transmitter array

Abstract

In an optical transmitter device, when point emitters are placed on the focal plane of a lens system, each point emitter will point to a specific free-space angle depending on its position relative to the longitudinal center axis of the lens system. Point emitters comprising end-fire tapers in combination with turning mirrors and microlenses provide improved performance because, unlike grating couplers, end-fire tapers enable uniform broadband operation in all possible polarization states. A turning mirror can be added to direct the light emitted from the end-fire tapers vertically upwards, which both enables a two-dimensional point emitter array and a more simplified assembly process.

Description

Technical Field

[0001] This disclosure relates to a transmitter array, and more particularly to a transmitter array for a LIDAR system. Background Technology

[0002] Conventional integrated optical phased arrays emit and receive light beams at various controllable angles for a wide range of applications, including free-space communication, holography, and light detection and ranging (LIDAR). A LIDAR sensor is an optical remote sensor that measures the distance to a target by using pulsed or modulated signals from a laser to illuminate the target and measuring the time it takes for the light to travel round-trip between the target and the LIDAR sensor's receiver. When a reflected pulsed or modulated signal is detected, the time of flight of the pulsed or modulated signal corresponds to the distance to the sensed target. LIDAR sensors are important components in autonomous vehicles, drone navigation systems, and robotic interactions, but are currently relatively expensive and large.

[0003] Conventional methods for achieving large-aperture on-chip non-mechanical beam steering, such as phased arrays, may have one or more of the following problems: 1) high power consumption, 2) limited to one-dimensional steering, 3) complex beamforming algorithms, and 4) strict requirements for manufacturing process uniformity.

[0004] To overcome some of the aforementioned problems, one-dimensional or two-dimensional point emitter arrays are arranged on the chip. As described in WO2020 / 0506307, published on March 19, 2020, entitled "Beam Steering and Receiving Method Based on an Optical Switch Array," which is incorporated herein by reference, when point emitters are placed on the focal plane of a lens system, each point emitter will point to a specific free-space angle depending on its position relative to the longitudinal central axis of the lens system. However, point emitters that can be manufactured in commercially available silicon photonics fabrication plants are typically grating couplers, which may have one or more of the following problems: 1) low emission efficiency, 2) non-uniformity in the manufacturing process, 3) strong wavelength dependence, and 4) inability to utilize optical polarization to achieve a low-loss monostable system. Summary of the Invention

[0005] Therefore, this disclosure relates to a light emitter device comprising:

[0006] A plurality of point emitters, arranged in an array comprising multiple rows and multiple columns of point emitters, each of the plurality of point emitters comprising: one of a plurality of end-fire tapers configured to emit a respective beam in a respective transmission direction; and

[0007] Multiple reflectors are used to redirect the respective beams substantially perpendicular to their respective transmission directions. Attached Figure Description

[0008] The invention will be described in more detail with reference to the accompanying drawings, which represent preferred embodiments of the invention, wherein:

[0009] Figure 1 This is a side view of a light emitter device according to an embodiment of this disclosure;

[0010] Figure 2 It is to remove the steering base plate. Figure 1 A plan view of the transmitter array of the device;

[0011] Figure 3A It is to remove the steering base plate. Figure 2 A partial plan view of the transmitter array;

[0012] Figure 3B It includes the steering base plate. Figure 3A An end view of a portion of the transmitter array;

[0013] Figure 3C It includes the steering base plate. Figure 3A A cross-sectional view of part of the transmitter array;

[0014] Figure 3D It has another example of a steering reflector and includes a steering substrate. Figure 3A A cross-sectional view of part of the transmitter array;

[0015] Figure 4A It is to remove the steering base plate. Figure 2 A partial plan view of another embodiment of the transmitter array;

[0016] Figure 4B It includes the steering base plate. Figure 4A An end view of a portion of the transmitter array;

[0017] Figure 4C It includes the steering base plate. Figure 4A A cross-sectional view of part of the transmitter array;

[0018] Figure 4D It has another example of a steering reflector and includes a steering substrate. Figure 4A A cross-sectional view of part of the transmitter array;

[0019] Figure 5 It has a steering base plate Figure 2 A cross-sectional view of the point emitter in the transmitter array;

[0020] Figure 6 yes Figure 5 A top view of the point emitter;

[0021] Figure 7 yes Figure 2 A cross-sectional view of another embodiment of the point transmitter of the transmitter array;

[0022] Figure 8 yes Figure 7 A top view of the point emitter;

[0023] Figure 9A It is used for Figure 1 A side view of an exemplary embodiment of the steering substrate of the light emitter device;

[0024] Figure 9B yes Figure 9A A top view of the steering substrate; and

[0025] Figure 9C yes Figure 9A A bottom view of the steering substrate. Detailed Implementation

[0026] While this teaching has been illustrated with various embodiments and examples, it is not intended to limit this teaching to these embodiments. Rather, as those skilled in the art will understand, this teaching encompasses various alternatives and equivalents.

[0027] Long-range LiDAR systems rely on the efficient transmission and reception of highly focused or collimated beams at different angles. While lenses are typically associated with imaging, they can also be used for beamforming and beam steering. (See reference...) Figure 1 The light emitter device 1 includes an emitter array 2 and a beam steering lens system 3. For beamforming, when the point emitter 5 from the emitter array 2... 11 Up to 5 nm When placed on the focal plane F of the lens system 3, it can emit a highly collimated output beam 4. o (Infinite conjugate). Based on the reciprocity theorem, the same applies to backpropagation, thus the parallel input beam 4 illuminating the lens system 3. i Focus will be placed on point-and-shoot transmitter 5 11 Up to 5 nm At one of the captured light spots, there is a slight spread limited by lens aberrations and diffraction. For beam steering, the shaped (e.g., substantially collimated or focused) far-field beam angle α depends on the point emitter 5 11 Up to 5 nm The output beam 4 is positioned on the focal plane F relative to the longitudinal central optical axis OA of the lens system 3. oThe beam angle α is determined by the following equation: α = arctan(d / f), where d is the distance from the center of the focal plane (i.e., the point where the optical axis OA coincides with the focal plane F), and f is the focal length of lens system 3. Therefore, by using point emitter 5... 11 Up to 5 nm The transmitter array 2 is placed on or near the focal plane F of the lens system 3, and then the point transmitters 5 are selectively turned on and off. 11 Up to 5 nm To enable one or more output beams 4 o A full LIDIA system is achieved by steering in the desired direction at the desired beam angle α. This method differs fundamentally from optical phased arrays because it does not require controlling the relative optical phase between transmitters and only requires activating one point transmitter at a time. 11 Up to 5 nm In addition, multiple point emitters can be activated simultaneously. 11 Up to 5 nm To transmit in different directions (i.e., with different beam angles α) 11 To α nm ) has multiple output beams 40.

[0028] As described below, the transmitter array 2 may include: for supporting point transmitters 5 11 Up to 5 nm The optical waveguide structure 8 includes a main substrate 7 and an upper steering substrate 9 for supporting beam-directing and / or beam-shaping elements. Ideally, the point emitter 5... 11 Up to 5 nm Arranged to include multiple (n) rows of point emitters 5 11 Up to 5 nm and multi-(m) column point transmitter 5 11 Up to 5 nm Point launcher 5 11 Up to 5 nm An array of point emitters. Typically, point emitters in rows are aligned, and point emitters in columns are aligned, but the rows and / or columns of point emitters can be offset. Point emitters 51 to 5... n There are many methods, including end-fire cones, end-fire cones with steering mirrors, single-layer grating couplers, and double-layer grating couplers.

[0029] The design of lens system 3 is critical to the system's performance. Lens system 3 may include multiple lens elements if desired. Much of the design of lens system 3 involves trade-offs between F-number, field of view, and aperture size. However, several design priorities are possible: for example, a) a design with a telecentric image plane, where the image space originates from point emitter 5. 11 Up to 5 nma) The principal rays are all parallel to the optical axis OA; b) the diffraction limit is reached across the entire field of view; and c) the image spatial numerical aperture (NA) of lens system 3 is essentially matched to that of point emitter 5. 11 Up to 5 nm The NA. The principal ray parallel to the optical axis OA will cause the point emitter 5 11 Up to 5 nm Designed to be perfectly vertical. Minimizing lens curvature aberrations enables an output beamwidth of 4. o Minimum spread and receive input beam 4 i The best possible focus. Point emitter 5 11 Up to 5 nm Preferably, the output beam 4 is emitted at a beam angle α that can be completely captured by the lens system 3. o For example, if point emitter 5 11 Up to 5 nm If one or more of the NA values ​​in the lens system 3 are greater than the image space NA of the lens system 3, then the emission from the point emitter 5... 11 Up to 5 nm A portion of the emitted light will not pass through lens system 3, thus causing a loss.

[0030] Reference Figure 2 The light emitter device 1 may further include at least one light source, preferably an array of light sources, and at least one photodetector, preferably optically connected to a corresponding point emitter 5 of the emitter array 2. 11 Up to 5 nm A photodetector array. Preferably, the light source array and the photodetector array include transceivers 111 to 112. n The array. Each transceiver is 111 to 112. n It can include a laser and a photodetector, with the laser generating an output beam 4 o At least one of them, the photodetector detects the input beam 4 i At least one of them. It can be achieved via transceiver 111 to 11 n Switching matrix 12 between transmitter array 2 and transmitter array 5 to provide direction to point transmitter 5 11 Up to 5 nm Selectively transmit light and from point emitter 5 11 Up to 5 nm Light is selectively received. Therefore, in order to select the desired point emitter 5 corresponding to the desired beam angle α... 11 Up to 5 nm The controller 13 can select the corresponding point transmitter 5 11 Up to 5 nm Transceiver 111 to 11 of a row in the row (e.g., 1 to n) nOne of the light sources in the matrix 12 is selected by turning on and / or off the individual switches 14 in the switching matrix 12 to select the point emitter 5 in that row. 11 Up to 5 nm One of them. For example, for 4 emitters in each row, 5 11 Up to 5 nm The switching matrix 12 can have a single input port optically connected to a switch tree comprising (m-1=3) switches 14 (e.g., a 2x2 on-chip Mach-Zehnder (MZI) interferometer), which can be selectively activated to output beam 4. o The output is directed to the desired output port. Multiple optical waveguide cores 15 extend parallel to each other between the output ports of the switching matrix 12 to the point emitters 51 to 52. n Each optical waveguide core 15 may include a curved portion, for example, a 90° curve, at its end, with each curved portion having a different radius of curvature configured to align with a respective point emitter 5 in a row. 11 Up to 5 nm Point launcher 5 11 Up to 5 nm Each row in the array can be combined with a point emitter 5 11 Up to 5 nm The nxm emitter array 2 point emitter 5 11 Up to 5 nm The other rows of the column are aligned. Ideally, the point emitters 5 of emitter array 2... 11 Up to 5 nm The spacing is from 5μm to 1000μm, or based on the focal length f, transmitter array 2 size L, and angular resolution required by the LIDAR system:

[0031] Spacing = Resolution / (2 * arctan(L / 2f)) * L

[0032] Similarly, when the incident beam 4 i One of the transmitters at the same point, 51 to 5 n When the incident beam is received, the incident beam 4 i The signal is transmitted in reverse through the corresponding optical waveguide 15 to the switching matrix 12, and then back to the corresponding transceivers 111 to 112. n The corresponding photodetector.

[0033] Reference Figures 3A-4D Point launcher 5 11 Up to 5 nm Each may include an end cone 21 in combination with a steering reflector 22 (e.g., a mirror) and an optional microlens 23 (see details). Figure 5 and Figure 6Unlike grating couplers, the end-emitting cone 21 enables uniform broadband transmission of light with all possible polarization states. The deflector 22 can be arranged in a cavity or trench 24 within the optical waveguide structure 8 to orient the light emitted from the end-emitting cone 21 parallel to the optical axis OA of the lens system 3, for example, vertically upwards and perpendicular to the upper surface of the emitter array 2. This achieves both a two-dimensional point emitter array 2 and a simplified assembly process.

[0034] A single groove 24 can be provided for multiple point emitters, and the ends of multiple end-firing cones 21 located nearby are oriented into this groove. Ideally, for an entire row of point emitters (e.g., 5...), 11 Up to 5 14 Set a trench 24; however, for each point emitter (e.g., point emitter 5) 34 Set a trench 24, or a group (e.g., 2 or 3) of point emitters (e.g., point emitters 5). 23 and 5 24 Alternatively, a trench 24 may be provided. Each trench 24 is configured to receive one or more corresponding deflector reflectors 22 aligned with the end of the end cone 21, and the depth may be between 2 μm and 150 μm, for example, extending beyond the end cone, or preferably extending to the bottom of the optical waveguide structure 8 to the main substrate 7, and / or more preferably extending into the main substrate 7 (shown in dashed lines).

[0035] In addition, a row of point emitters (e.g., 5) can be used. 11 Up to 5 14 The output beam 4 is set with a single steering reflector 22 and multiple end cones 21. o (and input beam 4) i The signal is directed to that point transmitter. Ideally, this would be for an entire row of point transmitters (e.g., 5). 11 Up to 5 14 A steering reflector 22 is set up; however, for each point emitter (e.g., point emitter 5) 34 Set a steering reflector 22, or a group (e.g., 2 or 3) of point emitters (e.g., point emitter 5). 23 and 5 24 Setting up a steering reflector 22 is also possible. See below for reference. Figures 9A to 9C As mentioned above, some or all of the steering reflectors 22 can be mounted on the steering base plate 9. Figure 3C and Figure 4C ), or mounted (e.g., deposited or etched) in trench 24 ( Figure 3D and Figure 4DThe width and height of the steering reflector 22 are approximately 5 μm to 100 μm, which is larger than the near-field mode size of the end-firing cone 21 divided by cos(45°).

[0036] Figure 3A A top view of the dot emitter array 2 with the steering substrate 9 removed is shown, specifically, a row of dot emitters 5 is shown. 11 Up to 5 14 Four point emitters are shown; however, additional point emitters are also within the scope of this invention. Figure 3B A cross-sectional view of a portion of the transmitter array 2 taken along section BB is shown. Figure 3C and Figure 3D It is along section CC (i.e., from the outer waveguide core 15 to the fourth point transmitter 5) 14 The image shows a cross-sectional view of the transmitter array 2 with another deflector 22. The transmitter array 2 may include an optical waveguide structure 8 consisting of one or more optical waveguide layers configured to form an optical waveguide core 15 and an end-firing taper 21 surrounded by cladding (i.e., a material with a low refractive index). The optical waveguide core 15 and the end-firing taper 21 may be made of silicon (Si) or silicon nitride (SiN), or both Si and SiN, or any other suitable optical waveguide core material. The optical waveguide structure 8 may be mounted on the upper part of a main substrate 7, for example, grown on the upper part of the main substrate, wherein the upper and lower cladding layers 32 and 33 surround the optical waveguide core 15 and the end-firing taper 21. The upper and lower cladding layers 32 and 33 may be made of oxide materials such as silicon dioxide (SiO2), for example, with a thickness of 2-5 μm, and the main substrate 7 may be made of silicon, quartz, or any suitable material. At least some end-emitting cones 21 may have a length of 100 μm to 400 μm, and gradually decrease in length from the original width (e.g., 400 nm to 500 nm wide) of the optical waveguide core 15 multiplied by 200 nm to 250 nm in thickness, for example, decreasing by 25% to 75%, preferably by about 50%, until the tip has a width and original thickness (e.g., 200 nm to 250 nm) between 50 nm and 400 nm, but the thickness may also be gradually reduced to less than that of the optical waveguide core 15 if necessary. Preferably, the ends of the end-emitting cones 21 may be symmetrical, for example, square (200 nm x 200 nm). At least some end-emitting cones 21, for example, point emitters 5 11 The waveguide core 15 may include an inverted taper that extends at least in width from its original dimensions (e.g., width) to a wider width, such as 2x to 10x or 1μm to 4μm. The thickness may also be extended if desired. Some end tapers 21 may be narrower, while others may be wider. Some end tapers 21 may be more or less narrower than others, and some end tapers may be more or less wider than others.

[0037] During transmission from the end of the end-emitting cone 21, the guiding mode spreads in the feed waveguide core 15. Mode spread controls beam divergence and the emission efficiency through the lens system 3. The minimum achievable NA of the bare silicon end-emitting cone entering the vicinity of the lens system 3, for example, air, is approximately 0.38, which is challenging for the design of the lens system 3 because of the output beam 4. i A portion of the aberrations may extend beyond the NA of lens system 3 and be lost. Alternatively, even if lens system 3 has a sufficiently high NA, optical aberrations typically present in high-NA lenses may degrade the performance of the LIDAR system. Aberration-free high-NA systems are generally expensive to manufacture and sensitive to misalignment and environmental disturbances such as shock and temperature.

[0038] Figure 4A A partial top view of another embodiment of the dot emitter array 2 with the steering substrate 9 removed is shown, specifically, a row of dot emitters 5 is shown. 11 Up to 5 14 . Figure 4B A cross-sectional view of a portion of the transmitter array 2 taken along section BB is shown. Figure 4C and Figure 4D It is along the cross section CC (i.e., from the outer double-layer optical waveguide core 15' to the fourth point transmitter 5) 14 The image shows a cross-sectional view of the transmitter array 2 with another deflector 22. The transmitter array 2 may include an optical waveguide structure 8, which consists of two optical waveguide layers configured to form a double-layered waveguide core 15' and a double-layered end-cone 21'. The inclusion of the second waveguide layer enables mode profile engineering, which also allows for a change in the NA of the transmitter array 2; that is, emitting light into a coupled mode with a wider mode spread results in a smaller NA. The double-layered waveguide core 15' and the double-layered end-cone 21' may be made of two similar waveguide materials with similar refractive indices, such as silicon (Si) or silicon nitride (SiN), or two different waveguide materials with different refractive indices (e.g., a first refractive index (e.g., Si) greater than a second refractive index (e.g., SiN)), or any other suitable waveguide core material. The waveguide layer can be mounted on the upper part of the main substrate 7, for example, grown on the upper part of the main substrate, wherein the upper and lower cladding layers 32 and 33 surround the dual-waveguide core 15' and the end-emitting taper 21'. The upper and lower cladding layers 32 and 33 can be made of oxide materials, such as silicon dioxide (SiO2), for example, 2 μm thick, and the main substrate 7 can be made of silicon or any suitable material.

[0039] Figure 5 and Figure 6Cross-sectional and top views are shown, respectively, of the steering reflector 22 and optional microlens 23 (if desired) combined with end-projection cone 21 or double-ended projection cone 21'. The steering reflector 22 can be formed (e.g., etched) from a separate (e.g., silicon or quartz) steering substrate 9, having angled wall corners, for example, at 45° to the longitudinal axis of the end-projection cone 21 defining the transmission direction, and can be coated or configured with a reflective layer or coating 42, such as silver, copper, aluminum, gold, or Bragg grating. If the steering reflector 22 has a sufficiently high refractive index n... reflector For example, silicon, and trench 24 has a sufficiently low refractive index r. reflector For example, air, making beam 4 o Most of them are greater than the critical angle arcsin(n reflector / n trench If the angle of impact on the inclined wall is such that coating 42 can be omitted, and beam 4 o It can be reflected by total internal reflection. The flat vertical sidewalls of the facing end cones 21 or 21' of the steering reflector 22 can be coated with an anti-reflection (AR) coating 43 to minimize Fresnel reflection from them. Similarly, the top surface of the microlens 23 or the steering substrate 9 can be coated with an AR coating. The output beam 4 from the end cones 21 or 21' adjacent to the trench 24 o The light beam expands, for example, from 1 μm to 10 μm, through the air gap and passes through the vertical sidewall, i.e., the AR coating 43, then impacts and is reflected off the tilted reflective layer or coating 42, which redirects the light path substantially perpendicular to the original propagation direction in the end-emitting cone 21 and upwards from the upper surface of the point emitter array 2. Then, the respective output beams 40 (and input beams 4...) i The emission pattern of the point emitter can be reshaped, e.g., collimated or focused, by the corresponding microlens 23. The goal of the microlens 23 is to convert the NA of the point emitter to a smaller value, e.g., less than 0.2, and preferably less than 0.15 for a more practical lens design. The diameter of each microlens 23 can be from 25 μm to 200 μm. Each steering reflector 22 can have an edge with a length between 6 μm and 90 μm. The gap and / or groove 24 can include a refractive index matching material between the end cone 21 and the steering reflector 22, e.g., a material with a refractive index between the effective refractive index of the pattern of the end cone 21 and the refractive index of the steering reflector 22, to at least reduce back reflections at the interface between the end cone 21 and the gap and / or the interface between the gap and the steering reflector 22.

[0040] Reference Figure 7 and Figure 8 In order to further reduce the size of the point transmitter 5 11 Up to 5 nmThe NA can be configured with suspended optical waveguide structures 50 optically connected to the ends of some or each of the end-firing cones 21 or 21'. The suspended optical waveguide structure 50 can be constructed from a cladding material (e.g., SiO2) that now forms the optical waveguide core, which is surrounded by a bag of material (e.g., air) with a lower refractive index forming the cladding. The suspended optical waveguide structure 50 can be suspended above the main substrate 7 by removing (e.g., etching) one or more substrate materials from the main substrate 7 and / or the steering substrate 9 and / or from the cladding materials of the upper and lower claddings 32 and 33 forming the bag or chamber 51 around the suspended optical waveguide structure 50 below and / or around it. Ideally, each trench 24 can be enlarged to extend below and / or around the suspended optical waveguide structure 50 to form a bag or chamber 51. Figure 8 As shown, the steering substrate 9 can also be etched in a selected area above the suspended waveguide structure 50 to form the channel 52. Figure 9C This design ensures that the optical mode of the suspended waveguide structure 50 does not leak into the main substrate 7 and / or the steering substrate 9. Therefore, the NA of the suspended waveguide structure 50 / end emitter 21 or 21' can be reduced to less than about 0.25, preferably less than 0.2, allowing the microlens 23 to convert the NA of the point emitter to less than 0.20, preferably less than 0.15. The suspended waveguide structure 50 can extend 2 μm to 50 μm into the chamber 51 or trench 24, while the end emitter 21 or 21' can extend slightly into the chamber 51 or trench 24, but less than the full length of the suspended waveguide structure 50. The suspended waveguide structure 50 can have a thickness of, for example, 6 μm to 8 μm, the same as the overall waveguide structure 8, or it can be made thinner than the waveguide structure by locally removing some of the upper cladding 32. The suspended waveguide structure 50 can have a constant width approximately the same as its thickness, for example, 6 μm to 8 μm. The suspended optical waveguide structure 50 can taper gradually, i.e., its width and / or height narrows towards its outer free end (dashed line), or it can taper gradually in the opposite direction, i.e., its width and / or height widens towards its outer free end. Ideally, the end-emitting cone 21 is located at the vertical and horizontal center of the waveguide structure 50.

[0041] Furthermore, in some or all of the above embodiments, the steering reflector 22 may include an integrated curved reflective surface 53 on its inclined surface or forming its inclined surface, to further reduce the number of point emitters 5. 11 Up to 5 nm The NA. For example, a spherical, conical, or aspherical surface with a radius of curvature of 0.1 mm to 1.0 mm can be formed (e.g., etched or deposited) on the inclined surface of the steering reflector 22. In embodiments with or without the curved reflective surface 53, the microlens 23 may be unnecessary and may be omitted.

[0042] Reference Figures 9A to 9CThe steering reflectors 22 and microlenses 23 can be fabricated on the same steering substrate 9, thereby allowing multiple steering reflectors 22 and multiple microlenses 23 to be configured on the same steering substrate 9. The steering substrate can then be bonded to the upper part of the photonic chip including the emitter array 2. Therefore, the reflective layer or coating 42, the AR coating 43, and the AR coating on each microlens 23 can be applied (e.g., coated) to corresponding features of the steering substrate 9 in a manufacturing process separate from the fabrication of the optical waveguide structure 8. Furthermore, the multiple steering reflectors 22 can comprise a single monolithic structure extending the length of the steering substrate 9 for reflecting point emitters (e.g., 5) from a column of the emitter array 2. 14 5 24 5 34 5 44 and 5 n4 Multiple output beams 4 o and the point transmitters (e.g., 5) that reflect the input beam 41 to the columns of transmitter array 2. 14 5 24 5 34 5 44 and 5 n4 ).

[0043] For illustrative and explanatory purposes, the above description of one or more embodiments of the invention has been given. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations can be made based on the above teachings. The scope of the invention is not limited by this detailed description, but is defined by the appended claims.

Claims

1. A light emitter device comprising: a plurality of point emitters arranged in an array comprising a plurality of rows of point emitters and a plurality of columns of point emitters, each of the plurality of point emitters comprising one of a plurality of end-fire tapers respectively having a tapered or widened width light waveguide core configured to emit a respective light beam in a respective transmission direction; and a plurality of reflectors for redirecting the respective light beams substantially normal to the respective transmission directions.

2. The optical transmitter apparatus of claim 1, wherein, At least some of the plurality of point emitters further comprise a microlens for shaping the respective light beams.

3. The optical transmitter apparatus of claim 1, wherein, At least some of the plurality of end-fire tapers comprise a double-layer end-fire taper.

4. The optical transmitter apparatus of claim 3, wherein, Each of the double-layer end-fire tapers comprises a first silicon layer and a second silicon nitride layer.

5. The optical transmitter apparatus of claim 1, wherein, At least some of the plurality of end-fire tapers have a width narrowed by 25% to 75%, to between 50 nm to 400 nm.

6. The optical transmitter apparatus of claim 1, wherein, At least some of the plurality of end-fire tapers have a width expanded to between 2x to lOx, or between 1 pm to 4 pm, of an original dimension of the light waveguide core.

7. The light emitter device of claim 1, further comprising: a host substrate for supporting the plurality of point emitters; and a light waveguide structure comprising: a plurality of light waveguide cores, each of the plurality of light waveguide cores extending to a respective one of the plurality of end-fire tapers; and a cladding surrounding the plurality of light waveguide cores. At least some of the plurality of light waveguide cores comprise a double-layer light waveguide core.

8. The optical transmitter apparatus of claim 7, wherein, Each double-layer light waveguide core comprises a first silicon layer and a second silicon nitride layer.

9. The optical transmitter apparatus of claim 8, wherein, The light waveguide structure comprises a plurality of trenches, each of the plurality of trenches adjacent to an end of at least one of the plurality of end-fire tapers for receiving each of the respective light beams; 10. The optical transmitter apparatus of claim 7, wherein, and wherein each of the plurality of reflectors is mounted in one of the plurality of trenches, and each reflector comprises a reflective surface at an oblique angle to the respective transmission direction. The reflective surface comprises a curved surface for shaping the respective light beams.

11. The optical transmitter apparatus of claim 10, wherein, 12. The light emitter device of claim 10, further comprising a turning substrate mounted on an upper surface of the light waveguide structure; each of the plurality of reflectors extends from the turning substrate into one of the plurality of trenches. wherein, 13. The light emitter device of claim 12, further comprising a plurality of microlenses configured to shape each of the respective light beams; and the plurality of microlenses are mounted on the turning substrate. wherein a first group of the plurality of waveguide cores are configured to direct a respective first group of the plurality of end-fire tapers toward a first trench of the plurality of trenches; 14. The optical transmitter apparatus of claim 10, wherein, and wherein each of the first group of the plurality of end-fire tapers is directed at a first reflector of the plurality of reflectors arranged in the first trench. At least one of the plurality of end-fire tapers comprises a suspended light waveguide extending therefrom into an adjacent one of the plurality of trenches; 15. The optical transmitter apparatus of claim 10, wherein, wherein the suspended light waveguide comprises a suspended waveguide core comprising a same material as the cladding, surrounded by a pocket disposed in the light waveguide structure, and the host substrate comprises a cladding material having a lower refractive index than the suspended waveguide core. ​ 16. The optical transmitter apparatus of claim 15, wherein, Each suspended optical waveguide includes a tapered sidewall that widens or narrows in width along the transmission direction.

17. The optical transmitter apparatus of claim 10, wherein, At least one of the plurality of reflectors is mounted on the main substrate in one of the plurality of grooves.

18. The optical transmitter apparatus of claim 17, further comprising: a turning substrate mounted on an upper surface of the optical waveguide structure; and a plurality of microlenses mounted on the turning substrate and configured to shape each of the respective light beams.

19. The optical transmitter apparatus of claim 1, further comprising a lens system including a focal length and an optical axis for redirecting the respective light beams at respective beam angles as a function of a position of a respective one of the plurality of point transmitters relative to the optical axis.

20. The optical transmitter apparatus of claim 1, further comprising: at least one light source for generating the respective light beams; and a switching matrix for selectively directing the respective light beams to one of the plurality of point transmitters.

21. The optical transmitter apparatus of claim 20, further comprising at least one photodetector for detecting an incident light beam received by the plurality of point transmitters.

22. The optical transmitter apparatus of claim 10, further comprising an index matching material in the grooves between the plurality of end-fire tapers and the plurality of reflectors, the index matching material having an index of refraction between an effective index of refraction of the plurality of end-fire tapers and an index of refraction of the plurality of reflectors.

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