Heterogeneous bonding optical waveguide sheet

Abstract

The utility model relates to a heterogeneous bonding optical waveguide sheet, which comprises an optical waveguide layer made of wide bandgap semiconductor materials and a glass substrate made of high refractive index glass, the optical waveguide layer is arranged on the glass substrate, and a grating structure is arranged on the surface, away from the glass substrate, of the optical waveguide layer. The high-refractive-index glass optical waveguide sheet solves the problems that the refractive index of an existing high-refractive-index glass optical waveguide sheet reaches 2.0, stray light is generated through secondary coupling out and the like, and has the advantages of being high in refractive index, large in FOV, full-color in single sheet and capable of reducing rainbow lines.

Description

Technical Field

[0001] The utility model relates to the technical field of optical elements, in particular to a heterogeneous bonded optical waveguide sheet. Background Art

[0002] Augmented reality technology, or AR technology, provides users with virtual information through images, videos, 3D models and other technologies while displaying real scenes, achieving a clever integration of virtual information and the real world. It is the next detonation point of information technology, and augmented reality glasses may replace mobile phones as the next generation of collaborative computing platform. Augmented reality technology represented by augmented reality glasses is currently beginning to rise in various industries, especially in the security and industrial fields. Augmented reality technology has demonstrated unparalleled advantages and greatly improved the way of information interaction. At present, the more mature optical display solutions in augmented reality technology are mainly divided into prism solutions, birdbath solutions, free-form surface solutions, off-axis holographic lens solutions and waveguide solutions.

[0003] Among many optical display solutions, the relief grating waveguide uses a relief grating (SRG) instead of the traditional catadioptric optical device (ROE) as the coupling, coupling and exit pupil expansion device in the waveguide solution. Due to its excellent performance, it is considered to be the most promising solution for consumer-grade AR glasses products. These gratings on the waveguide are designed for the wavelengths of red light, green light or blue light in the visible spectrum range. Through these gratings, virtual images or information are coupled into or decoupled from the optical waveguide, so that these images can be seen by the eyes. If the glass substrate used as a waveguide has a high refractive index, since the optical effect of AR glasses is usually determined by the minimum refractive index of the optical waveguide sheet, that is, the refractive index of the glass substrate in the red spectrum range, this high-refractive glass can make the light fully reflected in the waveguide, thereby reducing the leakage loss of light and reducing rainbow patterns, thereby achieving the effect of improving the field of view (FOV), optical clarity and light transmission efficiency.

[0004] The existing high-refractive glass material is relatively brittle, and the heavy glass component (i.e., the component with high molar mass) helps to improve the refractive index and mechanical reliability of the glass substrate, but at the same time it will increase the wearing weight and production cost of the glass substrate. At the same time, the refractive index of the current high-refractive glass has reached a bottleneck (about 2.0 refractive index), and there are also problems such as secondary outcoupling caused by the high refractive index to produce stray light, which has very limited effects on the improvement of the optical performance of AR lenses. Therefore, how to provide a new type of optical waveguide that has the advantages of high refractive index, large FOV, reduced rainbow patterns, etc., while also achieving a single-chip full-color image and avoiding secondary outcoupling to produce stray light is a problem that needs to be solved urgently. Summary of the invention

[0005] The problem to be solved by the utility model is to provide a heterogeneous bonded optical waveguide sheet in view of the above-mentioned deficiencies existing in the prior art, which solves the problems existing in the prior high-refractive glass optical waveguide sheet, such as the bottleneck of the refractive index reaching 2.0 and the secondary outcoupling generating stray light, and has the advantages of high refractive index, large FOV, single-chip full color and reduced rainbow pattern.

[0006] The above-mentioned invention object of the utility model is achieved through the following technical solutions:

[0007] A heterogeneous bonded optical waveguide sheet comprises an optical waveguide layer composed of a wide bandgap semiconductor material and a glass substrate composed of a high refractive index glass. The optical waveguide layer is arranged on the glass substrate, and the surface of the optical waveguide layer facing away from the glass substrate has a grating structure.

[0008] Specifically, in the optical waveguide lens of the present invention, the specific meaning of the "wide bandgap semiconductor material" refers to a semiconductor material with a bandgap width of 2.3 eV or above, and can be, for example, non-limitingly, one or a combination of silicon carbide (4H-SiC, 6H-SiC, 3C-SiC), gallium nitride (GaN), zinc oxide (ZnO), aluminum nitride (AlN), zinc selenide (ZnSe), indium gallium zinc oxide (IGZO), and diamond;

[0009] The specific meaning of the "grating structure" refers to an optical device composed of a large number of parallel slits of equal width and equal spacing, and can be, for example, a transmission grating and / or a reflection grating without limitation;

[0010] The specific meaning of the "high refractive index glass" refers to a high refractive index glass with a refractive index of 1.50 or above, and can be, for example, non-limitingly, silicate, borate, phosphate, fluoride and chalcogenide glass series or high refractive index dielectric materials such as doped titanium oxide, zirconium oxide, zinc oxide, aluminum oxide, etc.

[0011] Furthermore, the refractive index of the optical waveguide layer is greater than 2.60.

[0012] Furthermore, the optical waveguide layer is composed of silicon carbide material.

[0013] Furthermore, the thickness of the optical waveguide layer is 0.10-0.20 mm.

[0014] Furthermore, the grating structure is a sub-wavelength grating structure composed of a plurality of straight-tooth gratings, slanted-tooth gratings, and / or blazed gratings and arranged in a one-dimensional or two-dimensional array.

[0015] Furthermore, the refractive index of the glass substrate is 1.50-1.90.

[0016] Furthermore, the thickness of the glass substrate is 0.30-0.80 mm.

[0017] Furthermore, the optical waveguide layer is disposed on the glass substrate by direct bonding, warm pressure bonding, and / or optical bonding.

[0018] Furthermore, the bonding process of the optical waveguide layer and the glass substrate includes: subjecting the bonding surfaces of the optical waveguide layer and the glass substrate to plasma activation treatment respectively, stacking the optical waveguide layer and the glass substrate in a manner where the bonding surfaces are opposite to each other, and sequentially performing bonding and annealing treatments to form a Si-O-Si bonding surface between the optical waveguide layer and the glass substrate, thereby obtaining a heterogeneously bonded optical waveguide sheet.

[0019] Furthermore, before the plasma activation treatment, the wide bandgap semiconductor material and the high refractive index glass are cleaned separately by using an RCA cleaning method.

[0020] Furthermore, during the plasma activation treatment, the O2 flow rate is controlled to be 15-25 sccm, the power is controlled to be 80-120 W, and the time is controlled to be 50-70 s.

[0021] Furthermore, during the bonding process, the bonding between the optical waveguide layer and the glass substrate is completed from the center to the edge.

[0022] Furthermore, during the annealing process, the temperature is controlled to be 200-400° C. and the time is 1-3 hours.

[0023] Specifically, the bonding process of the optical waveguide layer and the glass substrate includes:

[0024] S1 cleaning: using RCA cleaning method to clean wide bandgap semiconductor materials and high refractive index glass respectively, and drying with nitrogen to obtain optical waveguide layer and glass substrate;

[0025] S2 plasma activation, firstly placing the S1 with the bonding surface facing upward to obtain the optical waveguide layer and the glass substrate, then bombarding the surfaces of the optical waveguide layer and the glass substrate respectively with O2 plasma, and controlling the O2 flow rate to be 20 sccm, the power to be 100 W, and the time to be 60 s; wherein the plasma activation can activate the Si-O bonds on the surfaces of the optical waveguide layer and the glass substrate, and make them hydrophilic;

[0026] S3 bonding, first stacking the S2 in a manner that the bonding surfaces are opposite to each other to obtain the optical waveguide layer and the glass substrate, then completing the bonding between the optical waveguide layer and the glass substrate from the center to the edge, and exhausting the air between the optical waveguide layer and the glass substrate to obtain a temporary bonded optical waveguide sheet; wherein the interface between the optical waveguide layer and the glass substrate is rich in =O bonds, which combine with water vapor in the air to form -OH bonds, and the van der Waals force of hydrogen bonds causes the surfaces of the optical waveguide layer and the glass substrate to adhere to each other, thereby obtaining a temporary bond of a certain strength;

[0027] S4 annealing, heat treating the temporarily bonded optical waveguide sheet obtained in S3, and controlling the temperature to be 200-400°C for 1-3 hours to obtain a heterogeneous bonded optical waveguide sheet; wherein the annealing heat treatment reduces the -OH bonds on the bonding surface into water molecules, forming a Si-O-Si bonding surface with stronger bonding force, and discharges water vapor to achieve the conversion of van der Waals force to covalent bond, thereby greatly increasing the bonding strength between the optical waveguide layer and the glass substrate.

[0028] In summary, the beneficial technical effects of the utility model are:

[0029] 1. If silicon carbide or high-refractive-index glass is used alone as the material of the optical waveguide sheet, as the thickness of the optical waveguide sheet decreases and the refractive index increases, the total reflection path inside it is shorter, and it is reflected multiple times onto the coupling-out grating, which in turn increases the probability of secondary coupling-out and generates more stray light. Based on the purpose of improving the thinning and high-refractive-index optical waveguide sheet, and in order to avoid the disadvantages brought about by the above-mentioned improvements, the utility model adopts a silicon carbide optical waveguide layer to bond a high-refractive-index glass substrate, and integrally processes the grating structure on the silicon carbide optical waveguide layer, which is beneficial to increase the lateral transmission distance of the small-angle diffracted light, reduce the secondary diffraction of the light, and avoid the stray light generated thereby;

[0030] 2. The present invention can realize full-color display through a single optical waveguide, increase the lateral transmission distance of small-angle diffracted light, and reduce the chromatic aberration caused by the secondary diffraction of light; according to the grating equation ndsinθ=kλ, sinθ=kλ / nd, sinθ R -sinθ G = k(λ R -λ G ) / nd, Δθ=kΔλ / nd; where n is the refractive index, θ R and θ G are the diffraction angles of red light and green light respectively; therefore, under the same light transmission, the greater the refractive index, the smaller the diffraction angle difference and the smaller the chromatic aberration;

[0031] 3. The utility model uses silicon carbide material with a refractive index of 2.6 or more bonded to high-refractive-index glass with a refractive index of 1.5 or more, which can enable the optical waveguide to break through the refractive index bottleneck of 2.0, thereby increasing the bending angle of light propagating in the optical waveguide, ultimately increasing the field of view angle and reducing the range of external stray light affected by rainbow patterns. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a structural schematic diagram of Example 1.

[0033] Figure 2 It is a structural schematic diagram of the total reflection distance calculation method of Examples 1 to 6 and Comparative Example 2.

[0034] In the figure, 1. optical waveguide layer; 11. grating structure; 2. glass substrate. DETAILED DESCRIPTION

[0035] In order to make the technical means, creative features, objectives and functions achieved by the present invention clearer and easier to understand, the present invention is further described below in conjunction with the accompanying drawings and specific implementation methods.

[0036] Example 1: Reference Figure 1 , is a heterogeneous bonded optical waveguide sheet disclosed in the utility model, comprising an optical waveguide layer 1 composed of a wide bandgap semiconductor material, and a glass substrate 2 composed of a high refractive index glass, the optical waveguide layer 1 is arranged on the glass substrate 2, and the surface of the optical waveguide layer 1 away from the glass substrate 2 has a grating structure 11. In order to make the optical waveguide sheet have the advantages of high refractive index, large FOV, single-chip full color, and reduced rainbow pattern:

[0037] The refractive index of the optical waveguide layer 1 is above 2.60 and is made of silicon carbide material, and the thickness of the optical waveguide layer 1 is 0.10-0.20 mm;

[0038] The grating structure 11 is a sub-wavelength grating structure 11 composed of a plurality of straight tooth gratings, slanted tooth gratings, and / or blazed gratings and arranged in a one-dimensional or two-dimensional array;

[0039] The refractive index of the glass substrate 2 is 1.50-1.90, and the thickness of the glass substrate 2 is 0.30-0.80 mm;

[0040] In addition, the optical waveguide layer 1 is disposed on the glass substrate 2 by direct bonding, which is specifically implemented as follows:

[0041] S1 cleaning, using the RCA cleaning method to clean the wide bandgap semiconductor material and the high refractive index glass respectively, and drying with nitrogen to obtain the optical waveguide layer 1 and the glass substrate 2;

[0042] S2 plasma activation, firstly placing S1 with the bonding surface facing upward to obtain the optical waveguide layer 1 and the glass substrate 2, then using O2 plasma to bombard the surfaces of the optical waveguide layer 1 and the glass substrate 2 respectively, and controlling the O2 flow rate to be 20sccm, the power to be 100W, and the time to be 60s; wherein, the plasma activation can activate the Si-O bonds on the surfaces of the optical waveguide layer 1 and the glass substrate 2, and make them hydrophilic;

[0043] S3 bonding, first stacking S2 in a manner that the bonding surfaces are opposite to each other to obtain the optical waveguide layer 1 and the glass substrate 2, then completing the bonding between the optical waveguide layer 1 and the glass substrate 2 from the center to the edge, and exhausting the air between the optical waveguide layer 1 and the glass substrate 2 to obtain a temporary bonded optical waveguide sheet; wherein, the interface between the optical waveguide layer 1 and the glass substrate 2 is rich in =O bonds, which combine with water vapor in the air to form -OH bonds, and the van der Waals force of hydrogen bonds will make the surfaces of the optical waveguide layer 1 and the glass substrate 2 adhere to each other, thereby obtaining a temporary bond of a certain strength;

[0044] S4 annealing, heat treating the temporarily bonded optical waveguide sheet obtained in S3, and controlling the temperature to 200-400°C for 1-3 hours to obtain a heterogeneous bonded optical waveguide sheet; wherein the annealing heat treatment reduces the -OH bonds on the bonding surface into water molecules, forming a Si-O-Si bonding surface with stronger bonding force, and discharges water vapor to achieve the conversion of van der Waals force to covalent bond, thereby greatly increasing the bonding strength between the optical waveguide layer 1 and the glass substrate 2.

[0045] Embodiments 2 to 6 are heterogeneous bonded optical waveguide sheets disclosed in the present invention. The difference from Embodiment 1 is that the technical parameters of the optical waveguide layer 1 and the glass substrate 2 are shown in Table 1.

[0046] Comparative Examples 1-2 are heterogeneous bonded optical waveguide sheets disclosed in the present invention, which are different from Example 1 in that the technical parameters of the optical waveguide layer 1 and the glass substrate 2 are shown in Table 1.

[0047] Table 1

[0048] Optical waveguide layer thickness Glass substrate refractive index Glass substrate thickness FOV Total reflection distance Example 1 0.1mm 1.8 0.4mm 82° 0.67mm Example 2 0.15mm 1.8 0.35mm 82° 0.64mm Example 3 0.2mm 1.8 0.3mm 82° 0.61mm Example 4 0.15mm 1.5 0.35mm 82° 0.83mm Example 5 0.15mm 1.6 0.35mm 82° 0.75mm Example 6 0.15mm 1.7 0.35mm 82° 0.69mm Comparative Example 1 0mm 1.8 0.5mm 25° 0.67mm Comparative Example 2 0.5mm 1.8 0mm 82° 0.40mm

[0049] Among them, refer to Figure 2 , total reflection distance calculation method: the incident light is uniformly calculated as -30°, the grating period P=300nm, the wavelength lamda=456nm(B); according to the grating equation, the corresponding diffraction angle in SiC is calculated to be 23.2°, and the corresponding diffraction angle in high-refractive glass under different refractive indices; the greater the total reflection distance, the smaller the effect of secondary diffraction, and the higher the corresponding efficiency under the same conditions.

[0050] As can be seen from Table 1, if 1.8 refractive index glass is used alone as the optical waveguide, the FOV is 25° (very small); if SiC material is used alone as the optical waveguide, the total reflection distance is very small, the secondary diffraction effect is large, the light efficiency loss is large, and the image effect entering the human eye is poor. The rest are combinations of SiC with different thicknesses and high-refractive glass with different parameters. As long as 11 layers of the grating structure are SiC, the FOV can be increased to 82°. In addition, as the refractive index of the lens increases, the FOV increases, and the corresponding angle of rainbow pattern generation decreases (the rainbow pattern effect is reduced).

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the utility model rather than to limit it. Although the utility model has been described in detail with reference to the preferred embodiments, ordinary technicians in the field should understand that the technical solution of the utility model can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the utility model, which should be included in the scope of the claims of the utility model.

Claims

1. A heterogeneous bonded optical waveguide sheet, characterized in that: The invention comprises an optical waveguide layer (1) composed of a wide bandgap semiconductor material and a glass substrate (2) composed of a high refractive index glass. The optical waveguide layer (1) is arranged on the glass substrate (2), and a surface of the optical waveguide layer (1) facing away from the glass substrate (2) has a grating structure (11).

2. The heterojunction bonded optical waveguide according to claim 1, characterized in that: The refractive index of the optical waveguide layer (1) is above 2.

60.

3. The heterojunction-bonded optical waveguide according to claim 2, characterized in that: The optical waveguide layer (1) is made of silicon carbide material.

4. The heterojunction-bonded optical waveguide sheet according to claim 3, characterized in that: The thickness of the optical waveguide layer (1) is 0.10-0.20 mm.

5. The heterojunction bonded optical waveguide according to claim 1, characterized in that: The grating structure (11) is a sub-wavelength grating structure (11) composed of a plurality of straight-tooth gratings, slanted-tooth gratings, and / or blazed gratings and arranged in a one-dimensional or two-dimensional array.

6. The heterojunction bonded optical waveguide according to claim 1, characterized in that: The refractive index of the glass substrate (2) is 1.50-1.

90.

7. The heterojunction-bonded optical waveguide sheet according to claim 6, characterized in that: The thickness of the glass substrate (2) is 0.30-0.80 mm.

8. The heterojunction-bonded optical waveguide sheet according to claim 1, characterized in that: The optical waveguide layer (1) is arranged on the glass substrate (2) by direct bonding, warm pressure bonding, and / or optical bonding.

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