A MHz bandwidth high signal-to-noise ratio 16-quadrant photodetector

Abstract

The present application relates to the technical field of photoelectric detector, particularly relates to a MHz bandwidth high signal-to-noise ratio 16-quadrant photoelectric detector, which comprises a 16-quadrant photodiode, the 16-quadrant photodiode comprises 16 photodiodes, the cathodes of each photodiode are connected in common and connected with a voltage anode, the anodes of each photodiode are connected with a corresponding signal conditioning circuit respectively, the structure of each signal conditioning circuit is same, which comprises: a capacitor 17, a transimpedance amplifier U18, a capacitor C19, an inductor L20, a sampling resistor R21, a resistor R22 and an operational amplifier U23.The present application optimizes the circuit design and layout, so that the AC and DC responses of each quadrant of the detector are consistent, solves the pixel crosstalk problem, greatly improves the anti-electromagnetic interference performance of the detector, and the designed 16-quadrant photoelectric detector has a very high signal-to-noise ratio and a wide linear range in the MHz bandwidth, and can realize the measurement of MHz bandwidth multi-quadrant laser intensity noise and the multi-quadrant noise spectrum measurement of non-classical light field in this frequency band.

Description

Technical Field

[0001] This invention relates to the field of photodetector technology, and in particular to a 16-quadrant photodetector with a MHz bandwidth and high signal-to-noise ratio. Background Technology

[0002] Research in quantum information science is inseparable from non-classical optical fields, such as compressed light and entangled light, which are now widely used in quantum teleportation, quantum dense coding, quantum key distribution, and quantum precision measurement. Experiments not only require the generation of high-quality non-classical optical fields but also their accurate measurement. Taking compressed light as an example, to reduce the impact of electronic noise on the measurement, the measured shot noise benchmark must be at least 10 dB higher than the electronic noise level.

[0003] In quantum precision measurement and imaging, such as small displacement measurement or super-resolution parameter estimation of incoherent point sources, effective measurement can be achieved by combining local field projection measurement techniques with equilibrium zero-beat methods. However, this method involves complex equipment. Multi-quadrant heterodyne detection greatly simplifies the experimental setup and is a simple and efficient measurement technique. However, current multi-quadrant detectors all employ DC amplification designs, making them unsuitable for direct application in quantum communication, quantum precision measurement and imaging, and other quantum information science fields. High signal-to-noise ratio AC / DC multi-quadrant photodetectors with MHz bandwidth have not been reported. Summary of the Invention

[0004] The purpose of this invention is to provide a 16-quadrant photodetector with a high signal-to-noise ratio and a MHz bandwidth, so as to realize the measurement of multi-quadrant laser intensity noise and the multi-quadrant noise spectrum of non-classical optical fields in this frequency band.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: a MHz bandwidth high signal-to-noise ratio 16-quadrant photodetector, comprising 16 quadrant photodiodes, wherein each 16-quadrant photodiode comprises 16 photodiodes, each photodiode sharing a common cathode and being connected to a positive voltage electrode via a feedthrough capacitor, and the anode of each photodiode being connected to a corresponding signal conditioning circuit, wherein each signal conditioning circuit has the same structure, including:

[0006] Capacitor C17, transimpedance amplifier U18, capacitor C19, inductor L20, sampling resistor R21, resistor R22, operational amplifier U23;

[0007] One end of capacitor C17 is connected to the anode of the corresponding photodiode, and the other end is connected to the input terminal of transimpedance amplifier U18. The output terminal of transimpedance amplifier U18 is connected to AC output terminal AC1 via capacitor C19. One end of inductor L20 is connected to the anode of the corresponding photodiode, and the other end is connected to one end of sampling resistor R21 and resistor R22. The other end of sampling resistor R21 is grounded, and the other end of resistor R22 is connected to the input terminal of operational amplifier U23. The output terminal of operational amplifier U23 is connected to DC output terminal DC1.

[0008] The DC output terminal DC1 is used to monitor the light intensity of the photodiode in the corresponding quadrant, and the AC output terminal is used to monitor the intensity noise of the photodiode in the corresponding quadrant.

[0009] The aforementioned MHz bandwidth high signal-to-noise ratio 16-quadrant photodetector further includes a power conversion circuit, which comprises four power conversion units, each power conversion unit supplying power to four signal conditioning circuits therein, and each power conversion unit comprising:

[0010] The system comprises a first voltage regulator chip, a second voltage regulator chip, a third voltage regulator chip, and a fourth voltage regulator chip. The first voltage regulator chip is used to convert an external positive voltage into a +6V DC voltage, and the second voltage regulator chip is used to convert the +6V DC voltage into a +5V DC voltage for output.

[0011] The third voltage regulator chip is used to convert the external negative voltage into a -6V DC voltage, and the fourth voltage regulator chip is used to convert the -6V DC voltage into a -5V DC voltage before outputting it.

[0012] The first, second, third, and fourth voltage regulator chips are MC7806, TPS7A4701, MC7906, and TPS7A3301, respectively.

[0013] The IN port of the first voltage regulator chip is connected to a +9V voltage and one end of capacitor C30, the other end of capacitor C30 is grounded, the GND port of the first voltage regulator chip is grounded, the OUT port is connected to one end of capacitors C32 and C33 and outputs a +6V voltage, the other ends of capacitors C32 and C33 are grounded, the IN port of the second voltage regulator chip is connected to the EN port and one end of capacitor C33, the NR port of the second voltage regulator chip is connected to one end of capacitor C34, the other end of capacitor C34 is grounded, the OUT port is connected to one end of resistor R36 and capacitor C38 and outputs a +5V voltage, the other end of resistor R36 is connected to the FB port and one end of resistor R37, the other end of resistor R37 is grounded, and the GND port of the second voltage regulator chip is grounded;

[0014] The IN port of the third voltage regulator chip is connected to a -9V voltage and one end of capacitor C39, with the other end of capacitor C39 grounded. The GND port of the third voltage regulator chip is grounded. The OUT port is connected to one end of capacitors C41 and C42, outputting a -6V voltage. The other ends of capacitors C41 and C42 are grounded. The IN port of the fourth voltage regulator chip is connected to the EN port and one end of capacitor C42. The NR port of the fourth voltage regulator chip is grounded via capacitor C43. The OUT port is connected to one end of resistor R46 and capacitor C48, outputting a -5V voltage. The other end of resistor R46 is connected to the FB port of the fourth voltage regulator chip and one end of resistor R47, with the other end of resistor R47 grounded. The GND port of the fourth voltage regulator chip is grounded. Capacitor C45 is placed between the FB port and the OUT port of the fourth voltage regulator chip.

[0015] The MHz bandwidth high signal-to-noise ratio 16-quadrant photodetector also includes a PCB board. The 16-quadrant photodiode, signal conditioning circuit and power conversion circuit are all mounted on the PCB board, and each transimpedance amplifier U18 is mounted on the side close to the 16-quadrant photodiode. The power conversion circuit and operational amplifier U23 are mounted outside the transimpedance amplifier U18.

[0016] The 16-quadrant photodiode is model S8558, the inductance of inductor L20 is 1.12mH, and the sampling resistor R21 has a resistance of 100Ω.

[0017] The signal conditioning circuit also includes a feedback resistor R24, capacitors C25, C26, and C27. One end of the feedback resistor R24 ​​is connected to the inverting input of the transimpedance amplifier U18, and the other end is connected to the output of the transimpedance amplifier U18. The other end of the capacitor C17 is connected to the inverting input of the transimpedance amplifier U18. One end of the capacitor C25 is connected to the inverting input of the transimpedance amplifier U18, and the other end is connected to the output of the transimpedance amplifier U18 via capacitor C26. One end of the capacitor C27 is connected to the other end of the capacitor C25, and the other end is grounded.

[0018] The transimpedance amplifier U18 is model OPA818. The capacitance values ​​of capacitors C25, C26 and C27 are 2.2pF, 2.2pF and 68pF respectively. The capacitance values ​​of capacitors C17 and C19 are 1uF and 0.1uF respectively. The resistance value of feedback resistor R24 ​​is 200kΩ.

[0019] The signal conditioning circuit also includes resistors R28 and R29. The other end of resistor R22 is connected to the non-inverting input of operational amplifier U23. The inverting input of operational amplifier U23 is grounded through resistor R28. The inverting input of operational amplifier U23 is connected to the output through resistor R29.

[0020] The operational amplifier U23 is model OPA2227, the resistor R28 has a resistance of 50Ω, and the resistor R29 has a resistance of 1kΩ.

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

[0022] 1. This invention provides a 16-quadrant photodetector with a high signal-to-noise ratio (SNR) and a MHz bandwidth. It employs inductive-capacitive coupling (LC coupling), AC / DC separation, and transimpedance amplification. The photocurrent generated by each quadrant of the 16-quadrant photodiodes is converted into a voltage signal by sampling resistor R21. This voltage signal is then connected to an operational amplifier U23, resistors R22, R28, and R29 to form a non-inverting amplifier circuit. The output signal is connected to an oscilloscope for real-time monitoring of light intensity changes in each quadrant. The AC signal passes through capacitor C17, enters transimpedance amplifier U18, and is output through capacitor C19 to a spectrum analyzer. The signal conditioning circuit structure connected to the photodiodes in each quadrant is identical. A feedthrough capacitor is installed at the power supply point of the 16-quadrant photodetector. This feedthrough capacitor is directly mounted on the metal panel, effectively preventing high-frequency signals from coupling from the input to the output, providing ideal capacitor filtering and improving the detector's SNR.

[0023] 2. The power conversion circuit used in this invention can output ultra-low noise DC voltage. The power conversion circuit includes four power conversion units, each of which supplies power to four signal conditioning circuits. Each power conversion unit uses MC7806 and MC7906 voltage regulator chips to output ±6V, which supplies power to ultra-low noise voltage regulator chips TPS7A4701 and TPS7A3301, respectively. The ultra-low noise voltage regulator chips output ±5V to supply power to four transimpedance amplifiers. RC filter circuits and multi-stage ceramic bypass capacitors are connected to the power supply of the transimpedance amplifiers to reduce amplifier noise coupling and further improve the signal-to-noise ratio of the detector.

[0024] 3. In the detector of this invention, the 16-quadrant photodiode, signal conditioning circuit, and power conversion circuit are all mounted on a PCB board, using a four-layer PCB design. The middle two layers are the power layer and ground layer, respectively, and the top and bottom layers are the top and bottom layers, respectively. All components are arranged on the top layer. Excessive input trace length can easily couple noise to the AC output port. The transimpedance amplifier is closest to the 16-quadrant photodiode and is placed below the PCB board in a straight line arrangement. Above it are the ultra-low noise voltage regulator chip and operational amplifier. The output terminal uses an SSMA connector to output AC and DC signals, which greatly improves the detector's anti-electromagnetic interference performance and prevents crosstalk between pixels. This ensures that the AC and DC responses of each quadrant of the 16-quadrant photodetector are consistent, with an extremely high signal-to-noise ratio and wide linear range within the MHz bandwidth. It can realize the measurement of multi-quadrant laser intensity noise in the MHz bandwidth and the measurement of multi-quadrant noise spectrum of non-classical optical fields in this frequency band. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of a 16-quadrant photodetector with a MHz bandwidth and high signal-to-noise ratio, provided in Embodiment 1 of the present invention.

[0026] Figure 2 This is a circuit diagram of a 16-quadrant photodetector with a MHz bandwidth and high signal-to-noise ratio, provided in Embodiment 2 of the present invention.

[0027] Figure 3 This is a circuit diagram of the +5V power supply in Embodiment 2 of the present invention;

[0028] Figure 4 This is a circuit diagram of the -5V power supply in Embodiment 2 of the present invention;

[0029] Figure 5 This is a schematic diagram of the device layout of a MHz bandwidth, high signal-to-noise ratio, 16-quadrant photodetector provided in Embodiment 3 of the present invention;

[0030] Figure 6 This is a schematic diagram of a 16-quadrant photodetector performance testing system with a MHz bandwidth and high signal-to-noise ratio according to an embodiment of the present invention.

[0031] Figure 7 The linear range diagram of a Coherent Company Mira 900 mode-locked femtosecond pulsed laser in the first quadrant (0-5MHz) of a 16-quadrant photodetector with a high signal-to-noise ratio (SNR) MHz bandwidth photodetector in an embodiment of the present invention is shown.

[0032] Figure 8 This is a noise diagram of equal optical power incident intensity in the first and second quadrants (0-5MHz) of a 16-quadrant photodetector with a MHz bandwidth and high signal-to-noise ratio according to an embodiment of the present invention. Detailed Implementation

[0033] 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. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] Example 1

[0035] like Figure 1 As shown, Embodiment 1 of the present invention provides a 16-quadrant photodetector with a high signal-to-noise ratio of MHz bandwidth, including 16 photodiodes. The 16-quadrant photodiodes include 16 photodiodes D1 to D16. Each photodiode has a common cathode and is connected to the positive voltage terminal. The anode of each photodiode is connected to a corresponding signal conditioning circuit. The structure of each signal conditioning circuit is the same.

[0036] like Figure 1 As shown, the signal conditioning circuit includes: capacitor C17, transimpedance amplifier U18, capacitor C19, inductor L20, sampling resistor R21, resistor R22, and operational amplifier U23; one end of capacitor C17 is connected to the anode of the corresponding photodiode, and the other end is connected to the input terminal of transimpedance amplifier U18. The output terminal of transimpedance amplifier U18 is connected to AC output terminal AC1 via capacitor C19; one end of inductor L20 is connected to the anode of the corresponding photodiode, and the other end is connected to one end of sampling resistor R21 and resistor R22. The other end of sampling resistor R21 is grounded, and the other end of resistor R22 is connected to the input terminal of operational amplifier U23. The output terminal of operational amplifier U23 is connected to DC output terminal DC1.

[0037] Specifically, in this embodiment, the DC output terminal DC1 is used to monitor the light intensity of the photodiode in the corresponding quadrant, and the AC output terminal AC1 is used to monitor the intensity noise of the photodiode in the corresponding quadrant.

[0038] Specifically, the 16-quadrant photodiode used in this embodiment is an S8558. The positive voltage of the power supply is 9V. The inductance L of inductor L20 is 1.12mH, the sampling resistor R21 has a resistance of 100Ω, and the resistor R22 has a resistance of 1kΩ.

[0039] Example 2

[0040] like Figure 2As shown, Embodiment 2 of the present invention provides a 16-quadrant photodetector with a high signal-to-noise ratio of MHz bandwidth. Similar to Embodiment 1, it includes 16-quadrant photodiodes and 16 signal conditioning circuits. In the 16-quadrant photodiodes, each photodiode has a common cathode and is connected to the positive voltage terminal. The anode of each photodiode is connected to a corresponding signal conditioning circuit. The structure of each signal conditioning circuit is the same. The signal conditioning circuit includes: capacitor C17, transimpedance amplifier U18, capacitor C19, inductor L20, sampling resistor R21, resistor R22, and operational amplifier U23.

[0041] Unlike Embodiment 1, in this embodiment, the signal conditioning circuit further includes capacitors C25, C26, and C27. One end of capacitor C17 is connected to the inverting input of the transimpedance amplifier U18. One end of capacitor C25 is connected to the inverting input of the transimpedance amplifier U18, and the other end is connected to the output of the transimpedance amplifier U18 via capacitor C26. One end of capacitor C27 is connected to the other end of capacitor C25, and the other end is grounded. In this embodiment, capacitors C25, C26, and C27 are connected in a T-type network and connected in parallel with the transimpedance amplifier U18.

[0042] Furthermore, in this embodiment, the signal conditioning circuit further includes a feedback resistor R24; the feedback resistor R24 ​​is connected in parallel with the transimpedance amplifier U18, that is, one end of it is connected to the inverting input terminal of the transimpedance amplifier U18, and the other end is connected to the output terminal of the transimpedance amplifier U18, and its resistance value is 200kΩ.

[0043] Specifically, in this embodiment, the transimpedance amplifier U18 is model OPA818. OPA818 is a low-noise, high-gain-bandwidth product chip with a gain-bandwidth product of 2.7 GHz and an input voltage noise density of [missing information]. Input current noise density is The non-inverting input of transimpedance amplifier U18 is grounded. A 200kΩ feedback resistor R24 ​​and capacitors C25, C26, and C27 are connected in parallel between the inverting input and the output. The calculated gain is 200kV / A. Capacitors C25, C26, and C27 are connected to form a T-network with an equivalent capacitance of 0.067pF. Among them, capacitor C17 is 1uF and capacitor C19 is 0.1uF. The output of transimpedance amplifier U18 is connected to the output of AC1 via capacitor C19. The output of AC1 is used to measure the intensity noise of MHz bandwidth laser and the noise spectrum of non-classical optical fields in this quadrant.

[0044] Furthermore, in this embodiment, the signal conditioning circuit further includes resistors R28 and R29. The other end of resistor R22 is connected to the non-inverting input terminal of operational amplifier U23. The inverting input terminal of operational amplifier U23 is grounded through resistor R28, and the inverting input terminal of operational amplifier U23 is connected to the output terminal through resistor R29.

[0045] Furthermore, in this embodiment, the operational amplifier U23 is model OPA2227, which is a dual-channel high-precision low-noise operational amplifier. The resistor R28 has a resistance of 50Ω, the resistor R29 has a resistance of 1kΩ, and the amplification factor is 21 times. The output terminal of the operational amplifier U23 is connected to the DC output port DC1, and the DC1 signal is connected to an oscilloscope for real-time monitoring of the light intensity changes in the corresponding quadrant.

[0046] Furthermore, the MHz bandwidth high signal-to-noise ratio 16-quadrant photodetector of this embodiment also includes a power conversion circuit, which includes four power conversion units, each power conversion unit supplying power to four signal conditioning circuits therein.

[0047] like Figure 3 The diagram shows the circuit schematic for providing a +5V DC voltage in the power conversion unit. It includes capacitor C30, a first voltage regulator chip U31, capacitors C32, C33, and C34, a second voltage regulator chip U35 with ultra-low noise voltage, resistors R36 and R37, and capacitor C38. The IN port of the first voltage regulator chip U31 is connected to the +9V voltage and one end of capacitor C30, while the other end of capacitor C30 is grounded. The GND port of the first voltage regulator chip U31 is grounded, and the OUT port is connected to one end of capacitors C32 and C33 for input voltage. Output +6V voltage. The other ends of capacitors C32 and C33 are grounded. The IN and EN ports of the second voltage regulator chip U35 are connected to one end of capacitor C33. The NR port of the second voltage regulator chip U35 is connected to one end of capacitor C34. The other end of capacitor C34 is grounded. The OUT port is connected to one end of resistor R36 and capacitor C38 to output +5V voltage. The other end of resistor R36 is connected to the FB port and one end of resistor R37. The other end of resistor R37 is grounded. The GND port of the second voltage regulator chip U35 is grounded.

[0048] Specifically, in this embodiment, the first voltage regulator chip U31 is model MC7806, capacitor C30 is 0.22uF, capacitor C32 is 0.1uF, capacitor C33 is 10uF, and capacitor C34 is 1uF; the second voltage regulator chip U35 is model TPS7A4701, resistor R36 is 16kΩ, resistor R37 is 6.2kΩ, and capacitor C38 is 10uF.

[0049] like Figure 4 The diagram shows the circuit schematic for providing a -5V DC voltage in the power conversion unit. It includes capacitor C39, third voltage regulator chip U40, capacitors C41, C42, and C43, fourth voltage regulator chip U44 with ultra-low noise voltage, capacitor C45, resistor R46, resistor R47, and capacitor C48. Unlike the +5V voltage supply, the IN port of the third voltage regulator chip U40 is connected to a -9V voltage. One end of capacitor C45 is connected to the OUT port of the fourth voltage regulator chip U44, and the other end is connected to the FB port.

[0050] Specifically, in this embodiment, the third voltage regulator chip U40 is model MC7906, capacitor C39 is 0.22uF, capacitor C41 is 1uF, capacitor C42 is 10uF, and capacitor C43 is 1uF; the fourth voltage regulator chip U44 is model TPS7A3301, capacitor C45 is 10nF, resistor R46 is 220kΩ, resistor R47 is 68kΩ, and capacitor C48 is 10uF.

[0051] Example 3

[0052] Embodiment 3 of this invention provides a 16-quadrant photodetector with a MHz bandwidth and high signal-to-noise ratio. Its circuit structure is the same as that of Embodiment 2. The difference is that in this embodiment, all circuits are mounted on a PCB board, using a four-layer PCB design. The middle two layers are the power and ground layers, and the top and bottom layers are the top and bottom layers, respectively. All components are located on the top layer. Excessive input trace length can easily couple noise to the AC output port. The transimpedance amplifier OPA818 is closest to the 16-quadrant photodiode S8558. Figure 5 As shown, Embodiment 3 of the present invention is a schematic diagram of the component layout of a 16-quadrant photodetector with a MHz bandwidth and high signal-to-noise ratio. The transimpedance amplifier OPA818 is arranged in a line below the PCB board, with an ultra-low noise voltage regulator chip TPS7A4701 above it. TPS7A3301 provides power to the chip, and the operational amplifier OPA2227 is also present. The output interface uses an SSMA connector to output AC and DC signals for each quadrant. For example... Figure 5 As shown, the MHz bandwidth high signal-to-noise ratio 16-quadrant photodetector uses four sets of voltage regulator chips MC7806 and MC7906 to output ±6V, which power four sets of ultra-low noise voltage regulator chips TPS7A4701 and TPS7A3301 respectively. Each set of ultra-low noise voltage regulator chips outputs ±5V to power four transimpedance amplifiers OPA818.

[0053] The MHz bandwidth, high signal-to-noise ratio 16-quadrant photodetector provided by this invention uses a 16-quadrant photodiode. The photocurrent generated in the first quadrant is sampled by resistor R21 to generate a voltage signal. This voltage signal is then output by an operational amplifier U23, resistors R22, R28, and R29 forming a non-inverting amplifier circuit. The output DC1 signal is connected to an oscilloscope for real-time monitoring of light intensity changes in the first quadrant. The AC signal passes through capacitor C17, enters a transimpedance amplifier U18, and outputs an AC1 signal via capacitor C19, which is connected to a spectrum analyzer. The connection method for the remaining quadrants is the same as that for the first quadrant. The detector output terminal AC1 provided by this invention, as a MHz signal output terminal, has advantages such as low noise, high gain, and wide linear range. It can realize the measurement of multi-quadrant laser intensity noise in a MHz bandwidth and the multi-quadrant noise spectrum measurement of non-classical optical fields in this frequency band.

[0054] like Figure 6 The diagram shows a performance testing device for a 16-quadrant photodetector with a MHz bandwidth and high signal-to-noise ratio provided by the present invention. The device includes: a laser 49, a first high-reflectivity mirror 50, a second high-reflectivity mirror 51, a 16-quadrant photodetector with a MHz bandwidth and high signal-to-noise ratio 52, an oscilloscope 53, and a spectrum analyzer 54. The first and second high-reflectivity mirrors 50 and 51 reflect the light beam emitted from the laser 49. The 16-quadrant photodetector 52 receives the light beams reflected by the first and second high-reflectivity mirrors 50 and 51, respectively. The 16-quadrant photodetector 52 is connected to the oscilloscope 53 and the spectrum analyzer 54. The laser 49 is a Coherent Mira900 mode-locked femtosecond pulsed laser, outputting a pulsed laser with a center wavelength of 850 nm, a pulse width of 130 fs, and a repetition frequency of 76 MHz. Both the first and second high-reflectivity mirrors 50 and 51 are 45° 850 nm high-reflectivity mirrors.

[0055] Figure 7 The linear range of the Mira900 mode-locked femtosecond pulsed laser from Coherent Technologies is plotted in the first quadrant (0-5 MHz detector). The detector's AC1 output port is connected to a spectrum analyzer, which is set to a frequency range of 0-5 MHz. The spectral lines, from bottom to top, represent the detector's electronic noise and the intensity noise measured at 850 nm laser injection power of 50 μW, 100 μW, 200 μW, 400 μW, and 800 μW, respectively. At an incident power of 50 μW, the intensity noise at 1 MHz is 13 dB higher than the electronic noise. At an incident power of 800 μW, the intensity noise is 25 dB higher than the electronic noise. Furthermore, within the analysis frequency range of 5 MHz, the intensity noise is more than 10 dB higher than the electronic noise. The detector's linear range is 800 μW. The test results in the other quadrants are the same as those in the first quadrant. Therefore, the detector provided by this invention has an extremely high signal-to-noise ratio and a wide linear range.

[0056] Figure 8 The present invention provides a 16-quadrant photodetector with a high signal-to-noise ratio (SNR) of MHz bandwidth, and features incident intensity noise maps of equal optical power (0-5MHz) in the first and second quadrants. Each AC output port of the detector is connected to a spectrum analyzer, which is set to a frequency range of 0-5MHz. The injected optical power is 100µW. The dark chromatogram lines, from bottom to top, represent the electronic noise in the first quadrant and the intensity noise measured with 100µW of injected optical power. The light chromatogram lines, from bottom to top, represent the electronic noise in the second quadrant and the intensity noise measured with 100µW of injected optical power. The electronic noise in the first quadrant and the intensity noise with 100µW of injected optical power overlap with the second quadrant. The test results for the remaining quadrants are the same as those for the first and second quadrants. The AC and DC responses of the detector in each quadrant are consistent, pixels do not crosstalk, and the detector has strong anti-electromagnetic interference capabilities.

[0057] In summary, this invention provides a 16-quadrant photodetector with a high signal-to-noise ratio and a MHz bandwidth. It employs inductive-capacitive coupling (LC coupling) with AC / DC separation and transimpedance amplification. The photocurrent generated by each quadrant of the 16-quadrant photodiodes is converted into a voltage signal by sampling resistor R21. This voltage signal is then connected to an operational amplifier U23, resistors R22, R28, and R29 to form a non-inverting amplifier circuit. The output signal is connected to an oscilloscope for real-time monitoring of light intensity changes in each quadrant. The AC signal passes through capacitor C17, enters transimpedance amplifier U18, and is output through capacitor C19 to a spectrum analyzer. The signal conditioning circuit structure connected to the photodiodes in each quadrant is identical. A feedthrough capacitor is installed at the power supply point of the 16-quadrant photodetector. This feedthrough capacitor is directly mounted on the metal panel, effectively preventing high-frequency signals from coupling from the input to the output, thus providing the filtering effect of an ideal capacitor. The power conversion circuit used in this invention includes four power conversion units. Each power conversion unit supplies power to four signal conditioning circuits. Each power conversion unit uses MC7806 and MC7906 voltage regulator chips to output ±6V, which supplies power to ultra-low noise voltage regulator chips TPS7A4701 and TPS7A3301, respectively. The ultra-low noise voltage regulator chips output ±5V to supply power to four transimpedance amplifiers. RC filter circuits and multi-stage ceramic bypass capacitors are connected to the power supply of each transimpedance amplifier to reduce amplifier noise coupling. The 16-quadrant photodiode, signal conditioning circuit, and power conversion circuit are all mounted on a PCB board using a four-layer PCB design. The middle two layers are the power and ground layers, respectively, while the top and bottom layers are the top and bottom layers. All components are placed on the top layer. Excessive input trace length can easily couple noise to the AC output port. The transimpedance amplifier is closest to the 16-quadrant photodiode and is placed below the PCB board in a straight line arrangement. Above it are the ultra-low noise voltage regulator chip and operational amplifier. The output terminal uses an SSMA connector to output AC and DC signals, which greatly improves the detector's anti-electromagnetic interference performance and prevents crosstalk between pixels. The designed 16-quadrant photodetector has consistent AC and DC responses in each quadrant, and has an extremely high signal-to-noise ratio and wide linear range within a MHz bandwidth. It can realize the measurement of multi-quadrant laser intensity noise and non-classical optical field noise spectrum in this frequency band within a MHz bandwidth.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A MHz bandwidth, high signal-to-noise ratio, 16-quadrant photodetector, characterized in that, The system includes 16 photodiodes, comprising 16 photodiodes. Each photodiode shares a common cathode and is connected to the positive terminal via a feedthrough capacitor. The anode of each photodiode is connected to a corresponding signal conditioning circuit. All signal conditioning circuits have the same structure and include: Capacitor C17, transimpedance amplifier U18, capacitor C19, inductor L20, sampling resistor R21, resistor R22, operational amplifier U23; One end of capacitor C17 is connected to the anode of the corresponding photodiode, and the other end is connected to the input terminal of transimpedance amplifier U18. The output terminal of transimpedance amplifier U18 is connected to AC output terminal AC1 via capacitor C19. One end of inductor L20 is connected to the anode of the corresponding photodiode, and the other end is connected to one end of sampling resistor R21 and resistor R22. The other end of sampling resistor R21 is grounded, and the other end of resistor R22 is connected to the input terminal of operational amplifier U23. The output terminal of operational amplifier U23 is connected to DC output terminal DC1. It also includes a power conversion circuit, which comprises four power conversion units, each power conversion unit supplying power to four signal conditioning circuits therein, and each power conversion unit comprising: The system comprises a first voltage regulator chip, a second voltage regulator chip, a third voltage regulator chip, and a fourth voltage regulator chip. The first voltage regulator chip is used to convert an external positive voltage into a +6V DC voltage, and the second voltage regulator chip is used to convert the +6V DC voltage into a +5V DC voltage for output. The third voltage regulator chip is used to convert the external negative voltage into a -6V DC voltage, and the fourth voltage regulator chip is used to convert the -6V DC voltage into a -5V DC voltage before outputting it. The first, second, third, and fourth voltage regulator chips are MC7806, TPS7A4701, MC7906, and TPS7A3301, respectively. The IN port of the first voltage regulator chip is connected to a +9V voltage and one end of capacitor C30, the other end of capacitor C30 is grounded, the GND port of the first voltage regulator chip is grounded, the OUT port is connected to one end of capacitors C32 and C33 and outputs a +6V voltage, the other ends of capacitors C32 and C33 are grounded, the IN port of the second voltage regulator chip is connected to the EN port and one end of capacitor C33, the NR port of the second voltage regulator chip is connected to one end of capacitor C34, the other end of capacitor C34 is grounded, the OUT port is connected to one end of resistor R36 and capacitor C38 and outputs a +5V voltage, the other end of resistor R36 is connected to the FB port and one end of resistor R37, the other end of resistor R37 is grounded, and the GND port of the second voltage regulator chip is grounded; The IN port of the third voltage regulator chip is connected to a -9V voltage and one end of capacitor C39, with the other end of capacitor C39 grounded. The GND port of the third voltage regulator chip is grounded. The OUT port is connected to one end of capacitors C41 and C42, outputting a -6V voltage. The other ends of capacitors C41 and C42 are grounded. The IN port of the fourth voltage regulator chip is connected to the EN port and one end of capacitor C42. The NR port of the fourth voltage regulator chip is grounded via capacitor C43. The OUT port is connected to one end of resistor R46 and capacitor C48, outputting a -5V voltage. The other end of resistor R46 is connected to the FB port of the fourth voltage regulator chip and one end of resistor R47, with the other end of resistor R47 grounded. The GND port of the fourth voltage regulator chip is grounded. Capacitor C45 is placed between the FB port and the OUT port of the fourth voltage regulator chip.

2. The MHz bandwidth high signal-to-noise ratio 16-quadrant photodetector according to claim 1, characterized in that, The DC output terminal DC1 is used to monitor the light intensity of the photodiode in the corresponding quadrant, and the AC output terminal is used to monitor the intensity noise of the photodiode in the corresponding quadrant.

3. The MHz bandwidth high signal-to-noise ratio 16-quadrant photodetector according to claim 1, characterized in that, It also includes a PCB board, on which the 16-quadrant photodiode, signal conditioning circuit and power conversion circuit are all mounted. Each transimpedance amplifier U18 is mounted on the side closest to the 16-quadrant photodiode, and the power conversion circuit and operational amplifier U23 are mounted outside the transimpedance amplifier U18.

4. The MHz bandwidth high signal-to-noise ratio 16-quadrant photodetector according to claim 1, characterized in that, The 16-quadrant photodiode is model S8558, the inductance of inductor L20 is 1.12mH, and the sampling resistor R21 has a resistance of 100Ω.

5. The MHz bandwidth high signal-to-noise ratio 16-quadrant photodetector according to claim 1, characterized in that, The signal conditioning circuit also includes a feedback resistor R24, capacitors C25, C26, and C27. One end of the feedback resistor R24 ​​is connected to the inverting input of the transimpedance amplifier U18, and the other end is connected to the output of the transimpedance amplifier U18. The other end of the capacitor C17 is connected to the inverting input of the transimpedance amplifier U18. One end of the capacitor C25 is connected to the inverting input of the transimpedance amplifier U18, and the other end is connected to the output of the transimpedance amplifier U18 via capacitor C26. One end of the capacitor C27 is connected to the other end of the capacitor C25, and the other end is grounded.

6. A MHz bandwidth high signal-to-noise ratio 16-quadrant photodetector according to claim 5, characterized in that, The transimpedance amplifier U18 is model OPA818. The capacitance values ​​of capacitors C25, C26 and C27 are 2.2pF, 2.2pF and 68pF respectively. The capacitance values ​​of capacitors C17 and C19 are 1uF and 0.1uF respectively. The resistance value of feedback resistor R24 ​​is 200kΩ.

7. The MHz bandwidth high signal-to-noise ratio 16-quadrant photodetector according to claim 1, characterized in that, The signal conditioning circuit also includes resistors R28 and R29. The other end of resistor R22 is connected to the non-inverting input of operational amplifier U23. The inverting input of operational amplifier U23 is grounded through resistor R28. The inverting input of operational amplifier U23 is connected to the output through resistor R29.

8. A MHz bandwidth high signal-to-noise ratio 16-quadrant photodetector according to claim 7, characterized in that, The operational amplifier U23 is model OPA2227, the resistor R28 has a resistance of 50Ω, and the resistor R29 has a resistance of 1kΩ.

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