On-chip waveguide grating antenna phase error detection method

Abstract

The invention discloses an on-chip waveguide grating antenna phase error detection method comprising the following steps: amplifying a waveguide grating antenna near field, and receiving the amplified near field by using a camera; irradiating the target surface of the camera through obliquely incident plane reference light, interfering with the near field amplified by the waveguide grating antenna to form an interference image, and collecting the interference image; and obtaining a one-dimensional sine interference curve of the interference image of each waveguide grating antenna unit, calculating the period of the one-dimensional sine interference curve and a difference value between peak values of the one-dimensional sine interference curve of the interference image of each waveguide grating antenna unit, and dividing the difference value by the period and multiplying by the wavelength to obtain the size of the phase error between the waveguide grating antenna units. According to the technical scheme, direct measurement of the phase error between the waveguide grating antennas can be achieved, and the defect that in the prior art, an optimization iterative algorithm is adopted to conduct indirect phase error detection and evaluation on the far field of the waveguide grating antennas is overcome.

Description

Technical Field

[0001] The present invention relates to the field of wavefront detection technology, and in particular to an on-chip waveguide grating antenna phase error detection method. Background Art

[0002] 75% of the target information obtained by humans comes from images, among which the acquisition and analysis of three-dimensional image information is becoming increasingly important. LiDAR is the mainstream cutting-edge technology for accurately and quickly acquiring three-dimensional images of targets. Around the beginning of the new century, humans have successfully used LiDAR technology to detect space, oceans, and the deep earth. With the recent rise of technologies such as artificial intelligence, unmanned driving, and 3D printing, LiDAR technology has shown broad application prospects. At present, LiDAR technology has a fatal flaw: it currently widely uses mechanical components to achieve reciprocating laser scanning. This large and slow optical mechanical system is not only very sensitive to temperature and shock, but also extremely expensive. The above situation has limited its scope of use in military and civilian fields.

[0003] The on-chip waveguide grating antenna uses phased array technology to achieve beam scanning, and controls the direction of light wave propagation by controlling the phase between a large number of small optical antenna units on the surface.

[0004] Waveguide grating antennas require high-density on-chip integration technology to achieve large transmitting and receiving apertures. However, due to manufacturing defects, there are inevitably differences in the length of the optical path between antennas, which will induce a randomly distributed and time-constant initial phase error. Without proper phase detection and calibration, the morphology of the far-field scanning spot will be destroyed. The far-field pattern is very chaotic, resulting in a decrease in the main lobe energy and an increase in the side lobes, or even a fragmentation of the scanning spot, which will cause a decrease in the detection distance and the generation of false alarms.

[0005] At present, the phase error detection and correction of waveguide grating antennas mainly use the far-field spot quality as the evaluation index and use iterative algorithms for optimization. Its technical limitations are:

[0006] (1) Due to the use of iterative optimization algorithm, there is a problem of long correction time.

[0007] (2) This method does not directly detect the phase error between waveguide grating antennas, but uses far-field information for direct correction and uses the far-field sidelobe suppression ratio for evaluation. It cannot directly detect the phase error between waveguide grating antennas and evaluate the phase error correction level of waveguide grating antennas. Summary of the invention

[0008] To solve the above problems, the present invention proposes an on-chip waveguide grating antenna phase error detection method, the method comprising:

[0009] S110, using a 4F optical system to amplify the near field of the waveguide grating antenna, and using a camera to receive the amplified near field, wherein the light emitted by the laser light source is first input into a fiber beam splitter via an optical fiber before reaching the 4F optical system, and the fiber beam splitter divides the input light into two paths: the first path of light reaches the coupler through the optical fiber, is input into the on-chip waveguide via end face coupling or grating coupling, and is divided into multiple paths by the on-chip beam splitter, and is radiated into free space via the waveguide grating antenna, and the light radiated into the free space passes through the 4F system composed of a microscope objective and a tube lens;

[0010] S120, irradiating the camera target surface with obliquely incident plane reference light, interfering with the near field amplified by the waveguide grating antenna to form an interference image, and collecting the interference image with a camera, wherein the obliquely incident plane reference light is formed by: the optical fiber beam splitter divides the input light into two paths: the second path of light passes through the optical fiber and the collimating lens to form a plane reference light, and the plane reference light is reflected by a beam splitter placed behind the tube mirror to form an obliquely incident plane reference light;

[0011] S130, obtaining a one-dimensional sinusoidal interference curve of the interference image of each waveguide grating antenna unit through an image processing algorithm, calculating the period of the one-dimensional sinusoidal interference curve and the difference between the peak values ​​of the one-dimensional sinusoidal interference curve of the interference image of each waveguide grating antenna unit, dividing the difference by the period and multiplying it by the wavelength to obtain the magnitude of the phase error between the waveguide grating antenna units.

[0012] Compared with the prior art, the present invention has the following beneficial effects:

[0013] (1) The on-chip waveguide grating antenna phase error detection device can be used to amplify the near field of the waveguide grating antenna, so as to achieve sufficient sampling of the near field of the waveguide grating antenna by the camera.

[0014] (2) The on-chip waveguide grating antenna phase error detection method can realize the direct detection of the phase error between waveguide grating antenna units.

[0015] (3) The on-chip waveguide grating antenna phase error detection method and device can realize the direct evaluation of the phase error correction level between waveguide grating antenna units. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The present invention is a flow chart of the on-chip waveguide grating antenna phase error detection method.

[0017] Figure 2 It is a schematic structural diagram of the on-chip waveguide grating antenna phase error detection device of the present invention.

[0018] Figure 3 This is a schematic diagram of the phase error detection method of the on-chip waveguide grating antenna of the present invention. DETAILED DESCRIPTION

[0019] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms, and the present disclosure should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0020] Figure 2 The figure is a schematic diagram of the structure of the on-chip waveguide grating antenna phase error detection device of the present invention. The device takes the near field of the waveguide grating antenna as the research object. Figure 2 As shown, the light emitted by the laser light source is input to the fiber beam splitter through the optical fiber, and the fiber beam splitter divides the input light into two paths: the first path of light reaches the coupler through the optical fiber, is input to the on-chip waveguide through end-face coupling or grating coupling, and is divided into multiple paths by the on-chip beam splitter, and radiates to the free space through the waveguide grating antenna. The light radiated to the free space is used as the target light, and after passing through the 4F system composed of the microscope objective and the tube lens, it forms the near field amplified by the waveguide grating antenna on the camera target surface; the second path of light passes through the optical fiber and the collimating lens to form a plane reference light. After being reflected by the beam splitter, the plane reference light reaches the camera target surface at a certain angle, and interferes with the near field amplified by the waveguide grating antenna to form an interference image. Finally, the interference image is collected by the camera.

[0021] Among them, the 4F optical system is used to amplify the near field of the waveguide grating antenna, so that the camera can fully sample the near field of the waveguide grating antenna.

[0022] In addition, a planar reference light is introduced to interfere with the near field of the waveguide grating antenna, and then the phase error can be calculated by the difference between the peaks of the one-dimensional interference pattern of the waveguide grating antenna unit. For this, please refer to the detailed description below.

[0023] Figure 1 FIG. 1 is a flow chart of the on-chip waveguide grating antenna phase error detection method of the present invention. Figure 1 As shown, the method comprises the following steps:

[0024] S110, using a 4F optical system to amplify the near field of the waveguide grating antenna, and using a camera to receive the amplified near field, wherein the light emitted by the laser light source is first input into a fiber beam splitter via an optical fiber before reaching the 4F optical system, and the fiber beam splitter divides the input light into two paths: the first path of light reaches the coupler through the optical fiber, is input into the on-chip waveguide via end face coupling or grating coupling, and is divided into multiple paths by the on-chip beam splitter, and is radiated into free space via the waveguide grating antenna, and the light radiated into the free space passes through the 4F system composed of a microscope objective and a tube lens;

[0025] S120, irradiating the camera target surface with obliquely incident plane reference light, interfering with the near field amplified by the waveguide grating antenna to form an interference image, and collecting the interference image with a camera, wherein the obliquely incident plane reference light is formed by: the optical fiber beam splitter divides the input light into two paths: the second path of light passes through the optical fiber and the collimating lens to form a plane reference light, and the plane reference light is reflected by a beam splitter placed behind the tube mirror to form an obliquely incident plane reference light;

[0026] S130, obtaining a one-dimensional sinusoidal interference curve of the interference image of each waveguide grating antenna unit through an image processing algorithm, calculating the period of the one-dimensional sinusoidal interference curve and the difference between the peak values ​​of the one-dimensional sinusoidal interference curve of the interference image of each waveguide grating antenna unit, dividing the difference by the period and multiplying it by the wavelength to obtain the magnitude of the phase error between the waveguide grating antenna units.

[0027] The waveguide grating antenna unit interference image mentioned in step S130 refers to the interference image between each antenna unit and the plane reference light in the amplified near field of the waveguide grating antenna.

[0028] The image processing algorithm mentioned in step S130 may include a loop extraction algorithm for intercepting a row element or a column element of the image matrix.

[0029] Since there is a phase error between the waveguide grating antennas, the amplified near field of the waveguide grating antenna mentioned in step S110 can be expressed as (here a waveguide grating antenna with 4 units is taken as an example, and it can be extended to more units):

[0030] (1)

[0031] Where x is the abscissa of the near field after amplification, y is the ordinate of the near field after amplification, j is an imaginary unit, rect represents a rectangular function, λ is the wavelength, W is the width of each unit antenna in the near field after amplification of the waveguide grating antenna, S is the spacing between the near-field images of the waveguide grating antenna units, and L is the width of the near-field image of the waveguide grating antenna unit. , , , They are the near field strength of different waveguide grating antenna units, , , , They are the near-field phases of different waveguide grating antenna units.

[0032] The reference light in step S120 can be expressed as:

[0033] (2)

[0034] Where θ is the incident angle of the reference light after being deflected by the beam splitter, is the reference light intensity.

[0035] The obtained interference intensity image is:

[0036] (3)

[0037] Interference images such as Figure 3 As shown in (a), the normalized one-dimensional cross-sectional view of the interference image of each waveguide grating antenna unit is obtained by using an image processing algorithm, as shown in Figure 3 According to formula 3 and Figure 3 As shown in (b), the one-dimensional cross-sectional view of each waveguide grating antenna unit is a one-dimensional sinusoidal interference curve with a period of P. However, due to the existence of phase error, the peak positions of the one-dimensional sinusoidal interference curves of different waveguide grating antenna units are different. Taking the peak position P1 of the one-dimensional sinusoidal interference curve of the first waveguide grating antenna unit as the reference position, the offsets between the peak values ​​of the one-dimensional sinusoidal interference curves of the second waveguide grating antenna unit, the third waveguide grating antenna unit, and the fourth waveguide grating antenna unit and the peak value of the one-dimensional sinusoidal interference curve of the first waveguide grating antenna unit are △1-2, △1-3, and △1-4. Then the phase error between the second waveguide grating antenna unit, the third waveguide grating antenna unit, the fourth waveguide grating antenna unit and the first waveguide grating antenna unit is △1-2 / P λ、△1-3 / P λ、△1-4 / P λ.

[0038] In one embodiment, the incident angle of the plane reference light can be changed by changing the angle of the beam splitter, thereby adjusting the period of the one-dimensional sinusoidal interference curve to meet the requirement of sufficient sampling of the interference curve by the camera.

[0039] In one embodiment, when calculating the peak position of the one-dimensional sinusoidal interference curve of the waveguide grating antenna unit, a Gaussian function or the like can be used to fit the peak of the one-dimensional sinusoidal interference curve, and then the peak position of the Gaussian function obtained by fitting is used as the peak position of the one-dimensional sinusoidal interference curve, so as to achieve the purpose of improving the peak position accuracy.

[0040] In one embodiment, when the phase between waveguide grating antenna units is controlled by thermo-optical effect or electro-optical effect, the above device and method can be used simultaneously to collect the near-field interference pattern of the waveguide grating antenna and calculate the phase error between the waveguide grating antennas in real time, thereby realizing visual monitoring of the phase error correction between the waveguide grating antennas.

[0041] In one embodiment, the above method may further include: evaluating the phase error level of the waveguide grating antenna. The evaluation process includes measuring the phase error between the waveguide grating antenna units using the method of the embodiment of the present invention. The smaller the phase error between the waveguide grating antenna units, the better the beam quality of the waveguide grating antenna.

[0042] An example is described below: the wavelength of the laser light source is 1550nm, the number of waveguide grating antenna units is 4, and the width of each unit in the near field after amplification of the waveguide grating antenna by the 4F system is 160 microns, the length is 768 microns, and the spacing is 180 microns. The near-field phases of the first waveguide grating antenna unit, the second waveguide grating antenna unit, the third waveguide grating antenna unit, and the fourth waveguide grating antenna unit are -0.0439 wavelengths, -0.1795 wavelengths, 0.0840 wavelengths, and -0.0888 wavelengths, respectively, that is, the phase errors between the second waveguide grating antenna unit, the third waveguide grating antenna unit, the fourth waveguide grating antenna unit and the first waveguide grating antenna unit are -0.1356, 0.2635, and -0.1728 wavelengths.

[0043] The incident angle of the plane reference light is 20 degrees. The far-field image obtained is as follows Figure 3 As shown in (a), the corresponding one-dimensional normalized profile is as follows Figure 3 As shown in (b). Taking the peak position of the one-dimensional normalized profile of the first waveguide grating antenna unit as the reference position, the distances between the peak values ​​of the one-dimensional normalized profiles of the second waveguide grating antenna unit, the third waveguide grating antenna unit, and the fourth waveguide grating antenna unit and the reference position are -0.081 mm, 0.155 mm, and -0.098 mm, and the period P is 0.58 mm. The measured phase errors between the second waveguide grating antenna unit, the third waveguide grating antenna unit, and the fourth waveguide grating antenna unit and the first waveguide grating antenna unit are -0.1397, 0.2672, and -0.169 wavelengths, respectively. The measured results are basically consistent with the actual results, thus realizing the detection of the phase error of the waveguide grating antenna.

[0044] In the description provided herein, a large number of specific details are described. However, it is understood that embodiments of the present invention can be practiced without these specific details. In some instances, well-known methods, structures and techniques are not shown in detail so as not to obscure the understanding of this description.

[0045] Although the present invention has been described according to a limited number of embodiments, it will be apparent to those skilled in the art, with the benefit of the above description, that other embodiments may be envisioned within the scope of the invention thus described. In addition, it should be noted that the language used in this specification is primarily selected for readability and instructional purposes, rather than for the purpose of explaining or limiting the subject matter of the present invention.

Claims

1. A method for detecting phase error of an on-chip waveguide grating antenna, characterized in that: The following steps are involved: S110, using a 4F optical system to amplify the near field of the waveguide grating antenna, and using a camera to receive the amplified near field, wherein the light emitted by the laser light source is first input into a fiber beam splitter via an optical fiber before reaching the 4F optical system, and the fiber beam splitter divides the input light into two paths: the first path of light reaches the coupler through the optical fiber, is input into the on-chip waveguide via end face coupling or grating coupling, and is divided into multiple paths by the on-chip beam splitter, and is radiated into free space via the waveguide grating antenna, and the light radiated into the free space passes through the 4F system composed of a microscope objective and a tube lens; S120, irradiating the camera target surface with obliquely incident plane reference light, interfering with the near field amplified by the waveguide grating antenna to form an interference image, and collecting the interference image with a camera, wherein the obliquely incident plane reference light is formed by: the optical fiber beam splitter divides the input light into two paths: the second path of light passes through the optical fiber and the collimating lens to form a plane reference light, and the plane reference light is reflected by a beam splitter placed behind the tube mirror to form an obliquely incident plane reference light; S130, obtaining a one-dimensional sinusoidal interference curve of the interference image of each waveguide grating antenna unit through an image processing algorithm, calculating the period of the one-dimensional sinusoidal interference curve and the difference between the peak values ​​of the one-dimensional sinusoidal interference curve of each waveguide grating antenna unit, dividing the difference by the period and multiplying it by the wavelength to obtain the magnitude of the phase error between the waveguide grating antenna units.

2. The on-chip waveguide grating antenna phase error detection method according to claim 1, characterized in that: The amplified near field of the waveguide grating antenna is expressed as: (1) Where x is the abscissa of the near field after amplification, y is the ordinate of the near field after amplification, j is an imaginary unit, rect represents a rectangular function, λ is the wavelength, W is the width of each unit antenna in the near field after amplification of the waveguide grating antenna, S is the spacing between the near-field images of the waveguide grating antenna units, and L is the width of the near-field image of the waveguide grating antenna unit. , , , They are the near field strength of different waveguide grating antenna units, , , , They are the near-field phases of different waveguide grating antenna units.

3. The on-chip waveguide grating antenna phase error detection method according to claim 2, characterized in that: The plane reference light is expressed as: (2) Where θ is the incident angle of the plane reference light after being deflected by the beam splitter, is the plane reference light intensity; The obtained interference image is: (3)。 4. The on-chip waveguide grating antenna phase error detection method according to claim 1, characterized in that: The incident angle of the plane reference light is changed by changing the angle of the beam splitter, thereby adjusting the period of the one-dimensional sinusoidal interference curve.

5. The on-chip waveguide grating antenna phase error detection method according to claim 1, characterized in that: When calculating the peak position of the one-dimensional sinusoidal interference curve of the waveguide grating antenna unit, a Gaussian function is used to fit the peak of the one-dimensional sinusoidal interference curve, and then the peak position of the Gaussian function obtained by fitting is used as the peak position of the one-dimensional sinusoidal interference curve.

6. The on-chip waveguide grating antenna phase error detection method according to claim 1, characterized in that: The phase between waveguide grating antenna units is controlled by thermo-optical effect or electro-optical effect, and the above-mentioned on-chip waveguide grating antenna phase error detection method is used simultaneously to collect the near-field interference pattern of the waveguide grating antenna and calculate the phase error between the waveguide grating antennas in real time, so as to realize the visual monitoring of the phase error correction between the waveguide grating antenna units.

7. The on-chip waveguide grating antenna phase error detection method according to claim 1, characterized in that: Also includes: The phase error level of the waveguide grating antenna unit is evaluated. The evaluation process includes using the on-chip waveguide grating antenna phase error detection method to measure the phase error between the waveguide grating antenna units. The smaller the phase error between the waveguide grating antenna units, the better the waveguide grating antenna beam quality.

Images