Photonic analog-to-digital conversion system and chip based on optical trapping principle

Abstract

The application provides a photonic analog-digital conversion system and chip based on an optical capture principle. The photonic analog-digital conversion chip uses multiple continuous light to load a sampled analog signal and controls each analog signal to enter an optical capture unit with an equal time interval through an optical delay line to realize the discretization of the signal in the time domain. The application uses the optical capture unit to generate an optical sampling pulse sequence with an amplitude modulated by the sampled signal, replaces the mode-locked laser with continuous laser, and realizes a monolithic integrated photonic analog-digital conversion chip by using a heterogeneous integration process. The application adopts the design of multiple light sources inputting at the same time, greatly improves the output optical power of the photonic analog-digital conversion chip, and offsets the influence of the on-chip optical power loss on the conversion precision of the photonic analog-digital conversion chip. The application is a solution for realizing a monolithic integrated high-speed and high-precision photonic analog-digital conversion chip.

Description

Technical Field

[0001] This invention relates to optoelectronic integration technology, specifically a photon analog-to-digital conversion system and chip based on the optical trapping principle. Background Technology

[0002] Signals in nature are all continuously changing analog signals. Analog signals face problems during transmission and processing, such as susceptibility to distortion, poor anti-interference capabilities, and difficulty in storage and processing. Discretizing analog signals into digital signals can solve these problems, which has led to the arrival of the digital age and the era of big data. Analog-to-digital converters (ADCs) are the core devices connecting analog and digital signals. With the development and progress of the information society, human demand for information volume and speed is increasing, and the performance of ADCs is constantly being upgraded.

[0003] Traditional analog-to-digital converters (ADCs) are designed and implemented based on electronic technology, i.e., electronic ADCs. However, electronic ADCs are limited by factors such as aperture jitter and relative blurring, making it difficult to achieve high effective bit sampling and quantization of high-frequency analog signals. Furthermore, the sampling rate of electronic ADCs is also constrained by high-speed clock generation technology, resulting in an "electronic bottleneck." Photonic ADC technology, which combines microwave photonics technology, offers numerous advantages such as high sampling rate, large analog input bandwidth, and low timing jitter. This broadens the input bandwidth of ADCs, improves the sampling rate and effective bit count, and has become an important direction for the future development of ADCs.

[0004] To further enhance the practicality of photonic analog-to-digital conversion (ADC) technology and broaden its application scenarios, photonic ADC systems are gradually evolving towards integrated photonic ADC chips to continuously reduce size and power consumption while improving reliability and stability. Researchers have proposed numerous solutions for integrated photonic ADC chips; however, most solutions merely move existing discrete optoelectronic devices onto a single chip, making it difficult to achieve monolithically integrated photonic ADC chips. Existing reported photonic ADC chips still utilize discrete, large-volume mode-locked lasers as photonic sampling pulses [Mehta, N., et al., “An Optically Sampled ADC in 3D Integrated Silicon-Photonics / 65nm CMOS.” 2020 IEEE Symposium on VLSI Technology, 2020, 1-2.]. Furthermore, due to the limitations imposed by the two-photon absorption effect, the input optical power of photonic analog-to-digital converter (ADC) chips is limited, while the losses of integrated optoelectronic devices are much greater than those of discrete devices. This means that photonic ADC chips can only achieve a low effective number of bits [A. Khilo, et al., "Photonic ADC: overcoming the bottleneck of electronic jitter." Optics Express. Vol. 20, No. 4, 4454-4469, 2012.]. Therefore, only by realizing a monolithically integrated photonic ADC chip, eliminating the need for bulky mode-locked lasers, and offsetting the impact of on-chip optical power loss on the conversion accuracy of the photonic ADC system can the practicality of the photonic ADC be maximized. Summary of the Invention

[0005] This invention proposes a photonic analog-to-digital converter (A / D) system and chip based on the optical trapping principle. The A / D chip utilizes multiple continuous light sources to load sampled analog signals and controls the input of each analog signal to the optical trapping unit at equal time intervals via optical delay lines, achieving signal discretization in the time domain. This invention uses the optical trapping unit to generate a sequence of optical sampling pulses with amplitude modulated by the sampled signal, replacing the mode-locked laser with continuous laser light, and utilizes heterogeneous integration technology to achieve a monolithic integrated photonic A / D chip. The invention's design of simultaneous input from multiple light sources significantly improves the output optical power of the photonic A / D chip, offsetting the impact of on-chip optical power loss on the conversion accuracy. This invention provides a solution for achieving a monolithic integrated high-speed, high-precision photonic A / D chip.

[0006] The technical solution of the present invention is as follows:

[0007] On one hand, the present invention provides a photonic analog-to-digital conversion system based on the optical trapping principle, characterized in that it includes a light source array connected in sequence, a modulator array composed of N electro-optic modulators in parallel, an optical delay line array composed of N delay lines with different delay amounts in parallel, a wavelength division multiplexer, an optical trapping module, a wavelength division multiplexer, a photodetector array composed of N PD units in parallel, and an electronic analog-to-digital converter array composed of N electronic analog-to-digital converters in parallel, wherein N≥2;

[0008] The light source array generates N continuous lasers with different wavelengths. Each laser is loaded with N sampled signals through an electro-optic modulator. The N continuous lasers loaded with sampled signals are input to N optical delay line units. The relative delay of each of the N optical delay line units is designed to be 1 / Nfs, where the delay generated by the nth optical delay line unit is (n-1) / Nfs. This makes each of the originally identical N sampled signals staggered by 1 / Nfs in the time domain, where n = 1, 2, 3...N, and fs is the optical capture frequency.

[0009] N delayed and staggered optical signals are combined into a beam of light by the wavelength division multiplexer and then enter the optical acquisition module. The optical acquisition module simultaneously performs time-domain discretization processing on the sampled signals loaded at different wavelengths at an acquisition frequency of fs.

[0010] The wavelength division multiplexer described is a reverse wavelength division multiplexer that divides the time-domain discretized optical signal into N paths according to wavelength, and then converts each of the N paths into N electrical signals by the N PD units. The N electrical signals are then converted into N electrical digital signals by the N electronic analog-to-digital converters. After the N electrical digital signals are reconstructed and interleaved, the information of the original electrical analog signal can be obtained.

[0011] The optical acquisition module consists of a dual parallel modulator, or a cascaded intensity modulator, phase modulator, or optical microcavity; the photodetector array consists of N photodetectors; and the electronic analog-to-digital converter array consists of N electronic analog-to-digital converters.

[0012] The connection method of each component is as follows: the N output terminals of the light source array are respectively connected to the optical input terminals of the N modulators in the modulator array; the N sampled signals are input to the RF input terminals of the N modulators in the modulator array; the output terminals of the N modulators in the modulator array are respectively connected to the input terminals of the N optical delay line units in the optical delay line array; the output terminals of the N optical delay line units in the optical delay line array are respectively connected to the N channel ports of the wavelength division multiplexer; the multiplexing output terminal of the wavelength division multiplexer is connected to the input terminal of the optical acquisition module; the output terminal of the optical acquisition module is connected to the multiplexing input terminal of the wavelength division demultiplexer; the N output channels of the wavelength division demultiplexer are connected to the input terminals of the N PD units in the photodetector array; the output terminals of the N PD units in the photodetector array are connected to the input terminals of the N electronic analog-to-digital converters in the electronic analog-to-digital converter array, where N is a positive integer greater than or equal to 2.

[0013] On the other hand, the present invention also provides a chip containing the above-mentioned photonic analog-to-digital conversion system based on the optical capture principle, characterized in that the light source array, modulator array, optical delay line array, wavelength division multiplexer, optical capture module, wavelength division multiplexer, photodetector array, and electronic analog-to-digital converter array are sequentially connected and integrated on a single chip using heterogeneous integration technology.

[0014] The light source array, modulator array, optical delay line array, wavelength division multiplexer, optical capture module, wavelength demultiplexer, photodetector array, and electronic analog-to-digital converter array are all integrated on a single chip using heterogeneous integration technology.

[0015] The light source array is realized on a silicon platform using heterogeneous integration technology with III-V group luminescent materials.

[0016] The modulator in the modulator array is an electro-optic intensity modulator. It uses the plasma dispersion effect or the electro-optic effect to change the transmittance of the modulator by changing the optical path difference between the upper and lower arms of the Mach-Zehnder interferometer, thereby modulating the intensity of the continuous laser and thus modulating the sampled signal onto the continuous laser.

[0017] The optical delay line array is composed of optical delay lines of different physical lengths, which generate different delay amounts for optical signals of different wavelengths in different channels to adjust the delay.

[0018] The wavelength division multiplexer and wavelength demultiplexer can be implemented using cascaded Mach-Zehnder interferometers, arrayed waveguide gratings, or cascaded microring resonators.

[0019] The optical capture module is used to generate a sequence of optical sampling pulses whose amplitude is modulated by the sampled signal. It can be implemented using, but is not limited to, a dual parallel modulator, a cascaded phase modulator and intensity modulator, a cascaded intensity modulator, an optical microcavity, etc.

[0020] The photodetector array consists of N photodetectors used to convert optical signals into electrical signals. The photodetectors are implemented by epitaxially growing germanium or germanium-silicon material on silicon and fabricating vertical or horizontal pin junctions.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] 1. By using continuous laser instead of mode-locked laser as the light source for the photonic analog-to-digital converter chip, and combining it with heterogeneous integration technology, a photonic analog-to-digital converter chip with monolithic integration of all optoelectronic devices can be realized, which significantly improves the integration level of the photonic analog-to-digital converter chip, reduces the chip size, and improves the practicality and stability of the photonic analog-to-digital converter chip.

[0023] 2. By connecting a multi-wavelength light source array to the modulator array, the total input optical power of the chip is increased without causing the two-photon absorption effect, effectively offsetting the impact of on-chip optical power loss on the conversion accuracy of the photonic analog-to-digital converter chip.

[0024] 3. The combination of wavelength division multiplexing (WDM) technology and optical acquisition technology makes it possible to generate multiple synchronous optical sampling pulses using a single optical acquisition module. The pulses are highly synchronized, thus avoiding signal distortion caused by delay errors and eliminating the need for separate synchronization adjustments for each channel. Attached Figure Description

[0025] Figure 1 This is an overall architecture diagram of a photonic analog-to-digital converter chip embodiment based on the optical capture principle of the present invention.

[0026] Figure 2 This is a schematic diagram illustrating the application of heterogeneous integration to directly bond III-V group continuous lasers onto a silicon wafer.

[0027] Figure 3 is a schematic diagram of a modulator embodiment; Figure 3(a) is a Mach-Zehnder intensity modulator architecture diagram; Figure 3(b) is a phase modulation structure diagram of the upper and lower arms of the Mach-Zehnder intensity modulator; Figure 3(c) is a schematic diagram of a PN junction formed by ridge waveguide doping.

[0028] Figure 4 shows schematic diagrams of three wavelength division multiplexer (WDM) embodiments, where the WDM is used in reverse. Figure 4(a) shows a WDM and WDM based on a cascaded Mach-Zehnder interferometer. Figure 4(b) shows a WDM and WDM based on an arbitrary waveguide grating. Figure 4(c) shows a WDM and WDM based on a cascaded microring resonator.

[0029] Figure 5 is a schematic diagram of the architecture of an optical capture module embodiment; Figure 5(a) is the architecture of an optical capture module embodiment with a cascaded intensity modulator and a phase modulator; Figure 5(b) is the architecture of an optical capture module embodiment with dual parallel modulators. Detailed Implementation

[0030] A specific embodiment of this invention is given below with reference to the accompanying drawings. This embodiment is implemented based on the technical solution of this invention, and provides detailed implementation methods and processes, but the scope of protection of this invention is not limited to the following embodiment.

[0031] Please see Figure 1 , Figure 1 This is an overall architecture diagram of a photonic analog-to-digital converter chip embodiment based on the optical trapping principle of the present invention. As shown in the diagram, it comprises a light source array 1, a modulator array 2, an optical delay line array 3, a wavelength division multiplexer 4, an optical trapping module 5, a wavelength demultiplexer 6, a photodetector array 7, and an electronic analog-to-digital converter array 8. The light source array 1 consists of N continuous laser sources with different wavelengths. The wavelength division multiplexer 4 consists of cascaded Mach-Zehnder interferometers, arrayed waveguide gratings, or cascaded microring resonators. The wavelength demultiplexer 6 is a wavelength division multiplexer 4 used in reverse. The modulator array 2 consists of N modulators. The optical delay line array 3 consists of N delay lines with different delay amounts. The optical trapping module 5 consists of dual parallel modulators, or cascaded intensity modulators / phase modulators, or optical microcavities. The photodetector array 7 consists of N germanium diodes grown on silicon and doped to form PIN diodes. The electronic analog-to-digital converter array 8 consists of N electronic analog-to-digital converters. The connection method of each component is as follows: the N output terminals of the light source array 1 are respectively connected to the optical input terminals of the N modulators in the modulator array 2; the N sampled signals are input to the RF input terminals of the N modulators in the modulator array 2; the output terminals of the N modulators in the modulator array 2 are respectively connected to the input terminals of the N optical delay line units in the optical delay line array 3; the output terminals of the N optical delay line units in the optical delay line array 3 are respectively connected to the N channel ports of the wavelength division multiplexer 4; the multiplexing output terminal of the wavelength division multiplexer 4 is connected to the input terminal of the optical capture module 5; the output terminal of the optical capture module 5 is connected to the multiplexing input terminal of the wavelength division demultiplexer 6; the N output channels of the wavelength division demultiplexer 6 are connected to the input terminals of the N PD units in the photodetector array 7; and the output terminals of the N PD units in the photodetector array 7 are connected to the input terminals of the N electronic analog-to-digital converters in the electronic analog-to-digital converter array 8, where N is a positive integer greater than or equal to 2.

[0032] The light source array 1 generates N continuous lasers with different wavelengths. The N sampled signals are loaded onto the N continuous lasers with different wavelengths through the electro-optic modulators in each path. The N continuous lasers loaded with the sampled signals are respectively input into the N optical delay line units in the optical delay line array 3. The relative delay of each of the N optical delay line units is designed to be 1 / Nfs, where the delay generated by the nth optical delay line unit is (n-1) / Nfs. This makes the N sampled signals, which were originally identical, staggered by 1 / Nfs in the time domain, where n = 1, 2, 3...N, and fs is the optical capture frequency. The N optical signals with staggered delays are combined into a beam of light by the wavelength division multiplexer 4 and then enter the optical capture module 5. The optical capture module 5 simultaneously performs time-domain discretization processing on the sampled signals loaded at different wavelengths at the capture frequency of fs. The time-domain discretized optical signal is again divided into N paths according to wavelength by the wavelength demultiplexer 6, and N paths of electrical signals are obtained by photoelectric conversion by N PD units. Then, N paths of electrical digital signals are obtained by N electronic analog-to-digital converters. The information of the original electrical analog signal can be obtained by reconstructing and interleaving the N paths of electrical digital signals.

[0033] The aforementioned light source array 1 achieves monolithic integration of photonic analog-to-digital converter chips by bonding III-V group materials onto a silicon wafer using a heterogeneous integration method. Bonding techniques include, but are not limited to, direct bonding, eutectic bonding, anodic bonding, thermo-press bonding, and ultrasonic bonding. The specific implementation method of direct bonding technology is provided below: (e.g.) Figure 2 As shown, after cleaning, oxygen plasma treatment, wet wafer surface treatment for direct bonding, annealing at 250-300℃ and 1MPa pressure, and etching to remove the InP substrate, silicon and III-V form strong covalent bonds with each other and are bonded together by van der Waals forces or hydrogen bonds. This enables monolithic integration of the light source array 1 and other optoelectronic devices in the photonic analog-to-digital converter chip.

[0034] The modulator array 2 consists of N silicon-based Mach-Zehnder intensity modulators (Fig. 3(a)). Phase modulation is added to the upper and lower arms of the Mach-Zehnder interferometer (Fig. 3(b)). A PN junction is formed by doping the ridge waveguide (Fig. 3(c)). The carrier dispersion effect is applied to adjust the refractive index of the upper and lower arms to affect the optical path difference, thereby changing the transmittance of the modulator and thus realizing the intensity modulation of the optical signal.

[0035] The optical delay line array 3 is composed of optical delay lines of different physical lengths, which generate different delay amounts for optical signals of different wavelengths in different channels to adjust the delay.

[0036] The wavelength division multiplexer 4 and wavelength demultiplexer 6 are used to combine and demultiplex lasers of different wavelengths. Wavelength division multiplexer 4 is a wavelength demultiplexer 5 used in reverse. Its structure includes, but is not limited to, a wavelength division multiplexer with cascaded Mach-Zehnder interferometers (Figure 4(a)), a wavelength division multiplexer with arbitrary waveguide gratings (Figure 4(b)), and a wavelength division multiplexer based on cascaded microring resonators (Figure 4(c)).

[0037] The optical capture module 5 is used to generate a sequence of light sampling pulses whose amplitude is modulated by the sampled signal. The scheme can be, but is not limited to, a cascaded phase modulator and intensity modulator (Figure 5(a)) or a dual parallel modulator (Figure 5(b)).

[0038] The photodetector array consists of N photodetectors used to convert optical signals into electrical signals. The photodetectors are implemented by epitaxially growing germanium or germanium-silicon material on silicon and fabricating vertical or horizontal pin junctions.

[0039] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A photonic analog-to-digital conversion system based on the principle of optical trapping, characterized in that, The array includes a light source array (1) connected in sequence, a modulator array (2) consisting of N electro-optic modulators arranged in parallel, an optical delay line array (3) consisting of N delay lines with different delay amounts arranged in parallel, a wavelength division multiplexer (4), an optical capture module (5), a wavelength division multiplexer (6), a photodetector array (7) consisting of N PD units arranged in parallel, and an electronic analog-to-digital converter array (8) consisting of N electronic analog-to-digital converters arranged in parallel, wherein N≥2; The light source array (1) generates N continuous lasers with different wavelengths. Each of the N sampled signals is loaded onto the N continuous lasers with different wavelengths through each electro-optic modulator. The N continuous lasers loaded with the sampled signals are respectively input into N optical delay line units. The relative delay of each of the N optical delay line units is designed to be 1 / Nfs. The delay generated by the nth optical delay line unit is (n-1) / Nfs, so that each of the N sampled signals that were originally identical is staggered by 1 / Nfs in the time domain. Where n=1, 2, 3...N, and fs is the optical capture frequency. N delayed optical signals are combined into a beam of light by the wavelength division multiplexer (4) and then enter the optical capture module (5). The optical capture module (5) simultaneously performs time-domain discretization processing on the sampled signals loaded on different wavelengths at a capture frequency of fs. The wavelength division multiplexer (6) is a wavelength division multiplexer (4) used in reverse. It divides the time-domain discretized optical signal into N paths according to wavelength, and converts them into N electrical signals by the N PD units. The N electrical signals are converted into N electrical digital signals by the N electronic analog-to-digital converters. After the N electrical digital signals are reconstructed and interleaved, the information of the original electrical analog signal can be obtained.

2. Photonic analog-to-digital conversion system of the optical trapping principle according to claim 1, characterized in that, The light source array (1) consists of N continuous laser light sources with different wavelengths.

3. The photon analog-to-digital conversion system based on the optical trapping principle according to claim 1, characterized in that, The optical capture module (5) employs a dual parallel modulator, a cascaded phase modulator and intensity modulator, a cascaded intensity modulator, or an optical microcavity.

4. A photonic analog-to-digital converter chip, comprising the photonic analog-to-digital converter system according to any one of claims 1-3, characterized in that, The light source array (1), modulator array (2), optical delay line array (3), wavelength division multiplexer (4), optical capture module (5), wavelength division multiplexer (6), photodetector array (7), and electronic analog-to-digital converter array (8) are sequentially connected and integrated on a single chip using heterogeneous integration technology.

5. The chip according to claim 4, characterized in that, The light source array (1) is monolithically integrated by bonding III-V group materials onto a silicon wafer using a heterogeneous integration method.

6. The chip according to claim 4, characterized in that, The modulator array (2) consists of electro-optic intensity modulators. By using the plasma dispersion effect or electro-optic effect, the transmittance of the modulator is changed by changing the optical path difference between the upper and lower arms of the Mach-Zehnder interferometer, so as to modulate the sampled signal onto the continuous laser.

7. The chip according to claim 4, characterized in that, The optical capture module (5) is used to generate a sequence of optical sampling pulses whose amplitude is modulated by the sampled signal, using a dual parallel modulator, a cascaded phase modulator and intensity modulator, a cascaded intensity modulator or an optical microcavity.

8. The chip according to claim 4, characterized in that, The wavelength division multiplexer (4) and the wavelength demultiplexer (6) are wavelength division multiplexers and wavelength demultiplexers based on cascaded Mach-Zehnder interferometers, or wavelength division multiplexers and wavelength demultiplexers based on arbitrary waveguide gratings, or wavelength division multiplexers and wavelength demultiplexers based on cascaded microring resonators.

9. The chip according to claim 4, characterized in that, The photodetector array (7) consists of N PIN diodes formed by growing germanium on silicon and doping them. This is achieved by epitaxially growing germanium or germanium-silicon material on silicon and fabricating vertical or horizontal PIN junctions.

10. The chip according to claim 4, characterized in that, The light source array is heterogeneously integrated by bonding III-V group materials to silicon wafers using bonding technology. The bonding methods include direct bonding, eutectic bonding, anodic bonding, thermo-pressing bonding, and ultrasonic bonding.

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