Large-bandwidth multichannel balanced photoelectric detector

Abstract

A large-bandwidth multichannel balanced photoelectric detector belongs to the technical field of photoelectric detection, and adopts the technical scheme that a plurality of discrete large-bandwidth trans-impedance amplifier arrays are used for amplifying electric signals output by the large-bandwidth photoelectric detector, and a plurality of discrete coupling optical fiber arrays are used for coupling light into a waveguide; while the compactness of the device is maintained, the difficulty and the cost of increasing the number of channels are reduced; the large-bandwidth multi-channel balanced photoelectric detector is realized through the combination of a plurality of large-bandwidth balanced photoelectric detectors with low channel number, and the large-bandwidth multi-channel balanced photoelectric detector has the advantages of low cost, simplicity, high efficiency, compact structure and the like; the large-bandwidth multi-channel balanced photoelectric detector has the advantages of being high in integration degree, low in cost, simple, convenient, high in expansibility and the like, miniaturization and all-solid-state of detection systems such as a laser radar can be achieved, and the large-bandwidth multi-channel balanced photoelectric detector has good performance in real-time, large-range and high-precision distance / speed measurement.

Description

Technical Field

[0001] The present invention belongs to the technical field of optoelectronic detection, and relates to a large-bandwidth multi-channel balanced optoelectronic detector. Background Art

[0002] In traditional lidar systems, a single balanced optoelectronic detector is used for detection, with a single detection direction and a limited detection field of view. To solve this problem, a balanced detector array solution has been proposed, which includes a balanced detector array chip and an array transimpedance amplifier chip to form a hybrid integrated balanced optoelectronic detector array. For small-bandwidth balanced optoelectronic detectors, the placement of the transimpedance amplifier is not restricted by the circuit layout. However, for large-bandwidth balanced optoelectronic detectors, the transimpedance amplifier needs to be strictly selected to meet the electrode spacing in the balanced detector chip. However, currently commercially available transimpedance amplifiers are difficult to simultaneously perform transimpedance amplification on the differential signals of multiple large-bandwidth balanced optoelectronic detectors.

[0003] In the prior art, the literature "Research on Miniaturized High-Isolation Balanced Optoelectronic Detector Array" (Wang Dong, Chen Daiyao, Lu Chaobao, et al. Optical Communication Technology. 2024, 48(5): 97-101.) addressed the problems of large volume and low integration of traditional microwave photon application balanced optoelectronic detectors, and designed a miniaturized, high-isolation balanced optoelectronic detector array based on optoelectronic hybrid integration packaging technology. By integrating multiple balanced photodiode chips and their biasing and matching circuits, the function of four-channel balanced optoelectronic detection was achieved. In this literature, the balanced photodiode chip is composed of two PD chips adjacent to each other on the same wafer with a spacing of 250 μm, and the channel spacing of the balanced optoelectronic detector array is 5 mm (see item 4 in the second paragraph of section 2 of this literature), and this spacing is still relatively large, which is not conducive to high-density integration of the chips. The literature "Design of a Hybrid Integrated 1×4 Array Balanced Optoelectronic Detector" (Electronics Technology (Shanghai), Zhou Lang, Cui Dajian, Huang Xiaofeng, et al. 2023.) addressed the problem of limited observation field of view of a single spot in synthetic aperture lidar, and designed a hybrid integrated 1×4 array balanced optoelectronic detector. The array balanced detection integrated chip, temperature control circuit, and RF circuit were integrated on a multi-channel differential circuit substrate using a common-base hybrid integration technology, where the array balanced detection integrated chip consists of an array balanced detector chip and an array transimpedance amplifier; although the design of the array transimpedance amplifier chip was carried out in this literature, the design and processing costs of this multi-channel transimpedance amplifier are relatively high and the cycle is long.

[0004] None of the above-mentioned literatures can simply and efficiently develop a large-bandwidth multi-channel balanced optoelectronic detector, mainly limited by the number of large-bandwidth transimpedance amplifier arrays. Therefore, it is necessary to design a large-bandwidth multi-channel balanced optoelectronic detector chip to match existing commercially available transimpedance amplifiers and perform optoelectronic hybrid packaging on it to form a large-bandwidth multi-channel balanced optoelectronic detector. Summary of the Invention

[0005] The technical solution of the present invention is used to solve the problems of high cost, difficulty in obtaining, and long development cycle of a transimpedance amplifier array with a large number of channels.

[0006] The present invention solves the above technical problems through the following technical solutions: The present invention provides a multi-channel large-bandwidth balanced photodetector, including: a multi-channel balanced photodetector chip, multiple groups of coupled fiber arrays, and multiple groups of large-bandwidth transimpedance amplifier arrays. The multiple groups of coupled fiber arrays are respectively connected to the input ends of the multi-channel balanced photodetector chip, and the multiple groups of large-bandwidth transimpedance amplifier arrays are respectively connected to the output ends of the multi-channel balanced photodetector chip; the four-channel balanced photodetector chip includes: multiple on-chip structural units arranged side by side, and the on-chip structural unit includes: 2 grating couplers, 1 2×2 multimode interference coupler, 2 photodetectors, multiple silicon waveguides, multiple microstrip lines, and multiple pads; the input ends of the 2 grating couplers are respectively connected to the coupled fibers in the coupled fiber array, and the output ends of the 2 grating couplers respectively use a silicon waveguide to correspond to the 2 input ends of the 2×2 multimode interference coupler. The grating coupler is used to couple the optical signal in the coupled fiber into the silicon waveguide. The 2 output ends of the 2×2 multimode interference coupler respectively use a silicon waveguide to connect to the input ends of the 2 photodetectors. The 2 photodetectors form a balanced photodetection unit for converting the optical signal into an electrical current signal; the photodetector is connected to 3 pads through 3 microstrip lines. The pads are used to connect to the large-bandwidth transimpedance amplifier array, and the electrical current signal is finally transmitted to the large-bandwidth transimpedance amplifier array through the pads, and then the large-bandwidth transimpedance amplifier array converts the electrical current signal into an output voltage signal.

[0007] Further, the coupled fiber array is composed of multiple coupled fibers arranged at equal intervals, and is used to be aligned and connected with the grating coupler in the multi-channel balanced photodetector chip to achieve low-loss transmission of the optical signal.

[0008] Further, the grating coupler is composed of 25 gratings with a period of 630 nm, and is used to transmit the signal light and the local oscillator light in the coupled fiber into the silicon waveguide.

[0009] Further, the center distance between two adjacent grating couplers is 250 μm.

[0010] Further, the 2×2 multimode interference coupler is used to mix the input signal light and local oscillator light, and its splitting ratio is 1:1.

[0011] Further, the photodetector uses a PIN-type germanium-silicon photodetector, the polarity of the PN junction is PNP, and the P poles, N poles, and P poles of the output ends of the two photodetectors are respectively connected to three pads through three microstrip lines. Further, the grating coupler, 2×2 multimode interference coupler, and photodetector are all fabricated using CMOS technology.

[0012] Further, the model of the large-bandwidth transimpedance amplifier array is MATA-006406.

[0013] Further, the material of the microstrip line is gold.

[0014] Further, the pitch of the equally-spaced arranged coupling optical fibers is 250 μm.

[0015] The beneficial effects of the present invention are as follows: The technical solution of the present invention uses multiple discrete large-bandwidth transimpedance amplifier arrays to amplify the electrical signals output by the large-bandwidth photodetectors, and uses multiple discrete coupling optical fiber arrays to couple light into the waveguide. While maintaining the device compactness, it reduces the difficulty and cost of increasing the number of channels; a large-bandwidth multi-channel balanced photodetector is realized through a combination of multiple low-channel large-bandwidth balanced photodetectors, which has the advantages of low cost, simplicity and high efficiency, and compact structure; the large-bandwidth multi-channel balanced photodetector of the present invention has the advantages of high integration level, low cost, simplicity and convenience, and high scalability, and can realize the miniaturization and all-solid state of detection systems such as lidar, and has good performance in real-time, large-range, high-precision distance / velocity measurement. Description of the Drawings

[0016] Figure 1 is a structural block diagram of a four-channel large-bandwidth balanced photodetector according to an embodiment of the present invention; Figure 2 is an arrangement diagram of the on-chip structural units of a multi-channel balanced photodetector chip according to an embodiment of the present invention; Figure 3 is a layout diagram of a four-channel balanced photodetector chip according to an embodiment of the present invention; Figure 4 is a frequency response curve diagram of a multi-channel balanced photodetector chip according to an embodiment of the present invention. Detailed Embodiments

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0018] The technical solutions of the present invention will be further described below in conjunction with the accompanying drawings of the specification and specific embodiments: Embodiment 1 As Figure 1 shown, the embodiment of the present invention provides a four-channel large-bandwidth balanced photodetector. The four-channel large-bandwidth balanced photodetector includes: a four-channel balanced photodetector chip 1, two groups of coupled fiber arrays 2, and two groups of large-bandwidth transimpedance amplifier arrays 3. The two groups of coupled fiber arrays 2 are respectively connected to the input ends of the four-channel balanced photodetector chip 1, and the two groups of large-bandwidth transimpedance amplifier arrays 3 are respectively connected to the output ends of the four-channel balanced photodetector chip 1.

[0019] The four-channel balanced photodetector chip 1 includes: four on-chip structural units arranged side by side.

[0020] As Figure 2 shown, it is the layout diagram of the on-chip structural unit. The on-chip structural unit includes: two grating couplers 10, one 2×2 multimode interference coupler 11, two photodetectors 12, multiple silicon waveguides 13, multiple microstrip lines 14, and multiple pads 15. The input ends of the two grating couplers 10 are respectively connected to the coupled fibers in the coupled fiber array 2. The output ends of the two grating couplers 10 respectively use one silicon waveguide 13 to be correspondingly connected to the two input ends of the 2×2 multimode interference coupler 11. The grating coupler 10 is used to couple the optical signals in the coupled fiber into the silicon waveguide 13. The two output ends of the 2×2 multimode interference coupler 11 respectively use one silicon waveguide 13 to be connected to the input ends of the two photodetectors 12. The two photodetectors 12 form a balanced photodetection unit. The photodetector 12 uses a PIN-type germanium-silicon photodetector, and the polarity of the PN junction is PNP. The P poles, N poles, and P poles of the output ends of the two photodetectors 12 are respectively connected to three pads 15 through three microstrip lines 14. The pads 15 are used to connect to the large-bandwidth transimpedance amplifier array 3. As Figure 3 shown, it is the layout layout of the four-channel balanced photodetector chip of the present invention.

[0021] The metal electrodes of the PIN-type GeSi photodetector are disposed on the doped silicon layer and the doped germanium layer, forming three electrodes in total, which are used to convert optical signals into current signals. The current signals are output to the pad 15 through the P electrode, the N electrode, and the P electrode, and finally transmitted to the large-bandwidth transimpedance amplifier array 3, and then the large-bandwidth transimpedance amplifier array 3 converts the current signals into output voltage signals.

[0022] The photodetector 12 described above may also be a photodetector made of InP or InGaAsP materials.

[0023] Preferably, the material of the microstrip line 14 is gold.

[0024] The 2×multiple-mode interference coupler 11 is used for mixing the input signal light and the local oscillator light, and its splitting ratio is 1:1.

[0025] The grating coupler 10, the 2×multiple-mode interference coupler 11, and the photodetector 12 are all fabricated using CMOS technology.

[0026] The grating coupler 10 is composed of 25 gratings with a period of 630 nm, which is used to transmit the signal light and the local oscillator light in the coupling optical fiber into the silicon waveguide 13. The center distance between two adjacent grating couplers 10 is 250 μm, so as to perform optical packaging using a coupling optical fiber array.

[0027] The coupling optical fiber array 2 in this embodiment is composed of four equally spaced coupling optical fibers, which are used to align and connect with the grating coupler in the four-channel balanced photodetector chip 1 to achieve low-loss transmission of optical signals; preferably, the spacing between the four equally spaced coupling optical fibers is 250 μm.

[0028] The optional models of the large-bandwidth transimpedance amplifier array 12 are: MATA-006406, ISG-T3223, MATA-006801, MATA-009806, GX36220, GX32222, or ADA4351-2.

[0029] Preferably, the model of the large-bandwidth transimpedance amplifier array 12 is MATA-006406. This model of the large-bandwidth transimpedance amplifier array has a total of four pairs of electrical pins for connecting the output electrical signals of the photodetector. The second and third pairs of pins are selected to connect to the electrodes of the first group of balanced photodetectors in the multi-channel balanced photodetector chip. The electrodes of the second group of balanced photodetectors are also connected in the same way and connected to the second transimpedance amplifier array chip; the distance between the two transimpedance amplifiers is 3 mm.

[0030] The large-bandwidth balanced photodetector array and the large-bandwidth transimpedance amplifier array are connected by gold wires. The large-bandwidth transimpedance amplifier array is kept aligned, and the gold wires are kept parallel or approximately parallel and short and straight. The large-bandwidth transimpedance amplifier array is integrated on a circuit board. The technical solution of the present invention is applicable to balanced photodetectors with different pitches and different numbers, arranged along the chip edge.

[0031] As Figure 4 shown, a 3dB electrical bandwidth test is performed on one of the photodetectors in the balanced detector chip by a SiYi vector network analyzer to form a frequency response curve. Three points near the 3dB bandwidth position and the starting point in the curve are respectively collected. The frequency of the starting point is 1GHz, and the frequencies near the 3dB position are 27.9225GHz, 30.241GHz, and 32.0601GHz respectively. Subtracting the frequency of the starting point from these three frequencies respectively gives 26.9225GHz, 29.241GHz, and 31.0601GHz, all of which are greater than 20GHz. Therefore, the characteristic of the large bandwidth is that the 3dB electrical frequency response range is not less than 20GHz.

[0032] The difference between the technical solution of the present invention and the prior art solution is that, since the large-bandwidth balanced photodetector has high requirements for the circuit and the gold wires need to be kept as short straight lines and parallel as possible, the prior art designs the photodetector to have a large pitch to meet the arrangement of the transimpedance amplifier. Although high-frequency packaging can be carried out, the required chip size is very large in this way; or it is connected to the chip through a commercial multi-channel large-bandwidth transimpedance amplifier. However, the more channels there are, the much more expensive it is and it is difficult to purchase imported ones. If designed by oneself, the difficulty is great and the cycle is long, which is not conducive to the mass production of large-bandwidth multi-channel balanced photodetectors. The technical solution of the present invention avoids these two problems. The large-bandwidth multi-channel balanced photodetector is divided into multiple groups, with two in each group, and is hybrid packaged with a coupling fiber array and a large-bandwidth transimpedance amplifier with a smaller number of channels. A packaging space is left at a certain distance between each group. Through this spaced multi-channel arrangement, the multi-channel arrangement of the large-bandwidth balanced photodetector can be realized, and it also has the advantages of low cost and simple operation.

[0033] The pitch of the coupled fiber array is 250 μm, and the pitch of the grating coupler is set to 250 μm. There are four input optical ports in a group, so a four-channel coupled fiber array is required. A pair of optical ports respectively input the signal light and the local oscillator light, which enter the 2×2 multimode interference coupler for mixing. The two output optical signals respectively enter two photodetectors, and the output electrical signals respectively enter the transimpedance amplifiers. Since there are two balanced photodetectors, the large-bandwidth transimpedance amplifier array contains two transimpedance amplifiers, and there are a total of 6 electrode interfaces. The distance between the two transimpedance amplifiers is 425 μm, and the electrode pitch of each transimpedance amplifier is 200 μm. When the pitch between the balanced photodetectors in the chip is inconsistent with the pitch between the transimpedance amplifiers, only two pairs of balanced photodetectors can be connected, so the channels are limited. In order to achieve a larger number of channels of balanced photodetectors, while making full use of space and keeping the bandwidth unaffected and maintaining consistency, this solution connects multiple transimpedance amplifiers in parallel and aligns them to increase the distance between every two pairs of balanced photodetectors to leave some space for the packaging of the transimpedance amplifiers. The direct multi-channel arrangement is limited by the number of channels of the transimpedance amplifier. This solution divides the high-channel number into multiple low-channel number balanced photodetectors, and a large-bandwidth multi-channel balanced photodetector can be achieved through the arrangement of multiple pairs of balanced photodetectors and low-cost hybrid optoelectronic packaging.

[0034] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A multi-channel large-bandwidth balanced photodetector, characterized in that Including: A multi-channel balanced photodetector chip (1), multiple groups of coupled fiber arrays (2), and multiple groups of large-bandwidth transimpedance amplifier arrays (3). The multiple groups of coupled fiber arrays (2) are respectively connected to the input ends of the multi-channel balanced photodetector chip (1), and the multiple groups of large-bandwidth transimpedance amplifier arrays (3) are respectively connected to the output ends of the multi-channel balanced photodetector chip (1). The four-channel balanced photodetector chip (1) includes: multiple on-chip structural units arranged side by side. The on-chip structural unit includes: 2 grating couplers (10), 1 2×2 multimode interference coupler (11), 2 photodetectors (12), multiple silicon waveguides (13), multiple microstrip lines (14), and multiple pads (15). The input ends of the 2 grating couplers (10) are respectively connected to the coupled fibers in the coupled fiber array (2). The output ends of the 2 grating couplers (10) respectively use one silicon waveguide (13) to be correspondingly connected to the 2 input ends of the 2×2 multimode interference coupler (11). The grating coupler (10) is used to couple the optical signal in the coupled fiber into the silicon waveguide (13). The 2 output ends of the 2×2 multimode interference coupler (11) respectively use one silicon waveguide (13) to be connected to the input ends of the 2 photodetectors (12). The 2 photodetectors (12) form a balanced photodetection unit for converting the optical signal into an electric current signal. The photodetector (12) is connected to 3 pads (15) through 3 microstrip lines (14). The pad (15) is used to connect to the large-bandwidth transimpedance amplifier array (3). The electric current signal is finally transmitted to the large-bandwidth transimpedance amplifier array (3) through the pad (15), and then the large-bandwidth transimpedance amplifier array (3) converts the electric current signal into an output voltage signal.

2. The multi-channel large-bandwidth balanced photodetector according to claim 1, wherein The coupled fiber array (2) is composed of multiple coupled fibers arranged at equal intervals, and is used to be aligned and connected with the grating coupler in the multi-channel balanced photodetector chip (1) to achieve low-loss transmission of optical signals.

3. The multi-channel large-bandwidth balanced photodetector according to claim 1, wherein The grating coupler (10) is composed of 25 gratings with a period of 630 nm, and is used to transmit the signal light and local oscillator light in the coupled fiber into the silicon waveguide (13).

4. The multi-channel large-bandwidth balanced photodetector according to claim 1, wherein The center distance between two adjacent grating couplers (10) is 250 μm.

5. The multi-channel large-bandwidth balanced photodetector according to claim 1, characterized in that The 2×2 multimode interference coupler (11) is used for mixing the input signal light and local oscillator light, and its splitting ratio is 1:

1.

6. The multi-channel large-bandwidth balanced photodetector according to claim 1, wherein The photodetector (12) uses a PIN-type germanium-silicon photodetector, the polarity of the PN junction is PNP, and the P poles, N poles, and P poles of the output ends of the 2 photodetectors (12) are respectively connected to 3 pads (15) through 3 microstrip lines (14).

7. The multi-channel large-bandwidth balanced photodetector according to claim 1, wherein The grating coupler (10), 2×2 multimode interference coupler (11), and photodetector (12) are all manufactured by using CMOS technology.

8. The multi-channel large-bandwidth balanced photodetector according to claim 1, wherein The model of the large-bandwidth transimpedance amplifier array (12) is MATA-006406.

9. The multi-channel large-bandwidth balanced photodetector according to claim 1, wherein The material of the microstrip line (14) is gold.

10. The multi-channel large-bandwidth balanced photodetector according to claim 2, wherein The distance between the coupled fibers arranged at equal intervals is 250 μm.

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