Bottom-emitting vertical cavity surface emitting laser array with integrated directed beam diffuser

A bottom-emitting vertical-cavity surface-emitting laser (VCSEL) chip may include a VCSEL array including plurality of VCSELs and an integrated optical element including a plurality of lens segments. The integrated optical element may direct beams provided by the plurality of VCSELs to a particular range of angles to create a diffusion pattern using the beams provided by the plurality of VCSELs. A surface of a first lens segment may be sloped to cause a beam from a first VCSEL to be steered at a first angle and a surface of a second (adjacent) lens segment may be sloped to cause a beam from a second VCSEL to be steered at a second angle. A direction of the second angle with respect to a surface of the VCSEL array may be opposite to a direction of the first angle with respect to the surface of the VCSEL array.

TECHNICAL FIELD

The present disclosure relates generally to a vertical-cavity surface-emitting laser (VCSEL) array and to a bottom-emitting VCSEL array with an integrated directed beam diffuser.

BACKGROUND

A VCSEL array can be used to illuminate a scene for use in, for example, a three-dimensional (3D) sensing application. Conventionally, the VCSEL array is paired with a diffuser that is external to the VCSEL array. The diffuser may act to spread light provided by emitters of the VCSEL over a field-of-view (FOV) also sometimes referred to as the field of illumination (FOI). In the conventional arrangement of an external diffuser and a VCSEL array, the diffuser spreads light from a given VCSEL over the entire FOV. Put another way, a diffuser response does not vary from emitter-to-emitter across the VCSEL array.

SUMMARY

In some implementations, a bottom-emitting VCSEL chip includes a VCSEL array including plurality of VCSELs; and an integrated optical element including a plurality of lens segments, wherein the integrated optical element is to direct beams provided by the plurality of VCSELs to a particular range of angles to create a diffusion pattern using the beams provided by the plurality of VCSELs, wherein a surface of a first lens segment of the plurality of lens segments is sloped to cause a beam from a first VCSEL of the plurality of VCSELs to be steered at a first angle, wherein a surface of a second lens segment of the plurality of lens segments is sloped to cause a beam from a second VCSEL of the plurality of VCSELs to be steered at a second angle, wherein the second lens segment is adjacent to the first lens segment, and wherein a direction of the second angle with respect to a surface of the VCSEL array is opposite to a direction of the first angle with respect to the surface of the VCSEL array, and wherein a beam from a VCSEL of the plurality of VCSELs is to pass through only one lens segment of the plurality of lens segments.

In some implementations, an optical device includes a VCSEL array including plurality of VCSELs; and an integrated optical element including a plurality of lens segments, wherein the integrated optical element is to direct beams provided by the plurality of VCSELs to a particular range of angles to create a diffusion pattern using the beams provided by the plurality of VCSELs, wherein a lens segment of the plurality of lens segments is to steer a beam from a VCSEL of the plurality of VCSELs at a respective particular angle in association with creating the diffusion pattern, and wherein surfaces of two adjacent lens segments of the plurality of lens segments are sloped to cause beams from two respective VCSELs of the plurality of VCSELs to be steered at angles having opposite directions with respect to a surface of the VCSEL array.

In some implementations, an optical device includes a VCSEL array including plurality of VCSELs; and an integrated optical element including a plurality of lens segments, wherein the integrated optical element is to direct beams provided by the plurality of VCSELs to a particular range of angles to create a diffusion pattern using the beams provided by the plurality of VCSELs, wherein light from a VCSEL of the plurality of VCSELs is present in a portion of the diffusion pattern that is less than an entirety of the diffusion pattern, and wherein surfaces of lens segments of the plurality of lens segments are sloped in alternating directions to cause beams from two or more respective VCSELs of the plurality of VCSELs to be steered at alternating angles with respect to a surface of the VCSEL array.

DETAILED DESCRIPTION

A conventional diffuser is a discrete component arranged at a particular distance from a light source (e.g., a VCSEL) and acts to spread light from the light source over an entire FOV, as described above. Such arrangement and functionality may be beneficial when the light source is single-mode or few-mode such that interference spots are present (also referred to as as speckle). However, some emitters, such as VCSELs, may have lateral modes that change on a picosecond (or shorter) timescale, which significantly reduces speckle, meaning that a broad diffusion of light from a given VCSEL in a VCSEL array is not needed to obtain a sufficiently smooth pattern.

Further, a diffuser can be diffractive or refractive. Both of these types of diffusers suffer as a divergence of a VCSEL increases, which can result in an FOV efficiency of only approximately 70% to 80%. In addition to the FOV efficiency, light may be reflected by an incoming surface (e.g., a polymer surface) of the diffuser or by an exiting surface (e.g., a glass surface) of the diffuser, neither of which are typically anti-reflection (AR) coated (due to the difficulty of depositing an AR coating and keeping the AR coating in place). Without these AR coatings, efficiency is further reduced (e.g., by up to approximately another 8%). Furthermore, the diffuser needs micrometer or sub-micrometer scale features that are difficult or impossible to fabricate with photolithography, instead requiring an imprint from a mold. A mold can be significantly more expensive than a photomask and also does not lend itself to integration with VCSEL arrays that can change from product to product. Furthermore, for a diffractive diffuser, there is often excess unwanted light in a center of a diffusion pattern from a “zero-order” direction. For a refractive diffuser, there may not be a problem from zero-order diffraction, but there may be parasitic reflections at some angles, which reduces efficiency. This problem is worsened at an interface where light goes from a material with a high refractive index (e.g., a semiconductor material) to air. For these reasons, the use of a conventional discrete diffuser may be sub-optimal in an application that uses VCSELs as a light source.

Some implementations described herein provide a VCSEL chip having a bottom-emitting VCSEL array with an integrated optical element that acts as a directed beam diffuser (herein referred to as an integrated optical element). In some implementations, the integrated optical element includes a plurality of lens segments that, collectively, create a diffusion pattern from beams provided by VCSELs of a VCSEL array (e.g., such that an aggregate intensity versus angle from all of the VCSELs mimics an output of a conventional diffuser). In some implementations, the integrated optical element creates the diffusion pattern by directing beams provided by the VCSELs to a particular range of angles. In some implementations, a beam from a given VCSEL passes through only one lens segment of the integrated optical element. In some implementations, a lens segment steers the beam from the given VCSEL at a particular angle in association with creating the diffusion pattern. In some implementations, light from the given VCSEL is present in only a portion of the diffusion pattern. That is, the light from the given VCSEL is not spread over the entire diffusion pattern (as in the case of a conventional diffuser).

As described in further detail below, the VCSEL array with the integrated optical element overcomes the above-described drawbacks of the conventional diffuser. In this way, functionality of a discrete diffuser and VCSEL array can be combined in one compact chip while also improving efficiency of the optical system. Further, a chip having the VCSEL array with the integrated optical element enables independent illumination of different regions, which may be advantageous for some optical systems, such as an indirect time-of-flight system that needs high power to illuminate objects at greater distances.

FIG.1is a diagram of an example optical device100comprising an emitter array102and an integrated optical element106. Optical device100may be, for example, a bottom-emitting VCSEL chip.

Emitter array102is an emitter array to provide light (e.g., beams110) from which a diffusion pattern is to be created by integrated optical element106. For example, as shown inFIG.1, emitter array102may include a plurality of emitters104, each of which is to provide a respective beam110. In some implementations, emitter array102is a planar array having oxide trenches defining the plurality of emitters104. In some implementations, emitter array102is a bottom-emitting VCSEL array comprising a plurality of bottom-emitting VCSELs (i.e., emitters104of emitter array102may emit light through a substrate-side of emitter array102). In some implementations, emitter array102is a one-dimensional (1D) array of emitters104. In some implementations, emitter array102is a two-dimensional (2D) array of emitters104. In some implementations, emitter array102includes at least approximately 40 emitters104(e.g., emitter array102may include a few hundred emitters). In some implementations, the number of emitters104may be selected so as to enable a smooth intensity versus angle profile to be created (e.g., as compared to an array of distinct spots in the far-field). Notably, such a design also enables independent illumination of different portions of a FOV.

Integrated optical element106is a component to create a diffusion pattern from beams110provided by emitters104of emitter array102. As shown inFIG.1, integrated optical element106may include a plurality of lens segments108. In some implementations, integrated optical element106is integrated with emitter array102. That is, integrated optical element106is not a discrete or external diffuser. Rather, integrated optical element106is integrated in a chip with emitter array102. For example, the plurality of lens segments108may be patterned on a substrate (e.g., a gallium arsenide (GaAs) substrate) of emitter array102. In some implementations, the optical element106and emitter array102may be monolithically integrated into a wafer comprising a plurality of optical devices100. In some implementations, integrated optical element106may form the substrate. In some implementations, integrated optical element106may be formed in the substrate of the emitter array102. Thus, in some implementations, the lens segments108are formed on an exterior surface of the optical device100. In some implementations, optical element106may have an anti-reflection coating deposited on the top surface.

In some implementations, a slope of a given lens segment108of integrated optical element106(e.g., relative to a surface of emitter array102) can be selected so as to provide steering of a beam110at a particular angle. Thus, slopes of the lens segments108of integrated optical element106can be selected so as to cause integrated optical element106to create a desired diffusion pattern from beams110provided by emitters104of emitter array102.

In some implementations, a surface of a lens segment108of integrated optical element106may be planar (e.g., a surface having a linear slope). A lens segment108having a sloped planar surface may provide steering of beam110but may not reduce divergence of the beam110. In some implementations, a surface of a lens segment108of integrated optical element106may be curved (e.g., a surface may have a non-linear slope, as illustrated inFIG.1). In some implementations, curvature of a surface of lens segment108may act to reduce divergence of a beam110passing through the lens segment108, which may be beneficial at, for example, comparatively steeper angles (e.g., to improve sharpness of the intensity versus angle profile at the edge of the diffusion pattern where the beam may exit at 20 to 60 degrees from normal and the surface may be tilted nominally 7 to 14 degrees from horizontal). In some implementations, a radius of curvature of the given lens segment108may be in a range from approximately 180 micrometers (μm) to approximately 450 μm (e.g., to obtain reasonable tolerance to misalignment, which may be in the range of approximately ±1 μm to approximately ±5 μm). In some implementations, a slope of a surface of a lens segment108may be selected so as to steer a beam110passing through the lens segment108in a desired direction. In some implementations, a type of the surface (e.g., curved, planar) of a given lens segment108may be selected so as to selectively reduce divergence of a beam110passing through the given lens segment108. In some implementations, reducing the divergence of beams110that illuminate edges of the FOV may improve sharpness in edges of an aggregate profile of the diffusion pattern created by integrated optical element106. In some implementations, the lens segments108may each correspond to segments of a same reference lens or may each correspond to segments from a set of two or three reference lenses.

In some implementations, a pitch (e.g., a center-to-center distance) between a given pair of lens segments108is in a range from approximately 30 μm to approximately 60 μm and intended to match the pitch of the emitters. This pitch is much tighter compared to that for full (circular) lenses, which may be 100 μm to 200 μm. In some implementations, a size of a footprint of integrated optical element106matches or is smaller than a size of a footprint of emitter array102. That is, in some implementations, a footprint of integrated optical element106is not larger than a footprint of emitter array102.

As shown inFIG.1, in operation, emitters104of emitter array102emit beams110through integrated optical element106such that each beam110passes through a respective lens segment108. In some implementations, as illustrated inFIG.1, optical device100is designed such that each beam110passes through a different lens segment108of integrated optical element106(i.e., such that no two beams110pass through the same lens segment108). Alternatively, in some implementations, optical device100maybe designed such that two or more beams110pass through a given lens segment108of integrated optical element106.

In some implementations, the lens segments108of integrated optical element106direct the beams110to a particular range of angles to create a diffusion pattern using the beams110. To create the diffusion pattern, a given lens segment108steers a beam110from one or more emitters104at a particular angle (e.g., the particular angle depending on slope of a surface of the given lens segment108). For example, as shown inFIG.1, beams110provided by emitters104on a left side of emitter array102may be steered in generally leftward directions in association with generating the diffusion pattern. As shown inFIG.1, beams110provided by emitters104on a right side of emitter array102may be steered in generally rightward direction in association with generating the diffusion pattern. As shown inFIG.1, beams110provided by emitters104near a center of emitter array102may be steered in a generally straight direction in association with generating the diffusion pattern. As a result, as indicated inFIG.1, light from a given emitter104is present in only a portion of the diffusion pattern created by integrated optical element106(i.e., light from the given emitter is not present across the entire diffusion pattern).

Notably, as illustrated inFIG.1, a beam110from a given emitter104may pass through only one lens segment108. In some implementations, optical device100may designed such that a combined output beam of optical device100mimics that of a conventional diffuser. That is, in some implementations, the diffusion pattern created by integrated optical element106may mimic that of the conventional external diffuser described above. In some implementations, optical device100is designed such that an aggregate intensity versus angle of the diffusion pattern minimizes an appearance of spots from individual emitters104in the diffusion pattern (e.g., such that intensity varies with oscillation of less than approximately 20% between inner angles of the diffusion pattern and outer angles of the diffusion pattern). In some implementations, optical device100is designed to maximize power concentrated within the FOV. To increase the power within a particular FOV, the edges of the profile need to be sharp with respect to angle. The optical device100designed with smaller emitters (e.g., 4 μm to 16 μm aperture diameter) and an optimal radius of curvature (e.g., for GaAs substrates a radius of 150 μm to 380 μm, generally 1.4× to 2.5× the substrate thickness) will better narrow the divergence and when pointed at the edge of the FOV will result in a sharper, more efficient profile. The radius of curvature and individual divergence may need to increase for emitters pointed towards the center of the FOV in order to smooth out the profile. Thicker substrates (e.g., thicknesses greater than 400 μm) and larger radii of curvature further reduce divergence, but require emitters spread further apart, which increases chip cost and may result in dispersion of the far-field profile into spots rather than a continuous beam of light.

As indicated above,FIG.1is provided as an example. Other examples may differ from what is described with regard toFIG.1. Further, the number and arrangement of components shown inFIG.1are provided as an example. In practice, there may be additional components, fewer components, different components, or differently arranged components than those shown inFIG.1.

In some implementations, optical device100is designed such that the diffusion pattern has a higher intensity (e.g., approximately two to four times a center intensity) at relatively larger angles within a desired FOV (e.g., a FOV from approximately 50 to approximately 120 degrees) to achieve a so-called “bat-wing” profile.FIG.2is an illustrative example of a bat-wing profile that can be achieved by appropriate design of optical device100.FIG.2is provided as an example, and other examples may differ from what is described with regard toFIG.2.

FIG.3is a diagram illustrating a composite relative intensity versus angle (far-field) of an output of optical device100after integrated optical element106for all emitters104in an example emitter array102and a relative intensity versus angle after integrated optical element106for an individual emitter104of the example emitter array102. As indicated inFIG.3, in operation of optical device100, a beam110of the individual emitter104is steered in a particular direction (as dictated by an associated lens segment108). The other beams110emitted by other emitters104of emitter array102are similarly steered (at particular angles as dictated by their associated lens segments108) so that the composite relative intensity versus angle is created from the beams110provided by the emitters104. That is, a composite of intensity profiles associated with each emitter104of the example emitter array102would result in the composite relative intensity versus angle profile shown inFIG.3.

FIG.4is a diagram illustrating an example distribution of emitters104designed to steer beams110to various angles in association with creating the composite intensity versus angle shown inFIG.3. In the example shown inFIG.4, emitter array102has 19 emitters104, and lens segments108of integrated optical element106direct the beams110to specific angles as given by the distribution shown inFIG.4. In some implementations, as indicated inFIG.4, there is a comparatively lower number of emitters104aimed toward a center of emitter array102(e.g., angles with a smaller absolute value). However, the number of emitters104aimed toward the center of emitter array102may not be so low such that individual beams110appear in the far-field. In some implementations, as shown inFIG.4, the number of emitters104aimed to angles near edges of the FOV (e.g., angles with a higher absolute value) may be comparatively higher (e.g., to increase intensity near the edges of emitter array102in order to create the diffusion pattern having the bat-wing profile). As indicated above,FIGS.3and4are provided as examples. Other examples may differ from what is described with regards toFIGS.3and4.

Notably, the examples shown inFIGS.3and4are associated with a 1D emitter array102, but similar principles may be applied in the case of a 2D emitter array102.FIG.5is a diagram illustrating an example of a distribution of aiming directions of emitters104in a 2D emitter array102(e.g., an array of328emitters104is shown inFIG.5). In some implementations, as shown inFIG.5, the distribution of aiming directions may have a honeycomb-like pattern (e.g., rather than a square grid) in a center of the far-field (e.g., away from edges of the far-field). In some implementations, the honeycomb-like pattern permits even coverage with the circular far-fields of individual emitters104. Notably, the honeycomb-like pattern shown inFIG.5indicates the distribution of aiming directions of emitters104as provided by integrated optical element106and does not relate to a spatial distribution of emitters104. That is, the distribution shown inFIG.5does not represent a physical layout of emitters104of the emitter array102.

FIGS.6A-6Care diagrams illustrating distributions of intensity versus angle for the example emitter array102associated withFIG.5.FIG.6Aillustrates a 2D intensity versus angle from all emitters104of the 2D emitter array102. Notably, intensity is higher near edges of the intensity distribution (e.g., as indicated by the comparatively darker region).FIG.6Billustrates a 2D intensity versus angle for an individual emitter104of the 2D emitter array102(on the same scale asFIG.6A). Here, each emitter104of the example emitter array102would have a similar intensity but would be directed towards a different angle (e.g., a different location inFIGS.6A,6B). A composite of the intensities associated with all emitters104would result in the distribution shown inFIG.6A.FIG.6Cillustrates examples of 1D “slices” through the intensity versus angle distribution shown inFIG.6Aalong a first axis (the theta Y axis shown inFIG.5) at various values (e.g., 0 degrees, 16 degrees, and 25 degrees) along a second axis (the theta X axis shown inFIG.5). As shown byFIGS.6A-6C, the diffusion pattern created by integrated optical element106in the 2D implementation may have a bat-wing profile (e.g., at a given “slice” of the distribution).

One consideration for an integrated optical element106is an ability to function even when an emitter104has died. A “dead” emitter104may be, for example, an emitter104that has an amount of power that is less than a threshold, an emitter104that has no power, an emitter104that has significantly less power than an adjacent emitter104, and/or the like.FIG.7illustrates examples of 1D slices through the intensity versus angle shown inFIG.6Ain a case when an emitter104near a center of the example emitter array102is a dead emitter. Thus,FIG.7illustrates a tolerance of the optical device100to a dead emitter104being present in the emitter array102. As indicated inFIG.7, a dead emitter104near the center of the 2D emitter array102reduces intensity by only approximately 15%, meaning that optical device100may still provide desired functionality in most circumstances. Notably, the example shown inFIG.7is an extreme case in which the dead emitter104has zero power. In practice, a dead emitter104may have some power, meaning that the intensity reduction would in some cases be less severe.

As indicated above,FIGS.5,6A-6C, and7are provided as examples. Other examples may differ from what is described with regard toFIGS.5,6A-6C, and7.

In some implementations, as described above, a surface of a lens segment108may be curved to reduce divergence of a beam110(e.g., to permit optical power to be better confined within the FOV).FIG.8is a schematic diagram illustrating lens segments108having radius of curvature r (e.g., formed on a substrate of emitter array102) through which beams110from emitters104pass and exit at an angle θ (relative to the horizontal). However, if the curvature is too strong, then a resulting tilt of a beam110may be sensitive to errors in an offset from a lens center (illustrated as x0inFIG.8). For example, if the alignment tolerance is +/−2 μm, a beam nominally pointing 30 degrees off vertical (normal to the substrate surface) may be as much as +/−2 degrees off for a radius of curvature of 200 μm and the error will increase as the radius of curvature is reduced. Due to limits of the radius of curvature, the size of full (circularly symmetric) lenses can be large as noted above and lens segments are preferred. Further, a tight curvature would lead to a lumpy illuminator. In some implementations, to tolerate misalignment (e.g., an error in x0, not a target value for x0) of up to a few micrometers and to keep the angular profile centered (e.g., within a few degrees), a radius of curvature r may be between approximately 180 μm and approximately 450 μm (e.g., when lens segments108are formed in GaAs, which is a common substrate for VCSELs). For a radius of curvature in such a range, the offset x0from the center of lens segment108to beam110to tilt the beam by approximately 30 to 40 degrees is in on the order of tens of micrometers. Notably, when a lens segment108that is an entire lens (e.g., a radially symmetric lens, as shown inFIG.8) is used for each emitter104, an emitter-to-emitter pitch is limited by the pitch between adjacent lenses plens, which may be, for example, 100 μm to 200 μm. Such a limitation may result in a significant amount of space between emitters104being wasted and lead to a large and costly die. Thus, in some implementations, a lens segment108may be a portion (e.g., a few percent) of the area of an entire lens. Using such lens segments108may therefore reduce a size and cost of optical device100.

FIG.9is a schematic diagram illustrating an example optical device100including lens segments108that are portions of lenses (e.g., segments of radially symmetric lenses, rather than entire radially symmetric lenses). In the example shown inFIG.9, each emitter104is arranged under a lens segment108to direct a beam110and partially reduce beam divergence. Here, the lens segments108enable the pitch pebetween emitters104to be limited by a size of beams110at the lens segments108rather than a size of the entire lens. Notably, because emitter array102is typically relatively small (e.g., having a size of approximately 1 millimeter (mm)) in comparison to the scene being illuminated by optical device100(e.g., which may have a size on the order of hundreds of mm to a few meters (m)), a spatial location of emitters104on a chip does not change an observed intensity versus angle. Accordingly, lens segments108may be spatially rearranged in any order. In some implementations, the spatial configuration of lens segments108is configured to improve manufacturability (e.g. yield and reproducibility) of the integrated optical element106. In some implementations, the spatial configuration of lens segments108is configured to reduce the frequency or height of transitions between adjacent lens segments. In some implementations, the spatial configuration of lens segments108is configured to reduce power loss effects from potential failure modalities (e.g. adjacent emitter failures, edge failures, crystallographic dislocations, etc.) As further shown inFIG.9, in some implementations, lens segments108are recessed from a top surface of integrated optical element106by a standoff at a perimeter of an emission area of optical device100(e.g., an edge of the die). Here, lens segments108being recessed from the top surface by the standoffs may serve to protect surfaces of lens segments108from damage.

As indicated above,FIGS.8and9are provided as examples. Other examples may differ from what is described with regard toFIGS.8and9.

In practice, different designs for lens segments108of integrated optical element106can be used to provide the same intensity versus angle profile. For example, the design for lens segments108of integrated optical element106shown inFIG.10may provide the same intensity versus angle profile as that provided by lens segments108of integrated optical element106shown inFIG.1. Notably,FIG.10is diagram illustrating an example of an alternative design that provides the same intensity versus angle profile as that provided by the integrated directed beam diffuser shown in the optical device ofFIG.1when both electrodes are energized. When either one of the two electrodes is energized, the central or the exterior portions of the intensity profile vs angle is illuminated. Notably, the design shown inFIG.1causes beams110nearer to edges of emitter array102to be tilted comparatively more than beams110nearer to the center of emitter array102. In comparison, the design shown inFIG.10causes beams110on a left side of emitter array102to be tilted comparatively less than and beams110on a right side of emitter array102.

In some implementations, beams110with the comparatively less tilt may be grouped under one contact of emitter array102, while beams110with comparatively more tilt may be grouped under another contact (e.g., a separate anode or cathode) of emitter array102. That is, in some implementations, a first set of emitters104of emitter array102is connected to a first contact112aof optical device100and a second set of emitters104of emitter array102is connected to a second contact112bof optical device100, as illustrated inFIG.10. In such a case, as further illustrated inFIG.10, integrated optical element106may be designed to steer beams110from the first set of emitters104toward a center of the diffusion pattern and may steer beams110from the second set of emitters104toward one or more edges of the diffusion pattern. In some implementations, one or more emitters104in the first set of emitters104are at an edge of emitter array102and one or more emitters104in the second set of emitters104are at an edge of emitter array102, which improves addressability of the sets of emitters104.

FIG.11is a diagram illustrating an example of a simplified 2D spatial layout (e.g., a 9×9 layout) for beam steering provided by integrated optical element106. InFIG.11, each emitter104of emitter array102is represented by a box, and an associated arrow indicates a direction of tilt provided by integrated optical element106(as observed from directly above integrated optical element106). The dot in the center box represents a beam110pointing directly out of a plane ofFIG.11. InFIG.11, lens segments108nearer to a center of emitter array102provide comparatively less tilt than lens segments108nearer to edges of emitter array102. This design is consistent with the design for integrated optical element106shown inFIG.1.

An alternative layout is shown inFIG.12. InFIG.12, lens segments108are arranged such that beams110with comparatively less tilt are nearer to a corner of emitter array102(e.g., the top left corner of emitter array102), rather than being nearer to the center of emitter array102as in the case ofFIG.11. One advantage of the design of integrated optical element106associated withFIG.12is that addressing beams110being directed nearer to the center of the FOV is simplified as compared to doing so inFIG.11(e.g., since emitters104aimed nearer to the center of the FOV are at an edge of emitter array102). For example, optical device100may be flip-chip mounted on a submount, and traces going to an edge of optical device100can be routed on a single plane of the submount. Conversely, in the design shown inFIG.11, either optical device100requires traces that overlap to separately access emitters104nearer to the center, or the submount needs traces or vias—either of which adds cost and complexity to either optical device100or the submount. Another possible arrangement (not shown) is to arrange lens segments108such that emitters104being aimed nearer to the center of the FOV are in multiple locations along a perimeter (e.g., at corners) of emitter array102. In such an arrangement, failures of multiple adjacent emitters104may not result in a significant loss of functionality (e.g., since not all emitters104being aimed nearer to the center would be clustered together). Notably, the layouts inFIGS.11and12may be used to illuminate the FOV or sub-sections of the FOV.

FIG.13is a diagram illustrating a flip-chip mounted optical device100including integrated optical element106. In some implementations, as shown inFIG.13, an AR coating is formed on a top surface of optical device100to reduce reflection by the top surface of optical device100.

As indicated above,FIGS.10-13are provided as examples. Other examples may differ from what is described with regard toFIGS.10-13.

The integrated optical element106described above is comparatively more efficient than a conventional (discrete) diffuser. For example, a given beam110may be reduced in divergence to produce sharper edges of intensity versus angle profile, thereby improving FOV efficiency (e.g., by approximately 7%). Further, an AR coating can be more readily formed and kept on optical device100(e.g., as compared to the conventional diffuser). Conventional diffusers are commonly a polymer attached to glass and stamped to form the refractive pattern. Typically, an AR coating is a thin film of a dielectric material like a metal oxide or glass or a multi-layer stack of metal oxides or glasses of thickness comparable to the wavelength (fractions of a micrometer). Such thin dielectric films do not adhere well to polymers which may stretch much faster with temperature and crack the film. But AR coating materials are compatible with semiconductors. The reduction in reflection provided by the AR coating can provide a further increase in the efficiency (e.g., by approximately 4% to 8% depending if a conventional diffuser has the glass substrate side coated). Notably, there may be some (e.g., approximately 3%) absorption from the substrate. However, the overall improvement in efficiency even with such absorption may be significant (e.g., approximately 12%).

In some implementations, the arrangement of lens segments108can be selected so as at to simplify fabrication of optical device100. For example, the arrangement of lens segments108can be selected so as to reduce or eliminate abrupt changes in the profile of lens segments108on integrated optical element106.FIGS.14A and14Bare diagrams illustrating an example arrangement of lens segments108that reduces abrupt changes in a profile of lens segments108on integrated optical element106(e.g., as compared to the design shown inFIG.1). Notably, in the design shown inFIG.1, a transition between a given pair of adjacent lens segments108(most easily seen at the left-most and right-most ends of the integrated optical element106) is a vertical step. In some implementations, to ease fabrication, the arrangement of lens segments108may be selected as shown inFIG.14Aso that, for example, beams110on the two adjacent lens segments108on the left-most side of integrated optical element106are directed in generally opposite directions (e.g., a leftward direction and a rightward direction), rather than both being directed in generally the same direction (e.g., leftward, as in the design shown inFIG.1). Similarly, beams110on the two adjacent lens segments108on the right-most side of integrated optical element106are directed in generally opposite directions (e.g., a leftward direction and a rightward direction), rather than both being directed in generally the same direction (e.g., rightward, as in the design shown inFIG.1). Here, by comparingFIGS.14A and1, it can be seen that the abrupt step between these adjacent lens segments is not present in the integrated optical element106with such an arrangement, thereby simplifying fabrication of optical device100(e.g., because of abrupt changes in the profile of integrated optical element106may be difficult to manufacture).

Thus, in some implementations, surfaces of lens segments108may be sloped in alternating directions to cause beams110from emitters104of the emitter array102to be steered at alternating angles with respect to a surface of the emitter array102. Put another way, in some implementations, surfaces of two adjacent lens segments108may be sloped to cause beams110from two emitters104of the emitter array102to be steered at angles having opposite directions with respect to a surface of the emitter array102. As a particular example, a surface of a first lens segment108may be sloped to cause a beam110from a first emitter104of the to be steered at a first angle, and a surface of a second lens segment108may be sloped to cause a beam110from a second emitter104to be steered at a second angle. In this example, the second lens segment108is adjacent to the first lens segment108, and a direction of the second angle with respect to a surface of the emitter array102is opposite to a direction of the first angle with respect to the surface of the emitter array102.

Additionally, as illustrated inFIG.14B, in some implementations, transitions between regions where beams110exit (e.g., regions near edges of lens segments108where beams110are not incident) may be smoothed so that abrupt profile changes between lens segments108are further reduced. Because such regions do not have an optical function, these regions may be adjusted as suitable for fabrication requirements. As further shown inFIG.14B, in some implementations, a transition to a higher plateau outside of lens segments108may also be smoothed. Notably, the illustrations shown inFIGS.14A and14Bare for a 1D design, but these techniques can be similarly applied in a 2D design. In some implementations, by arranging lens segments108to reduce steps and smoothing the profile of the integrated optical element106, more compact emitter designs are enabled (e.g., as compared to a design without such arrangement or smoothing that will require comparatively more die area for step transitions). Notably, such arrangement may not be needed for angle changes that are relatively are small (e.g., +/−5 degrees), as abrupt steps may not be present in the profile of integrated optical element106in these regions.

As indicated above,FIGS.14A and14Bare provided as examples. Other examples may differ from what is described with regard toFIGS.14A and14B.

In some implementations, emitters104in an emitter array102may be connected in groups that change sequentially across the emitter array102. Such a configuration may be used, for example, to enable a scene to be scanned from negative to positive angles.

FIG.15is a diagram illustrating an example optical device100in which emitters104of 2D emitter array102are connected in groups that change sequentially across emitter array102. InFIG.15, emitter steering angle in the x-direction is indicated along the top of optical device100. As shown, steering angle in the x-direction alternates between negative angles and positive angles so as to minimize vertical transitions in the profile of integrated optical element106, as described above. Further, emitter steering angle in the y-direction is indicated along the left side of optical device100. As shown, steering angle in the y-direction alternates between negative angles and positive angles so as to minimize vertical transitions in the profile of integrated optical element106, as described above. In the example shown inFIG.15, emitters104are connected by a first metal layer (shown in gray) to form four groups that span steering angles from −24 degrees to −15 degrees (Group 1), −12 degrees to −3 degrees (Group 2), +3 degrees to +12 degrees (Group 3), and +15 degrees to +24 degrees (Group 4). Thus, in some implementations, emitters104in the emitter array102may be connected such that steering angles provided by the plurality of lens segments108change sequentially in a particular direction (e.g., the x-direction and/or the y-direction) across the emitter array102.

In some implementations, the optical device100shown inFIG.15may include a second metal layer to provide a thermal pad, an example of which is shown inFIG.16. In some implementations, as shown inFIG.16, the second metal layer may be formed over a dielectric layer (e.g., to prevent adjacent groups of emitters104from shorting together). In some implementations, such a design enables flip-chip bonding to a submount and connections to a driver.

In some implementations, optical device100may be designed such that connections for groups of emitters104are arranged on one side of optical device100. In some implementations, such an arrangement may enable, for example, driver connections on only one side of optical device100.FIG.17is a diagram illustrating an example optical device100in which connections for groups of emitters104are on one side of optical device100. InFIG.17, emitter steering angle in the x-direction is indicated along the top of optical device100. As shown, steering angle in the x-direction alternates between negative angles and positive angles so as to minimize vertical transitions in the profile of integrated optical element106, as described above. Further, emitter steering angle in the y-direction is indicated along the left side of optical device100. As shown, steering angle in the y-direction alternates between negative angles and positive angles so as to minimize vertical transitions in the profile of integrated optical element106, as described above. In the example shown inFIG.17, emitters104are connected by a first metal layer (shown in gray) in association forming four groups that span steering angles from −24 degrees to −15 degrees (Group 1), −12 degrees to −3 degrees (Group 2), +3 degrees to +12 degrees (Group 3), and +15 degrees to +24 degrees (Group 4).

As shown inFIG.17, the first metal layer may be formed so as to provide electrical connections for all four groups from one side of optical device100. Notably, in the example shown inFIG.17connections to Groups 1 and 2 are fully formed on the first metal layer, while connections to Groups 3 and 4 are only partially formed the first metal layer. In this example, connections for Groups 3 and 4 are completed on a second metal layer, which is illustrated inFIG.18. In some implementations, as further shown inFIG.18, the second metal layer may further provide a thermal pad for optical device100. In some implementations, as shown inFIG.18, the second metal layer may be formed over a dielectric layer (e.g., to prevent adjacent groups of emitters104from shorting together). Here the dielectric layer includes vias to permit connections to Groups 3 and 4 to be completed. In some implementations, such a design enables flip-chip bonding to a submount and connections to a driver.

As indicated above,FIGS.15-18are provided as examples. Other examples may differ from what is described with regard toFIGS.15-18.

The foregoing disclosure provides illustration and description, but is not intended to be exhaustive or to limit the implementations to the precise form disclosed. Modifications and variations may be made in light of the above disclosure or may be acquired from practice of the implementations. Furthermore, any of the implementations described herein may be combined unless the foregoing disclosure expressly provides a reason that one or more implementations may not be combined.