Superlens for dodging and dodging emitting device comprising same

Abstract

The utility model provides a super lens for dodging and a dodging emitting device comprising the same. The super lens comprises a substrate and a micro-nano structure arranged on the substrate, the super lens is used for modulating the received light beam so as to form a homogenized light spot on a target plane; the micro-nano structures are anisotropic, and the absolute value of the difference value between the rotation angles of two adjacent micro-nano structures on the super lens is larger than a preset threshold value. According to the invention, the geometric phase of the super lens is designed through the GS algorithm, so that the phase distribution of the super lens is more random, the rotation angles of the adjacent micro-nano structures differ greatly, that is, the same-polarization phase of the super lens is more disordered, the same-polarization emergent light does not become zero-order, and the homogenization effect on the light beam is improved.

Description

Technical Field

[0001] The present application relates to the field of optics, and in particular to a metalens for light uniformity and a light uniformity emitting device comprising the metalens. Background Art

[0002] A metalens is a planar optical lens manufactured in large quantities using semiconductor chip technology. It features surface micro-nanostructures that modulate the phase of incident light. Due to its thinness, light weight, and low cost, metalens are increasingly being used in the optical field, for example, using metasurfaces for light uniformity. Currently, most metalenses are designed based on the principle of transmission phase. This type of metalens achieves phase control of the light beam by adjusting the geometric dimensions of the micro-nanostructure. However, this phase control method is highly sensitive to manufacturing tolerances. In other words, the process conditions and errors in the actual manufacturing process make it difficult for the actual dimensions of the micro-nanostructure to be completely consistent with their pre-set dimensions, which in turn affects the accuracy of phase control and creates a "zero-order problem." In light uniformity applications, the "zero-order problem" manifests itself as a significant increase in the light intensity at the center of the light spot, which is not as expected in the design, affecting the light uniformity performance of the metalens.

[0003] In order to solve the "zero-order problem", the existing technology designs the metalens based on the geometric phase principle. However, the metalens designed based on the geometric phase principle still has a gradient distribution with a regular shape (such as a circle or an ellipse), that is, the overall distribution has a gradient decrease or gradient increase within the regular shape. When the phases of adjacent positions on the metalens are regularly distributed and the gradient is small, the "zero-order problem" will still occur. Utility Model Content

[0004] One objective of this application is to provide a metalens for light homogenization and a light homogenization emission device containing the same. This application designs the geometric phase of the metalens using the GS algorithm, making the phase distribution of the metalens more random. This results in a larger difference in the rotation angles of adjacent micro-nanostructures, which in turn makes the phase of the same polarization of the metalens more chaotic. This prevents the emitted light of the same polarization from becoming zero-order, thereby improving the homogenization effect of the light beam.

[0005] According to one aspect of an embodiment of the present application, a metalens for light homogenization is disclosed, the metalens comprising a substrate and a micro-nanostructure disposed on the substrate;

[0006] The metalens is used to modulate the received light beam to form a homogenized light spot on the target plane;

[0007] The micro-nanostructure is anisotropic, and the absolute value of the difference between the rotation angles of two adjacent micro-nanostructures on the superlens is greater than a preset threshold.

[0008] In an exemplary embodiment of the present application, adjacent micro-nano structures on the metalens whose absolute values ​​of differences between all rotation angles are greater than a preset threshold are irregularly distributed on the metalens.

[0009] In an exemplary embodiment of the present application, the preset threshold is 15°.

[0010] In an exemplary embodiment of the present application, the preset threshold is 30°.

[0011] In an exemplary embodiment of the present application, the emission angles of the light beams projected from various positions on the metalens are randomly distributed.

[0012] In an exemplary embodiment of the present application, the size difference between any two micro-nano structures on the metalens is within a preset tolerance range.

[0013] In an exemplary embodiment of the present application, the preset tolerance range is from -10 nm to 10 nm.

[0014] In an exemplary embodiment of the present application, the preset tolerance range is -5 nm to 5 nm.

[0015] In an exemplary embodiment of the present application, the micro-nano structure is a nano-fin structure or an elliptical column structure.

[0016] According to one aspect of an embodiment of the present application, a uniform light emitting device is disclosed, the uniform light emitting device comprising: a super lens as described in any one of the above embodiments; a light source;

[0017] The super lens is arranged on the light-emitting side of the light source.

[0018] In an exemplary embodiment of the present application, the light source is a VCSEL light source.

[0019] The present application provides a metalens for light homogenization and a light homogenization emitting device including the same. The metalens includes a substrate and a micro-nanostructure disposed on the substrate. The metalens is used to modulate the received light beam to form a homogenized light spot on the target plane. The micro-nanostructure is anisotropic, and the absolute value of the difference between the rotation angles of two adjacent micro-nanostructures on the metalens is greater than a preset threshold. The present application designs the geometric phase of the metalens through the GS algorithm, making the phase distribution of the metalens more random, thereby making the rotation angles of adjacent micro-nanostructures differ greatly, that is, the same polarization phase of the metalens is more chaotic, so that the same polarization output light will not become zero order, thereby improving the homogenization effect of the light beam.

[0020] Other features and advantages of the present application will become apparent from the following detailed description, or may be learned in part by practice of the present application.

[0021] It should be understood that the foregoing general description and the following detailed description are merely illustrative and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The above and other objects, features and advantages of the present application will become more apparent by describing in detail example embodiments thereof with reference to the attached drawings.

[0023] Figure 1 A schematic diagram of the polarization conversion phase of a metalens provided by the prior art is shown.

[0024] Figure 2 FIG. 4 shows a schematic diagram of the same polarization phase of a metalens provided by the prior art. FIG.

[0025] Figure 3 FIG. 1 shows a structural schematic diagram of a metalens provided in one embodiment of the present application.

[0026] Figure 4 A schematic diagram of the polarization conversion phase of a metalens provided in one embodiment of the present application is shown.

[0027] Figure 5 A schematic diagram of the same polarization phase of the metalens provided in one embodiment of the present application is shown.

[0028] Figure 6 FIG. 1 shows a partial structural diagram of a metalens provided in one embodiment of the present application.

[0029] Figure 7 FIG. 1 shows a partial structural diagram of a metalens provided in one embodiment of the present application.

[0030] Figure 8 FIG. 1 shows a partial structural diagram of a metalens provided in one embodiment of the present application.

[0031] Figure 9 A schematic diagram showing light beam modulation by a metalens provided in the prior art is shown.

[0032] Figure 10 A schematic diagram showing light beam modulation by a metalens provided in one embodiment of the present application is shown.

[0033] Figure 11 A schematic diagram of the local phase distribution of a metalens provided in one embodiment of the present application is shown.

[0034] Figure 12 A schematic diagram of the light intensity distribution of the uniform light spot projected by the metalens provided in one embodiment of the present application is shown.

[0035] Figure 13A schematic diagram showing the light intensity distribution of a uniform light spot projected by a uniform light emitting device provided in an embodiment of the present application in an x-center section and a y-center section is shown.

[0036] Reference numerals:

[0037] 1-superlens; 11-substrate; 12-micro-nanostructure. DETAILED DESCRIPTION

[0038] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in a variety of forms and should not be construed as limited to the examples set forth herein; rather, these example embodiments are provided so that the description of this application will be more comprehensive and complete and will fully convey the concepts of the example embodiments to those skilled in the art. The accompanying drawings are merely schematic illustrations of the present application and are not necessarily drawn to scale. Identical reference numerals in the figures indicate identical or similar parts, and thus repeated descriptions thereof will be omitted.

[0039] In addition, the described features, structures or characteristics may be combined in one or more example embodiments in any suitable manner. In the following description, many specific details are provided to provide a full understanding of the example embodiments of the present application. However, those skilled in the art will appreciate that the technical solutions of the present application may be practiced while omitting one or more of the specific details, or other methods, components, steps, etc. may be adopted. In other cases, known structures, methods, implementations or operations are not shown or described in detail to avoid obscuring the main content and making various aspects of the present application vague.

[0040] In the prior art, metalenses are usually designed based on the transmission phase principle. The phase control of the light beam by this metalens is achieved by adjusting the geometric dimensions of the micro-nanostructure, wherein the micro-nanostructure is generally a cylinder, a prism with a square cross-section, and the modulation effect of the light beam is achieved by adjusting the geometric dimensions of the micro-nanostructure. However, this phase control method is highly sensitive to manufacturing tolerances. In the actual manufacturing process, due to process conditions or errors generated, it is difficult for the actual size of the micro-nanostructure to be completely consistent with its pre-set size, resulting in a bright spot in the center of the final projected homogenized light spot, that is, a "zero-order problem", which affects the effect of the metalens on the homogenization of the light beam. In order to solve the "zero-order problem", the prior art will design the metalens based on the geometric phase principle, and adjust the rotation angle of the micro-nanostructure in the metalens to achieve phase control of the light beam.

[0041] However, the phase of the metalens designed based on the geometric phase principle in the prior art is obtained by geometric method. In fact, this phase is a gradient phase. Figure 1 and Figure 2 , Figure 1FIG1 shows a schematic diagram of the polarization conversion phase of a metalens provided by the prior art. Figure 2 The figure shows the same polarization phase of the metalens provided by the prior art; polarization conversion phase refers to the relative phase difference between different polarization components during the polarization state conversion of the light beam; same polarization phase refers to the phase relationship between light waves at different positions or at different time points under the same polarization state. Figure 1 and Figure 2 It can be seen from the figure that the phase distribution of the metalens designed based on the geometric phase principle in the prior art is a gradient distribution with a regular shape. Both the polarization conversion phase and the co-polarization phase are distributed in an approximately elliptical ring shape, and the phase distribution has a gradient decreasing trend within the ring. When the phases of adjacent positions on the metalens are regularly distributed and the gradient is small, the rotation angle difference between adjacent micro-nanostructures is small, and the co-polarization phases of the micro-nanostructures through which the light beam passes are relatively close. These co-polarized lights are coherent, and interference will occur when the coherent light waves are superimposed in space, which will cause the co-polarized output light to become zero-order light, that is, a "zero-order problem" will occur.

[0042] In order to overcome the above-mentioned defects of the related art, the present application provides a metalens for uniform light and a uniform light emitting device containing the same. The present application designs the geometric phase of the metalens through the GS algorithm, so that the overall phase distribution of the metalens is more random, thereby making the overall rotation angles of adjacent micro-nano structures on the metalens differ greatly, that is, the same polarization phase of the metalens is more chaotic, so that the same polarization output light will not become zero order, thereby improving the homogenization effect of the light beam.

[0043] This application provides a metalens for light homogenization, such as Figure 3 As shown, Figure 3 Figure 1 shows a schematic diagram of the structure of a metalens provided in one embodiment of the present application. The metalens 1 includes a substrate 11 and a micro-nanostructure 12 disposed on the substrate 11. The micro-nanostructure 12 is a subwavelength structure. The metalens 1 is used to receive and modulate a light beam, thereby forming a uniform light spot on a target plane.

[0044] In the embodiment of the present application, the micro-nanostructure 12 on the metalens 1 is anisotropic. Anisotropy refers to the difference in the optical properties of a material in different directions. This difference is reflected in the refractive index, optical rotation and absorption spectrum.

[0045] It should be noted that the metalens 1 of the present application is designed based on the principle of geometric phase. Geometric phase refers to the phase difference caused by the change in the geometric characteristics of the light propagation path during the propagation of the light field. This phase change is closely related to the polarization state of the light and is a special phase phenomenon that occurs during the propagation of light. In the field of metalens phase modulation, geometric phase modulation is a polarization-dependent phase modulation method. This method can achieve the purpose of phase modulation by simply modulating the rotation angle of the micro-nanostructure 12 in the metalens 1. The relationship between the rotation angle of the micro-nanostructure 12 and the phase is: The positive and negative signs are related to the circular polarization state of the light beam, and θ is the rotation angle of the micro-nano structure 12.

[0046] Furthermore, the phase of the metalens 1 of the present application can be obtained by the GS (Gerchberg-Saxton) algorithm, which is a phase recovery algorithm. The principle of the GS algorithm is to recover the corresponding phase distribution by using the known light intensity distribution of the object surface and the intensity distribution of the observation surface. Compared with the phase obtained by the geometric method, the phase obtained by the GS algorithm is more random, see Figure 4 and Figure 5 , Figure 4 : shows a schematic diagram of the polarization conversion phase of the metalens provided in one embodiment of the present application, Figure 5 A schematic diagram of the same polarization phase of the metalens provided in one embodiment of the present application is shown. Figure 4 and Figure 5 Respectively Figure 1 and Figure 2 By comparison, it can be seen that the phase of the metalens provided by the present application is more random. In this case, the outgoing light with the same polarization will not become zero-order, thus avoiding the zero-order problem in the process of homogenizing the light beam by the metalens and improving the uniform light effect of the metalens. Figure 4 and Figure 5 This is only one phase distribution of the metalens provided in this application, and does not mean that the phase distribution of the metalens provided in this application is limited to this.

[0047] The relationship between the rotation angle and phase of the micro-nanostructure 12 of the metalens 1 designed based on the geometric phase principle is: When the phase of the metalens 1 is randomly distributed as a whole, the rotation angles of adjacent micro-nanostructures on the metalens 1 are also randomly distributed as a whole, and the rotation angles of adjacent micro-nanostructures 12 differ greatly.

[0048] Therefore, in the embodiment of the present application, the absolute value of the difference between the rotation angles of two adjacent micro-nano structures 12 of the metalens 1 is greater than the preset threshold range. Figure 6 Shown and Figure 7 As shown, Figure 6FIG2 shows a partial structural diagram of a metalens provided in one embodiment of the present application. Figure 7 The schematic diagram of the partial structure of the metalens provided by one embodiment of the present application is shown. The rotation angle of the micro-nanostructure 12 refers to the rotation angle of the micro-nanostructure 12 relative to the horizontal positive direction (i.e. Figure 6 and Figure 7 The rotation angle of the positive x-axis in Figure 6 and Figure 7 , Figure 6 and Figure 7 a1, a2, a3 and a4 are the rotation angles of the corresponding micro-nanostructure 12 respectively.

[0049] In one embodiment, the adjacent micro-nano structures 12 on the metalens 1 provided by the present application, whose absolute values ​​of the differences between all rotation angles are greater than a preset threshold, are irregularly distributed on the metalens 1. Figure 8 , Figure 8 FIG. 1 shows a partial structural diagram of a metalens 1 provided in one embodiment of the present application. Figure 8 The dotted box in the figure indicates that the absolute value of the difference between the rotation angles of the two circled micro-nano structures 12 is greater than the preset threshold value (the box not circled does not mean that it does not meet the requirements, Figure 8 This is for illustrative purposes only. In other words, in the metalens 1 provided in the present application, the specific positions of the adjacent micro-nanostructures 12 whose absolute value of the difference between any set of rotation angles is greater than the preset threshold value on the metalens 1 are randomly distributed without any regularity. In this case, the same polarization output light can be prevented from becoming zero-order light, thereby avoiding the zero-order problem and improving the uniform light effect of the metalens.

[0050] In one embodiment, the preset threshold is 15°. That is, there are two adjacent micro-nano structures 12 on the metalens 1, and the absolute value of the difference between the rotation angles of the two adjacent micro-nano structures 12 is greater than 15°. Figure 2 As shown, for example, if the absolute value of the difference between a1 and a2 is greater than 15 degrees, that is, |a1-a2|>15°. In this case, the rotation angle deviation between adjacent micro-nanostructures 12 on the metalens 1 is large, and the phase of the same polarization at various locations on the metalens 1 is relatively random, avoiding the zero-order problem and producing a homogenized light spot with better homogenization effect.

[0051] In one embodiment, the preset threshold is 30°. That is, there are two adjacent micro-nano structures 12 on the metalens 1, and the absolute value of the difference between the rotation angles of the two adjacent micro-nano structures 12 is greater than 30°. Figure 2As shown, for example, if the absolute value of the difference between a3 and a4 is greater than 30 degrees, that is, |a3-a4|>30°. In this case, the rotation angle deviation of the ringing micro-nanostructure 12 on the metalens 1 is larger, and the phase of the same polarization at various positions of the metalens 1 is more random, further avoiding the zero-order problem. In other words, the homogenization effect of the metalens 1 is better, and the generated homogenized light spot does not have obvious bright spots.

[0052] In one embodiment, the difference between the rotation angles of two adjacent micro-nano structures 12 on the metalens 1 is greater than 15 degrees, and the difference between the rotation angles of another two adjacent micro-nano structures 12 is greater than 30 degrees.

[0053] Because the phase of the metalens 1 of the present application is obtained using the GS algorithm, its phase is relatively random. Therefore, the phase of the same polarization output light formed after the light beam passes through the micro-nanostructure 12 is also relatively chaotic. Therefore, in one embodiment, the output angle of the light beam obtained by modulating various positions on the metalens 1 is randomly distributed.

[0054] It should be noted that, see Figure 9 and Figure 10 , Figure 9 FIG1 shows a schematic diagram of light beam modulation by a metalens provided by the prior art. Figure 10 FIG1 shows a schematic diagram of light beam modulation by a metalens provided in one embodiment of the present application. The light beam modulated by the metalens of the prior art is regularly distributed as a whole, that is, the emission angle of the light beam changes regularly (or presents a uniform emission angle) as the distance between the emission position and the center of the metalens changes. Figure 9 As shown in FIG, the emission angle of the light beam increases as the distance between the emission position and the center of the metal lens increases; the random distribution of the emission angle of the light beam in this embodiment means that the light beam projected by the metal lens is random as a whole, such as Figure 10 As shown, in fact, the emission angle of the light beam is not regular, and the emission angle of the light beam does not change regularly with the change of the distance between the emission position and the center of the metalens. Ultimately, all the messy light beams are projected onto the target plane to form a uniform light spot.

[0055] Because the metalens 1 is designed based on the principle of geometric phase, all micro-nanostructures 12 on the metalens 1 should maintain consistent dimensions. Consequently, geometric modulation of the light beam can be achieved by adjusting the rotation angles of all micro-nanostructures 12. However, given the practical difficulties of achieving consistent dimensions for all micro-nanostructures 12, in one embodiment, the size difference between any two micro-nanostructures 12 on the metalens 1 is within a preset tolerance range.

[0056] It should be noted that in this embodiment, the cross-sectional shapes of all micro-nanostructures 12 are consistent. For example, the cross-sectional shapes of all micro-nanostructures 12 are rectangular. Under this premise, the size difference between two micro-nanostructures 12 is also calculated accordingly and is within the preset tolerance range. For example, the difference in the long side size and the difference in the short side size of any two micro-nanostructures 12 with rectangular cross-sections are both within the preset tolerance range. In this case, the negative impact of the manufacturing tolerance on the uniform light effect of the metalens can be ensured.

[0057] Furthermore, the preset tolerance range is -10 nm to 10 nm, that is, the size difference between any two micro-nano structures 12 on the metalens 1 should be within 10 nm.

[0058] Furthermore, the preset tolerance range is -5nm to 5nm.

[0059] Furthermore, the sizes of all the micro-nano structures 12 on the metalens 1 are exactly the same.

[0060] In one embodiment, the micro-nano structure 12 is a nano-fin structure (rectangular column structure) or an elliptical column structure. In order to achieve the modulation of the geometric phase, the micro-nano structure 12 is required to have anisotropy. Both the nano-fin structure and the elliptical column structure have anisotropy, such as Figure 2 and Figure 3 As shown, Figure 2 Shown is a top view of the nanofin structure. Figure 3 The top view of the elliptical cylinder structure is shown. It should be emphasized that other structures that can achieve anisotropy of the micro-nanostructure 12 are within the scope of protection of this application. This application also provides a uniform light emitting device, which includes: a metalens 1 as described in any of the above embodiments; and a light source.

[0061] Specifically, the superlens 1 is arranged on the light-emitting side of the light source. The superlens 1 is used to receive the light beam emitted by the light source and modulate the light beam so as to project a uniform light spot on the target plane.

[0062] In one embodiment, the light source is a VCSEL (Vertical-Cavity Surface-Emitting Laser) light source.

[0063] Example

[0064] In this embodiment, a VCSEL light source with an operating center wavelength of 940 nm was selected as the light source. The micro-nanostructure 12 on the metalens 1 was a nanofin structure made of amorphous silicon, with no filler layer between the micro-nanostructures 12. The period of the micro-nanostructure was 360 nm, the height was 602 nm, and the major and minor axes of the nanofin structure were 284 nm and 134 nm, respectively. Testing showed that the polarization conversion efficiency of the micro-nanostructure 12 was 99.65%.

[0065] In this embodiment, the phase of the metalens is obtained by the GS algorithm, wherein the FOI of the metalens is 68°×54° (horizontal direction×vertical direction), and the local phase distribution of the metalens 1 is finally obtained as follows: Figure 11 As shown, Figure 11 FIG. 4 shows a local phase distribution diagram of a metalens provided in an embodiment of the present application.

[0066] Then, the Rayleigh-Sommerfeld diffraction algorithm is used to simulate the homogenization effect of the light spot passing through the super lens 1. The obtained light intensity distribution is as follows: Figure 12 and Figure 13 As shown, Figure 12 FIG2 shows a schematic diagram of the light intensity distribution of the uniform light spot projected by the metalens provided in one embodiment of the present application. Figure 13 A schematic diagram showing the light intensity distribution of a uniform light spot projected by a uniform light emitting device provided in an embodiment of the present application in an x-center section and a y-center section is shown.

[0067] Those skilled in the art will readily appreciate other embodiments of the present application after considering the specification and practicing the utility model disclosed herein. This application is intended to cover any variations, uses, or adaptations of the present application that follow the general principles of the present application and include common knowledge or customary techniques in the art not disclosed herein. The description and examples are to be considered merely as exemplary, and the true scope and spirit of the present application are indicated by the appended claims.

Claims

1. A metalens for light homogenization, characterized in that: The superlens includes a substrate and a micro-nano structure arranged on the substrate; The metalens is used to modulate the received light beam to form a homogenized light spot on the target plane; The micro-nanostructure is anisotropic, and the absolute value of the difference between the rotation angles of two adjacent micro-nanostructures on the superlens is greater than a preset threshold.

2. The metalens according to claim 1, wherein Adjacent micro-nano structures whose absolute values ​​of differences between all rotation angles on the superlens are greater than a preset threshold are irregularly distributed on the superlens.

3. The metalens according to claim 1, wherein The preset threshold is 15°.

4. The metalens according to claim 1, wherein The preset threshold is 30°.

5. The metalens according to claim 1, wherein The emission angles of the light beams projected from various positions on the metalens are randomly distributed.

6. The metalens according to claim 1, wherein The size difference between any two micro-nano structures on the metalens is within a preset tolerance range.

7. The metalens according to claim 6, wherein The preset tolerance range is from -10 nm to 10 nm.

8. The metalens according to claim 1, wherein The micro-nano structure is a nano-fin structure or an elliptical column structure.

9. A uniform light emitting device, characterized in that: The uniform light emitting device comprises: a super lens according to any one of claims 1 to 8; a light source; The super lens is arranged on the light-emitting side of the light source.

10. The uniform light emitting device according to claim 9, characterized in that: The light source is a VCSEL light source.

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