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 waveguide having a plurality of scatterers. A first segment of the optical waveguide is adapted to guide a light beam in an x-direction, and the first segment includes a first optical phase shifter. A second segment of the optical waveguide is adapted to guide the light beam in a different direction than the first segment, and the second segment includes a second optical phase shifter.

Description

Technical Field

[0001] The present invention relates to light beam steering, and more particularly, to an optical phased array that uses a light field of a fixed light wavelength to steer a light beam in different dimensions and directions. Background Art

[0002] Recent advances in silicon photonics have led to the development of nanophotonic optical phased arrays (OPAs). An OPA antenna is a photonic component that is able to change the direction of the lobe of an emitted light beam in real time. This ability to dynamically and precisely change the direction of an emitted light beam is extremely useful for directing a beam carrying an information signal to a specific target and / or receiver in applications such as light detection and ranging (LiDAR) systems and free-space transceivers.

[0003] OPA beam steering has traditionally relied on photonic components consisting of movable mirrors controlled using hydraulic pumps and micro-electromechanical systems. Further miniaturization efforts have resulted in beam steering components based on the structural properties of materials (such as liquid crystals, ferroelectrics, and phase-change materials) or on the modulation of optical properties (such as refractive index and wavelength of light).

[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 optical phase shifters and tunable light sources to change the optical phase difference of the light field at the beam emitter; by inducing a refractive index shift of the optical waveguide in the OPA, and by inducing a wavelength shift of the light field sent to the optical waveguide in the OPA, respectively. To achieve two-dimensional (2D) beam steering, an optical phase shifter is usually used to steer the beam in one dimension, and an tunable light source is used to steer the beam in another dimension. However, beam steering using wavelength shifting poses the following problems: i. Laser gain media that allow large wavelength shifts are uncommon; ii. In LiDAR systems, the properties of objects to be detected and the ranging distance vary with wavelength; iii. In free-space transceivers, beam steering using wavelength makes it infeasible to use unique wavelengths for different data streams; iv. It can be challenging to find other photonic components (such as waveguides and photodetectors) in the beam control system that support a similarly wide wavelength range as in the beam control platform; v. It can be complicated to continuously adjust the optical power of the light field emitted by the beam control platform to offset the solar irradiance variations of ambient light of different wavelengths in free space (with which the platform's light field must compete). Therefore, it is important to have a system that can steer beams in different directions and dimensions using a light field of fixed wavelength.

[0005] Although 2D beam steering using purely optical phase shifters can be implemented on conventional beam steering platforms using beam steering with fixed optical wavelengths, the number of optical phase shifters is usually nonlinearly related to the number of emitters in an array row. Therefore, the following problems arise: i. The management of the beam control system may be cumbersome; ii. The platform will occupy a large amount of space for the required optical phase shifters; iii. The energy efficiency of the beam steering platform is low due to the large number of optical phase shifters.

[0006] It is desirable to provide an improved photonic component capable of directing a light beam into different directions and dimensions using a light field of a fixed light wavelength (coherent light) through 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 steering of an optical beam is provided, comprising optical waveguides, each waveguide having a plurality of scatterers. A first segment of the optical waveguide is adapted to guide the optical beam in an x-direction, and the first segment comprises a first optical phase shifter. A second segment of the optical waveguide is adapted to guide the optical beam in a direction different from the first segment (e.g., in a y-direction), and the second segment comprises a second optical phase shifter.

[0008] From the foregoing disclosure and the following more detailed description of various embodiments, it will be apparent to those skilled in the art that the present invention provides a significant advancement in OPA technology. Of particular importance in this regard is that the present invention provides the potential to provide an OPA with 2D beam steering using a number of optical phase shifters that scale linearly with the number of rows in the OPA array. Additional features and advantages of the various embodiments will be better understood in light of the detailed description provided below. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 A schematic diagram of using optical phase shifters to guide a light beam using a fixed wavelength of light in two directions or dimensions (2D) by modulating the optical phase of the light field in a waveguide along rows and columns of an OPA in accordance with certain embodiments of the present specification is shown.

[0010] Figure 2 A schematic diagram of using optical phase shifters to modulate the optical phase of a light field in a waveguide along a column of OPAs is shown according to certain embodiments of the present specification.

[0011] Figure 3 A schematic diagram of using optical phase shifters to modulate the optical phase of a light field in a waveguide along a row of OPAs is shown according to certain embodiments of the present specification.

[0012] Figure 4A schematic diagram showing the use of an optical phase shifter in the last column to modulate the optical phase of a light field in a waveguide along a row of OPAs according to certain embodiments of the present specification.

[0013] Figure 5 The use of an optical phase shifter to modulate an out-of-plane light field scattered by a scatterer located at column n of an OPA is shown in accordance with certain embodiments of the present specification. The optical phase of row m in turn modulates the scattered beam θ on the x-axis. x Schematic diagram of the directionality.

[0014] Figure 6 The invention shows the use of an optical phase shifter to modulate the light field scattered out of the plane by a scatterer located at row m of an optical phased array according to some embodiments of the present specification. This in turn modulates the optical phase of the beam θ scattered out of plane on the y-axis of column n = 1 y Schematic diagram of the directionality.

[0015] Figure 7 A schematic diagram of using a metallic thermo-optical phase shifter to guide a light beam in the x and y dimensions is shown according to some embodiments of the present description.

[0016] Figure 8 Schematic diagrams showing the use of an optical phase shifter in the form of a highly doped semiconductor thermo-optical heater to guide a light beam in the x-dimension and the use of a modulator based on the pn junction plasma dispersion effect to guide a light beam in the y-dimension, both using a fixed wavelength of light, according to certain embodiments of the present specification.

[0017] Fig. 9 The optical phase shifter ( Fig. 9 The four embodiments of the model are partially isometric schematic diagrams of a phase shifter based on the pn junction plasma dispersion effect, a highly doped semiconductor thermo-optical phase shifter, and a metal thermo-optical phase shifter.

[0018] Fig.10 shows the resulting phase shift of one embodiment of an OPA according to the present specification and example doping effect simulation plots with respect to the voltage decay applied to a 6 mm long pn-doped optical phase shifter.

[0019] Fig.11 An estimated z component of the electric field of a photonic component is shown at different refractive indices of a waveguide forming part of an OPA, which component can be modulated using a phase shifter located on or otherwise integrated into the waveguide on the OPA, according to several embodiments of the present specification.

[0020] Fig.12is sent to the waveguide The light field at different optical phase differences (i.e. the phase difference in the y dimension) Schematic diagram of the comparison of polar coordinate plots of the far-field intensity generated by the input light field, which can be modulated using a phase shifter located on the OPA or otherwise integrated into the waveguide of the OPA.

[0021] It should be understood that the drawings are not necessarily drawn to scale, but rather present somewhat simplified representations of various features that illustrate the basic principles of the invention. The specific design features of the OPA disclosed herein, including, for example, the specific dimensions of the scatterers / emitters, will be determined to a certain extent by the specific intended application and use environment. Certain features of the illustrated embodiments are enlarged or distorted relative to other features to help provide a clear understanding. In particular, for example, thin features may be thickened for clarity of illustration. Unless otherwise specified, all references to dimensions, directions, and positions refer to the directions shown in the drawings. DETAILED DESCRIPTION

[0022] It will be apparent to those skilled in the art, i.e., those with knowledge or experience in this area of ​​technology, that the optical phased array disclosed herein has many 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 scales linearly with the number of rows of a plurality of optical phased arrays. This is in contrast to conventional OPAs for 2D beam steering that operate using a fixed wavelength of light, which use a number of optical phase shifters that scales nonlinearly with the number of rows in the OPA array. The OPA disclosed herein can be used as a beam control system, for example, which can be part of a LiDAR system or a free-space transceiver; and can be used as a transmitter and a receiver. Other embodiments suitable for other applications will be apparent to those skilled in the art, given the benefit of this disclosure.

[0023] Figure 1A schematic diagram of an optical phased array (OPA) 100 is shown, according to certain embodiments of the present specification, illustrating the use of optical phase shifters to achieve 2D beam steering of a light field using a fixed wavelength of light by modulating the optical phase of the light field in a series of one or more waveguides along the rows (M) and columns (N) of the OPA. The OPA includes an array of operably connected photonic components formed in rows and columns, having a first section of optical phase shifters 117 generally adjacent to (below, above, on one side or the other side of) or otherwise integrated (or embedded) therein the waveguides 100 and scatterers 121 (which may include a series of rows and columns of the array), and a second section of optical phase shifters 118 adjacent to or otherwise integrated with waveguides 119 (which may include another series of rows or columns of the array), wherein the waveguides 119 are operably connected to the first section. The first segment is capable of controlling a light beam in the x dimension and includes at least one first optical phase shifter 122 (forming an array 117) which is typically adjacent to or otherwise integrated into at least one (M≥1) waveguide 110 and includes a plurality (N) of optical nanostructures (also referred to as scatterers or emitters) 121 positioned at periodic points 112 in the segment along each waveguide. The second segment is capable of controlling a light beam in a dimension different from x, typically the y dimension (i.e., 90° in azimuth to the x dimension). The second segment includes at least one second optical phase shifter 123 (forming an array 118) which is adjacent to or otherwise integrated into at least one waveguide 119 which is operably connected to the waveguide 110 in the first segment. Each phase shifter 122 forming part of the array 117 modulates the optical phase of the light field in the optical waveguide 110, while each phase shifter 123 forming part of the array 118 modulates the optical phase of the light field of the optical waveguide 119 connected to the optical waveguide 110. The OPA can be scaled up to have an arbitrary number of M×N optical waveguides and scatterers. Each of the m optical waveguides 119 is configured to receive a 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 shifters, 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 (the first layer is used for the first optical phase shifter and the second layer is used 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). In addition, the first optical phase shifter may include a different material from the second optical phase shifter. Both the first optical phase shifter and the second optical phase shifter may be adjacent to or integrated in the corresponding waveguide.

[0024] Preferably, such photonic components in the OPA can be fully implemented on a chip using standard manufacturing techniques (such as lithography and deposition) and standard photonic materials (for example, 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-wave in the infrared region of the electromagnetic spectrum, for example, 1.4μm to 1.7μm. Depending on the application of the photonic component, visible light wavelengths (0.38μm to 0.75μm) and near-infrared wavelengths (0.75μm to 1.4μm) 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. Additionally, in a LiDAR system, the controller may be adapted to work with a scatterer 121 and an array (117 and 118) of optical phase shifters (122 and 123) adjacent to or otherwise integrated into at least one waveguide (110 and 119), and receive an emitted light field reflected from the object, and in conjunction with the processor calculate information about surface properties of the object based on the reflected light received from the scatterer and the waveguide.

[0025] The waveguides (110 and 119) can be circular or rectangular (rib or ridge) waveguides having an elongated top surface and sidewalls extending from the top surface. The refractive index of the waveguide core can be greater than the refractive index of the surrounding waveguide cladding. The waveguide cladding can include a lower cladding and an upper cladding. The waveguide can include any of several different types of waveguides. For example, the waveguide can be a waveguide based on total internal reflection (which constitutes the vast majority of optical waveguides traditionally used in integrated photonics), a slot waveguide, and a surface plasmon waveguide. Alternatively, in-plane scattering waveguides can be used, such as waveguides formed by photonic crystals (also using total internal reflection) and metamaterials. The composition of each of the multiple waveguides can be, for example, at least one of 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. The waveguide can support any optical waveguide mode, for example, a transverse electric mode and a transverse magnetic mode. The scatterer / emitter 121 may be a Mie scatterer or a Rayleigh scatterer. More specifically, Mie scattering mainly refers to the scattering of a light field from a scatterer whose diameter, width or diagonal is usually 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 of the wavelength of the incident light 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 also be doped with a positively charged dopant (p-type material) or a negatively charged dopant (n-type material). Types of positively charged dopants include, for example, boron, gallium and aluminum; and types of negatively charged dopants include, for example, arsenic, phosphorus and antimony. Each of the multiple scatterers may be embedded in a corresponding waveguide, and / or each of the multiple scatterers may be in contact with the top wall or side wall of the corresponding waveguide.

[0026] Figure 2 A schematic diagram of a column (N) of OPAs on the mth row in accordance with an embodiment of the present invention is shown. Each row includes an optical phase shifter 122 for shifting the optical phase of a light field in a waveguide 110 that is perturbed by a plurality 120 of scatterers 121. The waveguide 110 is operably connected to a waveguide 119 on which the optical phase shifters 122 (forming an array 117) are located / otherwise integrated. The scatterers are placed at periodic points 112 that are generally adjacent to the waveguide 110. Each scatterer 121 causes a portion of the light field (a and b) from the waveguide to be shifted. , respectively, represent the amplitude and phase of the light field) evanescently coupled 130 (by factor α), and scattered out of the plane 140 (by factor γ). Each of the M optical waveguides 119 is configured to receive a light field with a wavelength of λ0, which can be approximated using a plane wave To represent, where a and denote the amplitude and phase of the optical field sent to each waveguide, respectively. The subscripts m and n denote the array row and column, respectively.

[0027] Figure 3 shows a similar embodiment according to the present specification Figure 2 Schematic diagram of the invention, but showing rows of OPAs on 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 the waveguide 110, which is perturbed by a plurality 120 of scatterers 121. Each scatterer 121 causes a portion of the light field (a and b) from the waveguide to denote the amplitude and phase of the light field, respectively) evanescently coupled 130 (by factor α) and scattered out of the plane 140 (by factor γ). The subscripts m and n denote the array rows and columns, respectively.

[0028] Figure 4 Shows the Figure 3 A similar schematic diagram, but showing the rows of OPAs on 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 optical field in the waveguide 119 connected to the waveguide 110, which is perturbed by the plurality 120 of scatterers 121 and also causes a portion of the optical field (a and b) from the waveguide 110 to be shifted. denoting the amplitude and phase of the light field, respectively) are evanescently coupled 130 (by factor α) and are scattered out of plane 140 (by factor γ) by scatterer 121. The subscripts m and n denote array rows and columns, respectively.

[0029] Figure 5 The beam steering function of the first paragraph is summarized and the optical phase shifter is used to shift the optical phase (a and b) of the light field in the waveguide 110 by the optical phase shifter 122 according to one embodiment. Representing the amplitude and phase of the light field respectively) to modulate the x-axis θ on m lines x Schematic diagram of the directionality of a scattered beam on an OPA. The light field will be evanescently coupled 130 through a scatterer 121 located in column n of the OPA (by factor α) and scattered out of the plane 140 (by factor γ). The subscripts m and n refer to the array row and column, respectively. eff,fs , and d x are the effective wavelength of the light field in free space, the optical phase difference of the light field at the scatterer (in the x direction), and the scatterer spacing (in the x direction). a' is the approximate amplitude of the light field scattered out of the plane from each scatterer.

[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 between the centers of adjacent scatterers of the emitter 124 and can be designed according to the following equation: in, λ eff,fs =λ0 / n eff,fs is the effective wavelength of the light field in free space, λ0 is the wavelength of the light field, n eff,fs is the effective refractive index of the medium in free space, and is the optical phase difference of the light field at the emitter / scatterer 121.

[0031] Figure 6 The beam steering function of the second paragraph is summarized and the Figure 5 Similarly, according to one embodiment, an optical phase shifter is used to shift the optical phase (a and b) of the light field in the waveguide 119 connected to the waveguide 110 by an array 118 of optical phase shifters 123. Represents the amplitude and phase of the light field) modulated on the y-axis θ on n = 1 column y Schematic diagram of the directionality of the scattered light beam on the OPA. The light field is evanescently coupled 130 through the scatterer 121 located in column n of the OPA and scattered out of the plane 140. The subscripts m and n represent the array row and column, respectively. eff,fs , and d y are the effective wavelength of the light field in free space, the optical phase difference of the light field at the scatterer (in the y direction), and the scatterer spacing (in the y direction). a' is the approximate amplitude of the light field scattered out of the plane from each scatterer.

[0032] By changing the refractive index of the waveguides in the array, the optical phase of the light field in the waveguide 110 in the first section 117 and the second section 118 can be changed, which determines the directionality of the light beam in the x and y directions / dimensions, respectively. The first optical phase shifter and the second optical phase shifter can both include phase shifters based on thermo-optical effects, plasma dispersion effects, electro-optical effects (such as the Pockel effect), micro-electromechanically regulated evanescent field perturbations (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 may include metal heaters, alloy heaters, ceramic heaters, and highly doped semiconductor heaters; doped phase shifters based on plasma dispersion effects may include pn-doped or pin-doped semiconductors; phase shifters based on electro-optic effects may include modulators based on the Pockel effect (such as Li3NbO3 and BaTiO3) or modulators based on the Kerr effect; photonic micro-electromechanical system switching phase shifters may include micro-electromechanical system switches that introduce changes in evanescent field perturbations to change the effective refractive index of the optical phased array waveguide; phase shifters based on material structure changes may include liquid crystals, ferroelectrics, or phase change materials. Depending on the needs of the specific intended function, the phase shifters that modify the refractive index of the waveguide in the OPA may be the same or different from each other, and the first phase shifter may be the same or different from the second phase shifter. The change in refractive index can be advantageously induced by, for example, electrically heating the waveguide (via the thermo-optic effect), electrically changing the spatial carrier concentration in the doped semiconductor waveguide (changing the refractive index and adsorption of the phase shifter through the plasma dispersion effect), and electrically changing the birefringence of the waveguide (via the electro-optic effect). Thermal, spatial carrier concentration variations and optical birefringence variations in the waveguide can be introduced by applying voltages to a thermo-optic phase shifter (which can be a metal, ceramic / alloy such as indium tin oxide, or a heavily doped semiconductor heater near the waveguide by 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 that exhibits the Pockel effect). The metal heater can be constructed using materials with high thermo-optic coefficients, including but not limited to titanium nitride (TiN), nickel chromium (NiCr), and the doped semiconductor heater can include a semiconductor material heavily doped with positively charged (p++) or negatively charged (n++) dopants. For an n++ heater, the doping concentration of the heavily doped heater region may be N a ~10 20 cm -3 For a p++ heater, the doping concentration of the heavily doped heater region may be N d ~10 20 cm -3Alternatively, the phase shifter based on plasma dispersion effect may include a pn-doped or pin-doped semiconductor. The doping concentration of the doped semiconductor region based on plasma dispersion effect may 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 a waveguide can be formed using either a pn junction or a pin junction to achieve a spatial carrier concentration variation in the waveguide. A pn ​​junction is a junction that has a region of positively charged dopants injected into the waveguide (p-doped region) adjacent to a region of negatively charged dopants injected into the waveguide (n-doped region), while a pin junction is a junction that has a p-doped region adjacent to an undoped region (or "intrinsic" region) adjacent to an n-doped region. Phase shifters based on the electro-optic effect can be constructed using materials with high electro-optic coefficients, such as Li3NbO3 and BaTiO3.

[0033] Figure 7 A schematic top view of an embodiment of an OPA 110 is shown, which corresponds to Figure 11, an OPA having photonic components 117 and 118, the photonic component 117 being used to steer a light beam in the x-direction (due to an optical phase shift applied to a waveguide in a first segment), and the photonic component 118 being used to steer a light beam in the y-direction (due to an optical phase shift applied to an optical waveguide 119 in a second segment). The photonic component 117 is shown as having one embodiment of a thermo-optical phase shifter 154 (one example of an optical phase shifter 122) that includes a titanium nitride (TiN) thermo-optical heater 134 (on a substrate 141) to modulate the optical phase of a light field in a waveguide 110 that 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 light beam emitters in the x-direction, which in turn steers the light beam along the x-direction. The photonic assembly 118 is shown with one embodiment of a thermo-optical phase shifter 153 (an example of an optical phase shifter 123) that 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 segment connected to the second waveguide segment 110. The heater heats the waveguide in the second segment, thereby modulating the refractive index of the second waveguide segment to shift the optical phase difference of the light field between the light beam emitters in the y-direction, which in turn steers the light beam along the y-direction. Each thermo-optical heater 134 can be connected to a metal structure (on the bottom layer) and electrically connected to another metal structure (on the top layer) through a via. Preferably, heating of the thermo-optical heater can be introduced by applying a voltage to an electrical pad electrically connected to the metal structure.

[0034] Figure 8 is a schematic top view showing another embodiment of an OPA, which also corresponds to Figure 1 1 , which also has photonic components 117 and 118, according to one embodiment, with photonic component 117 being used to guide the optical beam in the x direction (due to the optical phase shift applied to the waveguide 110 in the first section) and photonic component 118 being used to guide the optical beam in the y direction (due to the optical phase shift applied to the optical waveguide 119 in the second section). Photonic component 117 is shown as having an optical phase shifter 122, which includes n++ (heavy doping, such as an acceptor concentration N a =1×10 20 cm 3) doped (ion implanted) thermo-optical heater 137 for modulating 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 110 in the first section, thereby modulating the refractive index of the waveguide 110 in the first section to shift the optical phase difference of the light field between the light beam emitters in the x-direction, which in turn steers the light beam along the x-direction. The photonic assembly 118 is shown having an optical phase shifter 123 including a pn junction (a p-doped region labeled 135 and an n-doped region labeled 136) on the waveguide 119 to modulate the optical phase of the light field in the waveguide 119. The voltage applied across the pn junction forming the optical phase shifter 122 introduces a plasma dispersion effect in the waveguide 119 in the second section, thereby modulating the refractive index of the waveguide 119 to shift the optical phase difference of the light field between the light beam emitters in the y direction, which in turn steers the light beam in the y direction. The 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) through electrical vias. Preferably, the plasma dispersion effect can be introduced from the doped semiconductor waveguide structures 135 and 136 by applying a voltage to the electrical pads electrically connected to the metal structures. Similarly, heating from the thermo-optical heater can be introduced from the heavily doped semiconductor structure 137 by applying a voltage to the electrical pads 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 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] Fig. 9 is a diagram showing different optical phase shifters according to several preferred embodiments of the optical phase shifter (in Fig. 9 In the four examples of the model, the highly doped semiconductor thermo-optic phase shifter 152 in the first segment, the pn-doped semiconductor phase shifter 151 in the second segment, and the metal thermo-optic phase shifters in the first and second segments (154 and 153, respectively) correspond to Figure 7 and Figure 81 . For example, according to one embodiment of the OPA, the OPA 100 may include rows (M) of metallic thermo-optical phase shifters 154 adjacent to or otherwise integrated with a total internal reflection-based waveguide 119 formed of Si3N4 in a first section, and rows (M) of separate metallic thermo-optical phase shifters 153 adjacent to or otherwise integrated with a total internal reflectivity-based waveguide 110 and a scatterer 121 formed of Si3N4 in a second section. According to another embodiment of the OPA, the OPA 100 may include a first row (M) of pn-doped optical phase shifters 152 in a first section, and a separate second row (M) of doped semiconductor thermo-optical phase shifters 151 in a second section. Optionally, for example, the number of rows (M) and the number of columns (N) of the OPA 100 may be between 2 and 10,000. The OPA 100 including optical phase shifters (117 and 118) may in turn include any of several different types of optical phase shifters (metallic thermo-optic phase shifters, pn-doped optical phase shifters, pin-doped optical phase shifters, doped semiconductor thermo-optic phase shifters, optical phase shifters based on thermo-optic effect) suitable for use in, for example, LiDAR systems or free-space transceivers.

[0037] The optical phase shift induced by an optical phase shifter used for beam steering varies depending on the design parameters. For a thermo-optical phase shifter, 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 waveguide temperature increase ΔT and the effective wavelength λ of the light field in the waveguide eff,wg Function: For example, to use ΔT = 50K (or 50°C), in the parameter and λ eff,wg The estimated length of the thermo-optical phase shifter is L≈60μm. 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. Fig.10 The phase shift produced using the Silvaco simulation software tool for one embodiment of an OPA according to the present specification is shown in FIG. and an example simulation of the doping effect with respect to the voltage decay applied to a 6 mm long pn-doped optical phase shifter. In the simulation example, on a 0.22 μm high optical waveguide, the acceptor N a and donor N d The doping concentration is N a =N d =3×10 18 cm 3The optical waveguide is partially 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] Fig.11 It shows the refractive index of the waveguide at different wg ( Fig.11 The electric field z component (E) of the photonic component along the xz cross section at d = 0.78 μm obtained by numerical simulation of the finite-difference time-domain method (FDTD) for 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 x ; direction specified in the subscript), it can be determined when When d = λ eff,wg When λ eff,wg =λ0 / n eff,wg is the effective wavelength of the light field in the waveguide (in this example, λ eff 0.78 μm), and n eff,wg is the effective refractive index of the waveguide medium. The scattered (or emitted) light field propagates in the free space in a direction completely perpendicular to the waveguide structure. eff,wg / d and / or This will cause the beam directivity 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 scatterers are formed of Si, have a diameter of approximately 160 nm, and 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, a partially etched slab height of 90 nm, and an air upper cladding and a SiO2 lower cladding. Preferably, in one embodiment, an optical phase shifter 122 may be located or otherwise integrated into each waveguide 110 perturbed by multiple emitters / scatterers 121 to achieve simultaneous optical phase shifting of the entire row of scatterers, thereby performing beam steering in the x-direction.

[0039] Fig.12 is sent to the waveguide The different optical phase differences of the input light field (i.e., the optical phase in the y direction) ) with respect to the azimuth and zenith viewing angles. The input light field can be modulated using a phase shifter located on or otherwise integrated into the OPA waveguide. ( Fig.12The six examples in the model are 150°, 90°, 30°, -30°, -90°, and -150°). According to one embodiment, a wavelength of 1.55 μm is used as the light field, each row of waveguides is spaced 0.9 μm apart, the scatterer is formed of Si with a diameter of about 160 nm, the waveguide supports a transverse 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 plate height of 90 nm, and has an upper cladding of air and a lower cladding of SiO2. In one embodiment, an optical phase shifter 123 can be located or otherwise integrated into each waveguide connected to the 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 used for 2D beam steering scales linearly (i.e., the total number of optical phase shifters is linearly proportional to the number of OPA array rows). For example, if there are 5 rows in the optical phased array, the total number of phase shifters can be 2×5=10 phase shifters (as the minimum number of phase shifters). There can also be 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 certain embodiments that various modifications, additions and other alternative embodiments may be made without departing from the true scope and spirit of the invention. The embodiments discussed have been selected and described in order to provide the best illustration of the principles of the invention and its practical application, thereby enabling one of ordinary skill in the art to use the invention in various embodiments and with various modifications to suit the particular use 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 equitably entitled.

Claims

1. An optical phased array for two-dimensional light beam steering, comprising: at least one optical waveguide having a refractive index, each optical waveguide having a plurality of scatterers; a first segment at the at least one optical waveguide, wherein the first segment is adapted to guide the optical beam in an x-direction and the first segment comprises at least one first optical phase shifter; and A second segment located at the at least one optical waveguide, wherein the second segment is adapted to direct the optical beam in a different direction than the first segment, and the second segment comprises at least one second optical phase shifter.

2. The optical phased array according to 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 of 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 changes the refractive index of the at least one optical waveguide based on one of a thermo-optic effect, a plasma dispersion effect, an electro-optic effect, a photonic micro-electromechanical system switching, or a material structure change.

5. The optical phased array according to claim 4, wherein: The thermo-optic phase shifter includes one of a metal heater, an alloy heater, a ceramic heater, and a highly doped semiconductor heater; The doping based on the plasma dispersion effect includes one of a pn-doped semiconductor and a pin-doped semiconductor; The modulator 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 photonic MEMS switch comprises a MEMS switch that introduces a change in an evanescent field perturbation to change the refractive index of the at least one optical waveguide; and The material structure change includes one of liquid crystal, ferroelectric and phase change material.

6. The optical phased array of 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 operably 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 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; as well as Each first optical phase shifter includes a first layer adjacent to each corresponding waveguide, and each second optical phase shifter includes a second layer adjacent to each corresponding waveguide.

8. The optical phased array according to claim 1, wherein: The at least one optical waveguide and each corresponding scatterer independently include at least one or more of Si, SiO2, Si3N4, BaTiO3, Li3NbO3, InP, a polymer, a III-V compound, and a II-VI compound.

9. The optical phased array according to claim 1, wherein: The at least one optical waveguide and each of the respective scatterers are independently doped with a 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 a corresponding one of the 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 a top wall or a side wall 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 based 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 side walls 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 light beam.

16. The optical phased array of claim 1 having a plurality of rows, wherein: The number of optical phase shifters scales linearly with the number of rows.

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