Transmit-receive integrated optical phased array chip based on grating lobe demodulation

Abstract

This invention proposes an integrated optical phased array chip based on grating lobe demodulation, belonging to the field of photonic integrated circuit technology. It includes: an optical input terminal, a multimode interferometric beamsplitter, a transmit phase shifter array, a transmit grating antenna array, a receive grating antenna array, a receive phase shifter array, an equal-length waveguide array, a star coupler, and a receive channel. The multimode interferometric beamsplitter, star coupler, transmit and receive phase shifter arrays, a pair of coaxial arrays with mismatched transmit and receive grating antenna arrays, and equal-length waveguide arrays constitute a deeply coupled and indispensable collaboratively designed chip structure, realizing parallel transceiver functionality based on grating lobe demodulation. The proposed integrated optical phased array chip based on grating lobe demodulation demodulates the main lobe and grating lobes to different channels, solving the problem that traditional OPAs cannot utilize grating lobe energy, realizing parallel transceiver ranging based on grating lobe demodulation, reducing control complexity, and improving optical energy utilization efficiency.

Description

Technical Field

[0001] This invention relates to the field of photonic integrated circuit technology, and more specifically, to a transceiver integrated optical phased array chip based on gate lobe demodulation. Background Technology

[0002] Integrated optical phased arrays (OPA) achieve beam scanning without mechanical movement by controlling the phase of light waves emitted by multiple optical antennas on a single chip. They offer significant advantages such as small size, high stability, and fast scanning speed, making them core components of next-generation solid-state lidar and beam control systems. OPA systems achieve high-resolution sensing and strong anti-interference capabilities by actively emitting laser pulses and analyzing the echo signals. However, most OPAs suffer from the fundamental limitation of single-point scanning, resulting in low frame rates and an inability to simultaneously acquire information from multiple points in space.

[0003] On the other hand, in the traditional design philosophy of OPAs, grating lobes are considered a harmful interference phenomenon. When the spacing between optical antenna elements is greater than half a wavelength, grating lobes with an intensity comparable to the main lobe will be generated in non-target directions, causing energy dispersion and spurious signals. Therefore, existing solutions generally focus on suppressing or eliminating grating lobes, with main methods including: using non-uniform antenna array arrangements, strictly limiting the antenna spacing to less than half a wavelength, or using complex weighting algorithms. These methods either sacrifice antenna aperture and scanning range or significantly increase the complexity of design and control.

[0004] Furthermore, existing integrated OPA transceiver solutions can only achieve single-point scanning, which limits the performance of the OPA; and they generally use designs with non-equidistant optical paths, requiring different voltage values ​​to be stored for the phase shifter of the transmitting section for different wavelengths, making the calibration system very complex.

[0005] Therefore, there is an urgent need for a new type of OPA chip architecture to break through the limitations of the traditional transmit / receive isolation mode, thereby reducing system control complexity and improving energy utilization efficiency. Summary of the Invention

[0006] To address the problems in the background technology, the present invention provides an integrated optical phased array chip based on grating lobe demodulation, which solves the defects of existing optical phased array chips.

[0007] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0008] An integrated optical phased array chip based on grating lobe demodulation includes:

[0009] The optical input terminal is used to receive the initial optical signal input to the chip;

[0010] A multimode interference beam splitter, whose input end is optically connected to the optical input end, is used to split the initial optical signal into N first optical signals, where N is an integer greater than 1;

[0011] The transmitter phase shifter array includes N independently adjustable transmitter phase shifter units. The input terminal of each transmitter phase shifter unit is optically connected to the corresponding output terminal of the multimode interference beam splitter, and is used to perform phase modulation on the N first optical signals to output N second optical signals.

[0012] A transmitting grating antenna array comprises N transmitting grating antennas arranged periodically at fixed intervals. The input end of each transmitting grating antenna is optically connected to the output end of a transmitting phase shifter unit, for radiating the N second optical signals to the far field, forming a transmitted light spot pattern containing a main lobe and at least one grating lobe; the main lobe and the at least one grating lobe correspond to different diffraction orders generated by the transmitting grating antenna array in the far field.

[0013] A receiving grating antenna array comprises N receiving grating antennas arranged periodically at a fixed interval. The spacing of the receiving grating antenna array is different from that of the transmitting grating antenna array. The receiving grating antenna array is used to receive optical signals returned from a far-field target and corresponding to different diffraction order directions, and couple them back into the chip to form N third optical signals.

[0014] A receiving phase shifter array includes N independently adjustable receiving phase shifter units. The input terminal of each receiving phase shifter unit is optically connected to the output terminal of a receiving grating antenna, and is used to perform phase modulation on the N third optical signals to output N fourth optical signals.

[0015] An equal-length waveguide array comprises N waveguides of equal optical length, with the input end of each waveguide optically connected to the output end of one of the receiving phase shifter units.

[0016] A star coupler, the input end of which is optically connected to the output ends of N waveguides of the equal-length waveguide array, is used to perform interference synthesis and spatial demultiplexing of the N fourth optical signals; the star coupler is formed by a pair of opposing arc-shaped boundaries and a pair of opposing straight boundaries, wherein the first arc-shaped boundary is a short arc, the second arc-shaped boundary is a long arc, and the pair of straight boundaries are non-parallel.

[0017] M receiving channels, the input ends of which are optically connected to the output end of the star coupler, where M is an integer greater than 1, and the M receiving channels correspond one-to-one with the main lobe and the at least one grating lobe in the emitted light spot pattern; the input ends of the M receiving channels are arranged along the short arc of the star coupler;

[0018] The input terminal of the inth receiving channel in the M receiving channels is positioned on the short arc according to a preset mapping relationship, such that the echo signal from the direction corresponding to the diffraction order corresponding to the inth receiving channel is coupled to the inth receiving channel; the mapping relationship is jointly determined by the spacing of the transmitting grating antenna array, the spacing of the receiving grating antenna array, the waveguide spacing of the equal-length waveguide array, the diffraction order, the operating wavelength, and the effective refractive index of the star coupler, so as to achieve spatial separation and demodulation of the main lobe and the at least one grating lobe echo signal; in is a positive integer from 1 to M, representing the receiving channel number.

[0019] Preferably, the connection position of the input terminal of the inth receiving channel among the M receiving channels on the short arc is determined by the following relationship: the angle between the direction of the line connecting this connection position to the geometric center of the long arc and the direction of the central symmetry axis of the star coupler. The sine value satisfies:

[0020] Where m is the diffraction order. Where d is the operating wavelength, d1 is the spacing between the transmitting grating antenna arrays, d2 is the spacing between the receiving grating antenna arrays, d is the waveguide spacing of the equal-length waveguide array, and n is the wavelength. slab is the effective refractive index of the star coupler.

[0021] Preferably, the output of each of the M receiving channels integrates a photodetector.

[0022] The beneficial effects of this invention are as follows:

[0023] (1) A "spatial optical path difference locking" mechanism determined by the chip's own physical structure is adopted. Through precise design, a fixed difference is made between the spacing of the transmitting grating array and the receiving grating array. Based on this, back-end interference processing is performed through a waveguide array of equal length and a star coupler with a specific geometry. This allows echo signals from different spatial angles (corresponding to different diffraction orders) to automatically accumulate different and fixed total optical path differences within the chip. This eliminates the need for any high-speed active switches, multi-wavelength laser sources, or precision filters, reducing control complexity and improving optical energy utilization efficiency.

[0024] (2) The introduction of the equal-length waveguide array is not a simple signal connection, but a key part of realizing this systematic design: it ensures that the optical path from all receiving grating antennas to the input of the star coupler is strictly equal. It avoids the linear phase tilt related to the spatial angle introduced by the receiving grating array, matches the focusing characteristics of the star coupler with non-parallel straight boundary, and can separate signals at different angles to different output ports without crosstalk. The "equal-length waveguide array" and the "star coupler" together constitute a unique and deterministic physical mapping relationship for converting spatial angle information into waveguide port information;

[0025] (3) By controlling specific high-order diffraction orders (grating lobes) within the effective field of view, making them, together with the main lobe, a stable and controllable parallel transmission beam, parallel transmission and reception ranging based on grating lobe demodulation is realized. The receiver demodulates echo signals from different directions (main lobe and each grating lobe) in parallel to independent physical channels. This means that, without increasing the number of laser sources or changing the total number of antenna elements N, the number of effective spatial detection channels of the system jumps from the traditional 1 (main lobe only) to M (main lobe and each grating lobe); the waste of grating lobe energy is avoided, and the complexity requirements of the driving circuit and signal processing are also reduced. Attached Figure Description

[0026] To facilitate understanding of the invention, it will be described in more detail with reference to the specific embodiments shown in the accompanying drawings. These drawings depict only typical embodiments of the invention and should not be considered as limiting the scope of protection of the invention.

[0027] Figure 1 This is a schematic diagram of the integrated optical phased array chip structure based on grating lobe demodulation provided in an embodiment of the present invention;

[0028] Figure 2 This is a schematic diagram of the internal structure of the transceiver integrated chip provided in an embodiment of the present invention. Detailed Implementation

[0029] Embodiments of the present invention are described below with reference to the accompanying drawings to enable those skilled in the art to better understand and implement the invention. However, the listed embodiments are not intended to limit the invention. Unless otherwise specified, the embodiments and technical features described below can be combined with each other, wherein identical components are denoted by the same reference numerals. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0030] Please refer to Figure 1 as well as Figure 2 , Figure 1 This is a schematic diagram of the integrated optical phased array chip structure based on grating lobe demodulation provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the internal structure of the transceiver integrated chip provided in an embodiment of the present invention.

[0031] like Figure 1The diagram shows a schematic of an integrated optical phased array chip structure based on grating lobe demodulation. The chip includes: an optical input terminal for receiving the initial optical signal input to the chip; a multimode interference beamsplitter, whose input terminal is optically connected to the optical input terminal, for splitting the initial optical signal into N first optical signals, where N is an integer greater than 1; a transmit phase shifter array containing N independently adjustable transmit phase shifter units, the input terminal of each transmit phase shifter unit being optically connected to the corresponding output terminal of the multimode interference beamsplitter, for performing phase modulation on the N first optical signals to output N second optical signals; and a transmit grating antenna array containing N transmit grating antennas arranged periodically at fixed intervals, the input terminal of each transmit grating antenna being optically connected to a transmit grating antenna. The output of the phase shifter unit is optically connected to radiate N second optical signals to the far field, forming an emitted light spot pattern containing one main lobe and at least one grating lobe. The main lobe and at least one grating lobe correspond to different diffraction orders generated by the emitting grating antenna array in the far field. The receiving grating antenna array contains N receiving grating antennas arranged periodically at a fixed interval. The spacing of the receiving grating antenna array is different from that of the emitting grating antenna array. The receiving grating antenna array is used to receive optical signals returning from the far-field target and corresponding to different diffraction order directions, and couple them back into the chip to form N third optical signals. The receiving phase shifter array contains N independently adjustable receiving phase shifter units. The input of each receiving phase shifter unit is connected to a... The output of a receiving grating antenna is optically connected to modulate the phase of N third optical signals to output N fourth optical signals. An equal-length waveguide array comprises N waveguides of equal optical length, with the input of each waveguide optically connected to the output of a receiving phase shifter unit. A star coupler, whose input is optically connected to the output of the N waveguides of the equal-length waveguide array, is used to perform interferometric synthesis and spatial demultiplexing of the N fourth optical signals. The star coupler is formed by a pair of opposing arc-shaped boundaries and a pair of opposing straight boundaries, where the first arc-shaped boundary is a short arc, the second arc-shaped boundary is a long arc, and the pair of straight boundaries are non-parallel. M receiving channels, whose inputs are optically connected to the output of the star coupler, where M is an integer greater than 1. Furthermore, each of the M receiving channels corresponds one-to-one with the main lobe and at least one grating lobe in the transmitted light spot pattern; the input ends of the M receiving channels are arranged along the short arc of the star coupler; the position of the input end of the in-th receiving channel on the short arc satisfies a preset mapping relationship, so that the echo signal from the direction corresponding to the diffraction order corresponding to the in-th receiving channel is coupled to the in-th receiving channel; the mapping relationship is jointly determined by the spacing of the transmitting grating antenna array, the spacing of the receiving grating antenna array, the waveguide spacing of the equal-length waveguide array, the diffraction order, the operating wavelength, and the effective refractive index of the star coupler, so as to achieve spatial separation and demodulation of the echo signals of the main lobe and at least one grating lobe; in is a positive integer from 1 to M, representing the receiving channel number.

[0032] In the chip, a multimode interferometric beamsplitter, a star coupler, a phase shifter region, a pair of coaxial array mismatched receiving and transmitting grating antenna arrays, and an equal-length array waveguide constitute a deeply coupled and indispensable collaborative design to achieve parallel transceiver functionality based on grating lobe demodulation. First, the optical signal is routed to multiple paths by the multimode interferometric beamsplitter, then the phase shifter region modulates the phase of each optical signal, and then the transmitting region, which can simultaneously emit multiple angled light spots containing grating lobes, is transmitted to the far field. Then, the receiving grating antenna array couples optical signals at different angles to the chip, and the phase shifter region modulates the phase of each optical signal. Then, the equal-length array waveguide and the star coupler demodulate the main lobe and grating lobe to different channels. Finally, the detector integrated at the output of the receiving channel acquires the optical signals carrying different distance information.

[0033] See Figure 2 Firstly, according to the optical phased array diffraction theory, the emission region emits multiple directions including the main lobe and the grating lobe. (Not shown in the image) The light spot:

[0034] ,

[0035] in, The modulation phase difference between phase shifter units in the transmitter phase shifter array. For the operating wavelength, d1 is the refractive index of the material in the outer space of the transmitting grating antenna array, m is the diffraction order.

[0036] For the receiving part, different receiving channel locations mean different The receiving channel can receive signals from different directions. The light spot is achieved by utilizing the principle of an arrayed waveguide grating of a star coupler:

[0037] ,

[0038] in For light from When the position is emitted, the phase difference between adjacent array waveguides connected to the star coupler. denoted as the effective refractive index of the star coupler, and d is the waveguide spacing of the equal-length waveguide array connected to the star coupler.

[0039] Based on the optical phased array diffraction theory and the principle of arrayed waveguide gratings, we can obtain... With different directions Corresponding relationships:

[0040] ,

[0041] Where d2 is the spacing of the receiving grating antenna array. To receive the modulation phase difference between phase shifter units in the phase shifter array.

[0042] To ensure that each receiving channel can always receive the corresponding diffraction order spot during beam deflection, it is necessary to ensure that... Not following and The values ​​change, therefore d1≠d2 needs to be set during calibration.

[0043] Through derivation, it can be concluded that the connection position of the input terminal of the inth receiving channel among the M receiving channels on the short arc of the star coupler is determined by the following relationship: the angle between the direction of the line connecting this connection position to the geometric center of the long arc of the star coupler and the direction of the central axis of symmetry of the star coupler. The sine value satisfies:

[0044] Where m is the diffraction order. Where d is the operating wavelength, d1 is the spacing between the transmitting grating antenna arrays, d2 is the spacing between the receiving grating antenna arrays, d is the waveguide spacing of the equal-length waveguide array, and n is the wavelength. slab is the effective refractive index of the star coupler.

[0045] Based on the above formula, it is achieved that each light spot can only receive one of the directions emitted from the transmitting area, thus realizing the parallel transmission and reception function based on grating lobe demodulation. This solves the problem that FMCW radar based on traditional OPA cannot utilize grating lobe energy and realizes parallel transmission and reception ranging based on grating lobe demodulation.

[0046] It is worth noting that this invention overcomes the traditional technical bias of needing to suppress grating lobes, employing a "spatial optical path difference locking" mechanism determined by the chip's own physical structure. Through precise design, the spacing between the transmitting grating array and the receiving grating array is kept constant. Based on this, back-end interference processing is performed using an equal-length waveguide array and a star coupler with a specific geometry. This allows echo signals from different spatial angles (corresponding to different diffraction orders) to automatically accumulate different, fixed total optical path differences within the chip. This eliminates the need for any high-speed active switches, multi-wavelength laser sources, or precision filters, reducing control complexity and improving optical energy utilization efficiency. The introduction of the equal-length waveguide array is not simply a signal connection, but a crucial element in achieving this systematic design: it ensures that the optical path from all receiving grating antennas to the input of the star coupler is strictly equal. This avoids the spatial angle-dependent linear phase tilt introduced by the receiving grating array, matches the focusing characteristics of the non-parallel straight-line boundary of the star coupler, and enables signals from different angles to be separated to different output ports without crosstalk. The "equal-length waveguide array" and the "star coupler" together constitute a unique and deterministic physical mapping relationship for converting spatial angle information into waveguide port information. By controlling specific higher-order diffraction orders (grating lobes) within the effective field of view, they become stable and controllable parallel transmission beams together with the main lobe, realizing parallel transmission and reception ranging based on grating lobe demodulation. The receiver demodulates echo signals from different directions (main lobe and each grating lobe) in parallel to independent physical channels. This means that, without increasing the number of laser sources or changing the total number of antenna elements N, the number of effective spatial detection channels of the system jumps from the traditional 1 (main lobe only) to M (main lobe and each grating lobe); avoiding the waste of grating lobe energy, and also reducing the complexity requirements of the driving circuit and signal processing.

[0047] In another embodiment of the invention, a photodetector is integrated at the output of each of the M receiving channels. The set of diffraction orders effectively utilized in the emitted light spot pattern is {m}. i |i=1,2,...,M}, where m i The set of diffraction orders is an integer, and contains at least one zero order and one non-zero order. i} is a continuous symmetric set. Specifically, when the set is {-1,0,+1}, the number of receiving channels M=3.

[0048] In another embodiment of the invention, the short arc of the star coupler is a part of a Rowland circle, and the long arc is another circular arc with a larger radius of curvature that is confocal with the Rowland circle, and the radius of the long arc is twice the radius of the short arc. The equal-length waveguide array is arranged in a fan shape in space, and its N output terminals are arranged at equal intervals along the long arc of the star coupler.

[0049] The various embodiments in this invention are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0050] The embodiments described above are merely preferred embodiments of the present invention. The terms "in one embodiment," "in another embodiment," "in yet another embodiment," or "in still another embodiment" used in this specification all refer to one or more of the same or different embodiments according to this disclosure. Ordinary variations and substitutions made by those skilled in the art within the scope of the present invention should be included within the protection scope of the present invention.

Claims

1. A transceiver integrated optical phased array chip based on grating lobe demodulation, characterized in that, include: The optical input terminal is used to receive the initial optical signal input to the chip; A multimode interference beam splitter, whose input end is optically connected to the optical input end, is used to split the initial optical signal into N first optical signals, where N is an integer greater than 1; The transmitter phase shifter array includes N independently adjustable transmitter phase shifter units. The input terminal of each transmitter phase shifter unit is optically connected to the corresponding output terminal of the multimode interference beam splitter, and is used to perform phase modulation on the N first optical signals to output N second optical signals. The transmitting grating antenna array comprises N transmitting grating antennas arranged periodically at a fixed interval. The input end of each transmitting grating antenna is optically connected to the output end of one of the transmitting phase shifter units, and is used to radiate the N second optical signals to the far field to form a transmitting light spot pattern containing a main lobe and at least one grating lobe. The main lobe and the at least one grating lobe respectively correspond to different diffraction orders generated by the transmitting grating antenna array in the far field; A receiving grating antenna array comprises N receiving grating antennas arranged periodically at a fixed interval. The spacing of the receiving grating antenna array is different from that of the transmitting grating antenna array. The receiving grating antenna array is used to receive optical signals returned from a far-field target and corresponding to different diffraction order directions, and couple them back into the chip to form N third optical signals. A receiving phase shifter array includes N independently adjustable receiving phase shifter units. The input terminal of each receiving phase shifter unit is optically connected to the output terminal of a receiving grating antenna, and is used to perform phase modulation on the N third optical signals to output N fourth optical signals. An equal-length waveguide array comprises N waveguides of equal optical length, with the input end of each waveguide optically connected to the output end of one of the receiving phase shifter units. A star coupler, whose input end is optically connected to the output ends of N waveguides of the equal-length waveguide array, is used to perform interferometric synthesis and spatial demultiplexing of the N fourth optical signals; the star coupler is formed by a pair of opposing arc-shaped boundaries and a pair of opposing straight boundaries, wherein the first arc-shaped boundary is a short arc and the second arc-shaped boundary is a long arc, and the pair of straight boundaries are non-parallel; the equal-length waveguide array is arranged in a fan shape in space, and the N output ends of the equal-length waveguide array are arranged at equal intervals along the long arc of the star coupler; M receiving channels, the input ends of which are optically connected to the output end of the star coupler, where M is an integer greater than 1, and the M receiving channels correspond one-to-one with the main lobe and the at least one grating lobe in the emitted light spot pattern; the input ends of the M receiving channels are arranged along the short arc of the star coupler; The position of the input terminal of the inth receiving channel in the M receiving channels on the short arc satisfies a preset mapping relationship, so that the echo signal from the direction corresponding to the diffraction order corresponding to the inth receiving channel is coupled to the inth receiving channel. The mapping relationship is determined by the spacing of the transmitting grating antenna array, the spacing of the receiving grating antenna array, the waveguide spacing of the equal-length waveguide array, the diffraction order, the operating wavelength, and the effective refractive index of the star coupler, so as to achieve spatial separation and demodulation of the main lobe and the echo signal of at least one grating lobe. in is a positive integer from 1 to M, representing the receive channel number.

2. The integrated optical phased array chip based on grating lobe demodulation according to claim 1, characterized in that, The connection position of the input terminal of the *in*th receiving channel among the M receiving channels on the short arc is determined by the following relationship: the angle between the direction of the line connecting this connection position to the geometric center of the long arc and the direction of the central symmetry axis of the star coupler. The sine value satisfies: ， Where m is the diffraction order. Where d is the operating wavelength, d1 is the spacing between the transmitting grating antenna arrays, d2 is the spacing between the receiving grating antenna arrays, d is the waveguide spacing of the equal-length waveguide array, and n is the wavelength. slab is the effective refractive index of the star coupler.

3. The transceiver integrated optical phased array chip based on grating lobe demodulation according to claim 2, characterized in that, Each of the M receiving channels integrates a photodetector at its output terminal.

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