Optical Beam Receiver Assembly

Abstract

According to a first aspect of the present invention there is provided an optical beam receiver assembly comprising an optical filter layer, a beam shaping layer, an optical receiver, a substrate having the optical filter layer and the beam shaping layer, the optical receiver arranged to receive an optical beam that has passed through the optical filter layer and the beam shaping layer, the optical filter layer configured to allow transmission of the optical beam within a wavelength range in which the optical receiver operates and attenuate other wavelengths, and the beam shaping layer configured to spatially shape the optical amplitude of the optical beam over a particular portion of the optical receiver.

Description

[Technical Field]

[0001] The present invention relates to the fields of integrated photonics, target tracking and ranging, data processing and remote sensing. An optical beam receiver assembly is disclosed having one or more layers and an optical receiver, wherein the one or more layers optimize an incident optical beam to the optical receiver. [Background technology]

[0002] The optical beams collected / detected by optical receivers can be non-optimal (e.g., non-uniform), making these receivers susceptible to "blindness effects" or signal loss (due to undetected optical beams) or to being obscured by signal noise (due to background or atmospheric optical solar clutter). To address these issues, several design implementations for the optical receiver itself have been proposed. However, such designs typically involve trade-offs. Designing a single structure that simultaneously varies and receives an incoming optical beam can be very complex.

[0003] Recently, efforts have been made to reduce the reliance on beam receivers that simultaneously receive and enhance optical beam characteristics on the same physical structure. One example of such an approach involves the reductive allocation of separate structures to receive and enhance optical beam characteristics on separate but integrated physical structures, as in Zhang et al., Opt. Comm. 514, 2022. Zhang et al. disclose physically distinct but integrated optical components to receive and enhance optical beam characteristics (in the form of a photodetector) and focus the optical beam to a spot (in the form of a metalens on the photodetector) to enhance the responsivity of the photodetector. When the detected optical signal includes background noise (from both other transmitted signals and / or optical solar clutter) in addition to the detected main signal, the net received signal can be composed of a set of signals at multiple wavelengths (including that of the main signal), which introduces chromatic dispersion into the net received signal. For example, optical focusing to enhance responsivity can result in chromatic aberration, which hinders accurate detection of the optical beam. Summary of the Invention [Problem to be solved by the invention]

[0004] It would be desirable to provide improved optical components that address the above-mentioned shortcomings. [Means for solving the problem]

[0005] According to a first aspect, there is provided an optical beam receiver assembly comprising an optical filter layer, a beam shaping layer, an optical receiver, a substrate having the optical filter layer and the beam shaping layer, the optical receiver arranged to receive an optical beam that has passed through the optical filter layer and the beam shaping layer, the optical filter layer configured to allow transmission of the optical beam within a wavelength range in which the optical receiver operates and attenuate other wavelengths, and the beam shaping layer configured to spatially shape the optical amplitude of the optical beam over a particular portion of the optical receiver.

[0006] From the foregoing disclosure and more detailed description of various embodiments, it will be apparent to those skilled in the art that the present invention provides a significant advance in the art of modifying beam characteristics of an incident optical beam to enhance detection of the optical beam by an optical receiver system. Of particular importance in this regard is the ability of the present invention to provide enhanced beam detection that is not affected by dispersion, thereby preventing loss of signal information from the beam caused by the presence of blur / interference fringes on the resulting beam. Additional features and advantages of various embodiments will be better understood in view of the detailed description provided below. [Brief explanation of the drawings]

[0007] [Figure 1A] 1 is a schematic diagram of an embodiment of an optical beam receiver assembly having stacked layers. [Figure 1B] 1 is a schematic diagram of an embodiment of an optical beam receiver assembly having stacked layers.

[0008] [Figure 2A] 1 is a table showing a schematic side view of variations of discrete stack layers to define beam characteristics of a light beam. [Figure 2B] 1 is a table showing a schematic side view of variations of discrete stack layers to define beam characteristics of a light beam.

[0009] [Figure 3] FIG. 1 is a table showing a schematic isometric view of a stacked layer unit cell.

[0010] [Figure 4] FIG. 4 is a schematic isometric view of a stack layer comprising a unit cell as shown in FIG. 3 for defining beam characteristics of a light beam.

[0011] [Figure 5] 5 is a schematic isometric view of a stack made up of stack layers as described in FIG. 4 for defining beam characteristics of a light beam.

[0012] [Figure 6] 10 is an estimate of the optical field transmittance for additional embodiments of optical components in a stack.

[0013] [Figure 7] 1B , a table showing estimated electric field (|E|) profiles of array units of the stack along the xz and xy cross sections with and without the optical filter stack of FIGS. 1A and 1B .

[0014] [Figure 8] 1 is a table showing beam filtering and focusing and a schematic diagram showing beam filtering, expanding and focusing.

[0015] It should be understood that the accompanying drawings are not necessarily to scale, and depict somewhat simplified representations of various features illustrating the underlying principles of the present invention. The specific design features of the beam receiver assembly structures disclosed herein, including, for example, the specific dimensions of the stack layers, are determined in part by the particular intended application and use environment. Certain features of the illustrated embodiments have been enlarged or distorted relative to others to facilitate a clearer understanding. In particular, for example, thin features may be thickened for clarity of illustration. DETAILED DESCRIPTION OF THE INVENTION

[0016] In the following description, various embodiments are described with reference to the drawings, in which like reference characters generally refer to the same parts throughout the different views. It will be apparent to those skilled in the art, i.e., those with knowledge or experience in this technical field, that many uses and design variations are possible for the optical beam receiver assemblies disclosed herein. The embodiments described below illustrate the general principles of the present invention for providing an optical beam receiver assembly suitable for receiving and optimizing an incident beam to suit the application for which the optical beam receiver is designed. Other embodiments suitable for other applications will be apparent to those skilled in the art given the benefit of this disclosure.

[0017] This application relates to integrated optical devices, and in particular to optical beam receiver assemblies. The optical beam receiver assemblies have a multi-layer structure that receives an incident optical beam, modifies the beam characteristics with a substrate, and receives the resulting optical beam. The optical beam assembly may be part of an optical receiver system used, for example, in wireless communication applications.

[0018] An optical beam receiver assembly has at least the following components: a substrate with one or more optical modulation layers and an optical receiver. The optical receiver is responsible for extracting the data in the signal carried by the incident optical beam. The optical receiver therefore includes components such as one or more photodetectors and supporting infrastructure such as an array of scatterers, waveguides, diffraction gratings, arrays of lenses, optoelectronic switches, etc. Alternatively, the optical receiver may be a device that integrates one or more of these components, such as a photodetector with an integrated waveguide.

[0019] The layout of the optical receiver, such as the type of photodetector used (e.g., scatterers, waveguides, diffraction gratings, lens arrays, and / or optoelectronic switch arrays), and their relative positions relative to the photodetector, may be designed for the application of the optical receiver system to which the optical beam receiver assembly belongs. For example, a LIDAR receiver system may use a free-space avalanche photodetector or a waveguide-integrated avalanche photodetector combined with an on-chip waveguide integrated with an array of scatterers or diffraction gratings. While a free-space avalanche photodetector allows for direct detection of the incident optical field to the photodetector, an array of scatterers allows for coupling of the free-space optical field to an on-chip optical waveguide connected to the avalanche photodetector. An avalanche photodetector enables highly sensitive optical field detection when a high reverse bias voltage (i.e., near the breakdown voltage) is applied. As a result of the applied high voltage, electrical carriers in the transition region are accelerated, significantly increasing (in contrast to conventional photodetectors) the number of free electron-hole pairs when carriers generated from incident photons collide with bound electrons.

[0020] These layout considerations dictate that the optical beam entering the optical beam receiver assembly must be spatially concentrated on a particular portion of the optical receiver, depending on the design of the optical receiver. The operating wavelength range required by the application in which the optical receiver system will be used is another consideration. The one or more light modulation layers include at least one optical filter layer and at least one beam shaping layer, both configured to address the above considerations and output an optical beam optimized for the optical receiver design.

[0021] The optical filter layer provides wavelength-sensitive transmission by being configured to allow transmission of an optical beam in a predetermined wavelength range and attenuate other wavelengths. By setting this predetermined wavelength range to the wavelength range in which the optical receiver operates, the optical filter layer outputs a beam optimized for the environment in which the optical receiver operates and also mitigates chromatic dispersion that occurs when signals of multiple wavelengths are present. In one embodiment, the operating principle of the optical filter layer is due to refractive index changes in the form of a spatial structure arrangement containing metals and / or dielectrics that is on the order of larger, comparable, or smaller than the wavelength of the optical signal passing through the optical filter layer.

[0022] In one embodiment, the beam shaping layer is configured to spatially shape the optical amplitude of the optical beam onto a particular portion of the optical receiver, thereby providing a means to spatially focus the optical beam. This focusing concentrates the output beam into a spot of significantly smaller width compared to the original width of the incident optical beam entering the optical beam receiver assembly. In other embodiments, the beam shaping layer expands or collimates the optical beam rather than focusing it. Thus, a beam shaping layer configured to spatially shape the optical beam amplitude allows control of the spatial amplitude distribution of the optical signal collected by the optical receiver, and depending on the application, the optical receiver receives a focused, expanded, or collimated optical beam.

[0023] The optical filter layer, the beam shaping layer, and the optical receiver are arranged such that the optical filter layer and the beam shaping layer are located along a path of the optical beam that passes through the optical beam receiver assembly and reaches the optical receiver, such that the optical receiver receives the optical beam that has passed through the optical filter layer and the beam shaping layer.

[0024] The at least one optical filter layer and the at least one beam shaping layer may be realized as thin films, corrugated thin films and / or nanostructures disposed on or integrated into a substrate on which the optical receiver is disposed. The order of these layers may be varied. In one embodiment, the beam shaping layer is disposed between the optical filter layer and the optical receiver. The beam shaping layer may be disposed above the optical receiver. In another embodiment, the optical filter layer is disposed between the beam shaping layer and the optical receiver. The optical filter layer may be disposed above the optical receiver.

[0025] The optical beam receiver assembly is described in more detail below in conjunction with the accompanying figures.

[0026] Referring to FIG. 1A, a schematic block diagram 100 of an optical beam receiver assembly 101 is disclosed, which includes at least one optical filter layer (P≧1) 121 of an optical filter stack 120 and at least one beam shaping layer (Q≧1) 131 of a beam shaping stack 130 mounted on an optical receiver 110 disposed on a substrate 140.

[0027] The optical receiver 110 may comprise an array of free-space photodetectors, an array of scatterers seamlessly coupled to a waveguide-integrated photodetector (e.g., in the form of an optical phased array), an array of scatterers combined with a lens, and an optoelectronic switch (e.g., in the form of a focal plane switch array) also seamlessly coupled to a waveguide-integrated photodetector. These different components may be integrated on the same platform, such as an optical phased array combined with a waveguide-integrated photodetector.

[0028] The stacks (120 and 130) advantageously provide the ability to tailor the beam characteristics, i.e., the spatial distribution of the optical amplitude, to the beam receiver structure. The stacks 120 and 130 can be realized by phase masks made from, for example, silicon (Si), polysilicon, silicon nitride (Si3N4), silicon dioxide, germanium (Ge), lithium niobate (Li3NbO3), polymers, III-V compounds (i.e., alloys containing elements from groups III and V of the periodic table), or II-VI compounds (i.e., alloys containing elements from groups II and VI of the periodic table).

[0029] There may be any number of stack layers based on the configuration of the optical beam receiver assembly 101 selected for the application. However, while Figure 1A shows the optical filter stack 120 having multiple optical filter layers 121 and the beam shaping stack 130 having multiple beam shaping layers 131, another embodiment (not shown) has an optical beam receiver assembly with only a single optical filter layer and a single beam shaping layer.

[0030] The stack layers output a modulated light beam 162 for an optical receiver 110 disposed on the substrate 140. The optical filter layer 121 and the beam shaping layer 131 are arranged such that the optical receiver 110 receives the light beam that has passed through the optical filter layer 121 and the beam shaping layer 131, such that the modulated light beam 162 is the result of the incident light beam 142 being spectrally filtered by the optical filter stack 120 and spatially shaped by the beam shaping stack 130. The optical receiver 110 may include structures (such as grating structures) that induce light scattering, for example, to collectively couple the free-space light beam into an on-chip photodetector.

[0031] As shown in FIG. 1A , the optical filter stack 120 and the beam shaping stack 130 are stacked vertically on one another. For example, the second optical filter layer p=2 is vertically stacked on top of the first optical filter layer p=1, and the third optical filter layer p=3 is stacked on top of the second optical filter layer p=2. Meanwhile, the second beam shaping layer q=2 is vertically stacked on top of the first beam shaping layer q=1, and the third beam shaping layer q=3 is stacked on top of the second beam shaping layer q=2. The implementation of FIG. 1A uses a configuration in which the beam shaping layer 131 is disposed between the optical filter layer 121 and the optical receiver 110. Thus, the first beam shaping layer q=1 is disposed above the optical receiver 110, which is disposed on the chip substrate 140. The optical filter layer 121, the beam shaping layer 131, and the optical receiver 110 are shown aligned on the chip substrate 140.

[0032] Each optical filter layer 121 can include thin films of one material alternating with thin films of a different material. One or more optical filter layers 121 can have different thicknesses, or they can all have the same thickness. Taken together, the optical filter stack 120 includes multiple optical filter layers 121 of alternating high and low refractive index materials. In such a configuration, each optical filter layer 121 is configured to spectrally filter optical signals of a specific wavelength. By selecting the appropriate material combination and respective dimensions, the optical filter stack 120 can be configured to allow transmission of an optical beam within a wavelength range within which the optical receiver 110 operates and attenuate other wavelengths using one or more optical filter layers 121. Referring to FIG. 6 , the optical filter stack 120 can have one optical filter layer 121 in a configuration 602 that attenuates wavelengths below 1.2 μm and another optical filter layer 121 in a configuration 604 that attenuates wavelengths between 1.2 μm and 1.4 μm. The output modulated optical beam 162 includes optical signals with wavelengths above 1.4 μm.

[0033] Each beam shaping layer 131 can include periodically arranged unit cells, each having optical shaping elements with structures (cores / pillars) having cross sections that are ellipsoidal, polygonal, or closed Bézier curves. Thus, each beam shaping layer 131 can have multiple optical shaping elements with different cross sections separated by a distance, as described in more detail below. These optical shaping elements enable the beam shaping layer 131 to spatially shape the light amplitude and modify the light beam characteristics of the light beam. Such light beam characteristics include the spatial distribution of the light amplitude. Such modulation can further include modulation of the beam spot size and redistribution of the light beam for uniform illumination, beam width, and field of view of the light beam, and can also be configured to enhance the responsivity of photodetectors within the optical receiver 110. By selectively incorporating appropriate light shaping elements that affect the light beam characteristics, the beam shaping stack 120 can be configured to reduce aberrations (e.g., spherical aberration) in the focused beam that may be introduced by the wavelength-selective transmission and attenuation performed by the optical filter stack 120. In another configuration, the selected light shaping element also facilitates collimating the light beam into the optical receiver 110. For example, the beam shaping stack 130 may have one beam shaping layer 131 that spatially collimates the light beam into one portion of the optical receiver 110 and another beam shaping layer 131 that spatially focuses the light beam into another portion of the optical receiver 110.

[0034] Specific (overall) beam characteristics can optionally be modified independently and / or collectively by multiple beam-shaping layers 131. The beam-shaping layers 131 can have the same, similar, or distinct functions to define the desired optical beam characteristics. As the optical beam propagates through each layer of the beam-shaping stack 130, the characteristics can be sequentially modified. Each of the beam-shaping layers 131 can have various attributes that can be combined in multiple ways to modulate the optical beam characteristics. For example, various dimensions of the beam-shaping layers 131, including their core height (i.e., where the optical beam-shaping elements are located), their core thickness, or diameter, are selected based on the phase shift required to focus the optical beam at a specific location on the optical receiver 110.

[0035] FIG. 1B is a schematic block diagram 150 of an optical beam receiver assembly 151 according to another embodiment of the present invention.

[0036] Similar to the optical beam receiver assembly 101 of FIG. 1A, the optical beam receiver assembly 151 includes an optical filter stack 120 having at least one (P≧1) optical filter layer 121 and a beam shaping stack 130 having at least one (Q≧1) beam shaping layer 131. However, the order of the optical filter stack 120 and the beam shaping stack 130 relative to the optical receiver 110 is different. In the optical beam receiver assembly 101 of FIG. 1A, the beam shaping layer 131 is disposed between the optical filter layer 121 and its optical receiver 110, whereas in the optical beam receiver assembly 151 of FIG. 1B, the optical filter layer 121 is disposed between the beam shaping layer 121 and the optical receiver 110. The optical filter stack 120 of the optical beam receiver assembly 151 is mounted to the optical receiver 110, which is disposed on a substrate 140.

[0037] The configuration of the beam forming stack 130 and the optical filter stack 120 of the optical beam receiver assembly 151 of FIG. 1B is the same as that of the optical beam receiver assembly 101 of FIG. 1A and will not be described in further detail.

[0038] 2A and 2B are tables comparing the resulting distribution of the light beam on the beam receiver when the stacks are applied together and when they are applied separately.

[0039] 2A, in combination A, which includes optical filter stack 120 stacked vertically above optical receiver 110, the beam illuminated at optical receiver 110 has a width comparable to its width when it enters optical filter stack 120. Optical filter stack 120 does not spatially modify the amplitude distribution of the beam, but instead passes only signals in a specific wavelength band while spectrally filtering signals at other wavelengths.

[0040] In combination B, which includes a beam shaping stack (e.g., in the form of a single layer metalens) 130 stacked vertically above the optical receiver 110, the beam illuminating the optical receiver 110 is substantially concentrated to an area with an effective width that is smaller than its width when it enters the beam shaping stack 130. The concentrated spot size tends to be magnified by spurious signals outside the wavelength band of interest that arise from chromatic aberrations that result from the unequal focal lengths of the metalens at different wavelengths of light.

[0041] In combination C, which includes an optical filter stack 120 stacked vertically on a beam-shaping stack 130 and a beam-shaping stack 130 stacked vertically on an optical receiver 110, the beam illuminating the optical receiver 110 is significantly focused to a sharp point with an effective width significantly negligible relative to its width when it enters the beam-shaping stack 130. This increases the responsivity of the photodetector within the optical receiver 110 compared to the case without such focusing. The optical filter stack 120 selectively passes signals of certain wavelengths while filtering signals of other wavelengths. As a result, the metalens effectively focuses the spectrally filtered optical beam to an equal focal length, resulting in a sharp beam focus on the optical receiver 110.

[0042] In Figure 2B, in combination D, which includes an optical filter stack 120 stacked vertically on the optical receiver 110, the optical field illuminated on the optical receiver 110 can be approximated as containing random light rays. The optical filter stack 120 does not spatially vary the amplitude distribution of the beam, but instead passes only signals in a specific wavelength band while spectrally filtering signals of other wavelengths. As a result of the random illumination, the optical field received by the optical receiver 110 is spatially random.

[0043] In combination E, which includes a beam-shaping stack (e.g., in the form of a single-layer metalens) 130 stacked vertically on the optical receiver 110, the optical field illuminated on the optical receiver 110, which can be approximated as including random rays, is substantially collimated in certain regions into a relatively uniform beam. The resulting beam tends to be less uniformly distributed due to the presence of spurious signals outside the wavelength band of interest resulting from chromatic dispersion. As a result, the resulting optical field received by the optical receiver 110 can include different possibilities for beam distribution.

[0044] In combination F, which includes optical filter stack 120 stacked vertically on beam shaping stack 130 and beam shaping stack 130 stacked vertically on optical receiver 110, the optical field illuminated on optical receiver 110, which can be approximated as containing random light rays, is highly collimated in a specific region to form a highly uniform beam. Optical filter stack 120 selectively passes signals of specific wavelengths while filtering signals of other wavelengths, and beam shaping stack 130 effectively collimates the spectrally filtered optical beam to form a highly uniform beam on optical receiver 110. As a result, the optical field received by optical receiver 110 is a coherent beam distribution.

[0045] 2A and 2B illustrate the advantages of the present invention. The optical filter stack 120 is structurally coupled / laminated with the beam shaping stack 130 to null out beam distortions resulting from chromatic dispersion (e.g., chromatic aberrations described in combination B). In addition to enabling focusing of the light beam, the beam enhancing stack 130 can redefine and modify the spatial amplitude distribution.

[0046] 3 is a table showing the unit cell structure 122 of the optical filter layer 121 of the optical filter stack 120 and the unit cell structure 132 of the beam shaping layer 131 of the beam shaping stack 130. The core 126 of the optical filter layer 121 includes thin film layers surrounded by an undercladding 125 and an overcladding 124, and the core 126 has a height H 120 The underclad 125 and overclad 124 form part of each unit cell 122, and each may comprise one or more optical materials such as Si, polysilicon, Si3N4, Ge, Li3NbO3, polymers, and III-V compounds. The core 133 of the beam-shaping layer 131 comprises a pillar surrounded by the underclad 135 and overclad 134, and the core 133 extends from the underclad to the overclad by a height H 130The undercladding 135 and overcladding 134 form part of each unit cell 132 and may each similarly comprise one or more optical materials, such as Si, polysilicon, Si3N4, Ge, Li3NbO3, polymers, and II-V compounds. The cores 133 corresponding to the array of unit cells are separated by either a uniform distance (to form a symmetrical array) or a non-uniform distance. The stack of optical filter layers 121 and the stack of beam-shaping layers 131 can be obtained using an overcladding that serves as an undercladding for the next layer in the optical filter stack 120 and the beam-shaping stack 130, respectively. That is, adjacent optical filter layers 121 share a cladding, and adjacent beam-shaping layers 131 share a cladding, with the cladding acting as a relay between the two adjacent layers. In the beam-shaping layer 131, the height of each pillar may be uniform, but the thickness and distance between each pillar may vary, for example, by fixing the thickness of the overcladding, which is typically between 0.01 μm and 5 μm. Thus, one or more of these claddings (undercladding 125 and overcladding 124 for optical filter layer 121, and undercladding 135 and overcladding 134 for beam-shaping layer 131) may have different thicknesses. Such optical components with distinct core heights and fixed overcladding and undercladding thicknesses can be easily fabricated layer by layer using standard manufacturing techniques, which is advantageous for commercial-scale and economically sustainable mass production of beam receiver assemblies.

[0047] The optical filter stack unit cell core 126 within the unit cell 122 has an amplitude a that is reflected by the core 126 with a factor r and transmitted with a factor t. λi 110 operates in a wavelength range over which the optical receiver 110 operates, while destructive interference results in attenuation of other wavelengths.

[0048] Meanwhile, the beam-shaping unit cell 132 receives an optical input field of amplitude a. The input optical field a propagates through the unit cell 132 and produces an output optical signal ae ikH 130 (using the plane wave approximation), where the wave vector k=2πn eff / λ o , n eff is the effective refractive index of the pillar structure, λ o is the wavelength of the optical field. The beam shaping layer 131 is not limited to a core with two discrete height levels (binary core), but can be extended to a core with multiple discrete height levels (multilevel core), a core with continuous height levels forming one or more continuous functional curves, or even a core with no repeating units.

[0049] FIG. 4 is another table, related to FIG. 3 , showing isometric schematic views of layers 121 of optical filter stack 120 and beam shaping layer 131 of beam shaping stack 130. Optical filter layer 121 and beam shaping layer 131 include optical filter layer unit cells 122 and beam shaping layer unit cells 132, respectively. Optical filter layer 121 includes a thin film core 123 surrounded by undercladding 125 and overcladding 124. Beam shaping layer 131 includes a cylindrical core 136 surrounded by undercladding 135 and overcladding 134. The distance between adjacent cores in each beam shaping layer unit cell 132 can be selected arbitrarily, and the dimensions (both height and diameter / diagonal / thickness) of beam shaping layer unit cells 132 can be based on the intended phase shift at a particular location on beam shaping layer 131. Thus, the dimensions (height, diameter, and / or diagonal) of each optical shaping element in beam shaping layer 131 depend on the focus required at the location of the optical shaping element.

[0050] The distance between adjacent cores of the beam-shaping layer unit cells 132 may be the same or may vary. The height of the beam-shaping layer unit cells 132 may be between 0.01 μm and 10 μm, the diameter or cross-section of the core of the beam-shaping layer unit cells 132 may be between 0.01 μm and 3 μm, and the periodic distance between adjacent beam-shaping layer unit cells 132 may be, for example, arranged in a square lattice between 0.01 μm and 3 μm. A lattice refers to a regular arrangement of the beam-shaping layer unit cells 132, for example, a triangular, square, or hexagonal two-dimensional lattice arrangement of the beam-shaping layer unit cells. Thus, the optical shaping elements in the beam-shaping layer 131 may be arranged in the lattice according to either a triangular, square, or hexagonal arrangement. Advantageously, as shown in FIG. 1A , at least one optical filter layer 121 may be stacked vertically on at least one beam-shaping layer 131, and at least one beam-shaping layer 131 may be stacked on top of the optical receiver 110.

[0051] The optical phase shift at each periodic lattice point is a function of the dimensions of the beam shaping layer unit cell 132. In the example shown in Figure 4, the core of the beam shaping layer unit cell has a cylindrical pillar structure. The beam shaping layer unit cell 132 has a height H that introduces the required phase shift. 130Alternatively, the beam-shaping layer unit cells 132 may be multi-layered or have a continuous spatial height. The cylindrical pillar structures 133 have elongated top surfaces 137 and sidewalls 138 extending downward from the top surfaces. The refractive index of the cylindrical pillar structures may be greater or less than that of the surrounding cladding. That is, for each beam-shaping layer 131, the cladding has a different refractive index from its core. In FIG. 3, the beam-shaping layer unit cells 132 introduce an optical phase shift based on their binary-thickness structure. The different optical phase shifts induced by each beam-shaping layer unit cell 132 at different points on the beam-shaping layer 131, taken together, allow the optical beam to the optical receiver 110 to be intelligently tailored to specific desired requirements.

[0052] In one example, the dual-thickness structure of the core 136 of the beam-shaping layer unit cell 132 is a cylindrical pillar structure with a thickness (consistently discontinuous) of 0.4 μm. The cylindrical pillar structure is surrounded by an overclad 134 and an underclad 135 within the unit cell 132. The beam-shaping layer unit cell 132 receives an optical input field of amplitude a. The input optical field a propagates through the unit cell 132 and generates an output optical signal ae (in the plane wave approximation). ikH where the wave vector k=2πn eff / λ o , n eff is the effective refractive index of the pillar structure, λ o is the wavelength of the optical field.

[0053] FIG. 5 is another table associated with FIGS. 3 and 4 showing isometric schematic views of the optical filter stack 120 and the beam-shaping stack 130. The cores 123 of the optical filter stack 120, which are made of thin films, are alternately stacked with cladding (124 and 125). The cores 133 of the beam-shaping stack 130, which are made of cylindrical pillars, are periodically arranged. The optical phase shift at each periodic lattice point of the layer 131, represented by the unit cell shown in FIG. 3, is k(n eff(which is a function of ) and / or H 130 In one example, n eff where π varies with the diagonal or diameter D of the pillar structure. Advantageously, such pillar structures (which constitute the core) can be fabricated using standard fabrication techniques, such as lithography and deposition, and include optical materials such as Si, polysilicon, Si3N4, Ge, Li3NbO3, polymers, and II-V compounds. According to one embodiment, the height of each pillar within a stacked layer unit cell is fixed based on layer-based deposition or etching processes in conventional semiconductor fabrication processes. Advantageously, for beam-shaping layer unit cells 132, the diameter of the pillar structure is a determining factor for introducing an optical phase shift. For example, for a 0.4 μm thick polysilicon cylindrical pillar surrounded by silicon dioxide overclad and underclad layers within a unit cell with a periodic distance of 0.75 μm between adjacent unit cells, a diameter from 0 to 0.75 μm (i.e., 0 to 1 times the periodic distance between adjacent unit cells) produces a monotonically increasing phase shift from 0 to 2π. Therefore, the intended optical phase shift at any point on the phase mask can be engineered based on the relationship between the diameter and the diameter-induced optical phase shift. Similarly, in the case of a metalens, the phase profile of a light beam is transformed based on a modulo 2π operation, which implies that the radii of the pillar structures within the unit cell are periodically varied.

[0054] In known optical receivers, the signal amplitude of the incident beam may be weak, resulting in signal loss. This problem can be addressed by defining and modifying the spatial distribution of the optical amplitude of the optical beam using a beam-shaping layer 131 vertically integrated on the optical receiver 110. That is, the beam is spatially focused to a point of interest on the optical receiver 110. As a result of spatial focusing by the beam-shaping stack 130, the incident photon flux at the point of interest increases. This increases the absorbed optical field from the beam, generating more electron-hole pairs and, for example, increasing the responsivity (ratio of current to optical power) of the photodetector on the optical receiver 110. The beam-focusing beam-shaping layer 131 is designed so that the optical phase of each horizontally adjacent beam-shaping layer unit cell 132 is shifted by the following equation:

number

number

number

[0055] In known optical receivers integrated with beam-focusing structures, a beam focused onto the optical receiver, e.g., a free-space photodetector, tends to have an increased beam width due to the presence of optical signals of different optical wavelengths. Such aberrations are particularly pronounced in settings where optical signals from a variety of different light sources are present and / or where the main signal to be detected is attenuated after traveling through free space, improving the signal-to-noise ratio. This issue is addressed by the optical filter stack 120 vertically integrated above the beam-focusing layer 131 and optical receiver 110 (as shown in FIG. 1A), which can spectrally filter signals of other wavelengths and pass the main signal of interest of a specific wavelength. As a result of the spectral selectivity of the optical filter stack 120, the incident beam onto the beam-focusing layer 131 contains signals of a specific wavelength. In this way, the resulting beam from the beam-focusing layer 131 is directed toward a specific spatial point of interest "free of chromatic aberration," thereby improving the responsivity of the free-space photodetector on the optical receiver 110. Improved optical-to-electrical conversion efficiency directly translates into improved detection sensitivity, which is desirable for many beam detection applications, including LiDAR and free-space transceivers.

[0056] Figure 6 shows the results of a finite-difference time-domain (FDTD) numerical simulation of optical filtering using vertical stacking of optical filter stacks on an optical receiver. The numerically simulated optical filter stack 600 has defined parameters, such as ten 100-nm polysilicon thin-film layers alternating with 250-nm silicon dioxide (SiO2) thin-film layers (i.e., 0.35 μm spatial period) in configuration 602 for filtering optical signals in wavelength range A, and ten 100-nm polysilicon thin-film layers alternating with 305-nm silicon dioxide (SiO2) thin-film layers (i.e., 0.405 μm spatial period) in configuration 604 for filtering optical signals in wavelength range B. Different layer configurations can be stacked to combine filtered signal ranges (both optical wavelength ranges A and B in configuration 606). The optical filter stack 600 is supplied with air above the top SiO2 overclad. The beam directionality for the optical filter stack is 14.5°. The periodic variation of refractive index in the optical filter stack 600 results in a spectral stopband (negligible optical transmission) centered at a wavelength of ∼550 nm, with a stopband spectral width of ∼250 nm. Other variations in the central stopband wavelength and stopband spectral width can be achieved by modifying the materials and structural dimensions of the optical filter stack. Multiple sets of layers forming optical filter stacks with various stopband attributes (e.g., different stopband wavelengths) can be combined in multiple ways to provide a net range of stopband central wavelengths and stopband spectral widths.

[0057] FIG. 7 is a table showing the estimated resulting electric field intensity (|E|) profiles of additional array units of the beamforming stack 130 along the xz and xy cross sections with and without the optical filter stack 120 702 and 704.

[0058] In example 702, the numerically simulated metalens array unit cells forming the optical beam shaping stack 120 have defined parameters such as 0.5 μm thick cylindrical polysilicon structures as phase mask unit cells with a pitch d=0.65 μm, and radii ranging from (0.275 to 0.475) × d to represent a 2π phase shift. Each layer also includes a 0.25 μm thick silicon dioxide overclad (between the unit cell cores) and air in the region above the overclad of the top layer. The beam directionality relative to the optical filter stack 120 is 14.5°. The metalens array has a focal length of ∼4.5 μm at 1.55 μm, centered at Δx=1 μm and Δy=0 from the center of the array unit cell. In configuration 704 without the optical filter stack 120, an optical signal with an optical wavelength between 1.0 μm and 1.6 μm is launched into the beam shaping stack 130 for beam focusing. At these wavelengths, the focal length of the metalens array varies from ∼4.5 μm to ∼7.5 μm, resulting in an expanded concentrated region at a constant distance from the beam shaping stack 130 (here 4.5 μm).

[0059] The beam shaping stack 130 may include beam shaping layers with the same and / or different functionality to simultaneously achieve the same, similar, or different functionality to modify the beam characteristics. For example, the beam shaping stack 130 may include beam shaping layers with beam focusing and beam expansion functions combined in multiple ways, as in the example shown in FIG. 8. Both the beam expansion layer 831 and the beam focusing layer 861 of the beam shaping stack 130 may be advantageously fabricated from a metalens array with the array unit cell shown in FIG. 5 and the estimated resulting electric field intensity (|E|) profile shown in FIG. 7.

[0060] The beam expansion layer 831, which includes metalens array cells, expands the width of the beam incident on the layer. As a result, the net width of the beam after passing through the beam focusing layer 861 increases from w1 to w2, and the expanded beam becomes less spatially focused. Thus, the devices disclosed herein are scalable and provide flexibility in vertically integrating beam shaping layers onto the optical receiver 110, using discretized phase-shifting unit cells (i.e., beam shaping layer unit cells) to modify the beam characteristics onto the optical receiver 110. Different stack layers with the same, similar, or different functions can be used by vertically integrating them above the optical receiver 110, thereby achieving multi-functionality (feature integration) on a single integration platform.

[0061] Furthermore, the optical receiver 110 with its vertically stacked layers is compact, and integration is achieved entirely on the substrate 140. The beamforming stack 130 can also be precisely positioned via chip design without the need for any mechanical positioning, thereby enabling a robust system that is less prone to mechanical errors. The optical receiver 110 is also cost-effective because the platform is fully integrated on the chip, and additional stack layers can be easily added using the same manufacturing steps. This convenience in manufacturing additional stack layers enables mass production of such devices, thereby improving cost efficiency.

[0062] It will be apparent from the foregoing disclosure and detailed description of specific embodiments that various modifications, additions, and other alternative embodiments are possible without departing from the true scope and spirit of the invention. The embodiments discussed have been chosen and described to provide the best explanation of the principles of the invention and its practical application, thereby enabling those skilled in the art to use the invention in various embodiments with various modifications suited to the particular uses intended. All such modifications and variations are within the scope of the invention, as determined by the appended claims when interpreted in accordance with the breadth and breadth permitted in fairness, law, and equity.

Claims

1. an optical filter layer; a beam shaping layer; a substrate having an optical receiver, the optical filter layer, and the beam shaping layer, the optical receiver positioned to receive the optical beam that has passed through the optical filter layer and the beam shaping layer; Equipped with the optical filter layer is configured to allow transmission of the optical beam within a wavelength range in which the optical receiver operates and attenuate other wavelengths; the beam shaping layer is configured to spatially shape the optical amplitude of the optical beam over a particular portion of the optical receiver. Optical beam receiver assembly.

2. the beam shaping layer is disposed between the optical filter layer and the optical receiver.

10. The optical beam receiver assembly of claim 1.

3. the optical filter layer is disposed between the beam shaping layer and the optical receiver; 10. The optical beam receiver assembly of claim 1.

4. further comprising a plurality of said optical filter layers; An optical beam receiver assembly according to any one of claims 1 to 3.

5. The plurality of optical filter layers are formed by alternating high refractive index materials and low refractive index materials.

5. An optical beam receiver assembly as defined in claim 4.

6. one or more of the optical filter layers have different thicknesses; 6. An optical beam receiver assembly according to claim 4 or 5.

7. Adjacent optical filter layers share a cladding. An optical beam receiver assembly according to any one of claims 4 to 6.

8. the cladding has a different refractive index from the core of each of the adjacent optical filter layers; 8. An optical beam receiver assembly as defined in claim 7.

9. one or more of the claddings have different thicknesses; 9. An optical beam receiver assembly according to claim 7 or 8.

10. the optical filter layer enhances the light beam within a wavelength range in which the optical receiver operates; An optical beam receiver assembly according to any preceding claim.

11. further comprising a plurality of said beam-shaping layers; An optical beam receiver assembly according to any preceding claim.

12. the beam shaping layer includes optical shaping elements having one or more cross sections that are elliptical, polygonal, or closed Bezier curves; An optical beam receiver assembly according to any preceding claim.

13. the optical shaping elements are arranged in a grid according to either a triangular, square, or hexagonal arrangement; 13. An optical beam receiver assembly as defined in claim 12.

14. The size of each optical shaping element depends on the focus required at the position of said optical shaping element.

14. An optical beam receiver assembly according to claim 12 or 13.

15. one or more of the lenses have different dimensions including one or more of a height, a diameter, and a diagonal; 15. An optical beam receiver assembly according to claim 14.

16. Adjacent beam-shaping layers share a common cladding; 16. An optical beam receiver assembly according to any one of claims 11 to 15.

17. the cladding has a different refractive index than the core of each of the adjacent beam-shaping layers; 17. An optical beam receiver assembly according to claim 16.

18. one or more of the claddings have different thicknesses; 18. An optical beam receiver assembly according to claim 16 or 17.

19. the optical receiver comprises one or more of an array of free-space photodetectors, an array of scatterers, a waveguide integrated photodetector, an array of lenses and optoelectronic switches, and a grating; An optical beam receiver assembly according to any preceding claim.

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