PATENT DOCUMENT

Publication Number: US-11881678-B1
Application Number: US-202017015766-A
Country: US
Kind Code: B1

Title: Photonics assembly with a photonics die stack

Abstract:
Configurations for a photonics assembly and the operation thereof are disclosed. The photonics assembly may include multiple photonics dies which may be arranged in an offset vertical stack. The photonics dies may emit light, and in some examples, an optical element may be a detector for monitoring properties such as the wavelength of the light. The photonics dies may be arranged in a stack as a package and the packages may be stacked or arranged side by side or both for space savings. The PIC may include combining and/or collimating optics to receive light from the photonics dies, a mirror to redirect the light, and an aperture structure. The aperture structure may include a region which is at least partially transparent such that light transmits through the transparent region of the aperture structure. The aperture structure may include an at least partially opaque region which may be used for directing and/or controlling the light launch position.

Claims:
What is claimed is: 
     
       1. A photonics system, comprising:
 a set of photonics dies arranged in an offset vertical stack, each photonics die in a different plane than each of the other photonics dies, the set of photonics dies comprising:
 a first light emitter configured to emit first light in a first wavelength range; and 
 a second light emitter configured to emit second light in a second wavelength range that is different than the first wavelength range, wherein the second light emitter is positioned between an overlapping region of two adjacent photonics dies of the set of photonic dies; and 
 
 an optical element configured to receive and collimate the first light and the second light into collimated light. 
 
     
     
       2. The photonics system of  claim 1 , wherein:
 each of the set of photonics dies is overlapping and offset in a first direction from all adjacent photonics dies; 
 each of the set of photonics dies emits light in a second direction that is orthogonal to the first direction; and 
 the photonics system further comprises a mirror configured to receive and reflect the collimated light from the optical element. 
 
     
     
       3. The photonics system of  claim 1 , further comprising an optical detecting element configured to detect optical signals of each photonics die of the set of photonics dies. 
     
     
       4. The photonics system of  claim 1 , wherein the set of photonics dies further comprises a detector configured to monitor at least one of the first or second light emitted by at least one of the first or second light emitters. 
     
     
       5. The photonics system of  claim 1 , further comprising:
 an aperture structure configured to receive the collimated and reflected light from the mirror and including:
 a first section that is at least partially optically transparent; and 
 a second section that is at least partially optically opaque; and 
 
 a prism configured to receive and reflect the collimated light from the optical element. 
 
     
     
       6. The photonics system of  claim 1 , wherein:
 the optical element is a first optical element; and 
 the photonics system further comprises: 
 a second optical element configured to receive the collimated light from the first optical element and to redirect the collimated light to the mirror. 
 
     
     
       7. The photonics system of  claim 1 , wherein:
 the optical element comprises an array of cylindrical microlenses; and 
 each cylindrical microlens is configured to receive the first light from a unique one of the set of photonics dies. 
 
     
     
       8. The photonics system of  claim 7 , further comprising a controllable actuator coupled to the optical element and configured to align the array of cylindrical microlenses. 
     
     
       9. The photonics system of  claim 1 , wherein the mirror is a microelectromechanical systems (MEMS) mirror comprising a set of individually controlled reflectors. 
     
     
       10. A method of operating a photonics system, comprising:
 emitting a first light having a first wavelength range from a first set of photonics dies; 
 emitting a second light having a second wavelength range from a second set of photonics dies; 
 receiving, by a first optical element, the first light and the second light; 
 receiving, by a second optical element, the first light and the second light; and 
 receiving, by a mirror, the first light and the second light from the second optical element; wherein: 
 the second optical element is configured to redirect the first and second wavelength ranges of light; and 
 the first set of photonics dies and the second set of photonics dies are arranged in an offset stack such that each of the first set of photonics dies and the second set of photonics dies is laterally offset from every adjacent one of the first set of photonics dies and the second set of photonics dies, a light emitter positioned between an overlapping region of two adjacent photonics dies of the first set of photonic dies. 
 
     
     
       11. The method of  claim 10 , wherein:
 the first light is emitted at a first time; and 
 the second light is emitted at a second time that is different from the first time. 
 
     
     
       12. The method of  claim 11 , further comprising:
 receiving, by an aperture structure, the first light and the second light from the mirror, the aperture structure comprising:
 a first section that is at least partially optically transparent; and 
 a second section that is at least partially optically opaque. 
 
 
     
     
       13. The method of  claim 12 , further comprising:
 receiving, by the mirror, one or more control signals from a controller; and 
 adjusting a position of the mirror based on the one or more control signals. 
 
     
     
       14. The method of  claim 13 , further comprising adjusting the position of the mirror at the first time such that the first wavelength range of light does not pass through the first section of the aperture structure. 
     
     
       15. The method of  claim 13 , further comprising:
 monitoring, by a detector coupled to a set of photonics dies, the first light and the second light; 
 determining whether a property of the first light or the second light meets a criterion; and 
 in the event the first light or the second light meets the criterion, adjusting the position of the mirror such that the first light and the second light pass through a first region of the aperture structure. 
 
     
     
       16. The method of  claim 10 , further comprising:
 receiving, by an actuator, a control signal; and 
 in response to receiving the control signal, actuating the actuator in order to align the first optical element with light emitted from at least one photonics die of the first and second sets of photonics dies. 
 
     
     
       17. The method of  claim 10 , further comprising:
 monitoring, by a detector coupled to the first and second sets of photonics dies, the first light and the second light. 
 
     
     
       18. A photonics assembly, comprising:
 a first photonics die including a first light emitter configured to emit light along a light path; 
 a second photonics die offset in a first direction from, and stacked below, the first photonics die, the second photonics die including a second light emitter configured to emit light along the light path, the second light emitter positioned in an overlapping region between the first photonics die and the second photonics die; 
 an optical element configured to receive light from the first and second light emitters along the light path, and further configured to collimate the received light; and 
 an aperture structure configured to receive light from the optical element along the light path; wherein: 
 the light path is in a second direction that is perpendicular to the first direction. 
 
     
     
       19. The photonics assembly of  claim 18 , further comprising a second optical element configured to receive collimated light from the optical element and redirect the collimated light to the aperture structure. 
     
     
       20. The photonics assembly of  claim 18 , further comprising a third photonics die offset in the first direction from, and stacked above, the first photonics die; wherein:
 the third photonics die is configured to receive light from the first photonics die; and 
 the third photonics die is further configured to monitor the light from the first photonics die.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a nonprovisional of and claims the benefit under 36 U.S.C. § 119(e) of U.S. Provisional Patent Application No. 62/897,647, filed Sep. 9, 2019, and entitled “Stacked Photonics Integrated Circuit,” the contents of which are incorporated herein by reference as if fully disclosed herein. 
    
    
     FIELD 
     This disclosure relates generally to photonics architectures packaged into a portable electronic device and, more specifically, to a photonics assembly with photonics dies arranged in a stack. 
     BACKGROUND 
     Photonics devices may be used for generating, processing, sensing, and/or outputting light. They may be utilized in many fields of endeavor, such as telecommunications, information processing, and medical fields, and may be employed in various devices such as bar code scanners, surgical endoscopes, photonic gyroscopes, and spectrometers. The architectures of these systems may include multiple components and circuitry which may affect the size of the device into which they are incorporated. 
     Due to the trend of creating ever smaller, thinner, and more compact electronic devices, the emphasis on the size and thickness of various components inside of the electronic device has increased. In some examples, a particular size of the electronic device is targeted and each component within the electronic device is given a maximum allowable form factor in order to support integration into the device. For example, a maximum area and/or thickness that the component may occupy in the electronic device may be limited. In some examples, integrating a photonics circuit into a particular device may be difficult due to the size constraints and limited area the photonics circuits may be allowed to occupy. 
     SUMMARY 
     Embodiments of the systems, devices, methods, and apparatuses described in the present disclosure are directed to stacked photonics dies. Also described are systems, devices, methods, and apparatuses directed to stackable photonics dies which may emit and detect light. Additionally, the photonics dies may have different functionalities and the dies may be modularly configured in a photonics assembly. 
     In some examples, the present disclosure describes a photonics system. The photonics system may include a set of photonics dies arranged in an offset vertical stack, each photonics die in a different plane than each of the other photonics dies. The photonics dies may include a first light emitter configured to emit first light in a first wavelength range, a second light emitter configured to emit second light in a second wavelength range that is different than the first wavelength range, an optical element configured to receive and collimate the first light and the second light into collimated light, and a mirror configured to receive the collimated light from the optical element and reflect the collimated light received from the optical element. Each of the set of photonics dies may be overlapping and offset in a first direction from all adjacent photonics dies and each of the set of photonics dies may emit light in a second direction that is orthogonal to the first direction. The photonics system may also include an optical element configured to detect light emitted by one or more of the photonics dies of the stack, where the light may be detected for each individual die emitting at different times, or the light may be detected for light being emitted at approximately the same time by multiple photonics dies. In some examples, the optical element may detect light emitted by one or more photonics dies at different times or light emitted at the same time to perform wavelength locking or reference measurements for the photonics dies of the stack. In some examples, the optical element routes optical signals between at least two of the set of photonics dies. The set of photonics dies may include a detector configured to monitor at least one of the first or second light emitted by at least one of the first or second light emitters. 
     In some examples, the photonics system may include an aperture structure configured to receive the collimated and reflected light from the mirror, and the aperture structure may include a first section that is at least partially optically transparent and a second section that is at least partially optically opaque. In some examples, the photonics system may include a prism configured to receive the collimated light from the optical element and reflect the collimated light received from the optical element. In some examples, the optical element may be a first optical element and the photonics system may include a second optical element configured to receive the collimated light from the first optical element and to redirect the collimated light to the mirror. In some examples, the optical element may include an array of cylindrical microlenses, and each cylindrical microlens is configured to receive the first light from a unique one of the set of photonics dies. In some examples, the photonics system may include a controllable actuator coupled to the optical element and configured to align the cylindrical microlens array. In some examples, the mirror may be a microelectromechanical systems (MEMS) mirror comprising a set of individually controlled reflectors. 
     In some examples, the present disclosure describes a method of operating a photonics system. The method may include emitting a first light having a first wavelength range from a first set of photonics dies, emitting a second light having a second wavelength range from a second set of photonics dies, receiving, by a first optical element, the first light and the second light, receiving, by a second optical element, the first light and the second light, and receiving, by a mirror, the first light and the second light from the second optical element. In some examples, the second optical element is configured to redirect the first and second wavelength ranges of light, and the first set of photonics dies and the second set of photonics dies are arranged in an offset stack such that each of the first set of photonics dies and the second set of photonics dies is laterally offset from every adjacent one of the first set of photonics dies and the second set of photonics dies. In some examples of the method, the first light is emitted at a first time and the second light is emitted at a second time that is different from the first time. 
     In some examples, the method may also include receiving, by an aperture structure, the first light and the second light from the mirror, and the aperture structure may include a first section that is at least partially optically transparent and a second section that is at least partially optically opaque. In some examples, the method may include receiving, by the mirror, one or more control signals from a controller, and adjusting a position of the mirror based on the one or more control signals. In some examples, the method may also include adjusting the position of the mirror at the first time such that the first wavelength range of light does not pass through the first section of the aperture structure. 
     In some examples, the method may include monitoring, by a detector coupled to the set of photonics dies, the first light and the second light, determining whether a property of the first light or the second light meets a criterion and, in the event the first light or the second light meets the criterion, adjusting the position of the mirror such that the first light and the second light passes through a first region of the aperture structure. In some examples, the method may include receiving, by an actuator, a control signal, and, in response to receiving the control signal, actuating the actuator in order to align the first optical element with the light emitted from at least one of the photonics dies of the sets of first and second photonics dies. In some examples, the method may include monitoring, by a detector coupled to the first and second sets of photonics dies, the first light and the second light. 
     In some examples, the present disclosure describes a photonics assembly. The photonics assembly may include a first photonics die including a first light emitter configured to emit light along a light path, a second photonics die offset in a first direction from, and stacked below, the first photonics die, the second photonics die including a second light emitter configured to emit light along the light path, an optical element configured to receive light from the first and second light emitters along the light path, and further configured to collimate the received light, and an aperture structure configured to receive light from the optical element along the light path, where the light path is in a second direction that is perpendicular to the first direction. In some examples, the photonics assembly may include a second optical element configured to receive collimated light from the optical element and redirect the light to the aperture structure. In some examples, the photonics assembly may include a third photonics die offset in the first direction from, and stacked above, the first photonics die where the third photonics dies is configured to receive light from the first photonics die, and the third photonics die is further configured to monitor the light from the first photonics die. 
     In addition to the example aspects and embodiments described above, further aspects and embodiments will become apparent by reference to the drawings and by study of the following description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    illustrates one example of a photonics assembly. 
         FIG.  2 A  illustrates a photonics die stack and an optical element. 
         FIG.  2 B  illustrates multiple packages including photonics dies. 
         FIG.  2 C  illustrates multiple packages including photonics dies. 
         FIG.  3 A  illustrates a cross-sectional view of a partial photonics assembly. 
         FIG.  3 B  illustrates a cross-sectional view of a partial photonics assembly. 
         FIG.  3 C  illustrates a cross-sectional view of a partial photonics assembly. 
         FIG.  4 A  illustrates a side view of a light combining optical element. 
         FIG.  4 B  illustrates a side view of a light combining optical element coupled to an actuator. 
         FIG.  5 A  illustrates a side view of components of a photonics die during processing. 
         FIG.  5 B  illustrates a side view of components of a photonics die during processing. 
         FIG.  5 C  illustrates a side view of components of a photonics die during processing. 
         FIG.  5 D  illustrates a side view of components of a photonics die during processing. 
         FIG.  5 E  illustrates a side view of components of a photonics die during processing. 
         FIG.  5 F  illustrates a side view of components of a photonics die during processing. 
         FIG.  6    illustrates a light emitter layout on an epitaxial element of the photonics die. 
         FIG.  7 A  illustrates a layout of epitaxial elements on a photonics die. 
         FIG.  7 B  illustrates a photonics die stack. 
         FIG.  7 C  illustrates a photonics die stack. 
         FIG.  7 D  illustrates a photonics die stack. 
         FIG.  8    illustrates a package with photonics dies. 
         FIG.  9    is a flowchart of a process for operating a photonics assembly using a linear scan. 
         FIG.  10    is a flowchart of a process for operating a photonics assembly for monitoring purposes. 
         FIGS.  11 A- 11 J  illustrate both side and top views of a photonics die with III-V materials. 
         FIG.  12    is a flowchart of a process flow for fabricating a photonics die with III-V materials. 
         FIG.  13    is a flowchart of a process flow for fabricating a photonics die with III-V materials. 
     
    
    
     The use of cross-hatching or shading in the accompanying figures is generally provided to clarify the boundaries between adjacent elements and also to facilitate legibility of the figures. Accordingly, neither the presence nor the absence of cross-hatching or shading conveys or indicates any preference or requirement for particular materials, material properties, element proportions, element dimensions, commonalities of similarly illustrated elements, or any other characteristic, attribute, or property for any element illustrated in the accompanying figures. 
     Additionally, it should be understood that the proportions and dimensions (either relative or absolute) of the various features and elements (and collections and groupings thereof) and the boundaries, separations, and positional relationships presented between them, are provided in the accompanying figures merely to facilitate an understanding of the various embodiments described herein and, accordingly, may not necessarily be presented or illustrated to scale, and are not intended to indicate any preference or requirement for an illustrated embodiment to the exclusion of embodiments described with reference thereto. 
     DETAILED DESCRIPTION 
     Reference will now be made in detail to representative embodiments illustrated in the accompanying drawings. It should be understood that the following description is not intended to limit the embodiments to one preferred embodiment. To the contrary, it is intended to cover alternatives, modifications, and equivalents as can be included within the spirit and scope of the described embodiments as defined by the appended claims. 
     Generally noise, such as random or semi-random noise, may be present in various types of imaging systems and may cause unwanted modifications of a signal. In some examples, the noise in the imaging systems may be coherent noise. Noise may degrade images in systems such as medical ultrasound systems, radar systems, projection systems, or any coherent imaging system by causing graininess, granular patterns, or intensity patterns in the image. Some systems may produce signals with so much noise that it may be difficult to determine the measured signal. In some examples, coherent multipath-interference may be a noise source, one example of which may be speckle noise. 
     Because of the increasing emphasis on smaller, more compact electronic devices, the size and thickness of the components inside of the electronic device may be limited. In some examples, a particular size of the electronic device is targeted and each component within the electronic device is given a maximum form factor or area that the component may occupy within the electronic device. Accordingly, the physical configuration of the integrated circuit, such as a photonics integrated circuit and/or photonics assembly, may become increasingly important to the form factor of the device. 
     As discussed herein, photonics assemblies may be arranged in various configurations such that they may perform desired operations while being extremely compact in order to fit into relatively small spaces within electronics devices. A sample photonics assembly may include one or more photonics dies which may be arranged in an offset vertical stack. The photonics assembly may include photonics dies capable of emitting one or more wavelengths and/or one or more wavelength ranges of light. Each such photonics die also may be configured as a detector for monitoring properties of light emitted from a different photonics die. Because each of the photonics dies may perform different functions and may be modularly configured, the photonics assembly may have a collective functionality defined by individual capabilities of each die. 
     The offset vertical stack configuration of the photonics dies may partially expose a surface of each photonics die in the stack. The exposed surface of a photonics die may be used for electrical connections such as wire bonds and bond pads, and detecting and/or routing of optical signals, thus resulting in space savings and a smaller footprint for the stack. 
     The photonics assembly may include optical elements, such as a mirror and an aperture structure. The photonics dies may emit light to the optical elements, which may combine, collimate, and/or redirect the light to the aperture structure. The aperture structure may include a transparent region or opening configured to allow light to pass through the aperture structure, may direct or control the light launch position, and may include an opaque region configured to block light while the wavelength and/or power of the emitted light stabilizes. Although referred to herein as an “aperture structure”, the aperture structure may be a layer with an opening which may be physically connected to or spaced apart from a photonics die, and this layer may control the emitting or receiving of stray or unwanted light. 
     These and other embodiments are discussed below with reference to  FIGS.  1 - 13   . However, those skilled in the art will readily appreciate that the detailed description given herein with respect to these Figures is for explanatory purposes only and should not be construed as limiting. 
     Directional terminology, such as “top”, “bottom”, “upper”, “lower”, “above”, “below”, “beneath”, “front”, “back”, “over”, “under”, “left”, “right”, and so forth, is used with reference to the orientation of some of the components in some of the figures described below. Because components in various embodiments can be positioned in a number of different orientations, directional terminology is used for purposes of illustration only and is in no way limiting. The directional terminology is intended to be construed broadly, and therefore should not be interpreted to preclude components being oriented in different ways. 
     As used throughout this specification, a reference number without an alpha character following the reference number can refer to one or more of the corresponding references, the group of all references, or some of the references. For example, “ 210 ” can refer to any one of the photonics dies  210  (e.g., photonics die  210 A, photonics die  210 B, etc.), can refer to all of the photonics dies  210 , or can refer to some of the photonics dies (e.g., both photonics die  210 A and photonics die  210 B) depending on the context in which it is used. 
     Overview of the Photonics Assembly 
       FIG.  1    illustrates an example photonics assembly which may include an interface  180 , a light emitter  107 , a detector  130 , and a controller  140 . The interface  180  can include an external surface (e.g., system interface  380  illustrated in  FIG.  4 A ) of a device which can accommodate light transmission therethrough. In some examples, the photonics assembly  100  can include an aperture structure  160  including one or more regions (e.g., a transparent region  170 , an opaque region, a translucent region, a reflective region, a region having a different refractive index than surrounding material, and so on) configured to shape one or more of the location(s), angle(s), and/or shape(s) of light exiting the photonics assembly  100 . By limiting the location and/or angles of light entering a measured sample volume  120 , the light incident on a measured sample volume  120 , and/or exiting from a measured sample volume  120  can be selectively limited. Although depicted in  FIG.  1   , the measured sample volume  120  is not included in the photonics assembly  100 . The terms “photonics assembly” and “photonics system” may be used interchangeably herein. 
     While operating the photonics assembly  100 , the measured sample volume  120  can be located close to, or touching at least a portion of, the photonics assembly  100  (e.g., photonics system interface). The one or more light emitters  107  can be coupled to the controller  140 . The controller  140  can send a signal (e.g., current or voltage waveform) to control the light emitters  107 , which can emit light. The one or more light emitters  107  may be included in one or more epitaxial elements (not shown in  FIG.  1   ), which, in turn, may be included in the photonics dies, which will be discussed in detail herein with reference to  FIGS.  7 A- 7 D . Discussions herein may reference the photonics dies emitting light, though it may be a light emitter that is part of the epitaxial element, which is then part of the photonics die that may be emitting light. As such, discussions of the photonics dies emitting light are understood to encompass a light emitter emitting light, so long as that light emitter is part of the photonics die. 
     Depending on the nature of the measured sample volume  120 , light can penetrate into the measured sample volume  120  to reach one or more scattering sites and can return (e.g., reflect and/or scatter back) towards the photonics assembly  100  with a controlled path length. The return light that enters back into the photonics assembly  100  may be directed, collimated, focused, and/or magnified. The return light can be directed towards the detector  130 . The detector  130  can detect the return light and can send an electrical signal indicative of the amount of detected light to the controller  140 . 
     Additionally or alternatively, the light emitter  107  can optionally emit light towards the reference (not illustrated in  FIG.  1   ). The reference can redirect light towards optics which may include, but are not limited to, a mirror, lenses, and/or a filter, and also may redirect light towards a sample with known optical properties. The optics may direct, collimate, focus, and/or magnify light towards the detector  130 . The detector  130  can measure light reflected from the reference and can generate an electrical signal indicative of this reflected light for quality purposes. As illustrated in  FIG.  1   , the light emitter  107  emits light toward an outcoupler or mirror  150 . In some examples, the light emitter  107  may emit light toward a prism. 
     The controller  140  can be configured to receive one or more electrical signals from the detector  130 , and the controller  140  (or another processor) can determine the properties of a sample from the received electrical signals. In some instances, the detector  130  can receive at least two electrical signals, where one electrical signal can be indicative of light reflected/scattered from the measured sample volume  120 , and another electrical signal can be indicative of light reflected/scattered from the reference. Additionally, the detector may be configured to transmit the electrical signals to the controller  140 . In some examples, each of the different electrical signals can be a time-multiplexed signal. For example, each of the different electrical signals for the measured sample volume and the reference may alternate with one another at different points in time. In other instances, two or more electrical signals can be received by different detector pixels concurrently and each of the electrical signals may include information indicative of different light information such as wavelength and intensity. 
     Photonics Die Stack 
       FIG.  2 A  illustrates a photonics die stack and an optical element. The photonics die stack or stack  211  can take the form of photonics dies  210  arranged in a vertical offset stack, in which each of the individual photonics dies may be referred to with a separate element number such as  210 A,  210 B,  210 C, and so forth. As discussed herein, the photonics dies may have different functionality from one another or the same functionality as one another depending on the application.  FIG.  2 A  illustrates ten photonics dies  210  for explanatory purposes only; the photonics assembly  100  may include any number of photonics dies. As illustrated in  FIG.  2 A , each photonics die  210  can include a first edge  215 A, a second edge  215 B, a third edge  215 C, and a fourth edge  215 D. The first edge  215 A may be the side of the photonics die from which the exposed surface of the photonics die  210  extends. The terms “photonics die stack” and “stack” may be used interchangeably herein. Additionally, as used herein, a stack may include multiple photonics dies, where the dies may be arranged in an aligned configuration or may be arranged such that each photonics die may be offset from the photonics dies positioned above and below it. 
     In  FIG.  2 A , a photonics die  210 A may be stacked on top of and offset from photonics die  210 B; each photonics die may be offset from the photonics dies immediately above and below it. Although in  FIG.  2 A  the photonics dies of the stack are offset from one another in one direction, the photonics dies of the stack may be offset in more than one direction. For example, the photonics dies may also be offset from one another so that the second edges  215 B are offset from one another in the stack  211  (e.g., leaving an exposed surface extending from multiple edges of the die in question). Additionally, the photonics dies are depicted in  FIG.  2 A  as being the same size, but the photonics dies may be different sizes. Further, the photonics dies in  FIG.  2 A  are illustrated as consistently offset in one direction, but every other photonics die may have aligned edges in the offset direction. For example, a first and a third photonics die may be aligned with one another, but a second photonics die that is located between the first and third photonics dies may be offset from the first and third photonics dies. 
     In some examples, a surface of each of the photonics dies may be exposed and bonded connections  232  and may be attached to one or more of the photonics dies  210 . The bonded connections  232  may be used to electrically connect components of a respective photonics die  210  to a controller (not shown in  FIG.  2 A ). In some examples, the bonded connections  232  may be wire bonds. Although  FIG.  2 A  illustrates bonded connections  232  forming a connection between the photonics die in the bottom of stack  211  to a substrate, in some examples the bonded connections  232  may attach more than one photonics die to the substrate. In some examples, the bonded connections  232  from a given photonics die  210  may be electrically isolated from the bonded connections  232  of another photonics die  210 . 
     In some examples, although not illustrated in  FIG.  2 A , one or more epitaxial elements may be bonded to the photonics die  210 A, one or more epitaxial elements may be bonded to the photonics die  210 B, and so forth. Additionally, one or more light emitters may be bonded to each of the epitaxial elements and the light emitters may emit a single wavelength or may emit a wavelength range. In this way, each of the photonics dies  210  may emit light at a wavelength or across a wavelength range, thus the stack  211  may provide light across a narrow wavelength range such as less than 200 nm or across a broad wavelength range such as 1400 nm-2400 nm. The configurations and epitaxial elements will be discussed with reference to  FIGS.  7 A- 7 D . 
     In some examples, the stack  211  may have all four edges aligned or approximately aligned in each direction. In this aligned configuration, the surfaces of the photonics dies along first edge  215 A may not be exposed. To create connections, such as electrical connections from a photonics die  210  to another location (e.g., a substrate or another photonics die  210 ), vias may extend through one or more dies of the photonics assembly  100 . Additionally or alternatively, the photonics assembly may include connections that are formed between the photonics dies; these connections may carry electrical signals, including common signals, or may be used to ground one or more dies. 
     Although  FIG.  2 A  illustrates each of the photonics dies being offset from one another, in some examples, two or more photonics dies may be aligned in each direction and offset from the other photonics dies. In some examples, the exposed surfaces of the photonics dies can be created by different sized or shaped photonics dies  210 . For example, photonics die  210 A may be smaller in one direction than photonics die  210 B, which may result in part of the surface of photonics die  210 B being exposed. 
     As previously described, each photonics die  210  can include a first edge  215 A, a second edge  215 B, a third edge  215 C, and a fourth edge  215 D. In some embodiments the second edge  215 B (or any other edge), may be adjacent to the optical paths  234  of the optical element  212 . The optical paths can be waveguides used for monitoring optical properties such as wavelengths of the light emitted by the photonics dies  210 . In some examples, one or more of photonics dies  210  may be detectors employed to monitor these optical properties. For example, a single photonics die may include one or more detectors and/or one or more emitters. Accordingly, the stack  211  may include photonics dies  210  which may be light emitting photonics dies and/or detector photonics dies. In some examples, functionality may be divided between different photonics dies to provide a collective functionality of stack  211 , thus allowing a modular and flexible stack design. In one example, the optical paths  234  can optically couple light from a light emitting photonics die  210 A to a detector on the photonics die  210 B. In another example, a light emitting photonics die  210 A may emit a first wavelength range to a detector on photonics dies  210 B and  210 C, where the detector on photonics die  210 B may be configured to detect wavelengths, and the detector on photonics die  210 C may be configured to detect optical power. 
     In some embodiments, a third edge  215 C of each photonics die  210  (or any other suitable edge) may transmit light  109  out of the stack  211 . In some examples, the third edge  215 C of at least two or more photonics dies  210  may be aligned or substantially aligned with one another. The emitted light  209  may be emitted from one or more photonics dies. As shown in  FIG.  2 A , photonics die  210 A may emit light  109 A which may be in approximately the same plane as photonics die  210 A. Similarly, photonics die  210 B may emit light  109 B which may be in approximately the same plane as photonics die  210 B. In some examples, the photonics die  210 A plane may be approximately parallel to the photonics die  210 B plane. Additionally,  FIG.  2 A  illustrates three photonics dies emitting light  109  for explanatory purposes only, as any number of photonics dies may emit light  109 . 
     In some examples, the stack may have a fourth edge  215 D of adjacent photonics dies  210 . The fourth edge  215 D may be offset in a manner similar to first edge  215 A, and may optionally include bonded connections  232 , similar to the first edge  215 A. 
       FIG.  2 B  illustrates multiple packages including photonics dies. In  FIG.  2 B , a photonics structure  200  may include a first package  227 A which may be stacked above a second package  227 B. The packages  227  may include photonics dies  210  which may emit light  109  toward optical element  229  and then to the mirror  150 . The functionality of the mirror  150  was discussed with respect to  FIG.  1   . Although the mirror is used herein, a prism may also be used to perform a similar function as the mirror. In  FIG.  2 B , the light may be emitted in the same direction as the stack offset and from the first edge  215 A of the stack  211 , as opposed to the light being emitted out of the third edge  215 C as discussed in  FIG.  2 A . The term “package” as used herein may include one or more photonics dies, a mounting substrate, die attach films, and so forth. 
     In  FIG.  2 B , the package  227  may include photonics dies  210  arranged in a vertical offset stack, in which each of the individual photonics dies may be referred to as  210 A,  210 B, and so forth. Package  277 B is located below package  227 A and may include the same components in the same configuration as package  227 .  FIG.  2 B  illustrates two packages for explanatory purposes only and the photonics system  200  may include any number of packages. The number of packages in a given embodiment may depend on a target form factor of the photonics circuitry and/or photonics system, which may depend at least in part on the form factor of the electronics device into which it will be incorporated. 
     In some examples, two separate packages may each include photonics dies with the same or different functionalities. The functionality of the photonics dies within each of the packages may depend on any number of factors such as, but not limited to, the wavelengths emitted by the photonics dies, the optical combiners or multiplexers, the optical switches, the waveguides, the optical power in a wavelength range, any combination thereof, and so forth. In some examples, two packages may each include a switch and five photonics dies. By including five photonics dies, the switch may select between each of the five photonics dies in the two packages faster than one package with a single switch and ten photonics dies. In another example of packages with photonics dies with different functionalities, each package may have five photonics dies, where each photonics die may emit a different wavelength range. For some applications the photonics assembly may need higher power in five wavelength ranges. In this example, two packages with five photonics dies per package, where the photonics dies within a package each emit a different wavelength range, may be more useful than a stack of ten different photonics dies where each photonics die emits one of ten different wavelength ranges. In some examples, the emitted wavelength ranges may be 1400 nm-2400 nm. Five and ten photonics dies per package are discussed for explanatory purposes only and, in other embodiments, a package may include any number of photonics dies. 
       FIG.  2 C  illustrates multiple packages including photonics dies. In  FIG.  2 C , a photonics structure  205  may include a first package  237  which may be adjacent to a second package  247 . The packages  237  and  247  may include photonics dies  210 A,  210 B, . . .  210 N, which may emit light (light not illustrated in  FIG.  2 C ) toward optical elements  239 . Similar to  FIG.  2 B , the light in  FIG.  2 C  may be emitted in the same direction as the stack offset. 
     Similar to the packages described with respect to  FIG.  2 B , the package  237  may include photonics dies  210  arranged in a vertical offset pattern as discussed above. Additionally, package  247  may include multiple photonics dies  210  arranged in a vertical offset pattern, similar to package  237 . 
       FIG.  2 C  illustrates two packages for explanatory purposes only; the photonics structure  205  may include any number of packages. Similar to  FIG.  2 B , the number of packages which may be adjacent to one another may depend on a target form factor of the photonics circuitry and/or photonics assembly, which may depend at least in part on the form factor of the electronics device into which it will be incorporated. In some examples, the packages may be stacked side by side and above one another and may be configured in any appropriate arrangement which may include aligning the packages with one another vertically, horizontally, or offsetting the packages relative to one another in any direction. 
       FIG.  3 A  illustrates a cross-sectional view of a partial photonics assembly.  FIG.  3 A  is a cross-section taken normal to a second edge  215 B of a stack of photonics dies with an optical element. Additionally, due to the direction of the-cross section of the photonics dies, the offset of the stack is not apparent in  FIG.  3 A . Structure  300  can include multiple photonics dies  210  incorporated into a stack  211 . As illustrated in  FIG.  3 A , the photonics dies can be arranged in a stacked configuration, where photonics die  210 A may be positioned above photonics die  210 B, photonics die  210 B may be positioned above photonics die  210 C, and so forth. 
     In some examples, the photonics die  210 A can be configured to emit light  109 A having a first wavelength or a first wavelength range; the photonics die  210 B can be configured to emit light  109 B including a second wavelength or a second wavelength range; photonics die  210 C can be configured to emit light including a third wavelength or a third wavelength range; and so forth. In this manner, each photonics die  210  of the structure  300  can be configured to emit light having a unique wavelength or unique wavelength ranges. 
     In some examples, the photonics die  210 A may include one or more epitaxial elements. Additionally, one or more light emitters may be bonded to each of the epitaxial elements. Thus, the wavelength range of light emitted by the photonics die  210 A depends on the number of light emitters and the number of epitaxial elements. In some examples, each epitaxial element may emit light over a wavelength range of 0.05 μm-0.075 μm. In some examples, each epitaxial element may emit light over a narrow wavelength range of approximately 0.066 μm. 
     In some examples, the combined wavelength range of multiple photonics dies  210  may output or provide a broadband wavelength range, which may be a set of emitted broadband wavelengths over an approximate range of 1 μm. In some examples, the 1 μm emitted broadband wavelength may be in the “broadband” range of approximately 1.0 μm to 3.0 μm. Accordingly, embodiments described herein may operate over, or employ, an operating range that may correspond to, or be encompassed in, a broadband wavelength range. Examples of such operating ranges include 1.0 μm-2.0 μm, 1.3 μm-2.3 μm, 1.4 μm-2.4 μm, 1.5 μm-2.5 μm, and so forth. Although specific wavelength ranges may be discussed, any appropriate wavelength or wavelength range may be emitted by the photonics elements described herein. Also as used herein, a “narrow wavelength range” generally refers to less than 0.07 μm. Although specific wavelength ranges of light have been discussed, any appropriate wavelength or wavelength range may be emitted by the photonics dies depending on the use case. 
     The structure  300  may also include any or all of a light combining optical element  222 , a light directing optical element  224 , a mirror  226 , an aperture structure  228 , and an optical element  212 . Although the light combining optical element  222  and light directing optical element  224  are illustrated in  FIG.  3 A  as two separate elements, in some examples, the functions of these two elements may be combined into one optical element such as a toroidal optical element. Additionally, the light combining optical element  222  is illustrated as a single optical element but the function may be performed by multiple optical elements. For example, the light  109  received from the stack  211  may be combined by a combining optical element and then collimated by a collimating element, and thus two optical elements may perform the functions of the single light combining optical element  222 . Similarly, while the light directing optical element  224  is depicted as a single optical element, two or more lenses may be used to redirect the light to the mirror. In some examples, a prism may perform a similar function as the mirror. Additionally, in some examples, the light combining optical element may also function as a light coupling element. In further examples, the light directing optical element may be any optical element that redirects light such as lenses with negative power or positive power. 
     In some examples, the photonics dies  210  may emit light  109  at an approximately normal angle of incidence to the receiving surface of the light combining optical element  222 . In  FIG.  3 A , the light combining optical element  222  may receive light  109  emitted by the photonics dies  210  of the stack  211 . In some examples, the light combining optical element  222  can be configured to combine light from multiple photonics dies  210  of the stack  211 . The light combining optical element  222  may be further configured to collimate and/or combine light received from the stack  211 . 
     The light combining optical element  222  may pass light  111 A to the light directing optical element  224 . As illustrated in  FIG.  3 A , the light directing optical element  224  can be configured to receive light  111 A from the light combining optical element  222 . In some examples, the light directing optical element  224  may direct or steer the light  113  to the mirror  226 . 
     The mirror  226  may receive light from the light directing optical element  224  and redirect light to the aperture structure  228 . In some examples, the mirror  226  can be arranged such that its reflecting plane is non-perpendicular and non-parallel to the plane of the photonics dies  210 . In some instances, the aperture structure  228  may be located above the stack  211 . In some embodiments, the aperture structure  228  may have a plane that is parallel or close to parallel (e.g., within 5 degrees) from the plane of at least one photonics die  210 . 
     The aperture structure  228  can include a transparent region  228 A and an opaque region  228 B. The transparent region  228 A may allow light  113  to pass through. The transparent region(s) may include material and/or an opening and may be at least partially transparent (for example, permitting at least 50% of light to pass therethrough). The opaque region  228 B may not allow incident light to pass through. In some examples, the opaque region  228 B may be configured to absorb or block incident light. 
     In some examples, light may pass through the transparent region  228 A of the aperture structure  228  and form a “stripe” of light. The stripe of light may be formed due to the varying positions of the photonics dies  210  and/or the varying positions of the one or more light emitters within each photonics die  210 . Multiple light emitters in a photonics die are discussed with reference to  FIG.  6   . In some examples, each photonics die position can be associated with light with one or more unique wavelengths or unique wavelength ranges. 
     In some examples, the mirror  226  can be a microelectromechanical (MEMS) mirror. The MEMS mirror may adjust the angle of light reflected from the mirror  226 . For example, the MEMS mirror can be controlled by a controller (not shown in  FIG.  3 A ) such that the light provided by the mirror  226  may be incident on, or pass through, a specific region of the aperture structure  228 . The mirror may receive one or more control signals from the controller and may adjust its position based on the control signal(s). In some examples, the mirror  226  may be used to time sequentially combine or multiplex individual light outputs from the corresponding photonics die so that all the light is directed to and entering the sample at approximately the same angle and position. 
     The structure  300  may also include an optical element  212 . In some examples, the optical element  212  may be located in the stack  211 . When located in the stack, the optical element may have one or more functions that are different from the photonics dies  210  in the stack. In some examples, the optical element  212  may be a detector. The detector may receive and detect light from each photonics die in the stack  211 . The detector may be used for wavelength locking or reference measurements of the photonics dies in the stack  211 . 
     For example, the photonics dies  210  can be configured to emit light, whereas the optical element  212  can be configured to route one or more optical signals from the photonics dies  210  included in the stack  211 . The optical element  212  can include one or more connections (electrical, optical, or both) to one or more photonics dies  210 . For example, optical signals can be routed from photonics die  210 A through the optical element  212  to another photonics die  210 B. The optical element  212  may also route signals to an off-chip die (not shown in  FIG.  3 A ). In some examples, the off-chip die may be an off-chip detector which may be used for wavelength locking. 
     The broad wavelength range of light of the stack  211  may be separated into narrow wavelength ranges that are emitted by each photonics die in the stack  211 , thus each photonics die may be unique and optimized for its respective narrow wavelength range. Examples of these unique factors of a photonics die  210  can include properties relating to antireflection coatings, narrow band passive photonics components (e.g., splitters, combiners/multiplexers, polarizers, and so forth), and process operations related to III-V integrations that are unique for particular material systems such as InP or GaSb, for example. In some examples, the photonics die  210 A and/or the components of the photonics die  210 A can be fabricated on different substrate types such as silicon, a III-V material like GaAs, ceramic, or any other appropriate substrate that may serve the purpose of mechanical, electrical, and optical support and/or routing. The different substrate types can be designed or selected to enhance certain performance characteristics such as wavelength of the respective photonics dies  210 . 
     In some examples, a first photonics die  210 A can be configured to measure one type of signal, and the second photonics die  210 B can be configured to measure another type of signal. Additionally or alternatively, the photonics die  210 C can be configured for calibration functions, such as wavelength monitoring. In this manner, the structure  300  can be a modular system, where the inclusion (or exclusion) of a given photonics die  210  can change the overall functionality of the device. 
     In some examples, at least one of the photonics dies  210  can have the same or redundant wavelength properties or optical functionality as another photonics die  210 . Operating the system in this manner may be referred to herein as a “redundant mode”. For example, two photonics dies  210 A and  210 B may emit light at the same wavelength or have the same wavelength range. By doing this, the system may have a redundant capability and employ either photonics die  210 A or photonics die  210 B to take a measurement at the first wavelength or in the first wavelength range. Thus, one or more components on photonics die  210 A may not be concurrently operated with one or more components on photonics die  210 B. 
     The system may also have the capability to increase the output power by using multiple photonics dies simultaneously. Operating the system in this manner may be referred to herein as a “power mode”. The concurrent operation of both photonics dies may increase the output power of the emitted light at a given wavelength or in a given wavelength range. In some examples, more than two photonics dies may be operated concurrently. Concurrent operation can include starting the operation of the photonics dies at the same time, ending the operation of the photonics dies at the same time, or both. 
     In some examples, two or more photonics dies may be operated in a redundant mode and two or more other photonics dies may be operated in a power mode. For example, both of photonics die  210 A and photonics die  210 B can be configured in the redundant mode for first wavelengths or first wavelength ranges, and both of photonics die  210 C and photonics die  210 D can be configured in a power mode for second wavelengths or second wavelength ranges. 
       FIG.  3 B  illustrates a cross-sectional view of a partial photonics assembly. The cross-sectional view of  FIG.  3 B  is the same as that of  FIG.  3 A . The structure  305  of  FIG.  3 B  is similar to the structure  300  of  FIG.  3 A , except the structure  305  of  FIG.  3 B  includes a single light combining and directing optical element  225 . The structure  305  can include multiple photonics dies  210 , a stack  211 , an optical element  212 , a mirror  226 , and an aperture structure  228  that may be similar to the components described with respect to the structure of  FIG.  3 A . Here, however, the structure may also include a light combining and directing optical element  225  to combine, collimate, and direct or steer light. The light combining and directing optical element  225  may be configured to receive light  109  from the stack  211 . The received light may be combined, collimated, and/or directed or steered to provide light  113  to the mirror  226 . 
       FIG.  3 C  illustrates a cross-sectional view of a partial photonics assembly. The cross-sectional view of  FIG.  3 C  is the same as that of  FIGS.  3 A and  3 B . Structure  310  is generally similar to, and may include components that are the same as, structure  300  and/or structure  305  of  FIGS.  3 A and  3 B , respectively. However, structure  310  may not include a mirror  226 . Additionally, in some examples of  FIG.  3 C , the light combining optical element  222  can include multiple lenses which will be discussed in further detail in  FIGS.  4 A and  4 B . 
     As illustrated in  FIG.  3 C , the structure  310  may have a light emitting edge (e.g., as illustrated in  FIG.  2 A  as third edge  215 C) which may direct light to the aperture structure  228  without the use of the mirror  226 . The stack  211  may provide light  109  to the light combining optical element  222 , which may in turn provide light  111 A to the light directing optical element  224 . The light directing optical element  224  may direct light to one or more regions, such as transparent region  228 A of the aperture structure  228 . 
     In other examples, the structure  310  may omit the aperture structure  228 . For example, light may be launched directly into the sample after passing through light combining optical element  222  and light directing optical element  224  and without passing through region  228 A of the aperture structure  228 . In this way, the light may launch into the sample without multiplexing the light. 
       FIG.  4 A  illustrates a side view of a light combining optical element. In some examples, the light combining optical element  222  may include an array of fast-axis collimating lenses. In some examples, the collimating lenses can take the form of a cylindrical microlens array having multiple microlenses such as microlens  422 A, microlens  422 B, microlens  422 C, and so forth. The terms “light combining optical element,” “microlens array,” and “microlenses” may be used interchangeably herein. 
     The light combining optical element  222  can receive light  109  emitted by one or more photonics dies of a stack; such dies and stacks were discussed with respect to previous figures. The light combining optical element  222  may then pass light  111  to the light directing optical element  224  shown in  FIG.  3 C . 
     In some examples, each microlens  422  of the light combining optical element  222  can be configured to receive light from a respective photonics die. That is, a first photonics die may emit light  109 A which may be received by microlens  422 A, a second photonics die may emit light  109 B which may be received by microlens  422 B, and so on. In some instances, the light combining optical element  222  may be adjustable and may move such that the light combining optical element  222  may be aligned so that each microlens  422  may receive light from a corresponding photonics die  210 . In some examples, the individual microlenses  222 , may not be attached to one another by a common substrate (not illustrated in  FIG.  4 A ). In this example, each individual microlens  422  can be individually aligned to the light emitted from its respective photonics die  210 . 
       FIG.  4 B  illustrates a side view of a light combining optical element  222  coupled to an actuator  223 . The light combining optical element  222  may be the same as, or similar to, the one described with respect to  FIG.  4 A . The actuator  223  can receive one or more control signals and move the microlenses  422  in response to such signals. In some examples, the actuator  223  may be a voice coil motor, a piezo-based motor, a shape memory alloy actuator, electrostatic MEMs, magnetic actuators, any combination thereof, and so forth. In some instances, the actuator  223  can move the microlenses  422  such that a specific microlens can be aligned with a targeted photonics die  210 . For example, the targeted photonics die may emit light  109 A. The actuator  223  can be configured to move the microlens  422  such that the maximum curvature point of microlens  422 A can be aligned with the photonics die that emits light  109 A. As another example, the targeted photonics die may, e.g., at a second time, be the photonics die that emits light  109 B; and the actuator  223  can be configured to move the microlens  422 B such that the maximum curvature point of microlens  422 B can be aligned with the emitted light  109 B. This type of adjustment may be used when the pitch of the microlenses does not align with the emitted light of the photonics dies. 
     Although  FIG.  4 B  illustrates the actuator  223  as coupled to the bottom of the microlens array  422 , in some examples the actuator  223  may be coupled to one or more sides of the microlenses  422  for moving it one or more directions, such as parallel or perpendicular to the stack of photonics dies or to adjust the distance between the microlenses  422  and the stack of photonics dies. As another example, the actuator  223  can be configured to move in one or more directions to act, along with the light combining optical element  222 , the light directing optical element  224 , or both, as a moving diffuser for mitigating noise. 
       FIGS.  5 A- 5 F  illustrate a side view of components of a photonics die during various processing operations that result in the construction of a photonics die. Generally there are three implementations of integrating light emitters with the epitaxial element to provide a photonics die. The light emitter may be bonded and integrated into a silicon photonics system where the light emits through the silicon photonics system (such as propagating through a waveguide in the silicon photonics system) as discussed with reference to  FIG.  6   . Additionally, the light emitter may be bonded to a dummy substrate such as silicon or ceramic or any appropriate substrate as described with reference to  FIGS.  5 A- 5 F , where the substrate provides electrical connections and mechanical and thermal advantages, but the light emitter emits light directly into free space. Further, the light emitter may use III-V material only with no substrate, where the III-V material is arranged as a stack without using any other substrates as described in  FIGS.  11 - 13   . 
     As illustrated in  FIG.  5 A , a light emitting element  107  may be bonded on a substrate  213 . The light emitting element  107  can be bonded on top of the substrate  213  such that the top of the light emitting element  107  protrudes from the substrate  213 . Alternatively, a substrate cavity may be formed and the light emitting element  107  can be integrated into the substrate cavity such that the top of the light emitting element  107  does not protrude above the substrate  213 , as illustrated in  FIG.  5 B . In some examples, the light emitting element  107  may be integrated into the substrate cavity so that the top of the light emitting element  107  partially protrudes above the substrate  213 . In some examples and as previously discussed, the substrate  213  may be a silicon substrate or a silicon photonics system or the light emitting element may be a III-V material. In other examples, the photonics die may be a III-V material only which will be discussed here in  FIGS.  11 - 13   . 
     In  FIG.  5 B , a cavity can be formed in the substrate  213 , and the light emitting element  107  can be recessed into the substrate  213  by being bonded in the cavity. In some examples, the light emitter  107  may be formed separately from the substrate  213  and then bonded thereto. For example, the light emitters  107  may be tested and selected based on their performance prior to being bonded to the substrate  213 . In this manner, a given photonics die  210  may have pre-screened light emitters  107 , which can lead to increased yields. 
       FIG.  5 C  illustrates that an overmold  509  may be formed or deposited around the light emitting element  107  of  FIG.  5 A  (or on top of the light emitting element  107  in the case of  FIG.  5 B ), such that the top of the light emitting element  107  may be approximately coplanar with the top of the overmold  509 , as shown in  FIG.  5 C . As another option, a portion of the substrate  213  may be cut, etched, machined away, or otherwise removed and the overmold material deposited on the remainder of the substrate; this may be done to the example photonics die illustrated in  FIG.  5 B , for example. 
     In some examples, the overmold  509  can be additionally formed on top of the light emitter  107 , such as shown in  FIG.  5 D . This is an optional processing operation and may be omitted in many embodiments. 
       FIG.  5 E  illustrates one way to reduce the thickness of a photonics die  210 . Part of the substrate  213  may be removed from the back (e.g., from the side of the substrate opposite the one bonded to the light emitter  107 ) by using an etch process. In some instances, an etch stop layer  513  may be adjacent to the substrate  213  to prevent the etching process from over etching the substrate  213 . 
     In some examples, multiple sides of the substrate  213  may have light emitters  107 A,  107 B mounted thereto, as depicted in  FIG.  5 F . For example, the substrate  213  can include light emitter  107 A located on a first side of the substrate  213  and light emitter  107 B located on a second side of the substrate  213 . In some examples, light emitter  107 A can be configured to emit light having a first wavelength or set of wavelengths, while light emitter  107 B can be configured to emit light having a second wavelength or set of wavelengths. Additionally, the structure of  FIG.  5 F  may enable a photonics die  210  to emit light  109  along multiple planes. 
       FIG.  6    illustrates a light emitter layout on an epitaxial element of the photonics die. As illustrated in  FIG.  6   , epitaxial element  275  may include multiple light emitters  107 , where the light emitters  107  are bonded into a silicon photonics system. As described below, the light emitters  107  may emit light into the silicon or the waveguides of the silicon photonics system. In some examples, there may be one or more epitaxial elements  275  disposed on a photonics die as appropriate. The light emitters  107  of  FIG.  6    may emit light out of an edge of the stack that is adjacent to the offset direction of the photonics dies. The epitaxial element  275  may include electrical connections  232  (e.g., bonded connections) and optical paths  234  along with corresponding routing traces from the electrical connections  232  and the optical paths  234  to the light emitters  107 . In some examples, the light paths  111  may be split off from a primary waveguide. In some examples, the light may be split off individually, in which case each light emitter  107  may have an individual pathway, the light may be tapped or split off of the optical combining element  621 . Additionally in some examples, there may be laterally-spaced exit locations  619 . In some examples, the optical combining element  621  may have multiple outputs or may also include a splitter located after the optical combining element  621 . 
     Continuing the discussion of  FIG.  6   , the optical combining element  621  can receive light  108  emitted by the light emitters  107 . In some examples, the optical combining element  621  may be a passive element and may combine the light into a waveguide. In some examples, the optical combining element may be an active element, such as an optical switch, which may switch between the light emitted by the light emitters or an optical multiplexer. The output from the optical combining element  621  can be light  109 , which can exit the photonics die at location  619 . In some examples, the epitaxial element  275  may combine light  108  emitted by the light emitters  107  to a waveguide. Although  FIG.  6    depicts the light from each of the light emitters being combined by a light combining element  621  and emitted as combined light, in some examples each light emitter on the photonics die may include a corresponding waveguide extending to the edge of the photonics die so that light from each emitter may be emitted in separate beams. In some examples, the light emitted by the light emitters may be combined or multiplexed into a subset of outputs and the light may be emitted in those subsets. In some examples, the subsets may include the same group of repeating wavelengths and in some examples, the subsets may include groups of unique wavelengths. Additionally, although  FIG.  6    depicts the light as being launched from a single output, light beams with different wavelengths or wavelength ranges may not be coincident on each other and may be separated by, for example, approximately 250 microns. 
       FIG.  7 A  illustrates a layout of sample epitaxial elements on a photonics die. In  FIG.  7 A , the photonics die  210  may include multiple epitaxial elements  275  and electrical connections  232 . Each epitaxial element  275  may include one or more light emitting elements  107  as described with reference to  FIG.  6   . The light emitting elements  107  may or may not be visible from the top view of the photonics die  210  in  FIG.  7 A . In some examples, each epitaxial element may include eight light emitting elements, thus in the example of  FIG.  7 A , the photonics die  210  may include 40 light emitting elements on the five epitaxial elements  275 . The light emitting elements included on an epitaxial element  275  may all emit the same wavelength of light or each light emitting element may emit a different wavelength of light from the other light emitting elements so that the photonics die  210  may emit a wavelength range of light. It should be appreciated that the layout shown is one example and other layouts are possible. Likewise, the number, size, and position of various elements, including light emitting elements  107 , electrical connections  232 , and epitaxial elements  275 , may vary between embodiments. 
     In some examples, the wavelength range of light emitted by multiple photonics dies  210  may be a broadband wavelength range and may use any number of lasers, such as 120 lasers. In some examples, the number of lasers may be greater or fewer than 120 lasers. In some examples, fifteen epitaxial elements  275  may be distributed over three photonics dies, so that each photonics die includes five epitaxial elements  275  as shown in  FIG.  7 A , and each epitaxial element may include eight light emitting elements. Although specific numbers of epitaxial elements, lasers, and wavelength ranges are discussed, the number of epitaxial elements, light emitting elements, photonics dies, lasers, and wavelength ranges may vary as appropriate. Further, each of the epitaxial elements  275  may emit light over an approximate wavelength range of 0.07 μm. 
     In other examples, eight lasers per epitaxial element  275  may be used and fifteen epitaxial elements  275  may be included on the photonics die  210 . Again, each of the epitaxial elements  275  may then emit light over an approximate wavelength range of 0.066 μm. Although specific numbers of photonics dies, lasers, epitaxial elements, and wavelength ranges are discussed, this is for explanatory purposes and these numbers may vary as appropriate. 
       FIG.  7 B  illustrates another example photonics die stack and a light combining element. The photonics die stack  211  includes photonics dies  210 A,  210 B, and  210 C and photonics die  210 A includes epitaxial elements  275 A and  275 B. As shown in  FIG.  7 B , the stack  211  includes offset photonics dies  210  that emit light  111  through the light combining element  222 . As shown in  FIG.  7 B , the epitaxial elements may vertically align with one another and the corresponding substrates may be different sizes to accommodate the electrical connections  232 . In the example of  FIG.  7 B , the light may be emitted approximately parallel to the plane of the corresponding photonics die. 
       FIG.  7 C  illustrates still another example photonics die stack. The photonics die stack  700  includes photonics dies  210  and an optical element  212  and each of the photonics dies may emit light  111 . It may be understood that the emitted light  111  may emit from the edge of the photonics dies  210 . The photonics die stack  700  includes three photonics dies  210 A,  210 B, and  210 C in an offset stack. Each of the photonics dies  210  includes five epitaxial elements  275  bonded to a substrate. Each of the epitaxial elements  275  may include eight light emitting elements (light emitting elements not illustrated in  FIG.  7 C ) for a total of 120 light emitting elements. In some examples, the light emitting element may be lasers, diodes, or any appropriate light source including but not limited to coherent light sources, semi-coherent light sources, and so forth. 
       FIG.  7 D  illustrates yet another example photonics die stack and is similar to  FIG.  7 C , but from an alternative point of view. Similar to  FIG.  7 C ,  FIG.  7 D  illustrates a photonics die stack  700  that includes photonics dies  210  and an optical element  212 , where each of the photonics dies may emit light  111 . Similar to  FIG.  7 C , the emitted light  111  may be emitted from the edge of the photonics dies  210 . As previously discussed, each of the photonics dies  210  includes five epitaxial elements  275  bonded to a corresponding substrate. As shown in  FIG.  7 D , the substrates may be different sizes to accommodate the electrical connections  232  and the edges of the photonics die stack  700  may not vertically align with one another on three sides of the photonics die stack. In  FIG.  7 D , the optical element  212  may abut the photonics dies  210  on the fourth side where the edges of the photonics dies may align so that the photonics dies may abut or be adjacent to the optical element  212 . As used herein, the term “abutting” means that two elements share a common boundary or otherwise contact one another, while the term “adjacent” means that two elements are near one another and may (or may not) contact one another. Thus, elements that are abutting are also adjacent, although the reverse is not necessarily true. Two elements that are “coupled to” one another may be permanently or removably physically coupled to one another and/or operationally or functionally coupled to one another. Additionally, the optical element  212  may be used in conjunction with the light combining optical element  222 . 
       FIG.  8    illustrates a package with photonics dies. In some examples, the stack can be configured such that the exposed surface of the phonics die located at the at least one edge of the photonics die  210  may be used for multiple purposes, such as emitting light and for electrical connections. As illustrated in  FIG.  8   , multiple photonics dies may be arranged to create an offset vertical stack configuration and the stack can include a first stack edge  815 A. The first stack edge  815 A can include one or more first sections  817 A and one or more second sections  817 B. The first section  817 A may define a region where light  109  may be emitted from a respective photonics die  210 . The second sections  817 B generally are positioned to the sides of the first section and can include or define electrical connections  232  between adjacent photonics dies. 
     Operation of a Photonics Assembly 
       FIG.  9    is a flowchart of a process for operating a photonics assembly using a linear scan. In some examples, the linear scan of  FIG.  9    can include operating the photonics dies in serial. For example, a first photonics die can be operated at a first time; a second photonics die can be operated at a second time; and so forth. The first time may be separate from and non-overlapping with the second time. 
     Process  900  can begin at operation  952  with a controller (as illustrated in  FIG.  1   ) transmitting one or more control signals to one or more light emitters located on the targeted photonics die. The targeted photonics die may refer to the photonics die of interest at a given time. The targeted photonics die may be selected based on any number of functions such as the range of emitted wavelengths or because the photonics die is the next photonics die in the scanning operation of the photonics assembly. For example, in a linear scan, the targeted photonics die may initially be the first photonics die  210 A, then the targeted photonics die may change to the second photonics die  210 B, followed by the targeted photonics die switching to the third photonics die  210 C, and so forth. The control signals can be transmitted from the controller to the light emitters using the routing traces of the optical element  212  and the electrical connections and optical paths located on the respective photonics die  210 . 
     At operation  954 , the light emitters on the targeted photonics die may emit light  109 A at a first time, second light  109 B at a second time, and so forth. The light combining optical element  222  may receive the respective light and at operation  956  may combine and/or collimate the light emitted by the light emitters on the targeted photonics die. At operation  958 , the light directing optical element  224  may receive the light from the light combining optical element  222  and may redirect the light to the mirror  226 . 
     At  960 , the mirror  226  may receive the light and a controller may be coupled to the mirror and can control the position of the mirror for redirecting the light as indicated at operation  962 . Also at operation  962 , the position of the mirror may be such that it redirects light to pass through the transparent region  228 A of the aperture structure  228  at operation  964 . In some examples, the angle of the mirror may depend on which photonics die  210  is emitting light, the wavelength(s) of the emitted light, or both. For example, the photonics die  210 A can be at the top of the stack and can be associated with a first position of the mirror. The photonics die  210 B may be positioned beneath the photonics die  210 A and can be associated with a second position of the mirror. Different photonics dies  210  may be associated with different positions of the mirror due to the different positions of the photonics dies  210  within the stack  211 . As another example, a first position of the mirror can be associated with a first wavelength or first wavelength range, and a second position of the mirror can be associated with a second wavelength or second wavelength range. 
     As indicated in operations  966  and  968 , operations  952 - 964  may be repeated in a cycle until all of the photonics dies with light emitters have become the targeted photonics. When a targeted photonics die  210  changes to a different photonics die  210 , the position of the mirror may be changed accordingly. In some examples, the position of the mirror may be related to the position of the photonics dies within the stack. In some examples, the position of the mirror may be incrementally adjusted. At the end of a cycle and at operation  970 , a processor can analyze the signals. The cycle can be associated with a given sequence of photonics dies and the sequence of photonics dies can include the same order as the photonics dies within the stack  211 , or may include a different order. In some examples, the sequence may include only some of the photonics dies in the stack  211 . 
       FIG.  10    is a flowchart of a process for operating a photonics assembly for monitoring purposes. In some examples, the process can be operated to monitor properties of the photonics assembly such as the emitted wavelength(s). The properties can be satisfied when the light emitter(s) of a given photonics die reaches a targeted stability point. Similar to process  900 , process  1000  can begin with operation  1052 , with a controller sending one or more control signals to one or more light emitters located on the targeted photonics die. The targeted photonics die may refer to the photonics die of interest at a given time. The targeted photonics dies may be selected based on any number of functions such as the range of emitted wavelengths or because the photonics die is the next photonics die in the scanning operation of the photonics assembly. For example, the targeted photonics die may initially be the first photonics die  210 A. After the emitted wavelength emitted by the first photonics die  210 A is monitored and confirmed, the targeted photonics die may change to the second photonics die  210 B, and so forth. The control signals may be similarly transmitted as discussed with respect to  FIG.  9   . 
     At operation  1054 , the mirror  226  can be positioned such that light from the light source(s) do not pass through the transparent region  228 A of the aperture structure  228 . At operation  1056 , the light emitters on the targeted photonics die may emit light  109 A at a first emitting time, and may emit light  109 B at a second emitting time, and so forth. At operation  1058 , one or more detectors can measure the properties of the emitted light. In some examples, the detector(s) can be located on a photonics die  210  of the stack  211  and can receive the optical signals from the light emitters using the optical element  212 , as discussed herein. 
     At operation  1060 , a controller can be used to determine whether the properties of the emitted light such as wavelength or power, as measured by the detector(s), meet one or more criteria. The criteria may be a stability point or a stability range for the emitted light of the light sources or the criteria may be based on a predetermined specification, for example. The predetermined specification may be a target wavelength range or may be a target optical power. If the emitted light has not met the criteria, then the process  1000  can wait for the emitted light to meet the criteria by repeating operations  1056  and  1058 . 
     If the emitted light meets the criteria, then at  1062  the mirror can be positioned such that light from the light source(s) passes through the transparent region of the aperture structure  228 . Operations  1052 - 1062  may be repeated in a cycle per operations  1064  and  1066  until all of the photonics dies which emit light have been the targeted photonics dies. Once a different photonics die is the targeted photonics die  210 , the position of the mirror may be changed accordingly, as discussed herein. At operation  1070 , the end of a cycle, a processor can analyze the signals. 
     Although  FIGS.  9  and  10    illustrate an overview of operations of the photonics assembly, further examples can include additional steps, sub-steps, operations, sub-operations, processes, and sub-processes such as those discussed herein in the context of the other figures. 
     Photonics Die with III-V Materials Only 
       FIGS.  11 A- 11 H  illustrate both cross-sectional and top views of a photonics die with III-V materials instead of both III-V and silicon materials. For example, the substrate  213  may not be silicon as previously discussed in  FIG.  5   , but instead is a III-V substrate. In some instances, the light emitters included in the photonics die may be distributed feedback lasers (DFBs) which may have gratings formed with III-V materials such as a III-V substrate. These DFBs will be discussed herein with respect to  FIGS.  11 A- 13   . As shown in  FIGS.  11 A- 11 H , the substrate  1115  is indicated with a cross-hatching pattern which may indicate the substrate  1115  in each of these figures. 
       FIG.  12    is a flowchart of a process flow for fabricating a photonics die with III-V materials, and may include operations that correspond to  FIGS.  11 A- 11 H . Accordingly, the operations of  FIG.  12    are discussed with reference to the corresponding ones of  FIGS.  11 A- 11 H . 
     As illustrated in the process  1250  of  FIG.  12   , in operation  1252 , a III-V wafer can be provided as a substrate  1115  as illustrated in  FIG.  11 A .  FIG.  11 A  shows both cross-sectional and top views of the substrate  1115 . At operation  1254  and as illustrated in  FIG.  11 A , laser ridges  1110  can be formed by patterning the substrate  1115 . At operation  1256 , metal  1112  can be deposited on top of the substrate  1115  and laser ridges  1110 , as shown in the top view of  FIG.  11 B . Part of the deposited metal may be removed from each of the laser ridges  1110  and the surface of the substrate  1115  as illustrated in the top view of  FIG.  11 B . At operation  1258  and as illustrated in  FIG.  11 C , pads  1114  can be deposited on top of the metal  1112 . 
     In operation  1260  and as shown in the side view of  FIG.  11 D , an overmold  1116  can be deposited on the metal  1112 . In operation  1262  and as shown in the top view of  FIG.  11 E  a grinding operation can expose the pads  1114 . As shown in  FIG.  11 F  and in operation  1264 , a redistribution layer  1118  can be deposited on the overmold  1116 . Following the deposition of the redistribution layer  1118 , at operation  1266  and as shown in  FIG.  11 G , portions of the substrate  1115  can be optionally removed in order to thin the resulting photonics die and metal traces may be added to connect the pads  1114  to a second set of pads on the left side of the substrate  1115 . 
     In operation  1268  and as shown in  FIG.  11 H , a film  1120 , such as a die attach film, can be deposited on the redistribution layer  1118 . At operation  1270 , chips can be diced (e.g., singulated), and the process can proceed with operation  1272  of integrating with other photonics dies. The integration with other photonics dies can include stacking photonics die  210 A on top of photonics die  210 B, as shown in the top view of  FIG.  11 I . The integration may also include forming electrical connections  232 , as shown in the top and cross-sectional views of  FIG.  11 J . In some examples, laser drilling may be followed by a metal fill to create the pads  1114 . 
     As previously discussed with respect to  FIG.  6   , a stripe of light may be formed due to the varying positions of the photonics dies  210  and/or the varying positions of the one or more light emitters within each photonics die  210 . When using DFBs only, the stripe may be created per each photonics die. In some examples, the photonics die may include a first grating which may be tuned to a first wavelength, a second grating which may be tuned to a second wavelength, a third grating which may be tuned to a third wavelength, and so forth. These gratings may be located such that the light may be launched directly out of the photonics die and/or via a waveguide, thus creating a stripe of light. In some examples, the stripe may be created by repeating the DFB structure as the DFBs may be made of the same material. 
       FIG.  13    is a flowchart of a process flow for fabricating a photonics die with III-V materials. Process  1350  can include operations  1352 ,  1354 ,  1356 ,  1364 ,  1366 ,  1368 ,  1370 , and  1372  that may be correspondingly similar to operations  1252 ,  1254 ,  1256 ,  1264 ,  1266 ,  1268 ,  1270 , and  1272  of process  1250  of  FIG.  12   . Process  1350  may also include operation  1360  for depositing an overmold. Operation  1360  may be similar to operation  1260 , but the overmold may be deposited before the pads are grown. In some examples, the grinding operation (e.g., operation  1262  of  FIG.  11   ) may be omitted. 
     Following operation  1360 , at operation  1361  holes may be drilled in the overmold, and at operation  1363 , the holes may be filled with metal. Process  1350  may proceed with operations  1364 ,  1366 ,  1368 ,  1370 , and  1372  as discussed herein. 
     The foregoing description, for purposes of explanation, uses specific nomenclature to provide a thorough understanding of the described embodiments. However, it will be apparent to one skilled in the art, after reading this description, that the specific details are not required in order to practice the described embodiments. Thus, the foregoing descriptions of the specific embodiments described herein are presented for purposes of illustration and description. They are not targeted to be exhaustive or to limit the embodiments to the precise forms disclosed. It will be apparent to one of ordinary skill in the art, after reading this description, that many modifications and variations are possible in view of the above teachings. 
     Although the disclosed examples have been fully described with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art. Such changes and modifications are to be understood as being included within the scope of the disclosed examples as defined by the appended claims.

Metadata:
Filing Date: 20200909
Publication Date: 20240123
Grant Date: 20240123
Priority Date: 20190909
Inventors: BISHOP, MICHAEL J.
LAI, Kwan-Yu
GOLDIS, ALEX
BISMUTO, ALFREDO
HILL, JEFFREY THOMAS
Assignee: APPLE INC
CPC Classifications: [{"code": "H01S5/4025", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01S5/023", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01S5/4087", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01S5/4075", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01S5/405", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01S5/0071", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B3/06", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B26/0833", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B26/105", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01S5/4043", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01S5/4087", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01S5/0071", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01S5/4043", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B3/06", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B26/0833", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B26/105", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01S5/4087", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B26/0833", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B3/06", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B26/105", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/12002", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B2006/12107", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B2006/12178", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/4206", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B2006/12121", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 89578479