of these axes. In this case, when the dynamic phase term has a π value, it serves as a half-wave plate that converts the direction of the incident polarized light by 90°. The Jones matrix of the half-wave plate is expressed as in Equation 1 below.

[Equation 1]

)을 하기 수학식 4와 같이 수학식 3으로 표시되는 회전 매트릭스와 수학식 1로 표시되는 반파장판의 Jones 매트릭스의 곱으로 표현할 수 있기 때문에 매질을 통과한 광이 2Φ 만큼의 추가적인 위상 지연을 겪게 된다.If the long axis direction of the anisotropic medium performing the half-wave plate function is rotated by Φ from the y-axis, the characteristics of the anisotropic medium (

) can be expressed as the product of the rotation matrix represented by Equation 3 and the Jones matrix of the half-wave plate represented by Equation 1 as in Equation 4 below, so that the light passing through the medium experiences an additional phase delay of 2Φ. .

[Equation 2]

[Equation 3]

[Equation 4]

According to an exemplary embodiment, a discontinuous geometric phase diffraction optical element of low resolution (first resolution) according to Equation 5 below by applying an anisotropic medium or material to the above-described optical axis rotation pattern master to have a thickness of half a wave plate and orienting it can be manufactured.

[Equation 4]

In the above formula, δ is the phase delay, n ₀ is the refractive index in the long axis direction of the anisotropic medium, ne is the refractive index in the short axis direction of the anisotropic medium, and _d is the physical thickness of the anisotropic medium.

According to an exemplary embodiment, the orientation of the anisotropic medium can be performed by applying the microrubbing technique, and as shown in FIG. 3 , the anisotropic medium (specifically, reactive mesogen) is interposed between the microgroove structures. ), the anisotropic medium is aligned in one direction by the physical force applied by the microgroove structure to the anisotropic medium. Then, when the anisotropic medium is a reactive mesogen, a chemical reaction such as photopolymerization (or crosslinking) may be performed after application and alignment. Illustratively, the wavelength of light (specifically, ultraviolet light) irradiated during the photopolymerization reaction of an anisotropic medium may be set, for example, in the range of approximately 300 to 380 nm, and the output of the irradiated light is different for each material. One, for example, a mercury lamp (eg, approximately 20 mW) can be irradiated in less than one minute. However, these investigation conditions may be understood as illustrative.

As an example, when the refractive index of the anisotropic medium, specifically, the long-axis direction and the short-axis direction of the reactive mesogen is 1.680 and 1.543, respectively, and the wavelength of the transmitted light is 532 nm, using Equation 5 to function as a half-wave plate In order to do this, the thickness d of the anisotropic medium may be approximately 194 μm.

According to an embodiment, the discontinuous low-resolution (first-resolution) geometric phase diffraction optical element manufactured as described above is used as a mask (phase mask), and photo-aligning responding to a polarized beam ) After arranging the substrate coated with the material at a predetermined height (separation distance), the step of exposing the substrate by inputting a linearly polarized beam is performed. In this case, as shown in FIG. 1 , in the case of a substrate coated with a photo-alignment material, a photosensitive organic layer having anisotropic absorption ability is coated on the substrate. Illustratively, the substrate may be made of a transparent material, for example, UV-transmissive glass (Quartz, Sodalime), a transparent flexible substrate (eg, thin glass or plastic substrate.), and the like.

According to an exemplary embodiment, the photo-alignment material may use a material known in the art, for example, an azo-benzene-based material. An exemplary photo-alignment material may be represented by Formula 1 below.

[Formula 1]

The above-described light-aligning material is commercially available under trade names Brilliant Yellow (Tokyo Chemical Industry), LIA-CO01 (DIC corp) PAAD-22 (Beam co), and the like.

In an exemplary embodiment, the thickness of the photo-alignment layer applied on the substrate may be determined in consideration of the orientation force and the properties of the material, for example, may be in the range of about 10 to 500 nm.

In addition, the light-aligning material may be coated using methods known in the art, such as spray, spin coating, spray coating, dip coating, and the like.

According to the illustrated embodiment, the linearly polarized beam is irradiated and transmitted to the discontinuous low-resolution geometric phase diffraction optical element manufactured above, and as a result, the alignment direction of the anisotropic medium of the discontinuous low-resolution geometric phase diffraction optical element It can be inscribed in the light-aligning layer to be perpendicular or parallel to this polarization direction. As an example, light transmitted under a half-wavelength condition is used for photo-alignment, and the alignment direction of the wave plate may be transferred to the surface of the light-alignment layer. That is, as the linearly polarized beam passes through the discontinuous low-resolution geometric phase diffraction optical element, the left-circle and right-circle polarized beams interfere, and the polarization pattern formed thereby can be formed in the light-alignment layer.

According to an exemplary embodiment, the linearly polarized beam may be a laser beam, the wavelength may be, for example, in the range of about 300 to 380 nm, specifically about 320 to 370 nm, for example, an Nd:YAG laser , or a mercury lamp using a band pass filter. In addition, the intensity of the linearly polarized beam may adjust the output power and the irradiation time according to the required energy of the material of the light-aligning layer.

In the illustrated embodiment, the polarization pattern engraved on the light-alignment layer with a predetermined separation distance (or height) from the discontinuous low-resolution geometric phase diffraction optical element is continuous and a phase delay of twice the optical axis rotation angle appears. Due to its geometrical nature, the period is reduced by 1/2. As a result, a reduced pattern period, specifically, a half period polarization pattern is engraved on the light-aligning layer, wherein the engraved pattern is continuous and may exhibit improved resolution (second resolution) compared to the first resolution. As such, the light-aligned substrate engraved with a specific pattern by the linearly polarized beam can be used as a continuous optical axis rotation pattern master.

After that, the step of applying an anisotropic medium to the continuous optical axis rotation pattern master having a second resolution to have a thickness of a half-wave plate is performed, as a result, a geometric phase diffraction optical element having a continuous phase distribution of high resolution (second resolution) can be manufactured. In addition, the anisotropic medium used may be selected from the types listed above, and in this case, it may be the same as or different from the anisotropic medium used for manufacturing the discontinuous geometric phase diffraction optical element of the first resolution. In addition, the thickness of the anisotropic medium formed on the patterned light-aligning layer can be set to a height that functions as a half-wave plate in consideration of the birefringence, and a photopolymerization (or crosslinking) reaction can be subsequently performed. have.

According to an exemplary embodiment, the continuous geometric phase diffraction optical element of the second resolution may be applied to a desired application by itself, or alternatively, a more improved resolution may be obtained by performing an additional photo-alignment process using it as a mask. It is also possible to manufacture a continuous geometric phase diffraction optical element with Specifically, the third resolution ( It is possible to manufacture a continuous optical axis rotation pattern master with improved resolution compared to the second resolution). Subsequently, a continuous geometric phase diffraction optical device having a third resolution may be manufactured by applying an anisotropic medium.

Furthermore, using a continuous geometric phase diffraction optical element of third resolution as a mask, the steps of engraving a half-period polarization pattern on the above-described photo-alignment material and applying an anisotropic medium can be repeated n times. Bar, the resolution of the continuous geometric phase diffraction optical element manufactured in n times is increased compared to n-1 times. In this case, the number of n is determined according to, for example, distribution of a target phase, and a period that can be implemented is limited according to restrictions of the photo-alignment material and the anisotropic material.

On the other hand, in this embodiment, the discontinuous low-resolution geometric phase diffraction optical element (or high-resolution continuous geometric phase diffractive optical element) used as a mask (phase mask) has a coherence distance at which the polarization interference effect can occur well. It may be required to be spaced apart from the substrate on which the light-aligning layer is formed by a certain distance in which the discontinuous interference fringes are formed as continuous interference fringes.

In this regard, the separation distance may be determined using the principle related to the coherence distance of the light source and the Fraunhofer diffraction.

Since polarization interference occurs within the coherence of the light source, the separation distance must be within the coherence distance. The smaller the separation distance, the higher the coherence. However, when the separation distance is small, the polarization interference generated by passing through the discontinuous low-resolution geometric phase diffraction optical element is discontinuously formed. Therefore, in order to become a continuous polarization interference fringe, an appropriate diffraction propagation distance is required. If the separation distance is shorter than the proper diffraction propagation distance, a discontinuous polarization interference fringe is generated, whereas if the separation distance is longer than the proper diffraction propagation distance, the coherence becomes small and the signal of the interference fringe is reduced due to the excessively long diffraction propagation distance. noise ratio is lowered. As such, it is necessary to select an appropriate separation distance in order to secure a desired distinct polarization interference.

In this regard, a separation distance point suitable for a continuous phase can be expressed by applying the Fraunhofer diffraction equation in which the curvature of a spherical wave can be interpreted as a plane wave because it is sufficiently far from the wave source as shown in Equation 6 below.

[Equation 6]

In the above formula, Z is the separation distance, λ is the center wavelength of the irradiated UV light, Λ is a period (refer to FIG. 4), N is the number of diffraction gratings included in one period, and A is a constant value.

In particular, in Equation (6), a discontinuous phase plane forms a continuous phase at A is typically about 100 (more than 90 and less than or equal to 110). However, depending on the degree of light alignment of the optical system, A may have a slight change.

6 shows the computational simulation results for the separation distance for obtaining a continuous polarization interference fringe.

In Equation 6 using Virtual Lab, polarization interference fringes were obtained while varying A values for λ = 313 nm, Λ = 20 μm, and N = 4 or 8.

When A = 0, the separation distance is 0, and a discontinuous polarization interference fringe is generated.

In the case of A = 50, compared with the case of A = 0, the polarization interference fringes change continuously, but a discontinuous portion still remains.

When A = 100, a continuous polarization interference fringe was generated.

When A = 150, as in the case of A = 100, a continuous polarization interference fringe was generated. However, in terms of the signal-to-noise ratio, when A = 100, a higher signal-to-noise ratio of a polarized interference fringe can be obtained.

Although the embodiments of the present specification have been described in detail with reference to the accompanying drawings, the present specification is not necessarily limited to these embodiments, and various modifications may be made without departing from the technical spirit thereof. Therefore, the embodiments disclosed in the present specification are for explanation rather than limiting the technical spirit of the present invention, and the scope of the technical spirit of the present invention is not limited by these embodiments. Each feature of the various embodiments of the present invention may be partially or wholly combined or combined with each other, and may be technically variously linked and driven by those skilled in the art, and each embodiment may be implemented independently with respect to each other or related to each other may be carried out together. The protection scope of the present invention should be construed by the following claims, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present invention.

Claims (5)

a) manufacturing a discontinuous low-resolution optical axis rotation pattern master formed by a diffraction grating arrangement;
b) manufacturing a discontinuous geometric phase diffraction optical element of a first resolution by orienting an anisotropic medium to the low-resolution discontinuous optical axis rotation pattern master;
c) using the discontinuous geometric phase diffraction optical element of the first resolution disposed at a predetermined distance on the substrate coated with the first photo-alignment material as a mask, and the period by injecting a linearly polarized beam thereto manufacturing a continuous optical axis rotation pattern master of a second resolution by engraving a polarization pattern reduced in half into the first light-aligning material; and
d) applying an anisotropic medium to the continuous optical axis rotation pattern master of the second resolution to manufacture a continuous geometric phase diffraction optical element of the second resolution;
The second resolution has an increased value compared to the first resolution,
A method of manufacturing a continuous geometric phase diffractive optical element from a discontinuous geometric phase diffractive optical element. According to claim 1,
A method for manufacturing a continuous geometric phase diffractive optical element from a discontinuous geometric phase diffractive optical element, wherein in the b) and d) steps, the anisotropic medium is applied to have a thickness of half a wave plate. According to claim 1,
In step c), the separation distance between the discontinuous geometric phase diffraction optical element of the first resolution and the substrate on which the first light-aligning material is applied is the formula

(Z is the separation distance, λ is the center wavelength of the irradiated UV light, Λ is the pattern period of the optical axis rotation pattern master, N is the number of diffraction gratings included in one period, and A is 90 or more and 110 or less) felled,
A method of manufacturing a continuous geometric phase diffractive optical element from a discontinuous geometric phase diffractive optical element. The method of claim 1 , wherein the anisotropic medium comprises reactive mesogen.
A method of manufacturing a continuous geometric phase diffractive optical element from a discontinuous geometric phase diffractive optical element. According to claim 1,
e) using, as a mask, the continuous geometric phase diffraction optical element of the second resolution disposed at a predetermined distance on the substrate coated with the second light-aligning material, and injecting the linearly polarized beam thereto manufacturing a continuous optical axis rotation pattern master of a third resolution by engraving a polarization pattern reduced by ½ to the second light-aligning material; and
f) applying an anisotropic medium to the continuous optical axis rotation pattern master of the third resolution to manufacture a continuous geometric phase diffraction optical element of the third resolution; further comprising,
The third resolution has an increased value compared to the second resolution,
A method of manufacturing a continuous geometric phase diffractive optical element from a discontinuous geometric phase diffractive optical element.

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