Optical arrangement

Abstract

Optical arrangement, with - at least one optical waveguide (11); and - at least one element (2) with at least one layer (21, 21a, 21b) formed from a two-dimensional material, wherein - the element (2) is arranged relative to the waveguide (11) such that - light exiting the waveguide (11) enters position (21, 21a, 21b) and / or is reflected at position (21, 21a, 21b); and / or - light exiting from layer (21, 21a, 21b) and / or reflected at layer (21, 21a, 21b) couples into the waveguide (11), characterized by the fact that the element (2) has an electrical contact (3a, 3b) for applying a voltage to the layer (21) made of the two-dimensional material, wherein the optical waveguide (11) is oriented relative to the layer (21) such that, at a predefinable voltage that can be applied to the layer (21) via the electrical contact (3a, 3b), light emerging from the waveguide (11) is totally reflected at the layer (21) and, at a different voltage, is at least partially transmitted through the layer (21), wherein the optical arrangement comprising a first output waveguide (110) into which the totally reflected light couples, and a second output waveguide (120) into which the transmitted light couples, and wherein the first output waveguide (110) forms an angle with the normal of the layer (21, 21a, 21b) made of the two-dimensional material, which corresponds to the angle formed by the waveguide (11) with this normal.

Description

[0001] The invention relates to an optical arrangement according to the preamble of claim 1.

[0002] Two-dimensional materials, i.e., materials with only one or a few atomic layers, have received considerable attention in materials science in recent years. Due to their structure, two-dimensional materials (e.g., graphene) possess unique mechanical, optical, and electrical properties. In particular, they are characterized by high charge carrier mobility, and manufacturing processes have recently been optimized to such an extent that these materials can be produced on a large scale with good quality and subsequently transferred to a desired substrate.

[0003] Furthermore, KR 10 2014 075 404 A and US 2015 / 0 168 747 A1 disclose the use of two-dimensional materials for light manipulation. Document US 2013 / 0 120 752 A1 describes a sensor using a two-dimensional material.

[0004] This makes it possible to utilize the electrical and optical properties of two-dimensional materials in optical or optoelectronic components, or in combination with such components. One such application is described, for example, in the article by Ye, Shengwei, et al., “Electro-absorption optical modulator using dualgraphene-on-graphene configuration”, Optics express 22.21 (2014): 26173-26180.

[0005] The problem to be solved by the invention is to make the use of two-dimensional materials for light manipulation more efficient.

[0006] This problem is solved by providing the optical arrangement with the features of claim 1.

[0007] An optical arrangement is then provided, with - at least one optical waveguide; and - at least one element with at least one layer formed from a two-dimensional material, wherein - the element is arranged relative to the waveguide in such a way that - light exiting the waveguide enters the layer (in particular, is transmitted) and / or is reflected at the layer; and / or - couples light exiting from the position and / or reflected at the position into the waveguide, whereby - the element has an electrical contact for applying a voltage to the layer made of the two-dimensional material, wherein the optical waveguide is oriented relative to the layer such that, at a predetermined voltage that can be applied to the layer via the electrical contact, light exiting the waveguide is totally reflected at the layer and, at a different voltage, is at least partially transmitted through the layer, wherein the optical arrangement comprises a first output waveguide into which the totally reflected light couples, and a second output waveguide into which the transmitted light couples, and wherein The first output waveguide forms an angle with the normal of the layer from the two-dimensional material that corresponds to the angle formed by the waveguide with this normal.

[0008] The "two-dimensional material" is, for example, a layer of material consisting of one or a maximum of 10 atomic layers. For example, the layer is formed from graphene, triazine-based graphitic carbon nitride, germanene, molybdenum disulfide, molybdenum diselenide, and / or silicene, or comprises at least one of these materials, in both single- and multi-atom layers. It is also conceivable that the two-dimensional material (e.g., the aforementioned graphene) contains a dopant. However, the invention is not limited to the use of any one of these two-dimensional materials. The optical arrangement according to the invention, in particular, forms at least a part of an optical or optoelectronic component or can be combined with such a component.

[0009] The element with at least one layer formed from the two-dimensional material is used in particular to influence light (e.g., to change the amplitude and / or phase of the light, especially to modulate it). It is also conceivable that the element (especially if designed as a thin-film element) serves to detect light.

[0010] The layer of the two-dimensional material is therefore not parallel to the waveguide. It is possible that the optical waveguide has a (e.g., elongated) recess (particularly in the form of a break), with the element being at least partially located within the recess. In particular, the recess is oriented such that the element located within it extends obliquely to the optical waveguide (e.g., transversely or obliquely to the waveguide). For example, the recess itself may be oblique to the optical waveguide.

[0011] It is also conceivable that the optical waveguide is formed (in a manner known per se) by layers of material (in particular semiconductor layers, polymer layers, or dielectric layers) arranged on a substrate, wherein the element is, in particular, arranged at least partially in a recess of the substrate. For example, the element is arranged in a recess that extends through at least a portion of the waveguide (at least a portion of the waveguide core) into the substrate, i.e., it forms a continuous recess encompassing both the aforementioned recess in the waveguide and the recess in the substrate. The recess is produced, in particular, by material removal, for example, by sawing or etching.

[0012] The element is thus arranged at an angle to the direction of propagation of the light guided in the waveguide, so that the area (the optically effective area) of the element need not be larger than the waveguide cross-section (or at least not larger than the cross-section of the waveguide core). It is conceivable that the area of ​​the element is on the order of only a few square micrometers and that the element has, for example, an edge length on the order of a few tens or hundreds of micrometers. A compact design of the element can have the advantage that, for example, unwanted capacitances that limit the bandwidth of the optical arrangement are reduced. Accordingly, a higher detection and / or modulation speed can be achieved. Furthermore, with such an arranged element, a simple, compact, and cost-effective integration of active functions (such as...) is possible.This enables the generation of light or the aforementioned light detection in waveguide networks, and in particular with thin-film components (e.g., those used in optical communications). Furthermore, a larger number of components can be manufactured simultaneously.

[0013] The layer of two-dimensional material is arranged on a substrate (support layer) of the element. For example, the element has a thickness of 1 to 200 µm (essentially determined by the substrate thickness). It is conceivable that the substrate contains further thin-film structures or is at least compatible with another (especially optoelectronic) thin-film device. For example, a dielectric material is used as the substrate material. Suitable substrate materials include, for example, polymer, silicon dioxide, silicon nitride, titanium dioxide, silicon, hafnium dioxide, hafnium silicate, zirconium silicate, zirconium dioxide, aluminum dioxide, magnesium fluoride, zinc sulfide, praseodymium titanium oxide, gallium arsenide, and / or indium phosphide.

[0014] However, the element does not necessarily have to be located in a recess of the waveguide and / or the substrate. It is also conceivable, for example, that it is located adjacent to or even abutting a facet of the optical waveguide. For instance, the element could be in direct contact with the facet of the optical waveguide and, for example, also connected to it.

[0015] According to the invention, the element has at least one electrical contact (e.g., made of a metal or a conductive alloy) connected to a layer of the two-dimensional material. A voltage can be applied to the element via this electrical contact to control the light-emitting effect of the element. It is conceivable that the element has several layers of a two-dimensional material, each layer, for example, comprising at least one area that does not overlap with the other layer. For instance, the layers are provided with electrical contacts in the non-overlapping areas, and a voltage can be applied via these electrical contacts, particularly across the area of ​​the element where the layers of the two-dimensional material overlap. It is also possible, of course, for the layers to overlap at least approximately completely.

[0016] In one embodiment, the element comprises a first and a second layer of a two-dimensional material, the layers being separated from each other by a material region, similar to a capacitor. This material region consists, for example, of an electrically insulating (in particular, dielectric) material.

[0017] Furthermore, a first electrical contact may be present, connected at least to the first layer, as well as a second electrical contact, connected at least to the second layer. A voltage can be applied via the electrical contacts across the first or the second layer and / or the material region between the first and second layers; in particular, to modify the optical properties of the element.

[0018] According to the invention, the element constitutes an optical switch. With the help of the element (i.e., with the help of the layer of two-dimensional material), not only can the intensity or phase of light be changed (in particular, modulated), but the path of the light can also be switched.

[0019] As mentioned above, the element with at least one layer of two-dimensional material can be designed and arranged, in particular, for light generation, light detection, and / or light modulation. Specifically, the element can be used for light modulation by utilizing electro-optical effects and / or electroabsorption effects.

[0020] The invention will be explained in more detail below with reference to exemplary embodiments and the figures. The figures show: Fig. 1 a simulation of the refractive index and absorption coefficient of graphene as a function of the chemical potential at a light wavelength of 1550 nm; Fig. 2 a schematic top view of an optical arrangement according to an unclaimed example; Fig. 3 a schematic top view of an optical arrangement according to an unclaimed example; Fig. 4 a top view of a thin-film element for an optical arrangement according to the invention; Fig. 5 a sectional view of another embodiment of the thin-film element; Fig. 6 a modification of the thin-film element made of Fig. 5; Fig. 7 another modification of the thin-film element made of Fig. 5; Fig. 8 a schematic top view of an optical arrangement according to an embodiment of the invention; and Fig. 9 a sectional view of an unused optical filter.

[0021] In Fig. Figure 1 shows the dependence of the refractive index (left y-axis) and the absorption coefficient (right y-axis) of graphene on the chemical potential for a wavelength of 1550 nm. The values ​​shown in Fig. The simulation underlying the depicted curves of the refractive index and absorption coefficient assumes a structure comprising two electrically isolated graphene layers. The electric field for shifting the chemical potential is generated by a voltage between the two graphene layers, i.e., by creating an electric field perpendicular to the graphene plane.

[0022] As in Fig. As can be seen in Figure 1, the absorption coefficient of graphene is over 200,000 1 / cm at chemical potentials up to 0.35 eV and drops to approximately 10,000 1 / cm at 0.4 eV. By switching between points of high and low absorption, graphene can be used, for example, to create an electroabsorption modulator. Simultaneously, the refractive index of the graphene layers exhibits a variation of more than 5 (down to 0.2) at chemical potentials around 0.4 eV. Switching between these two points allows, in particular, the modulation of the phase of the light interacting with the graphene layer (especially the light passing through it).

[0023] Fig. Figure 2 shows a top view of an optical arrangement in the form of a waveguide arrangement 1 (e.g., an optical circuit). The waveguide arrangement 1 includes an integrated optical waveguide 11, which is formed in a known manner by layers of material arranged on a substrate 12. For example, the waveguide 11 is a finned waveguide, which has a fin projecting from the substrate. It is also conceivable that the waveguide is a buried waveguide whose waveguide core is surrounded by layers of material. However, it should be noted that the invention does not necessarily require an integrated optical waveguide. Rather, an optical fiber, for example, could also be used as the waveguide.

[0024] In addition to the waveguide 11, the waveguide assembly 1 comprises a thin-film element 2, which is arranged in a slot-like recess 13 of the waveguide 11 and the substrate 12. The recess 13 extends through the waveguide 11 into the substrate 12, so that the waveguide is placed in a first (in Fig. The thin-film element 2 is divided into two (left) sections 111 and a second (right) section 112. The thin-film element 2 comprises at least one layer 21, which consists of a two-dimensional material such as graphene. The layer 21 is arranged on a substrate in the form of a support layer 22 (support substrate).

[0025] The recess 13, and thus the thin-film element 2 (“2d material thin-film element”), is oriented transversely to the optical waveguide 11. Accordingly, light is guided to the thin-film element 2 (i.e., to layer 21) via the first section 111 of the optical waveguide 11, with the light passing at least partially through layer 21 and also through the support layer 22 and coupling into the second section 112 of the waveguide 11. Layer 21 can be used to influence the light guided in the first section 111 of the waveguide 11, for example, by at least partially attenuating it. Such attenuation can, for instance, occur periodically, resulting in a modulation of the light. It is also conceivable, however, that light can be detected using layer 21, and information about the light arriving at layer 21 can be obtained.

[0026] The first and / or the second waveguide section 111, 112 can be directly adjacent to the thin-film element 2 (e.g., in contact with the thin-film element 2). However, it is also possible that there is a gap between the first and / or the second waveguide section 111, 112 and the thin-film element 2.

[0027] Naturally, the thin-film element 2 can have more than one layer of the two-dimensional material. Furthermore, it should be noted that the thin-film element 2 (in Fig. The thin-film element 2 projects upwards and downwards) beyond the waveguide 11 (at least beyond its core). However, this is not mandatory. Rather, the extent of the thin-film element 2 perpendicular to the direction of extension of the waveguide 11 could be only slightly larger than the width of the waveguide (at least of the core) or identical to the width of the waveguide. It is also conceivable that the extent of the thin-film element 2 is even smaller than the width of the waveguide. It is also possible, in principle, that there is a recess oriented longitudinally to the waveguide 11, rather than transversely, in which the thin-film element 2 is arranged. However, even in this configuration, the layer 21 or the multiple layers of the thin-film element 2 are oriented obliquely or perpendicularly to the waveguide 11.

[0028] Fig. Figure 3 shows another optical arrangement, which is also designed as a waveguide arrangement 1. Accordingly, the thin-film element 2 is not arranged in a recess of the waveguide 11 and / or the substrate 12, but is located on a facet 113 of the waveguide 11. In particular, the facet 113 is part of an end face of a component (e.g., an optochip) that comprises the substrate 12 and the waveguide 11. It is conceivable that the thin-film element 2 in this configuration serves to detect light that is guided to the thin-film element 2 in the waveguide 11. Alternatively or additionally, light (e.g., via a free beam) can be coupled into the waveguide 11 via the thin-film element 2. It is also possible that the thin-film element 2 is connected to the facet 113.

[0029] Fig. Figure 4 shows a possible design of a thin-film element 2, which is used, for example, in the examples of Fig. 2 or Fig. 3 can be used. The thin-film element 2 then comprises at least two parallel but spaced-apart layers 21a, 21b made of a two-dimensional material, with a (particularly electrically insulating) material layer located between these layers.

[0030] Layers 21a and 21b are structured, meaning they are not simply flat surfaces covering the support layer 22, but have a defined contour. In this case, layers 21a and 21b each have a (rectangular) first section 211a and 211b, which defines an interaction area of ​​the thin-film element 2. Each first section 211a and 211b is followed by a connecting section 212a and 212b, which in turn is connected to a (e.g., metallic) contact surface 3a and 3b, forming a capacitor-like structure. A voltage can be applied to layers 21a and 21b via the contact surfaces 3a and 3b.

[0031] The light to be manipulated or detected with the aid of the thin-film element 2 is directed in particular to the region of the thin-film element 2 where the first sections 211a, 211b of the layers 21a, 21b overlap. For example, this region is coupled to a waveguide (not shown). It is conceivable, in particular, that the waveguide is configured as in the Fig. 2 and Fig. 3 shown perpendicular (or at least oblique) to the plane along which layers 21a and 21b each extend.

[0032] The thin-film element 2 can, of course, comprise further layers of a two-dimensional material and correspondingly further material layers between these layers, whereby at least some of the further layers can also be provided with a contact surface. The further layers can be structured. However, this is not mandatory.

[0033] It is also conceivable that only one (e.g. analogous to positions 21a, 21b of the Fig. 4 structured) layer 21 made of a two-dimensional material is present, which is connected to both the first contact surface 3a and the second contact surface 3b ( Fig. 5) Such a thin-film element 2 can be used, for example, for light generation and / or light detection. Of course, several can be used, e.g. (especially according to Fig. 4) Structured layers 21a, 21b are present, wherein the layers 21a, 21b are each connected, for example, to both one contact surface 3a and the other contact surface 3b, i.e., connected in parallel. The layers 21a, 21b are arranged on support layers 22a - 22c, wherein one of the support layers 22a - 22c (the support layer 22b) is located between the layers 21a, 21b ( Fig. 6).

[0034] An arrangement analogous to Fig. 4 shows the Fig. Figure 7 shows a cross-sectional view. The layers 21a and 21b of the two-dimensional material are each connected to only one of the contact surfaces 3a and 3b, so that when a voltage is applied to the contact surfaces 3a and 3b, a voltage builds up across the layers 21a and 21b and the support layer 22b located between them (i.e., an electric field directed perpendicular to the layers 21a and 21b is generated, similar to a capacitor). Such a thin-film element can be used to modulate the amplitude and / or phase of light.

[0035] Fig. 8 refers to an embodiment of the invention. According to this embodiment, an optical arrangement according to the invention is in the form of a waveguide arrangement 1, which is Fig. 8 shown in top view, is designed in that an optical waveguide 11 (input waveguide) is provided, through which light is directed to a thin-film element 2, which, as shown in the preceding figures, consists of a substrate 22 with at least one layer 21 of a two-dimensional material arranged on the substrate 22.

[0036] The thin-film element 2 is arranged in a recess 13, in particular in a substrate 12, and oriented such that the waveguide 11 runs at an angle to the layer 21. More precisely, the waveguide 11 runs at such an angle that the light emerging from it strikes the layer 21 at an angle at which it is totally reflected by the layer 21 and, accordingly, no light is transmitted through the thin-film element 2.

[0037] The totally reflected light can be received by a further waveguide (first output waveguide 110), wherein the output waveguide 110 forms an angle with the normal of position 21 that corresponds to the angle formed by the waveguide 11 with this normal.

[0038] By applying a voltage to the thin-film element 2, particularly to layer 21, the effective refractive index of the thin-film element 2, and thus the angle of total internal reflection, can be changed. In particular, a voltage can be applied that changes the effective refractive index such that the light brought to the thin-film element 2 via the waveguide 11 is no longer totally reflected, but is at least partially transmitted through the thin-film element 2.

[0039] The transmitted light can be received by a second output waveguide 120, which is located on the other side of the thin-film element 2. In particular, the second output waveguide 120 is aligned at least approximately parallel to the input waveguide 11 (e.g., but offset along the thin-film element 2). The thin-film element 2 of the Fig. 8 thus acts as an optical switch, with which the input light guided via the waveguide 11 can be switched to either the first or the second output waveguide 110, 120.

[0040] Fig. Figure 9 shows an example of an optical filter 4. The optical filter 4 has a similarity to the Fig. Figure 7 shows a thin-film element 2 with at least two layers 21a, 21b made of a two-dimensional material. The layers 21a, 21b are arranged on support layers 22a - 22c, with the support layer 22b extending between the layers 21a, 21b and electrically insulating the layers 21a, 21b from each other. For example, at least the middle support layer 22b consists of a dielectric material. It is also conceivable that at least two of the support layers 22a - 22c are made of different materials. For example, the outer support layers 22a, 22c are made of the same material (e.g., a polymer), while the middle support layer 22b consists of a different material. Of course, in this embodiment, more than the two layers shown and correspondingly more than three support layers can also be present.

[0041] The filter is therefore a multi-layer filter whose optical properties are determined primarily by interference of the light reflected and / or transmitted by the individual layers. Analogous to Fig. 7. Layers 21a, 21b and the support layer 22b can be subjected to a voltage via contact surfaces 3a, 3b. By applying a voltage, the effective refractive index of the layer stack formed from layers 21a, 21b and the support layers 22a–22c can be changed. Thus, by applying a voltage, the optical properties of the filter 4, and therefore its absorption or transmission behavior, can be controlled. For example, it would be possible to switch between a reflective and a transmitting state of the filter 4.

[0042] It is conceivable that the optical filter 4 is combined with the one in Fig.The thin-film element 2 shown in Figure 9 is used in a free-jet arrangement, i.e., light strikes the thin-film element 2 of the filter 4 obliquely or perpendicularly to layers 21a, 21b. However, it is also possible for light to be guided to the thin-film element 2 via a waveguide. For example, the filter 4 can form a controllable antireflective coating or a highly reflective coating of a (especially optical) surface.

Claims

[1] Optical arrangement, with - at least one optical waveguide (11); and - at least one element (2) with at least one layer (21, 21a, 21b) formed from a two-dimensional material, wherein - the element (2) is arranged relative to the waveguide (11) such that - light exiting the waveguide (11) enters position (21, 21a, 21b) and / or is reflected at position (21, 21a, 21b); and / or - light exiting from layer (21, 21a, 21b) and / or reflected at layer (21, 21a, 21b) couples into the waveguide (11), characterized by , that the element (2) has an electrical contact (3a, 3b) for applying a voltage to the layer (21) made of the two-dimensional material, wherein the optical waveguide (11) is oriented relative to the layer (21) such that, at a predefinable voltage that can be applied to the layer (21) via the electrical contact (3a, 3b), light emerging from the waveguide (11) is totally reflected at the layer (21) and, at a different voltage, is at least partially transmitted through the layer (21), wherein the optical arrangement comprising a first output waveguide (110) into which the totally reflected light couples, and a second output waveguide (120) into which the transmitted light couples, and wherein the first output waveguide (110) forms an angle with the normal of the layer (21, 21a, 21b) made of the two-dimensional material, which corresponds to the angle formed by the waveguide (11) with this normal. [2] Optical arrangement according to claim 1, characterized by , that the layer (21, 21a, 21b) consists of one atomic layer or of a maximum of ten atomic layers of a material. [3] Optical arrangement according to claim 1 or 2, characterized by that the two-dimensional material is formed from graphene, triazine-based graphitic carbon nitride, germanene, molybdenum disulfide, molybdenum diselenide and / or silicene, or at least contains one of these materials. [4] Optical arrangement according to any one of the preceding claims, characterized by , that the optical waveguide (11, 110, 120) has a recess (13) wherein the element (2) is at least partially arranged in the recess (13). [5] Optical arrangement according to any one of the preceding claims, characterized by , that the optical waveguide (11, 110, 120) is formed by layers of material arranged on a substrate (12), wherein the element (2) is arranged at least partially in a recess (13) of the substrate (12). [6] Optical arrangement according to any one of the preceding claims, characterized by, that the element (2) comprises at least one electrical contact (3a, 3b) connected to the layer (21, 21a, 21b) of the two-dimensional material. [7] Optical arrangement according to any one of the preceding claims, characterized by , that the element (2) has several layers (21a, 21b) of a two-dimensional material. [8] Optical arrangement according to claim 7, characterized by , that the layers (21a, 21b) each have at least one area that does not overlap with the other layer (21a, 21b). [9] Optical arrangement according to any one of the preceding claims, characterized by , that the element (2) has a first and a second layer (21a, 21b) of a two-dimensional material, wherein the layers (21a, 21b) are separated from each other by a material region (22b). [10] Optical arrangement according to claim 9, characterized bya first electrical contact (3a) connected at least to the first layer (21a) and a second electrical contact (3b) connected at least to the second layer (21b). [11] Optical arrangement according to any one of the preceding claims, characterized by , that the element (2) is designed and arranged for light generation, light detection and / or light modulation.

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