Patent Publication Number: US-2022214509-A1

Title: Beam Steering Structure with Integrated Polarization Splitter

Description:
CLAIM OF PRIORITY 
     This application is a continuation application under 35 U.S.C. 120 of prior U.S. Non-Provisional application Ser. No. 16/440,903, filed on Jun. 13, 2019, which claims priority under 35 U.S.C. 119(e) to U.S. Provisional Patent Application No. 62/684,904, filed Jun. 14, 2018. The disclosure of each above-identified application is incorporated herein by reference in its entirety for all purposes. 
    
    
     BACKGROUND 
     1. Field of the Invention 
     The present invention relates to optical data communication. 
     2. Description of the Related Art 
     Optical data communication systems operate by modulating laser light to encode digital data patterns. The modulated laser light is transmitted through an optical data network from a sending node to a receiving node. The modulated laser light having arrived at the receiving node is de-modulated to obtain the original digital data patterns. Therefore, implementation and operation of optical data communication systems is dependent upon having reliable and efficient mechanisms for transmitting laser light and detecting laser light at different nodes within the optical data network. In this regard, it can be necessary to transmit laser light from an optical fiber to a chip, and vice-versa. It is within this context that the present invention arises. 
     SUMMARY 
     In an example embodiment, a beam-turning assembly is disclosed. The beam-turning assembly includes a beam steering structure that includes an alignment structure shaped to receive and align an optical fiber such that an axis of a core of the optical fiber is oriented in a first direction within the alignment structure. The beam steering structure includes an end portion having an angled optical surface oriented at a non-zero angle relative to the first direction. The end portion is shaped and positioned so that light propagating along the first direction from the optical fiber in the alignment structure passes through the end portion to reach the angled optical surface. The beam-turning assembly includes a reflecting system positioned on the angled optical surface across the first direction so that light propagating along the first direction through the end portion is incident upon the reflecting system at the angled optical surface. The reflecting system is configured to reflect incident light propagating along the first direction into a first reflected beam of a first polarization and a second reflected beam of a second polarization. The first reflected beam and the second reflected beam are separated by a beam spacing sized to direct the first reflected beam into a first optical communication channel and to direct the second reflected beam into a second optical communication channel. 
     In another example embodiment, a beam-turning assembly is disclosed. The beam-turning assembly includes a beam steering structure that includes an alignment structure shaped to receive and align an optical fiber such that an axis of a core of the optical fiber is oriented in a first direction within the alignment structure. The beam steering structure includes an end portion having an angled optical surface oriented at an angle relative to the first direction. The beam-turning assembly includes a reflecting system positioned on the angled optical surface across the first direction so that light propagating along the first direction from the optical fiber is incident upon the reflecting system. The reflecting system is configured to reflect incident light propagating along the first direction into a first reflected beam of a first polarization and a second reflected beam of a second polarization. The first reflected beam and the second reflected beam are separated by a beam spacing sized to direct the first reflected beam into a first optical communication channel and to direct the second reflected beam into a second optical communication channel. The end portion of the beam steering structure is shaped and positioned so that the first reflected beam and the second reflected beam do not pass through the beam steering structure. 
     In another example embodiment, a method is disclosed for optical beam turning in an optical data communication system. The method includes an operation for positioning an optical fiber in an alignment structure of a beam steering structure such that an axis of a core of the optical fiber is oriented in a first direction within the alignment structure. The first direction is oriented toward a reflecting system positioned on an angled optical surface of an end portion of the beam steering structure. The angled optical surface is oriented at a non-zero angle relative to the first direction. The reflecting system is configured to reflect incident light propagating along the first direction into a first reflected beam of a first polarization and a second reflected beam of a second polarization. The first reflected beam and the second reflected beam are separated by a beam spacing sized to direct the first reflected beam into a first optical communication channel and to direct the second reflected beam into a second optical communication channel. The method also includes an operation for transmitting light through the optical fiber so that the light travels from the optical fiber in the first direction and is incident upon the reflecting system. The light incident upon the reflecting system is split into the first reflected beam and the second reflected beam. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a vertical cross-section view of a beam-turning assembly  100  that includes a beam steering structure, in accordance with some embodiments. 
         FIG. 2  shows a top schematic view of an integrated optical interface device that includes the beam steering structure (or another type of beam steering structure described herein) and a fan-out device integrated with the beam steering structure, in accordance with some embodiments. 
         FIG. 3A  shows a vertical cross-section view of a beam steering structure, in accordance with some embodiments. 
         FIG. 3B  shows an isometric view of the beam steering structure of  FIG. 3A , in accordance with some embodiments. 
         FIG. 4A  shows a vertical cross-section view of a beam steering structure, in accordance with some embodiments. 
         FIG. 4B  shows an isometric view of the beam steering structure of  FIG. 4A , in accordance with some embodiments. 
         FIG. 5  shows a vertical cross-section view of a beam steering structure, in accordance with some embodiments. 
         FIG. 6  shows a vertical cross-section through the beam steering section of the beam steering structure of  FIG. 4A , in accordance with some embodiments. 
         FIG. 7  shows a vertical cross-section through the reflecting system, in accordance with some embodiments. 
         FIG. 8  shows a vertical cross-section through a beam steering section that is a variation of the beam steering section as shown in  FIG. 6 , in accordance with some embodiments. 
         FIG. 9  shows a vertical cross-section view of a beam steering structure, in accordance with some embodiments. 
         FIG. 10  shows a vertical cross-section view of a beam steering structure having a base, in accordance with some embodiments. 
         FIG. 11A  shows an isometric view of a beam steering structure, in accordance with some embodiments. 
         FIG. 11B  shows a top view of the beam steering structure of  FIG. 11A , in accordance with some embodiments. 
         FIG. 11C  shows a side view of the beam steering structure, corresponding to view A-A as referenced in  FIG. 11B , in accordance with some embodiments. 
         FIG. 11D  shows an end view of the beam steering structure, corresponding to view B-B as referenced in  FIG. 11B , in accordance with some embodiments. 
         FIG. 11E  shows a close-up side view of the beam steering structure of  FIG. 11A , with one of the optical fibers positioned in one of the v-grooves of the v-groove array, in accordance with some embodiments. 
         FIG. 11F  shows an end view of the beam steering structure, with one of the optical fibers positioned in one of the v-grooves of the v-groove array, corresponding to view C-C as referenced in  FIG. 11E , in accordance with some embodiments. 
         FIG. 11G  shows a close-up view of the area as referenced in  FIG. 11C , in accordance with some embodiments. 
         FIG. 12  shows a schematic of a vertical cross-section of a beam steering structure positioned substantially parallel to a use device, in accordance with some embodiments. 
         FIG. 13  shows a configuration of the reflecting system, in accordance with some embodiments. 
         FIG. 14  shows a plot of beam spacing as a function of the incidence angle between in input optical beam and the direction normal to angled optical surface for the beam steering structure having the reflecting system parameters of  FIG. 12 , in accordance with some embodiments. 
         FIG. 15  shows a plot of light loss (dB) as a function of angle deviation for the beam steering structure, where the angle deviation is defined as the difference between the incidence angle and the nominal designed angle, in accordance with some embodiments. 
         FIG. 16  shows another configuration of the reflecting system, in accordance with some embodiments. 
         FIG. 17  shows a plot of beam spacing as a function of the incidence angle for the beam steering structure having the reflecting system parameters of  FIG. 16 , in accordance with some embodiments. 
         FIG. 18  shows another configuration of the reflecting system of  FIG. 12 , in accordance with some embodiments. 
         FIG. 19  shows another configuration of the reflecting system of  FIG. 12 , in accordance with some embodiments. 
         FIG. 20  shows a variation of the reflecting system configuration of  FIG. 19 , in which the first reflecting region is reduced in thickness, in accordance with some embodiments. 
         FIG. 21  shows a flowchart of a method for optical beam turning in an optical data communication system, in accordance with some embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, numerous specific details are set forth in order to provide an understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without some or all of these specific details. In other instances, well known process operations have not been described in detail in order not to unnecessarily obscure the present invention. 
     In fiber-optic data communication systems, polarizing beam (i.e., light beam) splitters pass light of one polarization in a first direction, while re-directing light of a second polarization in a different direction. Such a function may be accomplished using Bragg-reflector stacks sandwiched between two prisms, and having index values meeting the Brewster condition, such that the Bragg reflection is highly polarization sensitive. These types of beam splitters are suitable for free-space applications using bulk optical components, and can be incorporated into discrete fiber-coupled components. 
     Also, in fiber-optic data communication systems, light is coupled from an optical fiber to a photonic chip, and vice-versa, and various approaches are being explored for fiber-to-chip coupling, one goal of which is to achieve scalable manufacturing of packaged devices incorporating integrated optics. Various embodiments for coupling light from an optical fiber to a photonic chip implement edge-coupling techniques and/or vertical-coupling techniques. In some edge-coupling techniques, light is coupled at the edge of a chip to fibers parallel and flush with on-chip waveguides. In some vertical-coupling techniques, a beam-turning element is implemented to allow horizontal packaging of fibers, which can improve the mechanically robustness of a packaged device, i.e., of a photonic chip within optical fiber(s) attached thereto. Also, in some packaged device configurations, a beam-turning connector for fiber-to-chip coupling can utilize one or more bent fiber(s), where multiple fibers can be ribbonized for scalability. 
     One challenge in fiber-to-chip coupling is that fibers typically carry light of two polarizations, while on-chip devices and waveguides are commonly single-polarization, so that a polarization multiplexing function is required. In some embodiments, this polarization multiplexing function can be achieved using an on-chip dual-polarization grating coupler, a type of vertical coupler that couples light from each of two on-chip waveguides to a different fiber polarization. However, because dual-polarization grating couplers can have substantially higher loss than single-polarization grating couplers, it can be beneficial to separate implementation of the polarization multiplexing function from the grating coupler. 
     With the above-mentioned issues in mind, it should be noted that polarizing beam-splitters employing multilayer dielectric stacks are not generally suitable for use in fiber-to-chip coupling, as they do not provide high-density connectivity or scalable manufacturing as needed for coupling of fibers to integrated devices. However, a beam-turning assembly is disclosed herein for high-density connectivity that includes a polarizing beam-splitter that is suitable for use in a fiber-to-chip coupler. 
     It is noted that in many applications, on-chip devices and waveguides may operate with both polarizations, allowing, for example, two separate communication channels. In such cases, the invention disclosed herein could be used to transmit signals with two separate polarizations, via two separate grating couplers, to the same output fiber, thus enhancing system capacity with comparable packaging costs. 
       FIG. 1  shows a vertical cross-section view of a beam-turning assembly  100  that includes a beam steering structure  101 , in accordance with some embodiments. The beam steering structure  101  includes an end portion  102  having an angled optical surface  103  angled at a surface angle  105  measured relative to a direction of propagation of an input optical beam  107 , i.e., relative to an axis of a core of an optical fiber  109 , when the optical fiber  109  is positioned in an alignment structure  111  of the beam steering structure  101 . In other words, with the direction of propagation of the input optical beam  107  considered as a first direction, the angled optical surface  103  is oriented at the surface angle  105  which is a non-zero angle relative to the first direction. In some embodiments, the alignment structure  111  is shaped to receive and align the optical fiber  109  such that the above-mentioned first direction is substantially parallel to a surface of optical incidence of a use device  116 , e.g., of a photonic chip. In some embodiments, the alignment structure  111  is shaped to receive and align the optical fiber  109  such that the above-mentioned first direction is not parallel to a surface of optical incidence of the use device  116 . The alignment structure  111  is shaped to receive and align the optical fiber  109  such that the axis of the core of the optical fiber  109  is oriented in the above-mentioned first direction, as indicated by the arrow representing the input optical beam  107 . In some embodiments, the alignment structure  111  is a v-groove into which the optical fiber  109  is positioned. The end portion  102  is shaped and positioned so that light propagating along the above-mentioned first direction from the optical fiber  109  in the alignment structure  111  passes through the end portion  102  to reach the angled optical surface  103 . 
     A reflecting system  113  is disposed on the angled optical surface  103  to extend over at least an area of the optical surface  103  upon which the input optical beam  107  is incident. The reflecting system  113  is positioned on the angled optical surface  103  across the above-mentioned first direction, as indicated by the arrow representing the input optical beam  107 , so that light propagating along the first direction through the end portion  102  is incident upon the reflecting system  113  at the angled optical surface  103 . The reflecting system  113  functions to reflect the input optical beam  107  that is emitted from the core of the optical fiber  109  into a reflected beam  115  directed toward a use device  116 , such as a photonic chip. In some embodiments, the reflecting system  113  can be formed as a multilayer stack of materials, such as a multilayer stack of films and/or coatings. The reflected beam  115  includes a first reflected beam  115 A of a first polarization and a second reflected beam  115 B of a second polarization. Therefore, the reflecting system  113  is configured to reflect incident light propagating along the above-mentioned first direction (as indicated by the arrow representing the input optical beam  107 ) into the first reflected beam  115 A of the first polarization and the second reflected beam  115 B of the second polarization. The first reflected beam  115 A is separated from the second reflected beam  115 B by a beam spacing  117 . The beam spacing  117  is large enough to provide separation of the first reflected beam  115 A and the second reflected beam  115 B into respective optical communication channels of the use device  116 . In other words, the first reflected beam  115 A and the second reflected beam  115 B are separated by the beam spacing  117  sized to direct the first reflected beam  115 A into a first optical communication channel and to direct the second reflected beam  115 B into a second optical communication channel. In some embodiments, the use device  116  is a photonic chip that includes optical input couplers separated by the beam spacing  117 . It should also be understood that in some embodiments, the direction of travel of the reflected beam  115  and the input optical beam  107  can be reversed, such that the reversed version of the reflected beam  115  is reflected by the reflecting system  113  on the angled optical surface  103  into the core of the optical fiber  109 . For example, in some embodiments, one or both of the first reflected beam  115 A and the second reflected beam  115 B is/are transmitted from the use device  116  through the end portion  102  of the beam steering structure  101  toward the reflecting system  113 , and is/are reflected by the reflecting system  113  into the core of the optical fiber  109 . 
     The alignment structure  111  can be formed integrally with the beam steering structure  101 . The alignment structure  111  facilitates placement of a waveguide, such as the optical fiber  109 , that defines the input optical beam  107 . The beam steering structure  101  can be configured to receive multiple input optical beams  107 . For example, in some embodiments, the beam steering structure  101  can be configured to receive an array of optical fibers  109 . In some embodiments, the beam steering structure  101  can include a v-groove array that has multiple v-grooves oriented to extend parallel to each other, with each v-groove configured to receive one optical fiber  109 . Also, in some embodiments, the waveguide that defines the input optical beam  107 , e.g., the optical fiber  109 , can optionally include an optical lensing element  106 , such as a gradient index (GRIN) lens or graded-index optical fiber. And, in some embodiments, the optical lensing element  106  of the waveguide that defines the input optical beam  107  can cause the input optical beam  107  to converge as it enters the beam steering structure  101  and approaches the optical surface  103 . In various embodiments, the optical lensing element  106  can be connected to the optical fiber  109  and/or the beam steering structure  101 . The beam steering structure  101  includes a recessed region  114 , with the end portion  102  positioned at an end of the recessed region  114 , and with the alignment structure  111  positioned in the recessed region  114 . The recessed region  114  has a recess height h 1 . The recess height hl helps determine the vertical position of the beam waist with respect to the use device  116  and the clearance of the optical fiber  109  relative to the use device  116  or other elements of an optical package. 
     In some embodiments, the beam steering structure  101  can be integrated with other devices, such as with other optical waveguide devices/structures and/or other optical components, within an integrated optical interface device.  FIG. 2  shows a top schematic view of an integrated optical interface device  202  that includes the beam steering structure  101  (or another type of beam steering structure described herein) and a fan-out device  207  integrated with the beam steering structure  101 , in accordance with some embodiments. The integrated optical interface device  202  is fabricated on a portion  209 A of a substrate  209 . The integrated optical interface device  202  can be one of many devices fabricated on the substrate  209 . In some embodiments, at least some of the fabrication steps used to produce the many devices on the substrate  209  can be performed in parallel to provide scalable manufacturing. Also, in some embodiments, different configurations of integrated optical interface devices and/or beam steering structures can be fabricated on the same substrate  209 . For example,  FIG. 2  also shows another portion  209 B of the substrate  209  where the beam steering structure  101  is fabricated as a stand-alone component. Therefore, it should be understood that in some embodiments a plurality of integrated optical interface devices and/or beam steering structures are fabricated in parallel (at the same time) on respective portions of a single substrate. In this manner, wafer fabrication processes are applied to simultaneously manufacture multiple instances of integrated optical interface devices and/or beam steering structures on a single substrate and thereby provide for scalable manufacturing. 
     As shown in  FIG. 2 , in some embodiments, the beam steering structure  101  (or other beam steering structure disclosed herein) can be integrated with the fan-out device  207 . The fan-out device  207  includes optical waveguides  203  integrated/formed on the substrate  209 . The optical waveguides  203  fan-out from one side of the fan-out device  207  near the reflecting system  113 , where there is a smaller spacing between adjacent optical waveguides  203 , to another side of the fan-out device  207  where there is a larger spacing between adjacent optical waveguides  203 . The larger spacing between adjacent optical waveguides  203  can ease installation of optical fibers, such that the optical fibers direct respective beams of light into the optical waveguides  203  and/or receive respective beams of light from the optical waveguides  203 . At the side of the fan-out device  207  where there is a smaller spacing between adjacent optical waveguides  203 , the optical waveguides  203  can be fabricated to direct light onto the reflecting system  113 . In some embodiments, the substrate  209  can be formed of silica or silicon, using standard fabrication processes. In some embodiments, the optical waveguides  203  can include a nitride or other optical material. In various embodiments, the optical waveguides  203  can be part of a planar lightwave circuit or part of an interposer device. In some embodiments, the angled surface on which the reflecting system  113  is formed can be made by grey-scale etching methods, among other methods. Also, in some embodiments, the optical waveguides  203  and/or the angled surface on which the reflecting system  113  is formed can be fabricated using optical lithography methods, such as those used in semiconductor fabrication processes. In some embodiments, the reflecting system  113  can include a polarization beam splitting coating, such as described with regard to  FIG. 1 . The fan-out device  207  can also be configured to include optical fiber alignment features. For example, the fan-out device  207  can be configured to include an array of v-grooves at the side of the fan-out device  207  where there is a larger spacing between adjacent optical waveguides  203 . Each of the v-grooves in the array can be configured to receive an optical fiber and align the core of the optical fiber with a respective one of the optical waveguides  203 . 
       FIG. 3A  shows a vertical cross-section view of a beam steering structure  301 , in accordance with some embodiments.  FIG. 3B  shows an isometric view of the beam steering structure  301 , in accordance with some embodiments. The beam steering structure  301  includes a substrate  303  that can be formed of silica or silicon, among other materials, in various embodiments. The substrate  303  includes a beam steering section  305  that includes an angled surface  307 . A reflecting system  309  is disposed on the angled surface  307  of the beam steering section  305 . In some embodiments, the reflecting system  309  can be formed as a multilayer stack of materials, such as a multilayer stack of films and/or coatings. The substrate  303  includes an alignment structure  311  configured to receive and align a number of optical waveguides, such as optical fibers  313 . The alignment structure  311  is configured to orient the optical fibers  313  (or other type of optical waveguide) so that an input optical beam  315  transmitted from the optical fiber  313  is directed toward the reflecting system  309  on the angled surface  307 . The beam steering structure  301  includes the alignment structure  311  shaped to receive and align one or more optical fiber(s) such that an axis of a core of each of the optical fiber(s) is oriented in a first direction within the alignment structure  311 , such that the input optical beam  315  propagates in the first direction. The beam steering section  305  is formed as an end portion of the beam steering structure  301 . The beam steering section  305  has the angled optical surface  307  oriented at an angle relative to the above-mentioned first direction. 
     The reflecting system  309  is disposed on the angled surface  307  to extend over at least an area of the angled surface  307  upon which the input optical beam  315  is incident. The reflecting system  309  is positioned on the angled surface  307  across the above-mentioned first direction (the direction in which the input optical beam  315  propagates) so that light propagating along the first direction from the optical fiber  313  is incident upon the reflecting system  309 . The reflecting system  309  functions to reflect the input optical beam  315  that is emitted from the core of the optical fiber  313  into a reflected beam  317  directed outward away from the substrate  303  and toward a use device  319 , such as a photonic chip. The beam steering structure  301  is an outward-reflecting type of beam steering structure because it is configured to reflect the input optical beam  315  outward away from the substrate  303  without having the reflected beam  317  pass through the substrate  303 . In some embodiments, the reflected beam  317  includes a first reflected beam  317 A of a first polarization and a second reflected beam  317 B of a second polarization. The first reflected beam  317 A is separated from the second reflected beam  317 B by a beam spacing  321 . The beam spacing  321  is large enough to provide separation of the first reflected beam  317 A and the second reflected beam  317 B into respective optical channels of the use device  319 . 
     Therefore, in some embodiments, the reflecting system  309  is configured to reflect incident light of the input optical beam  315  propagating along the first direction (as indicated by the arrow representing the input optical beam  315 ) into the first reflected beam  317 A of the first polarization and the second reflected beam  317 B of the second polarization. The first reflected beam  317 A and the second reflected beam  317 B are separated by the beam spacing  321  that is sized to direct the first reflected beam  317 A into a first optical communication channel and to direct the second reflected beam  317 B into a second optical communication channel. The beam steering section  305  (end portion) of the beam steering structure  301  is shaped and positioned so that the first reflected beam  317 A and the second reflected beam  317 B do not pass through the beam steering structure  301 . 
     In some embodiments, the use device  319  is a photonic chip that includes optical input couplers separated by the beam spacing  319 . It should also be understood that in some embodiments, the direction of travel of the reflected beam  317  and the input optical beam  315  can be reversed, such that the reversed version of the reflected beam  317  is reflected by the reflecting system  309  on the angled surface  307  into the core of the optical fiber  313 . The thickness hi of substrate  303  can be consistent with robust manufacturability and the need to fit inside a surrounding package. The recess height h 2  helps determine the vertical position of the beam waist with respect to the use device  319  and the clearance of the optical fiber  313  relative to the use device  319  or other elements of an optical package. 
       FIG. 4A  shows a vertical cross-section view of a beam steering structure  401 , in accordance with some embodiments.  FIG. 4B  shows an isometric view of the beam steering structure  401 , in accordance with some embodiments. The beam steering structure  401  includes a substrate  403  that can be formed of silica or silicon, among other materials, in various embodiments. The substrate  403  includes a beam steering section  405  that includes an angled surface  407 . A reflecting system  409  is disposed on the angled surface  407  of the beam steering section  405 . In some embodiments, the reflecting system  409  can be formed as a multilayer stack of materials, such as a multilayer stack of films and/or coatings. The substrate  403  includes alignment structures  411  configured to receive and align a number of optical waveguides, such as optical fibers  413 . The alignment structures  411  are configured to orient the optical fibers  413  (or other type of optical waveguide) so that an input optical beam  415  transmitted from the optical fiber  413  is directed through the beam steering section  405  toward the reflecting system  409  on the angled surface  407 . 
     The reflecting system  409  is disposed on the angled surface  407  to extend over at least an area of the angled surface  407  upon which the input optical beam  415  is incident. The reflecting system  409  functions to reflect the input optical beam  415  that is emitted from the core of the optical fiber  413  into a reflected beam  417  directed inward through the substrate  403  and toward a use device  419 , such as a photonic chip. The beam steering structure  401  is an inward-reflecting type of beam steering structure because it is configured to reflect the input optical beam  415  inward through the substrate  403  and toward the use device  419 . In some embodiments, the reflected beam  417  includes a first reflected beam  417 A of a first polarization and a second reflected beam  417 B of a second polarization. The first reflected beam  417 A is separated from the second reflected beam  417 B by a beam spacing  421 . The beam spacing  421  is large enough to provide separation of the first reflected beam  417 A and the second reflected beam  417 B into respective optical channels of the use device  419 . In some embodiments, the use device  419  is a photonic chip that includes optical input couplers separated by the beam spacing  421 . It should also be understood that in some embodiments, the direction of travel of the reflected beam  417  and the input optical beam  415  can be reversed, such that the reversed version of the reflected beam  417  is reflected by the reflecting system  409  on the angled surface  407  into the core of the optical fiber  413 . The thickness h 1  of substrate  403  can be consistent with robust manufacturability and the need to fit inside a surrounding package. The recess height h 2  helps determine the vertical position of the beam waist with respect to the use device  419  and the clearance of the optical fiber  413  relative to the use device  419  or other elements of an optical package. 
     For both the outward-reflecting type of beam steering structure  301  and the inward-reflecting type of beam steering structure  401 , it may be advantageous to have the alignment structures  311 ,  411  open either toward or away from the use device  319 ,  419 . The decision to have the alignment structures  311 ,  411  open either toward or away from the use device  319 ,  419  can be based on packaging considerations such as clearance, thermal management, and/or other considerations. For example, the inward-reflecting type of beam steering structure  401  is configured to have the alignment structures  411  open away from the use device  419 . In contrast, the beam steering structure  101  of  FIG. 1  shows another inward-reflecting type of beam steering structure configured to have the alignments structures  111  open toward the use device  116 . 
     It should be understood that fabrication of the reflecting system  309  for the outward-reflecting type of beam steering structure  301  differs from fabrication of the reflecting system  409  for the inward-reflecting type of beam steering structure  401 . Specifically, for the outward-reflecting type of beam steering structure  301 , a first reflecting region of the reflecting system  309  that is initially encountered by the input optical beam  315  is deposited/formed after (and possibly on top of) a second reflecting region of the reflecting system  309 , where the first reflecting region of the reflecting system  309  is defined to reflect the first reflected beam  317 A, and the second reflecting region of the reflecting system  309  is defined to reflect the second reflected beam  317 B. 
     For the inward-reflecting type of beam steering structure  101 ,  401 , a first reflecting region of the reflecting system  113 ,  409  is deposited/formed first followed by deposition/formation of a second reflecting region of the reflecting system  113 ,  409 , where the first reflecting region of the reflecting system  113 ,  409  is defined to reflect the first reflected beam  115 A,  417 A, and the second reflecting region of the reflecting system  113 ,  409  is defined to reflect the second reflected beam  115 B,  417 B. The fabrication of the reflecting system  113 ,  309 ,  409  considers material choice, layer adhesion, and flatness, among other issues. These issues associated with fabrication of the reflecting system  113 ,  309 ,  409  can be a consideration in determining whether or not to implement the outward-reflecting type of beam steering structure  301  or the inward-reflecting type of beam steering structure  101 ,  401 . 
       FIG. 5  shows a vertical cross-section view of a beam steering structure  501 , in accordance with some embodiments. The beam steering structure  501  includes a substrate  503  that can be formed of silica or silicon, among other materials, in various embodiments. The substrate  503  includes a beam steering section  505  that includes an angled surface  507 . A reflecting system  509  is disposed on the angled surface  507  of the beam steering section  505 . In some embodiments, the reflecting system  509  can be formed as a multilayer stack of materials, such as a multilayer stack of films and/or coatings. The substrate  503  includes alignment structures  511  configured to receive and align a number of optical waveguides, such as optical fibers  513 . The alignment structures  511  are configured to orient the optical fibers  513  (or other type of optical waveguide) so that an input optical beam  515  transmitted from the optical fiber  513  is directed to an input end of an intermediate optical waveguide  516 . The intermediate optical waveguide  516  is configured to extend through the beam steering section  505  so that an output end of the intermediate optical waveguide  516  is positioned and oriented to direct the input optical beam  515  toward the reflecting system  509  on the angled surface  507 . In this manner, the intermediate optical waveguide  516  is configured to couple light emitted from an input optical waveguide, e.g., optical fiber  513 , to an input optical beam incident on the reflecting system  509  on the angled surface  507 . 
     The reflecting system  509  is disposed on the angled surface  507  to extend over at least an area of the angled surface  507  upon which the input optical beam  515  that is emitted from the intermediate optical waveguide  516  is incident. The reflecting system  509  functions to reflect the input optical beam  515  that is emitted from the intermediate optical waveguide  516  into a reflected beam  517  directed inward through the substrate  503  and toward a use device  519 , such as a photonic chip. The beam steering structure  501  is an inward-reflecting type of beam steering structure because it is configured to reflect the input optical beam  515  inward through the substrate  503  and toward the use device  519 . In some embodiments, the reflected beam  517  includes a first reflected beam  517 A of a first polarization and a second reflected beam  517 B of a second polarization. The first reflected beam  517 A is separated from the second reflected beam  517 B by a beam spacing  521 . The beam spacing  521  is large enough to provide separation of the first reflected beam  517 A and the second reflected beam  517 B into respective optical channels of the use device  519 . In some embodiments, the use device  519  is a photonic chip that includes optical input couplers separated by the beam spacing  521 . It should also be understood that in some embodiments, the direction of travel of the reflected beam  517  and the input optical beam  515  can be reversed, such that the reversed version of the reflected beam  517  is reflected by the reflecting system  509  on the angled surface  507  into the intermediate optical waveguide  516  and from the intermediate optical waveguide  516  into the core of the optical fiber  513 . 
       FIG. 6  shows a vertical cross-section through the beam steering section  405  of the beam steering structure  401 , in accordance with some embodiments. The beam steering section  405  is configured so that the input optical beam  415  is oriented substantially parallel to a surface of optical incidence  605  on the use device  419 . Also, in  FIG. 6 , the input optical beam  415  is oriented parallel to a base of the beam steering section  405 , i.e., to a bottom surface  403 A of the substrate  403  of the beam steering section  405 . 
       FIG. 7  shows a vertical cross-section through the reflecting system  113 ,  409 , in accordance with some embodiments. The reflecting system  113 ,  409  includes a first reflecting region  409 A, a spacer region  409 B, and a second reflecting region  409 C. In various embodiments, each of the first reflecting region  409 A, the spacer region  409 B, and the second reflecting region  409 C can include one or multiple layers of material. In some embodiments, the reflecting system  113 ,  409  is formed as a multilayer stack of materials that includes one or more layers of material in the first reflecting region  409 A, one or more layers of material in the spacer region  409 B, and one or more layers of material in the second reflecting region  409 C, where the spacer region  409 B is disposed between the first reflecting region  409 A and the second reflecting region  409 C. 
     Strong polarization dependence of the first reflecting region  409 A of the reflecting system  113 ,  409  relies on the Brewster condition relating the incident angle between the input optical beam  107 ,  415  and the first reflecting region  409 A and index values of the materials of the beam steering section  101 ,  405  and the first reflecting region  409 A. With regard to the example of  FIG. 1 , the angle between the input optical beam  107  and the surface of optical incidence on the use device  116 , and the angle between the angled surface  103  and the surface of optical incidence on the use device  116 , can be defined in accordance with requirements of the optical grating couplers on the use device  116  into which the first reflected beam  115 A and the second reflected beam  115 B are directed, and can be defined to ease mechanical fabrication, and/or with consideration of other issues. After setting the angle between the input optical beam  107  and the surface of optical incidence on the use device  116 , and the angle between the angled surface  103  and the surface of optical incidence on the use device  116 , the material index of the first reflecting region  409 A is selected as indicated by the Brewster condition. 
     Similarly, with regard to the example of  FIG. 4A , the angle between the input optical beam  415  and the surface of optical incidence on the use device  419 , and the angle between the angled surface  407  and the surface of optical incidence on the use device  419 , can be defined in accordance with requirements of the optical grating couplers on the use device  419  into which the first reflected beam  417 A and the second reflected beam  417 B are directed, and can be defined to ease mechanical fabrication, and/or with consideration of other issues. After setting the angle between the input optical beam  415  and the surface of optical incidence on the use device  419 , and the angle between the angled surface  407  and the surface of optical incidence on the use device  419 , the material index of the first reflecting region  409 A is selected as indicated by the Brewster condition. 
     In some embodiments, the first reflecting region  409 A, or a first reflecting region material therein, is formed of a specific material mixture to achieve a material optical index value that optimizes the polarization selectivity. For example, in some embodiments, the first reflecting region  409 A, or a first reflecting region material therein, can be formed of a silicon oxynitride SiO x N y  material, where the parameters (x, y) are selected to achieve a material optical index value required by the Brewster condition. In an example embodiment, the first reflecting region  409 A, or a first reflecting region material therein, can be formed of a material that has a material optical index value (n hi ) of about 1.86. In some embodiments, the first reflecting region  409 A, or a first reflecting region material therein, is formed of a more standard optical coating material, which may provide advantages of reduced cost, improved consistency, improved reliability, among other advantages. In these embodiments, it may not be possible to customize the optical index value of the optical coating material. Therefore, in these embodiments, with regard to the example of  FIG. 1 , the angle between the input optical beam  107  and the surface of optical incidence on the use device  116 , and the angle between the angled surface  103  and the surface of optical incidence on the use device  116  can be controlled to achieve the Brewster condition. Similarly, in these embodiments, with regard to the example of  FIG. 4A , the angle between the input optical beam  415  and the surface of optical incidence on the use device  419 , and the angle between the angled surface  407  and the surface of optical incidence on the use device  419 , can be controlled to achieve the Brewster condition. 
     Some example optical coating materials that have a low optical material index value (n&lt;1.6) include SiO 2 , MgF 2 , and CeF 3 , among others. Some example optical coating materials that have an intermediate optical material index value (1.6&lt;=n&lt;=1.8) include SiO, Al 2 O 3 , and Y 2 O 3 , among others. Some example optical coating materials that have a high optical material index value (n&gt;1.8) include HfO 2 , Ta 2 O 5 , Nb 2 O 5 , LaTiO 3 , TiO 2 , among others. Also, some semiconductor materials of higher material optical index value include InP, Si, GaAs, among others. Also, in some embodiments, polymers can be used as the optical coating materials, such as Poly(1,1,1,3,3,3-hexafluoroisopropyl acrylate) that has a material optical index value (n=1.375) to Poly(pentabromophenyl methacrylate) that has a material optical index value (n=1.71), among others. In some embodiments, the optical coating material is also selected based on resistance to high temperatures and resistance to scratching, among other considerations. 
     In  FIG. 6 , the input optical beam  415  is depicted as horizontal and parallel to both the bottom surface  403 A of the substrate  403  of the beam steering section  405  and the horizontal plane of the use device  419 , i.e., the surface of optical incidence  605  on the use device  419 . Therefore, in the configuration of  FIG. 6 , the angle of the angled surface  407  as measured relative to the bottom surface  403 A of the substrate  403  controls a chip incidence angle  607  of the reflected beam  417 . The chip incidence angle  607  of the reflected beam  417  is measured between the direction of the reflected beam  417  and a vector perpendicular to the surface of optical incidence  605  on the use device  419  and within a reference plane that is coincident with the direction of the input optical beam  415  and perpendicular to the surface of optical incidence  605  on the use device  419 . 
     In some embodiments, the beam steering structure  401  can be tilted with respect to the surface of optical incidence  605  on the use device  419 . For example, in some embodiments, an active alignment process can be performed when positioning the beam steering structure  401  relative to the use device  419  to actively determine when first reflected beam  417 A and the second reflected beam  417 B are properly directed toward respective optical grating couplers on the use device  419 . In the active alignment process, light is transmitted through the beam steering structure  401  as it is positioned relative to the use device  419 , and the light received by the optical grating couplers on the use device  419  is monitored to determine when the first reflected beam  417 A and the second reflected beam  417 B are properly directed toward respective optical grating couplers on the use device  419 . Once proper alignment between the beam steering structure  401  and the use device  419  is achieved, the beam steering structure  401  can be fixed in position relative to the use device  419  by depositing an epoxy or similar adhesive between the beam steering structure  401  and the use device  419 . 
       FIG. 8  shows a vertical cross-section through a beam steering section  405 A that is a variation of the beam steering section  405  as shown in  FIG. 6 , in accordance with some embodiments. The beam steering section  405 A includes a ramp structure  801  configured to control an inclination angle  803  of the input optical beam  415  relative to the base of the beam steering section  405 A, i.e., to the bottom surface  403 A of the substrate  403  of the beam steering section  405 A. In some embodiments, such as shown in  FIG. 8 , the ramp structure  801  can be configured to incline the input optical beam  415  upward away from the base of the beam steering section  405 A. And, in some embodiments, the ramp structure  801  can be configured to incline the input optical beam  415  downward toward the base of the beam steering section  405 A. In the embodiment of  FIG. 8 , when the bottom surface  403 A of the substrate  403  of the beam steering section  405 A is positioned parallel with the surface of optical incidence  605  on the use device  419 , the inclination angle  803  will control the angle between the input optical beam  415  and the surface of optical incidence  605  on the use device  419 . Therefore, in the embodiments of  FIG. 8 , the inclination angle  803  and the angle between the angled surface  407  and the surface of optical incidence  605  on the use device  419 , can be defined in accordance with requirements of the optical grating couplers on the use device  419  into which the first reflected beam  417 A and the second reflected beam  417 B are directed, and can be defined to ease mechanical fabrication, and/or with consideration of other issues. 
       FIG. 9  shows a vertical cross-section view of a beam steering structure  901 , in accordance with some embodiments. The beam steering structure  901  includes an angled optical surface  903  angled at a surface angle  905  measured relative to a bottom surface  906  of a base of the beam steering structure  901 . In some embodiments, the beam steering structure  901  can include an alignment structure  911 , such as a v-groove, into which an optical fiber  909  is positioned. A reflecting system  913  is disposed on the angled optical surface  903  to extend over at least an area of the angled optical surface  903  upon which an input optical beam  907  is incident. In some embodiments, the reflecting system  913  can be formed as a multilayer stack of materials, such as a multilayer stack of films and/or coatings. The reflecting system  913  functions to reflect the input optical beam  907  that is emitted from the core of the optical fiber  909  into a reflected beam  915  directed toward a use device  916 , such as a photonic chip. The reflected beam  915  can include a first reflected beam  915 A of a first polarization and a second reflected beam  915 B of a second polarization. The first reflected beam  915 A is separated from the second reflected beam  915 B by a beam spacing  917 . The beam spacing  917  is large enough to provide separation of the first reflected beam  915 A and the second reflected beam  915 B into respective optical channels of the use device  916 . In some embodiments, the use device  916  is a photonic chip that includes optical input couplers separated by the beam spacing  917 . It should also be understood that in some embodiments, the direction of travel of the reflected beam  915  and the input optical beam  907  can be reversed, such that the reversed version of the reflected beam  915  is reflected by the reflecting system  913  on the angled optical surface  903  into the core of the optical fiber  909 . 
     In some embodiments, the alignment structure  911  can be formed integrally with the beam steering structure  901 . The alignment structure  911  facilitates placement of a waveguide, such as the optical fiber  909 , that defines the input optical beam  907 . The beam steering structure  901  can be configured to receive multiple input optical beams  907 . For example, in some embodiments, the beam steering structure  901  can be configured to receive an array of optical fibers  909 . In some embodiments, the alignment structure  911  of the beam steering structure  901  can include a v-groove array that has multiple v-grooves oriented to extend parallel to each other, with each v-groove configured to receive one optical fiber  909 . Also, in some embodiments, the waveguide that defines the input optical beam  907 , e.g., the optical fiber  909 , can include an optical lensing element, such as a GRIN lens or graded-index optical fiber. And, in some embodiments, the optical lensing element of the waveguide that defines the input optical beam  907  can cause the input optical beam  907  to converge as it enters the beam steering structure  901  and approaches the optical surface  903 . 
     The beam steering structure  901  also includes a ramp structure  918  configured to oriented the waveguide that defines the input optical beam  907 , e.g., the optical fiber  909 , at an angle  919  relative to the bottom surface  906  of the base of the beam steering structure  901 . In some embodiments, the alignment structure  911  is formed integrally with ramp structure  918 . In some embodiments, the ramp structure  918  is formed integrally with the beam steering structure  901 . In some embodiments, the ramp structure  918  and the beam steering structure  901  are physically separate structures, with the ramp structure  918  configured for installation on the beam steering structure  901 . In some embodiments, the angle  919  defines an angle between a direction of travel of the input optical beam  907  and the bottom surface  906  of the base of the beam steering structure  901 . The beam steering structure  901  and the ramp structure  918  can be defined so that the input optical beam  907  is incident upon the beam steering structure  901  at a non-perpendicular angle of incidence so as to mitigate reflection of the input optical beam  907  back into the waveguide, e.g., back into the core of the optical fiber  909 . Also, in some embodiments, a fill material  921  is used to secure the beam steering structure  901 , the optical fiber  909 , and the use device  916  in a fixed spatial orientation with respect to each other. In various embodiments, the fill material  921  can have a material optical index value similar to the core of the optical fiber  909  and/or the beam steering structure  901 . In some embodiments, the fill material  921  is an optical-grade epoxy. In some embodiments, the fill material  921  is a glass material having a low melting temperature. 
     It may be of interest to avoid back-reflections of the input optical beam  907  that direct light back into the core of the optical fiber  909 . Such back-reflections can lead to signal impairments (such as spectral interference and fading) and can possibly damage the optical source operating to generate the input optical beam  907 . In some embodiments, the fill material  921  is an optical index-matched material that has an optical index value substantially equal to the optical index value of either the beam-steering structure  901  and/or the core of the optical fiber  909 . Optical reflections of the input optical beam  907  are minimized at surfaces of the core of the optical fiber  909  and the beam steering structure  901  when the core of the optical fiber  909 , the fill material  921 , and the beam steering structure  901  have substantially the same optical index value. In some embodiments, an example common optical index value for the core of the optical fiber  909 , the fill material  921 , and the beam steering structure  901  is 1.45. However, it should be understood that in other embodiments, the optical index value for the core of the optical fiber  909 , the fill material  921 , and the beam steering structure  901  can be either less than 1.45 or greater than 1.45. 
     In some embodiments, the angle of the incident light on each interface within the beam steering structure  901  can be large enough to reduce capture of back-reflected light by the core of the optical fiber  909 . The ramp structure  918  can be configured to ensure that the angle of the incident light on each interface within the beam steering structure  901  is large enough to reduce capture of back-reflected light by the core of the optical fiber  909 . In some embodiments, the beam steering structure  901  can include additional angled interfaces to assist with preventing capture of back-reflected light by the core of the optical fiber  909 . For example, in some embodiments, the facet of the beam steering structure  901 , where the input optical beam  907  is incident upon the beam steering structure  901 , can be formed at an angle to reduce/prevent capture of back-reflected light by the core of the optical fiber  909 . 
     In some embodiments, the beam steering structure  901  can be actively aligned with the use device  916 , so that the first reflected beam  915 A and the second reflected beam  915 B are actively detected at respective optical grating couplers on the use device  916  before application of the fill material  921 , while maintaining low light loss as the fill material  921  (optical index-matched) is applied and cured. In some embodiments, the active alignment of the beam steering structure  901  with the use device  916  is performed in an inward-reflecting version of the beam steering structure  901  where the bottom surface  906  of a base of the beam steering structure  901  is substantially parallel to the optical incidence plane of the use device  916 . 
       FIG. 10  shows a vertical cross-section view of a beam steering structure  1001  having a base, in accordance with some embodiments. The beam steering structure  1001  of  FIG. 10  is similar to the beam steering structure  901  of  FIG. 9 , except that an alignment structure  1011  and a ramp structure  1018  are position above a base of the beam steering structure  1001 . The beam steering structure  1001  includes an angled optical surface  1003  angled at a surface angle  1005  measured relative to a bottom surface  1006  of a base of the beam steering structure  1001 . In some embodiments, the beam steering structure  1001  can include an alignment structure  1011 , such as a v-groove, into which an optical fiber  1009  is positioned. A reflecting system  1013  is disposed on the angled optical surface  1003  to extend over at least an area of the angled optical surface  1003  upon which an input optical beam  1007  is incident. In some embodiments, the reflecting system  1013  can be formed as a multilayer stack of materials, such as a multilayer stack of films and/or coatings. The reflecting system  1013  functions to reflect the input optical beam  1007  that is emitted from the core of the optical fiber  1009  into a reflected beam  1015  directed toward a use device  1016 , such as a photonic chip. 
     The reflected beam  1015  can include a first reflected beam  1015 A of a first polarization and a second reflected beam  1015 B of a second polarization. The first reflected beam  1015 A is separated from the second reflected beam  1015 B by a beam spacing  1017 . The beam spacing  1017  is large enough to provide separation of the first reflected beam  1015 A and the second reflected beam  1015 B into respective optical channels of the use device  1016 . In some embodiments, the use device  1016  is a photonic chip that includes optical input couplers separated by the beam spacing  1017 . It should also be understood that in some embodiments, the direction of travel of the reflected beam  1015  and the input optical beam  1007  can be reversed, such that the reversed version of the reflected beam  1015  is reflected by the reflecting system  1013  on the angled optical surface  1003  into the core of the optical fiber  1009 . 
     As with the alignment structure  911 , the alignment structure  1011  facilitates placement of a waveguide, such as the optical fiber  1009 , that defines the input optical beam  1007 . Also, in some embodiments, as with the alignment structure  911 , the alignment structure  1011  can be configured as a v-groove array that has multiple v-grooves oriented to extend parallel to each other, with each v-groove configured to receive one optical fiber  1009 . And, similar to the ramp structure  918 , the ramp structure  1018  is configured to oriented the waveguide that defines the input optical beam  1007 , e.g., the optical fiber  1009 , at an angle  1019  relative to the bottom surface  1006  of the base of the beam steering structure  1001 . In some embodiments, the alignment structure  1011  is formed integrally with ramp structure  1018 . In some embodiments, the ramp structure  1018  is formed integrally with the beam steering structure  1001 . In some embodiments, the ramp structure  1018  and the beam steering structure  1001  are physically separate structures, with the ramp structure  1018  configured for installation on the beam steering structure  1001 . In some embodiments, the angle  1019  defines an angle between a direction of travel of the input optical beam  1007  and the bottom surface  1006  of the base of the beam steering structure  1001 . The beam steering structure  1001  and the ramp structure  1018  can be defined so that the input optical beam  1007  is incident upon the beam steering structure  1001  at a non-perpendicular angle of incidence so as to mitigate reflection of the input optical beam  1007  back into the waveguide, e.g., back into the core of the optical fiber  1009 . Also, in some embodiments, a fill material  1021  is used to secure the beam steering structure  1001 , the optical fiber  1009 , and the use device  1016  in a fixed spatial orientation with respect to each other. In various embodiments, the fill material  1021  can have a material optical index value similar to the core of the optical fiber  1009  and/or the beam steering structure  1001 . In some embodiments, the fill material  1021  is an optical-grade epoxy. In some embodiments, the fill material  1021  is a glass material having a low melting temperature. 
     It may be of interest to avoid back-reflections of the input optical beam  1007  that direct light back into the core of the optical fiber  1009 . Such back-reflections can lead to signal impairments (such as spectral interference and fading) and can possibly damage the optical source operating to generate the input optical beam  1007 . In some embodiments, the fill material  1021  is an optical index-matched material that has an optical index value substantially equal to the optical index value of either the beam-steering structure  1001  and/or the core of the optical fiber  1009 . Optical reflections of the input optical beam  1007  are minimized at surfaces of the core of the optical fiber  1009  and the beam steering structure  1001  when the core of the optical fiber  1009 , the fill material  1021 , and the beam steering structure  1001  have substantially the same optical index value. In some embodiments, an example common optical index value for the core of the optical fiber  1009 , the fill material  1021 , and the beam steering structure  1001  is 1.45. However, it should be understood that in other embodiments, the optical index value for the core of the optical fiber  1009 , the fill material  1021 , and the beam steering structure  1001  can be either less than 1.45 or greater than 1.45. 
     The angle of the incident light on each material interface within the beam steering structure  1001  can be large enough to reduce capture of back-reflected light by the core of the optical fiber  1009 . The ramp structure  1018  can be configured to ensure that the angle of the incident light on each material interface within the beam steering structure  1001  is large enough to reduce capture of back-reflected light by the core of the optical fiber  1009 . In some embodiments, the beam steering structure  1001  can include additional angled material interfaces to assist with preventing capture of back-reflected light by the core of the optical fiber  1009 . For example, in some embodiments, the facet of the beam steering structure  1001 , where the input optical beam  1007  is incident upon the beam steering structure  1001 , can be formed at an angle to reduce/prevent capture of back-reflected light by the core of the optical fiber  1009 . 
     In some embodiments, the beam steering structure  1001  can be actively aligned with the use device  1016 , so that the first reflected beam  1015 A and the second reflected beam  1015 B are actively detected at respective optical grating couplers on the use device  1016 , before application of the fill material  1021 , while maintaining low light loss as the fill material  1021  (optical index-matched) is applied and cured. In some embodiments, the active alignment of the beam steering structure  1001  with the use device  1016  is performed in an inward-reflecting version of the beam steering structure  1001  where the bottom surface  1006  of a base of the beam steering structure  1001  is substantially parallel to the optical incidence plane of the use device  1016 . 
       FIG. 11A  shows an isometric view of a beam steering structure  1101 , in accordance with some embodiments.  FIG. 11B  shows a top view of the beam steering structure  1101 , in accordance with some embodiments.  FIG. 11C  shows a side view of the beam steering structure  1101 , corresponding to view A-A as referenced in  FIG. 11B , in accordance with some embodiments.  FIG. 11D  shows an end view of the beam steering structure  1101 , corresponding to view B-B as referenced in  FIG. 11B , in accordance with some embodiments.  FIG. 11G  shows a close-up view of the area  1190  as referenced in  FIG. 11C , in accordance with some embodiments. 
     The beam steering structure  1101  includes an angled optical surface  1103  angled at a surface angle  1105  measured relative to a top surface  1106  of the beam steering structure  1101 . In some embodiments, the surface angle  1105  is about 39.6 degrees. However, in other embodiments, the surface angle  1105  can be either less than 39.6 degrees or greater than 39.6 degrees. In some embodiments, the beam steering structure  1101  is formed to have a width  1161  of about 4 millimeters (mm). However, in other embodiments, the width  1161  can be either less than 4 mm or greater than 4 mm. In some embodiments, the beam steering structure  1101  is formed to have a height  1163  of about 1.2 mm. However, in other embodiments, the height  1163  can be either less than 1.2 mm or greater than 1.2 mm. In some embodiments, the beam steering structure  1101  is formed to have a length  1165  of about 6 mm. However, in other embodiments, the length  1165  can be either less than 6 mm or greater than 6 mm. It should be understood that in various embodiments, the surface angle  1105 , the width  1161 , the height  1163 , and the length  1165  can be defined as needed for a particular implementation of the beam steering structure  1101 . 
     A reflecting system  1113  is disposed on the angled optical surface  1103  to extend over at least an area of the angled optical surface  1103  upon which an input optical beam  1107  is incident. In some embodiments, the reflecting system  1113  can be formed as a multilayer stack of materials, such as a multilayer stack of films and/or coatings. The reflecting system  1113  functions to reflect the input optical beam  1107  into a reflected beam  1115  directed toward a use device  1116 , such as a photonic chip. In some embodiments, the reflecting system  1113  is configured so that the reflected beam  1115  includes a first reflected beam  1115 A of a first polarization and a second reflected beam  1115 B of a second polarization, where the first reflected beam  1115 A is separated from the second reflected beam  1115 B by a beam spacing  1117 . The beam spacing  1117  is large enough to provide separation of the first reflected beam  1115 A and the second reflected beam  1115 B into respective optical channels of the use device  1116 . In some embodiments, the use device  1116  is a photonic chip that includes optical input couplers separated by the beam spacing  1117 . It should also be understood that in some embodiments, the direction of travel of the reflected beam  1115  and the input optical beam  1107  can be reversed, such that the reversed version of the reflected beam  1115  is reflected by the reflecting system  1113  on the angled optical surface  1103  into a core of an optical fiber. 
     The beam steering structure  1101  includes a v-groove array  1111  that has multiple v-grooves oriented to extend parallel to each other, with each v-groove configured to receive one optical fiber  1109 . In some embodiments, the v-groove array  1111  is formed integrally with the beam steering structure  1101 . The v-groove array  1111  facilitates placement of optical fibers  1109  that respectively define multiple input optical beams  1107 . In some embodiments, the v-groove array  1111  is configured to receive an array of optical fibers  1109 . In some embodiments, the array of optical fibers  1109  can be configured as a ribbon of optical fibers  1109 . In some embodiments, one or more of the optical fibers  1109  can include an optical lensing element, such as a GRIN lens or graded-index optical fiber. And, in some embodiments, the optical lensing element can cause the input optical beam  1107  to converge as it enters the beam steering structure  1101  and approaches the optical surface  1103 . 
       FIG. 11E  shows a close-up side view of the beam steering structure  1101 , with one of the optical fibers  1109  positioned in one of the v-grooves of the v-groove array  1111 , in accordance with some embodiments.  FIG. 11F  shows an end view of the beam steering structure  1101 , with one of the optical fibers  1109  positioned in one of the v-grooves of the v-groove array  1111 , corresponding to view C-C as referenced in  FIG. 11E , in accordance with some embodiments. In some embodiments, the v-groove array  1111  is configured to receive optical fibers  1109  that have a diameter  1167  of about 0.125 mm. In these embodiments, the v-grooves of the v-groove array  1111  can be configured to have a depth  1169  of about 0.156 mm. Also, in these embodiments, the v-grooves of the v-groove array  1111  can be configured to have an opening width  1171  of about 0.218 mm at the top surface  1106  of the beam steering structure  1101 . Also, in these embodiments, the v-grooves of the v-groove array  1111  can be configured to have a pitch  1173  of about 0.250 mm, where the pitch is measured between and perpendicular the centerlines of adjacent v-grooves of the v-groove array  1111  and in a plane parallel with the top surface  1106  of the beam steering structure  1101 . It should be understood that in various embodiments, the depth  1169 , the opening width  1171 , and the pitch  1173  of the v-groove array  1111  can be defined as needed for a specified optical fiber  1109  diameter  1167  (which may be either less than or greater than 0.125 mm) and for a specified optical grating coupler spacing/configuration on the use device  1116 . Therefore, in various embodiments, the depth  1169  can be either less than or greater than 0.156 mm, and/or the opening width  1171  can be either less than or greater than 0.218 mm, and/or the pitch  1173  can be either less than or greater than 0.250 mm. Also, in some embodiments, one or more of the depth  1169 , the opening width  1171 , and the pitch  1173  can be different for different v-grooves of the v-groove array  1111 . 
       FIG. 12  shows a schematic of a vertical cross-section of a beam steering structure  1201  positioned substantially parallel to a use device  1216 , in accordance with some embodiments. The beam steering structure  1201  includes an angled optical surface  1203  angled at a surface angle  1205  measured relative to a bottom surface  1206  of a base of the beam steering structure  1201 . A reflecting system  1213  is disposed on the angled optical surface  1203  to extend over at least an area of the angled optical surface  1203  upon which an input optical beam  1207  is incident. In some embodiments, the reflecting system  1213  can be formed as a multilayer stack of materials, such as a multilayer stack of films and/or coatings. The reflecting system  1213  functions to reflect the input optical beam  1207  into a reflected beam  1215  directed toward the use device  1216 , such as a photonic chip. The reflected beam  1215  includes a first reflected beam  1215 A of a first polarization and a second reflected beam  1215 B of a second polarization. The first reflected beam  1215 A is separated from the second reflected beam  1215 B by a beam spacing  1217 . The beam spacing  1217  is large enough to provide separation of the first reflected beam  1215 A and the second reflected beam  1215 B into respective optical channels of the use device  1216 . In some embodiments, the use device  1216  is a photonic chip that includes optical input couplers separated by the beam spacing  1217 . The example beam steering structure  1201  is configured to have a chip incidence angle  1218  of about 14 degrees. The chip incidence angle  1218  is measured between the direction of travel of the reflected beam  1215  (either  1215 A or  1215 B) and a vector perpendicular to a surface of optical incidence  1220  on the use device  1216  and within a reference plane that is coincident with the direction of travel of the input optical beam  1215  and perpendicular to the surface of optical incidence  1220  on the use device  1216 . 
       FIG. 13  shows a configuration of the reflecting system  1213 , in accordance with some embodiments. The horizontal axis in  FIG. 13  shows distance as measured perpendicularly away from the angled optical surface  1203  along the vector  1240  as shown in  FIG. 12 . The vertical axis in  FIG. 13  shows the optical index value of the material within the reflecting system  1213 . Therefore, the curve  1301  shown in  FIG. 13  shows the optical index value of the materials within the reflecting system  1213  as a function of distance measured perpendicularly away from the angled optical surface  1203  along the vector  1240 . Each change in optical index value within the reflecting system  1213  represents a transition between different material layers/films that collectively form the reflecting system  1213 .  FIG. 13  shows that the reflecting system  1213  includes a first reflecting region  1303 , a spacer region  1305 , and a second reflecting region  1307 . 
     As shown in  FIG. 13 , for the beam steering structure  1201 , the Brewster condition is met for n lo =1.45 and n hi =1.86 within the first reflective region  1303 . Also, as shown in  FIG. 13 , the second reflective region  1307  includes multiple layers/films of a high-index material (n=3.5), such as silicon. In various embodiments, the second reflective region  1307  can be formed of many different types of highly reflecting materials. In some embodiments, the second reflective region  13070  can be formed using a metal layer. At least one material used in the second reflecting region  1307  should have an optical index value substantially different from the materials used in the first reflecting region  1303 . Also,  FIG. 13  shows that the spacer region  1305  separates the first reflective region  1303  and the second reflective region  1307 . In the reflecting system  1213 , the spacer region  1305  has a thickness of about 5 micrometers, which provides for a reflected beam shift greater than about 10 micrometers, where the reflected beam shift corresponds to the beam spacing  1217  between the first reflected beam  1215 A and the second reflected beam  1215 B. In some embodiments, non-linear phase in the reflected beam  1215  can be minimized to avoid beam distortion, and can be further improved by numerical or empirical optimization. 
     A rough approximation of the beam spacing  1217  can be made using geometric drawings of the beam steering structure  1201 , such as shown in  FIG. 12 . And, improved estimates of the beam spacing  1217  can be extracted from the phase of the simulated reflectance.  FIG. 14  shows a plot of beam spacing  1217  as a function of the incidence angle between in input optical beam  1207  and the direction normal to angled optical surface for the beam steering structure  1201  having the reflecting system  1213  parameters of  FIG. 12 , in accordance with some embodiments.  FIG. 15  shows a plot of light loss (dB) as a function of angle deviation for the beam steering structure  1201 , where the angle deviation is defined as the difference between the incidence angle and the nominal designed angle, in accordance with some embodiments. It is understood that an optical beam typically can be decomposed into components with different incidence angle and may typically have small misalignment, and so optical properties (loss, beam spacing) should be suitable over a range of angular deviation. 
       FIG. 16  shows another configuration of the reflecting system  1213 , in accordance with some embodiments. As with  FIG. 13 , the curve  1601  shown in  FIG. 16  shows the optical index value of the materials within the reflecting system  1213  as a function of distance measured perpendicularly away from the angled optical surface  1203  along the vector  1240 .  FIG. 16  shows that the reflecting system  1213  includes a first reflecting region  1603 , a spacer region  1605 , and a second reflecting region  1607 . As shown in  FIG. 16 , for the beam steering structure  1201 , n lo =1.45 and n hi =1.75 (alumina) within the first reflective region  1603 . Also, as shown in  FIG. 16 , the second reflective region  1607  includes multiple layers/films of a high-index material (n=3.5) (silicon).  FIG. 16  also shows that the spacer region  1605  has a thickness of 5.8 micrometers. With the parameters as shown in  FIG. 16  for the reflecting system  1213 , the Brewster condition is met with the surface angle  1205  set to 39.6 degrees and with the chip incidence angle  1218  set to 10.7 degrees. Also, with these settings the beam spacing  1217  is about  13  micrometers. In some embodiments, the beam spacing  1217  can have artifacts that manifest with a sensitivity to the spacer region  1305 ,  1605  thickness. Therefore, in some embodiments, a total thickness of the reflecting system  1213  can be controlled in order to improve fabrication sensitivity and beam distortion.  FIG. 17  shows a plot of beam spacing  1217  as a function of the incidence angle for the beam steering structure  1201  having the reflecting system  1213  parameters of  FIG. 16 , in accordance with some embodiments. 
       FIG. 18  shows another configuration of the reflecting system  1213 , in accordance with some embodiments. As with  FIG. 13 , the curve  1801  shown in  FIG. 18  shows the optical index value of the materials within the reflecting system  1213  as a function of distance measured perpendicularly away from the angled optical surface  1203  along the vector  1240 .  FIG. 18  shows that the reflecting system  1213  includes a first reflecting region  1803 , a spacer region  1805 , and a second reflecting region  1807 . As shown in  FIG. 18 , for the beam steering structure  1201 , n lo =1.45 and n hi =2.0 (silicon nitride) within the first reflective region  1803 . Also, as shown in  FIG. 18 , the second reflective region  1807  includes multiple layers/films of a high-index material (n=3.5) (silicon).  FIG. 18  also shows that the spacer region  1805  has a thickness of 5.8 micrometers. 
       FIG. 19  shows another configuration of the reflecting system  1213 , in accordance with some embodiments. As with  FIG. 13 , the curve  1901  shown in  FIG. 19  shows the optical index value of the materials within the reflecting system  1213  as a function of distance measured perpendicularly away from the angled optical surface  1203  along the vector  1240 .  FIG. 19  shows that the reflecting system  1213  includes a first reflecting region  1903 , a spacer region  1905 , and a second reflecting region  1907 . As shown in  FIG. 19 , for the beam steering structure  1201 , n lo =1.45 (silica) and n hi =1.85 within the first reflective region  1903 . Also, as shown in  FIG. 19 , the second reflective region  1907  is formed by a metal coating, as indicated by the dashed vertical line. In some embodiments, the metal coating of the second reflective region  1907  is a layer of aluminum (nhigher˜1.3+i12.3). 
       FIG. 20  shows a variation of the reflecting system  1213  configuration of  FIG. 19 , in which the first reflecting region  1903  is reduced in thickness, in accordance with some embodiments. This example shows how a desired performance of the reflecting system  1213  can be achieved with a limited total thickness of the reflecting system  1213 . In some embodiments, fabrication capabilities may limit the total thickness of the reflecting system  1213 . For example, in some embodiments, the total thickness of the reflecting system  1213  may be limited to about 8 micrometers. Simulation results indicate that the beam spacing  1217  can be about 10 micrometers when the total thickness of the reflecting system  1213  is limited to about 8 micrometers. It should be appreciated that there is a tradeoff between ease of fabrication and light coupling loss through the beam steering structure  1201 . 
       FIG. 21  shows a flowchart of a method for optical beam turning in an optical data communication system, in accordance with some embodiments. The method includes an operation  2101  for positioning an optical fiber ( 109 ,  313 ,  413 ,  909 ,  1009 ) in an alignment structure ( 111 ,  311 ,  411 ,  911 ,  1011 ) of a beam steering structure ( 101 ,  301 ,  401 ,  901 ,  1001 ) such that an axis of a core of the optical fiber ( 109 ,  313 ,  413 ,  909 ,  1009 ) is oriented in a first direction ( 107 ,  315 ,  415 ,  907 ,  1007 ) within the alignment structure ( 111 ,  311 ,  411 ,  911 ,  1011 ). The first direction ( 107 ,  315 ,  415 ,  907 ,  1007 ) is oriented toward a reflecting system ( 113 ,  309 ,  409 ,  913 ,  1013 ) positioned on an angled optical surface ( 103 ,  307 ,  407 ,  903 ,  1003 ) of an end portion ( 102 ,  305 ,  405 , end of  901 , end of  1001 ) of the beam steering structure ( 101 ,  301 ,  401 ,  901 ,  1001 ). The angled optical surface ( 103 ,  307 ,  407 ,  903 ,  1003 ) is oriented at a non-zero angle relative to the first direction ( 107 ,  315 ,  415 ,  907 ,  1007 ). The reflecting system ( 113 ,  309 ,  409 ,  913 ,  1013 ) is configured to reflect incident light propagating along the first direction ( 107 ,  315 ,  415 ,  907 ,  1007 ) into a first reflected beam ( 115 A,  317 A,  417 A,  915 A,  1015 A) of a first polarization and a second reflected beam ( 115 B,  317 B,  417 B,  915 B,  1015 B) of a second polarization. The first reflected beam ( 115 A,  317 A,  417 A,  915 A,  1015 A) and the second reflected beam ( 115 B,  317 B,  417 A,  915 B,  1015 B) are separated by a beam spacing ( 117 ,  321 ,  421 ,  917 ,  1017 ) sized to direct the first reflected beam ( 115 A,  317 A,  417 A,  915 A,  1015 A) into a first optical communication channel and to direct the second reflected beam ( 115 B,  317 B,  417 B,  915 B,  1015 B) into a second optical communication channel. The method also includes an operation  2103  for transmitting light through the optical fiber ( 109 ,  313 ,  413 ,  909 ,  1009 ) so that the light travels from the optical fiber ( 109 ,  313 ,  413 ,  909 ,  1009 ) in the first direction ( 107 ,  315 ,  415 ,  907 ,  1007 ) and is incident upon the reflecting system ( 113 ,  309 ,  409 ,  913 ,  1013 ). The light incident upon the reflecting system ( 113 ,  309 ,  409 ,  913 ,  1013 ) is split into the first reflected beam ( 115 A,  317 A,  417 A,  915 A,  1015 A) and the second reflected beam ( 115 B,  317 B,  417 B,  915 B,  1015 B). 
     In some embodiments, the reflecting system ( 113 ,  309 ,  409 ,  913 ,  1013 ) is configured to set the beam spacing ( 117 ,  321 ,  421 ,  917 ,  1017 ) to a size that causes the first reflected beam ( 115 A,  317 A,  417 A,  915 A,  1015 A) to travel into a first optical grating coupler of a photonic chip and that causes the second reflected beam ( 115 B,  317 B,  417 B,  915 B,  1015 B) to travel into a second optical grating coupler of the photonic chip. In some embodiments, the alignment structure ( 111 ,  311 ,  411 ,  911 ,  1011 ) is shaped to receive and align the optical fiber ( 109 ,  313 ,  413 ,  909 ,  1009 ) such that the first direction ( 107 ,  315 ,  415 ,  907 ,  1007 ) is substantially parallel to a surface of optical incidence of the photonic chip. In some embodiments, the alignment structure ( 111 ,  311 ,  411 ,  911 ,  1011 ) is shaped to receive and align the optical fiber ( 109 ,  313 ,  413 ,  909 ,  1009 ) such that the first direction ( 107 ,  315 ,  415 ,  907 ,  1007 ) is not parallel to a surface of optical incidence of the photonic chip. 
     In some embodiments, the method includes an operation for disposing a fill material between the beam steering structure ( 101 ,  301 ,  401 ,  901 ,  1001 ) and the photonic chip such that the fill material secures the beam steering structure ( 101 ,  301 ,  401 ,  901 ,  1001 ) in a fixed spatial relationship with the photonic chip. In some embodiments, the method includes an operation for positioning an optical lensing element ( 106 ) between the optical fiber ( 109 ,  313 ,  413 ,  909 ,  1009 ) in the alignment structure ( 111 ,  311 ,  411 ,  911 ,  1011 ) and the end portion ( 102 ,  305 ,  405 , end of  901 , end of  1001 ) of the beam steering structure ( 101 ,  301 ,  401 ,  901 ,  1001 ). In some embodiments, the optical lensing element ( 106 ) is positioned and configured to direct convergence at a beam waist of the light propagating along the first direction ( 107 ,  315 ,  415 ,  907 ,  1007 ) through the end portion ( 102 ,  305 ,  405 , end of  901 , end of  1001 ) of the beam steering structure ( 101 ,  301 ,  401 ,  901 ,  1001 ). In some embodiments, the optical lensing element ( 106 ) is configured to provide high optical coupling efficiency, for example by placing the beam waist near the optical input/grating couplers. 
     In some embodiments, the reflecting system ( 113 ,  309 ,  409 ,  913 ,  1013 ) includes a first reflecting region that reflects light of the first polarization and passes through light of the second polarization. And, the reflecting system ( 113 ,  309 ,  409 ,  913 ,  1013 ) includes a second reflecting region that reflects light of the second polarization. And, the reflecting system ( 113 ,  309 ,  409 ,  913 ,  1013 ) includes a spacer region positioned between the first reflecting region and the second reflecting region. The spacer region is substantially transparent to light that passes through the first reflecting region. 
     It should be understood that the beam steering structures ( 101 ,  301 ,  401 ,  901 ,  1001 ) and corresponding reflecting systems ( 113 ,  309 ,  409 ,  913 ,  1013 ) provide for high-density optical fiber-to-photonic chip connectivity with integrated polarization beam splitting. Also, in various embodiments, the beam steering structures ( 101 ,  301 ,  401 ,  901 ,  1001 ) and corresponding reflecting systems ( 113 ,  309 ,  409 ,  913 ,  1013 ) are implemented in various optical fiber-to-photonic chip coupling devices. It should be understood that the beam steering structures ( 101 ,  301 ,  401 ,  901 ,  1001 ) and corresponding reflecting systems ( 113 ,  309 ,  409 ,  913 ,  1013 ) disclosed herein are useful in transmitting signals with two separate polarizations from a single optical fiber to two separate optical grating couplers, respectively. Also, it should be understood that the beam steering structures ( 101 ,  301 ,  401 ,  901 ,  1001 ) and corresponding reflecting systems ( 113 ,  309 ,  409 ,  913 ,  1013 ) disclosed herein are useful in transmitting signals with two separate polarizations, via two separate optical grating couplers, to the same optical fiber. 
     The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the invention, and all such modifications are intended to be included within the scope of the invention. 
     Although the foregoing invention has been described in some detail for purposes of clarity of understanding, it will be apparent that certain changes and modifications can be practiced within the scope of the invention description. Accordingly, the present embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalents of the described embodiments.