Abstract
The present disclosure relates to an optoelectronic device for manipulating electromagnetic radiation. Drawbacks of conventional systems like material constraints, system complexity and tuning speed are overcome by the optoelectronic device comprising a substrate with at least one tuning structure arranged on the substrate, wherein the tuning structure comprises an electro-optical material. The tuning structure comprises a first and a second electrical contact. A cover layer covers the at least one tuning structure. An optical structure is arranged on the cover layer. A voltage source is electrically connected to the first and the second electrical contact and provided for generating electric fields within the at least one tuning structure.
Claims
1. An optoelectronic device for manipulating electromagnetic radiation, the optoelectronic device comprising: a substrate having a main plane of extension, at least one tuning structure arranged on a main surface of the substrate, the tuning structure comprising an electro-optical material, wherein the at least one tuning structure comprises a first electrical contact at a first side of the tuning structure and a second electrical contact at a second side of the tuning structure, a cover layer covering the at least one tuning structure, an optical structure arranged on the cover layer, so that the cover layer is arranged between the optical structure and the at least one tuning structure, a voltage source electrically connected to the first electrical contact and the second electrical contact, the voltage source being provided for generating electric fields within the at least one tuning structure, wherein the optical structure comprises a target specification being a member of a group comprising a focal length, a deflection angle, a phase delay, a light polarization and a pattern projection, and wherein the target specification of the optical structure is altered by controlling the electric fields within the at least one tuning structure.
2. The optoelectronic device according to claim 1, wherein at least one optical property of the tuning structure is altered by applying a respective electric field.
3. The optoelectronic device according to claim 1, wherein the optical structure comprises structural elements each being smaller than a wavelength of electromagnetic radiation to be manipulated.
4. The optoelectronic device according to claim 1, wherein the optical structure comprises a meta-material.
5. The optoelectronic device according to claim 1, wherein the optical structure forms one member of a group comprising a lens, a diffraction grating, a zone plate, a phase plate, a holographic plate and a diffusor.
6. (canceled)
7. The optoelectronic device according to claim 1, wherein in a top-view the tuning structure comprises a circumferential portion.
8. The optoelectronic device according to claim 7, wherein in top-view at least one further tuning structure comprises at least one further circumferential portion, the at least one further circumferential portion surrounding the circumferential portion in lateral directions, that extend parallel to the main plane of extension of the substrate.
9. The optoelectronic device according to claim 1, further comprising a plurality of tuning structures forming an array of tuning structures.
10. The optoelectronic device according to claim 1, wherein the first electrical contact and the second electrical contact are arranged on respective side surfaces of the tuning structure, where the side surfaces run perpendicular or transverse with respect to the main plane of extension of the substrate.
11. The optoelectronic device according to claims 1, wherein the first electrical contact and the second electrical contact are arranged on a top surface and a rear surface of the tuning structure, respectively, the top surface and the rear surface being parallel to the main plane of extension of the substrate and the top surface and the rear surface being arranged at opposing sides of the tuning structure.
12. The optoelectronic device according to claim 1, further comprising a plurality of tuning structures, wherein the electric field generated by the voltage source is different in at least two of the tuning structures during operation.
13. The optoelectronic device according to claim 1, wherein in the at least one tuning structure the electric field generated by the voltage source is variable in time during operation.
14. The optoelectronic device according to claim 1, wherein the electromagnetic radiation to be manipulated is in the infrared, the near-infrared or in the visible wavelength range, or in a range overlapping at least two of these wavelength ranges.
15. The optoelectronic device according to claim 1, wherein the tuning structure comprises a solid-state inorganic material.
16. An electronic system comprising the optoelectronic device according to claim 1, wherein the electronic system is in particular an optoelectronic system provided for emitting and/or sensing electromagnetic radiation.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0050] FIG. 1 shows a cross-section of an embodiment of an optoelectronic device.
[0051] FIGS. 2a to 2d show top-views of embodiments of an optoelectronic device.
[0052] FIG. 3 shows another top-view of an embodiment of an optoelectronic device.
[0053] FIG. 4 shows another top-view of an embodiment of an optoelectronic device.
[0054] FIG. 5 shows another cross-section of an embodiment of an optoelectronic device.
[0055] FIG. 6 shows another cross-section of an embodiment of an optoelectronic device.
[0056] FIG. 7 shows another cross-section of an embodiment of an optoelectronic device.
[0057] FIG. 8 shows a simulation result according to an embodiment of an optoelectronic device.
DETAILED DESCRIPTION
[0058] In FIG. 1 a cross-section of an embodiment of an optoelectronic device 1 is shown. The embodiment according to FIG. 1 comprises a substrate 2 with a main surface 3. The substrate 2 has a main plane of extension. Lateral directions x, y extend parallel to the main plane of extension of the substrate 2. At least one tuning structure 4 is arranged on the main surface 3 of the substrate 2. In the example shown in FIG. 1 there are four tuning structures 4 arranged on the main surface of the substrate 2. In lateral directions x, y the tuning structures 4 have a distance to each other. This means the tuning structures 4 are spaced apart from each other. The tuning structures 4 each have a top surface 5 and a rear surface 6, which are parallel to the main plane of extension of the substrate 2. The top surface 5 and the rear surface 6 are arranged at opposing sides of each tuning structure 4. The rear surface 6 of each tuning structure 4 faces the substrate 2. The top surface 5 faces away from the substrate 2.
[0059] Each tuning structure 4 comprises a first electrical contact 7 and a second electrical contact 8. The electrical contacts 7, 8 comprise a different material in comparison to the remaining tuning structure 4. In the embodiment shown in FIG. 1 the first electrical contact 7 is arranged on the top surface 5 of the tuning structure 4. The second electrical contact 8 is arranged on the rear surface 6 of the tuning structure 4. The electrical contacts 7, 8 cover the whole top surface 5 or, respectively, the whole rear surface 6 of the tuning structure 4. However, in other embodiments the electrical contacts 7, 8 cover only portions of the respective surfaces 5, 6 of the tuning structure 4. In the embodiment shown in FIG. 1 the side surfaces 9 of the tuning structure 4 are free from an electrical contact 7, 8. This means that the first electrical contact 7 and the second electrical contact 8 are not physically or electrically connected to each other.
[0060] The optoelectronic device 1 according to FIG. 1 further comprises a cover layer 10. The cover layer 10 can comprise the same material as the substrate 2. However, the cover layer 10 can also comprise a different material. The cover layer 10 covers the at least one tuning structure 4 on all its sides, apart from the rear surface 6, which faces the substrate 2. However, the electrical contacts 7, 8 are still accessible. On regions, which are free from the at least one tuning structure 4, the cover layer 10 is in direct contact with the substrate 2. The cover layer 10 has a top surface 11. The top surface 11 may extend parallel to the main plane of extension of the substrate 2.
[0061] On the top surface 11 of the cover layer 10 an optical structure 12 is arranged. In a transversal direction z, which is perpendicular to the main plane of extension of the substrate 2, the optical structure 12 is above the tuning structure 4. The cover layer 10 is arranged between the tuning structure 4 and the optical structure 12. In the embodiment shown in FIG. 1 the optical structure 12 comprises a plurality of structural elements 13. This means that the optical structure 12 has a structured surface 21, which forms a pattern. The pattern is formed by recesses 14 on the one side and by the structural elements 13 on the other side. In the transversal direction z the optical structure 12 has a thickness. As shown in FIG. 1 the recesses 14 extend over the entire thickness of the optical structure 12, so that portions of the top surface 11 of the cover layer 10 are exposed. This means that the structural elements 13 of the optical structure 12 are disconnected from each other. However, FIGS. 6 to 8 show different concepts of the optical structure, which will be discussed below.
[0062] As shown in FIG. 1 the optoelectronic device 1 further comprises a voltage source 15. The voltage source 15 can be, as shown, an external voltage source 15. However, the voltage source 15 can also be integrated in the substrate 2. The voltage source 15 is electrically connected to the first electrical contact 7 and the second electrical contact 8 of the at least one tuning structure 4. For the sake of presentation only one of the tuning structures 4 is connected to the voltage source 15 in FIG. 1. However, each tuning structure 4 may be connected to the same voltage source 15 or to further voltage sources 15. The voltage source 15 is provided to generate an electric potential difference between the first electrical contact 7 and the second electrical contact 8. This in turn generates an electric field within the at least one tuning element 4. The electrical connection from the voltage source 15 to the first and the second electrical contacts 7, 8 is achieved by means of electrically conductive wires 16. The electrically conductive wires 16 can comprise the same or a different material as the electrical contacts. The electrically conductive wires 16 can, as shown in FIG. 1, be integrated in the substrate 2 and the cover layer 10. The electrical contacts 7, 8 may be accessible via the electrically conductive wires.
[0063] During operation electromagnetic radiation reaches a rear surface 17 of the substrate 2 as indicated by the three arrows. Subsequently, the electromagnetic radiation passes through the substrate 2, the tuning structures 4 and the cover layer 10 and reaches the optical structure 12. The optical structure 12 manipulates the electromagnetic radiation in a predefined way. The optical structure 12 has a target specification manipulating the electromagnetic radiation, for example by means of a focal length, a deflection angle or the like. By applying an electric field to the tuning structure 4 the input wavefront of the electromagnetic radiation is modified, for example by a phase delay, so that when the modified wavefront passes through the optical structure 12, the result is a controlled deviation from the original target specifications of the optical structure 12.
[0064] FIGS. 2a to 2d show different embodiments of structural elements 13 of the optical structure 12 in a top-view. The top-view refers to a view on the optoelectronic device 1 from a side of the cover layer 10, which faces away from the substrate 2. FIGS. 2a to 2d show only details of one respective structural element 13 arranged on the top surface 11 of the cover layer 10. The length, width and distance to other structural elements can in particular be smaller than the wavelength of the electromagnetic radiation to be manipulated.
[0065] FIG. 2a shows a structural element 13, which has a rectangular shape, wherein the length, which refers to the structural element's dimension in y-direction is larger than its width, which refers to the structural element's dimension in x-direction. However, the proportions of the structural element 13 can also be equal or can be interchanged.
[0066] Moreover, such structural element 13 can be rotated in lateral directions x, y. The orientation of the structural element 13 in lateral directions x, y can be equal or different with respect to the orientation of neighboring structural elements 13.
[0067] FIG. 2b shows a structural element 13 on top of the cover layer 10, which has a plus-shape. As in the previous embodiment, such structural element 13 can be rotated in lateral directions x, y. The orientation of the structural element 13 in lateral directions x, y can be equal or different with respect to the orientation of neighboring structural elements 13.
[0068] FIG. 2c shows a structural element 13 on top of the cover layer 10, which has an L-shape. As in the previous embodiment, such structural element 13 can be rotated in lateral directions x, y. The orientation of the structural element 13 in lateral directions x, y can be equal or different with respect to the orientation of neighboring structural elements 13.
[0069] FIG. 2d shows a structural element 13 on top of the cover layer 10, which has a curved shape in top-view. In this embodiment the structural element 13 forms an oval. However, any other curved shape is also possible, as for example a circle.
[0070] It should be noted that all shown embodiments of structural elements 13 can also be combined with each other, so that at least two of the structural elements 13 comprise different shapes.
[0071] In FIG. 3 the top-view of another embodiment of the optoelectronic device 1 is shown. In this case the optoelectronic device 1 comprises a substrate 2 and a cover layer 10, which have a round shapes in top-view. The tuning structure 4 of the optoelectronic device 1 comprises a circumferential portion 18. In this case, the circumferential portion 18 forms a ring on the substrate 2. The ring formed by the circumferential portion 18 has a diameter and surrounds a region, which is free of the tuning structure 4. A further tuning structure 4′ comprises a further circumferential portion 19. The further circumferential portion 19 has a larger diameter than the circumferential portion 18 and surrounds the circumferential portion 18 in lateral directions x, y. At one side the further circumferential portion comprises a gap. This means that the further circumferential portion 19 forms a split ring.
[0072] The tuning structure 4 and the further tuning structure 4′ also comprise a first electrical contact 7. As mentioned above, the first electrical contact 7 is arranged on the top surface 5 of the respective tuning structure 4, 4′, this means on the side of the tuning structure 4, 4′, which faces towards the viewer of FIG. 3. The tuning structure 4 and the further tuning structure 4′ also comprise a second electrical contact 8, which is arranged on the rear surface 6 of the respective tuning structure 4, 4′ this means on a side of the tuning structure 4, 4′, which faces away from the viewer of FIG. 3. In FIG. 3 the second electrical contact 8 is drawn by dashed lines to indicate that it can be arranged in the transversal direction z exactly under the first electrical contact 7, so that it is not visible from the viewer's perspective.
[0073] The first and the second electrical contact 7, 8 of the tuning structure 4 comprising the circumferential portion 18 are arranged in such way, that they reach from the circumferential portion 18 in a lateral direction y through the gap in the further circumferential portion 19 to a peripheral region of the optoelectronic device 1. The peripheral region of the optoelectronic device 1 refers to a region, where no optical structure is present above the tuning structure and which therefore is optically inactive.
[0074] The first and the second electrical contact 7, 8 of the further tuning structure 4′ comprising the further circumferential portion 19 reach from the further circumferential portion 19 in an arbitrary lateral direction x, y to the peripheral region. Due to this arrangement the first and the second electrical contact 7, 8 of each tuning structure 4, 4′ are accessible and can be connected to the voltage source 15 (not shown) at the peripheral region of the optoelectronic device 1.
[0075] The embodiment shown in FIG. 3 comprises an optical structure 12 comprising structural elements 13, which have a round shape in top-view. In top-view, the overall area covered by the optical structure 12 approximately corresponds to the area enclosed in lateral directions x, y by the circumferential portion 18 and the further circumferential portion 19. This area can be referred to as the optically active area.
[0076] In the embodiment shown in FIG. 3 the optical structure 12 can be provided to form a tunable meta-lens, i.e. a lens comprising a meta-material. The meta-lens has a diameter corresponding to the optically active area. The tuning structure 4 and the further tuning structure 4′ introduce corrections in the phase function already implemented by the meta-lens. The electrical contacts 7, 8 of each tuning structure 4, 4′ are separately arranged, so that the respective tuning structures 4, 4′ can be controlled by an electric field independently. This way different phase delays can be achieved along the lens diameter as required.
[0077] The embodiment of the optoelectronic device shown in FIG. 4 comprises a substrate 2 and a cover layer 10 with rectangular shapes in top-view. It further differs from the embodiment of FIG. 3 in that is comprises a plurality of tuning structures 4, which are arranged as an array. In this case the array comprises six tuning structures 4. In FIG. 4 only the first electrical contact 7 of each tuning structure 4 is shown. However, the second electrical contact 8 (not shown) can be arranged directly under the first electrical contact 7, so that it is not visible from the viewer's perspective. The electrical contacts 7, 8 are extending from the respective tuning structure 4 in lateral directions x, y towards different peripheral regions of the optoelectronic device 1. This way, they can be connected separately to one or more voltage sources 15 (not shown). This in turn allows to control the electric field in each tuning structure 4 independently.
[0078] The optical structure 12 is arranged in the transversal direction z above the array of tuning structures 4. The area which is covered by the optical structure 12 comprising the structural elements 13 in lateral directions x, y, can be approximately as large as the area covered be the array of tuning structures 4. However, as shown in FIG. 4, the overall area covered by the array of tuning structures 4 can be slightly larger than the area covered by the optical structure 12. The overlapping region of both areas can be referred to as the optically active area.
[0079] The embodiment of the optoelectronic device 1 shown in FIG. 5 differs from the embodiment shown in FIG. 1 in that it shows a different optical structure 12. The optical structure 12 of FIG. 5 also comprises a structured surface 21 facing away from the cover layer 10. However, the structural elements 13 are physically connected to each other since the recesses 14 do not extend over the entire thickness of the optical structure 12. Therefore portions of the top surface 11 of the cover layer 10 are not exposed in the area, where the optical structure 12 is present. This means that the cover layer 10 is completely covered by the optical structure 12. The structured surface 21 forms a pattern, which can be regular or irregular. The structural elements 13 can comprise shapes according to FIGS. 2a-d. In another embodiment the structural elements 13 form concentric rings over the optically active area. In this case, the optical structure 12 forms a zone plate or a binary lens.
[0080] FIG. 5 differs further from FIG. 1 in that it shows a different concept for electrically contacting the at least one tuning structure 4. In this case, each tuning structure 4 has the first electrical contact 7 and the second electrical contact 8 arranged on a side surface 9 or, respectively, on a further side surface 9′ of the tuning structure 4. The side surface 9 and the further side surface 9′ run perpendicular or transverse with respect to the main plane of extension of the substrate 2. The side surface 9, where the first electrical contact 7 is arranged, is separated from the further side surface 9′, where the second electrical contact is arranged. This way, the first and the second electrical contacts 7, 8 are electrically isolated from each other. As shown in FIG. 5, the first and the second electrical contact 7, 8 can cover the whole respective side surface 9, 9′ of the tuning structure 4.
[0081] The embodiment of the optoelectronic device 1 shown in FIG. 6 differs from the embodiment shown in FIG. 5 in that it shows another variation of the optical structure 12. In this case the optical structure 12 forms a layer with a flat surface 21. This means that the surface 21 of the optical structure 12, which faces away from the cover layer 10, runs parallel to the main plane of extension of the substrate 2. This embodiment of the optical structure 12 can be used, if the optical structure 12 forms a phase plate or a diffusor.
[0082] The embodiment of the optoelectronic device 1 shown in FIG. 7 differs from the embodiment shown in FIG. 6 in that it shows another variation of the optical structure 12. In this case the optical structure 12 has a curved surface 21. This means that the surface 21 of the optical structure 12, which faces away from the cover layer 10, exhibits a curvature with respect to the main plane of extension of the substrate 2. This embodiment of the optical structure 12 can be used, if the optical structure 12 forms a refractive lens.
[0083] FIG. 8 shows a graph of functions obtained by simulation. Here, an intensity I of the electromagnetic radiation is plotted against a distance d between the optical structure 12 and a position in the transversal direction z above the optical structure 12. The intensity I is given in units of W/m.sup.2. The distance d is given in units of μm.
[0084] In this case the optical structure 12 forms a lens as for example discussed in conjunction with FIG. 3. The result of the simulation can be used for finding the focal length of the optical structure 12 forming the lens. It should however be noted that any other target specification of the optical structure 12 can be analyzed in a similar way.
[0085] The intensity characteristics are shown for three different scenarios: The first scenario (curve 22) shows the intensity I of the electromagnetic radiation while no electric field is applied on the tuning structure 4. The second and third scenario (curves 23 and 24) show the intensity I of the electromagnetic radiation while a respective electric field is applied on the tuning structure 4. Curve 22 shows a clear maximum at about 35 μm. This means that the focal length of the optical structure 12 can be identified with this distance. The simulation result also shows that the optoelectronic device 1 exhibits via the optical structure 12 a target specification even without tuning, i.e. in a mode of operation, which is not a tuning mode by applying an electric field. However, by applying an electric field of a specific strength and direction the intensity maximum is shifted towards a distance d of about 45 μm (curve 23). Moreover, by applying a different electric field as shown by curve 24, the intensity maximum can be shifted in the opposite direction, i.e. to a distance d of about 25 μm. This means that the optical characteristics of the optoelectronic device 1 can be changed dynamically in either direction by applying a respective electric field.
[0086] The embodiments of the optoelectronic device 1 disclosed herein have been discussed for the purpose of familiarizing the reader with novel aspects of the idea. Although preferred embodiments have been shown and described, many changes, modifications, equivalents and substitutions of the disclosed concepts may be made by one having skill in the art without unnecessarily departing from the scope of the claims.
[0087] It will be appreciated that the disclosure is not limited to the disclosed embodiments and to what has been particularly shown and described hereinabove. Rather, features recited in separate dependent claims or in the description may advantageously be combined. Furthermore, the scope of the disclosure includes those variations and modifications, which will be apparent to those skilled in the art and fall within the scope of the appended claims.
[0088] The term “comprising”, insofar it was used in the claims or in the description, does not exclude other elements or steps of a corresponding feature or procedure. In case that the terms “a” or “an” were used in conjunction with features, they do not exclude a plurality of such features. Moreover, any reference signs in the claims should not be construed as limiting the scope.
