Optical phased arrays and methods for correcting their phase

Abstract

An optical phased array is provided, comprising: a light injector; a first splitter connected to the light injector; a first phase shifter connected to the first splitter; a plurality of waveguides connected to the first splitter, and portions of the plurality of waveguides being connected to the first splitter via the first phase shifter; an antenna array connected to the plurality of waveguides; a single-mode filter disposed in each of the plurality of waveguides; and a first photodetector connected to the first splitter and configured to detect a portion of light radiated onto the antenna array.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to Korean Patent Application No. 10-2019-0106132, filed on August 28, 2019, with the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] The exemplary embodiments of this disclosure relate to optical phased arrays, and more specifically, to optical phased arrays including components for correcting phase errors generated during manufacturing, and methods for performing phase correction using the optical phased array. Background Technology

[0004] A phased array consists of multiple components that emit phased electromagnetic waves. A phased array is a device that can induce destructive and constructive interference phenomena by appropriately controlling the phase difference between its components to control the radiation angle of the electromagnetic waves in a desired direction.

[0005] An optical phased array (OPA) is a phased array that operates relative to short wavelengths of electromagnetic waves, typically a few micrometers (μm) or smaller (i.e., relative to optical signals). OPAs can control the radiation angle of optical signals using only electrical signals, without mechanical movement, thus enabling high-speed and highly reliable beam steering. OPAs can also be used in autonomous driving optical detection and ranging (LiDAR).

[0006] OPAs can be formed in several ways. For example, an OPA can be formed by using semiconductor processes to form the components constituting the OPA on a silicon or silicon oxide (SiO2) substrate. The components can be formed in an integrated form. An OPA formed in this way is called an OPA chip.

[0007] An OPA (Optical Point Amplifier) ​​comprises a light source, and the light is split into N channels by a beam splitter. The light source can be embedded within the OPA chip or input externally via optical fiber, etc. Each separate channel consists of a phase shifter and an antenna. The phase shifter provides a different phase difference to each of the N channels. The optical signals with different phases in each channel are interfered with by the antenna array, thus becoming a single beam with directionality. The direction in which the beam is emitted can vary depending on the phase difference conditions between the channels. Summary of the Invention

[0008] One or more example embodiments provide an OPA that can perform OPA phase correction relatively simply.

[0009] One or more example embodiments also provide an OPA that can perform OPA phase correction relatively quickly.

[0010] One or more example embodiments also provide an OPA that can increase the reliability of OPA phase correction.

[0011] One or more example embodiments also provide a method for performing OPA phase correction quickly and reliably using OPA.

[0012] Additional aspects will be set forth in part in the description which follows, and will also be apparent in part from the description itself, or may be learned by practice of exemplary embodiments.

[0013] According to one aspect of an example embodiment, an optical phased array (OPA) is provided, comprising: a light injector; a first splitter connected to the light injector; a first phase shifter connected to the first splitter; a plurality of waveguides connected to the first splitter, portions of the plurality of waveguides being connected to the first splitter via the first phase shifter; an antenna array connected to the plurality of waveguides; a single-mode filter disposed in each of the plurality of waveguides; and a first photodetector connected to the first splitter and configured to detect a portion of light radiated onto the antenna array.

[0014] The OPA may also include: multiple splitters disposed between the first splitter and multiple waveguides; and multiple photodetectors connected to the multiple splitters.

[0015] OPA may also include multiple phase shifters positioned between multiple separators.

[0016] Regarding the OPA, a waveguide and a first photodetector can be connected to a first side of a first splitter for light entry and exit, two waveguides are connected to a second side of the first splitter and branch off from the first splitter, and a first phase shifter is disposed on one of the two waveguides.

[0017] Regarding the OPA, a waveguide and a photodetector can be connected to the first side of each of a plurality of splitters through which light enters and exits, and two waveguides are connected to the second side of each of the plurality of splitters and branch off from each of the plurality of splitters.

[0018] The first photodetector may include a first optical receiving element and a second optical receiving element respectively disposed on both sides of the waveguide.

[0019] The photodetector connected to the first side of each of the multiple splitters may include a first optical receiving element and a second optical receiving element disposed on both sides of a waveguide.

[0020] Multiple photodetectors can be positioned to receive light that deflects off the waveguides as light radiated onto the antenna array passes through multiple waveguides and splitters.

[0021] A single-mode filter can be integrated into each of multiple waveguides.

[0022] A single-mode filter may include: a first portion having a first width; a second portion having a second width; and a third portion having a third width; wherein the first width, the second width, and the third width are different from each other.

[0023] Regarding the OPA, a waveguide and a photodetector can be connected to the first side of each of a plurality of splitters for light entry and exit, and two waveguides are connected to the second side of each of the plurality of splitters and branch off from each of the plurality of splitters, and each of a plurality of phase shifters is disposed in one of the two waveguides branching off from each of the plurality of splitters.

[0024] Regarding OPA, the number of multiple phase shifters can be equal to the number of multiple splitters, or the number of multiple phase shifters can be greater than the number of multiple splitters disposed between the optical injector and the antenna array.

[0025] When the number of multiple phase shifters is greater than the number of multiple splitters, the multiple phase shifters can be set in each of the multiple waveguides set between the first splitter and the antenna array.

[0026] The OPA may also include a thermal shielding element disposed around each of the first phase shifter and the plurality of phase shifters.

[0027] Regarding the OPA, a waveguide may be connected to the first side of each of a plurality of splitters for light entry and exit, and two waveguides may be connected to the second side of each of the plurality of splitters and branch off from each of the plurality of splitters, and a tap coupler may be configured to be adjacent to a waveguide connected to the first side of each of the plurality of splitters.

[0028] According to another aspect of the example embodiment, an optical phased array (OPA) is provided, comprising: an optical receiver; a first splitter connected to the optical receiver; a first phase shifter connected to the first splitter; a plurality of waveguides connected to the first splitter, portions of the plurality of waveguides being connected to the first splitter via the first phase shifter; an antenna array connected to the plurality of waveguides; and a single-mode filter disposed in each of the plurality of waveguides.

[0029] The OPA may also include: multiple splitters disposed between the first splitter and multiple waveguides; and multiple photodetectors connected to the multiple splitters.

[0030] OPA may also include multiple phase shifters positioned between multiple separators.

[0031] Regarding the OPA, one waveguide can be connected to a first side of a first splitter for light entry and exit, and two waveguides can be connected to a second side of the first splitter and branch off from the first splitter, wherein a first phase shifter can be disposed on one of the two waveguides branching off from the first splitter.

[0032] Regarding the OPA, a waveguide and a photodetector can be connected to the first side of each of the multiple splitters through which light enters and exits, and two waveguides can be connected to the second side of each of the multiple splitters and branch off from each of the multiple splitters.

[0033] The photodetector connected to the first side of each of the multiple splitters may include a first optical receiving element and a second optical receiving element respectively disposed on each side of a waveguide.

[0034] Multiple photodetectors can be positioned to receive light that deflects off the waveguides as light radiated onto the antenna array passes through the multiple waveguides and splitters.

[0035] A single-mode filter can be integrated into each of multiple waveguides.

[0036] A single-mode filter may include: a first portion having a first width; a second portion having a second width; and a third portion having a third width; wherein the first width, the second width, and the third width are different from each other.

[0037] For an OPA, a waveguide and a first photodetector may be connected to the first side of each of a plurality of splitters into which light enters and exits, and two waveguides may be connected to the second side of each of the plurality of splitters and branch off from each of the plurality of splitters, and each of a plurality of phase shifters may be disposed in one of the two waveguides branching off from each of the plurality of splitters.

[0038] The number of phase shifters can be equal to the number of splitters, or the number of phase shifters can be greater than the number of splitters positioned between the optical receiver and the antenna array.

[0039] When the number of multiple phase shifters is greater than the number of multiple splitters, the phase shifters can be disposed in each of the multiple waveguides disposed between the first splitter and the antenna array.

[0040] The OPA may also include a thermal shielding element disposed around each of the first phase shifter and the plurality of phase shifters.

[0041] Regarding the OPA, a waveguide may be connected to the first side of each of a plurality of splitters for light entry and exit, and two waveguides may be connected to the second side of each of the plurality of splitters and branch off from each of the plurality of splitters, and a tap coupler may be configured to be adjacent to a waveguide connected to the first side of each of the plurality of splitters.

[0042] According to another aspect of the example embodiment, a method for correcting phase error of an optical phased array (OPA) is provided, the method comprising: radiating light from the outside of the OPA to an antenna array of the OPA; measuring an electrical signal corresponding to at least a portion of the radiated light at a first location, the first location being located at a first distance along a waveguide from the antenna array; obtaining a phase correction value based on the measured electrical signal; and applying the obtained phase correction value to the OPA.

[0043] Electrical signal measurements can be performed simultaneously on multiple waveguides included in the OPA.

[0044] Measuring electrical signals may include: measuring the electrical signal corresponding to light deviating from a channel positioned at a first location, based on the phase difference between two adjacent waveguides of the transmitted radiated light.

[0045] Measuring electrical signals may include measuring electrical signals emitted from a photodetector located at a first position and configured to receive at least a portion of light.

[0046] After phase correction is completed at the first position, the method is repeated at a second position between the light injector into which light is injected and the first position when the OPA is operating normally.

[0047] The photodetector may include a first light receiving element and a second light receiving element, which are respectively connected to a separator disposed at a first location.

[0048] The photodetector may include a tapped coupler configured to be adjacent to the waveguide.

[0049] When measuring the electrical signal at the second position, measurements can be performed simultaneously on multiple waveguides positioned between the first and second positions.

[0050] After phase correction is completed at the second position, the method can be repeated at a third position between the light injector and the second position.

[0051] Phase shifters can be placed in each of multiple waveguides.

[0052] Multiple splitters and multiple phase shifters are placed between the optical injector and the antenna array, with the number of splitters equal to the number of phase shifters.

[0053] The heat shielding element can be placed on each of the phase shifters.

[0054] A single-mode filter is placed in each of the multiple waveguides.

[0055] A single-mode filter can be integrated into each of multiple waveguides.

[0056] A single-mode filter may include: a first portion having a first width; a second portion having a second width; and a third portion having a third width; wherein the first width, the second width, and the third width are different from each other. Attached Figure Description

[0057] The above and other aspects, features, and advantages of exemplary embodiments of the present disclosure will become clearer from the following description taken in conjunction with the accompanying drawings, in which:

[0058] Figure 1 This is a block diagram illustrating a concept for a method of correcting phase errors generated during the manufacturing process of an optical phased array (OPA) according to an example embodiment;

[0059] Figure 2 This is a flowchart illustrating a method for correcting phase errors generated during the OPA manufacturing process according to an example embodiment;

[0060] Figure 3 This is a plan view illustrating a first OPA according to an example embodiment, the first OPA including components for correcting phase errors generated during the manufacturing process;

[0061] Figure 4 It is a graph showing the variation in the intensity of the optical signal output to the main path of the splitter and the intensity of the optical signal output to the side path of the splitter according to an example embodiment, based on the phase difference between the light transmitted through the two input channels in a 3×2 splitter of the OPA, wherein the OPA includes components for correcting phase errors generated during the manufacturing process.

[0062] Figure 5 This is a plan view illustrating a second OPA according to an example embodiment, the second OPA including components for correcting phase errors generated during the manufacturing process;

[0063] Figure 6 This is a plan view illustrating a third OPA according to an example embodiment, the third OPA including components for correcting phase errors generated during the manufacturing process;

[0064] Figure 7 This is a plan view illustrating a fourth OPA according to an example embodiment, the fourth OPA including components for correcting phase errors generated during the manufacturing process;

[0065] Figure 8 It is along Figure 7 A cross-sectional view taken from line 8-8′;

[0066] Figure 9 This is a plan view illustrating a fifth OPA according to an example embodiment, the fifth OPA including components for correcting phase errors generated during the manufacturing process;

[0067] Figure 10 This is a plan view illustrating an example of a single-mode filter included in an OPA according to an exemplary embodiment, the OPA including components for correcting phase errors generated during the manufacturing process. Detailed Implementation

[0068] Referring now to the exemplary embodiments shown in the accompanying drawings, wherein the same reference numerals refer to the same elements throughout the drawings. In this respect, exemplary embodiments may take different forms and should not be construed as limited to the description set forth herein. Therefore, exemplary embodiments are described below only with reference to the accompanying drawings to explain various aspects. The term “and / or” as used herein includes any and all combinations of one or more of the related listed items. Expressions such as “at least one of…” modify the entire list of elements when following a list of elements, rather than individual elements in the list. For example, the expression “at least one of a, b, and c” should be understood to include only a, only b, only c, both a and b, both a and c, both b and c, or all of a, b, and c. Throughout the specification, unless otherwise stated, when a portion “includes” an element, it may also include another element, rather than excluding the presence of another element.

[0069] In an ideal optical phased array (OPA) chip, if the waveguide lengths of all channels are matched and no voltage is applied to the phase shifter, that is, no phase modulation occurs, the beam emitted from the antenna array is collected and radiated in a direction parallel to the waveguide propagation direction.

[0070] However, in actual manufactured OPAs, the waveguide width has an error of several nanometers along the travel direction. Therefore, there is an error between the optical path of the waveguide in an actual manufactured OPA and its design value.

[0071] Typically, when waveguide lengths are hundreds of μm or greater, phase variations due to manufacturing errors become random within the range of 0 to 2π, meaning these errors are difficult to predict. Consequently, even if the lengths of all channels are matched during the design phase, the beam may not converge in one direction due to manufacturing errors. Therefore, it is necessary to determine the driving conditions of N phase shifters to emit the beam at the desired radiation angle. However, methods that involve observing the beam shape with a camera using related technologies and then changing the driving conditions of the phase shifters typically employ relatively expensive infrared cameras.

[0072] Furthermore, in related technologies, the shape of the output beam is optimized by individually controlling the phase shifter of each channel of the OPA chip. However, there is a problem that the correction time increases exponentially as the number of phase shifters increases (e.g., dozens or hundreds or more).

[0073] The OPA phase error correction method according to the example embodiment can improve or solve these problems and correct phase errors generated during the manufacturing process without using a camera, injecting light into the region from which light is emitted from the OPA chip, and measuring the electrical signal generated from the OPA chip.

[0074] The following will describe in detail, with reference to the accompanying drawings, an optical phased array including components for correcting phase errors generated during manufacturing, and a method for correcting phase errors using the optical phased array. For clarity, the thickness of layers or regions shown in the drawings may be magnified during this process.

[0075] First, the concept of a method for correcting phase errors generated during the OPA manufacturing process, according to an example embodiment, will be described.

[0076] like Figure 1As shown, light can be incident or injected into the antenna region 150 of the optical phased array region 140 of the OPA chip 100 at a given incident angle. The antenna region 150 may include an antenna array. The light L1 injected into the antenna region 150 propagates along the optical waveguide (channel) in the optical phased array region 140 in the opposite direction to the direction of light propagation when the OPA chip 100 is operating normally in light emission mode after phase error correction is completed. When light L1 propagates through the waveguides of the optical phased array region 140 where there is a phase error generated during the manufacturing process, some light may be emitted outside the area where the corresponding waveguides meet due to the phase error. The emitted light is detected by a photodetector capable of photoelectric conversion. The photodetector may be, for example, a photodiode or include a photodiode. An electrical signal ES1 corresponding to the detected light is generated from the photodetector. That is, a photoelectric conversion signal corresponding to the phase error is generated from the OPA chip 100. The electrical signal ES1 corresponding to the photoelectric conversion signal is sent to a signal processor 110 connected to the OPA chip 100. Signal processor 110 calculates the phase correction value required to remove the phase error based on electrical signal ES1, and sends a signal ES2 corresponding to the phase correction value to phase tuner 120. Phase tuner 120 sends a phase correction value ES3 to OPA chip 100 according to signal ES2 corresponding to the sent phase correction value. The phase of the phase shifter included in the optical phased array region 140 is controlled by the phase correction value ES3 sent from phase tuner 120. The above process can be repeated until the phase error is removed or reduced to a desired level. Figure 1 In the figure, reference numeral 130 may be a light source or a light injection unit (or light injector) into which light is injected.

[0077] Figure 2 An example embodiment based on is shown. Figure 1 The flowchart shown is a method for correcting phase errors generated during the OPA manufacturing process (hereinafter referred to as the OPA correction method).

[0078] refer to Figure 2In the OPA correction method according to the example embodiment, firstly, light is injected into the antenna array of the OPA to be corrected (S11). The light injected in the first operation S11 can be light belonging to the wavelength range of the light injected into the light injection unit of the OPA, where phase correction of the OPA has been completed. For example, when the OPA is operating normally, assuming that the light injected into the light injection unit is infrared light belonging to a specific wavelength range, the light injected into the antenna array in the first operation S11 can also be infrared light belonging to a specific wavelength range. For example, the light injected into the antenna array in the first operation S11 can be laser light in the infrared band. When light is injected into the antenna array, if a collimator is used, the entire antenna array can be uniformly illuminated by light. Light injection can also be applied to OPAs described later.

[0079] Next, regardless of whether the OPA has a phase error, in the reverse process of light emitted from the light source being radiated through the antenna array via multiple waveguide channels during normal OPA operation, light injected into the antenna array is transmitted into the OPA. The injected light is light that travels from the antenna array toward the light source along multiple channels included in the OPA, and in this process, an electrical signal based on at least a portion of the injected light's photoelectric conversion can be generated, regardless of the phase difference between the light propagating along each channel. The amplitude of the generated electrical signal may differ when there is a phase difference between the light propagating along each channel and when there is no phase difference. Furthermore, when there is a phase difference between the light propagating along each channel, the amplitude of the generated electrical signal may also differ depending on the magnitude of the phase difference.

[0080] In this way, as the light injected in the first operation S11 is transmitted to the OPA, an electrical signal is generated from the OPA, and this electrical signal includes information about whether the OPA has a phase error generated during the manufacturing process and, if so, how much the phase error is. Therefore, information about the phase error of the OPA can be obtained by measuring the electrical signal. The second operation is to measure the electrical signal from the OPA (S22).

[0081] The third operation is to determine whether there is a phase error in the OPA and the degree of the phase error by analyzing the electrical signal measured in the second operation S22, and then calculate the phase correction value for correcting the phase error of the OPA (S33).

[0082] That is, in the third operation S33, when the injected light for correcting the phase error passes through each channel, if it is determined that the OPA has a phase error based on the measured electrical signal, the amount of phase of the injected light corresponding to the correction is analyzed, and based on the analysis, the electrical signal value (phase correction value) to be applied to the phase shifter included in the OPA to correct the phase of the injected light passing through each channel is calculated.

[0083] In the fourth operation, the phase correction value calculated above is applied to the OPA to correct its phase (S44). As a result, phase errors generated during the OPA manufacturing process can be corrected. The phase error of the OPA can be eliminated or reduced to a desired level by performing a single phase correction on the OPA. Since phase errors of the OPA can occur in all the multiple channels included in the OPA, the phase correction of the OPA can be performed on phase errors generated in certain portions of the multiple channels included in the OPA. The phase correction process for correcting phase errors in the remaining portions of the multiple channels should be performed continuously.

[0084] Then, the phase correction is repeated (S55). If the phase correction process for the OPA performed in the fourth operation S44 is called the first phase correction process, the second and third phase correction processes can be performed subsequently in the first to fourth operations (S11 to S44). In other words, the first phase correction process can be performed repeatedly.

[0085] The OPA correction method according to the example embodiment will be further described in the description of the OPA, including the components used to correct phase errors generated during the manufacturing process.

[0086] Figure 3 A first OPA 200 according to an example embodiment is shown.

[0087] refer to Figure 3According to an example embodiment, the first OPA 200 includes an optical injection unit 260 and an antenna grating array (antenna array 250). Between the optical injection unit 260 and the antenna array 250, a plurality of optical waveguides WG1, WG2a, WG2b, WG3a to WG3d, WG4a to WG4h, a plurality of beam splitters S1 to S7, a plurality of phase shifters PS1 to PS7, a plurality of optical receiving elements 210 and 220, and a plurality of single-mode filters F1 to F8 are disposed. The optical injection unit 260 is the region into which light is injected when the OPA is operating normally. The light injected into the optical injection unit 260 can be light in the infrared band. The optical injection unit 260 can be one end of the first optical waveguide WG1, or the optical injection unit 260 can be a unit connected to one end of the first optical waveguide WG1. The first beam splitter S1 is disposed at the other end of the first optical waveguide WG1. The second optical waveguide WG2a and the third optical waveguide WG2b branch off from the first beam splitter S1. The second beam splitter S2 is connected to the other end of the second optical waveguide WG2a, and the third beam splitter S3 is connected to the other end of the third optical waveguide WG2b. The second optical waveguide WG2a is disposed between the first beam splitter S1 and the second beam splitter S2, and the third optical waveguide WG2b is disposed between the first beam splitter S1 and the third beam splitter S3. A first phase shifter PS1 is disposed on the third optical waveguide WG2b. The first phase shifter PS1 can be configured to control the refractive index of the portion of the third optical waveguide WG2b passing through the first phase shifter PS1. In an example, the first phase shifter PS1 can be configured to change the temperature of the portion of the third optical waveguide WG2b passing through the first phase shifter PS1. Due to the temperature change of the portion of the third optical waveguide WG2b passing through the first phase shifter PS1, the refractive index of the corresponding portion changes, and as a result, the phase of the light transmitted through the third optical waveguide WG2b can be controlled. In another example, the first phase shifter PS1 can be configured to control the carrier density supplied to the portion of the third optical waveguide WG2b passing through the first phase shifter PS1. When the carrier density supplied to the portion passing through the first phase shifter PS1 changes, the refractive index of the portion of the third optical waveguide WG2b passing through the first phase shifter PS1 is changed. Therefore, the phase of light transmitted through the third optical waveguide WG2b can be controlled by controlling the carrier density supplied to the portion passing through the first phase shifter PS1. The carrier density can include electron density or hole density. As an example, the first phase shifter PS1 can be configured as a PIN diode, a PN diode, or a capacitor. The above description of the first phase shifter PS1 can also be applied to the phase shifters described below.

[0088] The second optical waveguide WG2a branches off from the second beam splitter S2 into a fourth optical waveguide WG3a and a fifth optical waveguide WG3b. The fourth and fifth optical waveguides WG3a and WG3b are separate from each other. The fourth beam splitter S4 is connected to one end of the fourth optical waveguide WG3a. The fifth beam splitter S5 is connected to one end of the fifth optical waveguide WG3b. The second phase shifter PS2 is disposed on the fifth optical waveguide WG3b between the second beam splitter S2 and the fifth beam splitter S5.

[0089] The third optical waveguide WG2b branches off from the third beam splitter S3 into the sixth optical waveguide WG3c and the seventh optical waveguide WG3d. The sixth and seventh optical waveguides WG3c and WG3d are separate from each other. The sixth beam splitter S6 is connected to one end of the sixth optical waveguide WG3c. The seventh beam splitter S7 is connected to one end of the seventh optical waveguide WG3d. The third phase shifter PS3 is located on the seventh optical waveguide WG3d between the third and seventh beam splitters S3 and S7.

[0090] The fourth optical waveguide WG3a branches off from the fourth beam splitter S4 into the eighth optical waveguide WG4a and the ninth optical waveguide WG4b. The eighth and ninth optical waveguides WG4a and WG4b can be of the same length. The eighth and ninth optical waveguides WG4a and WG4b are parallel to each other and separated from each other. The first antenna AT1 and the second antenna AT2 are connected to the ends of the eighth and ninth optical waveguides WG4a and WG4b, respectively. When the OPA is operating normally, light transmitted through the fourth beam splitter S4 via the eighth optical waveguide WG4a can be emitted at a given angle via the first antenna AT1. Furthermore, light transmitted through the fourth beam splitter S4 via the ninth optical waveguide WG4b can be emitted at a given angle via the second antenna AT2.

[0091] When the first OPA 200 is used as a phase correction device to correct phase errors generated during the manufacturing process, it is similar to Figure 1The incident light L1 shown enters the first antenna AT1 and the second antenna AT2 from outside the first OPA 200. When the beam size of the external light incident on the first antenna AT1 and the second antenna AT2 is smaller than the dimensions of the first antenna AT1 and the second antenna AT2, the deviation in phase correction accuracy between the channels connected to the first antenna AT1 and the second antenna AT2 may increase. Therefore, the beam size of the external light incident on the first antenna AT1 and the second antenna AT2 can be equal to or greater than the areas of the first antenna AT1 and the second antenna AT2. This relationship between the first antenna AT1 and the second antenna AT2 and the external light incident upon them can be applied to other antennas and antenna array 250. The light incident on the first antenna AT1 and the second antenna AT2 propagates in a direction opposite to the direction when the first OPA 200 is operating normally. In other words, the light incident on the first antenna AT1 and the second antenna AT2 is transmitted through the eighth optical waveguide WG4a and the ninth optical waveguide WG4b, respectively, and is combined in the fourth beam splitter S4 located at a first distance from the first antenna AT1 and the second antenna AT2. Then, the light passes through the fourth optical waveguide WG3a, the second beam splitter S2 located at a second distance from the first antenna AT1 and the second antenna AT2, the second optical waveguide WG2a, and the first beam splitter S1 located at a third distance from the first antenna AT1 and the second antenna AT2, and reaches the first optical waveguide WG1.

[0092] The first antenna AT1 and the second antenna AT2 can be gratings, and depending on the antenna width, they can provide only the basic mode or provide both the basic mode and higher-order modes together. As a result, light incident on the first antenna AT1 and the second antenna AT2 can be transmitted as single-mode light through the eighth optical waveguide WG4a and the ninth optical waveguide WG4b, or it can be transmitted as light including both single-mode and multi-mode light through the eighth optical waveguide WG4a and the ninth optical waveguide WG4b. Multi-mode light can be filtered by a first single-mode filter F1 and a second single-mode filter F2 respectively disposed in the eighth optical waveguide WG4a and the ninth optical waveguide WG4b. For example, when multi-mode light passes through the first single-mode filter F1 and the second single-mode filter F2, it can be scattered and disappear outside the eighth optical waveguide WG4a and the ninth optical waveguide WG4b. Therefore, the single-mode light transmitted through the eighth optical waveguide WG4a and the ninth optical waveguide WG4b is collected in the fourth beam splitter S4. Single-mode light incident on the fourth optical splitter S4 via the eighth optical waveguide WG4a and the ninth optical waveguide WG4b is split into several modes, which diverge into any number of modes by intersecting each other. Then, the main light is transmitted to the second optical splitter S2 via the fourth optical waveguide WG3a, while the multimode light is transmitted to the first optical receiving element 210 and the second optical receiving element 220, which are capable of photoelectric conversion and connected to the fourth optical splitter S4. Therefore, an electrical signal corresponding to the generated multimode light can be generated from the first optical receiving element 210 and the second optical receiving element 220. The electrical signal can be used to analyze the phase difference and its magnitude between the light transmitted through the eighth optical waveguide WG4a and the ninth optical waveguide WG4b. The second optical splitter S2 and the first optical splitter S1 can also perform the same process as the fourth optical splitter S4. As a result, single-mode light can be transmitted to the first optical waveguide WG1. The second distance is greater than the first distance, and the third distance is greater than the second distance.

[0093] A first single-mode filter F1 is disposed in an eighth optical waveguide WG4a between the fourth beam splitter S4 and the first antenna AT1. Multimode light, including external light injected into the first antenna AT1, can be filtered by the first single-mode filter F1. Therefore, when light injected into the first antenna AT1 is transmitted to the fourth beam splitter S4 via the first single-mode filter F1 during phase error correction, only single-mode light can be transmitted to the fourth beam splitter S4. The first single-mode filter F1 can be configured to transmit only single-mode light to the fourth beam splitter S4. In one example, the first single-mode filter F1 can be part of the eighth optical waveguide WG4a, and can be a modified portion of the eighth optical waveguide WG4a to function as a single-mode filter. This will be described below. In another example, the first single-mode filter F1 can be a separate filter connected to the eighth optical waveguide WG4a as a single-mode filter. The first single-mode filter F1 can be configured to be closer to the first antenna AT1 than the fourth beam splitter S4. The description of the first single-mode filter F1 can be applied to the other single-mode filters described below.

[0094] The fourth phase shifter PS4 and the second single-mode filter F2 are disposed on the ninth optical waveguide WG4b between the fourth beam splitter S4 and the second antenna AT2. The second single-mode filter F2 can be located between the fourth phase shifter PS4 and the second antenna AT2.

[0095] The fifth optical waveguide WG3b branches from the fifth beam splitter S5 into the tenth optical waveguide WG4c and the eleventh optical waveguide WG4d. The tenth and eleventh waveguides WG4c and WG4d are parallel and separate from each other. The length of the tenth waveguide WG4c is the same as the length of the eleventh waveguide WG4d. The length of the tenth waveguide WG4c can also be the same as the length of the ninth waveguide WG4b. The third antenna AT3 is connected to one end of the tenth waveguide WG4c, and the fourth antenna AT4 is connected to one end of the eleventh waveguide WG4d. The third single-mode filter F3 is disposed on the tenth waveguide WG4c, which is positioned between the fifth beam splitter S5 and the third antenna AT3, wherein the fifth beam splitter S5 is located at a first distance from both the third and fourth antennas AT4. The fifth phase shifter PS5 and the fourth single-mode filter F4 are disposed on the eleventh waveguide WG4d, which is positioned between the fifth beam splitter S5 and the fourth antenna AT4. The fourth single-mode filter F4 is located between the fifth phase shifter PS5 and the fourth antenna AT4.

[0096] The sixth optical waveguide WG3c branches from the sixth beam splitter S6 into the twelfth optical waveguide WG4e and the thirteenth optical waveguide WG4f. The twelfth and thirteenth waveguides WG4e and WG4f are parallel and separate from each other. The length of the twelfth waveguide WG4e is the same as the length of the thirteenth waveguide WG4f. The length of the twelfth waveguide WG4e can also be the same as the length of the eleventh waveguide WG4b. The fifth antenna AT5 is connected to one end of the twelfth waveguide WG4e, and the sixth antenna AT6 is connected to one end of the thirteenth waveguide WG4f. The fifth single-mode filter F5 is disposed on the twelfth waveguide WG4e, which is positioned between the sixth beam splitter S6 and the fifth antenna AT5, wherein the sixth beam splitter S6 is located at a first distance from both the fifth and sixth antennas AT5 and AT6. The sixth phase shifter PS6 and the sixth single-mode filter F6 are mounted on the thirteenth optical waveguide WG4f, which is positioned between the sixth beam splitter S6 and the sixth antenna AT6. The sixth single-mode filter F6 is located between the sixth phase shifter PS6 and the sixth antenna AT6.

[0097] The seventh optical waveguide WG3d branches off from the seventh beam splitter S7 into the fourteenth optical waveguide WG4g and the fifteenth optical waveguide WG4h. The fourteenth and fifteenth waveguides WG4g and WG4h are parallel to each other and separate from one another. The length of the fourteenth waveguide WG4g is the same as the length of the fifteenth waveguide WG4h. The length of the fourteenth waveguide WG4g can also be the same as the length of the thirteenth waveguide WG4f.

[0098] The seventh antenna AT7 is connected to one end of the fourteenth optical waveguide WG4g, and the eighth antenna AT8 is connected to one end of the fifteenth optical waveguide WG4h. A seventh single-mode filter F7 is disposed on the fourteenth optical waveguide WG4g, which is positioned between the seventh beam splitter S7 and the seventh antenna AT7, with the seventh beam splitter S7 located at a first distance from both the seventh and eighth antennas AT8. A seventh phase shifter PS7 and an eighth single-mode filter F8 are disposed on the fifteenth optical waveguide WG4h, which is positioned between the seventh beam splitter S7 and the eighth antenna AT8. The eighth single-mode filter F8 is located between the seventh phase shifter PS7 and the eighth antenna AT8. The first antenna AT1 to the eighth antenna AT8 can form an antenna array 250.

[0099] exist Figure 3 In the diagram, the eighth optical waveguide WG4a to the fifteenth optical waveguide WG4h, respectively connected to the first antenna AT1 to the eighth antenna AT8, are used as channels. As the number of waveguide bifurcation stages n increases, the number of channels increases by a power of 2(2^n). n Here, n is 1, 2, 3... The beam splitter is positioned at the stage where the optical waveguide bifurcates. Figure 3In this case, the number of stages n in the optical waveguide bifurcation is 3. Therefore, the number of channels is eight (2^n). 3 The number of stages, n, can be increased to three or more. The first beam splitter S1 is located in the first stage, where the first optical waveguide WG1 splits the beam into two stages for the first time. Two beam splitters S2 and S3 are located in the second stage, and four beam splitters S4 to S7 are located in the third stage. Figure 3 In the process, the number of beam splitters at each stage where the optical waveguide branches is 2 to the power of (n-1) (2^n - 1)^n. (n-1) The total number of beam splitters set from the first level to the nth level is (2 n -1. The number of phase shifters in each stage and the total number of phase shifters from the first stage to the nth stage can be equal to the number of beam splitters.

[0100] exist Figure 3 In this configuration, the first light receiving element 210 and the second light receiving element 220 are connected to each of the first beam splitters S1 to the seventh beam splitter S7. The first light receiving element 210 and the second light receiving element 220 can be examples of photoelectric conversion elements. The first light receiving element 210 and the second light receiving element 220 can be, for example, a photodiode, or may include a photodiode. Figure 3 In this configuration, the first optical receiving element 210 and the second optical receiving element 220 are disposed on the left side of each of the beam splitters S1 to S7. Therefore, two optical receiving elements and one optical waveguide are led out on one side of each beam splitter (e.g., the fourth beam splitter S4), through which light can enter and exit, and the branched optical waveguides WG4a and WG4b are led out on the other side of the fourth beam splitter S4. When the connection of the two optical receiving elements to each beam splitter is considered as two branch lines connected to each beam splitter, Figure 3 Each beam splitter can have the following configuration: three branch lines are connected to the left side of each beam splitter, and two branch lines are connected to the right side of each beam splitter. This configuration can be a 3×2 beam splitter. If one branch line is connected to the left side of the beam splitter and two branch lines are connected to the right side, then the beam splitter can be a 1×2 beam splitter. In the three branch lines connected to the left side of the fourth beam splitter S4 having the 3×2 beam splitter configuration, the optical waveguide WG3a is the main path for transmitting light, and the two optical receiving elements (i.e., the first optical receiver 210 and the second optical receiver 220) are the side paths. The same applies to other beam splitters having the 3×2 beam splitter configuration.

[0101] During phase error correction, when the phases of the light emitted through the eighth optical waveguide WG4a and the ninth optical waveguide WG4b (which serve as the first and second channels, respectively) are different, the phase of the light transmitted through the ninth optical waveguide WG4b can be controlled by using the fourth phase shifter PS4 to control the refractive index in the region of the ninth optical waveguide WG4b where the fourth phase shifter PS4 is located. As a result, the phases of the light transmitted from the first antenna AT1 and the second antenna AT2 through the eighth optical waveguide WG4a and the ninth optical waveguide WG4b to the fourth beam splitter S4 can be the same. Figure 1 The phase tuner 120 provides an electrical signal ES3 to the fourth phase shifter PS4 to determine the extent to which the refractive index of this region of the ninth optical waveguide WG4b is controlled by using the fourth phase shifter PS4.

[0102] For example, when the eighth optical waveguide WG4a and the ninth optical waveguide WG4b have a phase error generated during the manufacturing of the OPA, such as when the widths of the eighth optical waveguide WG4a and the ninth optical waveguide WG4b are not equal, in order to perform phase error correction, when light incident on the first antenna AT1 and the second antenna AT2 is transmitted to the fourth beam splitter S4 through the eighth optical waveguide WG4a and the ninth optical waveguide WG4b, there is a phase difference between the light transmitted to the fourth beam splitter S4. Due to the phase difference, there is an optical signal output from the fourth beam splitter S4 to the first optical receiving element 210 and the second optical receiving element 220, which serve as side paths. Since the intensity of the optical signal output to the first optical receiving element 210 and the second optical receiving element 220 varies according to the phase difference, the optical signal ultimately contains information about the phase difference between the two lights transmitted through the eighth optical waveguide WG4a and the ninth optical waveguide WG4b. Through photoelectric conversion, an electrical signal corresponding to the optical signal is output from the first optical receiving element 210 and the second optical receiving element 220. Figure 1 The signal processor 110 measures the electrical signal ES1 output from the first optical receiver 210 and the second optical receiver 220. This measurement is included in... Figure 2 In the second operation S22.

[0103] Figure 4 This is a graph showing the changes in the intensity of the optical signal output to the main path and the optical signal output to the side path of the beam splitter, based on the phase difference between the light transmitted through the two input channels. The horizontal axis represents the phase difference, and the vertical axis represents the intensity of the optical signal output through each path. The first curve G1 represents the intensity of the optical signal output through the main path. The second curve G2 represents the intensity of the optical signal output through the first side path. The third curve G3 represents the intensity of the optical signal output through the second side path. The two input channels can be connected to... Figure 3The two optical waveguides on the right side of the beam splitter. For example, the two input channels can be the eighth optical waveguide WG4a and the ninth optical waveguide WG4b connected to the fourth beam splitter S4. The main path can be the fourth optical waveguide WG3a connected to the left side of the fourth beam splitter S4, and the first side path and the second side path can be the first optical receiving element 210 and the second optical receiving element 220 connected to the fourth beam splitter S4, respectively.

[0104] refer to Figure 4 When the phase difference between the light transmitted through the two input channels is 0°, constructive interference occurs between the light transmitted through the two input channels. As a result, it can be seen that the optical signal output from the fourth beam splitter S4 to the third optical waveguide WG3a, which serves as the main path, is maximized, while the optical signals transmitted to the first optical receiver 210 and the second optical receiver 220, which serve as the side paths, are minimized. Conversely, when the phase difference between the light transmitted through the two input channels is 180°, destructive interference occurs between the light transmitted through the two input channels. Therefore, it can be seen that the optical signals transmitted to the first optical receiver 210 and the second optical receiver 220, respectively, are maximized, while the optical signal output to the third optical waveguide WG3a, which serves as the main path, is minimized. When destructive interference occurs between the light transmitted through the two input channels, the optical signal not output to the main path can be scattered and diffused, and the diffused optical signal is collected in the first and second side paths and output. When the phase difference between the light transmitted through the two input channels changes from 0° to 180°, the intensity of the optical signal output to the third optical waveguide WG3a decreases, while the intensity of the optical signal transmitted to the first optical receiving element 210 and the second optical receiving element 220 increases. Conversely, when the phase difference between the light transmitted through the two input channels changes from 180° to 360°, the intensity of the optical signal output to the third optical waveguide (WG3a) increases, while the intensity of the optical signal transmitted to the first optical receiving element 210 and the second optical receiving element 220 decreases.

[0105] Figure 4 The response characteristics can be used to determine the phase difference between light transmitted through two input channels, and to determine the electrical signal value (e.g., voltage or current value) to be input to the phase shifter to remove the phase difference.

[0106] For example, when the two input channels are the eighth optical waveguide WG4a and the ninth optical waveguide WG4b, during the phase difference correction process, the light injected through the first antenna AT1 is transmitted to the fourth beam splitter S4 through the eighth optical waveguide WG4a, and the light injected through the second antenna AT2 is transmitted to the fourth beam splitter S4 through the ninth optical waveguide WG4b.

[0107] refer to Figure 4The phase difference between the light transmitted through the eighth optical waveguide WG4a and the ninth optical waveguide WG4b can be seen from the intensity of the optical signals received by the first optical receiving element 210 and the second optical receiving element 220, which are connected to the fourth beam splitter S4 as side paths. Furthermore, the intensity of the optical signals received by the first optical receiving element 210 and the second optical receiving element 220 can be found by measuring the electrical signals output from the first optical receiving element 210 and the second optical receiving element 220, which are photoelectric conversion elements. The phase difference can be removed by applying a phase change to the ninth optical waveguide WG4b using a fourth phase shifter PS4 disposed on the ninth optical waveguide WG4b. For example, the phase change of the ninth optical waveguide WG4b can be controlled by using the fourth phase shifter PS4 until the intensity of the optical signals received by the first optical receiving element 210 and the second optical receiving element 220 is minimized. The phase of the light transmitted through the ninth optical waveguide WG4b is changed by controlling the phase change of the ninth optical waveguide WG4b. Therefore, controlling the phase change of the ninth optical waveguide WG4b can ultimately represent controlling the refractive index of the portion of the ninth optical waveguide WG4b to which the fourth phase shifter PS4 is located. Thus, the phase change of the ninth optical waveguide WG4b can be controlled based on the electrical signal value applied to the fourth phase shifter PS4. When the first electrical signal value is applied to the fourth phase shifter PS4, if the intensity of the optical signal received by the first optical receiving element 210 and the second optical receiving element 220 is minimal, then the phase difference between the light passing through the eighth optical waveguide WG4a and the ninth optical waveguide WG4b disappears when the first electrical signal value is applied to the fourth phase shifter PS4. That is, the phase of the light passing through the eighth optical waveguide WG4a and the ninth optical waveguide WG4b is the same. In other words, the phase error generated during the manufacturing process of the eighth optical waveguide WG4a and the ninth optical waveguide WG4b can be corrected by controlling the value input to the fourth phase shifter PS4 to the first electrical signal value.

[0108] Identify the phase difference between the light passing through the eighth optical waveguide WG4a and the ninth optical waveguide WG4b, and locate the phase difference applied to the fourth phase shifter PS4 to remove the reference. Figure 4 The process describing the phase difference in electrical signal values ​​can also be applied to Figure 3The remaining optical waveguides of the first OPA 200 are shown. By applying this signal, the electrical signal values ​​to be applied to the fifth phase shifter PS5 to remove the phase errors of the tenth optical waveguide WG4c and the eleventh optical waveguide WG4d, the electrical signal values ​​to be applied to the sixth phase shifter PS6 to remove the phase errors of the twelfth optical waveguide WG4e and the thirteenth optical waveguide WG4f, and the electrical signal values ​​to be applied to the seventh phase shifter PS7 to remove the phase errors of the fourteenth optical waveguide WG4g and the fifteenth optical waveguide WG4h can be known. Furthermore, the electrical signal values ​​to be applied to the second phase shifter PS2 to remove the phase errors of the fourth optical waveguide WG3a and the fifth optical waveguide WG3b, and the electrical signal values ​​to be applied to the third phase shifter PS3 to remove the phase errors of the sixth optical waveguide WG3c and the seventh optical waveguide WG3d can be known. Additionally, the electrical signal value to be applied to the first phase shifter PS1 to remove the phase errors of the second optical waveguide WG2a and the third optical waveguide WG2b can be known.

[0109] Through Figure 3 In the first OPA 200, the input values ​​of the first phase shifter PS1 to the seventh phase shifter PS7 are controlled as electrical signal values, which can eliminate phase differences caused by the manufacturing process of all optical paths in the first OPA 200. That is, phase errors in the first OPA 200 generated during the manufacturing process can be completely corrected. Therefore, during normal operation of the first OPA 200, the phase of each channel can be controlled as needed during the transmission of light radiated to the light source through the channels to the antenna array 250 and its emission. Thus, more accurate and reliable beam steering can be achieved.

[0110] The process of correcting the phase error of the first OPA 200 includes minimizing the intensity of the optical signal output to the first optical receiving element 210 and the second optical receiving element 220, which serve as side paths. Minimizing the intensity of the optical signal output to the first optical receiving element 210 and the second optical receiving element 220 involves removing the phase difference between the relevant channels using a phase shifter, and the value of the electrical signal applied to the phase shifter changes according to the magnitude of the phase difference. The phase error correction process is performed on several channels. Therefore, the phase error correction process is a process of removing phase differences of various magnitudes, and it involves applying electrical signal values ​​of various magnitudes to the phase shifter to remove phase differences of various magnitudes. This process is repeated until the phase error is corrected. Therefore, when the phase error correction process is completed, data regarding the electrical signal values ​​applied to the phase shifter can be accumulated to remove phase differences of various magnitudes generated in the channels. The data obtained in this way can determine the degree to which an electrical signal is supplied to the phase shifter to control the phase of the channel to a given value. In other words, when controlling the phase of each channel during normal operation of the OPA according to its initial purpose, based on data obtained during the correction of the OPA's phase error—that is, when controlling the phase of the light transmitted through each channel—the amount of the electrical signal input to the phase shifter for phase control can be determined. Since the OPA's beam steering is the result of phase control of the light transmitted through multiple channels, the data obtained during the correction of the OPA's phase error can be used for beam steering.

[0111] In normal operation of the OPA, light injection into the light injection unit 260 can be performed using, for example, a horizontal incidence method via edge coupling through one side of the waveguide or a vertical incidence method via a grating coupler. In another example, light injection can be performed by injecting light from the light source into the light injection unit 260 after the light source has been directly supplied to the OPA chip.

[0112] Figure 5 A second OPA 300 according to another example embodiment is shown, which includes components for correcting phase errors that occur during the manufacturing process. Description will be based on reference only. Figure 3 The first OPA 200 described is different from other parts. Similar reference numerals are used to indicate the parts that are different from those in the figure. Figure 3 The components are basically the same. In the second OPA 300, such as Figure 3 The first optical receiving element 210 and the second optical receiving element 220 are not connected to each of the first beam splitters S1 to the seventh beam splitter S7. Only three optical waveguides are connected to each of the first beam splitters S1 to the seventh beam splitter S7. One optical waveguide is connected to the left side of each of the beam splitters S1 to S7, and two optical waveguides are connected to the right side of each of the beam splitters S1 to S7. Therefore, Figure 5Each of the beam splitters S1 to S7 is a 1×2 beam splitter. A first tap coupler 310 is positioned close to the first optical waveguide WG1. The first tap coupler 310 can be disposed between the light injection unit 260 and the first beam splitter S1. The first tap coupler 310 includes a first light receiving element 310a and a first tap path 310b connected to the first light receiving element 310a. The first tap coupler 310 is an element that extracts a portion of the light transmitted through the adjacent optical waveguide WG1, that is, extracts a portion of the light transmitted through the optical waveguide WG1 into the first tap path 310b. Therefore, the first tap path 310b can be positioned at a location configured to extract a portion of the light transmitted through the first optical waveguide WG1. For example, when light is transmitted in the opposite direction to normal operation, that is, when light is transmitted to the first optical waveguide WG1 through the first beam splitter S1, the first tap path 310b can be configured to extract a portion of the light transmitted through the first optical waveguide WG1. The first optical receiving element 310a may be, for example, a photodiode or include a photodiode. The first tap path 310b may be in contact with one side of the first optical waveguide WG1.

[0113] When the second OPA 300 is operating normally, the operation of the tapped couplers adjacent to the optical waveguide can be stopped to reduce the loss of light transmitted through the optical waveguide. This can be applied to all tapped couplers included in the second OPA 300.

[0114] The second tap coupler 312 is positioned adjacent to the second optical waveguide WG2a. The second tap coupler 312 is positioned closer to the second beam splitter S2 than the first beam splitter S1. The second tap coupler 312 includes a second optical receiving element 312a and a second tap path 312b. The second optical receiving element 312a may be, for example, a photodiode or include a photodiode. The second tap path 312b may be positioned at a location configured to extract a portion of the light transmitted through the second optical waveguide WG2a. For example, when a portion of the light transmitted through the second beam splitter S2 to the second optical waveguide WG2a and the first beam splitter S1 is emitted to the outside of the second optical waveguide WG2a, the second tap path 312b may be positioned at a location capable of receiving the emitted light. The third tap coupler 314 is positioned adjacent to the third optical waveguide WG2b. The third tap coupler 314 includes a third optical receiving element 314a and a third tap path 314b. The third tap coupler 314 can be disposed between the first phase shifter PS1 and the third beam splitter S3. The third optical receiving element 314a can be the same device as the first optical receiving element 310a and the second optical receiving element 312a, or it can be another photoelectric conversion element. The third tap path 314b can contact the third optical waveguide WG2b. The third tap path 314b can be an optical path configured to transmit light to the third optical receiving element 314a. The third tap path 314b can be configured to extract a portion of the light transmitted from the third beam splitter S3 to the third optical waveguide WG2b. The fourth tap coupler 316 is disposed close to the fourth optical waveguide WG3a. The fourth tap coupler 316 includes a fourth optical receiving element 316a and a fourth tap path 316b connected thereto. The fourth optical receiving element 316a can be the same photoelectric conversion element as the third optical receiving element 314a. The fourth tap coupler 316 is arranged closer to the fourth beam splitter S4 than the second beam splitter S2. The fourth tap path 316b can contact the fourth optical waveguide WG3a. The fourth tap path 316b can be positioned at a location configured to extract a portion of the light transmitted through the fourth beam splitter S4 to the fourth optical waveguide WG3a.

[0115] The fifth tap coupler 318 is positioned adjacent to the fifth optical waveguide WG3b. The fifth tap coupler 318 is located between the second phase shifter PS2 and the fifth beam splitter S5. The fifth tap coupler 318 includes a fifth optical receiving element 318a and a fifth tap path 318b connected thereto. The fifth optical receiving element 318a can be a photoelectric conversion element. For example, the fifth optical receiving element 318a can be a photodiode or include a photodiode. The fifth tap path 318b can contact the fifth optical waveguide WG3b. The fifth tap path 318b can be positioned at a location configured to extract light transmitted through the fifth optical waveguide WG3b via the fifth beam splitter S5.

[0116] The sixth tap coupler 320 is configured to be adjacent to the sixth optical waveguide WG3c. The sixth tap coupler 320 can be located between the third beam splitter S3 and the sixth beam splitter S6. The sixth tap coupler 320 includes a sixth optical receiving element 320a and a sixth tap path 320b. The sixth optical receiving element 320a can be the same element in configuration and function as the fifth optical receiving element 318a. One side of the sixth tap path 320b can be connected to the sixth optical receiving element 320a, and the other side can be close to or in contact with the sixth optical waveguide WG3c. In either case, the sixth tap path 320b can be positioned to extract light transmitted through the sixth optical waveguide WG3c via the sixth beam splitter S6.

[0117] The seventh tap coupler 322 is located close to the seventh optical waveguide WG3d. The seventh tap coupler 322 is positioned between the seventh beam splitter S7 and the third phase shifter PS3. The seventh tap coupler 322 can be positioned at a location configured to extract light transmitted through the seventh optical waveguide WG3d via the seventh beam splitter S7. The seventh tap coupler 322 may include a seventh optical receiving element 322a and a seventh tap path 322b. The seventh optical receiving element 322a may be the same device as the sixth optical receiving element 320a. The seventh optical receiving element 322a is separate from the seventh optical waveguide WG3d. One side of the seventh tap path 322b is connected to the seventh optical receiving element 322a, and its other side can be close to or in contact with the seventh optical waveguide WG3d to extract light. Extraction of light transmitted through the seventh optical waveguide WG3d via the seventh beam splitter S7 can be performed via the seventh tap path 322b.

[0118] The configurations of the first tap couplers to the seventh tap couplers 310, 312, 314, 316, 318, 320, and 322 described above can all be identical, but this is merely an example. In another example, some of the first tap couplers to the seventh tap couplers 310, 312, 314, 316, 318, 320, and 322 can be configured to be functionally identical to the remaining tap couplers, but their configurations can differ from the remaining tap couplers.

[0119] Figure 6 A third OPA 400 according to another example embodiment is shown, which includes components for correcting phase errors that occur during the manufacturing process. Regarding Figure 6 The description of the third OPA 400 is limited to... Figure 3 The first OPA 200 is different from the other parts. Furthermore, similar reference numerals are used to indicate the parts that are different from the other parts. Figure 3 The components are basically the same.

[0120] and Figure 3 Compared to the first OPA 200, the third OPA 400 includes more phase shifters. For example, the third OPA 400 may include more phase shifters than the first OPA 200. Figure 3 The first OPA 200 has more than twice the number of phase shifters.

[0121] refer to Figure 6 The phase shifter is disposed in all optical waveguides WG2a, WG2b, WG3a to WG3d, and WG4a to WG4h disposed between the first beam splitter S1 and the antenna array 250. That is, the third OPA 400 may include... Figure 3 The first phase shifter PS1 to the seventh phase shifter PS7, the eighth phase shifter PS8 disposed on the second optical waveguide WG2a, the ninth phase shifter PS9 disposed on the fourth optical waveguide WG3a, the tenth phase shifter PS10 disposed on the sixth optical waveguide WG3c, the eleventh phase shifter PS11 disposed on the eighth optical waveguide WG4a which serves as the first channel, the twelfth phase shifter PS12 disposed on the tenth optical waveguide WG4c which serves as the third channel, the thirteenth phase shifter PS13 disposed on the twelfth optical waveguide WG4e which serves as the fifth channel, and the fourteenth phase shifter PS14 disposed on the fourteenth optical waveguide WG4g which serves as the seventh channel.

[0122] When two phase shifters are arranged in the same location (equivalent optical waveguides), each phase shifter is responsible for a phase shift from 0 to π. For example, the second optical waveguide WG2a and the third optical waveguide WG2b can be equivalent optical waveguides, as can the fourth optical waveguide WG3a and the fifth optical waveguide WG3b. Equivalent optical waveguides can refer to two optical waveguides that branch directly from the same beam splitter. Therefore, the first phase shifter PS1 and the eighth phase shifter PS8 can be two phase shifters located in the same position, and each of the first phase shifter PS1 and the eighth phase shifter PS8 is responsible for a phase shift from 0 to π. Figure 3 The same applies to the first OPA200. When the second phase shifter PS2 is set only on the fifth optical waveguide WG3b in the fourth optical waveguide WG3a and the fifth optical waveguide WG3b, the second phase shifter PS2 is responsible for the phase shift from 0 to 2π.

[0123] Figure 7 A fourth OPA 500 according to another example embodiment is shown, which includes components for correcting phase errors that occur during the manufacturing process. Regarding Figure 7 The description of the fourth OPA 500 is limited to... Figure 3 The first OPA 200 is different from the other parts. Furthermore, similar reference numerals are used to indicate the parts that are different from the other parts. Figure 3 The components are basically the same.

[0124] refer to Figure 7 In the fourth OPA 500, thermal shielding elements 510, 520, 530, 540, 550, 560, and 570 are respectively disposed around the first phase shifter PS1 to the seventh phase shifter PS7. In a plan view, each of the thermal shielding elements 510, 520, 530, 540, 550, 560, and 570 may surround the entire corresponding phase shifter. Each of the thermal shielding elements 510, 520, 530, 540, 550, 560, and 570 is configured to prevent or reduce heat transfer generated from the operation of the corresponding phase shifter to adjacent optical waveguides (channels), or to minimize heat transfer. Due to the provision of thermal shielding elements, the influence of heat generated during the correction of the phase of a particular channel on the phase correction of adjacent channels can be prevented or reduced. Thermal shielding elements may also be disposed in... Figure 6 In the third OPA 400.

[0125] Figure 8 An example of a heat-shielding element is shown, and the following is illustrated along... Figure 7 The cross section taken from line 8-8' in the middle.

[0126] refer to Figure 8 Fourteenth optical waveguide WG4g and fifteenth optical waveguide WG4h are separated from each other on substrate 600. Substrate 600 may include a silicon substrate, and may include various substrates. For example, gallium arsenide (GaAs), indium phosphide (InP), SiO2, etc., can be used as substrate 600. The material of the fourteenth optical waveguide WG4g and the fifteenth optical waveguide WG4h may include silicon. Although it is described that the seventh phase shifter PS7 is disposed on one side of the fifteenth optical waveguide WG4h, the embodiment is not limited thereto. For example, the portion of the fifteenth optical waveguide WG4h that contacts the seventh phase shifter PS7 may also be a component of the seventh phase shifter PS7. A trench 610 is formed in the substrate 600 between the fourteenth optical waveguide WG4g and the fifteenth optical waveguide WG4h. The trench 610 is formed closer to the fifteenth optical waveguide WG4h than the fourteenth optical waveguide WG4g. The trench 610 is disposed on both sides of the fifteenth optical waveguide WG4h. Because trench 610 is formed around the fifteenth optical waveguide WG4h, it prevents heat generated during the operation of the seventh phase shifter PS7 to control the phase of light transmitted through the fifteenth optical waveguide WG4h from being transferred to the fourteenth optical waveguide WG4g. Trench 610 may be left unfilled or may be filled with an insulating material with low thermal conductivity, such as SiO2.

[0127] Figure 9The fifth OPA 900, including components for correcting phase errors, is shown. In the fifth OPA 900, the right-hand portion of the first beam splitter S1 is identical to any of the first OPA 200, second OPA 300, third OPA 400, and fourth OPA 500 described above; therefore, its description is omitted. If the first OPA 200, second OPA 300, third OPA 400, and fourth OPA 500 are OPAs that combine a light emission mode (the normal operating mode of the OPA with phase correction completed) and a light reception mode (phase correction mode), then the fifth OPA 900 is an OPA that operates only in the light reception mode. The fifth OPA 900 does not have a light injection unit. The fifth OPA 900 includes an optical receiver 910, replacing the light injection unit 260 of the first OPA 200, second OPA 300, third OPA 400, and fourth OPA 500. The first beam splitter S1 is a 1×2 beam splitter and does not include the first optical receiving element 210 and the second optical receiving element 220 connected to the first OPA 200, second OPA 300, third OPA 400, and fourth OPA 500. The fifth OPA 900 operates in optical receiving mode, but can perform phase difference correction of the optical waveguide between the first beam splitter S1 and the antenna array 250 in the same manner as described in the first OPA 200, second OPA 300, third OPA 400, and fourth OPA 500. The optical receiver 910 can be a photodetector. The optical receiver 910 can be an optical receiving element or an optical receiver including an optical receiving element. For example, the optical receiving element can be a photodiode. The optical receiver 910 can measure the amount of light incident through the antenna array 250.

[0128] Figure 10 Examples are shown of any one of the single-mode filters F1 to F8 included in the first OPA 200, second OPA 300, third OPA 400, and fourth OPA 500 described above. For example, Figure 10 The single-mode filter described herein can be the first single-mode filter F1. Regarding Figure 10 The description of the single-mode filter depicted can be applied to other single-mode filters. Figure 10 The first single-mode filter F1 depicted is not set separately from the channel, but is formed by modifying certain parts of the optical waveguide.

[0129] refer to Figure 10 By modifying certain parts of the eighth optical waveguide WG4a to enable the corresponding parts to function as single-mode filters, a first single-mode filter F1 is formed.

[0130] In detail, the first single-mode filter F1 may include a first portion P1, a second portion P2, and a third portion P3. The first portion P1 is connected to the fourth beam splitter S4, and the third portion P3 is connected to the first antenna AT1. Among the first portions P1 to the third portions P3, the width W1 of the first portion P1 is the smallest, while the width W3 of the third portion P3 is the largest. The width W1 of the first portion P1 may be the width of the basic mode (single-mode) that can only transmit light. For example, the width W1 of the first portion P1 may be from about 0.2 μm to about 1 μm. However, the size of the width W1 is not limited to this. The width W3 of the third portion P3 may be, for example, from about 0.5 μm to 10 μm, but is not limited to this. The second portion P2 is between the first portion P1 and the third portion P3, and the width W2 changes in the length direction. The width W2 of the second portion P2 increases from the first portion P1 toward the third portion P3. When light is incident through the antenna to correct the phase error of the OPA, the light transmitted from the first antenna AT1 to the third portion P3 may include the basic mode and several higher-order modes. In other words, in the third part P3, light from the first antenna AT1 mixed with light from the second and third modes can be transmitted. Therefore, the third part P3 can be a multimode part. Light transmitted to the third part P3 passes through the second part P2, where the width W2 gradually decreases. At this point, light from several higher-order modes, besides the fundamental mode, is sequentially scattered to leave the optical waveguide WG4a, and only the fundamental mode light is transmitted to the first part P1. Therefore, the first part P1 can be a single-mode part. Furthermore, since light converts from multimode to single-mode when passing through the second part P2, the second part P2 can be a conversion part. As a result of the single-mode filter, only single-mode light can be transmitted to the beam splitter side.

[0131] When considering the configuration of the first single-mode filter F1 and when the OPA is operating normally in optical emission mode, the effect of the first single-mode filter F1 should be taken into account. However, when the length of the second portion P2 is sufficiently long, the single-mode light transmitted to the first single-mode filter F1 via the fourth beam splitter S4 can remain single-mode even after passing through the second portion P2. As a result, when the OPA is operating normally and when the length of the second portion P2 is sufficiently long, the single-mode light transmitted to the first single-mode filter F1 via the fourth beam splitter S4 can remain single-mode even after passing through the first single-mode filter F1. Therefore, when the OPA is operating normally, the light passing through the first single-mode filter F1 can be transmitted to the first antenna AT1 while maintaining single-mode operation. The length of the second portion P2, to obtain these results, can be, for example, from about 10 μm to 100 μm, but is not limited to this.

[0132] The evaluation of OPA phase correction methods can be based on the number of phase shifter input combinations that should be evaluated to achieve a specific side-mode rejection ratio (SMSR). In other words, the OPA phase correction method can be evaluated by the number of times the process of inputting an electrical signal to a phase shifter included in the OPA (the evaluation process) needs to be repeated until the desired result (e.g., beam formation) is obtained. When a first correction method is used instead of a second correction method in the evaluation process, the first correction method can be evaluated as relatively superior to the second correction method if the first correction method is repeated fewer times than the second correction method.

[0133] When using the OPA according to the above example embodiment (e.g., Figure 3 When describing the first OPA 200, the number of times the evaluation process is repeated to obtain the desired beam formation will be described.

[0134] Figure 3 The first OPA 200 has 8 channels (WG4a to WG4h), but for evaluation purposes, the number of channels in the first OPA 200 is considered to be 32. To make the number of channels in the first OPA 200 32, besides... Figure 3 In addition to the three levels shown, two more levels should be added on the right. That is, the number of levels n is 5, and the number of channels is 2 to the power of 5 (2^5). 5 The result is 32. In the case of the first OPA 200, two optical waveguides branch off from each of the splitters S1 to S7 at each stage, and the phase shifter is located at half of the branched optical waveguide. Therefore, when 32 channels are set in the first OPA 200, the total number of phase shifters included in the first OPA 200 is 31 (16+8+4+2+1). Considering the number of phase shifters, it is practically difficult to perform a scan using phase shifters (i.e., to perform phase control over the entire period (2π)). Therefore, it can be assumed that a phase scan performed by using phase shifters is performed under the following conditions.

[0135] In detail, the phase of one cycle (2π) is divided into eight steps, and scans are performed at π / 4 intervals in each phase shifter. During the scan of the phase in the eight steps considered for the correction scan, additional scans are performed for four values ​​surrounding the electrical signal value applied to the phase shifter used for the corresponding scan. This increases accuracy. For example, assuming a correction result is obtained in the case of a two-stage scan with a phase of π / 2 (i.e., when the phase of light transmitted through the corresponding channel is controlled by using phase shifters in up to π / 2), it can be assumed that the change in the correction result can be observed by controlling the phase of the transmitted light to four values ​​slightly greater or less than π / 2.

[0136] Under these conditions, when the evaluation process is performed using 31 phase shifters to obtain the desired correction result (e.g., beamforming), the evaluation process is repeated a total of 372 times, i.e., the number of phase shifters: 31 × (the number of scan steps per phase shifter in one cycle: 8 + the number of additional scans performed in a specific scan step: 4). That is, when using Figure 3 With the first OPA 200, the desired beam formation can be obtained after 372 evaluation processes.

[0137] Compared to related technologies with 32-channel OPAs, the number of evaluations performed until the desired correction result (e.g., beamforming) is obtained using a correction algorithm such as PSO (an algorithm for controlling the input values ​​of the phase shifter) is 207,600; the number of evaluations performed using a calibration algorithm called SPGD is 80,001; and the number of evaluations performed using a calibration algorithm called DSGD is 7,048. The number of evaluations is... Figure 3 The first OPA 200 (which is 372 times) is about 15 times faster, and up to about 500 times faster. This shows that when phase correction is performed using the OPA according to the example embodiment described above, phase correction can be about 15 to 500 times faster. Furthermore, in Figure 3 In the case of the first OPA 200, the electrical signal (i.e., photocurrent value) output from the photodetector is measured during the evaluation process. However, the phase correction evaluation performed using an OPA based on related technologies is a process to confirm whether phase correction is required by capturing an image using a camera. Therefore, when phase correction is performed using an OPA according to the above example embodiment, correction costs and time can be reduced compared to related technologies.

[0138] The phase error correction method using the OPA according to the above example embodiments is not limited to correcting phase errors generated during the OPA manufacturing process. The OPA correction method according to the above example embodiments can be used as a correction method for all phase errors occurring between channels included in the OPA (regardless of the cause of occurrence).

[0139] Furthermore, the OPA and the phase correction method using the OPA can be extended to general phased arrays and phase correction methods. That is, the configuration of the first OPA 200, the second OPA 300, the third OPA 400, the fourth OPA 500, and the fifth OPA 900 can be applied to general phased arrays using electromagnetic waves with wavelengths outside the infrared band. The beam splitters described in the first OPA 200, the second OPA 300, the third OPA 400, the fourth OPA 500, and the fifth OPA 900 can be splitters, the optical waveguides can be waveguides, and the optical injection units can be electromagnetic wave injection units.

[0140] A phase correction method employs a concept entirely different from related OPA phase correction methods. Specifically, light for phase correction is injected into the OPA antenna array so that it travels in the opposite direction to the direction of light travel during normal OPA operation. In addition to the main optical waveguide, a light-receiving element, conceived as a side path, is connected to a beam splitter included in the OPA. When a phase difference exists between light propagating in opposite directions through the channel, the light-receiving element connected to the beam splitter receives the optical signal corresponding to the phase difference. The received optical signal is converted into an electrical signal via photoelectric conversion, and finally, an electrical signal value for correcting the phase difference is generated by a signal processor and a phase tuner. Phase correction is then achieved by applying the electrical signal value to a phase shifter. This series of processes may include injecting light into the OPA in the opposite direction, measuring the optical signal containing information about the phase difference of the channel, and performing phase correction based on the optical signal. Compared to the phase correction process of related techniques that compare and analyze images captured using a camera, this correction method is simpler and reduces time and cost because it more easily measures the resulting optical signal corresponding to the phase difference without capturing an image.

[0141] Furthermore, since the phase of the channel can be controlled more precisely by using a phase shifter, the intensity of the measured optical signal can also be controlled more precisely. As a result, fine phase correction can be performed, and more accurate and reliable phase correction can be achieved. Through this process, data of the electrical signal value can be obtained and applied to the phase shifter for phase control of each channel, and the obtained data can be used to phase control each channel to emit a beam in the desired direction when the OPA is operating normally after phase correction.

[0142] In addition to corrections related to phase errors generated during the manufacturing process, the OPA according to the above example embodiments can also correct phase errors occurring in the OPA for various reasons.

[0143] It should be understood that the embodiments described herein should be considered in a descriptive sense rather than for limiting purposes. The description of features or aspects in each example embodiment should typically be regarded as other similar features or aspects that can be used in other example embodiments.

[0144] Although exemplary embodiments have been described with reference to the accompanying drawings, those skilled in the art will understand that various changes in form and detail may be made without departing from the spirit and scope defined by the claims.

Claims

1. An optical phased array, comprising: Light injector; A first separator is connected to the light injector; A first phase shifter is connected to the first separator; Multiple waveguides are connected to the first splitter, and portions of the multiple waveguides are connected to the first splitter via the first phase shifter; Antenna array, connected to the plurality of waveguides; A single-mode filter is disposed in each of the plurality of waveguides; as well as A first photodetector is connected to the first separator and configured to detect a portion of the light radiated onto the antenna array.

2. The optical phased array according to claim 1, further comprising: Multiple separators are disposed between the first separator and the multiple waveguides; as well as Multiple photodetectors are connected to the multiple separators.

3. The optical phased array according to claim 2 further includes a plurality of phase shifters disposed between the plurality of splitters.

4. The optical phased array according to claim 1, wherein, A waveguide and the first photodetector are connected to the first side of the first separator where light enters and exits. Two of the waveguides are connected to the second side of the first splitter and branch off from the first splitter, and The first phase shifter is disposed on one of the two waveguides.

5. The optical phased array according to claim 2, wherein, A waveguide and photodetector are connected to the first side of each of the plurality of splitters through which light enters and exits, and Two waveguides are connected to the second side of each of the plurality of splitters and branch off from each of the plurality of splitters.

6. The optical phased array according to claim 4, wherein, The first photodetector includes a first light receiving element and a second light receiving element respectively disposed on opposite sides of the waveguide.

7. The optical phased array according to claim 5, wherein, The photodetector connected to the first side of each of the plurality of splitters includes a first optical receiving element and a second optical receiving element respectively disposed on opposite sides of the waveguide.

8. The optical phased array according to claim 2, wherein, The plurality of photodetectors are positioned to receive light that deviates from the plurality of waveguides as light radiated onto the antenna array passes through the plurality of waveguides and splitters.

9. The optical phased array according to claim 1, wherein, The single-mode filter is integrated into each of the plurality of waveguides.

10. The optical phased array according to claim 9, wherein, The single-mode filter includes: The first portion having a first width; The second part having a second width; and The third part with a third width, The first width, the second width, and the third width are different from each other.

11. The optical phased array according to claim 3, wherein, A waveguide and photodetector are connected to the first side of each of the plurality of splitters for light entry and exit, and two waveguides are connected to the second side of each of the plurality of splitters and branch off from each of the plurality of splitters. Each of the plurality of phase shifters is disposed in one of the two waveguides that branch off from each of the plurality of splitters.

12. The optical phased array according to claim 3, wherein, The number of the plurality of phase shifters is equal to the number of the plurality of splitters, or the number of the plurality of phase shifters is greater than the number of the plurality of splitters disposed between the optical injector and the antenna array.

13. The optical phased array according to claim 12, wherein, When the number of the plurality of phase shifters is greater than the number of the plurality of splitters, the plurality of phase shifters are disposed in each of the plurality of waveguides disposed between the first splitter and the antenna array.

14. The optical phased array of claim 3 further includes a heat shielding element disposed around each of the first phase shifter and the plurality of phase shifters.

15. The optical phased array according to claim 2, wherein, A waveguide is connected to a first side of each of the plurality of splitters for light entry and exit, and two waveguides are connected to a second side of each of the plurality of splitters and branch off from each of the plurality of splitters. The tapped coupler is configured to be adjacent to one of the waveguides connected to a first side of each of the plurality of splitters.

16. An optical phased array, comprising: Optical receiver; A first splitter is connected to the optical receiver; A first phase shifter is connected to the first separator; Multiple waveguides are connected to the first splitter, and portions of the multiple waveguides are connected to the first splitter via the first phase shifter; Antenna array, connected to the plurality of waveguides; as well as A single-mode filter is disposed in each of the plurality of waveguides. The optical receiver measures the amount of light incident through the antenna array.

17. The optical phased array according to claim 16, further comprising: Multiple separators are disposed between the first separator and the multiple waveguides; as well as Multiple photodetectors are connected to the multiple separators.

18. The optical phased array of claim 17 further includes a plurality of phase shifters disposed between the plurality of splitters.

19. The optical phased array according to claim 16, wherein, A waveguide is connected to a first side of the first splitter where light enters and exits, and two waveguides are connected to a second side of the first splitter and branch off from the first splitter. The first phase shifter is disposed on one of the two waveguides that branch off from the first splitter.

20. The optical phased array according to claim 17, wherein, A waveguide and a photodetector are connected to the first side of each of the plurality of splitters through which light enters and exits, and two waveguides are connected to the second side of each of the plurality of splitters and branch off from each of the plurality of splitters.

21. The optical phased array according to claim 20, wherein, The photodetector connected to the first side of each of the plurality of splitters includes a first optical receiving element and a second optical receiving element respectively disposed on opposite sides of the waveguide.

22. The optical phased array according to claim 17, wherein, The plurality of photodetectors are positioned to receive light that deflects off the waveguides as light radiated onto the antenna array passes through the plurality of waveguides and splitters.

23. The optical phased array according to claim 16, wherein, The single-mode filter is integrated into each of the plurality of waveguides.

24. The optical phased array according to claim 23, wherein, The single-mode filter includes: The first portion having a first width; The second part having a second width; and A third part with a third width; The first width, the second width, and the third width are different from each other.

25. The optical phased array according to claim 18, wherein, A waveguide and photodetector are connected to the first side of each of the plurality of splitters for light entry and exit, and two waveguides are connected to the second side of each of the plurality of splitters and branch off from each of the plurality of splitters. Each of the plurality of phase shifters is disposed in one of the two waveguides that branch off from each of the plurality of splitters.

26. The optical phased array according to claim 18, wherein, The number of the plurality of phase shifters is equal to the number of the plurality of splitters, or the number of the plurality of phase shifters is greater than the number of the plurality of splitters disposed between the optical receiver and the antenna array.

27. The optical phased array according to claim 26, wherein, When the number of the plurality of phase shifters is greater than the number of the plurality of splitters, the plurality of phase shifters are disposed in each of the plurality of waveguides disposed between the first splitter and the antenna array.

28. The optical phased array of claim 18, further comprising a heat shielding element disposed around each of the first phase shifter and the plurality of phase shifters.

29. The optical phased array according to claim 17, wherein, A waveguide is connected to a first side of each of the plurality of splitters for light entry and exit, and two waveguides are connected to a second side of each of the plurality of splitters and branch off from each of the plurality of splitters. The tapped coupler is configured to be adjacent to one of the waveguides connected to a first side of each of the plurality of splitters.

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