Mode conversion waveguide system

Abstract

To provide a method for converting the mode of light and a mode conversion waveguide system.SOLUTION: Light is sent through a single-mode waveguide. In that case, the light has a first mode while moving through the single-mode waveguide. The light is sent from the single-mode waveguide to a multi-mode interface region connected to the single-mode waveguide. The light is reflected in the hollow of the multi-mode interface region in a manner which propagates the light to a direction away from the single-mode waveguide. The light is output from the multi-mode interface region. In that case, the light has a second mode.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure generally relates to optical waveguide structures and, in particular, to mode conversion waveguide systems.

Background Art

[0002] An optical waveguide is a physical structure that guides electromagnetic waves within the optical spectrum. These optical waveguides can be used as components within an integrated optical circuit. With respect to quantum communication and processing, optical material structures can be used to fabricate photonic transmitters, repeaters, and other quantum devices for communication.

[0003] An optical waveguide can perform mode conversion that can change the electric field pattern of the propagating wave. Mode conversion optical waveguides can be used for various applications. For example, mode conversion can be implemented within an optical waveguide to perform multiplexing or demultiplexing of optical signals.

[0004] In a mode division multiplexing scheme, optical signals of a single carrier wave wavelength are independently carried by various optical modes within one multimode waveguide bus. In addition, nonlinear optical processes within the waveguide such as parametric down conversion, spontaneous four-wave mixing, second harmonic generation, etc., often use higher order modes in the nonlinear optical process. These nonlinear optical processes can be used to fabricate, for example, heralded single photon sources, entangled photon sources, and optical parametric oscillators.

[0005] Optical waveguides that perform mode conversion of optical signals often include losses during mode conversion. As a result, the efficiency of conversion of light from one mode to another in these optical waveguides may be undesirable or not practical. These losses may be undesirable or not practical for the desired application.

[0006] Therefore, it would be desirable to have methods and apparatus that take into account at least some of the above-mentioned problems, as well as other potential problems. For example, it would be desirable to have methods and apparatus that overcome technical problems by performing optical signal mode conversion with increased efficiency. [Overview of the project]

[0007] One embodiment of the present disclosure provides a mode-converting waveguide system including a single-mode waveguide, a multimode waveguide, a multimode interference region connected to the single-mode waveguide and the multimode waveguide, and a cavity within the multimode interference region.

[0008] According to another exemplary embodiment, a method for converting the mode of light is provided. Light is transmitted through a single-mode waveguide. In this case, the light has a first mode while traveling through the single-mode waveguide. The light is transmitted from the single-mode waveguide into a multimode interference region connected to the single-mode waveguide. The light is reflected by a cavity in the multimode interference region in such a way that the light propagates away from the single-mode waveguide. The light is output from the multimode interference region. In this case, the light has a second mode.

[0009] These features and functions may be realized individually in various embodiments of this disclosure, or they may be combined in yet another embodiment, which can be understood in more detail by referring to the following description and drawings.

[0010] Novel features that may be considered characteristics of exemplary embodiments are specified in the appended claims. However, exemplary embodiments, preferred modes of use, further purposes, and their characteristics will be best understood by reading the following detailed description of exemplary embodiments of this disclosure with reference to the accompanying drawings. [Brief explanation of the drawing]

[0011] [Figure 1]This is an example block diagram of a mode-converting waveguide system according to one exemplary embodiment. [Figure 2] This is an illustrative block diagram of a cavity in a multimode interference region according to one exemplary embodiment. [Figure 3] This is an example block diagram of a multimode waveguide according to one exemplary embodiment. [Figure 4] This is a diagram of a mode-converting waveguide system according to an exemplary embodiment. [Figure 5] This is a cross-sectional view of a multimode waveguide according to an exemplary embodiment. [Figure 6] This is a cross-sectional view of a multimode interference region according to an exemplary embodiment. [Figure 7] This is a cross-sectional view of a mode-converting waveguide system according to an exemplary embodiment. [Figure 8] This is another diagram of a mode-converting waveguide system according to an exemplary embodiment. [Figure 9] This is a cross-sectional view of a multimode interference region according to an exemplary embodiment. [Figure 10] This is a cross-sectional view of a mode-converting waveguide system according to an exemplary embodiment. [Figure 11] This is yet another diagram of a mode-converting waveguide system according to an exemplary embodiment. [Figure 12] This is a cross-sectional view of a multimode interference region according to an exemplary embodiment. [Figure 13] This is a cross-sectional view of a mode-converting waveguide system according to an exemplary embodiment. [Figure 14] This is a cross-sectional view of a multimode waveguide according to an exemplary embodiment. [Figure 15] This is a diagram of a transverse electric (TE) mode that may exist in a mode-converting waveguide system according to an exemplary embodiment. [Figure 16] This is a diagram of a transverse magnetic (TM) mode that may exist in a mode-converting waveguide system according to an exemplary embodiment. [Figure 17]This is an example graph illustrating the electric field profile according to one exemplary embodiment. [Figure 18] This is another example of a graph illustrating the electric field profile according to one exemplary embodiment. [Figure 19] This is an illustrative flowchart of a process for converting the mode of light according to an exemplary embodiment. [Figure 20] This is an illustrative flowchart of a process for converting the mode of light according to an exemplary embodiment. [Figure 21] This is an example block diagram of a product management system according to one exemplary embodiment. [Modes for carrying out the invention]

[0012] The exemplary embodiments recognize and consider one or more different considerations. For example, the exemplary embodiments recognize and consider that optical waveguides used for mode conversion may have undesirable losses based on changes in the effective refractive index of the modes. The embodiments recognize and consider that some mode conversion optical waveguides use directional couplers that require the effective refractive index of the modes in question to be properly matched. The exemplary embodiments recognize and consider that changes in refractive index may cause uneven changes in the effective refractive index of the modes in question.

[0013] The exemplary embodiment recognizes and considers that current designs for mode-converting optical waveguides recognize and consider that variations in the manufacturing process and design can result in varying efficiencies when the shape dimensions and refractive index change. For example, materials used in mode-converting optical waveguides may have refractive indices that cannot be precisely controlled as desired. One example of a material for which controlling the refractive index can be difficult when manufacturing mode-converting optical waveguides is silicon nitride. The exemplary embodiment recognizes and considers that the formation and subsequent processing of silicon nitride films can result in changes in refractive index. The exemplary embodiment recognizes and considers that the chemical composition of the film can be changed by selecting the deposition time, deposition temperature, pressure, reactant flow rate, and substrate temperature during manufacturing, which affects the physical properties of the film, such as the refractive index.

[0014] Accordingly, exemplary embodiments provide methods, apparatus, and systems for mode conversion that allow for changes in refractive index. Detailed embodiments of the claimed structures and methods for optical waveguides are disclosed herein. However, it should be understood that the disclosed embodiments are merely illustrative of the claimed structures and methods, which may be embodied in various forms. In addition, each of the embodiments given in relation to the various embodiments is intended to be illustrative and not limiting.

[0015] Furthermore, the drawings are not necessarily to scale, and some features may be exaggerated to illustrate the details of certain components. Therefore, the specific structures and functions disclosed herein should not be construed as limiting, but merely as representative foundations to instruct those skilled in the art on various ways of employing the methods and structures disclosed herein.

[0016] For illustrative purposes, the terms “upper,” “lower,” “right,” “left,” “vertical,” “horizontal,” “up,” and “down,” and their derivatives, hereafter as they relate to embodiments of the present disclosure, as oriented in the drawings. The term “placed on” means that a first element, such as a first structure, is located on a second element, such as a second structure. In this case, an intervening element, such as an interface structure (e.g., an interface layer), may be located between the first and second elements.

[0017] The exemplary embodiment recognizes and considers the variation between the refractive index of the material and the refractive index for the modes of electromagnetic waves propagating through the material. This variation can lead to an undesirable decrease in the amount of mode conversion and transmission. The exemplary embodiment recognizes and considers the desirability of having an optical waveguide system with improved tolerance to changes in refractive index.

[0018] In this disclosure, when an element such as a layer, region, or substrate is referred to as being "on" or "on top of" another element, that element may be directly on top of the other element, or an intervening element may be present. In contrast, when an element is referred to as being "directly on," "directly above," or "on top of and in direct contact" another element, there is no intervening element, and the element is in contact with that other element.

[0019] The processes, steps, and structures described below do not constitute a complete process flow for manufacturing optical waveguides or integrated circuits. This disclosure can be implemented in conjunction with optical waveguides for semiconductor circuits currently in use in the art, and includes only some of the commonly implemented process steps, depending on the need for understanding the various embodiments of this disclosure. Drawings showing cross-sectional views of parts of integrated circuits under manufacture are not drawn to scale, but rather to illustrate various exemplary features of this disclosure.

[0020] Next, referring to the drawings, in particular Figure 1, an illustrative block diagram of a mode-converting waveguide system according to an exemplary embodiment is shown. As shown, the mode-converting waveguide system 100 includes a single-mode waveguide 102, a multimode interference region 104, and a multimode waveguide 106. In this exemplary embodiment, the multimode interference region 104 connects the single-mode waveguide 102 and the multimode waveguide 106. In this exemplary embodiment, the single-mode waveguide 102, the multimode waveguide 106, and the multimode interference region 104 are formed on a substrate 108. The substrate 108 can take several different forms. For example, the substrate 108 may be silicon dioxide (SiO2), silicon nitride (Si x N y (x and y are stoichiometric ratios), silicon hydride nitride (Si x N y :H z ), silicon oxynitride (SiO x N y ), aluminum nitride (AlN), silicon carbide (SiC), lithium niobate (LiNbO3), aluminum gallium arsenide (Al xGa1- x As), silicon (Si), and other suitable materials, may be selected from the group consisting of.

[0021] As depicted, the single-mode waveguide 102 is optically coupled to the multimode interference region 104. The multimode interference region 104 is optically connected to the multimode waveguide 106. Further, the mode conversion waveguide system 100 includes a cavity 118 positioned within the multimode interference region 104.

[0022] In this exemplary embodiment, electromagnetic energy 120 may move or propagate through the mode conversion waveguide system 100. This propagation of electromagnetic energy 120 through the mode conversion waveguide system 100 may change the mode 122 of the field 124 of the electromagnetic energy 120. In this exemplary embodiment, the field 124 may be at least one of an electric field 123 or a magnetic field 125.

[0023] As used herein, the phrase "at least one of" used with the listed items means that various combinations of one or more of the listed items may be used, and only one of each of the listed items may be required. In other words, "at least one of" means any combination of items, and that some items may be used from the list, but not all of the listed items are necessarily required. An item may be a particular object, article, or category.

[0024] For example, though not limited, “at least one of item A, item B, and item C” could include item A, item A and item B, or item B. This example could also include item A, item B, and item C, or item B and item C. Needless to say, any combination of these items is possible. In an exemplary embodiment, “at least one of ~” could, but not limited to, for example, “two item A, one item B, and ten item C,” “four item B and seven item C,” or any other suitable combination.

[0025] In an exemplary embodiment, the electromagnetic energy 120 traveling through the mode-converting waveguide system 100 is light 130 in this exemplary embodiment. The cavity 118 within the multimode interference region 104 reflects the light 130 having a first mode 132 traveling from the single-mode waveguide 102 into the multimode interference region 104 in such a way that the light 130 has a second mode 134.

[0026] In this exemplary embodiment, depending on the shape and dimensions of the structure within the mode-converting waveguide system 100, a single guided TE or TM optical mode or two or more guided TE optical modes may be supported. For example, a single-mode waveguide 102 may support a single TE or TM mode, while a multi-mode waveguide 106 may support a set of TE or TM optical modes.

[0027] In these embodiments, the TE (transverse electric) mode means that the electric field component of the guided mode is polarized in the plane of the substrate. The TM (transverse magnetic) mode means that the magnetic field is polarized in the plane of the substrate, or equivalently, the electric field is polarized perpendicular to the plane of the substrate. In an exemplary embodiment, the basic TE of the waveguide 11 and TM 11Modes have a single peak in the electric field profile of the derived mode, while modes of a higher order have two or more peaks in their electric field profile.

[0028] In this exemplary embodiment, light 130 has a first mode 132 as it travels through a single-mode waveguide 102. In the single-mode waveguide 102, the first mode 132 of light 130 may be the fundamental mode of light 130. The multimode interference region 104 changes light 130 from the first mode 132 to a second mode 134. Light 130 having the second mode 134 is output from the multimode interference region 104 to the multimode waveguide 106.

[0029] In this exemplary embodiment, the cavity 118 reflects light 130, such as light of a basic mode, as it travels through the multimode interference region 104, within the multimode interference region 104. The cavity 118 disturbs or alters the field 124 of the light 130 entering the multimode interference region 104, thereby changing the mode 114 of the light 130 from a first mode 132 to a second mode 134 when the light exits the multimode interference region 104.

[0030] For example, light 130 travels in a first direction 136 through a mode-converting waveguide system 100. This converts the light 130 from a lower mode to a higher mode. The light 130, having the first mode 132, travels through a single-mode waveguide 102, enters a multimode interference region 104, and exits the multimode interference region 104 into a multimode waveguide 106 in a second mode 134.

[0031] Further light in other modes can be introduced into the multimode waveguide 106, such that light 130 has a second mode 134. For example, light 130 in the second mode 134 is TE 31 It may have modes, and further light, ™ 31 It may have modes.

[0032] In this embodiment, the first mode 132 is TE 11 In light mode, the second mode 134 is TE 31 It may be a light mode. In another embodiment, the first mode 132 is TM 11 In light mode, the second mode 134 is TM 31 It could be in light mode.

[0033] In another exemplary embodiment, light 130 input to a mode-converting waveguide system 100 is in a higher-order mode and is input into a multimode waveguide 106. In this exemplary embodiment, light 130 travels through the mode-converting waveguide system 100 in a second direction 138, thereby converting light 130 to a lower-order mode. Light 130 having the second mode 134 travels through the multimode waveguide and is input into a multimode interference region 104, and is output from the multimode interference region 104 into a single-mode waveguide in the first mode 132.

[0034] In this embodiment, the single-mode waveguide 102 allows only lower-order mode light 130 to pass through, while blocking higher-order mode light 130. As a result, the single-mode waveguide 102 can function as a filter to filter out anything that has not been converted to a lower or more fundamental mode.

[0035] In this embodiment, the first mode 132 is TE 11 In light mode, the second mode 134 is TE 31 It may be a light mode. The first mode 132 is TM 11 In light mode, the second mode 134 is TM 31 It could be in light mode.

[0036] Next, referring to Figure 2, an example block diagram of a cavity in a multimode interference region according to an exemplary embodiment is depicted. In the exemplary embodiment, the same reference numerals may be used in multiple figures. When reference numerals are used repeatedly in different figures, they represent the same element in the different figures.

[0037] In this exemplary embodiment, the cavity 118 within the multimode interference region 104 has a shape 200 and a position 201. In one exemplary embodiment, the shape 200 and position 201 may be selected to provide symmetry within the multimode interference region 104. This symmetry may improve at least one of the tolerance for performance bandwidth or refractive index changes in the optical waveguide within the mode-conversion waveguide system 100.

[0038] The shape 200 and position 201 may be selected such that the cavity 118 within the multimode interference region 104 reflects the light 130 so that the light 130 propagates in the direction of motion. For example, if the light 130 is input into a single-mode waveguide 102, the cavity 118 moves the light 130 away from the single-mode waveguide 102. In another embodiment, if the light 130 is input into a multimode waveguide 106, the cavity 118 moves the light 130 away from the multimode waveguide 106. In other words, the cavity 118 reduces the reflection of the light 130 that moves it in the opposite direction to the direction of propagation when the light 130 is input into the multimode interference region 104.

[0039] Shape 200 can take several different forms. For example, shape 200 can be selected from one of the following: a cylinder, an ellipsoid, a pyramid, a cone, a sphere, a frustum, a frustum of a cone, a pyramidal frustum, a geometric shape symmetric with respect to plane 205 with respect to the multimode interference region, and one of other suitable shapes. In this embodiment, plane 205 is an xz plane such as the xz plane 702 in Figure 7 below.

[0040] In this exemplary embodiment, the multimode interference region 104 is symmetric with respect to an axis 202 extending centrally through the multimode interference region 104. In another embodiment, the multimode interference region 104 is symmetric with respect to a plane 205 with respect to the multimode interference region 104. For example, the multimode interference region 104 may be symmetric with respect to an xz plane that bisects the lower width 207 of the multimode interference region 104. In one embodiment, the shape 203 of the multimode interference region 104 is symmetric with respect to a plane or axis extending centrally through the multimode interference region 104. In this embodiment, the position 201 of the cavity 118 within the multimode interference region 104 is symmetric with respect to the plane 205. The position 201 is a three-dimensional position and can be described using a Cartesian coordinate system with XYZ values. The cavity 118 may be symmetric with respect to an axis 202 extending centrally through the multimode interference region 104.

[0041] Furthermore, the cavity 118 can take several different forms. For example, the cavity 118 may be either a void 204 or a hole 206 having shape 200. The void 204 is enclosed within the multimode interference region 104, while the hole 206 extends into the multimode interference region 104, and the hole 206 extends through the multimode interference region 104 and communicates with another component in the mode-converting waveguide system 100 outside the multimode interference region 104.

[0042] In an exemplary embodiment, the multimode interference region 104 is composed of a first material 208, and the cavity 118 is filled with a second material 210 different from the first material 208. In this exemplary embodiment, the second material 210 has a lower refractive index than the first material 208. In an exemplary embodiment, the second material 210 may be air, silicon oxide (SiO2), an insulator, or any other suitable material.

[0043] In one exemplary embodiment, the multimode interference region 104 may include cladding 212 and a core region 214 within the cladding 212. The core region is composed of a first material 208. In this embodiment, a cavity 118 is located within the core region 214 of the multimode interference region 104. In this embodiment, the second material 210 for the cavity 118 may be the same material as the cladding material 216 for the cladding 212.

[0044] Referring to Figure 3, an example block diagram of a multimode waveguide according to an exemplary embodiment is shown. The multimode waveguide 106 may have a taper 300. For example, the taper 300 of the multimode waveguide 106 may be such that the width 302 of the multimode waveguide 106 becomes narrower as it moves away from the connection point of the multimode waveguide 106 with the multimode interference region 104. In other words, the width 302 of the multimode waveguide 106 may taper so that the width 302 of the multimode waveguide 106 is wider at the connection point of the multimode waveguide 106 with the multimode interference region 104 than the width 302 of the multimode waveguide 106 at a point away from the connection point of the multimode interference region 104.

[0045] Furthermore, the multimode waveguide 106 may include a first section 306 and a second section 308. In this embodiment, the first section 306 is connected to the multimode interference region, and the second section is connected to the first section 306. In this exemplary embodiment, the first section 306 has a first cross-section 310, and the second section 140 has a second cross-section 312 that is different from the first cross-section 142.

[0046] In an exemplary embodiment, a first cross-section 310 within a first section 306 may consist of a region 314 made of silicon nitride. A second cross-section 312 within a second section 308 may consist of a central region 316 of lithium niobate located between a first lateral region 318 and a second lateral region 320 of silicon nitride. The central region 316 may be located between the first lateral region 318 and the second lateral region 320. Multiple sections may be located within a cladding 212.

[0047] In an exemplary embodiment, the mode-converting waveguide system 100 provides improved performance compared to current mode-converting waveguide systems. As depicted, light 130 can be input into either the desired single-mode waveguide or the multimode waveguide 106. When input into the single-mode waveguide 102, light 130 is in single mode and outputs in multimode in the multimode waveguide 106. When input into the multimode waveguide 106, light 130 is in any multimode and outputs in single mode in the desired single-mode waveguide.

[0048] Therefore, as depicted, mode-converting waveguide system 100 uses a 1x1 mode-converting system that provides mode conversion between higher-order modes and lower-order modes of light 130 using a single single-mode waveguide, a single multi-mode interference region, and a single multi-mode waveguide. In contrast to mode-converting waveguide system 100, which uses multiple input waveguides, multiple multi-mode interference regions, multiple output waveguides, or a combination thereof, mode-converting waveguide system 100 uses only one input waveguide and one output waveguide.

[0049] In an exemplary embodiment, the mode-conversion waveguide system 100 allows for changes in the refractive index of the waveguide. This feature can provide a technical benefit in mitigating the problem of using materials in the waveguide with refractive indices that are difficult to precisely control. In this embodiment, the change in refractive index does not disrupt symmetry. As a result, the resulting changes are balanced in the mode-conversion waveguide system 100. Also, because the input and output modes are symmetrical, the efficiency of the mode-conversion process does not change dramatically.

[0050] Current mode conversion systems lack symmetry. As a result, the effect of uniformly distributing changes in refractive index is absent, leading to a reduction in mode conversion efficiency. Various parts of current mode conversion systems can change by slightly different amounts. This disrupts the system in undesirable ways. For example, in a directional coupler mode converter, a change in the refractive index of the material changes the effective refractive index of each mode in the waveguide by different amounts. This change causes the effective refractive indexes of the modes to no longer be equal, reducing mode conversion efficiency.

[0051] The refractive index of the materials in the entire mode conversion system may not exactly match the value specified in the design. In the waveguide's effective refractive index, the effect of changes in the material's refractive index on the effective refractive index can be large or small depending on the geometric shape.

[0052] Furthermore, the design of the mode-converting waveguide system 100 is easier to manufacture compared to current mode converters such as directional couplers. The mode-converting waveguide system 100 can be manufactured using a minimum feature size of approximately 120 nm, while other mode converters currently in use have a minimum feature size of 37 nm. Moreover, the mode-converting waveguide system 100 can be manufactured with a coupling length shorter than 10 μm, while directional couplers currently used in mode conversion can have coupling lengths exceeding 50 μm.

[0053] Next, referring to Figure 4, an example of a mode-converting waveguide system according to an exemplary embodiment is depicted. As depicted, the mode-converting waveguide system 400 is an embodiment of the mode-converting waveguide system 100 shown in block form in Figure 1. The mode-converting waveguide system 400 is achieved through the selection of dimensions for various components within the mode-converting waveguide system 400. 11 and TE 31 Modes and TM 11 and TM 31 It can be configured to perform mode conversion between modes. In this exemplary embodiment, the dimensions provided for this exemplary embodiment are TE 11 and TE 31 These can be used to perform mode conversion between modes. Using these exemplary dimensions, the modes of light with a wavelength of 655 nm can be converted.

[0054] As depicted, the mode-converting waveguide system 400 is shown in a top view on the xy-plane 402 defined by the y-axis 442 and the x-axis 444. In this exemplary embodiment, the mode-converting waveguide system 400 includes a single-mode waveguide 404, a multimode interference region 406, and a multimode waveguide 408. In this exemplary embodiment, the multimode interference region 406 has a cavity 410.

[0055] In this exemplary embodiment, these different components are situated within a confinement structure 412, which takes the form of cladding 414. The confinement structure 412 consists of one or more layers with a lower refractive index compared to the other structures, causing internal reflection of light within the single-mode waveguide 404, the multimode interference region 406, and the multimode waveguide 408.

[0056] In this exemplary embodiment, the cladding 414 may be composed of one or more materials. For example, the cladding 414 may be selected from at least one of air and silicon oxide (SiO2).

[0057] As depicted, the cavity 410 may optionally be filled with the same material as the cladding 414. In this exemplary embodiment, as light travels through the mode-converting waveguide system 400 in direction 416, the cavity 410 is configured to promote or cause reflection of light in direction 416 and reduce reflection of light in direction 418. For example, with respect to light traveling through the single-mode waveguide 404 in direction 416, the cavity 410 causes the light to travel within the multimode interference region 406 so that the light propagates away from the single-mode waveguide 404.

[0058] In other words, by using the cavity 410 and its configuration, the reflection of light in direction 418 can be reduced. As a result, an improvement in the efficiency or transmission of light, and the conversion of light from basic modes to higher-order modes, occurs in direction 416 through the use of the cavity 410.

[0059] Furthermore, light traveling in direction 418 through the mode-converting waveguide system 400 can be converted from higher-order modes to lower-order modes such as fundamental optical modes. The use of a cavity 410 within the multimode interference region 406 for light traveling in direction 418 can also improve the efficiency in converting light having higher-order modes when received from the multimode waveguide 408 to lower-order modes that can be transmitted through the single-mode waveguide 404.

[0060] As depicted, the multimode waveguide 408 has a taper 420 within section 422 of the multimode waveguide 408. The taper 420 may help reduce the loss of light traveling within the multimode waveguide 408. The taper 420 is an optional feature.

[0061] TE 11 Basic light modes and TE 31The dimensions for the mode-conversion waveguide system 400, which converts between optical modes, can take several different forms. In this exemplary embodiment, the single-mode waveguide 404 has a lower width 424 of approximately 318 nm.

[0062] In one exemplary embodiment, the lower width is the width of the lower part of the optical waveguide. The lower portion of the optical waveguide may be slightly wider than the upper part of the optical waveguide. For example, the optical waveguide may have inclined or curved side walls such that the lower width of the optical waveguide is wider than the upper width.

[0063] The multimode interference region 406 has a width 426 of 1.82 μm and a length 428 of 4.84 μm. The cavity 410 is a cylinder 429 with a radius 430 of 124 nm. As depicted, the distance 434 from the input to the multimode interference region 406 to the center 432 of the cavity is 1.67 μm.

[0064] As depicted, the multimode waveguide 408 has a lower width 438 of 1.32 μm. As can be seen, the multimode interference region 406 has a first width of lower width 426, which is wider than the second width of the multimode waveguide 106, which is lower width 438.

[0065] In this exemplary embodiment, the taper 420 of the multimode waveguide 408 tapers over a distance of 10 μm 440 from a lower width 438 of 1.32 μm to a lower width 436 of 933 nm. In this exemplary embodiment, the centers of the single-mode waveguide 404, the multimode interference region 406, the multimode waveguide 408, and the cavity 410 are aligned with respect to each other with respect to the y-axis 442.

[0066] In this exemplary embodiment, the heights of the single-mode waveguide 404, the multimode interference region 406, and the multimode waveguide 408 within the mode-converting waveguide system 400 are 300 nm with respect to the z-axis (not shown). The z-axis is perpendicular to the xy-plane 402.

[0067] Next, referring to Figure 5, a cross-sectional view of a multimode waveguide according to an exemplary embodiment is shown. In this exemplary embodiment, cross-section 500 is a cross-sectional view of the multimode waveguide 408 cut along line 5-5 in Figure 4. As shown, cross-section 500 lies on the YZ plane 502 defined by the y-axis 442 and the z-axis 504.

[0068] In this exemplary embodiment, the multimode waveguide 408 is comprised of a core region 506 and cladding 414. The core region 506 is the portion of the multimode waveguide 408 on which the optical signal travels in this exemplary embodiment. In this exemplary embodiment, the core region 506 is made of silicon nitride (SiN).

[0069] As depicted, cladding 414 consists of two sections: lower cladding 508 and upper cladding 510. Lower cladding 508 is composed of a layer of silicon dioxide (SiO2), and upper cladding 510 is composed of air.

[0070] In this exemplary embodiment, the core region has a lower width of 436 nm with a bottom width of 933 nm and a height of 514 nm with a height of 300 nm. The side walls 516 and 518 have an inclination angle of 80 degrees.

[0071] Next, referring to Figure 6, a cross-sectional view of a multimode interference region according to an exemplary embodiment is shown. In this exemplary embodiment, cross-section 600 is a cross-sectional view of the multimode interference region 406 cut along line 6-6 in Figure 4. As shown, cross-section 600 lies on the YZ plane 502 defined by the y-axis 442 and the z-axis 504.

[0072] In this exemplary embodiment, the multimode interference region 406 is comprised of a core region 602 and cladding 414. The core region 602 is the portion of the multimode interference region 406 through which the optical signal travels in this exemplary embodiment. In this exemplary embodiment, the core region 602 is made of silicon nitride (SiN). The core region 602 has a bottom width of 1.82 μm 426 and a height of 300 nm 514.

[0073] As depicted, the cavity 410 communicates with the upper cladding 510 and the lower cladding 508 and takes the form of a cylinder 429 having a height 514 that extends from the upper cladding 510, which is made of air, to the lower cladding 508, which is made of silicon oxide (SiO2). The cylinder 429 has a radius 430 of 124 nm.

[0074] Referring to Figure 7, a cross-sectional view of a mode-converting waveguide system according to an exemplary embodiment is shown. In this exemplary embodiment, cross-section 700 is a cross-sectional view of a portion of the mode-converting waveguide system 400 cut along line 7-7 in Figure 4. As shown, cross-section 700 lies on the XZ plane 702 defined by the x-axis 444 and the z-axis 504.

[0075] As shown, portions of the single-mode waveguide 404 and the multimode waveguide 408 are visible on either side of the multimode interference region 406 in this cross-sectional view. As shown, the cylinder 429 is illustrated within the multimode interference region 406.

[0076] Various dimensions for the mode-converting waveguide system 400 can be modified to constitute a mode-converting waveguide system 400 for performing other types of conversions. Furthermore, the configuration of the cylinder 429 can be modified. For example, in another exemplary embodiment, the cylinder 429 does not have to extend through the entirety of the multimode interference region 406.

[0077] As depicted, the multimode interference region 406 is symmetric with respect to the XZ plane 702. In one exemplary embodiment, the XZ plane 702 may be defined so as to bisect the multimode interference region 406. In other words, the xz plane 702 may extend through the midpoint of the lower width 426 of the multimode interference region 406. In this exemplary embodiment, the symmetry is the dimensions and features of the multimode interference region 406. These features may include a cylinder 429. In other words, the cylinder 429 may be symmetrically positioned so as to bisect the xz plane 702. Furthermore, the symmetry of the multimode interference region 406 may also be with respect to an axis extending through the multimode interference region 406 at its center.

[0078] Next, referring to Figure 8, another example of a mode-converting waveguide system according to an exemplary embodiment is depicted. As depicted, the mode-converting waveguide system 800 is an embodiment of the mode-converting waveguide system 100 shown in block form in Figure 1. The mode-converting waveguide system 800 is achieved through the selection of dimensions for various components within the mode-converting waveguide system 800, 11 and TE 31 Modes and TM 11 and TM 31 It may be configured to perform mode conversion between modes. 11 and TM 31 Exemplary dimensions may be used for mode conversion between modes.

[0079] As depicted, the mode-converting waveguide system 800 is shown in a top view on the xy-plane 802 defined by the y-axis 804 and the x-axis 806. In this exemplary embodiment, the mode-converting waveguide system 800 includes a single-mode waveguide 808, a multimode interference region 810, and a multimode waveguide 812. In this exemplary embodiment, the multimode interference region 810 has a cavity 814 that takes the form of an ellipsoid 816.

[0080] In this exemplary embodiment, the ellipsoid 816 has a minor axis 818 of 30 nm and a major axis 820 of 600 nm. As depicted, the ellipsoid 816 is located at a distance 822 of 2.17 μm from the single-mode waveguide 808.

[0081] As depicted, the single-mode waveguide 808 has a lower width 824 of 318 nm. The multimode interference region 810 has a lower width 826 of 2.01 μm and a length 828 of 6.74 μm. The multimode waveguide 812 has a lower width 830 of 1.32 μm that tapers to a lower width 832 of 1.32 μm over a distance 834 of 10 μm.

[0082] In this embodiment, the centers of the single-mode waveguide 808, the multimode interference region 810, the multimode waveguide 812, and the cavity 814 are aligned with respect to each other with respect to the y-axis 804. The height of these components is 300 nm in the z-axis direction in this depicted embodiment.

[0083] Next, referring to Figure 9, a cross-sectional view of a multimode interference region according to an exemplary embodiment is shown. In this exemplary embodiment, cross-section 900 is a cross-sectional view of the multimode interference region 810 cut along line 9-9 in Figure 8. As shown, cross-section 900 lies on the YZ plane 902 defined by the y-axis 804 and the z-axis 906.

[0084] In this exemplary embodiment, the multimode interference region 810 is comprised of a core region 908 and cladding 910. In this exemplary embodiment, the core region 908 is made of silicon nitride (SiN). The core region 908 has a bottom width of 2.01 μm 826 and a height of 300 nm 912.

[0085] As depicted, the cavity 814 communicates with the upper cladding 914 and the lower cladding 916, and takes the form of an ellipsoid 816 extending from the upper cladding 914, which is composed of air, to the lower cladding 916, which is composed of silicon oxide (SiO2). The ellipsoid 816 has a minor axis 818 of 600 nm and a height 912.

[0086] Referring to Figure 10, a cross-sectional view of a mode-converting waveguide system according to an exemplary embodiment is shown. In this exemplary embodiment, cross-section 1000 is a cross-sectional view of a portion of the mode-converting waveguide system 800 cut along line 10-10 in Figure 8. As shown, cross-section 1000 lies on the XZ plane 1002 defined by the x-axis 806 and the z-axis 906.

[0087] As shown, portions of the single-mode waveguide 808 and the multimode waveguide 812 are visible on either side of the multimode interference region 810 in this cross-sectional view. As shown, the ellipsoid 816 is illustrated within the multimode interference region 810, having a major axis 820 of 600 nm.

[0088] Referring now to Figure 11, yet another example of a mode-converting waveguide system according to an exemplary embodiment is depicted. As depicted, the mode-converting waveguide system 1100 is an embodiment of the mode-converting waveguide system 100 shown in block form in Figure 1. The mode-converting waveguide system 1100 is achieved through the selection of dimensions for various components within the mode-converting waveguide system 800, 11 and TE 31 Modes and TM 11 and TM 31 It may be configured to perform mode conversion between modes. 11 Mode and TM 31 Exemplary dimensions may be used for mode conversion between modes.

[0089] As depicted, the mode-converting waveguide system 1100 is shown in a top view on the xy-plane 1102 defined by the y-axis 1104 and the x-axis 1106. In this exemplary embodiment, the mode-converting waveguide system 1100 includes a single-mode waveguide 1108, a multimode interference region 1110, and a multimode waveguide 1112. In this exemplary embodiment, the multimode interference region 1110 has a cavity 1114 that takes the form of a sphere 1116.

[0090] In this exemplary embodiment, the sphere 1116 has a radius 1118 of 150 nm. As depicted, the sphere 1116 is located at a distance 1120 of 2.17 μm from the single-mode waveguide 1108.

[0091] As depicted, the single-mode waveguide 1108 has a lower width 1122 of 318 nm. The multimode interference region 1108 has a lower width 1124 of 2.01 μm and a length 1126 of 6.74 μm. The multimode waveguide 1112 has a lower width 1128 of 1.32 μm that tapers to a lower width 1132 of 0.933 μm over a distance 1134 of 10 μm within region 1130.

[0092] In this embodiment, the centers of the single-mode waveguide 1108, the multimode interference region 1110, the multimode waveguide 1112, and the cavity 1114 are aligned with respect to each other with respect to the y-axis 1104. The height of these components is 300 nm in the z-axis direction in this depicted embodiment.

[0093] Next, referring to Figure 12, a cross-sectional view of a multimode interference region according to an exemplary embodiment is shown. In this exemplary embodiment, cross-section 1200 is a cross-sectional view of the multimode interference region 1110 cut along line 12-12 in Figure 11. As shown, cross-section 1200 lies on the YZ plane 1202 defined by the y-axis 1204 and the z-axis 1206.

[0094] In this exemplary embodiment, the multimode interference region 1110 is comprised of a core region 1208 and cladding 1210. In this exemplary embodiment, the core region 1208 is made of silicon nitride (SiN). The core region 1208 has a bottom width 1124 of 2.01 μm and a height 1211 of 300 nm.

[0095] The cladding 1210 is composed of an upper cladding 1212 and a lower cladding 1214. In this exemplary embodiment, the upper cladding 1212 is made of air and the lower cladding 1214 is made of silicon oxide (SiO2).

[0096] As depicted, the cavity 1114 is a sphere 1116 located within the core region 1208 and is not in communication with the upper cladding 1212 and the lower cladding 1214. As depicted, the sphere 1116 in this embodiment has a radius 1118 of 150 nm.

[0097] Referring to Figure 13, a cross-sectional view of a mode-converting waveguide system according to an exemplary embodiment is shown. In this exemplary embodiment, cross-section 1300 is a cross-sectional view of a portion of the mode-converting waveguide system 1100 cut along line 13-13 in Figure 11. As shown, cross-section 1300 lies on the XZ plane 1302 defined by the x-axis 1106 and the z-axis 1206.

[0098] As shown, portions of a single-mode waveguide 1108 and a multimode waveguide 1112 are visible on either side of the multimode interference region 1110 in this cross-sectional view. As shown, a cavity 1114 taking the form of a sphere 1116 with a radius 1118 of 150 nm is illustrated within the multimode interference region 1110.

[0099] The examples of mode-conversion waveguide systems in Figures 4 to 13 are provided as embodiments of the mode-conversion waveguide system 100 shown in block form in Figures 1 to 3. The various dimensions and configurations described provided as embodiments are not intended to limit the ways in which other exemplary embodiments may be implemented. For example, different components have asymmetries that contribute to improved tolerance to changes in bandwidth and refractive index. In the exemplary embodiments, the improvement in bandwidth results from increased coupling efficiency when changing the mode of the input optical signal.

[0100] In these embodiments, the symmetry of the cavity is described as aligning with respect to the y-axis with respect to other components. In other words, the cavity is described as being aligned with respect to an axis extending through the various components.

[0101] In yet another embodiment, various dimensions are used to obtain a desired mode conversion between TE or TM modes. In yet another exemplary embodiment, the multimode waveguides depicted in these drawings may not have a taper.

[0102] In yet another embodiment, the various waveguides within a mode-converting waveguide system may be composed of various materials. For example, a single-mode waveguide may consist of one material, a multimode interference region may consist of a second material, and a multimode waveguide may consist of a third material.

[0103] In another exemplary embodiment, other types of materials and combinations of materials may be used for cladding, besides the upper cladding being air, the lower cladding being silicon oxide, and the optical waveguide being silicon nitride. These embodiments do not preclude the use of other materials. For example, silicon, silicon carbide, lithium niobate, or other materials may be used for the core. In other exemplary embodiments, the upper cladding may be made of a material other than air. For example, silicon oxide, or other materials with a desired refractive index, may be used in addition to or instead of air. The refractive index of the material guiding the optical modes may affect the optimal shape and dimensions of the waveguide and the selection of dimensions in components such as the multimode interference region.

[0104] For example, Figure 14 shows a cross-sectional view of a multimode waveguide according to an exemplary embodiment. In this figure, the multimode waveguide uses a different type of material than the embodiments in Figures 4 to 13. As shown, the cross-section 1400 lies on the YZ plane 1402 defined by the y-axis 1404 and the z-axis 1406. This embodiment of the multimode waveguide 1408 is another exemplary configuration for a multimode waveguide that can be used in addition to or instead of the configuration illustrated for the multimode waveguide 408 in cross-section 500 of Figure 5.

[0105] In this exemplary embodiment, the multimode waveguide 1408 comprises a core region 1410 and cladding 1412. In this exemplary embodiment, the core region 1410 comprises a central region 1414, a first lateral region 1416, and a second lateral region 1418. The central region 1414 is located between the first lateral region 1416 and the second lateral region 1418. As depicted, the central region 1414 is composed of lithium niobate (LiNbO3), and the first lateral region 1416 and the second lateral region 1418 are composed of silicon nitride (SiN). In this embodiment, the cladding 1412 is composed of silicon oxide (SiO2).

[0106] Referring to Figure 15, an example of TE modes that may exist in a mode-converting waveguide system according to an exemplary embodiment is depicted. The graph 1500 shows various TE modes that may exist in mode-converting waveguide systems such as mode-converting waveguide system 100 in Figure 1, mode-converting waveguide system 400 in Figure 4, mode-converting waveguide system 800 in Figure 8, and mode-converting waveguide system 1100 in Figure 11.

[0107] Graph 1500 shows the electric field strength for specific optical modes within a waveguide 1502 made of silicon nitride. These modes are TE modes, where there are i electric field peaks in the y direction on the x-axis and j electric field peaks in the z direction on the x-axis. ij It is named according to the convention of expressing it as such.

[0108] As shown, Graph 1504 shows the TE for waveguide 1502, such as a single-mode waveguide. 11 This indicates mode 1506. TE 11 Mode 1506 is the basic mode in this embodiment and has a single maximal portion.

[0109] Graph 1508 shows the TE for waveguide 1503, such as multimode waveguides. 21 It depicts Mode 1510. TE 21 Mode 1510 has two maximal portions. In this exemplary embodiment, Graph 1512 shows the TE relative to waveguide 1503, such as a multimode waveguide. 31 It depicts Mode 1514. TE 31 Mode 1514 has three maximal parts. The modes in Graphs 1508 and 1512 are examples of modes that can be observed in a multimode waveguide.

[0110] Referring to Figure 16, an example of TM modes that may exist in a mode-converting waveguide system according to an exemplary embodiment is depicted. Graph 1600 illustrates various TM modes that may exist in mode-converting waveguide systems such as mode-converting waveguide system 100 in Figure 1, mode-converting waveguide system 400 in Figure 4, mode-converting waveguide system 800 in Figure 8, and mode-converting waveguide system 1100 in Figure 11.

[0111] Graph 1600 shows the magnetic field strength for specific optical modes within a waveguide 1502 made of silicon nitride. These modes are TM modes, where there are i magnetic field peaks in the y direction on the x-axis and j magnetic field peaks in the z direction on the x-axis for the waveguide. ij It is named according to the convention of expressing it as such.

[0112] As shown, Graph 1604 shows the TM for waveguide 1602, such as a single-mode waveguide. 11 This indicates mode 1606. ™ 11 Mode 1606 is the basic mode in this embodiment and has a single maximal portion.

[0113] Graph 1608 shows the TM for waveguide 1603, such as multimode waveguides. 21 It is drawing mode 1610. TM 21 Mode 1610 has two maximal portions. In this exemplary embodiment, Graph 1612 shows the TM relative to waveguide 1603, such as a multimode waveguide. 31 It depicts Mode 1614. TM 31 Mode 1614 has three maximal parts. The modes in Graphs 1608 and 1612 are embodiments of modes that can be observed in a multimode waveguide.

[0114] Referring to Figure 17, an example graph illustrating the electric field profile according to an exemplary embodiment is shown. In this exemplary embodiment, graph 1700 shows the electric field profile of an optical signal input into a single-mode waveguide in a mode-conversion waveguide system. TMij This refers to a TM mode in which the waveguide has i electric field peaks in the y direction on the x-axis and j electric field peaks in the z direction on the x-axis.

[0115] In this exemplary embodiment, the optical signal propagates from left to right in graph 1700. This propagation causes TM 11 From TM 31 This results in the conversion of the optical signal to [a specific format]. In this exemplary embodiment, the conversion efficiency is approximately 90 percent, and the total optical loss is approximately 7 percent.

[0116] Next, referring to Figure 18, another example of a graph illustrating the electric field profile according to an exemplary embodiment is shown. In this exemplary embodiment, graph 1800 shows the electric field profile of an optical signal input into a multimode waveguide in a mode-conversion waveguide system. The optical signal has a wavelength of 655 nm in this embodiment.™ ij This refers to a TM mode in which the waveguide has i electric field peaks in the y direction on the x-axis and j electric field peaks in the z direction on the x-axis.

[0117] In this exemplary embodiment, the optical signal propagates from right to left in Graph 1800. In this embodiment, the optical signal has a wavelength of 655 nm. This propagation results in TM 31 From TM 11 This results in the conversion of the optical signal to [a specific format]. In this exemplary embodiment, the conversion efficiency is approximately 98 percent, and the total optical loss is approximately 14 percent.

[0118] The illustrative electric field profiles for the mode-conversion optical waveguide system in Figures 15-18 are depicted to show the modes of the optical field that may be generated using the mode-conversion waveguide system, as illustrated in the examples of embodiments. The intensity and type of mode conversion that occurs may vary depending on the configuration of a particular mode-conversion waveguide system in one exemplary embodiment. For example, the mode-conversion waveguide system may use a variety of materials.

[0119] Next, referring to Figure 19, an illustrative flowchart of a process for converting the mode of light according to an exemplary embodiment is shown. The process in Figure 19 can be carried out using the mode-converting waveguide system 100 of Figure 1.

[0120] The process is initiated by sending light through a single-mode waveguide (operation 1900). In operation 1900, the light has a first mode while traveling through the single-mode waveguide. The process sends the light from the single-mode waveguide into a multimode interference region connected to the single-mode waveguide (operation 1902).

[0121] The process propagates the light away from the single-mode waveguide by reflecting the light in a cavity within the multimode interference region (operation 1904). The process then outputs the light from the multimode interference region (operation 1906).

[0122] The process sends the light output from the multimode interference region into a multimode waveguide (operation 1908). The process then terminates.

[0123] Referring to Figure 20, an illustrative flowchart of a process for converting the mode of light according to an exemplary embodiment is shown. The process in Figure 20 can be carried out using the mode-converting waveguide system 100 of Figure 1.

[0124] The process is initiated by sending light through a multimode waveguide (operation 2000). In operation 2000, the light has a second mode while traveling through the multimode waveguide. The process sends the light from the multimode waveguide into a multimode interference region connected to the multimode waveguide (operation 2002).

[0125] The process involves reflecting light in a cavity within the multimode interference region in a manner that causes the light to propagate away from the multimode waveguide (operation 2004). The process then outputs light from the multimode interference region (operation 2006). In operation 2006, the light has a first mode.

[0126] The process sends light output from the multimode interference region into a single-mode waveguide (operation 2008). The process then terminates.

[0127] The flowcharts and block diagrams in the various embodiments shown illustrate the structure, function, and operation of several possible embodiments of the apparatus and method in an exemplary embodiment. In this regard, each block in the flowchart or block diagram may represent at least one of a module, segment, function, or part of an operation or step. For example, one or more blocks may be implemented as program code, hardware, or a combination of program code and hardware. When implemented in hardware, the hardware may take the form of an integrated circuit manufactured or configured to perform, for example, one or more operations of the flowchart or block diagram. When implemented as a combination of program code and hardware, this implementation may take the form of firmware. Each block in the flowchart or block diagram may be implemented using dedicated hardware and a dedicated hardware system that performs various operations or combinations of operations of the program code executed by the dedicated hardware.

[0128] In some alternative embodiments of one exemplary embodiment, one or more functions described within a block may appear in a different order than that shown in the diagram. For example, in some cases, two consecutively shown blocks may be performed almost simultaneously, or sometimes blocks may be performed in reverse order depending on the functions they contain. In addition, other blocks may be added in addition to those shown in the flowchart or block diagram.

[0129] Next, referring to Figure 21, a block diagram of a product management system according to an exemplary embodiment is shown. The product management system 2100 is a physical hardware system. In this exemplary embodiment, the product management system 2100 includes at least one of the manufacturing system 2102 or the maintenance system 2104.

[0130] The manufacturing system 2102 is configured to manufacture products such as aircraft. As depicted, the manufacturing system 2102 includes manufacturing equipment 2106. Manufacturing equipment 2106 includes at least one of processing equipment 2108 or assembly equipment 2110.

[0131] Processing equipment 2708 is used to process nonlinear optical waveguide structures. Multiple copies or versions of the nonlinear optical waveguide structure can be processed on a substrate wafer.

[0132] The substrate wafer may include materials such as silicon, lithium niobate, quartz, sapphire, silicon carbide, or any other suitable substrate. The processing equipment 2708 may be used to process at least one of the following: optical waveguide structures, nonlinear optical waveguides, optical couplers, optical waveguide segments, laser transmitters, ultraviolet transmission systems, point-to-point communication devices, laser infrared counter-sources, underwater optical communication devices, or other suitable devices, antennas, or other suitable types of components. For example, the processing equipment 2708 may include machinery and tools.

[0133] With regard to processing semiconductor components and optical waveguide components, processing equipment 2708 may include at least one of the following: epitaxial reactors, oxidation systems, diffusion systems, etching systems, cleaning systems, bonding machines, dicing machines, wafer saws, ion implantation systems, physical vapor deposition systems, chemical vapor deposition systems, photolithography systems, electron beam lithography systems, plasma etchers, die attachment machines, wire bonders, die overcoat systems, molding equipment, hermetic sealers, electrical testers, burn-in ovens, retention bake ovens, ultraviolet erasure machines, or other suitable types of equipment that can be used to manufacture semiconductor structures.

[0134] Assembly equipment 2710 is equipment used to assemble parts to form chips, integrated circuits, multichip modules, computers, signal processors, aircraft, or any other products. Assembly equipment 2710 may also include machinery and tools. These machinery and tools may be at least one of robotic arms, spinner systems, spraying systems, and elevator systems, rail-based systems, or robots.

[0135] In this exemplary embodiment, the maintenance system 2104 includes a maintenance facility 2112. The maintenance facility 2112 may include any equipment necessary to perform maintenance on the aircraft. The maintenance facility 2112 may include tools for performing various operations on parts of the product. These operations may include at least one of the following: disassembly of parts, refurbishment of parts, inspection of parts, reworking of parts, manufacture of replacement parts, or other operations for performing maintenance on the product. Such operations may be periodic maintenance, inspection, replacement, refurbishment, or other types of maintenance operations.

[0136] In this exemplary embodiment, the maintenance equipment 2112 may include an ultrasonic inspection device, an X-ray imaging system, a vision system, a crawler, and other appropriate devices. In some cases, the maintenance equipment 2112 may include a processing facility 2108, an assembly facility 2110, or both, for manufacturing and assembling parts required for maintenance.

[0137] The product management system 2100 also includes a control system 2114. The control system 2114 is a hardware system and may also include software or other types of components. The control system 2114 is configured to control the operation of at least one of the manufacturing system 2102 or the maintenance system 2104. Specifically, the control system 2114 may control the operation of at least one of the processing equipment 2108, the assembly equipment 2110, or the maintenance equipment 2112.

[0138] The hardware within the control system 2114 may be implemented using hardware that may include computers, circuits, networks, and other types of equipment. Control may take the form of direct control of the manufacturing equipment 2106. For example, robots, computer-controlled machines, and other equipment may be controlled by the control system 2114. In other exemplary embodiments, the control system 2114 may manage actions performed by workers 2116 in manufacturing products and performing maintenance on products. For example, the control system 2114 may assign tasks, give instructions, display models, or perform other actions to manage actions performed by workers 2116. In these exemplary embodiments, the control system 2114 may manage at least one of manufacturing or maintaining a product or components of a product. The hardware within the control system 2714 may be implemented using hardware that may include computers, circuits, networks, and other types of equipment.

[0139] The control may take the form of direct control of the manufacturing equipment 2706. For example, robots, computer-controlled machines, and other equipment may be controlled by the control system 2714. In another exemplary embodiment, the control system 2714 may manage actions performed by workers 2716 in the manufacturing or maintenance of a product.

[0140] For example, the control system 2714 can assign tasks, give instructions, display models, or perform other actions to manage the actions performed by the worker 2716. In these exemplary embodiments, various processes for manufacturing semiconductor structures, optical structures, nonlinear optical waveguides, laser transmitters, photon generators, photon transmitters, photon detectors, ultraviolet transmission systems, point-to-point communication devices, laser infrared counter sources, underwater optical communication devices, or other suitable devices may be manufactured using processes implemented within the control system 2714.

[0141] In various exemplary embodiments, a worker 2116 may operate or interact with at least one of the following: manufacturing equipment 2106, maintenance equipment 2112, or control system 2114. This interaction may be performed to manufacture products within the product management system 2100.

[0142] Of course, the product management system 2100 may be configured to manage other products in many different industries. For example, the product management system 2100 may be used to manufacture products for the aerospace industry, the telecommunications industry, the space development industry, and other industries.

[0143] Some features of exemplary embodiments are described in the following sections. These sections are examples of features and are not intended to limit other exemplary embodiments.

[0144] Article 1. A mode-converting waveguide system, Single-mode waveguide, multimode waveguide, The single-mode waveguide and the multimode waveguide connected to the multimode interference region, and A mode-converting waveguide system including a cavity within the multimode interference region.

[0145] Article 2. The mode-converting waveguide system according to Clause 1, wherein the cavity reflects light having a first mode moving into the multimode interference region in such a manner that the light has a second mode.

[0146] Article 3. The mode-converting waveguide system according to Clause 1 or 2, wherein the multimode interference region has a shape symmetrical with respect to an axis extending centrally through the multimode interference region.

[0147] Article 4. The mode-converting waveguide system according to any one of the clauses 1 to 3, wherein the cavity is symmetrical with respect to an axis extending centrally through the multimode interference region.

[0148] Article 5. The mode-converting waveguide system according to any one of the following clauses, 1 to 4: The cavity is one of a void enclosed within the multimode interference region, a hole extending within the multimode interference region, and a hole extending through the multimode interference region.

[0149] Article 6. The mode-converting waveguide system according to any one of clauses 1 to 5, wherein the multimode interference region is composed of a first material, and the cavity is filled with a second material different from the first material.

[0150] Article 7. The mode-converting waveguide system according to any one of Clauses 1 to 6, wherein the multimode interference region includes cladding and a core region within the cladding, and the cavity is located within the core region within the multimode interference region and filled with cladding material for the cladding.

[0151] Article 8. The mode-converting waveguide system according to any one of the clauses 1 to 7, wherein the multimode interference region has a first width that is wider than the second width of the multimode waveguide.

[0152] Article 9. The mode-converting waveguide system according to any one of the clauses 1 to 8, wherein the width of the multimode waveguide tapers at the connection point of the multimode waveguide to the multimode interference region, and is wider at a point away from the connection point of the multimode waveguide to the multimode interference region.

[0153] Article 10. The multimode waveguide is A first section connected to the multimode interference region, and A mode-converting waveguide system according to any one of the clauses 1 to 9, comprising a second section connected to the first section, wherein the first section has a first cross-section and the second section has a second cross-section different from the first cross-section.

[0154] Article 11. The mode-converting waveguide system according to Clause 10, wherein the first cross section is made of silicon nitride, and the second cross section is made of a central region of lithium niobate located between the first lateral region of silicon nitride and the second lateral region of silicon nitride.

[0155] Article 12. A mode-converting waveguide system according to any one of the clauses 1 to 10, wherein light having a first mode travels through the single-mode waveguide, enters the multimode interference region, and exits the multimode interference region into the multimode waveguide in a second mode.

[0156] Article 13. The first mode described above is TE 11 The first mode is optical, and the second mode is TE 31 A mode-converting waveguide system as described in Clause 12, which is an optical mode.

[0157] Article 14. The first mode described above is TM 11 The first mode is light mode, and the second mode is TM 31 A mode-converting waveguide system as described in Clause 12, which is an optical mode.

[0158] Article 15. A mode-converting waveguide system according to any one of the clauses 1 to 14, wherein light having a first mode travels through the multimode waveguide, enters the multimode interference region, and exits the multimode interference region into the single-mode waveguide in a second mode.

[0159] Article 16. The second mode is TE 11 The optical mode is TE 31 A mode-converting waveguide system as described in Clause 15, which is an optical mode.

[0160] Article 17. The second mode is TM 11 The first mode is TM 31 A mode-converting waveguide system as described in Clause 15, which is an optical mode.

[0161] Article 18. A method for converting the mode of light, Transmitting the light through a single-mode waveguide, wherein the light has a first mode while traveling through the single-mode waveguide. To transmit the light from the single-mode waveguide into a multimode interference region connected to the single-mode waveguide, The light is propagated away from the single-mode waveguide, and the light is reflected in a cavity within the multimode interference region, and A method comprising outputting the light having a second mode from the multimode interference region.

[0162] Article 19. The method according to clause 18, further comprising sending the light output from the multimode interference region into a multimode waveguide.

[0163] Article 20. The method according to clause 18 or 19, wherein the multimode interference region has a shape symmetrical with respect to the plane with respect to the multimode interference region.

[0164] Article 21. The method according to any one of the claims 18 to 20, wherein the cavity is symmetrical with respect to an axis extending centrally through the multimode interference region.

[0165] Article 22. The method according to any one of the claims 18 to 21, wherein the cavity is one of a void enclosed within the multimode interference region, a hole extending within the multimode interference region, and a hole extending through the multimode interference region.

[0166] Article 23. The method according to any one of the claims 18 to 22, wherein the multimode interference region is composed of a first material, and the cavity is filled with a second material different from the first material.

[0167] Article 24. The method according to any one of the claims 18 to 23, wherein the multimode interference region includes cladding and a core region within the cladding, and the cavity is located within the core region within the multimode interference region and is filled with cladding material for the cladding.

[0168] Accordingly, exemplary embodiments of methods, apparatus, and systems for converting the modes of signals such as light are provided. Light is transmitted through a single-mode waveguide. In this case, the light has a first mode while traveling through the single-mode waveguide. Light is transmitted from the single-mode waveguide into a multimode interference region connected to the single-mode waveguide. Light is reflected by a cavity in the multimode interference region in such a way that the light propagates away from the single-mode waveguide. Light is output from the multimode interference region. In this case, the light has a second mode.

[0169] In exemplary embodiments, cavities within the multimode interference region are configured to enhance the efficiency of mode conversion. In exemplary embodiments, cavities may have shapes and positions that enhance efficiency and may reduce problems related to the difference between the refractive index in the mode conversion waveguide system and the desired refractive index for the optical signal propagating through the mode conversion waveguide system.

[0170] Furthermore, this disclosure includes embodiments as provided for in the following clauses. Article 1. Mode-converting waveguide systems (100, 400, 800, 1100), Single-mode waveguides (102, 404, 808, 1108), Multimode waveguides (106, 408, 1112, 1408), The multimode interference regions (104, 406, 810, 1110) connected to the single-mode waveguides (102, 404, 808, 1108) and the multimode waveguides (106, 408, 1112, 1408), and A mode-converting waveguide system (100, 400, 800, 1100) including cavities (118, 410, 814, 1114) within the aforementioned multimode interference regions (104, 406, 810, 1110). Article 2. The mode-converting waveguide system (100, 400, 800, 1100) according to Clause 1, wherein the cavities (118, 410, 814, 1114) reflect light (130) having a first mode (132) moving into the multimode interference region (104, 406, 810, 1110) in such a manner that the light (130) has a second mode (134). Article 3. The mode-converting waveguide system (100, 400, 800, 1100) according to Clause 1 or 2, wherein the multimode interference region (104, 406, 810, 1110) has a shape (200) that is symmetric with respect to an axis (202) extending centrally through the multimode interference region (104, 406, 810, 1110). Article 4. The mode-converting waveguide system (100, 400, 800, 1100) according to any one of clauses 1 to 3, wherein the cavities (118, 410, 814, 1114) are symmetric with respect to an axis (202) extending centrally through the multimode interference region (104, 406, 810, 1110). Article 5. The mode-converting waveguide system (100, 400, 800, 1100) described in any one of the following clauses (100, 400, 800, 1100): the cavity (118, 410, 814, 1114) is one of a void (204) surrounded within the multimode interference region (104, 406, 810, 1110), a hole (206) extending into the multimode interference region (104, 406, 810, 1110), and a hole (206) extending through the multimode interference region (104, 406, 810, 1110). Article 6. A mode-converting waveguide system (100, 400, 800, 1100) according to any one of clauses 1 to 5, wherein the multimode interference regions (104, 406, 810, 1110) are composed of a first material (208), and the cavities (118, 410, 814, 1114) are filled with a second material (210) different from the first material (208). Article 7. The multimode interference region (104, 406, 810, 1110) includes cladding (212, 414, 910, 1210, 1412) and core regions (214, 506, 602, 908, 1208, 1410) within the cladding (212, 414, 910, 1210, 1412), and the cavity (118, 410, 814, 1114) is part of the multimode interference region A mode-converting waveguide system (100, 400, 800, 1100) according to any one of clauses 1 to 6, located within the core regions (214, 506, 602, 908, 1208, 1410) within the regions (104, 406, 810, 1110) and filled with cladding material (216) for the cladding (212, 414, 910, 1210, 1412). Article 8. The mode-converting waveguide system (100, 400, 800, 1100) according to any one of clauses 1 to 7, wherein the multimode interference region (104, 406, 810, 1110) has a first width that is wider than the second width of the multimode waveguide (106, 408, 1112, 1408). Article 9. The mode-converting waveguide system (100, 400, 800, 1100) described in any one of clauses 1 to 8, wherein the width of the multimode waveguide (106, 408, 1112, 1408) tapers at the connection point with the multimode interference region (104, 406, 810, 1110) of the multimode waveguide (106, 408, 1112, 1408) compared to the width of the multimode waveguide (106, 408, 1112, 1408) at a location away from the connection point with the multimode interference region (104, 406, 810, 1110) of the multimode waveguide (106, 408, 1112, 1408). Article 10. The aforementioned multimode waveguides (106, 408, 1112, 1408) are A first section (306) connected to the multimode interference region (104, 406, 810, 1110), and A mode-converting waveguide system (100, 400, 800, 1100) according to any one of clauses 1 to 9, comprising a second section (308) connected to the first section (306), wherein the first section (306) has a first cross section (310) and the second section (308) has a second cross section (312) different from the first cross section (310). Article 11. The mode-converting waveguide system (100, 400, 800, 1100) according to Clause 10, wherein the first cross section (310) is made of silicon nitride, and the second cross section (312) is made of a central region (316) of lithium niobate located between a first lateral region (318) of silicon nitride and a second lateral region (320) of silicon nitride. Article 12. A mode-converting waveguide system (100, 400, 800, 1100) according to Clause 1, wherein light (130) having a first mode (132) travels through the single-mode waveguide (102, 404, 808, 1108), enters the multimode interference region (104, 406, 810, 1110), and exits from the multimode interference region (104, 406, 810, 1110) into the multimode waveguide (106, 408, 1112, 1408) in a second mode (134). Article 13. The aforementioned first mode (132) is TE 11 The optical mode is TE 31 A mode-converting waveguide system as described in Clause 12 (100, 400, 800, 1100), which is an optical mode. Article 14. The aforementioned first mode (132) is TM 11 The light mode is the second mode (134) mentioned above, and TM 31 A mode-converting waveguide system as described in Clause 12 (100, 400, 800, 1100), which is an optical mode. Article 15. A mode-converting waveguide system (100, 400, 800, 1100) according to Clause 1, wherein light (130) having a first mode (132) travels through the multimode waveguides (106, 408, 1112, 1408), enters the multimode interference region (104, 406, 810, 1110), and exits the multimode interference region (104, 406, 810, 1110) in a second mode (134) into the single-mode waveguides (102, 404, 808, 1108). Article 16. The aforementioned second mode (134) is TE 11 The optical mode is TE 31 A mode-converting waveguide system as described in Clause 15 (100, 400, 800, 1100), which is an optical mode. Article 17. The aforementioned second mode (134) is TM 11 It is an optical mode, and the aforementioned first mode (132) is TM 31A mode-converting waveguide system as described in Clause 15 (100, 400, 800, 1100), which is an optical mode. Article 18. A method for converting the mode of light (130), Transmitting the light (130) through a single-mode waveguide (102, 404, 808, 1108) (1900), wherein the light (132) has a first mode (132) while traveling through the single-mode waveguide (102, 404, 808, 1108), Transmitting the light (130) through a single-mode waveguide (102, 404, 808, 1108) (1900), Sending the light (130) from the single-mode waveguides (102, 404, 808, 1108) into the multimode interference region (104, 406, 810, 1110) connected to the single-mode waveguides (102, 404, 808, 1108) (1902), The light (130) is propagated away from the single-mode waveguide (102, 404, 808, 1108) by reflecting the light (130) in the cavities (118, 410, 814, 1114) within the multimode interference region (104, 406, 810, 1110) (1904), and A method comprising outputting (1906) the light (130) having a second mode (134) from the multimode interference region (104, 406, 810, 1110). Article 19. The method according to clause 18, further comprising sending the light (130) output from the multimode interference region (104, 406, 810, 1110) into a multimode waveguide (106, 408, 1112, 1408) (1908). Article 20. The method according to clause 18 or 19, wherein the multimode interference region (104, 406, 810, 1110) has a shape (200) that is symmetric with respect to the plane (205) with respect to the multimode interference region (104, 406, 810, 1110). Article 21. The method according to any one of the claims 18 to 20, wherein the cavities (118, 410, 814, 1114) are symmetric with respect to an axis (202) extending centrally through the multimode interference region (104, 406, 810, 1110). Article 22. The method according to any one of the following: the cavity (118, 410, 814, 1114) is one of a void (204) surrounded within the multimode interference region (104, 406, 810, 1110), a hole (206) extending into the multimode interference region (104, 406, 810, 1110), and a hole (206) extending through the multimode interference region (104, 406, 810, 1110). Article 23. The method according to any one of the claims 18 to 22, wherein the multimode interference regions (104, 406, 810, 1110) are composed of a first material (208), and the cavities (118, 410, 814, 1114) are filled with a second material (210) different from the first material (208). Article 24. The method according to any one of the claims 18 to 23, wherein the multimode interference regions (104, 406, 810, 1110) include cladding (212, 414, 910, 1210, 1412) and core regions (214, 506, 602, 908, 1208, 1410) within the cladding (212, 414, 910, 1210, 1412), and the cavities (118, 410, 814, 1114) are located within the core regions (214, 506, 602, 908, 1208, 1410) within the multimode interference regions (104, 406, 810, 1110) and are filled with cladding material (216) for the cladding (212, 414, 910, 1210, 1412).

[0171] The descriptions of various exemplary embodiments are presented for illustrative and explanatory purposes only and are not intended to be exhaustive or limit to the embodiments disclosed. Components that perform operations or tasks are described by various embodiments. In one exemplary embodiment, a component may be configured to perform the tasks or operations described. For example, this component may have a configuration or structural design that provides it with the ability to perform the operations or processes described in the embodiments as being performed by the component. Furthermore, to the extent that the words “includes / include,” “has,” and “contains,” and their variations are used herein, such words, like the word “comprises,” are intended to be inclusive as open-transition terms that do not exclude any additional or other elements.

[0172] Many modifications and variations will be apparent to those skilled in the art. Furthermore, various exemplary embodiments may offer different features compared to other preferred embodiments. One or more selected embodiments have been chosen and described to best illustrate the principles of the embodiments, their practical applications, and to facilitate the understanding of the disclosures of various embodiments and the various modifications suitable for specific applications considered.

Claims

1. A mode-converting waveguide system (100, 400, 800, 1100), comprising: a single-mode waveguide (102, 404, 808, 1108); Multimode waveguides (106, 408, 1112, 1408), a multimode interference region (104, 406, 810, 1110) connected to the single-mode waveguide (102, 404, 808, 1108) and the multimode waveguide (106, 408, 1112, 1408); and A mode-converting waveguide system (100, 400, 800, 1100) including a cavity (118, 410, 814, 1114) within the multimode interference region (104, 406, 810, 1110).

2. 2. The mode conversion waveguide system (100, 400, 800, 1100) of claim 1, wherein the cavity (118, 410, 814, 1114) reflects light (130) having a first mode (132) traveling within the multimode interference region (104, 406, 810, 1110) in such a way that the light (130) has a second mode (134).

3. 3. A mode conversion waveguide system (100, 400, 800, 1100) as described in claim 1 or 2, wherein the multimode interference region (104, 406, 810, 1110) has a shape (200) that is symmetrical about an axis (202) extending centrally through the multimode interference region (104, 406, 810, 1110).

4. 3. The mode-converting waveguide system (100, 400, 800, 1100) of claim 1 or 2, wherein the cavity (118, 410, 814, 1114) is symmetrical about an axis (202) extending centrally through the multimode interference region (104, 406, 810, 1110).

5. 3. A mode conversion waveguide system (100, 400, 800, 1100) as described in claim 1 or 2, wherein the cavity (118, 410, 814, 1114) is one of a void (204) enclosed within the multimode interference region (104, 406, 810, 1110), a hole (206) extending into the multimode interference region (104, 406, 810, 1110), and a hole (206) extending through the multimode interference region (104, 406, 810, 1110).

6. 3. A mode conversion waveguide system (100, 400, 800, 1100) as described in claim 1 or 2, wherein the multimode interference region (104, 406, 810, 1110) is composed of a first material (208) and the cavity (118, 410, 814, 1114) is filled with a second material (210) different from the first material (208).

7. The multimode interference region (104, 406, 810, 1110) includes a cladding (212, 414, 910, 1210, 1412) and a core region (214, 506, 602, 908, 1208, 1410) within the cladding (212, 414, 910, 1210, 1412), and the cavity (118, 410, 814, 1114) is configured to 3. The mode conversion waveguide system (100, 400, 800, 1100) of claim 1 or 2, wherein the mode conversion waveguide system (100, 400, 800, 1100) is positioned within the core region (214, 506, 602, 908, 1208, 1410) within an interference region (104, 406, 810, 1110) and is filled with cladding material (216) for the cladding (212, 414, 910, 1210, 1412).

8. 3. The mode-converting waveguide system (100, 400, 800, 1100) of claim 1 or 2, wherein the multimode interference region (104, 406, 810, 1110) has a first width that is greater than a second width of the multimode waveguide (106, 408, 1112, 1408).

9. 3. The mode-converting waveguide system of claim 1, wherein the multimode waveguide is tapered such that a width of the multimode waveguide is greater at a junction of the multimode waveguide with the multimode interference region than at a location away from the junction of the multimode waveguide with the multimode interference region.

10. The multimode waveguide (106, 408, 1112, 1408) a first section (306) connected to the multimode interference region (104, 406, 810, 1110); and 3. The mode conversion waveguide system (100, 400, 800, 1100) of claim 1 or 2, comprising a second section (308) connected to the first section (306), the first section (306) having a first cross section (310), and the second section (308) having a second cross section (312) different from the first cross section (310).

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