Liquid crystal grating of three diffraction modes in orthogonal orientation

Abstract

The application provides a liquid crystal grating which can realize three diffraction modes by orthogonal orientation, comprising an upper glass substrate, an upper strip electrode I, an upper strip electrode II, a liquid crystal layer, a lower strip electrode I, a lower strip electrode II and a lower glass substrate. The diffraction mode of the liquid crystal grating is controlled by controlling the driving voltage V1 and V2 applied to the upper strip electrode I and the lower strip electrode I. When the driving voltage V1=0V and V2>0V, the incident light will be diffracted in the y direction through the liquid crystal layer. When the driving voltage V1>0V and V2=0V, the incident light will be diffracted in the x direction through the liquid crystal layer. When the driving voltage V1>0V and V2>0V, the incident light will be diffracted in the x and y directions through the liquid crystal layer. In addition, the diffraction order number and the diffraction efficiency of the liquid crystal grating can be adjusted by changing the size of the driving voltage V1 and V2.

Description

I. TECHNICAL FIELD

[0001] The present application relates to the technical field of liquid crystal grating, and particularly to a liquid crystal grating with three kinds of diffraction modes in orthogonal orientation. II. BACKGROUND

[0002] Liquid crystal grating has become a research hotspot due to its adjustable diffraction order and diffraction efficiency with voltage, simple structure, and light and thin characteristics, and has wide application prospects in the fields of large-viewing-angle holographic 3D display, diffraction imaging, and optical communication. In recent years, the research on liquid crystal grating has become mature, and researchers have proposed liquid crystal gratings with different structures and functions, such as edge field conversion adjustable nematic liquid crystal grating, chessboard-shaped layered cholesteric liquid crystal grating, and pitch-adjustable liquid crystal grating. The edge field conversion adjustable nematic liquid crystal grating reduces the driving voltage by using the edge electric field of the electrode to induce the liquid crystal molecules, the chessboard-shaped layered cholesteric liquid crystal grating realizes fine pitch tuning of the liquid crystal grating, and the pitch-adjustable liquid crystal grating realizes two kinds of liquid crystal grating pitches by using different driving modes. However, the single diffraction mode is still the main problem faced by current liquid crystal gratings, which limits its further development. III. SUMMARY

[0003] The present application aims to overcome the deficiencies in the prior art and proposes a liquid crystal grating with three kinds of diffraction modes in orthogonal orientation. The present application comprises an upper glass substrate, upper strip electrodes I and II, a liquid crystal layer, lower strip electrodes I and II, and a lower glass substrate.

[0004] The liquid crystal layer has a uniform thickness and adopts orthogonal orientation. The orientation direction of the upper liquid crystal layer is perpendicular to the long side direction of the upper strip electrodes I and II, and the orientation direction of the lower liquid crystal layer is perpendicular to the long side direction of the lower strip electrodes I and II.

[0005] The upper strip electrodes I and II and the lower strip electrodes I and II are made of transparent conductive material. The widths of the upper strip electrodes I, the upper strip electrodes II, the lower strip electrodes I, and the lower strip electrodes II are the same. The gap between the upper strip electrodes I and II is the same as the gap between the lower strip electrodes I and II. The gap between all strip electrodes is greater than or equal to the width of all strip electrodes. The upper strip electrode I and the lower strip electrode I are connected to a driving voltage. The driving voltages applied to the upper strip electrode I and the lower strip electrode I are V1 and V2, respectively.

[0006] The liquid crystal grating of three diffraction modes in orthogonal orientation controls the diffraction mode of the liquid crystal grating by controlling the driving voltage V1 and V2 applied on the upper strip electrode I and the lower strip electrode I, and the specific principle is as follows: when the driving voltage V1=0V and V2>0V, the spatial non-uniform electric field distribution is generated between the lower strip electrodes I and II, the liquid crystal molecules are induced to rearrange in the y direction to form a gradient refractive index distribution in central symmetry, at this time, the incident light will be diffracted in the y direction through the liquid crystal layer; when the driving voltage V1>0V and V2=0V, the spatial non-uniform electric field distribution is generated between the upper strip electrodes I and II, the liquid crystal molecules are induced to rearrange in the x direction to form a gradient refractive index distribution in central symmetry, at this time, the incident light will be diffracted in the x direction through the liquid crystal layer; when the driving voltage V1>0V and V2>0V, the spatial non-uniform electric field distribution is generated between the upper strip electrodes I and II and between the lower strip electrodes I and II, the liquid crystal molecules form a gradient refractive index distribution in central symmetry in the x and y directions, at this time, the incident light will be diffracted in the x and y directions through the liquid crystal layer. Since the liquid crystal layer adopts the orthogonal orientation mode, the long axis direction of the liquid crystal molecules always keeps consistent with the direction of the electric field under the condition of power-on, without overcoming the extra torsional force, the diffraction accuracy is improved. In addition, the number of diffraction orders and the diffraction efficiency of the liquid crystal grating can be adjusted by changing the size of the driving voltage V1 and V2. IV. BRIEF DESCRIPTION OF DRAWINGS

[0007] Figure 1 is a structural schematic diagram of a liquid crystal grating of three diffraction modes in orthogonal orientation according to an embodiment of the present application. Figure 1 Figure 1 is a structural schematic diagram of a liquid crystal grating of three diffraction modes in orthogonal orientation according to an embodiment of the present application.

[0008] Figure 2 is a liquid crystal molecule distribution of the liquid crystal grating of three diffraction modes in orthogonal orientation according to an embodiment of the present application. Figure 2 Figure 2 is a liquid crystal molecule distribution of the liquid crystal grating of three diffraction modes in orthogonal orientation according to an embodiment of the present application. Figure 2 (a) is the liquid crystal molecule distribution when V1=0V and V2=0V, (b) is the liquid crystal molecule distribution when V1=3.5V and V2=3.5V. Figure 2 (a) is the liquid crystal molecule distribution when V1=0V and V2=0V, (b) is the liquid crystal molecule distribution when V1=3.5V and V2=3.5V.

[0009] Figure 3 is a diffraction effect of the liquid crystal grating of three diffraction modes in orthogonal orientation according to an embodiment of the present application. Figure 3 Figure 3 is a diffraction effect of the liquid crystal grating of three diffraction modes in orthogonal orientation according to an embodiment of the present application. Figure 3 (a) is the diffraction effect in the y direction, (b) is the diffraction effect in the x direction, and (c) is the diffraction effect in the x and y directions. Figure 3 (a) is the diffraction effect in the y direction, (b) is the diffraction effect in the x direction, and (c) is the diffraction effect in the x and y directions. Figure 3 (a) is the diffraction effect in the y direction, (b) is the diffraction effect in the x direction, and (c) is the diffraction effect in the x and y directions.

[0010] Figure 4 is a structural schematic diagram of a liquid crystal grating of three diffraction modes in orthogonal orientation according to another embodiment of the present application. Figure 1 Figure 4 is a structural schematic diagram of a liquid crystal grating of three diffraction modes in orthogonal orientation according to another embodiment of the present application.

[0011] Figure 4 is a structural schematic diagram of a liquid crystal grating of three diffraction modes in orthogonal orientation according to another embodiment of the present application.Figure 1 The illustrated letters in the figure are: d is the thickness of the liquid crystal layer, w is the width of all the strip electrodes, and I is the gap between the strip electrodes.

[0012] It should be understood that the above-mentioned figures are only schematic and not drawn on scale. V. DETAILED DESCRIPTION

[0013] The following will describe in detail an embodiment of the liquid crystal grating of three diffraction modes in orthogonal orientation proposed by the present application, and further describe the present application. It is necessary to point out here that the following embodiment is only used for further description of the present application, and cannot be understood as a limitation on the protection scope of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application according to the above-mentioned content of the present application, and still belong to the protection scope of the present application.

[0014] The structural schematic diagram of the liquid crystal grating of three diffraction modes in orthogonal orientation proposed by the present application is shown in the accompanying drawings as follows: Figure 1 The liquid crystal grating of three diffraction modes in orthogonal orientation proposed by the present application is shown in the accompanying drawings as follows, which comprises an upper glass substrate, an upper strip electrode I, an upper strip electrode II, a liquid crystal layer, a lower strip electrode I, a lower strip electrode II, and a lower glass substrate. The thickness of the liquid crystal layer is uniform, the liquid crystal layer adopts orthogonal orientation mode, the orientation direction of the upper liquid crystal layer is perpendicular to the long side direction of the upper strip electrodes I and II, the orientation direction of the lower liquid crystal layer is perpendicular to the long side direction of the lower strip electrodes I and II, and the liquid crystal layer adopts E7 nematic phase liquid crystal material. The upper strip electrodes I and II and the lower strip electrodes I and II are all made of transparent conductive material, the width of the upper strip electrodes I, the upper strip electrodes II, the lower strip electrodes I, and the lower strip electrodes II are all the same, the gap between the upper strip electrodes I and II is the same as the gap between the lower strip electrodes I and II, the gap between all the strip electrodes is greater than or equal to the width of all the strip electrodes, the upper strip electrode I and the lower strip electrode I are connected to a driving voltage, and the driving voltages applied to the upper strip electrode I and the lower strip electrode II are V1 and V2 respectively.

[0015] The diffraction mode of the liquid crystal grating is controlled by controlling the driving voltages V1 and V2 applied to the upper and lower strip electrodes I, when the driving voltages V1=0V and V2>0V, a spatially non-uniform electric field distribution is generated between the lower strip electrodes I and II, which induces the liquid crystal molecules to rearrange in the y direction to form a gradient refractive index distribution in a center-symmetrical manner, at this time, the incident light will be diffracted in the y direction by the liquid crystal layer; when the driving voltages V1>0V and V2=0V, a spatially non-uniform electric field distribution is generated between the upper strip electrodes I and II, which induces the liquid crystal molecules to rearrange in the x direction to form a gradient refractive index distribution in a center-symmetrical manner, at this time, the incident light will be diffracted in the x direction by the liquid crystal layer; when the driving voltages V1>0V and V2>0V, spatially non-uniform electric field distributions are generated between the upper strip electrodes I and II and between the lower strip electrodes I and II, the liquid crystal molecules form gradient refractive index distributions in the x and y directions in a center-symmetrical manner, at this time, the incident light will be diffracted in the x and y directions simultaneously by the liquid crystal layer. Since the liquid crystal layer adopts a normal orientation mode, the long axis direction of the liquid crystal molecules always keeps consistent with the direction of the electric field under the condition of power-on, without the need to overcome additional twisting force, the diffraction accuracy is improved. In addition, the number of diffraction orders and the diffraction efficiency of the liquid crystal grating can be adjusted by changing the sizes of the driving voltages V1 and V2.

[0016] The characteristic parameters of the nematic liquid crystal material used in the embodiment are as follows: refractive index n o =1.517, n e =1.741, birefringence Δn=0.224, dielectric constant Δε=11.4, viscosity γ=29 mPa.s.

[0017] The thickness d of the liquid crystal layer in the embodiment is 10 μm, the width w of all the strip electrodes is 10 μm, and the gap l of the strip electrodes is 10 μm.

[0018] Figure 1 is a schematic diagram of a liquid crystal grating with three diffraction modes according to the embodiment of the present application. Figure 2 Figure 2 is a liquid crystal molecule distribution of the liquid crystal grating with three diffraction modes according to the embodiment of the present application. Figure 2 (a) shows that the liquid crystal molecules are arranged orthogonally on the liquid crystal layer and vertically to the long side direction of the strip electrodes. Figure 2 (b) shows that the liquid crystal molecules are rearranged, the change in the tilt angle of the liquid crystal molecules between the strip electrodes is less than the change in the tilt angle of the liquid crystal molecules above the strip electrodes, and the long axis direction of the liquid crystal molecules always keeps consistent with the direction of the electric field.

[0019] Figure 3 is a diffraction effect of the liquid crystal grating with three diffraction modes according to the embodiment of the present application. Figure 3 Figure 4 is a diffraction effect of the liquid crystal grating with three diffraction modes according to the embodiment of the present application. Figure 3(a) is shown, at this time the incident light is diffracted in y direction by the liquid crystal layer. When the driving voltage V1=3.5V, V2=0V, as shown in the attached figure (b), at this time the incident light is diffracted in x direction by the liquid crystal layer. When the driving voltage V1=3.5V, V2=3.5V, as shown in the attached figure (c), at this time the incident light is diffracted in x and y direction by the liquid crystal layer. Figure 3 (b) is shown, at this time the incident light is diffracted in x direction by the liquid crystal layer. When the driving voltage V1=3.5V, V2=3.5V, as shown in the attached figure (c), at this time the incident light is diffracted in x and y direction by the liquid crystal layer. Figure 3 (c) is shown, at this time the incident light is diffracted in x and y direction by the liquid crystal layer.

[0020] The above only describes the preferred embodiments of the present application, but the present application is not limited to this embodiment. Those skilled in the art should understand that various changes can be made to the form and details of the present application without departing from the spirit and scope of the present application defined by the claims.

Claims

1. A liquid crystal grating of orthogonal orientation of three diffraction modes, comprising an upper glass substrate, an upper strip electrode I, an upper strip electrode II, a liquid crystal layer, a lower strip electrode I, a lower strip electrode II and a lower glass substrate, the upper strip electrode I and the lower strip electrode I are connected to a driving voltage, the diffraction mode of the liquid crystal grating is controlled by controlling the driving voltage V1 and V2 applied to the upper strip electrode I and the lower strip electrode I.

2. A liquid crystal grating of three diffraction orders of orthogonal orientations according to claim 1, characterized in that, The thickness of the liquid crystal layer is uniform, the liquid crystal layer adopts orthogonal orientation mode, the orientation direction of the upper liquid crystal layer is perpendicular to the long side direction of the upper strip electrode I and II, and the orientation direction of the lower liquid crystal layer is perpendicular to the long side direction of the lower strip electrode I and II.

3. A liquid crystal grating of orthogonal orientation of three diffraction orders according to claim 1, characterized in that, The width of the upper strip electrode I, the upper strip electrode II, the lower strip electrode I and the lower strip electrode II is the same, the gap between the upper strip electrode I and II is the same as the gap between the lower strip electrode I and II, and the gap between all strip electrodes is greater than or equal to the width of all strip electrodes.

4. The liquid crystal grating of claim 1, wherein the liquid crystal grating is a cross- oriented three-diffraction-mode liquid crystal grating. When the driving voltage V1=0V and V2>0V, the incident light will be diffracted in the y direction through the liquid crystal layer, when the driving voltage V1>0V and V2=0V, the incident light will be diffracted in the x direction through the liquid crystal layer, when the driving voltage V1>0V and V2>0V, the incident light will be diffracted in the x and y directions through the liquid crystal layer.

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