CN110426850A - The waveguide of the full-color coupling of single layer shows grating coupler - Google Patents

Abstract

The invention relates to the field of diffraction gratings, and aims to provide a single-layer full-color coupled waveguide display grating coupler. The coupler should have the performance of realizing high-efficiency coupling with a single-layer waveguide grating in a wide visible spectrum range. For this reason, the technical solution adopted by the present invention is that the single-layer full-color coupled waveguide display grating coupler includes: the waveguide is a transparent substrate, and a grating layer with the same material or similar refractive index as the transparent substrate layer, and the grating layer has a high refractive index. High refractive index material film layer, and metal film layer on high refractive index material. The shape, period, groove depth, groove top angle, material of the grating layer, the thickness and the refractive index of the high refractive index layer, and the thickness and the value of the refractive index of the metal film layer make the grating In the visible light spectrum range of 450nm-700nm, the first-order diffraction efficiency is higher than 70%. The invention is mainly applied to the design and manufacture occasions of the grating coupler.

Description

Single layer full color coupled waveguide display grating coupler

technical field

The invention relates to the field of diffraction gratings, relates to a single-layer full-color coupled waveguide display grating coupler, in particular to a single-layer full-color coupled waveguide display grating coupler for an optical see-through augmented reality display system.

Background technique

In recent years, the application of augmented reality technology Augmented Reality (AR) in the military, industry, medical, construction, education, tourism, navigation, sports and entertainment, communication media and other fields has developed rapidly. The display technology based on grating-optical waveguide has the advantages of large exit pupil, large field of view, lightness, compactness, and high transmittance, and can realize a device similar to glasses to achieve real mobility and all-day use. Color waveguide display technology provides more complete information display, increases the scope of application of waveguide display systems, and improves user experience. Full-color display is important and necessary for waveguide projection display systems to develop into consumer electronics products. In order to realize full-color waveguide display based on gratings, the existing schemes are mainly based on volume holographic gratings with multi-period characteristics, such as multilayer volume holographic gratings and multiplexed volume holographic gratings. Each layer of the multi-layer volume holographic grating is a single exposure, which is only sensitive to one wavelength. The three primary colors of red, green and blue can be modulated at the same time by overlapping three layers, while the multiplexed volume holographic grating is exposed in multiple steps. At the same time, it is sensitive to the light of three primary colors. The coupling gratings in these designs have different grating periods for different colors of light, enabling full-color incident light to be coupled into the waveguide plate. Although the diffraction efficiency of the volume holographic grating is high, the field of view of the system is small due to the angular selectivity of the holographic grating. Moreover, the holographic grating requires special high refractive index modulation to achieve high uniformity and high efficiency, and also requires precise control of conditions such as temperature, humidity, exposure time, and interference optical path accuracy. In addition, volume holographic materials are sensitive to temperature and humidity, which makes it difficult to preserve the holographic grating waveguide display.

Therefore, for the head-mounted waveguide display system, it is necessary to look for a coupling device with a single-chip waveguide structure that can have high diffraction efficiency in a certain range of the visible light spectrum. Waveguide display equipment becomes redundant and complicated, which is particularly important.

Contents of the invention

In order to overcome the deficiencies of the prior art, the present invention aims to propose a single-layer full-color coupled waveguide display grating coupler. The coupler should have the performance of high-efficiency coupling of a single-layer waveguide grating in a wide visible spectrum range. For this reason, the technical solution adopted by the present invention is that the single-layer full-color coupled waveguide display grating coupler includes: the waveguide is a transparent substrate, and a grating layer with the same material or similar refractive index as the transparent substrate layer, and the grating layer has a high refractive index. High refractive index material film layer, and metal film layer on high refractive index material. The shape, period, groove depth, groove top angle, material of the grating layer, the thickness and the refractive index of the high refractive index layer, and the thickness and the value of the refractive index of the metal film layer make the grating The first-order diffraction efficiency is higher in the visible light spectrum range of 450nm-700nm, which is above 70%.

The grating coupler for waveguide display is a single-layer waveguide grating; the cross-sectional shape of the grating is an asymmetric inclined relief grating or a symmetrical relief grating structure, which can be specifically rectangular, sinusoidal, half-sine or trapezoidal; the grating The grating period is 300-500nm, the grating groove depth is greater than 30nm and less than 200nm, the groove top angle is greater than 15 degrees and less than 60 degrees, and the grating can be a linear one-dimensional grating or a two-dimensional grating.

The grating layer material is suitable for nano-printing or embossing, specifically polymethyl methacrylate PMMA, polystyrene PS (polystyrene), e-book exposure resist HSQ (hydrogen silsesquioxane).

The waveguide, that is, the transparent base material can specifically be polycarbonate, polyvinyl chloride, polyester, polymethyl methacrylate, silicon dioxide, fused silica or polymethyl methacrylate PMMA; the thickness of the transparent base is 500 microns to 3 mm .

The thickness of the high refractive index film layer is 5nm to 150nm; the material of the high refractive index film layer is magnesium oxide, aluminum oxide, titanium dioxide, hafnium oxide, zinc oxide, niobium oxide or tantalum pentoxide.

The thickness of the metal film layer is 40nm to 1 μm; the material of the metal film layer is titanium, aluminum, copper, gold, silver, lithium.

Features and beneficial effects of the present invention are:

(1) The single-layer full-color coupled waveguide display grating coupler of the present invention can achieve color coupling with only a single-layer waveguide grating compared with multi-layer multiplexing gratings, distributed exposure gratings, and multi-layer color waveguide gratings.

(2) Compared with the single-layer full-color coupled waveguide display grating coupler of the present invention, the color effect can be achieved by combining multiple colors with discrete wavelengths, the visible light spectrum range is wider, and the full-color color dynamic range is larger.

(3) The single-layer full-color coupled waveguide display grating coupler of the present invention is not limited to traditional holographic materials, and can be selected from safe and environmentally friendly materials, which are easy to store and can ensure accuracy.

(4) The single-layer full-color coupled waveguide display grating coupler of the present invention can be fabricated by nano-printing or embossing methods, which do not require special high-refractive index modulation holographic Materials, without precise control of conditions such as temperature, humidity, exposure time, and interference optical path accuracy, can produce higher-precision grating waveguides, and have good replicability, which is conducive to productization.

(5) Large viewing angle expansion, only when a large viewing angle display is required, only multiple layers of full-color waveguide display grating couplers need to be superimposed, so that each layer corresponds to a different viewing angle and finally realizes viewing angle expansion.

It should be understood that any product implementing the present invention does not necessarily need to achieve all the above-mentioned advantages at the same time. The above description and the following detailed description are only examples and explanations of the technical solutions of the present invention, and cannot limit the present invention.

Description of drawings:

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and together with the description serve to explain the principles of the invention.

Figure 1 is a schematic diagram of the structure of a single-layer full-color coupled waveguide display grating coupler.

Fig. 2 is a schematic cross-sectional structure diagram of a single-layer full-color coupled waveguide display grating coupler.

Fig. 3 shows the spectral response of the grating coupler for the single-layer full-color coupled waveguide of the present invention.

Fig. 4 shows the spectral response of the single-layer full-color coupled waveguide display grating coupler under different incident angles of the present invention.

Fig. 5 is a schematic diagram of one-dimensional exit pupil expansion in an embodiment of the present invention.

Detailed ways

The purpose of the present invention is to provide a single-layer full-color coupling waveguide display grating coupler, which should have the performance of high-efficiency coupling for a single-layer waveguide grating in a wide visible spectrum range.

In order to solve the above technical problems, the present invention is realized through the following technical solutions:

A single-layer full-color coupled waveguide display grating coupler, a single-layer full-color coupled waveguide display grating coupler, a display waveguide grating coupler applied to the visible light band, including: the waveguide is a transparent substrate, and the same material as the transparent substrate layer Or a grating layer with a similar refractive index. The grating layer has a high-refractive-index material film layer and a metal film layer on the high-refractive-index material. The shape, period, groove depth, groove top angle, material of the grating layer, the thickness and the refractive index of the high refractive index layer, and the thickness and the value of the refractive index of the metal film layer make the grating The first-order diffraction efficiency is high in the visible light spectrum range of 450nm-700nm.

In the above technical solution, the grating coupler for waveguide display is only a single-layer waveguide grating.

In the above technical solution, the single-layer full-color coupled waveguide display grating coupler is characterized in that, optionally, the profile of the grating section is an asymmetrical oblique relief grating or a symmetrical relief grating structure, specifically rectangular, sinusoidal , half-sine, trapezoidal.

The grating period of the grating is 300-500nm, the grating groove depth is greater than 30nm and less than 200nm, the groove top angle is greater than 15 degrees and less than 60 degrees, and the grating can be a linear one-dimensional grating or a two-dimensional grating.

Optionally, the grating layer material is a material suitable for nano-printing or imprinting, which has thermosetting or thermoplastic properties, better etching resistance, less shrinkage, lower viscoplasticity, high resolution, and fast curing Specifically, it can be polymethyl methacrylate PMMA, polystyrene PS (polystyrene), e-book exposure resist HSQ (hydrogensilsesquioxane).

Optionally, the waveguide, that is, the transparent base material is an optical material with high optical transmittance in the entire visible light band or in a specific wavelength range, specifically polycarbonate, polyvinyl chloride, polyester, polymethacrylic acid Methyl ester, silica, fused silica; transparent substrate thickness 500 microns to 3 mm.

In the above technical solution, the single-layer full-color coupled waveguide display grating coupler is characterized in that the thickness of the high refractive index film layer is 5nm to 150nm.

Optionally, the material of the high refractive index film layer is magnesium oxide, aluminum oxide, titanium dioxide, hafnium oxide, zinc oxide, niobium oxide or tantalum pentoxide.

In the above technical solution, the single-layer full-color coupled waveguide display grating coupler is characterized in that the thickness of the metal film layer is 40 nm to 1 μm.

Optionally, the material of the metal film layer is titanium, aluminum, copper, gold, silver, lithium.

The single-layer full-color coupled waveguide display grating coupler is characterized in that the first-order diffraction efficiency of the grating coupler is relatively high in the visible light spectrum range of 450nm-700nm.

Embodiments of the present invention are described in detail below, and the following description and drawings sufficiently illustrate specific embodiments of the present invention to enable those skilled in the art to practice them. The examples merely represent possible variations. Individual components and functions are optional unless explicitly required, and the order of operations may vary. Parts and features of some embodiments may be included in or replace parts and features of other embodiments. This embodiment is implemented on the premise of the technical solution of the present invention, and detailed implementation methods and specific operation processes are given. However, this embodiment The scope of protection of the invention is not limited to the following examples, and the scope of embodiments of the present invention includes the full scope of the claims and all available equivalents of the claims. Herein, various embodiments may be referred to individually or collectively by the term "invention", which is for convenience only and if in fact more than one invention is disclosed, the scope of the application is not automatically limited to any single invention. Invention or inventive concept.

The embodiment of the present invention discloses a polarization-insensitive high-efficiency waveguide display grating coupler. The structural diagrams of the polarization-insensitive high-efficiency waveguide display grating coupler proposed by the present invention are shown in Figures 1 and 2, which include: A transparent substrate 105, a grating layer 106 of the same material or similar refractive index as the grating base layer, a high refractive index material film layer 107 on the grating layer, and a metal film layer 108 on the high refractive index material. And the incident light 101, the 0th order diffracted light 102, the positive first order diffracted light 103, the negative first order diffracted light 104, the energy is concentrated in the positive first order 103, the shape, period Λ, groove depth h, groove top of the grating Angle, material, the thickness and refractive index of the high refractive index layer, and the thickness and refractive index of the metal film layer make the average diffraction efficiency of the grating reach 76% in the range of 450nm-750nm visible light, normal incidence Under certain conditions, the spectral response has a large bandwidth, and the full-color coupling effect of the monolithic grating waveguide structure is realized, making the waveguide display system thinner and more compact.

In the above technical solution, the grating coupler for waveguide display is only a single-layer waveguide grating.

In the above technical solution, the single-layer full-color coupled waveguide display grating coupler is characterized in that, optionally, the cross-sectional shape of the grating is an embossed grating structure, specifically isosceles triangle, rectangle, or zigzag.

The grating period of the grating is 300-500nm, the grating groove depth is greater than 30nm and less than 200nm, the groove top angle is greater than 15 degrees and less than 60 degrees, and the grating can be a linear one-dimensional grating or a two-dimensional grating.

Optionally, the grating layer material is a material suitable for nano-printing or imprinting, which has thermosetting or thermoplastic properties, better etching resistance, less shrinkage, lower viscoplasticity, high resolution, and fast curing Specifically, it can be polymethyl methacrylate PMMA, polystyrene PS (polystyrene), e-book exposure resist HSQ (hydrogensilsesquioxane).

Optionally, the waveguide, that is, the transparent base material is an optical material with high optical transmittance in the entire visible light band or in a specific wavelength range, specifically polycarbonate, polyvinyl chloride, polyester, polymethacrylic acid Methyl ester, silica, fused silica; transparent substrate thickness 500 microns to 3 mm.

In the above technical solution, the single-layer full-color coupled waveguide display grating coupler is characterized in that the thickness of the high refractive index film layer is 5nm to 150nm.

Optionally, the material of the high refractive index film layer is magnesium oxide, aluminum oxide, titanium dioxide, hafnium oxide, zinc oxide, niobium oxide or tantalum pentoxide.

In the above technical solution, the single-layer full-color coupled waveguide display grating coupler is characterized in that the thickness of the metal film layer is 40 nm to 1 μm.

Optionally, the material of the metal film layer is titanium, silver, lithium.

The above are only examples, and those skilled in the art can also combine more optional implementations without making creative efforts.

The single-layer full-color coupled waveguide display grating coupler is characterized in that the first-order diffraction efficiency of the grating coupler is relatively high in the visible light spectrum range of 450nm-700nm.

Figure 3 shows the single-layer full-color coupled waveguide display grating coupler of the present invention, under the incident condition of TE mode light, the spectral response range, it can be seen that it has a very large bandwidth in the visible light range.

Fig. 4 has shown the waveguide display grating coupler of single-layer full-color coupling of the present invention, under the condition of different incident angles, spectral response curve, envelope curve has higher diffraction efficiency in the range of 450-450nm visible light as a whole, average diffraction The efficiency reaches 76%.

The single-layer full-color coupled waveguide display grating coupler of the present invention can have the following application modes:

The single-layer full-color coupled waveguide display grating coupler of the present invention can be used as an input coupler for light beams to be coupled into the waveguide in a one-dimensional exit pupil expansion waveguide display device, as shown in Figure 5, and can be applied to optical devices with augmented reality functions Transmissive waveguide displays. The function of full-color coupling into the waveguide is realized by using a monolithic waveguide grating structure.

The above description is only a preferred example of the present invention, and does not limit the patent scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present invention shall be made by using the contents of the present invention and The equivalent structures or process changes made in the accompanying drawings to achieve equivalent effects, or directly or indirectly used in other related technical fields, are all included in the scope of patent protection of the present invention.

Claims (6)

1. A single-layer full-color coupled waveguide display grating coupler is characterized in that it includes: the waveguide is a transparent substrate, the same material as the transparent substrate layer or a grating layer with a similar refractive index, and a high-refractive index material film is arranged on the grating layer layer, and a metal film layer on a high refractive index material. The shape, period, groove depth, groove top angle, material of the grating layer, the thickness and the refractive index of the high refractive index layer, and the thickness and the value of the refractive index of the metal film layer make the grating The first-order diffraction efficiency is higher in the visible light spectrum range of 450nm-700nm, which is above 70%. 2. The single-layer full-color coupled waveguide display grating coupler as claimed in claim 1, wherein the waveguide display grating coupler is a single-layer waveguide grating; the profile of the grating is asymmetric Slanted relief grating or symmetrical relief grating structure, specifically rectangular, sinusoidal, half-sine or trapezoidal; the grating period of the grating is 300-500nm, the grating groove depth is greater than 30nm and less than 200nm, and the groove top angle is greater than 15 degrees and less than 60 degrees, the grating can be linear one-dimensional grating or two-dimensional grating. 3. The waveguide display grating coupler with single-layer full-color coupling as claimed in claim 1, wherein the material of the grating layer is a material suitable for nano-printing or embossing, specifically polymethyl methacrylate PMMA, polystyrene PS (polystyrene), e-book exposure resist HSQ (hydrogen silsesquioxane). 4. The single-layer full-color coupled waveguide display grating coupler as claimed in claim 1, wherein the waveguide is a transparent substrate material specifically polycarbonate, polyvinyl chloride, polyester, polymethacrylate ester, silica, fused silica, or polymethyl methacrylate PMMA; transparent substrate thickness 500 microns to 3 mm. 5. The waveguide display grating coupler with single-layer full-color coupling as claimed in claim 1, characterized in that, the thickness of the high refractive index film layer is 5nm to 150nm; the material of the high refractive index film layer is magnesium oxide , aluminum oxide, titanium dioxide, hafnium oxide, zinc oxide, niobium oxide, or tantalum pentoxide. 6. The single-layer full-color coupled waveguide display grating coupler as claimed in claim 1, wherein the thickness of the metal film layer is 40nm to 1 μm; the material of the metal film layer is titanium, aluminum, copper, gold, silver ,lithium.