Optical modulator

Abstract

The application discloses an optical modulator. The optical modulator comprises a substrate, a conductive oxide layer, a dielectric layer and a metal layer. The substrate has a first surface and a second surface arranged oppositely, the first surface is provided with at least one groove, the groove wall of the groove comprises two wall surfaces arranged oppositely along a specified direction, and an included angle of 85-95 degrees is formed between the two wall surfaces. The metal layer at least continuously covers the groove wall of the groove. The conductive oxide layer and the dielectric layer are arranged between the substrate and the metal layer and are used for forming an electrical connection between the substrate and the metal layer. When the modulated light is incident from the second surface of the substrate, and a specified bias is applied between the substrate and the metal layer, the absorption of the optical modulator to the specified wavelength light can be regulated, and the modulation of the optical signal is realized. The optical modulator provided by the application improves the modulation efficiency of the optical modulator.

Description

Technical Field

[0001] This invention relates to an optical modulator, and more particularly to a spatial optical modulator, belonging to the field of optoelectronic device technology. Background Technology

[0002] Optical modulators are devices that use electrical, thermal, or mechanical driving methods to modify optical signals, and they have important applications in optical information processing, optical communication, imaging, and display. Based on the transmission method of the optical signal, optical modulators can be divided into optical waveguide modulators and spatial optical modulators. The former modulates light in a waveguide, while the latter modulates light transmitted in space. Currently, the main technologies for realizing spatial optical modulators include electroabsorption modulation, electro-optic modulation, liquid crystals, and MEMS. Among these, the low-speed operation of liquid crystal and MEMS modulation cannot meet the needs of high-speed modulation applications; electroabsorption modulation is generally based on gallium arsenide quantum well materials, which is costly, and the overall structure often requires dozens of layers of heterogeneous material epitaxy, resulting in complex processes. Furthermore, the uniformity of multilayer materials limits the array size and modulation depth; electro-optic modulation is generally based on nonlinear crystal materials or polymers, resulting in large device size and high driving voltage.

[0003] A 2010 issue of *Nano Letters*, Volume 10, page 2111, reported the formation of a planar capacitor structure on an indium tin oxide (ITO) thin film. Under bias, the electron concentration distribution at the interface between ITO and the dielectric layer could be adjusted, resulting in a refractive index change of up to 1 at the interface layer, potentially leading to effective optical modulation. A 2012 issue of *Nanophotonics*, Volume 1, page 17, reported a waveguide modulator integrating an ITO planar capacitor structure onto a silicon waveguide, achieving a modulation efficiency of 1 dB / µm, far exceeding that of optical modulators based on traditional materials such as silicon and lithium niobate. However, spatial optical modulators have consistently faced the problem of low modulation efficiency due to insufficient interaction intensity between the modulated light and the material. A 2013 article in *Applied Physics Letters*, Volume 102, number 221102, reported a spatial optical modulator integrating ITO onto the surface of a metal nanograting, observing a modulation depth of less than 1%. A spatial light modulator integrating indium tin oxide into a metal nanograting and metal mirror sandwich structure was reported in Nano Letters, Volume 16, page 5319, 2016, achieving a modulation depth of 20-30%. Optics Letters, page 39-4978, 2014, reported a high localized field mode excitation of an indium tin oxide planar capacitor structure using prism coupling, achieving a modulation depth of 20%.

[0004] However, existing technologies such as those mentioned above all suffer from the problem of needing to prepare costly and low-yield nanostructures or additional prism coupling methods to achieve optical modulation, which limits large-scale applications and the realization of highly integrated microsystems. Summary of the Invention

[0005] The main objective of this invention is to provide an optical modulator that overcomes the shortcomings of the prior art.

[0006] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0007] This invention provides an optical modulator, comprising a substrate, a conductive oxide layer, a dielectric layer, and a metal layer;

[0008] The substrate has a first surface and a second surface arranged opposite to each other. The first surface of the substrate is provided with at least one groove. The groove wall includes two wall surfaces arranged opposite to each other along a set direction, and the two wall surfaces form an included angle of 85-95°.

[0009] The metal layer at least continuously covers the wall of the trench; the conductive oxide layer and the dielectric layer are stacked between the substrate and the metal layer and are used to form an electrical connection between the substrate and the metal layer; when the modulated light is incident from the second surface of the substrate and a specified bias voltage is applied between the substrate and the metal layer, the absorption of the specified wavelength light by the optical modulator can be controlled, thereby realizing the modulation of the optical signal.

[0010] In one specific embodiment, the tank wall includes two first wall surfaces arranged opposite each other along a first direction and two second wall surfaces arranged opposite each other along a second direction. The first wall surfaces and the second wall surfaces are both inclined, and an angle of 85-95° is formed between the two first wall surfaces and between the two second wall surfaces. The first direction and the second direction are perpendicular to each other.

[0011] In one specific embodiment, the included angle formed between the two walls is 90°.

[0012] In one specific embodiment, the first surface of the substrate is provided with a plurality of grooves, and the plurality of grooves are arranged in parallel along a first direction or a second direction.

[0013] In one specific embodiment, the gap between two adjacent slots does not exceed 10% of the center distance between the two adjacent slots.

[0014] In one specific embodiment, the width of the groove opening in a set direction is 1-100 μm.

[0015] In one specific embodiment, the conductive oxide layer is disposed between the dielectric layer and the metal layer, or the dielectric layer is disposed between the conductive oxide layer and the metal layer.

[0016] In one specific embodiment, the conductive oxide layer is made of a metal oxide.

[0017] In one specific embodiment, the metal oxide includes any one or a combination of two or more of indium tin oxide, zinc oxide, aluminum-doped zinc oxide, gallium-doped zinc oxide, cadmium oxide, and indium-doped cadmium oxide, but is not limited thereto.

[0018] In one specific embodiment, the thickness of the conductive oxide layer is 5-50 nm.

[0019] In one specific embodiment, the material of the dielectric layer includes any one or a combination of two or more of silicon dioxide, silicon nitride, aluminum oxide, magnesium fluoride, hafnium oxide, and zinc selenide, but is not limited thereto.

[0020] In one specific embodiment, the thickness of the dielectric layer is 5-50 nm.

[0021] In one specific embodiment, the material of the metal layer includes any one or a combination of two or more of gold, silver, aluminum, copper, and titanium, but is not limited thereto.

[0022] In one specific embodiment, the thickness of the metal layer is greater than 50 nm.

[0023] In one specific embodiment, the thickness of the metal layer is 50-100 nm.

[0024] In one specific embodiment, the substrate includes a silicon substrate.

[0025] In one specific embodiment, the metal layer, the conductive oxide layer, and the dielectric layer are all continuously and conformally covered on the first surface of the substrate.

[0026] In one specific embodiment, the light-reflecting structure formed by the groove wall and the metal layer can reflect incident light from any angle incident on the second surface of the substrate onto the light modulator along the original path.

[0027] In one specific embodiment, the second surface of the substrate is further covered with an anti-reflective film, which is used to reduce the reflected light from the second surface and ensure that the light ultimately reflected back is modulated by the electrical absorption of the conductive oxide. The anti-reflective film can be of a type known to those skilled in the art, and its thickness and other parameters can be selected according to specific circumstances, without being specifically limited here.

[0028] This invention also provides an optical signal modulation method, comprising:

[0029] Provide the aforementioned optical modulator;

[0030] The modulated light is incident on the optical modulator from the second surface of the substrate, and a specified bias voltage is applied between the substrate and the metal layer, thereby controlling the absorption of light of a specified wavelength by the optical modulator, and thus realizing the modulation of the optical signal.

[0031] Compared with the prior art, the advantages of the present invention include:

[0032] 1) An optical tuner provided in this embodiment of the invention achieves strong localization of incident light in the layer structure of a conductive oxide parallel plate capacitor by setting a micron-scale V-groove structure on a silicon substrate, thereby avoiding the dependence of the prior art on nanostructures or coupling prisms, reducing the manufacturing cost of the optical tuner, and facilitating the large-scale and miniaturized manufacturing of the optical tuner.

[0033] 2) An optical tuner provided in this embodiment of the invention has a micron-scale V-shaped groove structure with a 90-degree angle on a silicon substrate, and a metal film is coated on the surface of the V-shaped groove structure, so that incident light at all angles can be reflected in the original path, thereby simplifying the optical path of the system, and the double reflection helps to increase the modulation depth. Attached Figure Description

[0034] To better illustrate the content of this invention, the embodiments are briefly described below with reference to the accompanying drawings. The drawings are schematic diagrams of idealized embodiments of the invention. For clarity, the proportions of layers and regions have been enlarged, but as schematic diagrams, they should not be considered to strictly reflect the proportional relationships of geometric dimensions. The embodiments shown in the invention should not be considered limited to the specific shapes of the regions shown in the figures. The representations in the figures are illustrative and should not be considered to limit the scope of the invention; wherein:

[0035] Figure 1 This is a side view of an optical modulator structure provided in a typical embodiment of the present invention;

[0036] Figure 2a This is a top view schematic diagram of a one-dimensionally arranged V-groove structure in an optical modulator provided in a typical embodiment of the present invention;

[0037] Figure 2b These are top views of a two-dimensional V-groove structure in an optical modulator provided in a typical embodiment of the present invention.

[0038] Figure 3 This is a typical embodiment of the present invention, which provides the relationship between the dielectric constant of indium tin oxide material used in an optical modulator and wavelength at different electron concentrations;

[0039] Figure 4aThis invention provides a typical embodiment of an indium tin oxide parallel plate capacitor for an optical modulator, showing the reflection spectrum of incident light with different polarizations when the electron accumulation region has different electron concentrations.

[0040] Figure 4b This is a typical embodiment of the present invention, which provides the modulation result of a V-groove optical modulator on P-polarized light by adjusting the electron concentration of the electron accumulation layer;

[0041] Figure 4c This is a side view of the electric field distribution in a V-groove optical modulator provided in a typical embodiment of the present invention. Detailed Implementation

[0042] In view of the shortcomings of the prior art, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention. The following will further explain and illustrate this technical solution, its implementation process, and its principles.

[0043] An optical modulator provided by an embodiment of the present invention includes at least a silicon substrate and a trench on the upper surface of the silicon substrate, and at least a conductive oxide layer, a dielectric layer, and a metal layer that conformally cover the trench wall surface at least continuously. The conductive oxide layer and the dielectric layer are stacked between the silicon substrate and the metal layer, forming an electrical connection between them. The relative positions of the upper and lower layers of the conductive oxide layer and the dielectric layer can be interchanged. The silicon substrate, the conductive oxide layer, the dielectric layer, and the metal layer together form a layer structure of a parallel-plate capacitor. Applying a bias voltage between the silicon substrate and the metal layer can lead to electron accumulation between the conductive oxide layer and the dielectric layer through a capacitor charging effect.

[0044] When a bias voltage is applied between the silicon substrate and the metal layer, an electron accumulation region is formed on the side of the conductive oxide layer near the dielectric layer. The electron accumulation concentration is different under different bias voltages. The dielectric constant of the electron accumulation region in the conductive oxide layer is related to the concentration of electron accumulation. By adjusting the bias voltage and making the real part of the dielectric constant of the electron accumulation region close to zero at a specified wavelength, the incident light at this wavelength can be strongly localized to the electron accumulation region and strongly absorbed.

[0045] Therefore, when the modulated light is incident from the lower surface of the silicon substrate, it undergoes two reflections on the sidewall of the groove, that is, it interacts with the above-mentioned parallel plate capacitor structure twice. Under an appropriate bias voltage, the light of the specified wavelength is absorbed by the conductive oxide layer in the parallel plate capacitor structure, thereby realizing the intensity modulation of the optical signal.

[0046] This invention provides an optical tuner that employs a micron-scale V-groove structure on the surface of a silicon substrate opposite to the light incident surface to achieve strong localization of incident light in a conductive oxide parallel plate capacitor layer structure. This avoids the reliance on nanostructures or coupling prisms in existing technologies, promoting low-cost, large-scale applications and miniaturization. The use of a V-groove structure (preferably a 90° angle groove) and the application of a metal film on the surface of the V-groove structure enable full-angle incident light to be reflected along the original path, simplifying the optical path of the system. Furthermore, the double reflection helps to increase the modulation depth.

[0047] The following will further explain the technical solution, its implementation process and principle in conjunction with the accompanying drawings. Unless otherwise specified, the silicon substrate, conductive oxide layer, dielectric layer, metal layer and other components constituting the optical modulator provided in the embodiments of the present invention can all be those known to those skilled in the art.

[0048] In a more specific implementation plan, please refer to Figure 1 An optical modulator, comprising:

[0049] A silicon substrate 101, wherein a plurality of V-grooves 102 are provided on its upper surface (i.e., the aforementioned first surface, hereinafter the same), the gap between two adjacent V-grooves is g, and the center distance between two adjacent V-grooves is P; and,

[0050] A conductive oxide layer 103, a dielectric layer 104, and a metal layer 105 are sequentially deposited on the surface of the V-groove 102. The conductive oxide layer 103 and the dielectric layer 104 are stacked between the silicon substrate 101 and the metal layer 105, forming an electrical connection between the silicon substrate 101 and the metal layer 105. It should be noted that the upper and lower layer positions of the conductive oxide layer 103 and the dielectric layer 104 between the silicon substrate 101 and the metal layer 105 can be interchanged (e.g., ...). Figure 1 ).

[0051] Please see Figure 1 and Figure 2a Multiple V-shaped grooves can be arranged in parallel along the same direction. The two sidewalls 102-a and 102-b of each V-shaped groove are arranged opposite each other, and the included angle between the two sidewalls 102-a and 102-b is θ, which is 85-95°, preferably 90°.

[0052] Please see Figure 2b Multiple V-grooves can be arranged in parallel along two vertical directions. The angle between the two sets of sidewalls 102-1 and 102-3, 102-2 and 102-4 of each V-groove is θ, preferably 90 degrees. However, errors may occur during the actual preparation process, causing deviations from this angle.

[0053] Please see Figure 3Indium tin oxide (ITO) is a typical conductive oxide material whose dielectric constant is related to the electron concentration and conforms to the Drude model.

[0054]

[0055]

[0056] Where, ε ∞ ω is the high-frequency dielectric constant. p Let Γ be the plasmon oscillation frequency, Γ be the damping constant of the material, and n0 be the electron concentration. From equation (1), we can see that the dielectric constant ε is related to ω. p It is related to ω, and it can be seen from equation (2) that ω p It is related to electron concentration; changing the electron concentration can adjust ω. p This changes the dielectric constant ε of the material.

[0057] Figure 3 This shows that when the electron concentration is 1*10 19 cm -3 1*10 20 cm -3 3*10 20 cm -3 5*10 20 cm -3 7*10 20 cm -3 The values ​​of the real and imaginary parts of the dielectric constant of indium tin oxide at different wavelengths; by Figure 3 As can be seen, the real part of the dielectric constant of indium tin oxide becomes 0 at different wavelengths under different electron concentrations; for example, when the electron concentration is 7*10 20 cm -3 At this point, the real part of the dielectric constant of indium tin oxide becomes 0 at 1500 nm; according to the continuity condition of the electric displacement vector at the interface, the perpendicular electric field component in the zero dielectric constant material will become infinite, that is, the strong localization of the electromagnetic field is realized, which can greatly improve the optical absorption, optical nonlinearity and other properties.

[0058] The technical solution of the present invention will now be described in detail with reference to several preferred embodiments and related drawings.

[0059] Example 1

[0060] Please see Figure 1An optical modulator has a layer structure on a silicon substrate 101 consisting of, from bottom to top, a V-groove 102, a dielectric layer 104, a conductive oxide layer 103, and a metal layer 105. Multiple V-grooves 102 are arranged parallel to each other in the same direction, with zero gap between adjacent V-grooves 102, a center-to-center distance of 10 μm between adjacent V-grooves 102, and an angle of 90° between each V-groove and its two sidewalls. The dielectric layer 104 is hafnium oxide with a thickness of 10 nm; the conductive oxide layer 103 is indium tin oxide with a thickness of 10 nm; and the metal layer 105 is a gold film with a thickness of 200 nm.

[0061] Specifically, when a bias voltage is applied between the metal layer 105 and the silicon substrate 101, an electron accumulation layer is formed between the indium tin oxide 103 and the hafnium oxide 104, and the thickness of the electron accumulation layer is about 1 nm.

[0062] Specifically, in a four-layer parallel-plate capacitor structure such as silicon-indium tin oxide-hafnium oxide-gold, when s-polarized and p-polarized light are incident at 45° angles respectively, the calculated reflection spectrum is as follows: Figure 4a As shown in Figure a, s-polarized light lacks an electric field component perpendicular to the layer structure interface, thus failing to excite a strongly localized electromagnetic field mode in the electron accumulation layer. Therefore, its reflection spectrum shows no significant difference under different electron concentrations in the electron accumulation layer. In contrast, p-polarized light exhibits a 1*10-1 difference under two different electron concentrations. 20 cm -3 (on), 6.5*10 20 cm -3 The reflectance spectrum showed a significant difference when (off), especially at 1520 nm, the reflectance dropped from 89% to 36%, achieving significant electrically driven light intensity modulation.

[0063] Specifically, considering that p-polarized light incident on the actual structure of the V-groove will undergo two reflections before returning in its original direction, the reflection spectrum of the electron accumulation layer under different bias voltages yields the following results: Figure 4b As shown in Figure 4, different degrees of light intensity modulation can be obtained at different wavelengths by adjusting the electron concentration, especially at 1520 nm where a relative modulation depth of 82% is achieved. Furthermore, selecting an appropriate bias voltage can yield excellent optical modulation performance over a wide spectral range; for example, when the electron concentration of the electron accumulation layer is 1*10... 20 cm -3 (on) and 5*10 20 cm -3 When the (off) interval is varied, a relative modulation depth of over 75% is also obtained at 1720nm; Figure 4c The electron concentration of the electron accumulation layer is shown to be 6.5*10. 20 cm -3A side view of the electric field distribution in the V-groove at a wavelength of 1520 nm, by Figure 4c It can be seen that the electric field component is strongly localized in the electron accumulation layer and thus efficiently absorbed, thereby achieving the excellent optical modulation performance mentioned above.

[0064] The optical tuner provided in this invention achieves strong localization of incident light in the layer structure of a conductive oxide parallel plate capacitor by setting a micron-scale V-groove structure on a silicon substrate. This avoids the dependence of existing technologies on nanostructures or coupling prisms, reduces the manufacturing cost of the optical tuner, and is beneficial for the large-scale and miniaturized manufacturing of the optical tuner.

[0065] The optical tuner provided in this embodiment of the invention features a micron-scale V-groove structure on a silicon substrate, with a metal film coated on the surface of the V-groove structure. This allows for the reflection of incident light at all angles along its original path, thereby simplifying the system's optical path. Furthermore, the double reflection helps increase the modulation depth. Additionally, the optical tuner provided in this embodiment of the invention employs a conductive oxide parallel plate capacitor to achieve optical modulation, improving the modulation efficiency of the optical modulator (significantly higher than that of materials such as silicon and lithium niobate).

[0066] It should be understood that the above embodiments are merely illustrative of the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. An optical modulator, characterized in that, Includes substrate, conductive oxide layer, dielectric layer, and metal layer; The substrate has a first surface and a second surface arranged opposite to each other. The first surface of the substrate is provided with at least one groove. The groove wall includes two wall surfaces arranged opposite to each other along a set direction, and the two wall surfaces form an included angle of 85-95°. The metal layer at least continuously covers the wall of the trench; the conductive oxide layer and the dielectric layer are stacked between the substrate and the metal layer and are used to form an electrical connection between the substrate and the metal layer; When the modulated light is incident from the second surface of the substrate and a specified bias voltage is applied between the substrate and the metal layer, the absorption of light of a specified wavelength by the optical modulator can be controlled, thereby achieving the modulation of the optical signal.

2. The optical modulator according to claim 1, characterized in that: The groove wall includes two first wall surfaces arranged opposite each other along a first direction and two second wall surfaces arranged opposite each other along a second direction. The first wall surfaces and the second wall surfaces are both inclined, and an angle of 85-95° is formed between the two first wall surfaces and between the two second wall surfaces. The first direction and the second direction are perpendicular to each other.

3. The optical modulator according to claim 1 or 2, characterized in that: The included angle between the two walls is 90°.

4. The optical modulator according to claim 1 or 2, characterized in that: The first surface of the substrate is provided with a plurality of grooves, which are arranged in parallel along a first direction or a second direction.

5. The optical modulator according to claim 4, characterized in that: The gap between two adjacent slots shall not exceed 10% of the center distance between the two adjacent slots.

6. The optical modulator according to claim 1, characterized in that: The width of the groove opening in the set direction is 1-100μm.

7. The optical modulator according to claim 1, characterized in that: The conductive oxide layer is disposed between the dielectric layer and the metal layer, or the dielectric layer is disposed between the conductive oxide layer and the metal layer.

8. The optical modulator according to claim 1 or 7, characterized in that: The conductive oxide layer is made of metal oxides.

9. The optical modulator according to claim 8, characterized in that: The metal oxide includes any one or a combination of two or more of indium tin oxide, zinc oxide, aluminum-doped zinc oxide, gallium-doped zinc oxide, cadmium oxide, and indium-doped cadmium oxide.

10. The optical modulator according to claim 1 or 7, characterized in that: The thickness of the conductive oxide layer is 5-50 nm.

11. The optical modulator according to claim 1 or 7, characterized in that: The dielectric layer is made of any one or a combination of two or more of the following materials: silicon dioxide, silicon nitride, aluminum oxide, magnesium fluoride, hafnium oxide, and zinc selenide.

12. The optical modulator according to claim 1 or 7, characterized in that: The thickness of the dielectric layer is 5-50 nm.

13. The optical modulator according to claim 1 or 7, characterized in that: The metal layer is made of any one or a combination of two or more of the following materials: gold, silver, aluminum, copper, and titanium.

14. The optical modulator according to claim 1 or 7, characterized in that: The thickness of the metal layer is greater than 50 nm.

15. The optical modulator according to claim 14, characterized in that: The thickness of the metal layer is 50-100 nm.

16. The optical modulator according to claim 1 or 7, characterized in that: The substrate includes a silicon substrate.

17. The optical modulator according to claim 1, characterized in that: The metal layer, conductive oxide layer, and dielectric layer are all continuously and conformally covered on the first surface of the substrate.

18. The optical modulator according to claim 1, characterized in that: The second surface of the substrate is also covered with an anti-reflective film.

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