Optical device including a protected lens

Abstract

This disclosure describes, among other things, optical devices in which a lens structure is closer to an aperture substrate than a support on which the lens structure is disposed. The lens structure includes meta-atoms defined across a metasurface distributed across a surface of the lens substrate support and configured to alter the local amplitude, local phase, or both of an optical wave at an applied wavelength. This disclosure also describes assemblies incorporating one or more such optical devices, and methods for manufacturing the optical devices.

Description

[Technical Field]

[0001] Field of Disclosure SUMMARY The present disclosure relates to optical devices that include protected lenses.

[0002] background Wafer-level lamination is sometimes used to align optical apertures to lenses during the fabrication of optical devices, and in some cases, subsequent handling of the optical device can scratch or otherwise damage the lenses.

[0003] overview This disclosure describes optical devices in which a lens structure distributed across the surface of a glass or other support faces an optical substrate having optical structures. This disclosure also describes assemblies incorporating one or more such optical devices, and methods for making the optical devices and assemblies.

[0004] For example, in one embodiment, the present disclosure describes an apparatus including an aperture substrate, a lens substrate, and a spacer. The aperture substrate has an optical aperture. The lens substrate includes a lens structure on a support, the lens structure being closer to the aperture substrate than the support. The lens structure includes meta-atoms defined across a metasurface distributed across a surface of the support and configured to change the local amplitude, local phase, or both of an optical wave at an applied wavelength. The support is transparent to the applied wavelength. A first end of the spacer is attached to the aperture substrate, and a second end of the spacer is attached to either the lens substrate or a protective cover over the metasurface. The aperture extends from the first end to the second end through the spacer, and the aperture has a refractive index of 1.0 or less.

[0005] Some embodiments include one or more of the following features. For example, in some embodiments, the aperture substrate includes a first support having a metal layer disposed thereon, the metal layer defining an optical aperture, and the first support being transparent to the applied wavelength. In some embodiments, the lens structure faces the optical aperture, while in some embodiments, the lens structure faces the first support. In some cases, the support having the lens structure disposed thereon and the first support having the metal layer disposed thereon are made of glass. In some embodiments, the metal layer defining the optical aperture is made of a black chrome coating. In some embodiments, the opening in the spacer contains air.

[0006] In some embodiments, the apparatus further includes an image sensor positioned such that light entering through the optical aperture passes through the lens structure and then impinges on the image sensor.

[0007] The present disclosure also describes a method for manufacturing an optical device. For example, in one embodiment, the method includes providing a first wafer having a metal layer disposed thereon, the metal layer defining optical apertures, the first wafer being transparent to an applied wavelength. The method includes providing a second wafer having a lens structure on a surface thereof, the lens structure being defined by meta-structures distributed across the surface of the second wafer and including meta-atoms configured to alter the local amplitude, local phase, or both of an optical wave at the applied wavelength, the second wafer being transparent to the applied wavelength. The method further includes providing a spacer wafer, wherein there are apertures extending through the spacer wafer from a first side of the spacer wafer to a second side of the spacer wafer, the apertures having a refractive index of 1.0 or less. The first side of the spacer wafer is attached to the first wafer, and the second side of the spacer wafer is attached to either a second wafer or a protective cover covering the meta-structures to form a wafer stack, such that the lens structure is closer to the first wafer than to the second wafer, and each of the optical apertures is aligned with a corresponding one of the apertures in the spacer wafer.

[0008] Some embodiments include one or more of the following features. For example, in some embodiments, the method includes separating the wafer stack into individual optical devices. In some embodiments, the method includes providing an image sensor such that light entering through an optical aperture of one of the individual optical devices passes through a lens structure and then incident on the image sensor.

[0009] Some embodiments may provide one or more of the following advantages. For example, locating the lens structure on the side of the lens substrate facing the aperture substrate may reduce the likelihood of scratching or otherwise damaging the lens structure during subsequent handling of the optical device. The presence of air or other low-index optically transparent material core region (e.g., in place of glass) between the active region of the lens structure and the aperture may, in some cases, result in an optical device with a relatively small total z-height and / or a small total track length (TTL). Also, in some embodiments, using a relatively thin glass substrate to support the lens structure may help to keep the effects of optical aberrations caused by converging light rays passing through the flat surface of the glass substrate relatively small.

[0010] Other aspects, features, and advantages will become readily apparent from the following detailed description, the accompanying drawings, and the claims. [Brief explanation of the drawings]

[0011] [Figure 1] 1 shows an example of an optical device. [Figure 2] 2 illustrates a stage in wafer-level fabrication of an optical device similar to that of FIG. 1; [Figure 3] 2 illustrates a stage in wafer-level fabrication of an optical device similar to that of FIG. 1; [Figure 4] 2 illustrates an example of an optical assembly including the optical device of FIG. 1. [Figure 5]5 illustrates an example of a light beam sensed by the optical assembly of FIG. 4. [Figure 6] 1 illustrates another example of an optical device. [Figure 7] 1 illustrates further examples of optical devices. [Figure 8] 1 illustrates yet another example of an optical device. DETAILED DESCRIPTION OF THE INVENTION

[0012] Detailed Description This disclosure describes optical devices in which the active region of the lens structure faces an aperture substrate, thereby providing protection within the interior region of the device. Some of the embodiments described below refer to meta-optical elements (MOEs) as an example of a lens structure. However, the devices and techniques described in this disclosure can also be used with other types of lenses (e.g., diffractive optical elements (DOEs)) distributed across the surface of a glass or other transparent support.

[0013] 1, optical device 10 includes an aperture substrate 12, a spacer 14 attached to aperture substrate 12, and a lens substrate 16 attached to spacer 14. Substrates 12, 16 and wafer 14 are stacked together with spacer 14 disposed between aperture substrate 12 and lens substrate 16.

[0014] The aperture substrate 12 includes an aperture 18 defined, for example, by a metal layer (e.g., a black chrome coating) 22 on the surface of a first support 20. The support 20 is transparent to the intended application wavelength or range of wavelengths for the device 10 (e.g., infrared (IR), IR, or visible light). For example, in some embodiments, the application wavelength may be 940 nm, 1380 nm, or 1550 nm. The support 20 may be constructed, for example, from glass or other transparent materials. In some embodiments, the first support 20 is constructed from D263® T glass, a nearly colorless, flat, borosilicate thin glass manufactured by SCHOTT. Other types of glass or transparent materials (e.g., SCHOTT MEMpax® ultra-thin borosilicate glass) may also be used in some embodiments.

[0015] Lens substrate 16 includes a lens structure 26 on a surface of a second support 24. Support 24 is also transparent to the intended application wavelength or range of wavelengths for device 10 and may be composed of, for example, glass. In some embodiments, support 24 is composed of D263® T glass. Other types of glass or transparent materials may be used in some embodiments.

[0016] In some embodiments, lens structures 26 are defined throughout a metasurface, sometimes referred to as a metastructure. Metastructures can include small structures (e.g., nanostructures or other meta-atoms) distributed across the surface of support 24 and arranged to interact with light in specific ways. The nanostructures can interact with light waves individually or collectively. For example, the nanostructures or other meta-atoms can change the local amplitude, local phase, or both, of an incident light wave.

[0017] When the meta-atoms (e.g., nanostructures) of a metasurface are in a specific arrangement, the metasurface can function as an optical element such as a lens, lens array, beam splitter, diffuser, polarizer, bandpass filter, or other optical element. In some cases, the metasurface can perform optical functions originally performed by refractive and / or diffractive optical elements. The meta-atoms may, in some cases, be arranged in a pattern so that the metastructure functions, for example, as a lens, grating coupler, or other optical element. In other cases, the meta-atoms need not be arranged in a pattern, and the metastructure can function, for example, as a fan-out grating, diffuser, or other optical element. In some embodiments, the metasurface can perform other functions, including polarization control, negative index transmission, beam deflection, vortex generation, polarization conversion, optical filtering, and plasmonic optical functions.

[0018] In the example shown in FIG. 1 , the lens structure 26 includes an optically active region 27 laterally surrounded by an optically inactive region 29. One end of the spacer can be attached to the optically inactive region 29 of the lens substrate 16. The spacer 14, which separates the aperture 18 a certain distance from the lens structure 26, can also be constructed of, for example, glass. Additionally, the spacer 14 can have an aperture 28 extending from one side of the spacer to the other. In such an arrangement, the space within the aperture 28 can have a refractive index of 1.0 or less. For example, the aperture 28 can contain a vacuum or can be filled with a substance (e.g., air) that is optically transparent at the wavelength of application. Such a configuration can, in some embodiments, enable the optical device to have a relatively small total z-height and / or a relatively small total track length (TTL). Embodiments in which the aperture 28 contains air or a vacuum may be preferable over, for example, filling the aperture with an epoxy or polymer material, which can adversely affect optical performance due to the higher refractive index of such materials.

[0019] 1 , lens structure 26 is disposed on a surface of second support 24 that faces aperture substrate 12. That is, lens structure 26 faces aperture 18 rather than being disposed on an exterior surface of optical device 10. Such an arrangement allows lens structure (e.g., meta-atoms) 18 to be protected within an interior region 28 defined by the housing of optical device 10, thereby reducing the likelihood of scratches or other damage to lens structure 26 during subsequent handling of optical device 10.

[0020] The arrangement of FIG. 1 may, in some cases, be less costly and / or complex to manufacture than a situation in which the lens structure is disposed on the outer surface of a lens substrate and encapsulated for protection. While converging light rays passing through the flat surface of glass support 24 can cause optical aberrations, such aberrations depend largely on the thickness of support 24 and its refractive index. Therefore, by using a relatively thin support, the effects of such aberrations can be kept relatively small. For example, in some cases, support 24 may have a thickness of approximately 200 μm. In some embodiments, other thicknesses may be appropriate.

[0021] As described above, the optical device 10 can be fabricated, for example, by a wafer-level process, an example of which is described in connection with FIGS. 2 and 3. As shown in FIG. 2, a first transparent (e.g., glass) wafer 120 is provided having a thin metal layer 22, e.g., a black chrome coating, on its surface. The thin metal layer 22 defines an optical aperture 18. A second transparent (e.g., glass) wafer 124 is also provided having a lens structure 26 on its surface. The lens structure 26 can include, for example, a metastructure composed of nanostructures, such as meta-atoms. In other embodiments, the lens structure 26 can be composed of other types of lenses (e.g., DOEs) distributed across the surface of the second wafer 124. A spacer wafer 114, e.g., made of glass, is also provided. The spacer wafer 114 includes apertures 28, each of which extends from a first side to a second, opposite side through the spacer wafer. The spaces defined by the apertures 28 can have a refractive index of, for example, 1.0 or less and can be optically transparent at the applicable wavelength. For example, the opening 28 can contain air or a vacuum.

[0022] Next, as shown in FIG. 3, a first wafer 120 is attached to a first side of the spacer wafer 114, and a second wafer 124 is attached to a second, opposite side of the spacer wafer 114 to form a wafer stack. The first and second wafers 120, 124 are attached to the spacer wafer 114 such that the active areas of the lens structures 26 on the second wafer 124 face the first wafer 120 (or the thin metal layer 22 that defines the optical apertures 18). The wafers 120, 124 can be attached to the spacer wafer 114 by, for example, an adhesive. The wafer structure can then be separated into individual optical devices by, for example, dicing along dicing lines 150.

[0023] The optical device 10 can be incorporated into an optoelectronic assembly, such as a light-sensing module. As shown in the examples of FIGS. 4 and 5 , such an assembly 32 can include an image sensor 30 positioned such that light 140 entering the optical device 10 through the aperture 18 passes through a lens structure 26 before impinging on the image sensor 30. For example, if the lens structure 26 is implemented as a metasurface including meta-atoms, the meta-atoms can alter the local amplitude, the local phase, or both, of the incident light wave 140. After passing through the lens structure 26, the altered light wave 142 is incident on the image sensor 30.

[0024] During assembly of the module, optical device 10, including lens structure 26, can be placed in a lens holder and actively aligned with image sensor 30 before being fixed in place on the image sensor. Because lens structure 26 faces opening 18, the lens structure can be more easily protected from scratches or other damage that might otherwise occur during assembly.

[0025] While the foregoing embodiments show the aperture 18 and metal layer (e.g., black chrome coating) 22 facing the lens structure 26, in some embodiments, the metal layer (e.g., black chrome coating) 22 may be external to the first support 20, such that the metal layer 22 faces outward from the lens structure, as shown in the exemplary optical device 10A of FIG. 6. Nevertheless, in both this and other examples above, the lens structure 26 faces the aperture substrate 12, which includes the first support, on which the metal layer that defines the optical aperture is disposed. The optical device 10A can also be incorporated into an optoelectronic assembly, such as a light-sensing module.

[0026] The embodiments of Figures 5 and 6 may present trade-offs in some cases. For example, varying the refractive index between the aperture stop and the nanostructures can affect optical performance. Thus, in the embodiment of Figure 6, the support (i.e., cover glass) 20 is located after the aperture stop, and the refractive index varies between the aperture stop and the nanostructures. As a result, optical aberrations may slightly degrade optical performance. On the other hand, in the embodiment of Figure 5, where the cover glass is located before the aperture stop, the presence of the cover glass does not affect optical performance. Nevertheless, a potential benefit of using the embodiment of Figure 6 is that the device can be made more compact compared to the embodiment of Figure 5. For example, if the cover glass 20 in Figure 6 is sufficiently thin (e.g., on the order of about 200 µm, or even less in some cases), little optical performance is lost and a very compact device can still be achieved. Furthermore, in such a design, the nanostructures can still be protected from both sides.

[0027] In some embodiments, the cover glass 20 can be omitted, as shown in the exemplary optical device 10B of FIG. 7. That is, the aperture substrate 12 defines the aperture 18, but the cover glass 20 is not present. Because the aperture stop does not have a cover glass, a very compact design can be achieved. Furthermore, because the lens structure 26 still faces the aperture substrate 12, the meta-atoms (e.g., nanostructures) of the lens structure 26 can be substantially protected within the housing.

[0028] In some embodiments, as shown in the example of FIG. 8 , the lens structure 26 (i.e., the metasurface) of device 10C is covered by a protective cover 50 disposed on the side of the metasurface opposite support 24. This arrangement can provide even more protection for the metasurface. In some embodiments, the protective cover 50 is, for example, an encapsulation layer composed of a material that is optically transparent at the wavelength of interest. For example, in some cases, the encapsulation layer 50 is composed of a polymer. The encapsulation layer 50 can be relatively thin (e.g., in some cases 1-3 μm) to reduce the extent of any adverse effects on optical performance. In some embodiments, the protective cover 50 is a relatively thin cover glass. For example, the protective cover 50 can be embodied as SCHOTT MEMpax® ultra-thin borosilicate glass having a thickness of, for example, 70 μm. In some embodiments, other materials and / or thicknesses may be used for the protective cover 50.

[0029] In some cases, one or more light-sensing modules as described above may be incorporated into, for example, a mobile phone, a laptop, a television, a wearable device, or an automotive vehicle.

[0030] While this specification contains many details, these should not be construed as limitations on the scope of the disclosure or what may be claimed, but rather as descriptions of features specific to particular embodiments. Certain features described herein in the context of separate embodiments may also be combined in the same embodiment. Conversely, various features described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable subcombination. Various modifications can be made to the foregoing examples. Accordingly, other embodiments are within the scope of the claims.

Claims

1. An aperture substrate having an optical aperture, A lens substrate comprising a lens structure on a support, wherein the lens structure is closer to the aperture substrate than the support, and the lens structure comprises metaatoms defined across the entire metasurface distributed across the surface of the support and configured to change the local amplitude, local phase, or both of a light wave at the applicable wavelength, and the support is transparent to the applicable wavelength, A spacer wherein the first end of the spacer is attached to the opening substrate, and the second end of the spacer is attached to either the lens substrate or a protective cover covering the meta surface, A device equipped with, An apparatus wherein the opening extends from the first end to the second end via the spacer, and the opening has a refractive index of 1.0 or less.

2. The apparatus according to claim 1, wherein the aperture substrate includes a first support on which a metal layer is disposed, the metal layer defines the optical aperture, and the first support is transparent to the applicable wavelength.

3. The apparatus according to claim 2, wherein the lens structure faces the optical aperture.

4. The apparatus according to claim 2, wherein the lens structure faces the first support.

5. The apparatus according to any one of claims 2 to 4, wherein the support on which the lens structure is arranged and the first support on which the metal layer is arranged are made of glass.

6. The apparatus according to any one of claims 2 to 4, wherein the metal layer defining the optical aperture is made of a black chrome coating.

7. The apparatus according to any one of claims 1 to 4, wherein the opening contains air.

8. The apparatus according to claim 1, wherein the lens structure includes an optically active region laterally surrounded by an optically inert region, and the second end of the spacer is attached to the optically inert region of the lens structure.

9. The light entering through the optical aperture passes through the lens structure and is then incident on the image sensor, which is positioned to receive light. The apparatus according to any one of claims 1 to 4, further comprising:

10. To provide a first wafer on which a metal layer is arranged, wherein the metal layer defines an optical aperture and the first wafer is transparent with respect to the applicable wavelength, To provide a second wafer, the second wafer having a lens structure on its surface, the lens structure being defined by a metastructure distributed across the surface of the second wafer and containing metaatoms configured to change the local amplitude, local phase, or both of a light wave at the applicable wavelength, and the second wafer being transparent to the applicable wavelength. To provide a spacer wafer, wherein an opening exists through the spacer wafer extending from a first side of the spacer wafer to a second side of the spacer, and the opening has a refractive index of 1.0 or less. The first side of the spacer wafer is attached to the first wafer, and the second side of the spacer wafer is attached to either the second wafer or a protective cover covering the metastructure to form a wafer stack, wherein the lens structure is closer to the first wafer than to the second wafer, and each of the optical apertures is aligned with a corresponding one of the apertures of the spacer wafer. Methods that include...

11. Separating the wafer stack into individual optical devices The method according to claim 10, further comprising:

12. To provide an image sensor such that light entering through one of the individual optical devices passes through the lens structure and is then incident on the image sensor. The method according to claim 10, further comprising:

13. The method according to any one of claims 10 to 12, wherein the first wafer and the second wafer are made of glass.

14. The method according to claim 13, wherein the spacer wafer is made of glass.

15. The method according to any one of claims 10 to 12, wherein the metal layer defining the optical aperture is made of a black chrome coating.

16. The method according to any one of claims 10 to 12, wherein the opening contains air.

17. The method according to claim 10, wherein the lens structure includes optically active regions, each laterally surrounded by corresponding optically inert regions, and the method comprises attaching the optically inert regions to the second side of the spacer wafer.

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