Method for Manufacturing an Electro-Optical Component and Electro-Optical Component

Abstract

Provided is a method for manufacturing an optical component, including the following steps: producing at least one optical waveguide or a part of an optical waveguide on a substrate, where producing the optical waveguide or the part of the optical waveguide includes producing a waveguide core or a portion of a waveguide core, and where the waveguide core or the portion of the waveguide core includes silicon nitride, a polymer or a III-V semiconductor material; and arranging at least one layer of lithium niobate on a side of the waveguide core or of the portion of the waveguide core facing away from the substrate. After arranging at least one layer of lithium niobate at least one of the following steps is carried out: structuring at least one layer of lithium niobate, producing a further portion of the waveguide core and/or arranging at least one contact structure for electrically contacting the at least one layer of lithium niobate.

Claims

1. A method for manufacturing an optical component, comprising the following steps: producing at least one optical waveguide or a part of an optical waveguide on a substrate, wherein producing the optical waveguide or the part of the optical waveguide comprises producing a waveguide core or a portion of a waveguide core, wherein the waveguide core or the portion of the waveguide core includes silicon nitride, a polymer or a III-V semiconductor material; arranging at least one layer of lithium niobate on a side of the waveguide core or of the portion of the waveguide core facing away from the substrate, wherein after arranging the at least one layer of lithium niobate, at least one of the following steps is carried out: structuring the at least one layer of lithium niobate, producing a further portion of the waveguide core and/or arranging at least one contact structure for electrically contacting the at least one layer of lithium niobate.

2. The method according to claim 1, wherein the layer of lithium niobate is connected to the optical waveguide or the part of the optical waveguide by means of a bonding method.

3. The method according to claim 2, wherein the bonding method comprises connecting the layer of lithium niobate to the optical waveguide or the part of the optical waveguide by means of at least one intermediate layer.

4. The method according to claim 1, wherein the substrate is a first wafer on which several optical waveguides or several parts of optical waveguides are produced at the same time to produce a plurality of optical components, wherein the layer of lithium niobate initially is arranged on a second wafer that is removed after carrying out the bonding method.

5. The method according to claim 1, wherein the structuring of the layer of lithium niobate comprises a partial removal of the layer of lithium niobate.

6. The method according to claim 5, wherein the partial removal of the layer of lithium niobate is effected in such a way that it forms a waveguide area that extends along the waveguide core or the portion of the waveguide core, wherein lateral depressions of the layer of lithium niobate each adjoin the waveguide area.

7. The method according to claim 1, wherein the portion of the waveguide core represents a first portion of the waveguide core, which is produced before arranging the layer of lithium niobate, wherein a second portion of the waveguide core is manufactured after arranging the layer of lithium niobate.

8. The method according to claim 7, wherein the first and the second portion of the waveguide core are produced on sides of the layer of lithium niobate facing away from each other.

9. The method according to claim 1, wherein arranging the at least one contact structure for electrically contacting the layer of lithium niobate comprises producing at least one metal layer on a side of the layer of lithium niobate facing away from the substrate.

10. The method according to claim 1, wherein producing the optical waveguide or the part of the optical waveguide comprises preparing a cladding layer on the substrate, wherein the waveguide core or the portion of the waveguide core is produced on the cladding layer.

11. The method according to claim 10, wherein after producing the waveguide core or the portion of the waveguide core on the cladding layer a further cladding layer is produced.

12. The method according to claim 1, wherein the waveguide core or the portion of the waveguide core includes silicon nitride, and the optical waveguide or the part of the optical waveguide comprises a waveguide cladding including silicon dioxide.

13. An optical component, comprising a substrate; an optical waveguide arranged on the substrate with a waveguide core or a portion of the waveguide core, wherein the waveguide core or the portion of the waveguide core includes silicon nitride, a polymer or a III-V semiconductor material; at least one layer of lithium niobate, which is located on a side of the waveguide core or of a portion of the waveguide core facing away from the substrate, wherein the layer of lithium niobate is configured in the form of a structure that extends along the waveguide core or the portion of the waveguide core, and/or on the layer of lithium niobate at least one contact structure is arranged for electrically contacting the at least one layer of lithium niobate.

14. The optical component according to claim 13, wherein the waveguide core includes first and second portions, wherein the first and the second portion are disposed on sides of the layer of lithium niobate facing away from each other.

15. The optical component according to claim 13, wherein the waveguide core includes silicon nitride.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The solution will be explained in detail below by means of exemplary embodiments with reference to the Figures.

[0031] FIG. 1 schematically shows a cross-section of an optical component according to a first exemplary embodiment of the solution.

[0032] FIG. 2 schematically shows a cross-section of an optical component according to a second exemplary embodiment of the solution.

[0033] FIG. 3 schematically shows a cross-section of an optical component according to a third exemplary embodiment of the solution.

DESCRIPTION OF THE INVENTION

[0034] FIG. 1 shows a cross-section of a partial section of an electro-optical component 1, for example of a modulator or a switch. The electro-optical component 1 comprises at least one optical waveguide 10 arranged on a substrate 20. The optical waveguide 10 includes a waveguide cladding 101 and a waveguide core 102 embedded in the same. Above the waveguide core 102, i.e. on a side of the waveguide core 102 facing away from the substrate 20, a layer 30 of lithium niobate is located. The lithium niobate layer 30 extends completely across the waveguide core 102 and at least across a part of the waveguide cladding 101.

[0035] In addition, two contact structures in the form of a first and a second electrode 41, 42 are located on the layer 30 of lithium niobate, which—as seen along the main plane of extension of the substrate 20—are arranged on different sides of the waveguide core 102. By means of the electrodes 41, 42, the layer 30 of lithium niobate can be contacted electrically so that by applying a voltage to the electrodes 41, 42 the refractive index of the lithium niobate layer 30 can be changed. The refractive index of the lithium niobate layer 30 in turn contributes to an effective index of refraction experienced by an optical mode guided in the waveguide 10, so that by applying a voltage to the electrodes 41, 42 the propagation of the optical mode can be influenced.

[0036] The waveguide core 102 for example is made of silicon nitride, while the waveguide cladding 101 is formed of silicon dioxide. The substrate 20 in particular is a silicon substrate, e.g. a wafer made of silicon. However, the solution is not limited to this material system; rather, the waveguide core 102 and the waveguide cladding 101 each might also be made of a polymer or a III-V semiconductor material. The electrodes 41, 42 in particular are configured in the form of a structured metal layer. The metal layer in particular comprises a structured gold layer.

[0037] For manufacturing the electro-optical component 1 shown in FIG. 1, as already explained above, a first cladding layer initially is arranged on the substrate 20 and a layer of the material of the waveguide core 102, for example said silicon nitride, is produced on the first cladding layer. Subsequently, the core material layer is structured, in particular by removing lateral areas of the core material layer, so that the rectangular cross-section of the waveguide core 102 shown in FIG. 1 is obtained. After structuring the core material layer, a second material layer is produced, in particular from the same material as the first cladding layer, which fills up the areas laterally of the waveguide core 102 and also extends above the core 102.

[0038] As likewise has already been explained above, this second cladding layer is planarized; for example, it is removed completely above the waveguide core 102. Subsequently, the layer 30 of lithium niobate initially arranged on a second substrate (not shown), in particular on a second wafer, is connected to the waveguide 10 by means of a bonding method, i.e. in particular connected to a surface of the waveguide core 102 and a surface of the waveguide cladding 101 each extending laterally of the waveguide core 102. Connecting the lithium niobate layer 30 can be effected by means of an (in particular adhesive) intermediate layer (not shown). It is also conceivable that the lithium niobate layer 30 is directly bonded to the surfaces of the waveguide cladding 101 and the waveguide core 102. In addition, it is conceivable that said second cladding layer is not removed completely so that connecting (bonding) the lithium niobate layer 30 to the waveguide 10 is effected via the remaining second cladding layer (and possibly via a further intermediate layer). After bonding the lithium niobate layer 30 to the waveguide 10, the second substrate (and possibly further material layers located between the lithium niobate layer 30 and the second substrate) is removed.

[0039] A modification of the electro-optical component 1 of FIG. 1 is shown in FIG. 2. Accordingly, the electrodes 41, 42 are arranged in a structured area 31 of the layer 30 of lithium niobate. The structured area 31 comprises depressions 311a, 311b laterally of the waveguide core 102, in which the lithium niobate layer 30 has partly been removed (except for areas 312a, 312b with a lower residual thickness) and in which the electrodes 41, 42 are arranged. It is also conceivable that the lithium niobate layer 30 is removed completely to produce the depressions 311a, 311b. Above the waveguide core 102 a waveguide area 313 of the lithium niobate layer 30 is disposed, which is defined by the depressions 311a, 311b and which—as seen parallel to the substrate 20—at least sectionally follows the course of the waveguide core 102 and which has a larger thickness—as seen perpendicularly to the substrate 20—than the areas 312a, 312b. In addition, the waveguide area 313 has a slightly larger width (expansion parallel to the substrate 20) than the waveguide core 102. It is also conceivable, however, that the waveguide area 313 at least approximately has the same width as the waveguide core 102 or a smaller width than the waveguide core 102.

[0040] The electro-optical component 1 according to the solution, which is shown in FIG. 3, includes an optical waveguide 10 with a waveguide core 102, wherein the waveguide core 102 has a first and a second portion 1021, 1022, which are disposed on sides of the layer 30 of lithium niobate facing away from each other. The portions 1021, 1022 of the waveguide core 102 each are surrounded by first and second portions 1011, 1012 of a waveguide cladding 101. The portions 1011, 1012 of the waveguide cladding 101 correspondingly extend analogously to the portions 1021, 1022 of the waveguide core 102 likewise on sides of the layer 30 of lithium niobate facing away from each other. The lower portion 1011 of the waveguide cladding 101 is arranged on a (non-illustrated) substrate (analogously to FIGS. 1 and 2). For example, the waveguide core 102, i.e. the portions 1021, 1022, is made of silicon nitride, and the waveguide cladding 101 (its portions 1011, 1012) of silicon dioxide. The substrate used can again be a silicon substrate, e.g. a wafer made of silicon. Other material systems, however, likewise are possible, as already explained above.

[0041] The manufacture of the component shown in FIG. 3 initially is effected analogously to the method described in connection with FIG. 1. After bonding the layer 30 of lithium niobate to a lower part of the waveguide 10, i.e. to the first (lower) portion 1011 of the waveguide cladding 101, and to the first (lower) portion 1021 of the waveguide core 102, a layer of the material of the second portion 1022 of the waveguide core 102 is produced on the lithium niobate layer 30 and its rectangular cross-section is obtained by laterally removing this material. The width (parallel to the substrate or to the lithium niobate layer 30) of the second portion 1022 of the waveguide core 102 in particular corresponds to the width of the first portion 1021 of the waveguide core 102. Subsequently, the material of the upper portion 1012 of the waveguide cladding 101 is deposited. Further processing steps can follow, for example machining (e.g. planarizing) the upper portion 1012 of the cladding layer 101 and/or mounting electrodes for contacting the layer 30 of lithium niobate.