Stacked optical waveguide with respective facet angles

Abstract

To provide a system that can efficiently provide high quality optical information to a user in various applications.SOLUTION: Described herein is an apparatus which may contain a first waveguide with a first waveguide second major surface and a second waveguide with a second waveguide first major surface that is separated from the first waveguide second major surface by a separation layer. The apparatus may further contain a coupling element configured to couple in a first beam into the first waveguide at a first angle of incidence and couple in a second beam into the second waveguide at a second angle of incidence that is greater than the first angle of incidence. The apparatus may also contain a first group of facets arranged in the first waveguide and configured to couple out the first beam out of the first waveguide and a second group of facets arranged in the second waveguide and configured to couple out the second beam out of the second waveguide.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Unless otherwise indicated in this specification, the materials described in this section are not prior art to the claims of this application and are not to be regarded as prior art merely by inclusion in this section.

[0002] The present disclosure generally relates to systems and methods for presenting information to a user, and more particularly to optical systems and near-eye displays for presenting information to a user.

Background Art

[0003] Wearable optical devices such as near-eye displays and smart glasses are often limited to a single facet angle across the entire field of view in a particular dimension (e.g., left / right, up / down). Thus, designers need to weigh the benefits of a small facet angle (e.g., increased diffraction limit, increased aperture) against the benefits of a large facet angle (e.g., wider field of view). Further, conventional techniques provide a single resolution across a particular dimension (e.g., cannot provide foveal display of information). What is needed are solutions to these and other problems.

Summary of the Invention

[0004] An overview of a device (e.g., a stacked optical waveguide) will be provided. In some implementation forms, the device may include a first optical waveguide having a first main surface and a second main surface of the first optical waveguide. The device may also include a second optical waveguide having a first main surface and a second main surface of the second optical waveguide. The first main surface of the second optical waveguide may be separated from the second main surface of the first optical waveguide by a separation layer. The device may also include a coupling element configured to couple a first beam to the first optical waveguide at a first incident angle greater than the critical angle of the first optical waveguide. The coupling element may also be configured to couple a second beam to the second optical waveguide at a second incident angle greater than the first incident angle. The device may also include a first facet group disposed within the first optical waveguide between the first main surface and the second main surface of the first optical waveguide and configured to couple and output the first beam from the first optical waveguide. The device may also include a second facet group disposed within the second optical waveguide between the first main surface and the second main surface of the second optical waveguide and configured to couple and output the second beam from the second optical waveguide.

[0005] In some embodiments, the apparatus may include a first waveguide having a first major surface and a second major surface of the first waveguide. The apparatus may also include a second waveguide having a first major surface and a second major surface of the second waveguide. The first major surface of the second waveguide may be separated from the second major surface of the first waveguide by a separation layer. The apparatus may also include a coupling element configured to couple a first beam to the first waveguide at a first incident angle greater than the critical angle of the first waveguide. The coupling element can also be configured to couple a second beam to the second waveguide at a second incident angle greater than the first incident angle. The apparatus may also include a first facet group disposed within the first waveguide between the first major surface and the second major surface of the first waveguide and configured to couple and output the first beam from the first waveguide. The apparatus may also include a second facet group disposed within the second waveguide between the first major surface and the second major surface of the second waveguide and configured to couple and output the second beam from the second waveguide. The apparatus may also include a third facet group disposed within the second waveguide between the first major surface and the second major surface of the second waveguide and configured to couple and output the second beam from the second waveguide. The first major surface of the first waveguide, the second major surface of the first waveguide, the first major surface of the second waveguide, and the second major surface of the second waveguide may extend along a facet axis. The first waveguide and the second waveguide may be superimposed along a normal axis orthogonal to the facet axis. The first facet group may be disposed within the first waveguide at a first position along the facet axis. At least a portion of the second facet group may be disposed within the second waveguide at a second position along the facet axis different from the first position along the facet axis. At least a portion of the third facet group may be disposed within the second waveguide at a third position along the facet axis different from the first position. The first position along the facet axis may be between the second position along the facet axis and the third position along the facet axis.

[0006] In some embodiments, the apparatus may include a first waveguide having a first major surface and a second major surface of the first waveguide. The apparatus may also include a second waveguide having a first major surface and a second major surface of the second waveguide. The first major surface of the second waveguide may be separated from the second major surface of the first waveguide by a separation layer. The apparatus may also include a coupling element configured to couple a first beam to the first waveguide at a first incident angle greater than the critical angle of the first waveguide. The coupling element may also be configured to couple a second beam to the second waveguide at a second incident angle greater than the first incident angle. The apparatus may also include a first facet group disposed within the first waveguide between the first major surface and the second major surface of the first waveguide and configured to couple and output the first beam from the first waveguide. The apparatus may also include a second facet group disposed within the second waveguide between the first major surface and the second major surface of the second waveguide. The apparatus may also include a homogenizer disposed within the second waveguide between the coupling element and the second facet group and configured to replicate a second beam effective to increase the number of beams reflected within the second waveguide and incident on the second facet group. The second facet group may be configured to couple and output the beams (e.g., the second beam and the replicas of the second beam) reflected within the second waveguide from the second waveguide.

[0007] In some embodiments, the apparatus may include a first waveguide having a first major surface and a second major surface of the first waveguide. The apparatus may also include a second waveguide having a first major surface and a second major surface of the second waveguide. The first major surface of the second waveguide may be separated from the second major surface of the first waveguide by a separation layer. The apparatus may also include a coupling element configured to couple a first beam to the first waveguide at a first incident angle greater than the critical angle of the first waveguide. The coupling element may also be configured to couple a second beam to the second waveguide at a second incident angle greater than the first incident angle. The coupling element may include a partial reflection element configured to couple the first beam to the first waveguide at the first incident angle and pass a portion of the incident beam to a reflection element. The coupling element may also include a reflection element configured to couple the second beam to the second waveguide at the second incident angle. The apparatus may also include a first facet group disposed within the first waveguide between the first major surface and the second major surface of the first waveguide and configured to couple and output the first beam from the first waveguide. The apparatus may also include a second facet group disposed within the second waveguide between the first major surface and the second major surface of the second waveguide.

[0008] In some embodiments, the apparatus may include a first waveguide having a first major surface and a second major surface of the first waveguide. The apparatus may also include a second waveguide having a first major surface and a second major surface of the second waveguide. The first major surface of the second waveguide may be separated from the second major surface of the first waveguide by a separation layer. The apparatus may also include a coupling element configured to couple a first beam to the first waveguide at a first incident angle greater than the critical angle of the first waveguide. The coupling element may also be configured to couple a second beam to the second waveguide at a second incident angle greater than the first incident angle. The coupling element may include a partial reflection element configured to couple the first beam to the first waveguide at the first incident angle and pass a portion of the incident beam to a reflection element. The coupling element may also include a reflection element configured to couple the second beam to the second waveguide at the second incident angle. The apparatus may also include a first facet group disposed within the first waveguide between the first major surface and the second major surface of the first waveguide and configured to couple and output the first beam from the first waveguide. The apparatus may also include a second facet group disposed within the second waveguide between the first major surface and the second major surface of the second waveguide. The partial reflection element and the reflection element do not overlap or at least partially overlap when viewed along the normal direction perpendicular to the first major surface of the first waveguide, the second major surface of the first waveguide, the first major surface of the second waveguide, and the second major surface of the second waveguide.

[0009] In some implementations, the apparatus may include a first waveguide having a first major surface and a second major surface of the first waveguide. The apparatus may also include a second waveguide having a first major surface and a second major surface of the second waveguide. The first major surface of the second waveguide may be separated from the second major surface of the first waveguide by a separation layer. The apparatus may also include a coupling element configured to couple a first beam to the first waveguide at a first incident angle greater than the critical angle of the first waveguide. The coupling element may also be configured to couple a second beam to the second waveguide at a second incident angle greater than the first incident angle. The coupling element may include a beam splitter. The beam splitter may be configured to split an incident beam into a reflected beam and a transmitted beam, couple the reflected beam to the first waveguide, and couple the transmitted beam to the second waveguide. The reflected beam may be the first beam, and the transmitted beam may be the second beam. The apparatus may also include a first facet group disposed within the first waveguide between the first major surface and the second major surface of the first waveguide and configured to couple the first beam out of the first waveguide. The apparatus may also include a second facet group disposed within the second waveguide between the first major surface and the second major surface of the second waveguide.

[0010] In some implementations, the apparatus may include a first waveguide having a first major surface and a second major surface of the first waveguide. The apparatus may also include a second waveguide having a first major surface and a second major surface of the second waveguide. The first major surface of the second waveguide may be separated from the second major surface of the first waveguide by a separation layer. The apparatus may also include a coupling element configured to couple a first beam to the first waveguide at a first incident angle greater than the critical angle of the first waveguide. The coupling element may also be configured to couple a second beam to the second waveguide at a second incident angle greater than the first incident angle. The coupling element may include a prism and a beam splitter. The prism may be configured to refract an incident beam towards the beam splitter. The beam splitter may be configured to split the refracted incident beam into a reflected beam and a transmitted beam, couple the reflected beam to the first waveguide, and couple the transmitted beam to the second waveguide. The reflected beam may be the first beam, and the transmitted beam may be the second beam. The apparatus may also include a first facet group disposed within the first waveguide between the first major surface and the second major surface of the first waveguide and configured to couple and output the first beam from the first waveguide. The apparatus may also include a second facet group disposed within the second waveguide between the first major surface and the second major surface of the second waveguide.

[0011] In some implementations, the apparatus may include a first waveguide having a first major surface and a second major surface of the first waveguide. The apparatus may also include a second waveguide having a first major surface and a second major surface of the second waveguide. The first major surface of the second waveguide may be separated from the second major surface of the first waveguide by a separation layer. The apparatus may also include a coupling element configured to couple a first portion of the incident beam to the first waveguide at an incident angle greater than the critical angle of the first waveguide to generate a first beam. The coupling element may also be configured to couple a second portion of the incident beam to the second waveguide at an incident angle at which a second beam is generated. The apparatus may also include a first facet group disposed within the first waveguide between the first major surface and the second major surface of the first waveguide, configured to partially reflect the first beam to generate a reflected beam at an incident angle smaller than the first incident angle and a transmitted beam at the first incident angle, and configured to couple the reflected beam out of the first waveguide. The apparatus may also include a second facet group disposed within the second waveguide between the first major surface and the second major surface of the second waveguide, and configured to couple the second beam out of the second waveguide.

[0012] The foregoing summary is illustrative only and is not intended to be limiting in any way. By reference to the drawings and the following detailed description, additional aspects, embodiments, and features will become apparent in addition to the illustrative aspects, embodiments, and features described above. In the drawings, like reference numerals indicate the same or functionally similar elements.

Brief Description of the Drawings

[0013]

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DETAILED DESCRIPTION OF THE INVENTION

[0014] In the following description, in order to provide an understanding of the various embodiments of the present application, many specific details such as specific structures, components, materials, dimensions, processing steps, and techniques are described. However, it will be apparent to those skilled in the art that the various embodiments of the present application can be implemented without these specific details. In some cases, well-known structures or processing steps are not described in detail in order to avoid obscuring the present application.

[0015] As will be described in more detail below, wearable devices such as near-eye displays and / or smart glasses can be implemented by the systems and methods described in accordance with the present disclosure. This system can efficiently provide high-quality optical information to users in various applications.

[0016] FIG. 1 shows a block diagram of an exemplary optical system according to various embodiments of the present disclosure. The optical system 100 may include two or more devices or components. The optical system 100 can generally be implemented as a hybrid system including various electronic, optical, and electro-optical elements. The optical device 102 may include one or more elements from the optical system 100. As will be described in more detail below, the optical system 100 may include a wearable device 110 such as one or more near-eye displays or smart glasses, and the wearable device 110 can be worn over or around the user's head to transmit optical information to one or more of the user's eyes.

[0017] The wearable device 110 may include a controller 114 having a memory 116. The controller 114 may be configured to transmit and receive electrical signals to and from various other elements within the optical system 100, execute program instructions stored in the memory 116 to process and provide information, operate the wearable device 110, and interact with other systems external to the wearable device 110. The controller 114 may include a microcontroller, a processor, various discrete components, a programmable logic device, and / or various interface circuits that may access the memory 116 which may be removable, replaceable, programmable, and reprogrammable to update instructions to the controller 114.

[0018] The wearable device 110 may also include a power management module 120 having a battery 122. The power management module 120 may be configured to monitor the charging, discharging, and power consumption of the battery 122. Various elements of the wearable device 110 may receive power from the battery 122, including, for example, the controller 114, one or more image projectors 126 (projection optical devices or pods), and an optical engine 134 having one or more digital images 136.

[0019] The wearable device 110 may also include one or more image projectors 126 each configured to generate a parallel image beam based on the digital image 136. The parallel image beam may be an illumination representation of a digital image having an image field that is a two-dimensional representation of the digital image based on either a single graphic image (e.g., a still image) or a series of graphic images (e.g., a moving image). The parallel image beam may be collimated to infinity.

[0020] The wearable device 110 may also include one or more light guiding optical elements 130 (e.g., waveguide WG, LOE also referred to as a stacked optical waveguide) comprising a transparent material configured to receive and propagate light, and the light can be incident on and exit from various internal and external parts of the light guiding optical element 130. For example, the transparent material including the light guiding optical element 130 may include an optical glass or other suitable material that is converted into a complex optical structure using a process that may include processes such as coating, laminating, slicing, polishing, and shaping of the transparent material. This process may include the addition of a partially reflective or fully reflective material such as a mirror coating. Similarly, this process may include the addition of a partially opaque or fully opaque material such as a light cover for blocking light.

[0021] The wearable device 110 may also include one or more image projectors 126 and one or more optical engines 134 coupled to the light guiding optical element 130. The optical engine 134 may be configured to directly operate the image projector 126 under the instructions of the controller 114. For example, the optical engine 134 may be able to provide graphics processing of the digital image prior to projection of an illuminated representation of the digital image by the image projector 126.

[0022] The wearable device 110 may also include a frame 138 (e.g., a structure) for supporting and holding one or more elements within the wearable device 110. For example, the frame 138 can support and hold the first image projector 126a in a position adjacent to the first light guiding optical element 130a. Similarly, the frame 138 can support and hold the second image projector 126b in a position adjacent to the second light guiding optical element 130b. In this way, the frame 138 can support and hold a pair of one or two image projectors 126 and light guiding optical elements 130 above or around the user's head. In this specification, references are made regarding the orientation of various elements relative to each other. Such references may also include references to various elements of the wearable device 110 when supported by the frame 138, or references to three-dimensional (3D) references (e.g., the X, Y, Z axes), as described in the associated drawings.

[0023] The optical system 100 may also include a host computer 170 that can include a processor 174 configured to read and execute operations based on instructions 178 stored on a computer-readable medium 180. The instructions 178 may be provided to the controller 114 and may include at least some instructions stored in the memory 116. The host computer 170 can communicate with one or more elements of the wearable device 110 via a signal and power bus 188. In this way, the host computer 170 can supply power to charge the battery 122, provide instructions to the controller 114 and various other elements of the wearable device 110, receive status from them, and provide digital image data to the optical engine 134.

[0024] Figure 2 shows a top view of a stacked optical waveguide 200 according to various examples of the present disclosure. The stacked optical waveguide 200 can be an example of the light guiding optical element 130 described above and may function as an aperture expander. Although Figure 2 is shown as a top view (e.g., left / right on the page corresponds to the user's left / right visual axis), the stacked optical waveguide 200 may be mounted along other axes (e.g., up / down) without departing from the scope of the present disclosure.

[0025] The stacked optical waveguide 200 can include a first waveguide 202, a second waveguide 204, and a coupling element 206. The coupling element 206 may be included in a part of the first waveguide 202 and the second waveguide 204, or may be a separate component attached thereto.

[0026] The first waveguide 202 includes a first major surface 208 of the first waveguide and a second major surface 210 of the first waveguide. The second waveguide 204 includes a first major surface 212 of the second waveguide and a second major surface 214 of the second waveguide. The major surfaces are configured to cause total internal reflection (TIR) within each waveguide when the beam angle is greater than the critical angle of the waveguide, and to allow the beam to exit the waveguide when the beam angle is less than the critical angle of the waveguide (e.g., when perpendicular to the major surface).

[0027] The first waveguide 202 is separated from the second waveguide 204 by a separation layer 216 that can be an air gap, a low refractive index layer, or a low refractive index adhesive. Note that the separation layer 216 may not extend into the coupling element 206. That is, when the coupling element 206 is formed in the same substrate as the first waveguide 202 and the second waveguide 204 (as shown in the figure), a coupling separation layer 242 may exist between a part of the coupling element 206. The coupling separation layer 242 may include a refractive index matching material (e.g., a high refractive index adhesive, layer, or material). Alternatively, the coupling element 206 can be formed as a separate structure and connected to the ends of the first waveguide 202 and the second waveguide 204 (e.g., with a refractive index matching adhesive). Such an implementation form of the coupling element 206 looks similar to the coupling elements 506 and 606, but has different reflective elements.

[0028] The first waveguide 202 and the second waveguide 204 can be stacked along a normal axis 218 perpendicular to the first major surface 208 of the first waveguide, the second major surface 210 of the first waveguide, the first major surface 212 of the second waveguide, and the second major surface 214 of the second waveguide. Orthogonal to the normal axis 218 is the facet axis 246, which will be further described below.

[0029] The coupling element 206 is configured to receive an incident beam 244 (e.g., a parallel image beam) and couple the incident beam 244 or a portion thereof to the first waveguide 202 and the second waveguide 204. The incident beam 244 may come from an image projector or a pod (e.g., one of the image projectors 126), or from an aperture expander operating along another axis (e.g., up / down). Although shown as being parallel to the normal axis 218, the incident beam 244 can be incident on the coupling element 206 at any angle.

[0030] In the illustrated example, the coupling element 206 includes a partial reflection element 220 and a reflection element 222. The partial reflection element 220 is configured to reflect a portion of the incident beam 244 to generate a first beam 224 that enters the first waveguide 202 at a first beam incident angle 226. The first beam incident angle 226 may be greater than the critical angle of the first waveguide (e.g., between 45 degrees and 55 degrees from the normal axis 218). The partial reflection element 220 is further configured to pass the remaining portion of the incident beam 244 (e.g., the portion not reflected to generate the first beam 224) to the reflection element 222. The reflection element 222 is configured to reflect the remaining portion of the incident beam 244 to generate a second beam 228 that enters the second waveguide 204 at a second beam incident angle 230. The second beam incident angle 230 may be greater than the critical angle of the second waveguide and greater than the first beam incident angle 226 (e.g., between 55 degrees and 89 degrees from the normal axis 218). The partial reflection element 220 and the reflection element 222 can both be angled obliquely (e.g., with respect to the normal axis 218 and the facet axis 246) and may have different surface coatings.

[0031] As shown, the reflective element 222 may have a shallower angle with respect to the normal axis 218. Accordingly, a portion of the coupling element 206 may extend beyond the second major surface 214 of the second waveguide. By doing so, it becomes possible to make (e.g., match) the projected widths or profiles of the reflective element 222 and the partial reflective element 220 the same (e.g., identical) (e.g., the projected profile when viewed along the facet axis 246 and / or along the normal axis 218). As a result, the reflective element 222 will receive the entire cross-section of the light transmitted through the partial reflective element 220. The extension may be a triangular structure that is adhered to the second major surface of the second waveguide via a refractive index-matching adhesive, as shown. Accordingly, both the partial reflective element 220 and the reflective element 222 can receive the entire aperture width of the incident beam 224.

[0032] The first waveguide 202 and the second waveguide 204 include facets configured to couple the beam out of the first waveguide 202 and the second waveguide 204 (e.g., for reception by a user's eye). The facets are also configured such that a portion of the beam can be transmitted through the facet to an adjacent facet (for coupling by the adjacent facets). The first waveguide 202 includes a first facet group 232. The second waveguide includes a second facet group 234 and a third facet group 236. The first facet group 232 can have a first facet angle 238 with respect to the normal axis 218, and the second facet group 234 and the third facet group 236 can have a second facet angle 240 with respect to the normal axis 218. Accordingly, the first facet group 232, the second facet group 234, and the third facet group 236 can be tilted obliquely with respect to the normal axis 218 and the facet axis 246. The second facet angle 240 may be smaller than the first facet angle 238. The second facet group 234 and the third facet group 236 can be arranged along the facet axis 246 so as to surround the first facet group 232 (e.g., such that the first facet group 232 is between the second facet group 234 and the third facet group 236 when viewed along the normal axis 218). In the illustrated example, the third facet group 232 is closer to the coupling element 206 than the first facet group 232.

[0033] By having two waveguides each having three facet groups with respective facet angles, a foveal image (e.g., an image having different resolutions over at least one dimension) can be generated. By doing so, the stacked optical waveguide 200 can potentially utilize the good aspects of various facet angles (e.g., higher sensitivity / greater aperture at the center of the projected image, greater field of view further away from the center).

[0034] Each of the facets may be at least a partially reflective optical structure having a flat surface (along with the partial reflector 220 and the reflector 222). Each facet (or element) may include an angular selectivity coating having an optical axis offset from the normal direction to the coating to selectively pass or attenuate illumination having the same or different orientations respectively.

[0035] As used herein, each facet group may include a plurality of planar optical elements (e.g., facets) that are spaced apart from each other, parallel to each other, and partially reflective. Thus, each of the facet groups may be parallel to each other and may be arranged at the same oblique angle. Also, the facets described herein can include an angular selectivity coating and can be controlled to have multiple states (e.g., on / off) or to change the level of reflectivity and / or transmittance of each facet or a cooperative assembly of facets within the structure. The final facet within the structure (e.g., the terminal facet, the rightmost facet of the first facet group 232 and the second facet group 234) can be fully mirror finished (e.g., not a partial mirror finish) to reflect the remaining illumination that may have passed through the previous facets within the structure. Alternatively, to maintain consistency, reduce complexity, and simplify the structure, each facet may have the same partial reflectivity.

[0036] FIG. 3 shows a top view of another stacked optical waveguide 300 according to various embodiments of the present disclosure. The stacked optical waveguide 300 has many of the same structures as the stacked optical waveguide 200. Therefore, the same numbering and names are used. For simplicity, only the features specific to the stacked optical waveguide 300 will be described. Any of the features of the stacked optical waveguide 200 (other than the features specifically mentioned for the stacked optical waveguide 300 and / or those specific to the stacked optical waveguide 200) should be assumed to be applicable to the stacked optical waveguide 300.

[0037] Similar to the stacked optical waveguide 200, the reflective element 222 of the stacked optical waveguide 300 may have a shallower angle with respect to the normal axis 218. Instead of extending the reflective element 222 beyond the second major surface 214 of the second waveguide as in the stacked optical waveguide 200, the reflective element 222 of the stacked optical waveguide 300 extends only up to the second major surface 214 of the second waveguide. Therefore, the reflective element 222 may not receive the entire aperture width of the light that has passed through the partial reflective element 220. In other words, the partial reflective element 220 can receive the entire aperture width of the incident beam 244, and the reflective element 222 can receive a part of the aperture width of the incident beam 244. Therefore, the third facet group (for example, the third facet group 236) may not be necessary.

[0038] In the stacked waveguide 300, the first waveguide 202 includes a first facet group 232. The second waveguide 204 includes a second facet group 234 without including a third facet group 236. To compensate for the shorter length of the reflective element 222, a homogenizer 302 can be mounted within the second waveguide 204 between the coupling element 206 and the second facet group 234. The homogenizer 302 can be disposed substantially midway between the second major surface 214 and the first major surface 212 of the second waveguide in a parallel plane, i.e., in the vertical direction. The first waveguide 202 may not require a homogenizer.

[0039] The homogenizer 302 can be any type of optical homogenizer configured to improve the uniformity of illumination. For example, the homogenizer 302 can include a partial planar reflector as a semi-reflective surface, a partially transmissive surface, or a film added within the second waveguide 204. The homogenizer 302 can effectively double the number of reflected beams within the second waveguide 204 by reflecting the light beam across the second waveguide 204 (e.g., by TIR) to rise or fall. By rising, a part of the light from below the homogenizer 302 is reflected at the lower surface of the homogenizer 302, and the remaining part of the light passes through the homogenizer, effectively doubling the number of light beams. By falling, a part of the light from above the homogenizer 302 can be reflected at the upper surface of the homogenizer 302, and the remaining part of the light can pass through the homogenizer, effectively doubling the number of light beams.

[0040] By having two waveguides without protrusions to compensate for the extended length of the reflective element 222, a foveal image can be generated in a compact form factor. By doing so, the stacked optical waveguide 300 may be able to utilize surfaces with good various facet angles (e.g., higher sensitivity / larger aperture at the center of the projected image, larger field of view further away from the center).

[0041] FIG. 4 shows a top view of another stacked optical waveguide 400 according to various embodiments of the present disclosure. The stacked optical waveguide 300 has many structures similar to the stacked optical waveguide 200. Therefore, the same numbering and names are used. For simplicity, only the features specific to the stacked optical waveguide 400 will be described. Any features of the stacked optical waveguide 200 (other than those specifically mentioned for the stacked optical waveguide 400 and / or those specific to the stacked optical waveguide 200) should be assumed to be applicable to the stacked optical waveguide 400.

[0042] In the stacked optical waveguide 400, the partial reflection element 220 and the reflection element 222 may not overlap when viewed along the normal axis 218. In this embodiment, the partial reflection element 220 receives the first portion of the incident beam 244, and the reflection element 222 receives the second portion of the incident beam. For the sake of explanation, the incident beam 244 is split into two beams (one for each element). These portions may be mutually exclusive. If they are mutually exclusive, the partial reflection element 220 may be fully reflective. Similar to the stacked optical waveguide 200, the reflection element 222 of the stacked optical waveguide 400 may have a shallower angle with respect to the normal axis 218. Also, the reflection element 222 may extend beyond the second major surface 214 of the second optical waveguide, as in the stacked optical waveguide 200. Since the reflection element 220 can receive only the second portion of the incident beam 244, the third facet group (e.g., the third facet group 236) may not be necessary.

[0043] In the stacked optical waveguide 300, the first optical waveguide 202 includes the first facet group 232. The second optical waveguide includes the second facet group 234 and does not include the third facet group 236.

[0044] By having two optical waveguides with mutually exclusive portions of the incident beam 244, a foveal image can be generated with minimal illuminance loss. By doing so, the stacked optical waveguide 300 may be able to utilize the good aspects of various facet angles (e.g., higher sensitivity / larger aperture at the center of the projected image, larger field of view further away from the center).

[0045] FIG. 5 shows a top view of another stacked optical waveguide 500 according to various embodiments of the present disclosure. The stacked optical waveguide 500 has many structures similar to the stacked optical waveguide 200. Therefore, the same numbering and names are used. For simplicity, only the features specific to the stacked optical waveguide 500 are described. Any features of the stacked optical waveguide 200 (other than those specifically mentioned for the stacked optical waveguide 500 and / or those specific to the stacked optical waveguide 200) should be assumed to be applicable to the stacked optical waveguide 500.

[0046] In the stacked optical waveguide 500, the coupling element 206 may be implemented as an independent structure attached to the ends of the first optical waveguide 202 and the second optical waveguide 204 (similar to the alternative example described for the stacked optical waveguide 200). Alternatively, the structure included therein may be implemented in one or more of the first optical waveguide 202 or the second optical waveguide 204 (similar to the stacked optical waveguide 200).

[0047] The stacked optical waveguide 500 is configured to receive the incident beam 244 at an angle other than parallel to the normal axis 218. The coupling element 206 includes a beam splitter 502 that is arranged adjacent to each other between the first optical waveguide 202 and the second optical waveguide 204 along the normal axis 218 and is parallel to the main surface. The beam splitter 502 is configured to receive the incident beam 244 and split it into a first beam 224 and a second beam 228. The first beam 224 and the second beam 228 may be mirrors for each other, and / or the corresponding reflection points from their respective main surfaces along the facet axis 246 may be different, but they have the same incident angle (for example, to each optical waveguide).

[0048] In the stacked optical waveguide 500, the first optical waveguide 202 includes a first facet group 232. The second optical waveguide includes a second facet group 234 without including a third facet group 236. The facet angles of the first facet group 232 and the second facet group 234 may be the same. Further, the first facet group 232 and the second facet group 234 may be aligned along the facet axis 246.

[0049] FIG. 6 shows a top view of another stacked optical waveguide 600 according to various embodiments of the present disclosure. The stacked optical waveguide 600 has many of the same structures as the stacked optical waveguide 200. Accordingly, the same numbering and names are used. For simplicity, only the features specific to the stacked optical waveguide 600 are described. Any of the features of the stacked optical waveguide 200 (other than those specifically mentioned for the stacked optical waveguide 600 and / or those specific to the stacked optical waveguide 200) should be assumed to be applicable to the stacked optical waveguide 600.

[0050] In this exemplary figure, the first waveguide 202 is below the second waveguide 204. This ensures that the relationship between the beam incident angle and the facet angle (e.g., a shallow waveguide and a non - shallow waveguide) is similar to the relationship of the stacked optical waveguide 200. The stacked optical waveguide 600 is configured to receive the incident beam 244 at an angle other than parallel to the normal axis 218, similar to the stacked waveguide 500.

[0051] The coupling element 206 includes a prism 602 configured to refract the incident beam 244 onto the beam splitter 502. The beam splitter 502 is mounted at an angle not parallel to the facet axis 246 within the same substrate as the second waveguide 204 (e.g., between the plane of the first major surface 212 of the second waveguide and the second major surface of the second waveguide), and the beam splitter 502 is configured to split the refracted incident beam 244 into a first beam 224 and a second beam 228. To do so, the beam splitter 502 can be arranged at an angle oblique to the normal axis 218 and the facet axis 246. Similar to the stacked optical waveguide 200, the first incident angle 226 may be smaller than the second incident angle 228.

[0052] The stacked optical waveguide 600 may include the first facet group 232 and the second facet group 234 without including the third facet group 236. In the stacked optical waveguide 600, the second facet group 234 may be configured to couple and output the second beam 228 from the stacked optical waveguide 600, and the first facet group 232 may be configured to couple and output the first beam 224 via the second waveguide 204. The stacked optical waveguide 600 may also include a homogenizer 302 disposed in the second waveguide 204 at a position similar to that of the stacked optical waveguide 300. The first waveguide 202 may not require a homogenizer.

[0053] FIG. 7 shows a top view of another stacked optical waveguide 700 according to various embodiments of the present disclosure. The stacked optical waveguide 700 has many structures similar to those of the stacked optical waveguide 200. Therefore, the same numbering and names are used. For simplicity, only the features specific to the stacked optical waveguide 700 are described. Any of the features of the stacked optical waveguide 200 (other than the features specifically mentioned for the stacked optical waveguide 700 and / or those specific to the stacked optical waveguide 200) should be assumed to be applicable to the stacked optical waveguide 700.

[0054] In the stacked optical waveguide 700, the coupling element 206 may be implemented as an independent structure attached to the ends of the first waveguide 202 and the second waveguide 204 (similar to the alternative example described with respect to the stacked optical waveguide 200). Alternatively, the structures included therein may be implemented in one or more of the first waveguide 202 or the second waveguide 204 (similar to the stacked optical waveguide 200).

[0055] The coupling element 206 does not include the partial reflection element 220, and the reflection element 222 extends along the normal axis from the first main surface 208 of the first waveguide to the second main surface 214 of the second waveguide. The reflection element 222 is configured to receive the entire aperture of the incident beam 244 (illustrated as two beams), reflect the first portion of the incident beam 244 as the first beam 224 into the first waveguide 202, and reflect the second portion of the incident beam 244 as the second beam 228 into the second waveguide 204. The first beam 224 and the second beam 228 may have similar incident angles. The second waveguide 204 may include a homogenizer 302 to compensate for not receiving the entire aperture of the incident beam 244. The first waveguide 202 may not require a homogenizer.

[0056] Similar to the stacked optical waveguide 200, the first facet angle 238 may be smaller than the second facet angle 240. However, the first facet group 232 may not be configured to directly couple and output the first beam 224. Instead, each of the first facet group 232 may be configured to receive the first beam 224, reflect a portion of the first beam 224, and generate a reflected beam at an angle smaller than the critical angle of the first waveguide 202. The reflected beam can then be reflected at the first main surface 208 of the first waveguide and return to each facet. Each facet can then couple and output the reflected beam from the first waveguide 202.

[0057] In this way, the stacked optical waveguide 700 can utilize the coupling element 206 with a single reflection element and still achieve the advantages of multiple facet angles. By doing so, the complexity and cost of the stacked optical waveguide 700 can be reduced compared to other waveguides.

[0058] The terms used in this specification are for the purpose of describing particular embodiments only and are not intended to limit the present invention. As used in this specification, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly dictates otherwise. As used herein, the terms "include", "comprises", and / or "comprising" identify the presence of the described features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. Further, terms such as above, upper surface, below, lower surface, upward, downward, left, right, front, back, etc. are to be understood in the context of the expressions described and illustrated above such that the wearable device can have such an orientation with respect to various elements as based on or supported by the frame or as shown in the figures of the drawings.

[0059] In the following claims, where applicable, the corresponding structures, materials, acts, and equivalents of all means-plus-function or step-plus-function elements are intended to include any structure, material, or act for performing the recited function in combination with other claimed elements specifically claimed for performing that function. The description of the present invention has been presented for purposes of illustration and description, but is not intended to be exhaustive or limiting of the invention in the disclosed form. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the invention. The embodiments were chosen and described in order to best explain the principles and practical applications of the invention and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated.

Examples

[0060] Example 1a: An apparatus, comprising: a first waveguide including a first main surface of the first waveguide and a second main surface of the first waveguide; a second waveguide including a first main surface of the second waveguide and a second main surface of the second waveguide, wherein the first main surface of the second waveguide is separated from the second main surface of the first waveguide by a separation layer; a coupling element configured to couple a first beam to the first waveguide at a first incident angle greater than a critical angle of the first waveguide and to couple a second beam to the second waveguide at a second incident angle greater than the first incident angle; a first facet group disposed within the first waveguide between the first main surface of the first waveguide and the second main surface of the first waveguide and configured to couple and output the first beam from the first waveguide; and a second facet group disposed within the second waveguide between the first main surface of the second waveguide and the second main surface of the second waveguide and configured to couple and output the second beam from the second waveguide.

[0061] Example 2a: The apparatus according to Example 1a, wherein the first incident angle is between 45 degrees and 55 degrees from a normal axis perpendicular to the first main surface of the first waveguide, the second main surface of the first waveguide, the first main surface of the second waveguide, and the second main surface of the second waveguide, and the second incident angle is between 55 degrees and 89 degrees from the normal axis.

[0062] Example 3a: The apparatus according to Example 1a or 2a, wherein the first facet group is disposed at a first facet angle with respect to a normal axis perpendicular to the first main surface of the first waveguide, the second main surface of the first waveguide, the first main surface of the second waveguide, and the second main surface of the second waveguide, and the second facet group is disposed at a second facet angle with respect to the normal axis.

[0063] Example 4a: The apparatus according to any one of Examples 1a to 3a, wherein the first facet angle is different from the second facet angle.

[0064] Example 5a: The apparatus according to any one of Examples 1a to 4a, wherein the first facet angle is greater than the second facet angle.

[0065] Example 6a: The first main surface of the first waveguide, the second main surface of the first waveguide, the first main surface of the second waveguide, and the second main surface of the second waveguide extend along the facet axis, the first waveguide and the second waveguide are overlapped along a normal axis orthogonal to the facet axis, the first facet group is disposed in the first waveguide at a first position along the facet axis, and at least a part of the second facet group is disposed in the second waveguide at a second position along the facet axis different from the first position along the facet axis. The device according to any one of Examples 1a to 5a.

[0066] Example 7a: The second position along the facet axis is farther from the coupling element than the first position along the facet axis. The device according to Example 6a.

[0067] Example 8a: Further includes a third facet group disposed in the second waveguide between the first main surface and the second main surface of the second waveguide and configured to couple and output the second beam from the second waveguide. At least a part of the third facet group is disposed in the second waveguide at a third position along the facet axis different from the first position along the facet axis. The device according to Example 6a or 7a.

[0068] Example 9a: The third position along the facet axis is closer to the coupling element than the first position along the facet axis. The device according to Example 8a.

[0069] Example 10a: Further including a third facet group disposed in the second waveguide between the first main surface and the second main surface of the second waveguide and configured to couple and output the second beam from the second waveguide, the first main surface of the first waveguide, the second main surface of the first waveguide, the first main surface of the second waveguide, and the second main surface of the second waveguide extend along a facet axis, the first waveguide and the second waveguide are overlapped along a normal axis orthogonal to the facet axis, the first facet group is disposed in the first waveguide at a first position along the facet axis, at least a part of the second facet group is disposed in the second waveguide at a second position along the facet axis different from the first position along the facet axis, at least a part of the third facet group is disposed in the second waveguide at a third position along the facet axis different from the first position along the facet axis, and the first position along the facet axis is between the second position along the facet axis and the third position along the facet axis. The apparatus according to Example 1a.

[0070] Example 11a: Further including a homogenizer disposed in the second waveguide between the coupling element and the second facet group and configured to replicate the second beam effective to increase the number of beams reflected in the second waveguide and incident on the second facet group. The apparatus according to any one of Examples 1a to 7a.

[0071] Example 12a: The coupling element includes a partial reflection element configured to couple the first beam into the first waveguide at the first incident angle and pass a part of the incident beam to the reflection element, and the reflection element configured to couple the second beam into the second waveguide at the second incident angle. The apparatus according to any one of Examples 1a to 11a.

[0072] Example 13a: The partial reflection element is the device according to Example 12a that coincides with the reflection element when viewed along the normal axis perpendicular to the first main surface of the first waveguide, the second main surface of the first waveguide, the first main surface of the second waveguide, and the second main surface of the second waveguide.

[0073] Example 14a: The partial reflection element is the device according to Example 12a that surrounds the reflection element when viewed along the normal axis perpendicular to the first main surface of the first waveguide, the second main surface of the first waveguide, the first main surface of the second waveguide, and the second main surface of the second waveguide.

[0074] Example 15a: The device according to Example 12a, wherein when viewed along the normal axis perpendicular to the first main surface of the first waveguide, the second main surface of the first waveguide, the first main surface of the second waveguide, and the second main surface of the second waveguide, the partial reflection element and the reflection element at least partially overlap.

[0075] Example 16a: The device according to Example 12a, wherein when viewed along the normal axis perpendicular to the first main surface of the first waveguide, the second main surface of the first waveguide, the first main surface of the second waveguide, and the second main surface of the second waveguide, the partial reflection element and the reflection element do not overlap.

[0076] Example 17a: The reflection element is the device according to Example 12a, 13a, 15a, or 16a that extends beyond the second main surface of the second waveguide.

[0077] Example 18a: The coupling element includes a prism and a beam splitter. The prism is configured to refract an incident beam toward the beam splitter. The beam splitter is configured to split the refracted incident beam into a reflected beam and a transmitted beam, couple the reflected beam to the first waveguide, and couple the transmitted beam to the second waveguide. The reflected beam is the first beam, and the transmitted beam is the second beam. The device according to any one of Examples 1a to 11a.

[0078] Example 19a: The apparatus according to any one of Examples 1a to 18a, wherein the second beam passes through the first waveguide after being coupled and output from the second waveguide.

[0079] Example 20a: The apparatus according to any one of Examples 1a to 19a, wherein the separation layer includes an air gap or a low refractive index adhesive.

[0080] Example 21a: The apparatus according to any one of Examples 1a to 20a, wherein the coupling element is attached to ends of the first waveguide and the second waveguide.

[0081] Example 22a: The apparatus according to any one of Examples 1a to 20a, wherein the coupling element is formed in the same substrate as the first waveguide and the second waveguide.

[0082] Example 1b: An apparatus, comprising: a first waveguide including a first major surface of the first waveguide and a second major surface of the first waveguide; a second waveguide including a first major surface of the second waveguide and a second major surface of the second waveguide, wherein the first major surface of the second waveguide is separated from the second major surface of the first waveguide by a separation layer; a coupling element configured to couple a first beam to the first waveguide at a first incident angle greater than a critical angle of the first waveguide and to couple a second beam to the second waveguide at a second incident angle greater than the first incident angle; a first facet group disposed within the first waveguide between the first major surface of the first waveguide and the second major surface of the first waveguide and configured to couple and output the first beam from the first waveguide; a second facet group disposed within the second waveguide between the first major surface of the second waveguide and the second major surface of the second waveguide and configured to couple and output the second beam from the second waveguide; and a third facet group disposed within the second waveguide between the first major surface of the second waveguide and the second major surface of the second waveguide and configured to couple and output the second beam from the second waveguide, wherein the first major surface of the first waveguide, the second major surface of the first waveguide, the first major surface of the second waveguide, and the second major surface of the second waveguide extend along a facet axis, the first waveguide and the second waveguide are overlapped along a normal axis orthogonal to the facet axis, the first facet group is disposed within the first waveguide at a first position along the facet axis, at least a part of the second facet group is disposed within the second waveguide at a second position along the facet axis different from the first position along the facet axis, at least a part of the third facet group is disposed within the second waveguide at a third position along the facet axis different from the first position along the facet axis, and the first position along the facet axis is between the second position along the facet axis and the third position along the facet axis.

[0083] Example 2b: The device according to Example 1b, wherein the first incident angle is between 45 degrees and 55 degrees with respect to the normal axis perpendicular to the first main surface of the first waveguide, the second main surface of the first waveguide, the first main surface of the second waveguide, and the second main surface of the second waveguide, and the second incident angle is between 55 degrees and 89 degrees with respect to the normal axis.

[0084] Example 3b: The device according to Example 1b or 2b, wherein the first facet group is arranged at a first facet angle with respect to the normal axis perpendicular to the first main surface of the first waveguide, the second main surface of the first waveguide, the first main surface of the second waveguide, and the second main surface of the second waveguide, and the second facet group and the third facet group are arranged at a second facet angle with respect to the normal axis.

[0085] Example 4b: The device according to any one of Examples 1b to 3b, wherein the first facet angle is different from the second facet angle.

[0086] Example 5b: The device according to any one of Examples 1b to 4b, wherein the first facet angle is larger than the second facet angle.

[0087] Example 6b: The device according to any one of Examples 1b to 5b, wherein the second position along the facet axis is farther from the coupling element than the first position along the facet axis.

[0088] Example 7b: The device according to any one of Examples 1b to 6b, wherein the third position along the facet axis is closer to the coupling element than the first position along the facet axis.

[0089] Example 8b: The device according to any one of Examples 1b to 7b, wherein the first position along the facet axis is between the second position along the facet axis and the third position along the facet axis.

[0090] Example 9b: The coupling element includes a partial reflection element configured to couple the first beam into the first waveguide at the first incident angle and pass a part of the incident beam to the reflection element, and the reflection element configured to couple the second beam into the second waveguide at the second incident angle, and the device according to any one of Examples 1b to 8b.

[0091] Example 10b: The partial reflection element coincides with the reflection element when viewed along the normal axis perpendicular to the first main surface of the first waveguide, the second main surface of the first waveguide, the first main surface of the second waveguide, and the second main surface of the second waveguide, and the device according to any one of Examples 1b to 9b.

[0092] Example 11b: The partial reflection element and the reflection element at least partially overlap when viewed along the normal axis perpendicular to the first main surface of the first waveguide, the second main surface of the first waveguide, the first main surface of the second waveguide, and the second main surface of the second waveguide, and the device according to any one of Examples 1b to 10b.

[0093] Example 12b: The reflection element extends beyond the second main surface of the second waveguide, and the device according to any one of Examples 1b to 11b.

[0094] Example 13b: After the second beam is coupled and output from the second waveguide, it passes through the first waveguide, and the device according to any one of Examples 1b to 12b.

[0095] Example 14b: The separation layer includes an air gap or a low refractive index adhesive, and the device according to any one of Examples 1b to 13b.

[0096] Example 15b: The coupling element is attached to the ends of the first waveguide and the second waveguide, and the device according to any one of Examples 1b to 14b.

[0097] Example 16b: The coupling element is formed in the same substrate as the first waveguide and the second waveguide, and the device according to any one of Examples 1b to 15b.

[0098] Example 1c: A device including a first waveguide including a first main surface and a second main surface of the first waveguide, and a second waveguide including a first main surface and a second main surface of the second waveguide, wherein the first main surface of the second waveguide is separated from the second main surface of the first waveguide by a separation layer; a coupling element configured to couple a first beam to the first waveguide at a first incident angle greater than a critical angle of the first waveguide and to couple a second beam to the second waveguide at a second incident angle greater than the first incident angle; a first facet group disposed in the first waveguide between the first main surface and the second main surface of the first waveguide and configured to couple and output the first beam from the first waveguide; a second facet group disposed in the second waveguide between the first main surface and the second main surface of the second waveguide and configured to couple and output the second beam from the second waveguide; and a homogenizer disposed in the second waveguide between the coupling element and the second facet group, the homogenizer being configured to replicate the second beam effective to increase the number of beams reflected in the second waveguide and incident on the second facet group, and the second facet group being configured to couple the beam from the homogenizer reflected in the second waveguide out of the second waveguide.

[0099] Example 2c: In the device according to Example 1c, the first incident angle is between 45 degrees and 55 degrees from a normal axis perpendicular to the first main surface of the first waveguide, the second main surface of the first waveguide, the first main surface of the second waveguide, and the second main surface of the second waveguide, and the second incident angle is between 55 degrees and 89 degrees from the normal axis.

[0100] Example 3c: The first facet group is arranged at a first facet angle with respect to the normal axis perpendicular to the first main surface of the first waveguide, the second main surface of the first waveguide, the first main surface of the second waveguide, and the second main surface of the second waveguide, and the second facet group is arranged at a second facet angle with respect to the normal axis. The device according to Example 1c or 2c.

[0101] Example 4c: The first facet angle is different from the second facet angle. The device according to any one of Examples 1c to 3c.

[0102] Example 5c: The first facet angle is larger than the second facet angle. The device according to any one of Examples 1c to 4c.

[0103] Example 6c: The first main surface of the first waveguide, the second main surface of the first waveguide, the first main surface of the second waveguide, and the second main surface of the second waveguide extend along the facet axis, the first waveguide and the second waveguide are overlapped along the normal axis perpendicular to the facet axis, the first facet group is arranged in the first waveguide at a first position along the facet axis, and at least a part of the second facet group is arranged in the second waveguide at a second position along the facet axis different from the first position along the facet axis. The device according to any one of Examples 1c to 5c.

[0104] Example 7c: The second position along the facet axis is farther from the coupling element than the first position along the facet axis. The device according to any one of Examples 1c to 6c.

[0105] Example 8c: The coupling element includes a partial reflection element configured to couple the first beam into the first waveguide at the first incident angle and pass a part of the incident beam to the reflection element, and the reflection element configured to couple the second beam into the second waveguide at the second incident angle. The device according to any one of Examples 1c to 7c.

[0106] Example 9c: The device according to any one of Examples 1c to 8c, wherein when viewed along the normal axis perpendicular to the first main surface of the first waveguide, the second main surface of the first waveguide, the first main surface of the second waveguide, and the second main surface of the second waveguide, the partial reflection element surrounds the reflection element.

[0107] Example 10c: The device according to any one of claims 1c to 9c, wherein when viewed along the normal axis perpendicular to the first main surface of the first waveguide, the second main surface of the first waveguide, the first main surface of the second waveguide, and the second main surface of the second waveguide, the partial reflection element and the reflection element at least partially overlap.

[0108] Example 11c: The device according to any one of Examples 1c to 10c, wherein when viewed along the normal axis perpendicular to the first main surface of the first waveguide, the second main surface of the first waveguide, the first main surface of the second waveguide, and the second main surface of the second waveguide, the partial reflection element and the reflection element do not overlap.

[0109] Example 12c: The device according to any one of Examples 8c to 11c, wherein the reflection element extends beyond the second main surface of the second waveguide.

[0110] Example 13c: The device according to any one of Examples 1c to 12c, wherein the coupling element includes a prism and a beam splitter, the prism is configured to refract an incident beam toward the beam splitter, the beam splitter is configured to split the refracted incident beam into a reflected beam and a transmitted beam, couple the reflected beam to the first waveguide, and couple the transmitted beam to the second waveguide, the reflected beam is the first beam, and the transmitted beam is the second beam.

[0111] Example 14c: The apparatus according to any one of Examples 1c to 13c, wherein the second beam passes through the first waveguide after being coupled and output from the second waveguide.

[0112] Example 15c: The apparatus according to any one of Examples 1c to 14c, wherein the separation layer includes an air gap or a low refractive index adhesive.

[0113] Example 16c: The apparatus according to any one of Examples 1c to 15c, wherein the coupling element is attached to ends of the first waveguide and the second waveguide.

[0114] Example 17c: The apparatus according to any one of Examples 1c to 16c, wherein the coupling element is formed in the same substrate as the first waveguide and the second waveguide.

[0115] Example 1d: An apparatus, comprising: a first waveguide including a first main surface and a second main surface of the first waveguide; a second waveguide including a first main surface and a second main surface of the second waveguide, wherein the first main surface of the second waveguide is separated from the second main surface of the first waveguide by a separation layer; a partial reflection element configured to couple a first beam to the first waveguide at a first incident angle greater than a critical angle of the first waveguide and to pass a part of the incident beam through the reflection element; a reflection element configured to couple a second beam to the second waveguide at a second incident angle greater than the first incident angle; a first facet group disposed in the first waveguide between the first main surface and the second main surface of the first waveguide and configured to couple and output the first beam from the first waveguide; and a second facet group disposed in the second waveguide between the first main surface and the second main surface of the second waveguide and configured to couple and output the second beam from the second waveguide.

[0116] Example 2d: The first incident angle is between 45 degrees and 55 degrees from the normal axis perpendicular to the first main surface of the first waveguide, the second main surface of the first waveguide, the first main surface of the second waveguide, and the second main surface of the second waveguide, and the second incident angle is between 55 degrees and 89 degrees from the normal axis, the apparatus according to Example 1d.

[0117] Example 3d: The first facet group is arranged at a first facet angle with respect to the normal axis perpendicular to the first main surface of the first waveguide, the second main surface of the first waveguide, the first main surface of the second waveguide, and the second main surface of the second waveguide, and the second facet group is arranged at a second facet angle with respect to the normal axis, the apparatus according to Example 1d or 2d.

[0118] Example 4d: The first facet angle is different from the second facet angle, the apparatus according to any one of Examples 1d to 3d.

[0119] Example 5d: The first facet angle is larger than the second facet angle, the apparatus according to any one of Examples 1d to 4d.

[0120] Example 6d: The first main surface of the first waveguide, the second main surface of the first waveguide, the first main surface of the second waveguide, and the second main surface of the second waveguide extend along the facet axis, the first waveguide and the second waveguide are overlapped along the normal axis perpendicular to the facet axis, the first facet group is arranged in the first waveguide at a first position along the facet axis, and at least a part of the second facet group is arranged in the second waveguide at a second position along the facet axis different from the first position along the facet axis, the apparatus according to any one of Examples 1d to 5d.

[0121] Example 7d: The second position along the facet axis is farther from the coupling element than the first position along the facet axis, the apparatus according to any one of Examples 1d to 6d.

[0122] Example 8d: Further comprising a third facet group disposed in the second waveguide between the first main surface and the second main surface of the second waveguide, and configured to couple and output the second beam from the second waveguide, at least a part of the third facet group is disposed in the second waveguide at a third position along the facet axis different from the first position along the facet axis, the apparatus according to any one of Examples 1d to 7d.

[0123] Example 9d: The third position along the facet axis is closer to the coupling element than the first position along the facet axis, the apparatus according to any one of Examples 1d to 8d.

[0124] Example 10d: Further comprising a third facet group disposed in the second waveguide between the first main surface and the second main surface of the second waveguide, and configured to couple and output the second beam from the second waveguide, the first main surface of the first waveguide, the second main surface of the first waveguide, the first main surface of the second waveguide, and the second main surface of the second waveguide extend along the facet axis, the first waveguide and the second waveguide are overlapped along a normal axis perpendicular to the facet axis, the first facet group is disposed in the first waveguide at a first position along the facet axis, at least a part of the second facet group is disposed in the second waveguide at a second position along the facet axis different from the first position along the facet axis, at least a part of the third facet group is disposed in the second waveguide at a third position along the facet axis different from the first position along the facet axis, the first position along the facet axis is between the second position along the facet axis and the third position along the facet axis, the apparatus according to any one of Examples 1d to 9d.

[0125] Example 11d: The apparatus according to any one of Examples 1d to 10d, further comprising a homogenizer configured to replicate the second beam that is disposed in the second waveguide between the coupling element and the second facet group and is effective to increase the number of beams reflected in the second waveguide and incident on the second facet group.

[0126] Example 12d: The apparatus according to any one of Examples 1d to 11d, wherein the partial reflection element coincides with the reflection element when viewed along the normal axis perpendicular to the first main surface of the first waveguide, the second main surface of the first waveguide, the first main surface of the second waveguide, and the second main surface of the second waveguide.

[0127] Example 13d: The apparatus according to any one of Examples 1d to 12d, wherein the partial reflection element surrounds the reflection element when viewed along the normal axis perpendicular to the first main surface of the first waveguide, the second main surface of the first waveguide, the first main surface of the second waveguide, and the second main surface of the second waveguide.

[0128] Example 14d: The apparatus according to any one of Examples 1d to 13d, wherein the partial reflection element and the reflection element at least partially overlap when viewed along the normal axis perpendicular to the first main surface of the first waveguide, the second main surface of the first waveguide, the first main surface of the second waveguide, and the second main surface of the second waveguide.

[0129] Example 15d: The apparatus according to any one of Examples 1d to 14d, wherein the partial reflection element and the reflection element do not overlap when viewed along the normal axis perpendicular to the first main surface of the first waveguide, the second main surface of the first waveguide, the first main surface of the second waveguide, and the second main surface of the second waveguide.

[0130] Example 16d: The apparatus according to any one of Examples 1d to 15d, wherein the reflection element extends beyond the second main surface of the second waveguide.

[0131] Example 17d: The apparatus according to any one of Embodiments 1d to 16d, wherein the second beam passes through the first waveguide after being coupled and output from the second waveguide.

[0132] Embodiment 18d: The apparatus according to any one of Embodiments 1d to 17d, wherein the separation layer includes an air gap or a low refractive index adhesive.

[0133] Embodiment 19d: The apparatus according to any one of Embodiments 1d to 18d, wherein the coupling element is attached to the ends of the first waveguide and the second waveguide.

[0134] Embodiment 20d: The apparatus according to any one of Embodiments 1d to 19d, wherein the coupling element is formed in the same substrate as the first waveguide and the second waveguide.

[0135] Embodiment 1e: An apparatus comprising: a first waveguide including a first main surface and a second main surface of the first waveguide; a second waveguide including a first main surface and a second main surface of the second waveguide, wherein the first main surface of the second waveguide is separated from the second main surface of the first waveguide by a separation layer; a first reflecting element configured to couple a first portion of an incident beam as a first beam to the first waveguide at a first incident angle greater than a critical angle of the first waveguide; a second reflecting element configured to couple a second portion of the incident beam as a second beam to the second waveguide at a second incident angle greater than the first incident angle; a coupling element including the first reflecting element and the second reflecting element; a first facet group disposed in the first waveguide between the first main surface and the second main surface of the first waveguide and configured to couple and output the first beam from the first waveguide; and a second facet group disposed in the second waveguide between the first main surface and the second main surface of the second waveguide and configured to couple and output the second beam from the second waveguide.

[0136] Embodiment 2e: The first incident angle is between 45 degrees and 55 degrees with respect to the normal axis perpendicular to the first main surface of the first waveguide, the second main surface of the first waveguide, the first main surface of the second waveguide, and the second main surface of the second waveguide, and the second incident angle is between 55 degrees and 89 degrees with respect to the normal axis, the device according to Example 1e.

[0137] Example 3e: The first facet group is arranged at a first facet angle with respect to the normal axis perpendicular to the first main surface of the first waveguide, the second main surface of the first waveguide, the first main surface of the second waveguide, and the second main surface of the second waveguide, and the second facet group is arranged at a second facet angle with respect to the normal axis, the device according to Example 1e or 2e.

[0138] Example 4e: The first facet angle is different from the second facet angle, the device according to any one of Examples 1e to 3e.

[0139] Example 5e: The first facet angle is larger than the second facet angle, the device according to any one of Examples 1e to 4e.

[0140] Example 6e: The first main surface of the first waveguide, the second main surface of the first waveguide, the first main surface of the second waveguide, and the second main surface of the second waveguide extend along the facet axis, the first waveguide and the second waveguide are overlapped along the normal axis perpendicular to the facet axis, the first facet group is arranged in the first waveguide at a first position along the facet axis, and at least a part of the second facet group is arranged in the second waveguide at a second position along the facet axis different from the first position along the facet axis, the device according to any one of Examples 1e to 5e.

[0141] Example 7e: The second position along the facet axis is farther from the coupling element than the first position along the facet axis, the device according to any one of Examples 1e to 6e.

[0142] Example 8e: An apparatus according to any one of Examples 1e to 7e, further comprising a homogenizer configured to replicate the second beam, which is disposed in the second waveguide between the coupling element and the second facet group and is effective to increase the number of beams reflected in the second waveguide and incident on the second facet group.

[0143] Example 9e: An apparatus according to any one of Examples 1e to 8e, wherein the partial reflection element and the reflection element do not overlap when viewed along a normal axis perpendicular to the first major surface of the first waveguide, the second major surface of the first waveguide, the first major surface of the second waveguide, and the second major surface of the second waveguide.

[0144] Example 10e: An apparatus according to any one of Examples 1e to 9e, wherein the reflection element extends beyond the second major surface of the second waveguide.

[0145] Example 11e: An apparatus according to any one of Examples 1e to 10e, wherein the second beam passes through the first waveguide after being coupled and output from the second waveguide.

[0146] Example 12e: An apparatus according to any one of Examples 1e to 11e, wherein the separation layer includes an air gap or a low refractive index adhesive.

[0147] Example 13e: An apparatus according to any one of Examples 1e to 12e, wherein the coupling element is attached to the ends of the first waveguide and the second waveguide.

[0148] Example 14e: An apparatus according to any one of Examples 1e to 13e, wherein the coupling element is formed in the same substrate as the first waveguide and the second waveguide.

[0149] Example 1f: An apparatus, comprising: a first waveguide including a first major surface and a second major surface of the first waveguide; a second waveguide including a first major surface and a second major surface of the second waveguide, wherein the first major surface of the second waveguide is separated from the second major surface of the first waveguide by a separation layer; a coupling element configured to couple a first beam to the first waveguide at an incident angle greater than a critical angle of the first waveguide and couple a second beam to the second waveguide at the incident angle, the coupling element including a beam splitter configured to split an incident beam into a reflected beam and a transmitted beam, and couple the reflected beam to the first waveguide as the first beam and couple the transmitted beam to the second waveguide as the second beam; a first facet group disposed within the first waveguide between the first major surface and the second major surface of the first waveguide and configured to couple and output the first beam from the first waveguide; and a second facet group disposed within the second waveguide between the first major surface and the second major surface of the second waveguide and configured to couple and output the second beam from the second waveguide.

[0150] Example 2f: The apparatus according to Example 1a, wherein the first incident angle is between 45 degrees and 55 degrees from a normal axis perpendicular to the first major surface and the second major surface of the first waveguide.

[0151] Example 3f: The apparatus according to Example 1a or 2a, wherein the first facet group and the second facet group are arranged at a facet angle with respect to a normal axis perpendicular to the first major surface and the second major surface of the first waveguide, the first major surface and the second major surface of the second waveguide.

[0152] Example 4f: The apparatus according to any one of Examples 1f to 3f, wherein the second beam reflects the first beam with respect to the plane of the beam splitter.

[0153] Example 5f: The beam splitter is parallel to the first main surface of the first waveguide, the second main surface of the first waveguide, the first main surface of the second waveguide, and the second main surface of the second waveguide, and the device according to any one of Embodiments 1f to 4f.

[0154] Embodiment 6f: After the second beam is coupled and output from the second waveguide, it passes through the first waveguide, and the device according to any one of Embodiments 1f to 5f.

[0155] Embodiment 7f: The separation layer includes an air gap or a low refractive index adhesive, and the device according to any one of Embodiments 1f to 6f.

[0156] Embodiment 8f: The coupling element is attached to the ends of the first waveguide and the second waveguide, and the device according to any one of Embodiments 1f to 7f.

[0157] Embodiment 9f: The coupling element is formed in the same substrate as the first waveguide and the second waveguide, and the device according to any one of Embodiments 1f to 8f.

[0158] The coupling element may include a prism and a beam splitter. The prism may be configured to refract the incident beam towards the beam splitter. The beam splitter may be configured to split the refracted incident beam into a reflected beam and a transmitted beam, couple the reflected beam to the first waveguide, and couple the transmitted beam to the second waveguide. The reflected beam may be the first beam, and the transmitted beam may be the second beam. This device may also include a first facet group disposed in the first waveguide between the first main surface of the first waveguide and the second main surface of the first waveguide and configured to couple and output the first beam from the first waveguide. This device may also include a second facet group disposed in the second waveguide between the first main surface of the second waveguide and the second main surface of the second waveguide.

[0159] Embodiment 1g: An apparatus, comprising: a first waveguide including a first main surface and a second main surface of the first waveguide; a second waveguide including a first main surface and a second main surface of the second waveguide, wherein the first main surface of the second waveguide is separated from the second main surface of the first waveguide by a separation layer; a coupling element configured to couple a first beam to the first waveguide at a first incident angle greater than the critical angle of the first waveguide and to couple a second beam to the second waveguide at a second incident angle greater than the first incident angle, the coupling element including a prism and a beam splitter, the prism being configured to refract an incident beam toward the beam splitter, the beam splitter being configured to split the refracted incident beam into a reflected beam and a transmitted beam, and to couple the reflected beam as the second beam to the second waveguide and the transmitted beam as the first beam to the first waveguide; a first facet group disposed within the first waveguide between the first main surface and the second main surface of the first waveguide and configured to couple and output the first beam from the first waveguide; and a second facet group disposed within the second waveguide between the first main surface and the second main surface of the second waveguide and configured to couple and output the second beam from the second waveguide.

[0160] Example 2g: The apparatus according to Example 1g, wherein the first incident angle is between 45 degrees and 55 degrees from a normal axis perpendicular to the first main surface of the first waveguide, the second main surface of the first waveguide, the first main surface of the second waveguide, and the second main surface of the second waveguide, and the second incident angle is between 55 degrees and 89 degrees from the normal axis.

[0161] Example 3g: The apparatus according to Example 1g or 2g, wherein the first facet group is disposed at a first facet angle with respect to a normal axis perpendicular to the first main surface of the first waveguide, the second main surface of the first waveguide, the first main surface of the second waveguide, and the second main surface of the second waveguide, and the second facet group is disposed at a second facet angle with respect to the normal axis.

[0162] Example 4g: The apparatus according to any one of Examples 1g to 3g, wherein the first facet angle is different from the second facet angle.

[0163] Example 5g: The apparatus according to any one of Examples 1g to 4g, wherein the first facet angle is larger than the second facet angle.

[0164] Example 6g: The first main surface of the first waveguide, the second main surface of the first waveguide, the first main surface of the second waveguide, and the second main surface of the second waveguide extend along the facet axis, the first waveguide and the second waveguide are overlapped along a normal axis orthogonal to the facet axis, the first facet group is disposed in the first waveguide at a first position along the facet axis, and at least a part of the second facet group is disposed in the second waveguide at a second position along the facet axis different from the first position along the facet axis. The apparatus according to any one of Examples 1g to 5g.

[0165] Example 7g: The apparatus according to any one of Examples 1g to 6g, wherein the second position along the facet axis is farther from the coupling element than the first position along the facet axis.

[0166] Example 8g: The apparatus according to any one of Examples 1g to 7g, further including a homogenizer configured to replicate the second beam effective to increase the number of beams that are disposed in the second waveguide between the coupling element and the second facet group and are reflected in the second waveguide and incident on the second facet group.

[0167] Example 9g: The coupling element includes a prism and a beam splitter. The prism is configured to refract an incident beam toward the beam splitter. The beam splitter is configured to split the refracted incident beam into a reflected beam and a transmitted beam, couple the reflected beam to the first waveguide, and couple the transmitted beam to the second waveguide. The reflected beam is the first beam, and the transmitted beam is the second beam. The apparatus according to any one of Examples 1g to 8g.

[0168] Example 10g: The first beam passes through the first waveguide after being coupled and output from the second waveguide. The apparatus according to any one of Examples 1g to 9g.

[0169] Example 11g: The separation layer includes an air gap or a low refractive index adhesive. The apparatus according to any one of Examples 1g to 10g.

[0170] Example 12g: The coupling element is attached to the ends of the first waveguide and the second waveguide. The apparatus according to any one of Examples 1g to 11g.

[0171] Example 13g: The coupling element is formed in the same substrate as the first waveguide and the second waveguide. The apparatus according to any one of Examples 1g to 12g.

[0172] Example 14g: The angle of the incident beam is not perpendicular to the first main surface of the first waveguide, the second main surface of the first waveguide, the first main surface of the second waveguide, and the second main surface of the second waveguide. The apparatus according to any one of Examples 1g to 13g.

[0173] Example 15g: The beam splitter is not parallel to the first main surface of the first waveguide, the second main surface of the first waveguide, the first main surface of the second waveguide, and the second main surface of the second waveguide. The apparatus according to any one of Examples 1g to 14g.

[0174] Example 16g: The beam splitter is disposed between the first main surface and the second main surface of the second waveguide, and the device according to any one of Examples 1g to 15g.

[0175] Example 1h: A device, comprising: a first waveguide including a first main surface and a second main surface of the first waveguide; a second waveguide including a first main surface and a second main surface of the second waveguide, wherein the first main surface of the second waveguide is separated from the second main surface of the first waveguide by a separation layer; a coupling element configured to couple a first portion of an incident beam as a first beam to the first waveguide at an incident angle greater than the critical angle of the first waveguide, and couple a second portion of the incident beam as a second beam to the second waveguide at the incident angle to generate a second beam; a first facet group disposed in the first waveguide between the first main surface and the second main surface of the first waveguide, configured to partially reflect the first beam to generate a reflected beam at an incident angle smaller than the first incident angle and a transmitted beam at the first incident angle, and couple and output the reflected beam outside the first waveguide; and a second facet group disposed in the second waveguide between the first main surface and the second main surface of the second waveguide, configured to couple and output the second beam from the second waveguide.

[0176] Example 2h: The incident angle is between 45 degrees and 55 degrees with respect to the normal axis perpendicular to the first main surface of the first waveguide, the second main surface of the first waveguide, the first main surface of the second waveguide, and the second main surface of the second waveguide, and the device according to Example 1h.

[0177] Example 3h: The first facet group is disposed at a first facet angle with respect to the normal axis perpendicular to the first main surface of the first waveguide, the second main surface of the first waveguide, the first main surface of the second waveguide, and the second main surface of the second waveguide, and the second facet group is disposed at a second facet angle with respect to the normal axis, and the device according to Example 1h or 2h.

[0178] Example 4h: The apparatus according to any one of Examples 1h to 3h, wherein the first facet angle is different from the second facet angle.

[0179] Example 5h: The apparatus according to any one of Examples 1h to 4h, wherein the first facet angle is larger than the second facet angle.

[0180] Example 6h: The first main surface of the first waveguide, the second main surface of the first waveguide, the first main surface of the second waveguide, and the second main surface of the second waveguide extend along the facet axis, the first waveguide and the second waveguide are superposed along the normal axis orthogonal to the facet axis, the first facet group is disposed in the first waveguide at a first position along the facet axis, and at least a part of the second facet group is disposed in the second waveguide at a second position along the facet axis different from the first position along the facet axis. The apparatus according to any one of Examples 1h to 5h.

[0181] Example 7h: The apparatus according to any one of Examples 1h to 6h, wherein the second position along the facet axis is farther from the coupling element than the first position along the facet axis.

[0182] Example 8h: The apparatus according to any one of Examples 1h to 7h, further including a homogenizer configured to replicate the second beam effective to increase the number of beams that are disposed in the second waveguide between the coupling element and the second facet group and are reflected in the second waveguide and incident on the second facet group.

[0183] Example 9h: The apparatus according to any one of Examples 1h to 8h, wherein the coupling element includes a reflective element.

[0184] Example 10h: The device according to any one of Examples 1h to 9h, wherein the reflection element does not extend beyond the second main surface of the second waveguide.

[0185] Example 11h: The device according to any one of Examples 1h to 10h, wherein the second beam passes through the first waveguide after being coupled and output from the second waveguide.

[0186] Example 12h: The device according to any one of Examples 1h to 11h, wherein the separation layer includes an air gap or a low refractive index adhesive.

[0187] Example 13h: The device according to any one of Examples 1h to 12h, wherein the coupling element is attached to the ends of the first waveguide and the second waveguide.

[0188] Example 14h: The device according to any one of Examples 1h to 13h, wherein the coupling element is formed in the same substrate as the first waveguide and the second waveguide.

Claims

1. An apparatus comprising: a first waveguide including a first major surface and a second major surface of the first waveguide extending along a facet axis; a second waveguide including a first major surface and a second major surface of the second waveguide extending along the facet axis, wherein the first major surface of the second waveguide is separated from the second major surface of the first waveguide by a separation layer; the first waveguide and the second waveguide being overlapped along a normal axis orthogonal to the facet axis; a coupling element configured to couple a first portion of an incident beam as a first beam to the first waveguide at a first incident angle greater than a critical angle of the first waveguide; a coupling element configured to couple a second portion of the incident beam as a second beam to the second waveguide at a second incident angle greater than the first incident angle; a first facet group disposed within the first waveguide between the first major surface and the second major surface of the first waveguide at a first position along the facet axis, the first facet group being configured to couple and output the first beam from the first waveguide; a second facet group disposed within the second waveguide between the first major surface and the second major surface of the second waveguide at a second position along the facet axis different from the first position along the facet axis, the second facet group being configured to couple and output the second beam from the second waveguide.

2. The first incident angle is between 45 degrees and 55 degrees from a normal axis perpendicular to the first major surface of the first waveguide, the second major surface of the first waveguide, the first major surface of the second waveguide, and the second major surface of the second waveguide; The second incident angle is between 55 degrees and 89 degrees from the normal axis. The apparatus according to claim 1.

3. The first facet group is disposed at a first facet angle with respect to a normal axis perpendicular to the first major surface of the first waveguide, the second major surface of the first waveguide, the first major surface of the second waveguide, and the second major surface of the second waveguide; The second facet group is disposed at a second facet angle different from the first facet angle with respect to the normal axis. The apparatus according to claim 1.

4. The first facet angle is greater than the second facet angle. The apparatus according to claim 3.

5. The second position along the facet axis is farther from the coupling element than the first position along the facet axis. The apparatus according to claim 1.

6. Further comprising a third facet group disposed in the second waveguide between the first main surface of the second waveguide and the second main surface of the second waveguide, and configured to couple and output the second beam from the second waveguide. The apparatus according to claim 1, wherein the third facet group is disposed in the second waveguide at a third position along the facet axis different from the first position along the facet axis.

7. The apparatus according to claim 6, wherein the third position along the facet axis is closer to the coupling element than the first position along the facet axis.

8. The apparatus according to claim 6, wherein the first position along the facet axis is between the second position along the facet axis and the third position along the facet axis.

9. Further comprising a homogenizer disposed in the second waveguide between the coupling element and the second facet group along the facet axis, and configured to replicate the second beam effective to increase the number of beams reflected in the second waveguide and incident on the second facet group. The apparatus according to claim 1.

10. The coupling element Includes a partial reflection element configured to generate the first beam, couple the first beam to the first waveguide at the first incident angle, and pass a part of the incident beam to the reflection element. The apparatus according to claim 1, wherein the reflection element is configured to couple a part of the incident beam to the second waveguide as the second beam at the second incident angle.

11. The apparatus according to claim 10, wherein the partial reflection element coincides with the reflection element when viewed along the normal axis.

12. The apparatus according to claim 10, wherein the partial reflection element surrounds the reflection element when viewed along the normal axis.

13. The apparatus according to claim 10, wherein the partial reflection element and the reflection element at least partially overlap when viewed along the normal axis.

14. The apparatus according to claim 10, wherein the partial reflection element and the reflection element do not overlap when viewed along the normal axis.

15. The apparatus according to claim 10, wherein the reflection element extends beyond the second main surface of the second waveguide.

16. The coupling element includes a prism and a beam splitter. The prism is configured to refract the incident beam toward the beam splitter. The beam splitter The refracted incident beam is split into a reflected beam and a transmitted beam, the reflected beam is coupled to the first waveguide, the transmitted beam is coupled to the second waveguide, the reflected beam is the first beam, The apparatus according to claim 1, wherein the transmitted beam is the second beam.

17. The apparatus according to claim 1, wherein the second beam passes through the first waveguide after being coupled and output from the second waveguide.

18. The apparatus according to claim 1, wherein the separation layer includes an air gap or a low refractive index adhesive.

19. An apparatus, a first waveguide including a first main surface of the first waveguide extending along a facet axis and a second main surface of the first waveguide, a second waveguide including a first main surface of the second waveguide extending along the facet axis and a second main surface of the second waveguide, wherein the first main surface of the second waveguide is separated from the second main surface of the first waveguide by a separation layer, the first waveguide and the second waveguide are overlapped along a normal axis orthogonal to the facet axis, a second waveguide, receives an incident beam, generates a first beam and a second beam from the incident beam, couples the first beam to the first waveguide at a first incident angle greater than the critical angle of the first waveguide, a coupling element configured to couple the second beam to the second waveguide at a second incident angle greater than the first incident angle, a first facet group disposed in the first waveguide between the first main surface of the first waveguide and the second main surface of the first waveguide at a first position along the facet axis, and configured to couple and output the first beam from the first waveguide, a second facet group disposed in the second waveguide between the first main surface of the second waveguide and the second main surface of the second waveguide at a second position along the facet axis different from the first position along the facet axis, and configured to couple and output the second beam from the second waveguide, a third facet group disposed in the second waveguide between the first main surface of the second waveguide and the second main surface of the second waveguide at a third position along the facet axis different from the first position and the second position along the facet axis, and configured to couple and output the second beam from the second waveguide, The apparatus, wherein the first position along the facet axis is between the second position along the facet axis and the third position along the facet axis.

20. The first facet group is arranged at a first facet angle, The apparatus according to claim 19, wherein the second facet group and the third facet group are arranged at a second facet angle different from the first facet angle.

21. The coupling element is a partial reflection element arranged in the same substrate as the first waveguide, and a reflection element at least partially arranged in the same substrate as the second waveguide, the apparatus according to claim 19.

22. The apparatus according to claim 21, wherein the partial reflection element coincides with the reflection element when viewed along the normal axis.

23. An apparatus comprising a first waveguide including a first main surface of the first waveguide extending along a facet axis and a second main surface of the first waveguide, a second waveguide including a first main surface of the second waveguide extending along the facet axis and a second main surface of the second waveguide, wherein the first main surface of the second waveguide is separated from the second main surface of the first waveguide by a separation layer, the first waveguide and the second waveguide being overlapped along a normal axis orthogonal to the facet axis, a second waveguide, receiving an incident beam, generating a first beam and a second beam from the incident beam, coupling the first beam to the first waveguide at a first incident angle greater than the critical angle of the first waveguide, a coupling element configured to couple the second beam to the second waveguide at a second incident angle greater than the first incident angle, a first facet group arranged in the first waveguide between the first main surface and the second main surface of the first waveguide at a first position along the facet axis, and configured to couple and output the first beam from the first waveguide, a second facet group arranged in the second waveguide between the first main surface and the second main surface of the second waveguide at a second position along the facet axis different from the first position along the facet axis, and a homogenizer arranged in the second waveguide between the coupling element and the second facet group along the facet axis, wherein the coupling element is between the first main surface of the first waveguide and the second main surface of the second waveguide, the homogenizer being configured to replicate the second beam effective to increase the number of beams reflected in the second waveguide and incident on the second facet group. The apparatus, wherein the second facet group is configured to couple and output the beam from the homogenizer reflected within the second waveguide outside the second waveguide.

24. The coupling element is disposed between a first main surface of the first waveguide and a second main surface of the first waveguide, generates the first beam, couples the first beam to the first waveguide at the first incident angle, and includes a partial reflection element configured to pass a part of the incident beam to a reflection element. The apparatus according to claim 23, wherein the reflection element is disposed between a first main surface of the second waveguide and a second main surface of the second waveguide, and is configured to couple a part of the incident beam to the second waveguide as the second beam at the second incident angle.

25. The apparatus according to claim 24, wherein the partial reflection element surrounds the reflection element when viewed along the normal axis.

26. The apparatus according to claim 24, wherein the partial reflection element is disposed within the same substrate as the first waveguide. The apparatus according to claim 24, wherein the reflection element is disposed within the same substrate as the second waveguide.

27. An apparatus including a first waveguide including a first main surface of the first waveguide extending along a facet axis and a second main surface of the first waveguide, a second waveguide including a first main surface of the second waveguide extending along the facet axis and a second main surface of the second waveguide, wherein the first main surface of the second waveguide is separated from the second main surface of the first waveguide by a separation layer, the first waveguide and the second waveguide are overlapped along a normal axis orthogonal to the facet axis, a coupling element configured to couple a first beam to the first waveguide at an incident angle greater than a critical angle of the first waveguide, and to couple a second beam to the second waveguide at the incident angle, receives an incident beam at the incident angle, splits the incident beam into a reflected beam and a transmitted beam, couples the reflected beam to the first waveguide as the first beam, and includes a beam splitter configured to couple the transmitted beam to the second waveguide as the second beam, and a first facet group disposed within the first waveguide between the first main surface of the first waveguide and the second main surface of the first waveguide, and configured to couple and output the first beam from the first waveguide. A second facet group disposed within the second waveguide between a first major surface of the second waveguide and a second major surface of the second waveguide and configured to couple and output the second beam from the second waveguide.

28. The apparatus according to claim 27, wherein the beam splitter is disposed between a second major surface of the first waveguide and a first major surface of the second waveguide.

29. The apparatus according to claim 27, wherein the first facet group and the second facet group share a facet angle.

30. The apparatus according to claim 27, wherein the first facet group and the second facet group are aligned along the facet axis.

31. An apparatus, A first waveguide including a first major surface of the first waveguide extending along a facet axis and a second major surface of the first waveguide, A second waveguide including a first major surface of the second waveguide extending along the facet axis and a second major surface of the second waveguide, The first major surface of the second waveguide is separated from the second major surface of the first waveguide by a separation layer, The first waveguide and the second waveguide are overlapped along a normal axis orthogonal to the facet axis, a second waveguide, Coupling a first beam to the first waveguide at a first incident angle greater than a critical angle of the first waveguide, A coupling element configured to couple a second beam to the second waveguide at a second incident angle greater than the first incident angle, The coupling element includes a prism and a beam splitter, The prism is configured to refract an incident beam toward the beam splitter, The beam splitter, Receiving the refracted incident beam at an incident angle, Dividing the refracted incident beam into a reflected beam and a transmitted beam, Coupling the reflected beam to the second waveguide as the second beam at the second incident angle, A coupling element configured to couple the transmitted beam to the first waveguide as the first beam at the first incident angle, A first facet group disposed within the first waveguide between a first major surface of the first waveguide and a second major surface of the first waveguide at a first position along the facet axis and configured to couple and output the first beam from the first waveguide. A second facet group that is disposed in the second waveguide between a first main surface and a second main surface of the second waveguide at a second position along the facet axis that is different from the first position along the facet axis, and that is configured to couple and output the second beam from the second waveguide, and an apparatus including the same.

32. The apparatus according to claim 31, further including a homogenizer disposed in the second waveguide between the coupling element and the second facet group along the facet axis.

33. The apparatus according to claim 31, wherein the beam splitter extends from a first main surface of the first waveguide to a second main surface of the first waveguide.

34. An apparatus, comprising: a first waveguide including a first main surface and a second main surface of the first waveguide that extend along a facet axis; a second waveguide including a first main surface and a second main surface of the second waveguide that extend along the facet axis, wherein the first main surface of the second waveguide is separated from the second main surface of the first waveguide by a separation layer; the first waveguide and the second waveguide are overlapped along a normal axis orthogonal to the facet axis; a coupling element that receives an incident beam and couples a first portion of the incident beam as a first beam to the first waveguide at an incident angle greater than a critical angle of the first waveguide; a reflection element configured to couple a second portion of the incident beam as a second beam to the second waveguide at the incident angle to generate a second beam; a first facet group that is disposed in the first waveguide between the first main surface and the second main surface of the first waveguide at a first position along the facet axis, partially reflects the first beam, generates a reflected beam having an incident angle smaller than the first incident angle and a transmitted beam having the first incident angle, and is configured to couple and output the reflected beam from the first waveguide; a first facet group that is disposed in the second waveguide between the first main surface and the second main surface of the second waveguide at a second position along the facet axis, and is configured to couple and output the second beam from the second waveguide, and an apparatus including the same.

35. The apparatus according to claim 34, further including a homogenizer disposed in the second waveguide between the coupling element and the second facet group along the facet axis.

36. The device according to claim 34, wherein the reflection element extends from a first main surface of the first waveguide to a second main surface of the second waveguide.

37. The device according to claim 34, wherein the coupling element is attached to ends of the first waveguide and the second waveguide.

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