Scatter mitigation structure for photonic integrated circuits

Abstract

A photonic circuit can include a first area with a photonic element and a second area with a waveguide optically connected to the photonic element. The photonic circuit can include a scatter mitigation shell comprising a metallic enclosure to shield the first area from scattered light, the metallic enclosure comprising at least one elliptical arc-shaped boundary to prevent light scattered into the scatter mitigation shell from reaching a given region within the first area, the photonic element being positioned in the given region.

Description

SCATTER MITIGATION STRUCTUREFOR PHOTONIC INTEGRATED CIRCUITSCLAIM OF PRIORITY

[0001] This application claims the benefit of priority to U.S. Patent Application Serial No. 63 / 776,823, filed on March 24, 2025, which is incorporated by reference herein in its entirety.TECHNICAL FIELD

[0002] The present disclosure generally relates to photonic circuits, and more particularly to shielding photonic elements from stray light.BACKGROUND

[0003] A photonic circuit can comprise a first area comprising a photonic element and a second area comprising a waveguide optically connected to the photonic element. The photonic element can comprise a detector. In some applications, such as high-performance optical networking and quantum-optics based logic devices (e.g., photonic quantum computers), background light scatter can be a source of noise on the detector and degrade optical performance.BRIEF DESCRIPTION OF THE DRAWINGS

[0004] The following description includes discussion of figures having illustrations given by way of example of implementations of embodiments of the disclosure. The drawings should be understood by way of example, and not by way of limitation. As used herein, references to one or more "embodiments" are to be understood as describing a particular feature, structure, or characteristic included in at least one implementation of the inventive subject matter. Thus, phrases such as "in one embodiment" or "in an alternate embodiment" appearing herein describe various embodiments and implementations of the inventive subject matter, and do not necessarilyall refer to the same embodiment. However, they are also not necessarily mutually exclusive. To easily identify the discussion of any particular element or act, the most significant digit or digits in a reference number refer to the figure (‘TIG ”) number in which that element or act is first introduced.

[0005] FIG. 1 illustrates an edge coupling arrangement for a photonic integrated circuit (PIC), in accordance with some examples.

[0006] FIG. 2 illustrates a cross-section of a PIC having a scatter mitigation shield that surrounds a waveguide optically coupled to a detector, in accordance with some examples.

[0007] FIG. 3 illustrates the geometric optical properties of an ellipse, in accordance with some examples.

[0008] FIG. 4 illustrates an elliptical scatter shield with an entrance and exit, in accordance with some examples.

[0009] FIG. 5 illustrates regions of scattered light in an elliptical scatter shield, in accordance with some examples.

[0010] FIG. 6 illustrates a PIC integrating an elliptical scatter shield, in accordance with some examples.

[0011] FIG. 7 illustrates a multiple ellipse scatter shield, in accordance with some examples.

[0012] FIG. 8 illustrates a portion of a PIC integrating the multiple ellipse scatter shield, in accordance with some examples.

[0013] Descriptions of certain details and implementations follow, including a description of the figures, which may depict some or all of the embodiments described below, as well as discussing other potential embodiments or implementations of the inventive concepts presented herein. An overview of embodiments of the disclosure is provided below, followed by a more detailed description with reference to the drawings.DETAILED DESCRIPTION

[0014] In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide an understanding of various embodiments of the inventive subject matter. It will be evident, however, to those skilled in the art, that embodiments of the inventive subject matter may be practiced without these specific details. In general, well-known instruction instances, structures, and techniques are not necessarily shown in detail.

[0015] In some examples, a photonic integrated circuit (PIC) is disclosed, comprising a first area containing a photonic element and a second area with a waveguide that is optically connected to the photonic element. The PIC includes a scatter mitigation shell featuring a metallic enclosure designed to shield the photonic element from scattered light, ensuring that light scattered into the shell does not reach a specific region where the photonic element is located.

[0016] The use of an elliptical arc-shaped boundary in the scatter mitigation shell leverages the geometric properties of ellipses to control the trajectory of scattered light. This geometric property may provide a region of the scatter mitigation shell with low scatter, thus preventing interference with the photonic element, such as a detector, thereby reducing noise and enhancing the signal -to-noise ratio. This provides a practical solution to the problem of scattered light in photonic circuits, which is important for applications requiring high precision and low noise, such as quantum computing systems.

[0017] The scattered light entering the scatter mitigation shell may originate from a light source coupled to the waveguide, such as a laser configured to enter the waveguide at an edge coupler. Alternatively, the scattered light may emanate from sources not associated with the light source coupled to the waveguide. The metallic enclosure may include at least one opening, and the scatter mitigation shell may include an input channel with the waveguide positioned parallel to and within this input channel, oriented towards the elliptical arc-shaped boundary at the output of the input channel. Additionally, the scatter mitigation shell may comprise anoutput channel parallel to the input channel, with both channels oriented opposite the elliptical arc-shaped boundary. The output channel may be located at the designated region, with the waveguide positioned within the output channel, and may connect to a second input channel, where the waveguide is positioned parallel to and within the second input channel, further oriented towards a second elliptical arc-shaped boundary at the output of the second input channel.

[0018] In a further embodiment, at least one elliptical arc-shaped boundary is configured to control the trajectory of light scattered into the scatter mitigation shell, confining the light within the top half of the boundary. The photonic element may be a photon detector, with the scatter mitigation shell reducing background light at the photon detector and enhancing the signal-to-noise ratio compared to positioning the photon detector in other regions of the scatter mitigation shell. One of ordinary skill having the benefit of this disclosure will appreciate that the particular type of detector employed in the systems disclosed herein is not critical and can be chosen to be any type of number resolving photon detector, e.g., superconducting nanowire single photon detectors (SNSPD), transition edge sensors (TES), a charge integration photon detector (CIPD), single photon avalanche diodes (SPAD), avalanche photodiode (APD), and the like. In an example, one or more detectors can block the photon's path, i.e., they can be located directly in the optical path of the photon traveling in the waveguide. In an example, one or more detectors need not be directly in the optical path of the photon but instead can be located next to the waveguide (e.g., on top of or to the side of the waveguide) such that evanescent coupling of the photon into the detector is possible.

[0019] The scatter mitigation shell may also include a metallic ceiling covering the elliptical arc-shaped boundary and the first area, with a first elliptical arc-shaped boundary connected to a second elliptical arc-shaped boundary through an output channel in the first boundary positioned at the designated region. An output channel in the second elliptical arc-shaped boundary may be positioned at a second designated region. These and other aspects will be more clearly understood from the following detaileddescription taken in conjunction with the accompanying drawings and claims.

[0020] FIG. 1 shows an edge coupling arrangement 100 from a side perspective view, in accordance with some examples. In the example of FIG.1, a dimension legend 101 shows the three dimensions, X, Y, and Z, with respect to the following figures. For example, optical and electrical devices (e.g., PICs, electrical chips) can have a planar form in the XY plane, where the optical waveguides or electrical traces are laid out generally parallel (e.g., approximately parallel) to the XY plane. A given optical and / or electrical device may comprise multiple planar layers (e.g., different layers of silicon, cladding, and so on), where vertical paths (e.g., up / down, along the Z-axis) between different planar layers can be implemented by vias (e.g., to connect electrical paths) or internal PIC optical transitions (e.g., internal PIC tapers).

[0021] In FIG. 1, a PIC 120 is illustrated having a topside 122 extending laterally along the XY plane, and edges (e.g., sides, facets), such as edge 117, into which light can be coupled laterally along an input direction 125 (e.g., injection direction, parallel to the XY plane); although one of ordinary skill appreciates that light can be received out of the edge 117 in a direction opposite of the arrow of the input direction 125 (e.g., the PIC 120 couples, or transmits, light out to an external device, such as another PIC or fiber), in accordance with some examples.

[0022] In the example of FIG. 1, the edge coupling arrangement 100 shows an optical fiber 110 (e.g., single mode fiber (SMF), SMF-28 that is coupled to the PIC 120. One advantage of edge coupling is that it can be efficient: a given a topside or bottom-side of a PIC may be difficult to access or may not have space in the layout design for the addition of gratings or parallel -tapers implemented in evanescent-style coupling, whereas the edge or side of the PIC may be accessible in those same PIC designs. Additionally, edge coupling can provide very low loss optical coupling as compared to other approaches.

[0023] In the illustrated example, the optical fiber 110 includes a core 112 (e.g., core layer), and a cladding 114 (e.g., cladding layer) that surrounds thecore 112. The core 112 is configured to transmit light (e.g., radiation, visible light, UV radiation, IR radiation) along the length (e.g., along the axis) of the optical fiber 110. The optical fiber 110 may include any type of optical fiber. For example, the optical fiber 110 may comprise a glass optical fiber in which the core 112 comprises a glass layer, and the cladding 114 comprises a different glass layer having a lower refractive index than the core 112 such that the light is substantially confined and propagates in the core 112.

[0024] In some examples, the PIC 120 is an optical die or chip formed from planar layers of materials (e.g., silicon, silicon nitride, silicon dioxide, III-V materials, etc.) that have different refractive indices such that light can propagate in waveguides of the PIC 120. In the example of FIG. 1, the PIC 120 has a topside 122 and an edge 117, though it is appreciated by one of ordinary skill that the topside 122 is with respect to the view of FIG. 1. The topside 122 is planar and substantially parallel with the XY plane. The topside 122 is at an angle to the edge 117 (e.g., orthogonal, at 90 degrees). By axially aligning the core 112 of the optical fiber 110 and the waveguide 124 of the PIC 120, light can be coupled to and from the edge 117 in an edge coupling region 133. The optical fiber 110 may be positioned and axially aligned to the PIC 120 using one or more alignment techniques (e.g., active alignment, passive marker-based (fiduciary-based) placement and alignment), or by way of a fiber mount that holds the optical fiber 110 in position (e.g., a moveable fiber holder, a v-groove structure of a fiber holder chip).

[0025] In some examples, scattered light 130 may occur at the interface of the optical fiber 110 and the edge 117. The scattered light 130 may scatter into free space, that is, away from the PIC 120, and continue reflecting off additional surfaces. In another example, the scattered light 130 may scatter into the PIC 120, e.g., through the substrate. The scattered light 130 may be approximately isotropic. The scattered light 130 may reach the detection area where an electronic component 126 (e.g., sensitive photon detector) is optically coupled to waveguide 124 of the PIC 120. Any amount of scattered light 130 that reaches the detector may contribute a background amount of signal. In an example using heralded single photon sources, a single photondetector may have a specification for a scatter light extinction ratio of 140dB.

[0026] Note that although scattered light 130 is shown in the edge coupling of the optical fiber 110 and the PIC 120, any other suitable fiber coupling technique (gratings, tapers) may result in scattered light. Additionally, scattered light 130 may arise from any other sources of light within the PIC or from sources of light (free space or otherwise) outside of the PIC.

[0027] FIG. 2 illustrates a cross section 200 of a PIC comprising a scatter mitigation shield 202. The scatter mitigation shield 202 surrounds a waveguide 206, which is optically coupled to a detector 204. This arrangement can decrease the impact of scattered light on the detector 204, thereby improving the performance of the PIC.

[0028] In the context of a heralded single photon source (HSPS), achieving high performance requires engineered spontaneous four-wave mixing (SFWM) sources, heralding detectors, and a high-performance filter network in the PIC. To separate the bright laser pump from the single photons (e.g., arriving at the detector 204 through waveguide 206), approximately 100 dB suppression of the pump photons is necessary. This may be achieved in the PIC by combining interferometric in-guide filtering with shielding of the detectors from out-of-guide scattered pump light.

[0029] To suppress scattered light, the detectors are locally shielded by encasing them in metal, as shown in FIG. 2. The scatter mitigation shield 202 may be fabricated in the substrate 208 using deep and shallow metal-filled trenches and back-end-of-line metals, resulting in approximately 115 dB pump power suppression between the pump input and the superconducting nanowire single-photon detectors (SNSPDs) (e.g., detector 204).

[0030] The scatter mitigation shield 202 acts as a protective enclosure, preventing unwanted scattered light from reaching the detector 204. The waveguide 206 is optically connected to the detector 204, allowing for efficient light coupling and detection. The configuration of the waveguide 206, in conjunction with the scatter mitigation shield 202, ensures that thelight reaching the detector 204 is primarily the intended signal, with minimal interference from scattered light.

[0031] The scatter mitigation shield 202 may include openings for additional electronic traces to connect to the detector 204, and for the waveguide 206 to enter / exit the scatter mitigation shield 202. In some examples, such openings may introduce opportunities for scattered light to reach the detector 204, e.g., through the substrate 208, etc. Additional considerations for the structure of the scatter mitigation shield 202 may provide increased scattered light suppression.

[0032] FIG. 3 illustrates the geometric optical properties of an ellipse 300, in accordance with some examples. The ellipse 300 may have a right focal point 310 and left focal point 312. There are two geometric optical properties shown for light rays reflected inside the ellipse 300. The ray 302 originates (or otherwise passes through) the right focal point 310, and is reflected at reflection point 314 as ray 306. Ray 306 passes through the left focal point 312. Thus, a ray going through one focal point of an ellipse will pass through the remaining focal point upon reflection. Additionally, the ray 304 originates (or otherwise passes through) the right hand side of the right focal point 310 and is reflected at reflection point 314 as ray 308. Ray 308 propagates to the left side of the left focal point 312. Thus, a ray going from a given side of a given focal point will propagate to the complementary side of the complementary focal point. Such geometric properties of the ellipse 300 may be used to configure specific optical trajectories for an elliptical scatter shield.

[0033] FIG. 4 illustrates an elliptical scatter shield 400 with an entrance and exit, in accordance with some examples. The elliptical scatter shield 400 may include an entrance 402, an exit 404, an elliptical arc-shaped boundary 406, and a light trap 408. The entrance 402 may comprise an input channel with parallel sides and any suitable width. In an example, the entrance 402 may be aligned so that one of the input channel sides is an extension of the elliptical arc-shaped boundary 406. That is, the entrance may be positioned so that scattered light enters the elliptical scatter shield 400 at an offset from a focal point of an equivalent ellipse to the elliptical arc-shaped boundary406. The entrance 402 may be configured to have a photonic element (e.g., waveguide) in the input channel.

[0034] The exit 404 may comprise an exit channel with parallel sides and any suitable width. The sides of the exit channel may be parallel to the entrance 402 (e.g., the input channel is parallel to the exit channel). In an example, the exit 404 may be aligned at a central portion of the elliptical arc-shaped boundary 406. In particular, the exit 404 may be positioned in a low scatter region, as described below in FIG. 5. The exit 404 may be configured to have at least one photonic element (e.g., waveguide, detector, etc.) in the exit channel.

[0035] The elliptical arc-shaped boundary 406 may have any suitable radius of curvature and may connect the entrance 402 (e.g., the input channel) with the light trap 408. In an example, the light trap 408 may be comprise a channel that has an additional wall at the side of the channel opposite the elliptical arc-shaped boundary. In an example, the light trap 408 may be aligned so that one of the channel sides is an extension of the elliptical arc-shaped boundary 406.

[0036] As shown in FIG. 4, a bundle of light rays 410, 412, and 414 may scatter into the elliptical scatter shield 400 at the entrance 402. Through several reflections, the light rays 410, 412, and 414 do not propagate into the exit 404, based on the geometric reflection properties outlined in FIG. 3. That is, the inclusion of the elliptical arc-shaped boundary 406 can control the trajectories of the scattered light to avoid a particular region (e.g., the exit 404) of the elliptical scatter shield 400.

[0037] FIG. 5 illustrates regions of scattered light in an elliptical scatter shield, in accordance with some examples. The elliptical scatter shield 400 is shown with three regions of scatter. By using a larger quantity of initial ray trajectories (e.g., range of angles at the entrance 402) than shown in FIG. 4, a more general overview of how frequently different regions of the elliptical scatter shield 400 may receive scattered light can be built. As shown in FIG.5, by simulating light scattered into the elliptical scatter shield, a high scatter region 502 may be identified that spans the entrance 402 and a curved section of the interior of the elliptical scatter shield, following the curvatureof the elliptical arc-shaped boundary 406. The high scatter region 502 may also encompasses the light trap 408.

[0038] A low scatter region 506 may be identified in the exit 404 that has a low amount of scattered light based on the frequency of ray trajectories that reflect into the low scatter region 506. In an example, the exit channel is aligned with the low scatter region 506. A medium scatter region 504 may be identified as regions of the interior of the elliptical scatter shield 400 that receive some amount of scattered light but not as frequently as the high scatter region 502.

[0039] FIG. 6 illustrates a PIC integrating an elliptical scatter shield with additional photonic componentry, in accordance with some examples. A waveguide 602 may be positioned in the input channel of the entrance 402, The waveguide 602 may be configured to exit the input channel parallel to the input channel and curve through the high scatter region. The waveguide 602 may be configured to exit the elliptical scatter shield 400 through the exit 404 where the waveguide 602 may be parallel to the exit channel. In an example, any other suitable photonic elements, such as detector 604, may be positioned in the elliptical scatter shield 400. In an example, the detector 604 may be positioned near the exit 404 such that the waveguide 602 is optically coupled to a hair-pin turn of a superconducting single photon detector 604.

[0040] FIG. 7 illustrates a multiple ellipse scatter shield 700, in accordance with some examples. The multi ellipse scatter shield 700 may include first ellipse scatter shield 702, connector region 704, second ellipse scatter shield 706, connector region 708, and detection area scatter shield 710.

[0041] The first ellipse scatter shield 702 and second ellipse scatter shield 706 may be the elliptical scatter shield 400 as described above in FIGS. 4-6. In an example, the connector region 704 may be positioned at the exit channel of first ellipse scatter shield 702, and second ellipse scatter shield 706 may be oriented such that the entrance channel of second ellipse scatter shield 706 is aligned to the connector region 704. That is, multi ellipse scatter shield 700 may be a series of cascaded elliptical scatter shield 400, where the input channel of a downstream elliptical scatter shield 400 is connected to the output channel of the upstream elliptical scatter shield 400.

[0042] The connector region 708 may be used to connect second ellipse scatter shield 706 to detection area scatter shield 710. The detection area scatter shield 710 may be configured to have additional openings, e.g., for photonic or electrical connections to other areas of the PIC.

[0043] FIG. 8 illustrates a portion of a PIC integrating the multiple ellipse scatter shield 700 with additional photonic components, in accordance with some examples. That is, in an example, the ellipse scatter shield 700 can extend (e.g., using deep and shallow metal-filled trenches and back-end-of-line metals) through several vertical regions of the PIC. In FIG. 8, a layer of the PIC including waveguide 802 and detection region 804 are shown. The waveguide 802 may be routed through the cascaded elliptical scatter shields and to a central area of the detection area scatter shield 710, where the detection region 804 of the waveguide may be optically coupled (e.g., through vertical coupling, out-of-the-page) to a detector. As mentioned above, in an example, the scatter mitigation shell may be further covered by a metallic ceiling. For example, in the Z-direction (out of the page with respect to FIG. 8), a layer of metal may be deposited on to the scatter shield 710, thereby enclosing the scatter shield 710 and allowing light to enter the scatter shield 710 through specific openings (e.g., entrance 402).

[0044] In some examples, the photonic element comprises other types of photonic elements. For example, in some examples, the scatter mitigation shell can enclose a photonic switch (e.g., Mach Zehnder Interferometer) to ensure the switch operates in low light conditions (e.g., to prevent scattered light from distorting a desired interference pattern from the switch. In an example, the photonic element comprises passive elements, such as a waveguide or cavity that is designed to operate in very low light conditions.

[0045] Example 1 is a photonic integrated circuit (PIC) comprising: a first area comprising a photonic element; a second area comprising a waveguide optically connected to the photonic element; and a scatter mitigation shell comprising a metallic enclosure to shield the first area from scattered light, the metallic enclosure comprising at least one elliptical arc-shaped boundary to prevent light scattered into the scatter mitigation shell from reaching aIlgiven region within the first area, the photonic element being positioned in the given region.

[0046] In Example 2, the subject matter of Example 1 includes, wherein light scattered into the scatter mitigation shell comprises light scattered from a light source coupled to the waveguide.

[0047] In Example 3, the subject matter of Example 2 includes, wherein the light source comprises a laser.

[0048] In Example 4, the subject matter of Example 3 includes, wherein the light source is configured to enter the waveguide at an edge coupler.

[0049] In Example 5, the subject matter of Examples 1-4 includes, wherein light scattered into the scatter mitigation shell comprises light scattered from sources other than a light source coupled to the waveguide.

[0050] In Example 6, the subject matter of Examples 1-5 includes, wherein the metallic enclosure comprises at least one opening.

[0051] In Example 7, the subject matter of Example 6 includes, wherein the scatter mitigation shell comprises an input channel, the waveguide positioned parallel to and within the input channel, wherein the waveguide is further positioned towards the elliptical arc-shaped boundary at an output of the input channel.

[0052] In Example 8, the subject matter of Example 7 includes, wherein the scatter mitigation shell comprises an output channel that is parallel to the input channel.

[0053] In Example 9, the subject matter of Example 8 includes, wherein the input channel and the output channel are oriented opposite the elliptical arc¬ shaped boundary.

[0054] In Example 10, the subject matter of Example 9 includes, wherein the output channel is positioned at the given region, and wherein the waveguide is positioned within the output channel.

[0055] In Example 11, the subject matter of Example 10 includes, wherein the output channel connects to a second input channel, the waveguide positioned parallel to and within the second input channel, wherein thewaveguide is further positioned towards a second elliptical arc-shaped boundary at an output of the second input channel.

[0056] In Example 12, the subject matter of Examples 1–11 includes, wherein at least one elliptical arc-shaped boundary is configured to control a trajectory of light scattered into the scatter mitigation shell.

[0057] In Example 13, the subject matter of Example 12 includes, wherein at least one elliptical arc-shaped boundary is configured to confine light scattered into the scatter mitigation shell within a top half of at least one elliptical arc-shaped boundary.

[0058] In Example 14, the subject matter of Examples 1-13 includes, wherein the photonic element comprises a photon detector.

[0059] In Example 15, the subject matter of Example 14 includes, wherein the scatter mitigation shell reduces background light at the photon detector and wherein a signal to noise ratio of the photon detector is increased relative to positioning the photon detector at other regions in the scatter mitigation shell.

[0060] In Example 16, the subject matter of Examples 1–15 includes, wherein the scatter mitigation shell further comprises a metallic ceiling covering the at least one elliptical arc-shaped boundary and the first area.

[0061] In Example 17, the subject matter of Example 16 includes, a first elliptical arc-shaped boundary connected to a second elliptical arc-shaped boundary through an output channel in the first elliptical arc-shaped boundary positioned at the given region.

[0062] In Example 18, the subject matter of Example 17 includes, an output channel in the second elliptical arc-shaped boundary positioned at a second given region.

[0063] Example 19 is a method for shielding a photonic element from scattered light, the method comprising: configuring a photonic integrated circuit (PIC) with a first area comprising a photonic element and a second area comprising a waveguide optically connected to the photonic element; configuring the PIC with a scatter mitigation shell comprising a metallic enclosure to shield the first area from scattered light, the metallic enclosure comprising: at least one opening; at least one elliptical arc-shaped boundary;an input channel, the waveguide positioned parallel to and within the input channel, wherein the waveguide is further positioned towards the elliptical arc-shaped boundary at an output of the input channel; and an output channel positioned at a given region in the first area, wherein the waveguide is positioned within the output channel; coupling at least one light source into the PIC, resulting in scattered light; and controlling a trajectory of scattered light using the at least one elliptical arc-shaped boundary to prevent light scattered into the scatter mitigation shell from reaching the given region within the first area.

[0064] Example 20 is at least one machine-readable medium including instructions that, when executed by processing circuitry, cause the processing circuitry to perform operations to implement of any of Examples 1-19.

[0065] Example 21 is an apparatus comprising means to implement of any of Examples 1-19.

[0066] Example 22 is a system to implement of any of Examples 1-19.

[0067] Example 23 is a method to implement of any of Examples 1-19.

[0068] The foregoing disclosure provides illustration and description but is not intended to be exhaustive or to limit the implementations to the precise form disclosed. Modifications may be made in light of the above disclosure or may be acquired from practice of the implementations. As used herein, the term “component” is intended to be broadly construed as hardware, firmware, or a combination of hardware and software. It will be apparent that systems and / or methods described herein may be implemented in different forms of hardware, firmware, and / or a combination of hardware and software. The actual specialized control hardware or software code used to implement these systems and / or methods is not limiting of the implementations. Thus, the operation and behavior of the systems and / or methods are described herein without reference to specific software code - it being understood that software and hardware can be used to implement the systems and / or methods based on the description herein. As used herein, satisfying a threshold may, depending on the context, refer to a value being greater than the threshold, greater than or equal to the threshold, less thanthe threshold, less than or equal to the threshold, equal to the threshold, and / or the like, depending on the context. Although particular combinations of features are recited in the claims and / or disclosed in the specification, these combinations are not intended to limit the disclosure of various implementations. In fact, many of these features may be combined in ways not specifically recited in the claims and / or disclosed in the specification.

[0069] Although each dependent claim listed below may directly depend on only one claim, the disclosure of various implementations includes each dependent claim in combination with every other claim in the claim set. No element, act, or instruction used herein should be construed as critical or essential unless explicitly described as such. Also, as used herein, the articles “a” and “an” are intended to include one or more items and may be used interchangeably with “one or more.” Further, as used herein, the article “the” is intended to include one or more items referenced in connection with the article “the” and may be used interchangeably with “the one or more.” Furthermore, as used herein, the term “set” is intended to include one or more items (e.g., related items, unrelated items, a combination of related and unrelated items, and / or the like), and may be used interchangeably with “one or more.” Where only one item is intended, the phrase “only one” or similar language is used. Also, as used herein, the terms “has,” “have,” “having,” or the like are intended to be open-ended terms. Further, the phrase “based on” is intended to mean “based, at least in part, on” unless explicitly stated otherwise. Also, as used herein, the term “or” is intended to be inclusive when used in a series and may be used interchangeably with “and / or,” unless explicitly stated otherwise (e.g., if used in combination with “either” or “only one of’).

Claims

CLAIMSWhat is claimed is:

1. A photonic integrated circuit (PIC) comprising:a first area comprising a photonic element;a second area comprising a waveguide optically connected to the photonic element; anda scatter mitigation shell comprising a metallic enclosure to shield the first area from scattered light, the metallic enclosure comprising at least one elliptical arc-shaped boundary to prevent light scattered into the scatter mitigation shell from reaching a given region within the first area, the photonic element being positioned in the given region,2. The PIC of claim 1, wherein light scattered into the scatter mitigation shell comprises light scattered from a light source coupled to the waveguide.

3. The PIC of claim 2, wherein the light source comprises a laser.

4. The PIC of claim 3, wherein the light source is configured to enter the waveguide at an edge coupler.

5. The PIC of claim 1, wherein light scattered into the scatter mitigation shell comprises light scattered from sources other than a light source coupled to the waveguide.

6. The PIC of claim 1, wherein the metallic enclosure comprises at least one opening.

7. The PIC of claim 6, wherein the scatter mitigation shell comprises an input channel, the waveguide positioned parallel to and within the input channel, wherein the waveguide is further positioned towards the elliptical arc-shaped boundary at an output of the input channel.

8. The PIC of claim 7, wherein the scatter mitigation shell comprises an output channel that is parallel to the input channel.

9. The PIC of claim 8, wherein the input channel and the output channel are oriented opposite the elliptical arc-shaped boundary.

10. The PIC of claim 9, wherein the output channel is positioned at the given region, and wherein the waveguide is positioned within the output channel.

11. The PIC of claim 10, wherein the output channel connects to a second input channel, the waveguide positioned parallel to and within the second input channel, wherein the waveguide is further positioned towards a second elliptical arc-shaped boundary at an output of the second input channel.

12. The PIC of claim 1, wherein at least one elliptical arc-shaped boundary is configured to control a trajectory of light scattered into the scatter mitigation shell.

13. The PIC of claim 12, wherein at least one elliptical arc-shaped boundary is configured to confine light scattered into the scatter mitigation shell within a top half of at least one elliptical arc-shaped boundary.

14. The PIC of claim 1, wherein the photonic element comprises an optical detector.

15. The PIC of claim 1, wherein the photonic element comprises an optical switch.

16. The PIC of claim 14, wherein the scatter mitigation shell reduces background light at the optical detector and wherein a signal to noise ratio of the optical detector is increased relative to positioning the optical detector at other regions in the scatter mitigation shell.

17. The PIC of claim 1, wherein the scatter mitigation shell further comprises a metallic ceiling covering the at least one elliptical arc-shaped boundary and the first area.

18. The PIC of claim 17, further comprising a first elliptical arc-shaped boundary connected to a second elliptical arc-shaped boundary through an output channel in the first elliptical arc-shaped boundary positioned at the given region.

19. The PIC of claim 18, further comprising an output channel in the second elliptical arc-shaped boundary positioned at a second given region.

20. A method for shielding a photonic element from scattered light, the method comprising:configuring a photonic integrated circuit (PIC) with a first area comprising a photonic element and a second area comprising a waveguide optically connected to the photonic element;configuring the PIC with a scatter mitigation shell comprising a metallic enclosure to shield the first area from scattered light, the metallic enclosure comprising:at least one opening;at least one elliptical arc-shaped boundary;an input channel, the waveguide positioned parallel to and within the input channel, wherein the waveguide is further positioned towards the elliptical arc-shaped boundary at an output of the input channel; andan output channel positioned at a given region in the first area, wherein the waveguide is positioned within the output channel;coupling at least one light source into the PIC, resulting in scattered light; andcontrolling a trajectory of scattered light using the at least one elliptical arc-shaped boundary to prevent light scattered into the scatter mitigation shell from reaching the given region within the first area.

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