Optical Phased Array with Linearly Scalable Phase Shifters for 2D Beam Steering

Abstract

An optical phased array for 2D steering of an optical beam includes optical waveguides, each waveguide having a plurality of scatterers, a first segment of the optical waveguide configured to steer the optical beam in an x-direction, the first segment including a first optical phase shifter, and a second segment of the optical waveguide configured to steer the optical beam in a direction different from the first segment, the second segment including a second optical phase shifter.

Description

[Technical Field]

[0001] The present invention relates to optical beam steering, and more particularly to optical phased arrays that steer optical beams in different dimensions and directions using optical fields of a fixed optical wavelength. [Background technology]

[0002] Recent advances in silicon photonics have led to the development of nanophotonic optical phased arrays (OPAs). OPA antennas are photonic components that can change the direction of the lobes of an emitted beam in real time. This ability to dynamically and precisely shift the direction of an emitted beam is useful for directing beams carrying information signals to specific targets and / or receivers in applications such as light detection and ranging (LiDAR) systems and free-space transmitters and receivers.

[0003] Beam steering from OPAs has traditionally utilized photonic components incorporating movable mirrors controlled using hydraulic pumps and microelectromechanical systems. Further miniaturization efforts have resulted in beam steering components that modulate based on the structural properties of materials, such as liquid crystals, ferroelectrics, and phase-change materials, or based on optical properties such as refractive index or light wavelength.

[0004] Among various beam steering techniques, optical modulation is particularly suitable for on-chip beam steering. This can be achieved by shifting the optical phase difference of the optical field at the beam emitter by inducing a refractive index shift in the optical waveguide within the OPA using an optical phase shifter and a tunable light source, respectively, and by inducing an optical wavelength shift in the optical field sent to the optical waveguide within the OPA. To enable two-dimensional (2D) beam steering, it is customary to steer the optical beam in one dimension using an optical phase shifter and in the other dimension using a tunable light source. However, using optical wavelength shifting for beam steering presents the following problems: i. It is not common to have a lasing gain medium that allows for a large shift in optical wavelength. ii. In LiDAR systems, the nature of the object being detected and the ranging distance can vary with wavelength. iii. In free-space transceivers, using optical wavelength for beam steering makes it impossible to use unique optical wavelengths for different data streams. iv. It may be difficult to find other photonic components (such as waveguides and photodetectors) in a beam steering system that can accommodate a wavelength range as wide as the beam steering platform. v. It may be complicated to continuously adjust the optical power of the optical field emitted from the beam steering platform to offset variations in ambient solar irradiance in free space at different wavelengths, with which the optical field from the platform must compete. Thus, it is important to have a system that allows for the manipulation of optical beams in different directions and dimensions using an optical field of a fixed optical wavelength.

[0005] While 2D beam steering using purely optical phase shifters can be achieved with conventional beam steering platforms for beam steering using a fixed optical wavelength, the number of optical phase shifters typically scales nonlinearly with the number of emitters in an array row. This results in the following problems: i. Managing the beam steering system can be time-consuming; ii. The platform occupies a large footprint due to the large number of optical phase shifters required; and iii. The large number of optical phase shifters makes the beam steering platform energy inefficient. Summary of the Invention [Problem to be solved by the invention]

[0006] It is desirable to provide an improved photonic component that enables manipulation of light beams in different directions and dimensions using an optical field (coherent light) of a fixed optical wavelength via optical phase shifters, where the number of optical phase shifters scales linearly with the number of rows in the OPA array. [Means for solving the problem]

[0007] According to a first aspect, an optical phased array for 2D steering of an optical beam includes optical waveguides, each waveguide having a plurality of scatterers. A first segment of the optical waveguide is configured to steer the optical beam in an x-direction, the first segment including a first optical phase shifter. A second segment of the optical waveguide is configured to steer the optical beam in a different direction than the first segment (e.g., in the y-direction), the second segment including a second optical phase shifter.

[0008] It will be apparent to those skilled in the art from the foregoing disclosure and the following detailed description of various embodiments that the present invention represents a significant advance in the art of OPAs. Of particular importance in this regard is the potential ability the present invention offers to provide an OPA with 2D beam steering using optical phase shifters that scale linearly with the number of rows in the OPA array. Further features and advantages of various embodiments will be better understood in light of the detailed description provided below. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 10 is a schematic diagram illustrating the use of an optical phase shifter to manipulate an optical beam in two directions or dimensions (2D) using a fixed optical wavelength by modulating the optical phase of an optical field within a waveguide along the rows and columns of an OPA according to certain embodiments disclosed herein.

[0010] [Figure 2] 1 is a schematic diagram illustrating the use of an optical phase shifter to modulate the optical phase of an optical field within a waveguide along an array of OPAs according to certain embodiments disclosed herein.

[0011] [Figure 3] 1 is a schematic diagram illustrating the use of an optical phase shifter to modulate the optical phase of an optical field within a waveguide along a row of an OPA according to certain embodiments disclosed herein.

[0012] [Figure 4] In the last column, a schematic diagram illustrating the use of an optical phase shifter to modulate the optical phase of an optical field within a waveguide along a row of an OPA according to certain embodiments disclosed herein.

[0013] [Figure 5] FIG. 1C is a schematic diagram illustrating the use of an optical phase shifter to modulate the optical phase of the light field φ scattered out-of-plane by scatterers arranged in column n of an OPA, thereby modulating the directionality θ of the scattered light beam in the x-axis at row m, according to certain embodiments disclosed herein.

[0014] [Figure 6] FIG. 1C is a schematic diagram illustrating the use of an optical phase shifter to modulate the optical phase of an optical field φ scattered out-of-plane by a scatterer arranged in row m of an optical phased array, thereby modulating the directionality θ of the out-of-plane scattered optical beam in the y-axis at column n=1, in accordance with certain embodiments disclosed herein.

[0015] [Figure 7] 1 is a table showing a schematic diagram illustrating the use of a metallic thermo-optic optical phase shifter to manipulate a light beam in both the x and y dimensions, in accordance with certain embodiments disclosed herein.

[0016] [Figure 8] 1 is a table showing a schematic diagram illustrating the use of an optical phase shifter in the form of a highly doped semiconductor thermo-optical heater to steer a light beam in the x-dimension and a modulator based on the plasma dispersion effect of a pn junction to steer a light beam in the y-dimension, both using a fixed light wavelength, according to certain embodiments disclosed herein.

[0017] [Figure 9] 10 is a table showing partial isometric schematic diagrams of optical phase shifters (phase shifter based on plasma dispersion effect of pn junction, highly doped semiconductor thermo-optic phase shifter, and metallic thermo-optic phase shifter in four examples of the model in FIG. 9 ) according to certain preferred embodiments disclosed herein.

[0018] [Figure 10] FIG. 10 shows a simulation plot of an exemplary doping effect of the resulting phase shift Δφ and attenuation with respect to the voltage applied to a 6 mm long pn-doped optical phase shifter according to one embodiment of the OPA disclosed herein.

[0019] [Figure 11]1 is a table showing the resulting estimated z-component of the electric field in accordance with some embodiments of the photonic component disclosed herein at different refractive indices of a waveguide forming part of the OPA, where the refractive index can be modulated using a phase shifter disposed in or otherwise integrated with the waveguide of the OPA.

[0020] [Figure 12] 10 is a table comparing polar plots of the far-field intensity obtained with different optical phase differences Δφy (i.e., phase differences Δφ in the y-direction) of the optical field sent to the waveguide, which can be modulated using a phase shifter located or otherwise integrated into the waveguide of the OPA. DETAILED DESCRIPTION OF THE INVENTION

[0021] It should be understood that the accompanying drawings are not necessarily to scale, and that they present somewhat simplified representations of various features illustrating the underlying principles of the present invention. Specific design features of the OPAs disclosed herein, including, for example, specific dimensions of the scatterers / emitters, 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 clear understanding. In particular, thin features may be thickened, for example, for clarity of illustration. Unless otherwise specified, all dimensional, directional, and positional references are with respect to the orientation shown in the drawings.

[0022] Those skilled in the art, i.e., those with knowledge or experience in this field of technology, will recognize that the optical phased arrays disclosed herein are susceptible to numerous uses and design variations. In the detailed description of various alternative features and embodiments below, the general principles of the present invention are explained with reference to an optical phase assembly for 2D beam steering using phase shifters that scale linearly with the number of rows in the optical phase array. This contrasts with conventional OPAs for 2D beam steering, which operate using a fixed optical wavelength and use optical phase shifters that scale nonlinearly with the number of rows in the OPA array. The OPAs disclosed herein may be used as beam steering systems that may be part of a LiDAR system or a free-space transceiver, e.g., they may be used as both a transmitter and a receiver. Given the benefit of this disclosure, other embodiments suitable for other applications will be apparent to those skilled in the art.

[0023] 1 shows a schematic diagram of an optical phased array (OPA) 100 illustrating the use of optical phase shifters to achieve 2D beam steering using an optical field of a fixed optical wavelength by modulating the optical phase of the optical field within a series of one or more waveguides along the rows (M) and columns (N) of the OPA according to certain embodiments disclosed herein. The OPA comprises an array of operatively connected photonic components formed in rows and columns, the array comprising a first segment 117 of optical phase shifters positioned generally adjacent to (below, above, to one side, or the other of) or otherwise integrated (or embedded) with the waveguides 100 and scatterers 121 (which may comprise a series of rows and columns of the array), and a second segment 118 of optical phase shifters positioned adjacent to or otherwise integrated with a waveguide 119 (which may comprise another series of rows and columns of the array) operatively connected to the first segment. The first segment enables steering of the optical beam in the x-dimension and comprises at least one first optical phase shifter 122 (forming an array 117) disposed generally adjacent to or otherwise integrated with at least one (M≧1) waveguide 110 and a plurality (N) 120 optical nanostructures (also referred to as scatterers or emitters) 121 disposed along each waveguide at periodic points 112 in the segment. The second segment enables steering of the optical beam in a dimension different from the x-dimension, typically the y-dimension (i.e., 90° azimuthally from the x-dimension), and comprises at least one second optical phase shifter 123 (forming an array 118) disposed adjacent to or otherwise integrated with at least one waveguide 119 operatively connected to the waveguides 110 of the first segment. Each phase shifter 122 forming part of array 117 modulates the optical phase of the optical field within optical waveguide 110, and each phase shifter 123 forming part of array 118 modulates the optical phase of the optical field in an optical waveguide 119 connected to optical waveguide 110. The OPA is scalable to have any number M×N of optical waveguides and scatterers. Each m of the M optical waveguides 119 is configured to receive the optical field propagating to m of the M optical waveguides 110. The subscripts m and n refer to the rows and columns of the array, respectively.In a preferred embodiment, each row can include the same type of optical phase shifter, and the second segment can have only one row of optical phase shifters. Optionally, each optical phase shifter can be formed as a different layer (a first layer corresponding to the first optical phase shifter and a second layer corresponding to the second optical phase shifter, the first layer adjacent to each corresponding waveguide, and the second layer adjacent to each corresponding waveguide). Also, the first optical phase shifter can include a different material than the second optical phase shifter. Both the first optical phase shifter and the second optical phase shifter can be located adjacent to or integrated with the corresponding waveguide.

[0024] Advantageously, such photonic components of this OPA can be implemented entirely on a chip using standard fabrication techniques, such as lithography and evaporation, and standard photonic materials, 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 optical field can be in the short-wavelength infrared region of the electromagnetic spectrum, for example, between 1.4 μm and 1.7 μm. Visible wavelengths (0.38 μm to 0.75 μm) and near-infrared wavelengths (0.75 μm to 1.4 μm) may also be used, depending on the application of the photonic components. One or more electrical connections may be provided between the first optical phase shifter of the first segment and the second optical phase shifter of the second segment. Further, in the LiDAR system, the controller may be configured to cooperate with an array (117 and 118) of optical phase shifters (122 and 123) positioned adjacent to or otherwise integrated with at least one waveguide (110 and 119) and scatterer 121 to receive the reflected and emitted light fields from the object, and may include a processor for calculating information regarding the surface characteristics of the object based on the reflected light received by the scatterers and waveguides.

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

[0026] 2 shows a schematic diagram of a column (N) of an OPA with m rows, according to one embodiment of the present invention. Each row includes an optical phase shifter 122 that shifts the optical phase of the optical field in a waveguide 110, as perturbed by a plurality 120 of scatterers 121. The waveguide 110 is operatively connected to a waveguide 119 in which / otherwise integrated are disposed the optical phase shifters 122 (forming an array 117). The scatterers are disposed at periodic points 112 generally adjacent to the waveguide 110. Each scatterer 121 shifts a portion (α and φ) of the optical field from the waveguide. in,m represent the amplitude and phase of the optical field, respectively), are evanescently coupled 130 (with rate α) and scattered out-of-plane 140 (with rate γ). Each m of the M optical waveguides 119 is iφ in,m and α and φ in,m represent the amplitude and phase, respectively, of the optical field sent to each waveguide. The subscripts m and n again represent the rows and columns of the array, respectively.

[0027] 3 shows a schematic diagram similar to FIG. 2, but illustrating the first (n=1) column of rows of an OPA according to one embodiment of the present invention. Each column comprises an array 118 of optical phase shifters 123 that shift the optical phase of the optical field in a waveguide 119 connected to the waveguide 110, as perturbed by a plurality 120 of scatterers 121. Each scatterer 121 shifts a portion (α and φ) of the optical field from the waveguide. in,m denote the amplitude and phase of the optical field, respectively), are evanescently coupled 130 (with rate α) and scattered out-of-plane 140 (with rate γ). The subscripts m and n again denote the rows and columns of the array, respectively.

[0028] 4 shows a similar schematic diagram to FIG. 3, but showing the last (n=N) columns of rows of OPAs. Each column comprises an array 118 of optical phase shifters 123 that shift the optical phase of the optical field in a waveguide 119 connected to the waveguide 110, which is perturbed by a plurality 120 of scatterers 121, again resulting in a portion (α and φ) of the optical field from the waveguide 110 being shifted, according to one embodiment. in,mdenote the amplitude and phase of the optical field, respectively), is evanescently coupled 130 (with rate α) and scattered out-of-plane 140 (with rate γ) by the scatterer 121. The subscripts m and n again denote the rows and columns of the array, respectively.

[0029] FIG. 5 summarizes the beam steering function of the first segment, according to one embodiment, which shifts the optical phase of the optical field (α and φ) within the waveguide 110 via the optical phase shifter 122. in,m denote the amplitude and phase of the optical field, respectively), and the directionality θ of the scattered light beam in the x-axis at row m is determined by evanescent coupling 130 (with rate α) and out-of-plane scattering 140 (with rate γ) by scatterers 121 arranged in column n of the OPA. x 1 shows a schematic diagram illustrating the use of optical phase shifters to modulate λ. The subscripts m and n represent the rows and columns of the array, respectively. eff,fs , Δφ x , and d x are the effective wavelength of the optical field in free space, the optical phase difference of the optical field in the scatterers (x direction), and the scatterer pitch (x direction), respectively. α' is the approximate amplitude of the optical field scattered out-of-plane from each scatterer.

[0030] The beam directionality (or beam steering angle) θ of an OPA, which is a function of the emitter pitch d, i.e., the distance 124 between the centers of adjacent scatterers that act as emitters, can be designed based on the following equation:

number

[0031] FIG. 6 summarizes the beam steering function of the second segment, according to one embodiment, showing a schematic diagram similar to FIG. 5, but shifting the optical phase of the optical field (α and φ) in waveguide 119 connected to waveguide 110 via an array 118 of optical phase shifters 123. in,m and represent the amplitude and phase of the optical field, respectively), and the directionality θ of the scattered light beam in the y-axis at row n=1 is determined by evanescent coupling 130 and out-of-plane scattering 140 using scatterers 121 arranged in column n of the OPA. y The subscripts m and n represent the rows and columns of the array, respectively. eff,fs , Δφ y , and d y are the effective wavelength of the optical field in free space, the optical phase difference of the optical field in the scatterers (y direction), and the scatterer pitch (y direction), respectively. α' is the approximate amplitude of the optical field scattered out-of-plane from each scatterer.

[0032] The optical phase of the optical field within the waveguides 110 of the first segment 117 and the second segment 118 (determining the beam directionality in the x-direction / dimension and the y-direction / dimension, respectively) can be varied by changing the refractive index of the waveguides in the array. Both the first and second optical phase shifters can include phase shifters based on either the thermo-optic effect, the plasma dispersion effect, the electro-optic effect (such as the Pockels effect), microelectromechanically tuned evanescent field perturbation (which changes the effective refractive index of the OPA waveguide), or structural changes in materials (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 the plasma dispersion effect can include pn-doped or pn-doped semiconductors; electro-optic phase shifters can include Pockels-effect modulators such as Li3NbO3 and BaTiO3, or Kerr-effect modulators; photonic microelectromechanical system switching phase shifters can include microelectromechanical system switches that produce variations in evanescent field perturbations to change the effective refractive index of optical phased array waveguides; and phase shifters based on structural changes in materials can include liquid crystals, ferroelectrics, or phase-change materials. Phase shifters that change the refractive index of waveguides within an OPA can be the same or different from each other, as needed for the specific intended function, and a first phase shifter can be the same or different from a second phase shifter. The refractive index change can be advantageously induced, for example, by electrically heating the waveguide (via the thermo-optic effect), electrically varying the spatial carrier concentration in a doped semiconductor waveguide (altering the refractive index and adsorption of the phase shifter via the plasma dispersion effect), and electrically varying the birefringence of the waveguide (via the electro-optic effect).Heat, spatial carrier concentration changes, and optical birefringence changes within the waveguide can be induced by applying a voltage to a thermo-optic phase shifter (a metal, ceramic / alloy phase shifter such as indium tin oxide, or a heavily doped semiconductor heater (hereafter referred to as a doped semiconductor phase shifter) near the waveguide, using a doped / ion-implanted semiconductor region extending along the waveguide), and by applying a voltage to an electro-optic phase shifter (formed using a material with a high electro-optic coefficient, such as one exhibiting the Pockels effect). Metal heaters can be constructed using materials with a high thermo-optic coefficient, including, but not limited to, titanium nitride (TiN) and nickel chromium (NiCr), and doped semiconductor heaters can include semiconductor materials heavily doped with positively charged (p++) or negatively charged (n++) dopants. The doping concentration of the heavily doped heater region is approximately 10 for n++ heaters. 20 cm -3 N a , and about 10 for p++ heaters 20 cm -3 N d Alternatively, the phase shifter based on the plasma dispersion effect may include either a pn-doped semiconductor or a p-i-n-doped semiconductor. The doping concentration of the doped semiconductor region based on the plasma dispersion effect may be about 10 for the n-doped region. 17 ~10 18 cm -3 N a , about 10 in the p-doped region 17 ~10 18 cm -3 N d Doping of the waveguide to allow for spatial carrier concentration variations within the waveguide may be formed using pn junctions or pin junctions. A pn junction is a junction with a region where a positively charged dopant has been implanted into the waveguide (p-doped region) next to a region where a negatively charged dopant has been implanted into the waveguide (n-doped region), and a pin junction is a junction with a p-doped region next to an undoped region (or "intrinsic" region) adjacent to an n-doped region. Phase shifters based on the electro-optic effect may be constructed using materials with high electro-optic coefficients, such as Li3NbO3 and BaTiO3.

[0033] 7 is a diagram illustrating a schematic top view of one embodiment of an OPA 110 corresponding to that of FIG. 1 , the OPA having a photonic component 117 for steering an optical beam in the x-direction (by an optical phase shift applied to a first segment of the waveguide) and a photonic component 118 for steering an optical beam in the y-direction (by an optical phase shift applied to a second segment of the waveguide 119). Photonic component 117 is shown along with an embodiment of a thermo-optic phase shifter 154 (an example of an optical phase shifter 122) comprising a titanium nitride (TiN) thermo-optic heater 134 (on a substrate 141) for modulating the optical phase of an optical field in waveguide 110 perturbed by a plurality of scatterers 121 disposed along the waveguide. The waveguide cladding can comprise a lower cladding 114 and an upper cladding 113. The heater heats the waveguide of the first segment, thereby modulating the refractive index of the waveguide of the first segment to shift the optical phase difference of the optical field between the beam emitters in the x-direction, which then steers the optical beam along the x-direction. Photonic component 118 is shown with one embodiment of thermo-optic phase shifter 153 (an example of optical phase shifter 123), also comprising a titanium nitride (TiN) thermo-optic heater 134 (on substrate 141) for modulating the optical phase of the optical field in the waveguide of the first segment, which is connected to waveguide 110 of the second segment. The heater heats the waveguide of the second segment, thereby modulating the refractive index of the waveguide of the second segment to shift the optical phase difference of the optical field between the beam emitters in the y-direction, which then steers the optical beam along the y-direction. Each thermo-optic heater 134 may be connected to a metal structure (on the bottom layer) that is electrically connected to another metal structure (on the top layer) through an electrical via. Advantageously, heating of the thermo-optic heater can be induced by applying a voltage to an electrical pad electrically connected to the metal structure.

[0034] 8 is a table showing a schematic top view of another embodiment of an OPA, also corresponding to that of FIG. 1, again including a photonic component 117 for steering the optical beam in the x-direction (by an optical phase shift applied to the waveguide 110 of the first segment) and a photonic component 118 for steering the optical beam in the y-direction (by an optical phase shift applied to the waveguide 119 of the second segment), according to one embodiment. Photonic component 117 includes n++ (e.g., acceptor concentration Na=1×10) scatterers for modulating the optical phase of the optical field in waveguide 110 perturbed by a plurality of scatterers 121 disposed along the waveguide. 20 cm 3 The photonic component 118 is shown with an optical phase shifter 122 comprising a doped (ion-implanted) thermo-optic heater 137 (heavily doped with ZnO). The waveguide cladding can comprise a lower cladding 114 and an upper cladding 113. The heater heats the first segment waveguide 110, thereby modulating the refractive index of the first segment waveguide 110 and shifting the optical phase difference of the optical field between the beam emitter in the x-direction, which in turn steers the optical beam along the x-direction. The photonic component 118 is shown with an optical phase shifter 123 comprising a p-n junction (a p-doped region 135 and an n-doped region 136) on the waveguide 119 for modulating the optical phase of the optical field in the waveguide 119. A voltage applied across the pn junction forming the optical phase shifter 122 induces a plasma dispersion effect in the second segment waveguide 119, thereby modulating the refractive index of the waveguide 119 and shifting the optical phase difference of the beam-emitter optical field in the y-direction, which in turn steers the optical beam along the y-direction. The doped semiconductor structures 135, 136, and 137 may be connected to a metal structure (on the bottom layer) electrically connected to another metal structure (on the top layer) through electrical vias. Advantageously, the plasma dispersion effect can be induced from the doped semiconductor waveguide structures 135 and 136 by applying a voltage to an electrical pad electrically connected to the metal structure. Similarly, heating of the thermo-optical heater can be induced from the heavily doped semiconductor structure 137 by applying a voltage to an electrical pad electrically connected to the metal structure.

[0035] Phase shifter 122 need not extend along the entire length of waveguide 110 in the first segment, and phase shifter 123 need not extend along the entire length of waveguide 119 in the second segment. The required optical phase shift may be varied by having the phase shifters extend through different portions of the segments, creating an optical phase shift region in each segment.

[0036] FIG. 9 is a table showing partial isometric schematic diagrams of different optical phase shifters (heavily doped semiconductor thermo-optic phase shifter 152 in the first segment, pn-doped semiconductor phase shifter 151 in the second segment, and metallic thermo-optic phase shifters (154 and 153, respectively) in the first and second segments, corresponding to the optical phase shifters depicted in FIGS. 7 and 8 in the four examples of the model in FIG. 9 ) according to some preferred embodiments of the optical phase shifter. For example, according to one embodiment of the OPA, the OPA 100 may comprise a row (M) of metallic thermo-optic optical phase shifters 154 in the first segment that are positioned adjacent to or otherwise integrated with the total internal reflection-based waveguide 119 formed from Si3N4, and another row (M) of metallic thermo-optic optical phase shifters 153 in the second segment that are positioned adjacent to or otherwise integrated with the total internal reflection-based waveguide 110 formed from Si3N4 and the scatterer 121. According to another embodiment of the OPA, the OPA 100 can include a first row (M) of pn-doped optical phase shifters 152 in a first segment and another second row (M) of doped semiconductor thermo-optic optical phase shifters 151 in a second segment. Optionally, the number of rows (M) and columns (N) of the OPA 100 can range, for example, from 2 to 10,000. The OPA 100 includes optical phase shifters (117 and 118), which can include any of several different types of optical phase shifters (metal thermo-optic optical phase shifters, pn-doped optical phase shifters, pn-doped optical phase shifters, doped semiconductor thermo-optic optical phase shifters, and optical phase shifters based on the thermo-optic effect) configured for use, for example, in a LiDAR system or a free-space transceiver.

[0037] The optical phase shift induced by an optical phase shifter due to beam steering varies depending on the design parameters. In the case of a thermo-optic phase shifter, the optical phase shift depends on the temperature coefficient dn / dT of the waveguide material and the length L of the heated waveguide region. The induced optical phase shift scales with the increase in waveguide temperature ΔT and the effective wavelength λ of the optical field within the waveguide. eff,wg can be conveniently expressed as a function of

number

[0038] Figure 11 shows the different waveguide refractive indices n wg The electric field (E) of the embodiment of the photonic component at d=0.78 μm along the xz cross section revealed (3.48, 3.75, 4.0, 4.25 and 4.5 for the five examples of the model in FIG. 11). Z1 is a table showing the results of numerical simulations in the finite-difference time-domain (FDTD) of the z-component of the θ (or θ ) profile. x ; the direction is specified in the subscript), when Δφ=0, that is, d=λ eff,wg (where λ eff,wg =λ0 / n eff,wg is the effective wavelength of the optical field in the waveguide (in our case, λ eff,wg = 0.78 μm), and n eff,wg is the effective refractive index of the waveguide medium), the scattered (radiated) optical field can be determined to propagate in free space in a direction exactly perpendicular to the waveguide structure. eff,wg Varying / d and / or Δφ shifts the beam directionality from the normal to the vertical direction (in the z-axis). For example, according to one embodiment using a 1.55 μm wavelength as the optical field, scatterers formed from Si can have a diameter of approximately 160 nm, and the waveguide can support a transverse magneto-optical waveguide mode with a width of 0.7 μm and a sidewall thickness or height of 0.22 μm, partially etched with an air upper cladding and a SiO2 lower cladding at a slab height of 90 nm. Advantageously, in one embodiment, one optical phase shifter 122 can be located or otherwise integrated into each waveguide 110 perturbed by multiple emitter / scatterers 121, enabling simultaneous optical phase shifting for an entire row of scatterers for beam steering in the x-direction.

[0039] Figure 12 shows the different Δφ y (150°, 90°, 30°, −30°, −90°, −150° in the six example models of FIG. 12 ) and different optical phase differences Δφ of the input optical field sent to the waveguide, which can be modulated using phase shifters located or otherwise integrated into the waveguide of the OPAs disclosed herein. y1 is a table comparing polar plots of the resulting far-field intensity with respect to azimuthal and zenithal viewing angles (i.e., optical phase Δφ in the y-direction). According to one embodiment using a wavelength of 1.55 μm as the optical field, each row of waveguides is spaced 0.9 μm apart, the scatterers formed from Si have a diameter of approximately 160 nm, and the waveguides are partially etched with an air upper cladding and a SiO lower cladding at a 90 nm slab height, with a width of 0.7 μm and a sidewall thickness or height of 0.22 μm, to accommodate a transverse magneto-optical waveguide mode. In one embodiment, one optical phase shifter 123 can be disposed in or otherwise integrated into each waveguide connected to the waveguide 110 for beam steering in the y-direction. Advantageously, when this configuration is combined with another configuration using one other optical phase shifter 122 located or otherwise integrated into each waveguide 110 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 the optical phase array has five rows, the total number of phase shifters could be 2 × 5 = 10 phase shifters (minimum number of phase shifters), 3 × 5 = 15 phase shifters, or 4 × 5 = 20 phase shifters, etc.

[0040] 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 described embodiments were chosen and described to provide the best explanation of the principles of the invention and its practical application, and to thereby enable those skilled in the art to use the invention in various embodiments and with various modifications suited to the particular uses contemplated. 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 to which they are fairly, legally, and duly entitled.

Claims

1. 1. An optical phased array for 2D steering of a light beam, comprising: at least one optical waveguide having a refractive index, each waveguide having a plurality of scatterers; a first segment of the at least one optical waveguide, the first segment configured to steer the light beam in an x-direction, the first segment comprising at least one first optical phase shifter; a second segment of the at least one optical waveguide, the second segment configured to steer the light beam in a different direction than the first segment, the second segment comprising at least one second optical phase shifter; An optical phased array that combines these.

2. 10. 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. 10. The optical phased array of claim 1, further comprising: at least one electrical connection between the at least one first optical phase shifter of the first segment and the at least one second optical phase shifter of the second segment.

4. 10. The optical phased array of claim 1, wherein each of the at least one first optical phase shifter and the at least one second optical phase shifter changes the refractive index of the waveguide based on one of a thermo-optic effect, a plasma dispersion effect, an electro-optic effect, photonic microelectromechanical system switching, or a structural change of a material.

5. the thermo-optic phase shifter includes one of a metal heater, an alloy heater, a ceramic heater, and a highly doped semiconductor heater; the doped based on the plasma dispersion effect comprises one of a pn-doped semiconductor and a pin-doped semiconductor; the one based on the electro-optic effect includes one of a modulator based on the Pockels effect and a modulator based on the Kerr effect; the photonic microelectromechanical system switching comprises one of a microelectromechanical system switch that produces a variation in an evanescent field perturbation to change the refractive index of the waveguide; 5. The optical phased array of claim 4, wherein the structural change of material comprises one of a liquid crystal, a ferroelectric, and a phase change material.

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

7. the at least one waveguide comprises a plurality of waveguides, the at least one first optical phase shifter comprises a plurality of first optical phase shifters, and the at least one second optical phase shifter comprises a plurality of second optical phase shifters; 2. The optical phased array of claim 1, wherein each first optical phase shifter comprises a first layer adjacent to each of the corresponding waveguides, and wherein each second optical phase shifter comprises a second layer adjacent to each of the corresponding waveguides.

8. The at least one waveguide and the corresponding scatterer are each made of Si, SiO ２ , Si ３ N ４ , BaTiO ３ , Li ３ NbO ３ , InP, a polymer, a III-V compound, and a II-VI compound.

9. 2. The optical phased array of claim 1, wherein each of the at least one waveguide and corresponding scatterer is independently doped with a p-type material or an n-type material.

10. The optical phased array of claim 1 , wherein each of the plurality of scatterers comprises one of a Mie scatterer and a Rayleigh scatterer.

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

12. The optical phased array of claim 1 , wherein each of the plurality of scatterers contacts a top wall or a side wall of a corresponding at least one waveguide.

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

14. 10. The optical phased array of claim 1, wherein each of the at least one 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 configured to calculate information about an object based on the light beam.

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

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