Devices including lens configurations with stacked metasurfaces and methods for manufacturing same

Abstract

An example of an apparatus includes a lens mechanism including a first substrate having a first metasurface and a second substrate having a second metasurface, the first and second metasurfaces being stacked and facing each other, and the first and second metasurfaces being separated from each other by an adhesive that attaches the first and second substrates to each other. A method of manufacturing the lens mechanism is also disclosed.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of priority to U.S. Provisional Patent Application No. 63 / 481,480, filed January 25, 2023, the entire contents of which are incorporated herein by reference.

[0002] Field of Disclosure The present disclosure relates to lens configurations having stacked metasurfaces. [Background technology]

[0003] background A meta-optical element (MOE) is an example of an optical element that utilizes flat optics technology. MOEs have metasurfaces that include small, dispersed subwavelength structures (e.g., nanostructures or other meta-atoms) arranged to interact with light in specific ways. The meta-atoms can individually and / or collectively interact with light waves to change the local amplitude, local phase, or both of the incident light wave. MOEs can be used in optical applications to exploit the intrinsic properties imparted by an adapted phase function, for example, compared to conventional curved refractive lenses. Summary of the Invention [Means for solving the problem]

[0004] overview The present disclosure describes devices that include lens configurations with stacked metasurfaces and methods for manufacturing the lens configurations.

[0005] In one aspect, for example, the present disclosure describes an apparatus including a lens mechanism including a first substrate having a first metasurface and a second substrate having a second metasurface, the first and second metasurfaces being stacked and facing each other, and separated from each other by an adhesive that attaches the first and second substrates to each other.

[0006] Some implementations include one or more of the following features: For example, in some implementations, the first and second substrates are made of a glass material and the adhesive is a polymer adhesive; in some implementations, the first and second substrates are made of borosilicate glass; and in some implementations, the adhesive is optically transparent at infrared operating wavelengths.

[0007] In some implementations, the first metasurface faces the second metasurface with only the adhesive between them, and there is no air gap between the first and second metasurfaces. In some implementations, the lens mechanism, including the first and second substrates, the first and second metasurfaces, and the adhesive, has a total thickness of 100 microns (μm) or less. In some implementations, the lens mechanism, including the first and second substrates, the first and second metasurfaces, and the adhesive, has a total thickness of 10 microns or less. In some implementations, the lens mechanism, including the first and second substrates, the first and second metasurfaces, and the adhesive, has a total thickness of 1 micron or less.

[0008] In some applications, the lens arrangement further includes an aperture, possibly comprised of a layer of black chrome or structured resist applied to one of the metasurfaces or one of the substrates.

[0009] In some implementations, the lens arrangement further includes a third substrate having a third metasurface attached to the second substrate by an additional adhesive, and optionally, the third metasurface faces the second substrate with only the additional adhesive therebetween.

[0010] The present disclosure also describes a method that includes applying an adhesive to a surface of a first substrate having a metasurface, the first substrate being attached to a second substrate having a second metasurface such that the first and second metasurfaces are stacked and face each other, the first and second substrates being attached to each other by the adhesive, and the first and second metasurfaces being separated from each other by the adhesive.

[0011] Some implementations include one or more of the following features: For example, in some examples, the first and second substrates are made of a glass material, the adhesive is a polymer adhesive, and after attaching the first and second substrates to each other, the first metasurface faces the second metasurface with only the adhesive therebetween, and no air gap exists between the first and second metasurfaces.

[0012] In some implementations, the method includes thinning at least one of the first or second substrates. The thinning may include, for example, etching, grinding, and / or polishing. In some examples, the method includes thinning at least one of the first or second substrates until a combined thickness of the first and second substrates, the first and second metasurfaces, and the adhesive is 10 microns or less.

[0013] In some implementations, the lateral alignment precision between the first metasurface and the second metasurface is better than 50 μm, 20 μm, 10 μm, or 5 μm, and in some implementations, the lateral alignment precision between the first metasurface and the second metasurface is better than 1 μm.

[0014] In some implementations, the method includes attaching a third substrate to the second substrate with an additional adhesive, the third substrate having a third metasurface, the first, second, and third metasurfaces being stacked one on top of the other. In some examples, the third substrate is attached to the second substrate such that the third metasurface faces the second substrate with only the additional adhesive therebetween.

[0015] In some implementations, the method includes completely removing at least one of the first or second substrates. In some implementations, the method includes attaching a third substrate to the second metasurface with an additional adhesive, the third substrate having a third metasurface, the first, second, and third metasurfaces being stacked one on top of the other. In some examples, the third substrate is attached to the second substrate such that the third metasurface faces the second metasurface with only the additional adhesive therebetween.

[0016] Some implementations include one or more of the following advantages. For example, in some implementations, a lens configuration with two or more stacked metasurfaces can achieve a relatively short total track length (TTL), a small f-number, and / or improved overall imaging performance. In some cases, a first optical function can be realized on one metasurface and another, different optical function on a second metasurface. In some cases, stacked metasurfaces can facilitate a wide range of optical functions by having resonant interactions between the stacked metasurfaces. In some cases, stacked metasurfaces can facilitate the integration of an image sensor or light source with the metasurface stack, allowing the sensor or light source to be positioned relatively close to the metasurface stack. Such an arrangement can, in some cases, achieve a very compact (e.g., thin) optical device.

[0017] Other aspects, features, and advantages will be readily apparent from the following detailed description, the accompanying drawings, and the claims. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 illustrates an example of a lens configuration including stacked metasurfaces. [Figure 2A] 1A-1C illustrate stages in a method of manufacturing a lens configuration. [Figure 2B] 1A-1C illustrate stages in a method of manufacturing a lens configuration. [Figure 2C] 1A-1C illustrate stages in a method of manufacturing a lens configuration. [Figure 2D] 1A-1C illustrate stages in a method of manufacturing a lens configuration. [Figure 2E] 1A-1C illustrate stages in a method of manufacturing a lens configuration. [Figure 2F] 1A-1C illustrate stages in a method of manufacturing a lens configuration. [Figure 3A]FIG. 1 illustrates steps in a method for fabricating a lens configuration having three or more stacked metasurfaces. [Figure 3B] FIG. 1 illustrates steps in a method for fabricating a lens configuration having three or more stacked metasurfaces. [Figure 3C] FIG. 1 illustrates steps in a method for fabricating a lens configuration having three or more stacked metasurfaces. [Figure 4] FIG. 1 illustrates an example of a lens configuration with stacked metasurfaces and optical apertures. [Figure 5] FIG. 1 illustrates an example of a lens configuration with stacked metasurfaces and optical apertures. [Figure 6A] 1A-1C illustrate stages in a method of manufacturing a lens configuration. [Figure 6B] 1A-1C illustrate stages in a method of manufacturing a lens configuration. [Figure 6C] 1A-1C illustrate stages in a method of manufacturing a lens configuration. [Figure 6D] 1A-1C illustrate stages in a method of manufacturing a lens configuration. [Figure 6E] 1A-1C illustrate stages in a method of manufacturing a lens configuration. [Figure 6F] 1A-1C illustrate stages in a method of manufacturing a lens configuration. [Figure 7] FIG. 1 illustrates an example of an image sensor module including a lens configuration with stacked metasurfaces. [Figure 8] FIG. 1 illustrates an example of a light source module including a lens configuration with stacked metasurfaces. DETAILED DESCRIPTION OF THE INVENTION

[0019] Detailed Description This disclosure describes devices including lens configurations with stacked metasurfaces, and methods for manufacturing such lens configurations. In some implementations, lens configurations in which two or more metasurfaces are stacked can achieve a relatively short total track length (TTL), a small f-number, and / or improved overall imaging performance.

[0020] As shown in the example of FIG. 1, the lens arrangement 10 includes first and second substrates 12A, 12B attached (e.g., bonded) to one another. Each substrate 12A, 12B has a respective metasurface 14A, 14B on one side. Each metasurface 14A, 14B has carefully arranged "unit cells" or "meta-atoms" with subwavelength structures (e.g., nanostructures). The term "subwavelength" means that these nanostructures have at least one lateral dimension (a dimension parallel to the substrate on which the nanostructures are disposed) that is less than the wavelength of light incident thereon. The meta-atoms may be composed of, for example, silicon. Generally, the dimensions of the nanostructures correspond to the shortest wavelengths of interest. For example, in some implementations, the nanostructures may be in the form of nanoscale features with dimensions less than 1 micron. By adjusting the shape of these unit cell elements, the phase above these elements can be altered in response to a plane wave. With knowledge of the phase in terms of shape parameters, metalenses with any phase profile can be created by placing meta-atoms in the desired locations. In general, the derivative of the phase profile determines the ray bending. Each substrate, together with its respective metasurface, forms a metalens.

[0021] The substrates 12A, 12B, which may be composed of, for example, glass (e.g., borosilicate glass such as D263® glass manufactured by Schott), may be attached (e.g., glued) to one another by an adhesive 16A, such as a polymer adhesive that is optically transparent at operating wavelengths (e.g., infrared or visible wavelengths). In some implementations, the adhesive is index matched to the glass substrates 12A, 12B. The substrates are attached to one another so that the metasurfaces 14A, 14B are adjacent to one another. That is, the first metasurface 14A faces the second metasurface 14B with only a thin layer of adhesive 16A between them. In the example shown, there is no air gap between the metasurfaces 14A, 14B. In some cases, the overall thickness (T) of the lens arrangement 10 is about 10 microns (μm), and in some cases less. In some examples, incorporating stacks of metasurfaces into a lens arrangement as described herein facilitates a wide range of optical functions by having resonant interactions between the stacked metasurfaces. Such optical functions may include, for example, near-field interactions, filtering functions, and / or plasmonics.

[0022] 2A, 2B, 2C, 2D, 2E, and 2F illustrate various stages in a method for fabricating the device of FIG. 1. This method may, in some cases, be performed at the wafer level. As shown in FIG. 2A, first and second glass substrates 12A and 12B are provided, each of which has a respective metasurface 14A or 14B on its surface. In some examples, the initial thickness of each substrate 12A or 12B may be on the order of several hundred microns (e.g., 500 microns) to provide mechanical and structural integrity and a relatively planar surface for processing. As shown in FIG. 2B, a thin layer of optically transparent adhesive (e.g., a polymer adhesive) 16A is provided on one (or both) sides of the substrates 12A and 12B on which the metasurfaces 14A and 14B reside. The adhesive 16A may be applied, for example, by spin coating or spin jetting, or by other methods for applying a controlled amount of adhesive onto the substrate surface. Then, as shown in FIG. 2C, the two substrates 12A, 12B are brought into contact with each other with their respective metasurfaces 14A, 14B facing each other. In some implementations, the adhesive 16A between the substrates 12A, 12B can be cured thermally and / or by applying UV radiation. In some implementations, as shown by FIG. 2D, one or both of the substrates 12A, 12B can be thinned from the backside (i.e., the side opposite the metasurface) of the substrate to reduce the overall thickness of the resulting device. This thinning can be achieved, for example, by etching techniques, including dry etching (e.g., reactive ion etching (RIE)) and / or wet etching (e.g., hydrofluoric acid). Other thinning techniques include mechanical grinding and / or polishing. In some cases, thinning can be performed to reduce the overall device thickness (T) to 10 μm or less. If the above steps are performed at the wafer level, a dicing operation can then be performed to separate the wafer into individual devices.

[0023] In some implementations, as illustrated by Figures 2E and 2F, one or both of the substrates 12A, 12B may be completely removed by etching or other thinning techniques.

[0024] In some instances, the techniques described in this disclosure can help actively control the overall thickness of the stack, which in some cases can improve yield and reduce manufacturing costs.

[0025] In some implementations, further processing can be performed to provide a lens configuration in which three or more metasurfaces are stacked closely together. For example, as shown in FIG. 3A, at least one of the substrates in FIG. 2C (e.g., the second substrate 12B) can be thinned (e.g., etched) to leave only a thin layer of substrate material on the metasurface 14B. If a highly selective etch is used, the substrate 12B can be etched all the way down to (or nearly down to) the metasurface 14B. Next, as shown in FIG. 3B, the third substrate 12C with its respective third metasurface 14C is attached (e.g., glued) to the second substrate 12B with an adhesive 16B, such as a polymer adhesive that is optically transparent at the operating wavelength (e.g., infrared or visible wavelength). In some implementations, the adhesive is index-matched to the glass substrates 12B and 12C. The substrates are attached to each other so that the metasurfaces 14B and 14C are closely spaced from each other. That is, the third metasurface 14C faces the second metasurface 14B with only a thin layer of adhesive 16B and the remaining material (if any) of the second substrate 12B between them.

[0026] In some implementations, one or both of the outer substrates (i.e., the first substrate 12A and / or the third substrate 12C) may be etched from the backside of the substrate (i.e., the side opposite the metasurface) to reduce the overall thickness of the resulting lens configuration. In some implementations, at least one of the substrates is completely removed by etching or other thinning techniques. Etching techniques may include, for example, dry etching (e.g., RIE) and / or wet etching (e.g., hydrofluoric acid). FIG. 3C shows an example of a lens configuration 20 including three stacked metasurfaces 14A, 14B, and 14C after thinning (e.g., etching) the outer substrates 12A and 12C. In the resulting lens configuration 20, these substrates are attached (e.g., glued) to each other such that the metasurfaces 14A, 14B, and 14C form a stack and are adjacent or proximate to each other. That is, the first metasurface 14A faces the second metasurface 14B with only a thin layer of adhesive 16A between them, and the third metasurface 14C faces the second metasurface 14B with only a thin layer of adhesive 16B (and possibly a thin layer of the material of the second substrate 12B) between them. In the example shown, there are no air gaps between the metasurfaces 14A, 14B, and 14C.

[0027] In some implementations, further processing similar to that described in connection with Figures 3A-3C can be performed to provide additional metasurfaces in the stack. Providing more than two metasurfaces can be advantageous, for example, in achromatic lens implementations, and can generally improve the flexibility of lens design.

[0028] In some implementations, an optical aperture or stop 18 may be provided on the outer surface of one of the substrates (e.g., the first substrate 12A) to form an optical device 30, 40 including a lens configuration having a stack of two or more metasurfaces 14A, 14B, as shown in the examples of FIGS. 4 and 5. The aperture 18 may be constructed of, for example, black chrome or structured resist and, in some implementations, may help block unwanted light (e.g., stray light). In some examples (such as shown in FIG. 4), the aperture 18 may slightly overlap laterally with the location of the metasurface, while in other examples (such as shown in FIG. 5), the aperture 18 may not laterally overlap with the location of the metasurface. In some implementations, the aperture is applied to one of the metasurfaces.

[0029] FIGS. 6A, 6B, 6C, 6D, 6E, and 6F illustrate various stages in an example of a method for fabricating a lens configuration including an optical aperture. This method may, in some cases, be performed at the wafer level. As shown in FIG. 6A, first and second glass substrates 12A and 12B are provided, each of which has a respective metasurface 14A or 14B on its surface. In some examples, the initial thickness of each substrate 12A or 12B may be approximately several hundred μm (e.g., 500 μm) to provide mechanical and structural integrity and a relatively planar surface for processing. Additionally, a thin layer 18 (e.g., of black chrome or structured resist) is applied to the surface of one of the substrates 12A such that the layer 18 laterally surrounds the edge of the metasurface 14A. As shown in FIG. 6B, a thin layer of optically transparent adhesive (e.g., a polymer adhesive) 16A is provided on one (or both) sides of the substrates 12A and 12B on which the metasurfaces 14A and 14B reside. The adhesive 16A can be applied, for example, by spin coating or spin jetting, or by other methods for applying a controlled amount of adhesive onto the substrate surface. Then, as shown in FIG. 6C, the two substrates 12A, 12B are brought into contact with each other with their respective metasurfaces 14A, 14B facing each other. In some implementations, the adhesive 16A between the substrates 12A, 12B can be cured thermally and / or by applying UV radiation. In some implementations, as shown in FIG. 6D, one or both of the substrates 12A, 12B can be thinned from the backside (i.e., the side opposite the metasurface) of the substrate to reduce the overall thickness of the resulting device. This thinning can be achieved, for example, by etching techniques, including dry etching (e.g., reactive ion etching (RIE)) and / or wet etching (e.g., hydrofluoric acid). Other thinning techniques include mechanical grinding and / or polishing. In some cases, thinning can be performed to reduce the overall thickness (T) of the device to 10 μm or less.If the above steps are performed at the wafer level, a dicing operation can then be performed to separate the wafer into individual devices. In some implementations, as shown by Figures 6E and 6F, one or both of the substrates 12A, 12B can be completely removed by etching or other thinning techniques. The result in each of Figures 6D, 6E, and 6F is a lens feature including a stack of metasurfaces 14A, 14B and an optical aperture defined by layer 18.

[0030] The various lens mechanisms and optical devices described herein can be used in a wide range of applications, including optical imaging systems (e.g., cameras) and optical projection systems. FIG. 7 illustrates an example of a lens mechanism 50 having a stack of metasurfaces 14A and 14B. An image sensor 52 is disposed along the optical axis of the stack and positioned to receive light rays 54 passing through the stack of metasurfaces 14A and 14B. The image sensor 52 may be, for example, a CMOS sensor or a CCS sensor. FIG. 8 illustrates an example of a lens mechanism 60 having a stack of metasurfaces 14A and 14B. A light source 62 is operable to emit light (e.g., infrared or visible light) 64 toward the stack of metasurfaces 14A and 14B such that at least a portion of the light rays pass through the stack of metasurfaces 14A and 14B. In some implementations, the lens mechanism can help collimate light from the light source 62, which may include, for example, a vertical cavity surface-emitting laser (VCSEL) or a light-emitting diode (LED). Integrating an image sensor or light source with the metasurface stacks described in this disclosure can allow the sensor or light source to be positioned relatively close to the metasurface stack, potentially resulting in very compact (e.g., thin) optical devices.

[0031] A variety of modifications will be readily apparent from the above detailed description, and accordingly, other implementations are within the scope of the claims.

Claims

1. 1. An apparatus comprising: a lens arrangement including a first substrate having a first metasurface and a second substrate having a second metasurface; The device, wherein the first and second metasurfaces are stacked and face each other, and the first and second metasurfaces are separated from each other by an adhesive that attaches the first and second substrates to each other.

2. 10. The apparatus of claim 1, wherein the first and second substrates are made of a glass material and the adhesive is a polymer adhesive.

3. The device of any one of claims 1 to 2, wherein the adhesive is optically transparent to infrared radiation.

4. The device of any one of claims 1 to 3, wherein the first and second substrates are made of borosilicate glass.

5. 5. The device of claim 1, wherein the first metasurface faces the second metasurface with only the adhesive therebetween, and no air gap exists between the first and second metasurfaces.

6. 6. The device of claim 1, wherein the total combined thickness of the lens assembly, including the first and second substrates, the first and second metasurfaces, and the adhesive, is 10 microns or less.

7. 6. The device of claim 1, wherein the lens arrangement further comprises a third substrate having a third metasurface, the third substrate being attached to the second substrate by an additional adhesive.

8. 8. The device of claim 7, wherein the third metasurface faces the second substrate with only the additional adhesive therebetween.

9. 9. The device of claim 1, comprising at least one optical aperture on one of the metasurfaces or one of the substrates.

10. The device of any one of claims 1 to 9, wherein a lateral alignment accuracy between the first metasurface and the second metasurface is better than 50 μm.

11. The device of any one of claims 1 to 9, wherein a lateral alignment precision between the first metasurface and the second metasurface is better than 5 μm.

12. 1. A method comprising: applying an adhesive onto a surface of a first substrate having a metasurface; and attaching the first substrate to a second substrate having a second metasurface such that the first and second metasurfaces are stacked and face each other, wherein the first and second substrates are attached to each other by the adhesive and the first and second metasurfaces are separated from each other by the adhesive.

13. 13. The method of claim 12, wherein the first and second substrates are made of a glass material, the adhesive is a polymer adhesive, and after attaching the first and second substrates to each other, the first metasurface faces the second metasurface with only the adhesive therebetween and no air gap exists between the first and second metasurfaces.

14. The method of any one of claims 12 to 13, further comprising the step of thinning or completely removing at least one of the first or second substrates.

15. The method of claim 14 , wherein the thinning or completely removing step comprises etching.

16. 16. The method of claim 14, comprising thinning at least one of the first or second substrates until a combined thickness of the first and second substrates, the first and second metasurfaces, and the adhesive is 10 microns or less.

17. 17. The method of claim 12, further comprising attaching a third substrate to the second substrate by additional adhesive, the third substrate having a third metasurface, and the first, second, and third metasurfaces being stacked on top of each other.

18. 18. The method of claim 17, wherein the third substrate is attached to the second substrate such that the third metasurface faces the second substrate with only the additional adhesive between them.

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