Abstract
The reflection-asymmetric metal grating polarization beam splitter comprises a substrate, and a first grating composed of first mediums and first metals, and first light-absorbing materials are provided on the upper surfaces or side surfaces of the first metals. A plurality of second materials are provided at equal intervals longitudinally along the upper surfaces of the first metals to form a second grating. The first light-absorbing materials are closely provided on the upper surfaces of the first metals between two adjacent second materials, and second light-absorbing materials are closely provided on the upper surfaces and/or side surfaces of the second materials. The second materials have a greater thickness than the first light-absorbing materials. Second mediums are filled in spaces between adjacent second materials above the first light-absorbing materials.
Claims
1. A reflection-asymmetric metal grating polarization beam splitter, comprising a substrate (1), first mediums (2), and first metals (3), wherein a plurality of the first metals (3) and the first mediums (2) are provided transversely on an upper surface of the substrate (1) side by side at equal intervals to form a first grating, upper surfaces of the first metals (3) are provided with light-absorbing materials, the width of the first mediums (2) meets a mode cutoff of incident light with an electric field direction parallel to the first metal (3) grating lines, and a grating period of the first grating meets the requirement that a diffraction angle in the air at incident light waveband is greater than 90 degrees.
2. The beam splitter according to claim 1, wherein first light-absorbing material sidewalls (6) are closely provided on transverse sidewall surfaces of the first metals (3) and the light-absorbing materials.
3. The beam splitter according to claim 1, wherein the substrate (1) is a material transparent to incident light, the first mediums (2) are air or a material transparent to incident light, the first metals (3) are Al, and the light-absorbing materials are metal tungsten or boron carbide.
4. The beam splitter according to claim 1, wherein a plurality of second materials (5. a) are provided at equal intervals longitudinally along the upper surfaces of the first metals (3) to form a second grating, the light-absorbing materials are closely provided on the upper surfaces of the first metals (3) between two adjacent second materials (5. a), second mediums (4. b) are filled in spaces between adjacent second materials (5. a) above the light-absorbing materials, the width of the second mediums (4. b) meets the mode cutoff of incident light that makes a magnetic field direction parallel to the first metals (3) line direction, and a grating period of the second grating meets the requirement that the diffraction angle in the air at incident light working waveband is greater than 90 degrees.
5. The beam splitter according to claim 1, wherein a plurality of second materials (5. a) are provided at equal intervals longitudinally along the upper surfaces of the first metals (3) to form a second grating, the light-absorbing materials comprise first light-absorbing materials (4. a) and second light-absorbing materials (5. b), the first light-absorbing materials (4. a) are closely provided on the upper surfaces and/or side surfaces of the first metals (3) between two adjacent second materials (5. a), the second light-absorbing materials (5. b) are closely provided on upper surfaces of the second materials (5. a) lines, second mediums (4. b) are filled in spaces between the adjacent second materials (5.a) above the first light-absorbing materials (4. a), the width of the second mediums (4. b) meets the mode cutoff of incident light that makes the magnetic field direction parallel to the first metal (3) line direction, and the grating period of the second grating meets the requirement that the diffraction angle in the air at incident light working waveband is greater than 90 degrees.
6. The beam splitter according to claim 5, wherein on the same first metal (3) line, second light-absorbing material sidewalls (7) are closely provided on longitudinal sidewall surfaces of the second materials (5. a).
7. The beam splitter according to claim 4, wherein the substrate (1) is a material transparent to the working waveband, the first mediums (2) and the second mediums (4. b) are a material transparent to incident light, the first metals (3) are aluminum, the second materials (5. a) are aluminum, metal tungsten or silicon dioxide, and the light-absorbing materials are a material that exhibits metallicity at the working waveband.
8. The beam splitter according to claim 5, wherein the substrate (1) is a material transparent to incident light, the first mediums (2) and the second mediums (4. b) are air or a material transparent to incident light, the first metals (3) are aluminum, the second materials (5. a) are aluminum, metal tungsten or silicon dioxide, and the first light-absorbing materials (4. a) and the second light-absorbing materials (5. b) are tungsten, gallium arsenide, boron carbide or composite materials thereof.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0040] FIG. 1 is a schematic diagram of a geometric structure of a reflection-asymmetric metal grating polarization beam splitter of the invention.
[0041] FIG. 2 is a schematic diagram of a first embodiment of a metal grating polarization beam splitter.
[0042] FIG. 3 shows spectrum charts of reflection, transmission, and transmission polarization ratio of a one-dimensional aluminum-tungsten grating obtained by the simulation when light is incident from a grating surface in the first embodiment.
[0043] FIG. 4 shows spectrum charts of reflection, transmission, and transmission polarization ratio of the one-dimensional aluminum-tungsten grating obtained by the simulation when light is incident from a substrate surface in the first embodiment.
[0044] FIG. 5 is a schematic diagram of a second embodiment of the metal grating polarization beam splitter.
[0045] FIG. 6 shows spectrum charts of reflection, transmission, and transmission polarization ratio of a one-dimensional aluminum-tungsten grating with sidewalls obtained by the simulation when light is incident from the grating surface in the second embodiment.
[0046] FIG. 7 is a schematic diagram of a third embodiment of the metal grating polarization beam splitter.
[0047] FIG. 8 shows spectrum charts of reflection, transmission, and transmission polarization ratio of a one-dimensional aluminum-boron carbide grating obtained by the simulation when light is incident from the grating surface in the third embodiment.
[0048] FIG. 9 is a schematic diagram of a fourth embodiment of the metal grating polarization beam splitter.
[0049] FIG. 10 shows spectrum charts of reflection, transmission, and transmission polarization ratio of a composite grating where a second grating is an aluminum-tungsten composite structure, obtained by the simulation through a finite element software in the fourth embodiment.
[0050] FIG. 11 is a schematic diagram of a fifth embodiment of the metal grating polarization beam splitter.
[0051] FIG. 12 shows spectrum charts of reflection, transmission, and transmission polarization ratio of a composite grating where a second grating is a tungsten grating, obtained by the simulation when light is incident from the grating surface in the fifth embodiment.
[0052] FIG. 13 is a schematic diagram of a sixth embodiment of the metal grating polarization beam splitter.
[0053] FIG. 14 shows spectrum charts of reflection, transmission, and transmission polarization ratio of a composite grating where a second grating is a medium-tungsten grating, obtained by the simulation when light is incident from the grating surface in the sixth embodiment.
[0054] FIG. 15 is a schematic diagram of a seventh embodiment of the metal grating polarization beam splitter.
[0055] FIG. 16 shows spectrum charts of reflection, transmission, and transmission polarization ratio of a composite grating where a second grating is an aluminum-tungsten grating, obtained by the simulation when light is incident from the grating surface in the seventh embodiment.
[0056] FIG. 17 is a schematic diagram of an eighth embodiment of the metal grating polarization beam splitter.
[0057] FIG. 18 shows spectrum charts of reflection, transmission, and transmission polarization ratio of a composite grating where a second grating is a medium-tungsten grating with sidewalls, obtained by the simulation when light is incident from the grating surface in the eighth embodiment.
[0058] In the accompanying drawings:
[0059] 1: substrate; 2: first medium; 3: first metal; 4. a: first light-absorbing material; 4. b: second medium; 5. a: second material; 5. b second light-absorbing material; 6: first light-absorbing material sidewall; 7: second light-absorbing material sidewall; 8: incident TE light; 9: weak TE reflected light; 10: weak TE transmission light; 11: incident TM light; 12: weak TM reflected light; 13: strong TM transmission light.
DETAILED DESCRIPTION OF THE INVENTION
[0060] For the purposes, technical solutions, and advantages of embodiments of the invention to be clearer, the technical solutions in the embodiments of the invention will be clearly and completely described below in combination with the accompanying drawings in the embodiments of the invention. It is obvious that the described embodiments are some of the embodiments of the invention but not all of them. All other embodiments obtained by those skilled in the art without creative work done, based on the embodiments of the invention, fall within the protection scope of the invention.
[0061] Referring to FIG. 1, FIG. 1 is a schematic diagram of a geometric structure of a reflection-asymmetric metal grating polarization beam splitter of the application, wherein the beam splitter includes a substrate 1, first mediums 2, first metals 3, first light-absorbing materials 4. a, second mediums 4. b, second materials 5. a, second light-absorbing materials 5. b, incident TE light 8, weak TE reflected light 9, weak TE transmission light 10, incident TM light 11, weak TM reflected light 12, and strong TM transmission light 13.
Embodiment 1
[0062] A one-dimensional aluminum-tungsten grating is shown. The reflection of TE light is suppressed when light is incident from a grating surface, and TE light is highly reflected when light is incident from a substrate surface, with the same high transmission polarization suppression ratio occurring for both conditions.
[0063] FIGS. 2 to 4 respectively show a schematic structure diagram of a one-dimensional aluminum-tungsten grating, and spectrum charts of reflection, transmission, and absorption in the visible light range obtained through the commercial software COMSOL, as well as simulation results of the transmission polarization ratio. The lower layer of the polarization beam splitter is a first grating composed of the first metal aluminum and the first mediums (which are a material transparent to incident light or a working wavelength, such as air, PMMA (polymethyl methacrylate), SiO.sub.2 (silicon dioxide), PC (polycarbonate), quartz, or PET (polyester resin)). The direction of the grating period is along the x-axis, and aluminum lines extend along the y-axis direction. The period P1 is 100 nm (nanometers). The metal aluminum lines each have a length of half the period (that is, w1=50 nm), and a thickness h1 of 100 nm. The first materials on the aluminum lines are tungsten with a thickness h2 of 45 nm.
[0064] Referring to FIG. 3, spectrum charts of a one-dimensional aluminum grating are represented by thin lines, and those of a one-dimensional aluminum-tungsten grating are represented by thick lines. When light is incident from the grating surface, the simulation results show that the one-dimensional aluminum grating without tungsten has a TE light reflectance of as high as 90% and a TM light transmittance of about 80%. For the one-dimensional aluminum-tungsten grating with metal tungsten, the reflection efficiency of TE light is greatly decreased to about 35%, the transmission efficiency of TM light is only decreased to about 73%, the transmission efficiency of TE light is decreased by more than one order of magnitude, and the transmission polarization ratio is increased to 10,000 to 19,000. It can be seen that compared with the one-dimensional aluminum grating, the one-dimensional aluminum-tungsten grating increases the transmission polarization ratio by 4 to 21 times, suppresses about 60% of TE reflected light, and also decreases the reflection efficiency of TM light by about a half.
[0065] Referring to FIG. 4, for the one-dimensional aluminum-tungsten grating, when the incident light is incident from the substrate surface, the transmission efficiencies do not change, the reflection efficiency of TM light increases, and the reflection efficiency of TE light reaches about 90%.
Embodiment 2
[0066] Referring to FIGS. 5 and 6, based on Embodiment 1, the thickness of the aluminum lines is increased to 150 nm, and at the same time, the aluminum lines each have first light-absorbing material sidewalls 6 with a thickness of 5 nm on their edges, with the first light-absorbing material sidewalls 6 made of metal tungsten.
[0067] FIG. 5 shows a schematic structure diagram of a composite grating, whose structure parameters are the same as those of the one-dimensional aluminum-tungsten grating in Embodiment 1, except that the thickness of the aluminum layer grating is increased to 150 nm and the aluminum lines each have 5 nm tungsten sidewalls.
[0068] FIG. 6 shows the results of a simulation embodiment through the commercial software COMSOL, where light is incident from the grating surface. The simulation results show that the increase in the thickness of the aluminum layers has little effect on the reflection and transmission efficiencies of TM polarized light and the reflection efficiency of TE light, but greatly decreases the transmission efficiency of TE light, thereby increasing the transmission polarization ratio by ˜41 times. Thin sidewalls have little effect on the results.
Embodiment 3
[0069] Referring to FIGS. 7 and 8, for a one-dimensional aluminum-boron carbide grating, when light is incident from the grating surface, the reflection of TE light is suppressed, with a high transmission polarization suppression ratio.
[0070] FIG. 7 shows a schematic structure diagram of a one-dimensional aluminum-boron carbide grating. The lower layer of the polarization beam splitter is the first grating composed of the first metal aluminum and the first mediums (which are air, PMMA, or SiO.sub.2). The direction of the grating period is along the x-axis, the aluminum lines extend along the y-axis direction, and the period P1 is 100 nm. The metal aluminum lines each have a width of half the period (that is, w1=50 nm), and a thickness h1 of 120 nm. The first materials on the aluminum lines are boron carbide, with a thickness h2 of 60 nm.
[0071] FIG. 8 shows spectrum charts of reflection, transmission, and absorption in the visible light range obtained through the commercial software COMSOL, as well as simulation results of the transmission polarization ratio. Light is incident from the grating surface, and the simulation results show that the reflection efficiency of TE light is from 5% to 35%, the transmission efficiency of TM light is from 50% to 82%, and the transmission polarization suppression ratio is from 8,500 to 16,200.
Embodiment 4
[0072] Referring to FIGS. 9 and 10, a second grating is an aluminum-tungsten composite structure, light is incident from the grating surface, and a high transmission polarization ratio is obtained while the TE reflection is decreased to less than 20%.
[0073] FIG. 9 shows a schematic structure diagram of a composite grating. The first grating composed of the first metal aluminum and the first mediums (which are air, PMMA, PC, PET, or SiO.sub.2) has a period P1 of 100 nm, and the aluminum lines each have a width w1 of 50 nm. The second grating composed of the second material aluminum on the upper layer and the second mediums (which are air, PMMA (polymethyl methacrylate), SiO.sub.2 (silicon dioxide), PC (polycarbonate), or PET (polyester resin)) has a period P2 of 200 nm. In each period, a second material aluminum line has a length w2 of 140 nm and a thickness h2 of 100 nm, a first light-absorbing material tungsten line at the bottom of the second medium has a length of 60 nm and a thickness h3 of 30 nm, and their widths both are the same as that of the aluminum line on the lower layer, of 50 nm.
[0074] Referring to FIG. 10, the simulation results show that TM light with a wavelength of above 540 nm has a transmittance of about 80%, and TM light with a short wavelength has a slightly lower transmittance of about 62%. TE light with a wavelength of from 420 nm to 700 nm has a reflection efficiency decreased to below 20%. There is a very high transmission polarization ratio of 17,000 to 33,000.
Embodiment 5
[0075] Referring to FIGS. 11 and 12, the second grating is a one-dimensional tungsten grating, and a low TE reflection and a high transmission polarization suppression ratio are obtained.
[0076] FIG. 11 shows a schematic structure diagram of a one-dimensional tungsten grating being superimposed onto a one-dimensional aluminum grating. The first grating composed of the first metal aluminum and the first medium (which is air, PMMA, or SiO.sub.2) has a period P1 of 100 nm, and the aluminum lines each have a width w1 of 50 nm. The second grating composed of the second material tungsten on the upper layer and the second medium (which is air, PMMA, PC, PET, or SiO.sub.2) has a period P2 of 200 nm. In each period, a second material tungsten line has a length w2 of 140 nm and a thickness h2 of 120 nm, a first light-absorbing material tungsten line at the bottom of the second medium (air) has a length of 60 nm and a thickness h3 of 45 nm, and their widths both are the same as that of the aluminum line on the lower layer, of 50 nm.
[0077] FIG. 12 shows spectrum charts of reflection, transmission, and absorption in the visible light range obtained through the commercial software COMSOL, as well as simulation results of the transmission polarization ratio. Light is incident from the grating surface, and the simulation results show that TE light and TM light both have a reflection efficiency of below 10%, and the transmission polarization ratio is as high as 22,000 to 50,000.
Embodiment 6
[0078] Referring to FIGS. 13 and 14, the second grating is a medium-tungsten composite structure, and a low TE reflection and a high transmission polarization suppression ratio are obtained.
[0079] FIG. 13 shows a schematic structure diagram of a composite grating. The first grating composed of the first metal aluminum and the first mediums (which are air, PMMA (polymethyl methacrylate), SiO.sub.2 (silicon dioxide), PC (polycarbonate), quartz, or PET (polyester resin)) has a period P1 of 100 nm, the grating direction is along the x-axis, and the aluminum lines each extend along the y-axis direction and have a width w1 of 50 nm. The second grating composed of the second material silicon dioxide on the upper layer and the second mediums (which are air, PMMA, PET, PC, quartz or SiO.sub.2) has a period P2 of 250 nm. In each period, a second material silicon dioxide line has a length w2 of 75 nm and a thickness h2 of 140 nm, a second light-absorbing material tungsten on the top of the second material silicon dioxide has a thickness h4 of 80 nm, a first light-absorbing material tungsten line at the bottom of the second medium (air) has a length of 175 nm and a thickness h3 of 80 nm, and their widths all are the same as that of the aluminum line on the lower layer, of 50 nm.
[0080] FIG. 14 shows spectrum charts of reflection, transmission, and absorption in the visible light range obtained through the commercial software COMSOL, as well as simulation results of the transmission polarization ratio. Light is incident from the grating surface, and the simulation results show that TE light with a wavelength of greater than 500 nm has a reflection efficiency of less than 4%, TM light with a wavelength of greater than 500 nm has a reflection efficiency of less than 2%, and the transmission polarization ratio is from 20,000 to 35,000.
Embodiment 7
[0081] Referring to FIGS. 15 and 16, the second grating is an aluminum-tungsten composite structure, and a low TE reflection and a high transmission polarization suppression ratio are obtained.
[0082] FIG. 15 shows a schematic structure diagram of a composite grating. The first grating composed of the first metal aluminum and the first medium (which is air, PMMA (polymethyl methacrylate), SiO.sub.2 (silicon dioxide), PC (polycarbonate), quartz, or PET (polyester resin)) has a period P1 of 100 nm, the grating direction is along the x-axis, and the aluminum lines extend along the y-axis direction and have a width w1 of 50 nm. The second grating composed of the second material aluminum on the upper layer and the second medium (which is air, PMMA (polymethyl methacrylate), SiO.sub.2 (silicon dioxide), PC (polycarbonate), quartz, or PET (polyester resin)) has a period P2 of 200 nm. In each period, a second material aluminum line has a length w2 of 140 nm and a thickness h2 of 100 nm, a second light-absorbing material on the top of the second material aluminum has a thickness h4 of 45 nm, a first light-absorbing material line at the bottom of the second medium (air) has a length of 60 nm and a thickness h3 of 45 nm, and their widths all are the same as that of the aluminum line on the lower layer, of 50 nm.
[0083] FIG. 16 shows spectrum charts of reflection, transmission, and absorption in the visible light range obtained through the commercial software COMSOL, as well as simulation results of the transmission polarization ratio. Light is incident from the grating surface. The simulation results show that TM light has a high transmittance of 55% to 75%, TE light with a wavelength of 500 nm to 800 nm has a reflection efficiency reduced to below 10%, TE light with a short wavelength has also a reflection efficiency of below 20%, and the transmission polarization ratio is as high as 50,000-200,000. The shorter the wavelength, the higher the transmission polarization ratio.
Embodiment 8
[0084] Referring to FIGS. 17 and 18, based on Embodiment 6, second light-absorbing material sidewalls 7 with a thickness of 10 nm are attached to the aluminum line edges of the second grating. The second light-absorbing material sidewalls 7 are made of metal tungsten. Light is incident from the grating surface, and a low TE reflection and a high transmission polarization suppression ratio are obtained.
[0085] FIG. 17 shows a schematic structure diagram of a composite grating, in which tungsten layers with a width of 10 nm are superimposed onto the sides of the second material aluminum, based on Embodiment 6.
[0086] FIG. 18 shows spectrum charts of reflection, transmission, and absorption in the visible light range obtained through the commercial software COMSOL, as well as simulation results of the transmission polarization ratio. The simulation results show that TM light has a transmittance maintained at 55% to 75%, TE light with a wavelength of 500 nm to 800 nm has a reflection efficiency of below 10%, TE light with a short wavelength has a reflection efficiency of below 20%, and the transmission polarization ratio is as high as 55,000 to 380,000. The shorter the wavelength, the higher the transmission polarization ratio.
[0087] Finally, it should be explained that the above embodiments are only used to illustrate the technical solutions of the invention instead of limiting them. Although the invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that it is still possible to modify the technical solutions recorded in the aforementioned embodiments or equivalently replace some of the technical features, and these modifications or replacements do not separate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the invention.
