Optical phased array with linearly scalable phase shifters for two-dimensional beam steering

Abstract

An optical phased array for two-dimensional steering of a light beam includes optical waveguides each having a plurality of scatterers. A first segment of the optical waveguides is adapted to guide the light beam in an x-direction and includes a first optical phase shifter. A second segment of the optical waveguides is adapted to guide the light beam in a different direction than the first segment and includes a second optical phase shifter.

Description

Technical Field

[0001] This invention relates to beam steering, and more specifically, to an optical phased array that uses a light field of fixed wavelength to control a beam in different dimensions and directions. Background Technology

[0002] Recent advances in silicon photonics have led to the development of nanophotonic optical phased arrays (OPAs). An OPA antenna is a photonic component capable of altering the lobe direction of an emitted beam in real time. In applications such as optical detection and ranging (LiDAR) systems and free-space transceivers, this ability to dynamically and precisely change the direction of the emitted beam is extremely useful for guiding beams carrying information signals to specific targets and / or receivers.

[0003] OPA beam steering has traditionally relied on photonic components, which include movable mirrors controlled by hydraulic pumps and microelectromechanical systems (MEMS). Further miniaturization efforts have yielded beam steering elements that are modulated based on material structural properties (such as liquid crystals, ferroelectric and phase change materials) or optical properties (such as refractive index and wavelength).

[0004] Among various beam steering methods, modulation based on optical properties is particularly suitable for on-chip beam steering. This can be achieved by using an optical phase shifter and a tunable light source to change the optical phase difference of the light field at the beam emitter; this is achieved by inducing a refractive index shift in the optical waveguide in the OPA and an optical wavelength shift in the light field transmitted to the optical waveguide in the OPA, respectively. To achieve two-dimensional (2D) beam steering, an optical phase shifter is typically used to control the beam in one dimension, and a tunable light source is used to control the beam in the other dimension. However, using wavelength shift for beam steering presents several challenges: i. Laser gain media that allow for large wavelength shifts are uncommon; ii. In LiDAR systems, the characteristics of the object being detected and the ranging distance vary with wavelength; iii. In free-space transceivers, using wavelength for beam steering makes it impractical to use unique wavelengths for different data streams; iv. Finding other photonic components (such as waveguides and photodetectors) within the beam control system that support a similar wide wavelength range as the beam control platform can be challenging; v. Continuously adjusting the optical power of the beam field emitted by the beam control platform to counteract variations in solar irradiance of ambient light at different wavelengths in free space (which the platform's beam field must compete with) can be complex. Therefore, it is crucial to have a system capable of guiding a beam in different directions and dimensions using a beam field with a fixed wavelength.

[0005] Although 2D beam steering using purely optical phase shifters can be achieved on conventional beam control platforms that use fixed-wavelength beam control, the number of optical phase shifters is typically non-linearly related to the number of emitters in the array row. This leads to the following problems: i. the beam control system can be cumbersome to manage; ii. the platform will occupy a large amount of space required for the optical phase shifters; iii. the beam control platform is energy inefficient due to the large number of optical phase shifters.

[0006] It is desirable to provide an improved photonic component that can guide a light beam to different directions and dimensions using a light field of fixed wavelength (coherent light) via optical phase shifters; wherein the number of optical phase shifters is linearly proportional to the number of rows of the OPA array. Summary of the Invention

[0007] According to a first aspect, an optical phased array for two-dimensional beam steering is provided, comprising optical waveguides, each waveguide having a plurality of scatterers. A first segment of the optical waveguides is adapted to guide the beam in the x-direction and includes a first optical phase shifter. A second segment of the optical waveguides is adapted to guide the beam in a direction different from the first segment (e.g., in the y-direction) and includes a second optical phase shifter.

[0008] Based on the foregoing disclosure and the following more detailed description of various embodiments, those skilled in the art will understand that the present invention provides significant advancements in OPA technology. Particularly important in this regard is the invention's potential to provide OPAs with 2D beam steering using optical phase shifters in number linearly proportional to the number of rows in the OPA array. Additional features and advantages of the various embodiments will be better understood from the detailed description provided below. Attached Figure Description

[0009] Figure 1 The diagram illustrates, according to certain embodiments of this specification, a method of guiding a light beam using a fixed wavelength in two directions or dimensions (2D) by modulating the optical phase of the light field in the waveguide along the rows and columns of the OPA.

[0010] Figure 2 A schematic diagram is shown illustrating the use of an optical phase shifter to modulate the optical phase of an optical field in a waveguide along a column of an OPA, according to certain embodiments of this specification.

[0011] Figure 3 A schematic diagram illustrating the use of an optical phase shifter to modulate the optical phase of an optical field in a waveguide along the rows of an OPA, according to certain embodiments of this specification, is shown.

[0012] Figure 4A schematic diagram is shown illustrating, according to certain embodiments of this specification, the optical phase of the optical field modulated in the waveguide along the row of the OPA using an optical phase shifter in the last column.

[0013] Figure 5 The present specification illustrates the use of an optical phase shifter to modulate an out-of-plane light field scattered by a scatterer located at column n of the OPA, according to certain embodiments thereof. The optical phase, which in turn modulates the scattered beam θ on the x-axis of line m. x A directional diagram.

[0014] Figure 6 The present specification illustrates the use of an optical phase shifter to modulate an out-of-plane light field scattered by a scatterer located at row m of an optical phased array, according to certain embodiments thereof. The optical phase, which in turn modulates the beam θ scattered out of the plane along the y-axis at column n=1. y A directional diagram.

[0015] Figure 7 A schematic diagram illustrating the use of a metallic thermo-optical phase shifter to guide a beam in the x and y dimensions is shown according to certain embodiments of this specification.

[0016] Figure 8 shows schematic diagrams illustrating, according to certain embodiments of this specification, the use of an optical phase shifter in the form of a highly doped semiconductor thermo-optic heater to guide a light beam in the x-dimensional direction, and the use of a modulator based on the pn junction plasmon dispersion effect to guide a light beam in the y-dimensional direction, both using a fixed wavelength of light.

[0017] Figure 9 An optical phase shifter according to several preferred embodiments of this specification is shown. Figure 9 The four embodiments of the model are partially equidistant schematic diagrams of a phase shifter based on pn junction plasma dispersion effect, a highly doped semiconductor thermo-optical phase shifter, and a metal thermo-optical phase shifter.

[0018] Figure 10 The phase shift produced by one embodiment of the OPA according to this specification is shown. And an example simulation of the doping effect relative to the voltage decay applied to a 6 mm long pn-doped optical phase shifter.

[0019] Figure 11 The present specification illustrates the estimated z-component of the electric field of a photonic component at different refractive indices of a waveguide forming part of an OPA, according to several embodiments thereof. This component can be modulated using a phase shifter of a waveguide located on or otherwise integrated into the OPA.

[0020] Figure 12 It is sent to the waveguide The light field at different optical phase differences (i.e., phase difference in the y-axis) A comparative diagram of the polar coordinates of the far-field intensity generated under the condition that the input optical field can be modulated using a phase shifter of a waveguide located on or otherwise integrated onto the OPA.

[0021] It should be understood that the accompanying drawings are not necessarily drawn to scale, but rather present a simplified representation of various features illustrating the basic principles of the invention. Specific design features of the OPA disclosed herein, including, for example, the specific dimensions of the scatterer / emitter, will be determined to some extent by the particular intended application and usage environment. Some features of the illustrated embodiments are enlarged or distorted relative to other features to aid in clarity of understanding. In particular, for example, thin features may be thickened for clarity of illustration. Unless otherwise stated, all dimensions, orientations, and positions mentioned refer to the orientations shown in the drawings. Detailed Implementation

[0022] Those skilled in the art, i.e., those with knowledge or experience in this field, will appreciate that the optical phased arrays disclosed herein have numerous uses and design variations. The following detailed discussion of various alternative features and embodiments will illustrate the general principles of the invention with reference to an optical phase assembly for 2D beam steering using phase shifters, the number of which is linearly proportional to the number of rows in the plurality of optical phased arrays. This contrasts with conventional OPAs that operate with fixed optical wavelengths for 2D beam steering, which use optical phase shifters whose number is non-linearly proportional to the number of rows in the OPA array. The OPA disclosed herein can be used as a beam control system, for example, as part of a LiDAR system or a free-space transceiver; and can be used as both a transmitter and a receiver. Other embodiments suitable for other applications will be apparent to those skilled in the art in light of the benefits of this disclosure.

[0023] Figure 1A schematic diagram of an optical phased array (OPA) 100 according to certain embodiments of this specification is shown, illustrating 2D beam steering of a light field using a fixed wavelength by modulating the optical phase of a light field in a series of one or more waveguides along rows (M) and columns (N) of the OPA. The OPA includes an array of photonic components operatively connected in rows and columns, having a first segment of optical phase shifters 117 generally adjacent (below, above, to one side, or to the other) or otherwise integrated (or embedded) therein to waveguide 100 and scatterer 121 (which may include a series of rows and columns of the array), and a second segment of optical phase shifters 118 adjacent to or otherwise integrated with waveguide 119 (which may contain another series of rows or columns of the array), wherein waveguide 119 is operatively connected to the first segment. The first segment is capable of controlling the light beam in the x-dimensional direction and includes at least one first optical phase shifter 122 (forming array 117), which is typically adjacent to or otherwise integrated therein with at least one (M≥1) waveguide 110, and includes a plurality of (N) optical nanostructures (also referred to as scatterers or emitters) 121 positioned at periodic points 112 along each waveguide in the segment. The second segment is capable of controlling the light beam in a dimension different from x, typically the y-dimensional direction (i.e., 90° azimuthally from the x-dimensional direction). The second segment includes at least one second optical phase shifter 123 (forming array 118), which is adjacent to or otherwise integrated therein with at least one waveguide 119 operatively connected to the waveguide 110 in the first segment. Each phase shifter 122, forming a portion of array 117, modulates the optical phase of the light field in the optical waveguide 110, while each phase shifter 123, forming a portion of array 118, modulates the optical phase of the light field in the optical waveguide 119 connected to the optical waveguide 110. OPA can be scaled up to have any number of M×N optical waveguides and scatterers. Each m optical waveguide in the M optical waveguides 119 is configured to receive the light field propagating to the m optical waveguides in the M optical conductors 110. The subscripts m and n represent the rows and columns of the array, respectively. In a preferred embodiment, each column may include the same type of optical phase shifter, and there may be only one column of optical phase shifters in the second segment. Optionally, each group of optical phase shifters may be formed as different layers (a first layer for the first optical phase shifter, a second layer for the second optical phase shifter, wherein the first layer is adjacent to each corresponding waveguide, and the second layer is adjacent to each corresponding waveguide). Furthermore, the first optical phase shifter may include a different material than the second optical phase shifter. Both the first and second optical phase shifters may be adjacent to or integrated into the corresponding waveguides.

[0024] Preferably, such photonic components in the OPA can be fully realized on a chip using standard fabrication techniques (such as photolithography and deposition) and standard photonic materials (e.g., including but not limited to silicon (Si), silicon nitride (Si3N4), germanium (Ge), lithium niobate (Li3NbO3), barium titanate (BaTiO3), and indium phosphide (InP)). Optionally, the wavelength of the input light field can be short-wavelength in the infrared region of the electromagnetic spectrum, for example, 1.4 μm to 1.7 μm. Depending on the application of the photonic component, visible light wavelengths (0.38 μm to 0.75 μm) and near-infrared wavelengths (0.75 μm to 1.4 μm) can also be used. One or more electrical connections can be provided between the first optical phase shifter in the first segment and the second optical phase shifter in the second segment. Furthermore, in a LiDAR system, the controller can be adapted to work with the scatterer 121 and an array of optical phase shifters (122 and 123) (117 and 118) adjacent to or otherwise integrated into at least one waveguide (110 and 119), and to receive the emitted light field reflected from the object, and to combine the information about the object's surface properties based on the reflected light received by the scatterer and the waveguide by the processor.

[0025] Waveguides (110 and 119) can be circular or rectangular (ribbed or ridged) waveguides with an elongated top surface and sidewalls extending from the top surface. The refractive index of the waveguide core can be greater than that of the surrounding waveguide cladding. The waveguide cladding can include a lower cladding and an upper cladding. Waveguides can include any of several different types of waveguides. For example, waveguides can be based on total internal reflection (which constitutes the vast majority of optical waveguides traditionally used in integrated photonics), slotted waveguides, and surface plasmon polariton waveguides. Alternatively, in-plane scattering waveguides can be used, such as waveguides formed from photonic crystals (which also use total internal reflection) and metamaterials. The composition of each of the multiple waveguides can be at least one of, for example, Si, SiO2, BaTiO3, Li3NbO3, InP, III-V compounds, II-VI compounds, and polymers. Each of the multiple waveguides can be doped with p-type or n-type materials. Waveguides can support any optical waveguide mode, such as transverse electric modes and transverse magnetic modes. Scatterer / emitter 121 can be a Mie scatterer or a Rayleigh scatterer. More specifically, Mie scattering refers to the scattering of a light field from a scatterer whose diameter, width, or diagonal is typically close to the wavelength of the incident light field, while in Rayleigh scattering, the diameter, width, or diagonal of the scatterer is at most one-tenth the wavelength of the incident light field. Each of the plurality of scatterers can be composed of at least one of, for example, Si, SiO2, BaTiO3, Li3NbO3, InP, III-V compounds, II-VI compounds, and polymers. Each of the plurality of scatterers can also be doped with a positively charged dopant (p-type material) or a negatively charged dopant (n-type material). Types of positively charged dopant include, for example, boron, gallium, and aluminum; while types of negatively charged dopant include, for example, arsenic, phosphorus, and antimony. Each of the plurality of scatterers can be embedded in a corresponding waveguide, and / or each of the plurality of scatterers can be in contact with the top or sidewall of the corresponding waveguide.

[0026] Figure 2 A schematic diagram of the columns (N) of the OPA in row m according to an embodiment of the present invention is shown. Each row includes an optical phase shifter 122 for shifting the optical phase of the light field in waveguide 110, which is perturbed by a plurality of scatterers 121. Waveguide 110 is operatively connected to waveguide 119, and the optical phase shifters 122 (forming array 117) are located on / otherwise integrated on waveguide 119. Scatterers are placed at periodic points 112, typically adjacent to waveguide 110. Each scatterer 121 causes a portion of the light field (a and b) from the waveguide to be shifted. (Representing the amplitude and phase of the optical field, respectively) Evanescent coupling 130 (through factor α) and scattering outwards in a plane 140 (through factor γ). Each of the M optical waveguides 119 is configured to receive an optical field with wavelength λ0, which can be approximated using a plane wave. Let represent, where a and These represent the amplitude and phase of the optical field transmitted to each waveguide, respectively. The subscripts m and n represent the array row and column, respectively.

[0027] Figure 3 An embodiment similar to that shown in this specification is illustrated. Figure 2 A schematic diagram, but showing the row of OPAs in the first column (n=1). Each column includes an array 118 of optical phase shifters 123 for shifting the optical phase of the light field in a waveguide 119 connected to waveguide 110, which is perturbed by a plurality of 120s of scatterers 121. Each scatterer 121 perturbs a portion of the light field (a and b) from the waveguide. (These represent the amplitude and phase of the light field, respectively) Evanescent coupling 130 (through factor α) and scattering outwards to plane 140 (through factor γ). Subscripts m and n represent the array row and column, respectively.

[0028] Figure 4 Showing with Figure 3 A similar schematic diagram, but showing the row of OPAs in the last column (n=n). According to this embodiment, each column includes an array 118 of optical phase shifters 123 for shifting the optical phase of the light field in the waveguide 119 connected to the waveguide 110, the optical phase being perturbed by a plurality of 120s of scatterers 121, and also causing a portion of the light field (a and b) from the waveguide 110 to be affected. The amplitude and phase of the light field (representing the amplitude and phase of the light field, respectively) are evanescently coupled 130 (through factor α) and scattered out of plane 140 (through factor γ) by scatterer 121. The subscripts m and n represent the array row and column, respectively.

[0029] Figure 5 The beam steering function of the first paragraph is summarized, and it is shown that, according to one embodiment, the optical phase (a and b) of the light field in waveguide 110 is moved by optical phase shifter 122 via optical phase shifter 122. (representing the amplitude and phase of the light field, respectively) to modulate the x-axis θ on the m-row. x A schematic diagram of the directionality of the upward-scattered beam. This light field will undergo evanescent coupling 130 (through factor α) through scatterer 121 located in column n of the OPA, and will be scattered out onto plane 140 (through factor γ). The subscripts m and n represent the array row and column, respectively. λ eff,fs , and d x These are the effective wavelength of the light field in free space, the optical phase difference of the light field at the scatterer (x direction), and the distance between the scatterers (x direction), respectively. a' is the approximate amplitude of the light field scattered from each scatterer to the outside of the plane.

[0030] The beam directivity (or beam steering angle) θ of the OPA is a function of the emitter spacing d, which acts as the distance 124 between the centers of adjacent scatterers of the emitter, and can be designed according to the following equation: in, λ eff,fs =λ0 / n eff,fs It is the effective wavelength of the light field in free space. λ0 is the wavelength of the light field. n eff,fs It is the effective refractive index of the medium in free space, and It is the optical phase difference of the light field at emitter / scatterer 121.

[0031] Figure 6 The second section summarizes the beam steering function and demonstrates its compatibility with... Figure 5 Similarly, according to one embodiment, an optical phase shifter is used to move the optical phase (a and b) of the light field in the waveguide 119 connected to the waveguide 110 via an array 118 of optical phase shifters 123. (Representing the amplitude and phase of the light field respectively) Modulated on column n=1 along the y-axis θ y A schematic diagram of the directionality of the upward-scattered beam. This light field achieves evanescent coupling 130 through scatterers 121 located in column n of the OPA and is scattered out onto plane 140. The subscripts m and n represent the array row and column, respectively. λ eff,fs , and d y These are the effective wavelength of the light field in free space, the optical phase difference of the light field at the scatterer (y direction), and the distance between the scatterers (y direction), respectively. a' is the approximate amplitude of the light field scattered from each scatterer to the outside of the plane.

[0032] By changing the refractive index of the waveguides in the array, the optical phase of the light field in waveguide 110 of the first segment 117 and the second segment 118 can be altered. This optical phase determines the beam directionality in the x and y directions / dimensions, respectively. Both the first and second optical phase shifters can include phase shifters based on thermo-optic effects, plasmon dispersion effects, electro-optic effects (such as the Pockel effect), evanescent field perturbations regulated by microelectromechanical systems (changing the effective refractive index of the OPA waveguide), or material structure changes (such as liquid crystals, ferroelectrics, and phase change materials). Thermo-optic phase shifters can include metal heaters, alloy heaters, ceramic heaters, and highly doped semiconductor heaters; doped phase shifters based on plasmon dispersion effects can include pn-doped or pin-doped semiconductors; phase shifters based on electro-optic effects can include modulators based on the Pockel effect (such as Li3NbO3 and BaTiO3) or modulators based on the Kerr effect; photonic microelectromechanical system (MEMS) switching phase shifters can include MEMS switches that introduce changes in evanescent field perturbations to alter the effective refractive index of the optical phased array waveguide; phase shifters based on material structure variations can include liquid crystals, ferroelectrics, or phase change materials. Depending on the specific intended function, the phase shifters modifying the waveguide refractive index in the OPA can be the same or different from each other, and the first phase shifter can be the same or different from the second phase shifter. Changes in refractive index can advantageously be induced, for example, by electrically heating the waveguide (via the thermo-optic effect), electrically altering the spatial carrier concentration in the doped semiconductor waveguide (by changing the refractive index and the adsorption of the phase shifter through plasmon dispersion effects), and electrically altering the birefringence of the waveguide (via the electro-optic effect). Changes in thermal and spatial carrier concentration, and optical birefringence in the waveguide can be introduced by applying voltage to a thermo-optical phase shifter (which can be a metal, ceramic / alloy, such as indium tin oxide, or a heavily doped semiconductor heater near the waveguide, using a doped / ion-implanted semiconductor region extending along the waveguide (hereinafter referred to as a doped semiconductor phase shifter)) and an electro-optical phase shifter (formed using a material with a high electro-optic coefficient, such as a material exhibiting the Pockel effect). Metal heaters can be constructed using materials with high thermo-optic coefficients, including but not limited to titanium nitride (TiN) and nickel-chromium (NiCr), while doped semiconductor heaters can include semiconductor materials heavily doped with positively charged (p++) or negatively charged (n++) dopants. For an n++ heater, the doping concentration in the heavily doped heater region may be N. a ~10 20 cm -3 For a p++ heater, the doping concentration in the heavily doped heater region may be N. d ~10 20 cm -3Alternatively, phase shifters based on the plasma dispersion effect can include pn-doped or pin-doped semiconductors. The doping concentration of the doped semiconductor region based on the plasma dispersion effect can be N for the n-doped region. a ~10 17 Up to 10 18 cm -3 For p-doped regions, it can be N d ~10 17 Up to 10 18 cm -3 Doping on waveguides can be achieved using pn junctions or pin junctions to vary the spatial carrier concentration within the waveguide. A pn ​​junction is a junction with regions of positively charged dopant (p-doped regions) injected into the waveguide adjacent to regions of negatively charged dopant (n-doped regions), while a pin junction is a junction with p-doped regions adjacent to undoped regions (or "intrinsic" regions) adjacent to n-doped regions. Electro-optic phase shifters can be constructed using materials with high electro-optic coefficients, such as Li3NbO3 and BaTiO3.

[0033] Figure 7 A schematic top view showing one embodiment of OPA 110, which corresponds to Figure 1The OPA in the second segment has photonic components 117 and 118. Photonic component 117 is used to guide the light beam in the x-direction (due to an optical phase shift applied to the waveguide in the first segment), and photonic component 118 is used to guide the light beam in the y-direction (due to an optical phase shift applied to the optical waveguide 119 in the second segment). Photonic component 117 is shown as an embodiment with a thermo-optical phase shifter 154 (an example of an optical phase shifter 122), which includes a titanium nitride (TiN) thermo-optical heater 134 (on a substrate 141) to modulate the optical phase of the light field in the waveguide 110, which is perturbed by a plurality of scatterers 121 positioned along the waveguide. The waveguide cladding may include a lower cladding 114 and an upper cladding 113. The heater heats the waveguide in the first segment, thereby modulating the refractive index of the waveguide in the first segment to shift the optical phase difference of the light field between the beam emitters in the x-direction, which in turn causes the beam to be redirected along the x-direction. Photonic component 118 is shown as one embodiment with a thermo-optical phase shifter 153 (an example of an optical phase shifter 123), which also includes a titanium nitride (TiN) thermo-optical heater 134 (on substrate 141) for modulating the optical phase of the light field in the first waveguide connected to the second waveguide 110. The heater heats the waveguide in the second segment, thereby modulating the refractive index of the second waveguide to shift the optical phase difference of the light field between the beam emitters in the y-direction, which in turn causes the beam to be redirected along the y-direction. Each thermo-optical heater 134 may be connected to a metal structure (on the bottom layer) and electrically connected to another metal structure (on the top layer) via vias. Preferably, heating of the thermo-optical heaters can be introduced by applying a voltage to electrical pads electrically connected to the metal structures.

[0034] Figure 8 is a schematic top view showing an embodiment of an OPA in an existing solution (e.g., US2002 / 0065997), which corresponds to Figure 1 The OPA in one embodiment, according to one embodiment, has photonic components 117 and 118, photonic component 117 for guiding a light beam in the x-direction (due to an optical phase shift applied to waveguide 110 in the first segment), and photonic component 118 for guiding a light beam in the y-direction (due to an optical phase shift applied to optical waveguide 119 in the second segment). Photonic component 117 is shown to have an optical phase shifter 122 comprising n++ (heavily doped, e.g., acceptor concentration N) a =1×10 20 cm 3 A doped (ion-implanted) thermo-optical heater 137 is used to modulate the optical phase of a light field in waveguide 110, which is perturbed by a plurality of scatterers 121 positioned along the waveguide. Figure 7In contrast to the embodiment in Figure 8, the photonic component 117 is based on a heavily doped phase shifter to generate heat on waveguide 110 for optical phase shifting. The heavily doped phase shifter is typically placed on the side of waveguide 110, thus significantly increasing the spacing of waveguide 110, which results in a reduced field of view / beam steering range in the y-direction (as described in Equation 1), which is undesirable. Adjacent heavily doped regions cannot be placed together, as this would cause short circuits between the doped regions. The waveguide cladding may include a lower cladding 114 and an upper cladding 113. A heater heats the waveguide 110 in the first segment, thereby modulating the refractive index of the waveguide 110 in the first segment to shift the optical phase difference of the light field between the beam emitters in the x-direction, which in turn causes the beam to be steered along the x-direction. Photonic component 118 is shown as having an optical phase shifter 123 comprising a pn junction (a p-doped region labeled 135 and an n-doped region labeled 136) on waveguide 119 to modulate the optical phase of the light field in waveguide 119. A voltage applied across the pn junction forming optical phase shifter 122 introduces a plasmonic dispersion effect in the waveguide 119 in a second segment, thereby modulating the refractive index of waveguide 119 to shift the optical phase difference of the light field between beam emitters in the y-direction, which in turn causes the beam to be redirected in the y-direction. Doped semiconductor structures 135, 136, and 137 can be connected to a metal structure (on the bottom layer) and electrically connected to another metal structure (on the top layer) via vias. Preferably, the plasmonic dispersion effect can be introduced from the doped semiconductor waveguide structures 135 and 136 by applying a voltage to pads electrically connected to the metal structures. Similarly, heating of the thermo-optical heater can be introduced from the heavily doped semiconductor structure 137 by applying a voltage to pads electrically connected to the metal structures.

[0035] Phase shifter 122 does not need to extend along the entire length of waveguide 110 in the first segment, and phase shifter 123 does not need to extend along the entire length of waveguide 119 in the second segment. The desired optical phase shift can be modified by changing the portion of the segment to which the phase shifter extends, thereby creating an optical phase shift region in each segment.

[0036] Figure 9 This shows different optical phase shifters according to several preferred embodiments of the optical phase shifter (a highly doped semiconductor thermo-optical phase shifter 152 located on the side of the first waveguide 110 (as described in US2022 / 0065997), a pn-doped semiconductor phase shifter 151 in the second segment, and metal thermo-optical phase shifters (154 and 153, respectively) in the first and second segments, corresponding to... Figure 7A table of partially equidistant schematic diagrams (and the optical phase shifters shown in Figure 8). For example, according to one embodiment of the OPA, the OPA 100 may include rows (M) of metal thermo-optical phase shifters 154 adjacent to or otherwise integrated with a waveguide 119 based on total internal reflection formed of Si3N4 in a first segment, and separate rows (M) of metal thermo-optical phase shifters 153 adjacent to or otherwise integrated with a waveguide 110 and a scatterer 121 based on total internal reflection formed of Si3N4 in a second segment. According to another embodiment of the OPA, the OPA 100 may include a first row (M) of pn-doped optical phase shifters in the first segment and separate second rows (M) of doped semiconductor thermo-optical phase shifters 151 in the second segment. Optionally, for example, the number of rows (M) and columns (N) of the OPA 100 may be between 2 and 10,000. The OPA 100, which includes optical phase shifters (117 and 118), may also include any of several different types of optical phase shifters suitable for, for example, LiDAR systems or free-space transceivers (metal thermo-optical phase shifters, pn-doped optical phase shifters, pin-doped optical phase shifters, doped semiconductor thermo-optical phase shifters, and thermo-optical effect-based optical phase shifters).

[0037] The optical phase shift caused by optical phase shifters used for beam steering varies depending on design parameters. For thermo-optical phase shifters, the optical phase shift depends on the temperature coefficient of the waveguide material. And the length of the heated waveguide region L. The induced optical phase shift can be conveniently described as the increase in waveguide temperature ΔT and the effective wavelength of the optical field λ in the waveguide. eff,wg Functions: For example, in order to use ΔT = 50K (or 50℃), in the parameter and λ eff,wg With a diameter of ≈1 μm, a 2π phase shift is induced, and the estimated length of the thermo-optical phase shifter is L≈60 μm. For doped semiconductor optical phase shifters based on the plasma dispersion effect, the optical phase shift depends on the doping concentration on the waveguide forming the phase shifter. Figure 10 This specification shows a phase shift generated using the Silvaco simulation software tool according to an embodiment of the OPA. And a simulated diagram of an example doping effect relative to the voltage decay applied to a 6 mm long pn-doped optical phase shifter. In the simulated example, on a 0.22 μm high optical waveguide, the acceptor N a and donor N d Doping concentration of N a =N d =3×10 18 cm 3The optical waveguide section is etched with a slab height of 90 nm. Simulation results show that the designed structure can advantageously achieve an optical phase modulation efficiency of 1.494 V·cm.

[0038] Figure 11 This shows the different waveguide refractive indices n wg ( Figure 11 The electric field z-component (E) obtained by finite-difference time-domain (FDTD) numerical simulation of the photonic component at d = 0.78 μm along the xz cross section in the five examples of the model (3.48, 3.75, 4.0, 4.25, and 4.5). z ) distribution. According to Equation 1, especially for θ (or θ) in the x-direction. x The direction specified in the subscript can be used to determine when... When, that is, when d = λ eff,wg When, where λ eff,wg =λ0 / n eff,wg It is the effective wavelength of the optical field in the waveguide (in this example, λ). eff (0.78μm), and n eff,wg λ is the effective refractive index of the waveguide medium, and the scattered (or emitted) light field propagates in free space in a direction perfectly perpendicular to the waveguide structure. Changing λ... eff,wg / d and / or This causes the beam directionality to shift from the vertical direction (z-axis). For example, according to one embodiment using a 1.55 μm wavelength as the light field, the scatterer is formed of Si with a diameter of approximately 160 nm, the waveguide supports a transverse magneto-optical waveguide mode with a width of 0.7 μm, a sidewall thickness or height of 0.22 μm, partially etched with a 90 nm slat height, and an air upper cladding and a SiO2 lower cladding. Preferably, in one embodiment, an optical phase shifter 122 may be located on or otherwise integrated into each waveguide 110 perturbed by the plurality of emitters / scatterers 121 to achieve simultaneous optical phase shifting of the entire row of scatterers, thereby directing the beam in the x-direction.

[0039] Figure 12 It is sent to the waveguide Different optical phase differences in the input light field (i.e., optical phase in the y-direction) A comparative schematic diagram of polar coordinates of the far-field intensity relative to the azimuth angle and zenith angle is shown below. This input optical field can be modulated using a phase shifter located on or otherwise integrated into the OPA waveguide. This paper discusses different... ( Figure 12The six examples in the model are disclosed at 150°, 90°, 30°, -30°, -90°, and -150°. According to one embodiment, a 1.55 μm wavelength is used as the optical field, with each waveguide row spaced 0.9 μm apart. The scatterer is formed of Si with a diameter of approximately 160 nm. The waveguide supports a lateral magneto-optical waveguide mode, has a width of 0.7 μm, a sidewall thickness or height of 0.22 μm, is partially etched with a 90 nm board height, and has an air upper cladding and a SiO2 lower cladding. In one embodiment, an optical phase shifter 123 may be located on or otherwise integrated into each waveguide connected to waveguide 110 for beam steering in the y-direction. Preferably, when this configuration is combined with a separate configuration using another optical phase shifter 122 located on or otherwise integrated into each waveguide 110 (which is perturbed by multiple emitters / scatterers 121 for beam steering in the x-direction), the total number of optical phase shifters for 2D beam steering scales linearly (i.e., the total number of optical phase shifters is linearly proportional to the number of rows in the OPA array). For example, if there are 5 rows in the optical phased array, the total number of phase shifters can be 2 × 5 = 10 (as the minimum number of phase shifters). There can also be 3 × 5 = 15 phase shifters, or 4 × 5 = 20 phase shifters, etc.

[0040] As will be apparent from the foregoing disclosure and detailed description of certain embodiments, various modifications, additions, and other alternative embodiments can be made without departing from the true scope and spirit of the invention. The embodiments discussed were chosen and described to provide the best illustration of the principles of the invention and its practical application, thereby enabling those skilled in the art to use the invention in various embodiments and make various modifications to suit a particular intended use. All such modifications and variations are within the scope of the invention as defined by the appended claims when interpreted according to their fair, legal, and just enjoyment.

Claims

1. An optical phased array for two-dimensional beam steering, comprising: At least one optical waveguide having a refractive index, each optical waveguide having multiple scatterers; A first segment located at a first optical waveguide of the at least one optical waveguide, wherein the first segment is adapted to guide the beam in the x direction, and the first segment includes at least one first optical phase shifter located below or above the first optical waveguide and the plurality of scatterers; A second segment located at a second optical waveguide of the at least one optical waveguide, wherein the second segment is adapted to guide the beam in a direction different from that of the first segment, and the second segment includes at least one second optical phase shifter longitudinally located below the second optical waveguide; and A waveguide cladding surrounding the first and second optical waveguides, the waveguide cladding including an upper cladding and a lower cladding, the first and second optical waveguides being connected in series and arranged within the upper cladding; and the first optical waveguide being connected to the second optical waveguide along its length, such that the optical phased array is configured to guide the light beam through the second optical waveguide to the first optical waveguide.

2. The optical phased array of claim 1, wherein, The at least one first optical phase shifter is different from the at least one second optical phase shifter.

3. The optical phased array according to claim 1, further comprising at least one electrical connection between the at least one first optical phase shifter in the first segment and the at least one second optical phase shifter in the second segment.

4. The optical phased array according to claim 1, wherein, Each of the at least one first optical phase shifter and the at least one second optical phase shifter alters the refractive index of the at least one optical waveguide based on one of the following: thermo-optical effect, plasma dispersion effect, electro-optical effect, photonic microelectromechanical system switching, or material structure change.

5. The optical phased array according to claim 4, wherein, The thermo-optical phase shifter based on the aforementioned thermo-optical effect includes one of a metal heater, an alloy heater, a ceramic heater, and a highly doped semiconductor heater; The doped phase shifter based on the plasma dispersion effect includes one of pn-doped semiconductor and pin-doped semiconductor; The phase shifter based on the electro-optic effect includes one of a modulator based on the Pockel effect and a modulator based on the Kerr effect; The phase shifter based on the aforementioned photonic microelectromechanical system (MEMS) switching includes a MEMS switch that introduces a change in the evanescent field perturbation to alter the refractive index of the at least one optical waveguide; and Phase shifters based on the aforementioned material structure changes include one of liquid crystal, ferroelectric, and phase change materials.

6. The optical phased array according to claim 1, comprising a first row of the first segment and a second row of the second segment, wherein, The at least one first optical phase shifter in the first segment is operatively connected to the at least one second optical phase shifter in the second segment.

7. The optical phased array according to claim 1, wherein, The at least one optical waveguide includes a plurality of waveguides, the at least one first optical phase shifter includes a plurality of first optical phase shifters, and the at least one second optical phase shifter includes a plurality of second optical phase shifters; as well as Each first optical phase shifter includes a first layer located below or above each corresponding waveguide, and each second optical phase shifter includes a second layer located below each corresponding waveguide.

8. The optical phased array according to claim 1, wherein, The at least one optical waveguide and each corresponding scatterer independently comprise at least one or more of Si, SiO2, Si3N4, BaTiO3, Li3NbO3, InP, polymers, III-V compounds other than InP, and II-VI compounds.

9. The optical phased array according to claim 1, wherein, The at least one optical waveguide and each corresponding scatterer are independently doped with p-type or n-type material.

10. The optical phased array according to claim 1, wherein, Each of the plurality of scatterers includes one of a Mie scatterer and a Rayleigh scatterer.

11. The optical phased array according to claim 1, wherein, Each of the plurality of scatterers is embedded in the corresponding at least one optical waveguide.

12. The optical phased array according to claim 1, wherein, Each of the plurality of scatterers is in contact with the top or sidewall of the corresponding at least one optical waveguide.

13. The optical phased array according to claim 1, wherein, Each of the at least one optical waveguide is one of a total internal reflection waveguide and an in-plane scattering waveguide.

14. The optical phased array according to claim 1, wherein, Each of the at least one optical waveguide is a rectangular waveguide having an elongated top surface and sidewalls extending from the top surface.

15. The optical phased array of claim 1, further comprising a controller adapted to calculate information about an object based on the beam.

16. The optical phased array according to claim 1, wherein, The number of optical phase shifters is linearly proportional to the number of rows.

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