A method and system for improving the power monitoring range of an optical chip photodetector
By applying a 0V bias using a low-gain PIN photodetector on the optical chip and combining it with temperature control, the problems of dark current and noise in photodetectors when monitoring weak and strong light are solved, and high-precision optical power monitoring is achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- QUANTUMCTEK CO LTD
- Filing Date
- 2024-12-26
- Publication Date
- 2026-06-26
AI Technical Summary
Existing optical chip photodetectors suffer from problems such as large dark current, noise amplification, significant temperature influence, and uneven monitoring range when monitoring weak and strong light, making it difficult to achieve high-precision optical power monitoring.
A low-gain PIN photodetector is used with a 0V bias applied. Combined with temperature control, the photocurrent is calculated by the responsivity and dark current of the photodetector material, and the optical signal is directly monitored, avoiding the influence of temperature changes on the dark current.
It enables wide-range optical power monitoring under both weak and strong light conditions, reduces dark current fluctuations, improves monitoring accuracy and stability, and avoids noise amplification.
Smart Images
Figure CN122282102A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of optical technology, specifically relating to a method and system for improving the power monitoring range of an optical chip photodetector. Background Technology
[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.
[0003] In the field of quantum communication, information encoding and decoding are usually based on weak light signals at the single-photon level. Due to the high requirements for light intensity stability, photodetectors are often designed to monitor the power of weak light signals, and high sensitivity is also required.
[0004] In recent years, with the development of new materials, the field of quantum communication has also begun to use germanium-silicon photodiodes made of new materials. Their cost can be reduced by several times compared with traditional group III-V photodiodes, but their dark current is much higher than that of traditional materials and is greatly affected by temperature. When using conventional methods to monitor the power of signal light through germanium-silicon photodiodes, it cannot meet the requirements for the indication accuracy of weak light.
[0005] Currently, in the field of optical chips, there are generally two methods for detecting weak light on the chip: one is to use an avalanche diode (APD). However, the photosensitive surface of an APD is generally small, and it is very easy to saturate when monitoring strong light. If the monitoring range needs to include both weak and strong light, two or more APDs are required. Moreover, APDs usually require a large bias voltage to increase the linear region range, and the dark current is usually also very large. The second method is to connect a high-gain amplifier to the PIN photodiode. The function of the amplifier is to amplify the input current signal to obtain a larger voltage signal output. However, a high-gain amplifier will amplify all signals, including noise signals.
[0006] For example, the invention patent with publication number CN113805270A and title "A Highly Integrated Silicon Photonic Chip", such as Figure 1As shown, 10 is a silicon substrate, 30 is a splitter, and 40 is a silicon optical modulator. This patent uses two detection optical paths to detect weak light, each carrying a high-gain germanium-silicon avalanche diode detector 701 and a low-gain PIN photodetector 702. When detecting weak light, the light emitted by the first laser 801 passes through the first optical path, and 701 receives the gain. When detecting strong light, the light emitted by the second laser 802 passes through the second optical path, and 702 receives the gain. This allows monitoring of both the lower-power first optical path and receiving the higher-power second optical path without amplifying the noise from the strong light in the second optical path. However, this method uses two photodetectors, and the germanium-silicon material has a large dark current, resulting in excessive noise during amplification, even with weak light. If the monitoring range is very large, i.e., from strong light modulation to weak light, the transition region between strong and weak light will be uneven. Furthermore, the existing solution does not consider the effect of temperature on the dark current of the photodetector. If the silicon photomodulator operates for a long time, heat will accumulate and crosstalk to the detector, causing changes in the dark current. As time changes, the gain and noise will also change, which increases the difficulty of subsequent monitoring. Summary of the Invention
[0007] To address the aforementioned problems, this invention proposes a method and system for improving the power monitoring range of a photodetector in an optical chip. This invention only requires a photodetector with a zero-voltage bias. By controlling the local temperature, the fluctuation amplitude of the dark current is reduced. Combined with the responsivity analysis of the photodetector material, the measured current signal can be directly used to monitor the corresponding optical signal, thereby achieving wide-range optical power monitoring.
[0008] According to some embodiments, the present invention adopts the following technical solution:
[0009] A method for improving the power monitoring range of an optical chip photodetector includes the following steps:
[0010] Using a photodetector to acquire the optical signal from the optical chip;
[0011] Turn off the light source, apply a zero bias voltage to the photodetector to minimize the dark current, record the acquired dark current, and achieve dark current calibration.
[0012] Turn on the light source and acquire the photocurrent signal from the photodetector;
[0013] Based on the responsivity, dark current, and photocurrent signal of the photodetector material, the photocurrent is calculated, and the optical power is obtained.
[0014] During the above process, the temperature of the entire optical chip is controlled to keep the temperature within the set range.
[0015] As an alternative implementation, the photodetector is a germanium-silicon PIN photodetector.
[0016] As an alternative implementation, the optical chip is a silicon photonic chip.
[0017] As an alternative implementation method, the process of performing photocurrent calculation to obtain optical power P includes: Where R is the responsivity of the photodetector material, Id is the dark current, and Is is the photocurrent signal.
[0018] As an alternative implementation, the process of applying a zero-voltage bias to the photodetector is to apply a reverse bias voltage of 0V to the germanium-silicon PIN photodetector.
[0019] A system for improving the power monitoring range of an optical chip photodetector includes:
[0020] A photodetector is connected to the light source of the optical chip to acquire the optical signal from the optical chip.
[0021] The power supply module is used to apply a zero-voltage bias to the photodetector when the light source is off, so as to minimize the dark current.
[0022] The photocurrent acquisition module is used to acquire the dark current of the biased photodetector and to acquire the photocurrent signal of the photodetector after the light source is turned on.
[0023] The photocurrent calculation module is used to calculate the photocurrent based on the responsivity, dark current, and photocurrent signal of the photodetector material, and to calculate the optical power.
[0024] The temperature control module is used to control the temperature of the entire optical chip, keeping its temperature within a set range.
[0025] As an alternative implementation, the light source is connected to the optical chip via a grating array and optical fiber. Each active device in the optical path of the optical chip is connected via a waveguide. The optical signal output by the light source is output to a multimode interference coupler after passing through the active devices. The multimode interference coupler splits the signal into two paths, one of which is output to the subsequent optical path for continued transmission, and the other is output to the photodetector.
[0026] As a further step, the active device is a low-speed phase modulator, a high-speed phase modulator, or an optical power regulator.
[0027] As an alternative implementation, the photodetector is connected to the photocurrent acquisition module and the power supply module via electrical interconnection.
[0028] As an alternative implementation, the entire optical chip is within the temperature control module's control range.
[0029] As an alternative implementation, the optical chip and the temperature control module are packaged together.
[0030] As an alternative implementation, the photodetector is a germanium-silicon PIN photodetector.
[0031] As an alternative implementation, the optical chip is a silicon photonic chip.
[0032] As an alternative implementation, the photocurrent calculation module is configured to calculate: Where R is the responsivity of the photodetector material, Id is the dark current, Is is the photocurrent signal, and P is the calculated optical power.
[0033] As an alternative implementation, the power module is used to apply a reverse bias voltage of 0V to the germanium-silicon PIN photodetector.
[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0035] This invention innovatively proposes a method to improve the power monitoring range of a photodetector in an optical chip. In the initial stage, a 0V bias is applied to the PD to minimize the dark current, and the temperature of the entire optical chip is controlled to ensure that the dark current used for calibration is a constant value. The dark current is acquired in a dark environment and used in the final calculation process. When the photocurrent calculation module performs the calculation, the dark current is subtracted from the photocurrent acquired when the optical chip is working. The resulting value is the photoelectric response value of the photodetector in the light-transmitting state, which can accurately characterize the represented optical power and realize the monitoring of weak light.
[0036] This invention innovatively proposes a system for improving the power monitoring range of an optical chip photodetector. It does not require extensive structural modifications to the optical chip circuitry; it only requires a multimode interference coupler to split one optical output path to a PIN photodetector. Using only a low-gain PIN photodetector, the photocurrent can be directly calculated, enabling monitoring of a large range from strong to weak light (e.g., single-photon level). It eliminates the need for amplification of the original signal; the power monitoring range of the photodetector is improved simply by directly calculating the photocurrent through a corresponding photocurrent calculation module.
[0037] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description
[0038] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.
[0039] Figure 1 This is a schematic diagram of the detection optical path structure in existing technology;
[0040] Figure 2 This is a schematic flowchart of a method for improving the power monitoring range of an optical chip photodetector according to one embodiment;
[0041] Figure 3 This is a schematic diagram of a system structure for improving the power monitoring range of an optical chip photodetector, according to one embodiment. Detailed Implementation
[0042] The present invention will be further described below with reference to the accompanying drawings and embodiments.
[0043] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.
[0044] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.
[0045] Where there is no conflict, the embodiments and features described in this application may be combined with each other.
[0046] Example 1
[0047] This embodiment provides a method for improving the power monitoring range of an optical chip photodetector. In this embodiment, only a low-gain PIN photodetector, such as a germanium-silicon PIN photodetector (PD, also known as a photodiode or photodetector), is used, and a 0V (zero voltage) bias is applied. By controlling the local temperature, the fluctuation amplitude of the dark current is reduced. Then, an external analysis module is used to analyze the responsivity of the germanium-silicon material, and the measured current signal is directly used to monitor the corresponding optical signal. In this way, a wide range of optical power monitoring can be achieved using only a single PIN photodetector.
[0048] The specific implementation process is described below.
[0049] As described in the background section, temperature has a significant impact on dark current. When a load is applied, heat is generated locally, and the dark current changes by 6% to 10% for every 1°C increase. When the optical power is below -50dBm, the temperature-induced changes in dark current due to the heat generated by the device introduce variables that are indistinguishable after light transmission, significantly affecting the calculation process. Therefore, this embodiment controls the local temperature throughout the entire process, keeping the dark current constant and avoiding calculation errors caused by temperature variations.
[0050] Of course, the aforementioned local temperature control can be achieved through devices such as temperature control modules.
[0051] The method in this embodiment includes the following steps:
[0052] Using a photodetector to acquire the optical signal from the optical chip;
[0053] Turn off the light source, apply a zero bias voltage to the photodetector to minimize the dark current, record the acquired dark current, and achieve dark current calibration.
[0054] Turn on the light source and acquire the photocurrent signal from the photodetector;
[0055] Based on the responsivity, dark current, and photocurrent signals of the photodetector material, the photocurrent is calculated, and the optical power is obtained.
[0056] First, let's explain the principle:
[0057] PD working mode
[0058] Applying a reverse bias to the PD increases the width of the depletion region, leading to increased responsivity and decreased junction capacitance. This results in a higher dark current, which is directly temperature-dependent; as temperature rises, the dark current increases significantly. In low-light conditions, the photocurrent level is very close to the dark current. Even with temperature control to manage dark current, it's crucial to minimize it as much as possible. A 0V bias puts the PD in photovoltaic mode, restricting current flow. In this mode, the PD has the lowest dark current, and the temperature control is most effective.
[0059] Optical power calculation
[0060] The relevant parameters for optical power calculation include the measured photocurrent Is, dark current Id, and the material's responsivity R. Due to the temperature control and PD operating mode settings, the impact of temperature on the PD's dark current is minimized. Even if the ambient temperature changes, the dark current Id can be considered constant during testing. Furthermore, since the PD operates at 0V, the responsivity R is also constant. Therefore, only the photocurrent Is is a variable in the optical power P calculation. Recording the dark current Id only once during system initialization before testing ensures accurate real-time monitoring and optical power calculation results throughout the testing process.
[0061] The solution formula is as follows:
[0062]
[0063] like Figure 2 As shown, temperature control is implemented to ensure that the local temperature remains constant throughout the entire test process, preventing dark current fluctuations caused by temperature changes.
[0064] Turn off the light source and ensure that the optical path of the PD is in a dark environment. Apply a reverse bias voltage of 0V to the PD, and it will work in photovoltaic mode with the minimum dark current. Record the acquired dark current Id to complete the dark current calibration.
[0065] When the light source is turned on, the optical chip works normally. Due to interference, modulation, beam splitting, and beam combining, the optical power changes, and the optical power monitored by the PD changes accordingly, which is converted into a current signal and changes accordingly.
[0066] Real-time monitoring of the PD current signal Is, based on the responsivity R of the germanium-silicon material, the dark current Id, and the measured photocurrent Is, the photocurrent is calculated into optical power P according to the following formula.
[0067]
[0068] In summary, this embodiment minimizes dark current by applying a 0V bias to the PD in the initial stage and controls the temperature of the entire optical chip to ensure that the dark current used for calibration is a constant value. The dark current is acquired in a dark environment and used in the final calculation process. During the calculation, the dark current is subtracted from the photocurrent acquired when the optical chip is working. The resulting value is the photoelectric response value of the photodetector in the light-transmitting state, which can accurately characterize the optical power it represents and realize the monitoring of weak light.
[0069] Example 2
[0070] A system for improving the power monitoring range of an optical chip photodetector, such as Figure 3As shown, the system includes a light source, a temperature control module, an optical chip, a power supply module, a photocurrent acquisition module, and a photocurrent calculation module. The light source is connected to the optical chip via a grating array and optical fiber. The active devices in the optical path of the optical chip are connected via waveguides. The optical signal output from the light source is output to a multimode interference coupler (MMI) after passing through the active devices. The MMI splits the signal into two paths: one path is output to the subsequent optical path for further transmission, and the other path is output to the photocurrent acquisition module (PD). The PD is electrically interconnected with the photocurrent acquisition module and the power supply module (which applies a 0V bias to the PD). The entire optical chip is under the control of the temperature control module, which maintains a constant overall temperature.
[0071] The optical chip structure is based on a silicon-based SOI chip.
[0072] The temperature control module can be a temperature-controlled vacuum chuck for bare chips or directly packaged with the chip.
[0073] Active devices can be low-speed phase modulators (e.g., thermally tuned phase shifters), high-speed phase modulators (e.g., carrier depletion modulators), optical power regulators (e.g., variable optical attenuators), etc.
[0074] The photocurrent acquisition module can be a source meter, transimpedance amplifier, or other device or system that can record the data of the PD in the optical chip.
[0075] The photocurrent calculation module can be software used to calculate optical power, etc.
[0076] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made by those skilled in the art without creative effort within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A method for improving the power monitoring range of an optical chip photodetector, characterized in that, Includes the following steps: Using a photodetector to acquire the optical signal from the optical chip; Turn off the light source, apply a zero bias voltage to the photodetector to minimize the dark current, record the acquired dark current, and achieve dark current calibration. Turn on the light source and acquire the photocurrent signal from the photodetector; Based on the responsivity, dark current, and photocurrent signal of the photodetector material, the photocurrent is calculated, and the optical power is obtained. During the above process, the temperature of the entire optical chip is controlled to keep the temperature within the set range.
2. The method for improving the power monitoring range of an optical chip photodetector as described in claim 1, characterized in that, The photodetector is a germanium-silicon PIN photodetector.
3. The method for improving the power monitoring range of an optical chip photodetector as described in claim 1, characterized in that, The optical chip is a silicon photonic chip.
4. The method for improving the power monitoring range of an optical chip photodetector as described in claim 1, characterized in that, The process of calculating the photocurrent and obtaining the optical power P includes: Where R is the responsivity of the photodetector material, Id is the dark current, and Is is the photocurrent signal.
5. The method for improving the power monitoring range of an optical chip photodetector as described in claim 1, characterized in that, The process of applying a zero bias voltage to a photodetector is equivalent to applying a reverse bias voltage of 0V to a germanium-silicon PIN photodetector.
6. A system for improving the power monitoring range of an optical chip photodetector, characterized in that, include: A photodetector is connected to the light source of the optical chip to acquire the optical signal from the optical chip. The power supply module is used to apply a zero-voltage bias to the photodetector when the light source is off, so as to minimize the dark current. The photocurrent acquisition module is used to acquire the dark current of the biased photodetector and to acquire the photocurrent signal of the photodetector after the light source is turned on. The photocurrent calculation module is used to calculate the photocurrent based on the responsivity, dark current, and photocurrent signal of the photodetector material, and to calculate the optical power. The temperature control module is used to control the temperature of the entire optical chip, keeping its temperature within a set range.
7. The system for improving the power monitoring range of an optical chip photodetector as described in claim 6, characterized in that, The light source is connected to the optical chip via a grating array and optical fiber. The active devices in the optical path of the optical chip are connected via waveguides. The optical signal output by the light source is output to a multimode interference coupler after passing through the active devices. The multimode interference coupler splits the signal into two paths, one of which is output to the subsequent optical path for further transmission, and the other is output to the photodetector.
8. The system for improving the power monitoring range of an optical chip photodetector as described in claim 7, characterized in that, The active device is a low-speed phase modulator, a high-speed phase modulator, or an optical power regulator.
9. The system for improving the power monitoring range of an optical chip photodetector as described in claim 6, characterized in that, The photodetector is electrically interconnected with the photocurrent acquisition module and the power supply module.
10. The system for improving the power monitoring range of an optical chip photodetector as described in claim 6, characterized in that, The entire optical chip is within the temperature control range of the temperature control module.
11. A system for improving the power monitoring range of an optical chip photodetector as described in claim 6 or 10, characterized in that, The optical chip and temperature control module are packaged together.
12. The system for improving the power monitoring range of an optical chip photodetector as described in claim 6, characterized in that, The photodetector is a germanium-silicon PIN photodetector.
13. The system for improving the power monitoring range of an optical chip photodetector as described in claim 6, characterized in that, The optical chip is a silicon photonic chip.
14. The system for improving the power monitoring range of an optical chip photodetector as described in claim 6, characterized in that, The photocurrent calculation module is configured to calculate: Where R is the responsivity of the photodetector material, Id is the dark current, Is is the photocurrent signal, and P is the calculated optical power.
15. The system for improving the power monitoring range of an optical chip photodetector as described in claim 6, characterized in that, The power module is used to apply a reverse bias voltage of 0V to the germanium-silicon PIN photodetector.