Avalanche photodetector with integrated filter amplifier chip and driving method thereof

Abstract

The present invention discloses an avalanche photodetector with an integrated filter amplifier chip, including an APD chip, a refrigerator and an avalanche signal processing chip. The output end of the APD chip is electrically connected to the signal input end of the avalanche signal processing chip, and the output end of the avalanche signal processing chip outputs a processed avalanche signal. The APD chip is closely attached to the cold end surface of the refrigerator. The avalanche signal processing chip is used to suppress the gated signal and the second and higher harmonic signals in the original avalanche signal output by the APD chip, and to perform targeted filtering and low-noise amplification on the avalanche signal. The avalanche signal processing chip integrates the functions of a filter and a low-noise amplifier. The APD chip, the refrigerator and the avalanche signal processing chip are integrally packaged in a housing. The present invention also discloses a driving method of the avalanche photodetector. The advantages of the present invention are that the avalanche photodetector with an integrated filter amplifier chip has a small size and mass, a simple circuit structure, low power consumption and stable detection efficiency.

Description

Technical Field

[0001] The present invention relates to the field of photoelectric detection technology, and more specifically to an avalanche photoelectric detector with an integrated filter amplifier chip and a driving method thereof. Background Art

[0002] With the continuous development of photoelectric detection technology, single-photon detection has been widely used in the detection of weak signals due to its high sensitivity, thus promoting the progress of biological fluorescence detection, spectral measurement, lidar, optical quantum information processing, fiber optic sensing and other fields. Especially in the field of quantum communication, single-photon detectors play a vital role in both quantum random number generators and quantum key distribution technologies. At present, quantum communication technology has gradually become practical, commercialized and integrated. Therefore, further requirements have been put forward for the size, power consumption and stability of single-photon detectors. Avalanche photodiode (APD) is one of the core components of single-photon detectors and determines the sensitivity of the detector. By reducing the temperature of the APD working environment, its dark current noise can be reduced, thereby greatly improving the sensitivity of single-photon detectors.

[0003] The prior art uses a clamp to fix the APD tube on the cooling surface of a semiconductor cooler (TEC). The heat generated by the APD tube is transferred to the TEC through the tube shell, and the TEC cools the entire APD tube. This method has low cooling efficiency and usually requires the use of multi-stage TEC, resulting in high power consumption. When the APD tube is working, it is necessary to provide bias current and dynamic driving voltage to the APD through an external driving circuit module. Since the original avalanche signal output by the APD is mixed with strong gating and second and higher harmonic interference signals, an avalanche detection readout circuit module is also required to process the original avalanche signal output by the APD and extract the photocurrent generated by the detection. The avalanche detection readout circuit module first needs to take targeted filtering measures to greatly suppress the gating signal interference in the background, while trying not to change the avalanche signal amplitude. Next, it is also necessary to use a low-noise amplifier unit to amplify the filtered avalanche signal. The current detector's driving circuit, filter, and low-noise amplifier unit are all cascaded on the PCB through discrete circuits, which greatly increases the overall size and weight of the detector in actual use. At the same time, the cascade of multiple discrete circuits will also introduce additional noise and crosstalk. In order to reduce its negative impact, it is necessary to add a shielding cover to this part of the circuit to improve the electromagnetic field spatial coupling and digital control signal crosstalk, which increases the complexity of system design and production. In addition, each circuit needs to be driven by a power supply, which makes the detector drive complex and power consumption high.

[0004] Since the above scheme has low cooling efficiency, high power consumption and large size, relevant researchers have proposed an integrated solution of packaging TEC in an avalanche photodiode. Patent publication number CN 107167251A discloses an overall solution of an integrated cooling avalanche photodetector, such as Figure 1 As shown, the detector includes an avalanche photodiode 100, a DC bias voltage generating circuit unit 200, a sinusoidal gate pulse generating circuit unit 300, a filter amplifying and shaping circuit unit 400, a temperature control circuit unit 500 and an FPGA circuit unit 600. The solution integrates the thermistor and the semiconductor cooler into the package of the avalanche photodiode 100, which improves the cooling efficiency to a certain extent. However, only realizing the integrated package of APD and TEC is not enough to support the miniaturization of the overall size of the detector. In actual use, the solution still needs to connect the following multiple discrete circuit units outside the APD package structure to work properly: a DC bias voltage generating circuit unit, a sinusoidal gate pulse generating circuit unit, a filter amplifying and shaping circuit unit, a temperature control circuit unit and an FPGA circuit unit. Therefore, the actual size of the detector still has more than two orders of magnitude of improvement space.

[0005] In terms of cooling methods, the prior art uses a constant voltage source to power the semiconductor cooling chip so that it works at the maximum cooling power. Patent No. CN 103557950 discloses a single-photon detector with stable efficiency and a control method, such as Figure 2 As shown, the single-photon detector in this scheme includes a stable voltage source, a cooling box, a single-chip microcomputer, a high-voltage module, a semiconductor cooling piece, an APD and a thermistor. The APD and the thermistor are fixed on the semiconductor cooling piece, and the three are packaged together in the cooling box. The stable voltage source is electrically connected to the semiconductor cooling piece, the thermistor and the high-voltage module are connected to the single-chip microcomputer, and the high-voltage module is connected to the APD to provide a driving voltage for it. The semiconductor cooling piece works at the maximum cooling power. When the working environment temperature of the APD changes, the resistance of the thermistor changes with the temperature in the cooling box, and transmits the temperature signal to the single-chip microcomputer. The single-chip microcomputer controls the output of the high-voltage module according to the temperature signal, thereby controlling the bias voltage of the APD.

[0006] The use of a constant cooling power will cause the temperature inside the refrigeration box to change with the external environment temperature, resulting in poor temperature stability. In order to compensate for the change in APD detection efficiency caused by changes in external temperature, the prior art uses a method of changing the APD reverse bias voltage as the temperature changes to control its detection efficiency. However, as the APD reverse bias voltage changes, its dark current changes, which will cause changes in dark counts and affect the detection error rate. That is, changing the APD reverse bias voltage will affect the stability of the detection output to a certain extent. Summary of the invention

[0007] The technical problem to be solved by the present invention is that the detector in the prior art has large size and mass, complex external circuits, signal crosstalk between circuits and large signal noise.

[0008] The present invention solves the above technical problems through the following technical solutions: an avalanche photodetector with integrated filter amplifier chip, including an APD chip and a refrigerator, and also including an avalanche signal processing chip, the output end of the APD chip is electrically connected to the signal input end of the avalanche signal processing chip, the output end of the avalanche signal processing chip outputs the processed avalanche signal, the APD chip is closely attached to the cold end surface of the refrigerator, the avalanche signal processing chip is used to suppress the gated signal and the second and above harmonic signals in the original avalanche signal output by the APD chip, and filter and low-noise amplify the avalanche signal; the avalanche signal processing chip integrates the functions of the filter and the low-noise amplifier, and the APD chip, the refrigerator and the avalanche signal processing chip are integrally packaged in a shell. The present invention proposes an avalanche photodetector with integrated filter amplifier chip, which realizes the chip integration of APD and the chip integration of the avalanche signal processing circuit connected to the output end of APD, and is packaged in a shell with good heat dissipation effect. The detector no longer needs to be connected to a complex peripheral circuit, which greatly reduces the device size and improves the integration.

[0009] Preferably, the avalanche photodetector with integrated filter amplifier chip also includes an APD driver chip, the input end of the APD chip is electrically connected to the APD driver chip, and the APD driver chip is also packaged in the housing. The present invention proposes an avalanche photodetector with integrated filter amplifier chip, which further realizes chip integration of a drive circuit connected to the APD input end, further reduces the device size, and improves the integration level.

[0010] Preferably, the avalanche photodetector with integrated filter amplifier chip also includes a ceramic substrate, the APD chip is arranged in the cooling area of ​​the ceramic substrate, the avalanche signal processing chip and the APD driver chip are arranged in the non-cooling area of ​​the ceramic substrate, and the ceramic substrate is also encapsulated in the shell.

[0011] Preferably, the avalanche photodetector with integrated filter amplifier chip further comprises a thermistor, wherein the thermistor is arranged in the cooling area of ​​the ceramic substrate, close to the APD chip, and the thermistor is also packaged in the housing.

[0012] Preferably, the avalanche photodetector with integrated filter amplifier chip also includes a temperature control circuit, which includes a temperature acquisition ADC, a processor and a refrigerator driver. The temperature acquisition ADC is connected in parallel at both ends of the thermistor, and the refrigerator driver is connected to the refrigerator. One end of the processor is connected to the temperature acquisition ADC, and the other end is connected to the refrigerator driver. The temperature control circuit is arranged in the non-refrigeration area of ​​the ceramic substrate and is also encapsulated in the housing. During the operation of the detector, the cooling power of the refrigerator is adjusted according to the temperature change, so that the APD works in a stable low-temperature environment, and the reverse bias voltage and the gate signal size remain unchanged, thereby ensuring that the APD dark current noise is low and the sensitivity is high, so that the detector can maintain a stable detection efficiency.

[0013] Preferably, the cooling area and the non-cooling area of ​​the ceramic substrate are heat-insulated. The only chip in the detector that needs to work in a low-temperature environment (-55°C) is the APD chip, while the APD driver chip and the LTCC chip can also work normally at room temperature. Therefore, heat-insulating them can improve the cooling effect of the APD chip.

[0014] Preferably, the refrigerator is only arranged in the cooling area of ​​the ceramic substrate; further, the non-cooling area of ​​the ceramic substrate can also be temperature-controlled separately, so as to achieve heat insulation between the cooling area and the non-cooling area of ​​the ceramic substrate.

[0015] Preferably, the avalanche signal processing chip is an LTCC chip. The LTCC chip is a chip with filtering and amplification functions, integrating the functions of a filter and a low noise amplifier.

[0016] Preferably, the LTCC chip includes a first filter, a second filter, a first low noise amplifier and a second low noise amplifier, the first filter, the first low noise amplifier, the second low noise amplifier and the second filter are connected in sequence by capacitor AC coupling, the input end of the first low noise amplifier is grounded through a first inductor and a first resistor connected in series, the input end of the second low noise amplifier is grounded through a second inductor and a second resistor connected in series, the output end of the first low noise amplifier is connected to a power supply voltage Vcc through a third inductor and a third resistor connected in series, and the output end of the second low noise amplifier is connected to the power supply voltage Vcc through a fourth inductor and a fourth resistor connected in series.

[0017] Further preferably, the LTCC chip further comprises a first capacitor, a second capacitor, a third capacitor and a fourth capacitor, wherein one end of the first capacitor is connected to the node between the first inductor and the first resistor, and the other end is grounded, one end of the second capacitor is connected to the node between the second inductor and the second resistor, and the other end is grounded, one end of the third capacitor is connected to the node between the third inductor and the third resistor, and the other end is grounded, and one end of the fourth capacitor is connected to the node between the fourth inductor and the fourth resistor, and the other end is grounded. The first capacitor, the second capacitor, the third capacitor and the fourth capacitor are used to filter out AC signals in the circuit to prevent the AC signals from coupling to the power supply circuit.

[0018] The present invention also provides a driving method for an avalanche photodetector, in which a voltage signal output by an APD driving chip drives the APD chip to work. At this time, if an optical signal reaches the photosensitive surface of the APD chip, an avalanche effect will occur in the APD chip, and the generated original avalanche signal will be output to an avalanche signal processing chip; the avalanche signal processing chip processes the original avalanche signal, filters the gate signal and the second and higher harmonic signal frequencies, filters out the interference of the high-frequency gate signal, and filters and low-noise amplifies the avalanche current caused by the optical signal, and then outputs it through the pin of the photodetector to realize the detection of the input optical signal.

[0019] Preferably, the avalanche photodetector also includes a thermistor. When the temperature of the APD chip changes, the resistance of the thermistor will change accordingly and be fed back to the processor through the temperature acquisition ADC. The processor controls the refrigerator drive according to the resistance feedback from the temperature acquisition ADC, and the refrigerator drive controls the cooling power of the refrigerator. That is, different cooling powers are adjusted according to different temperatures to keep the working temperature of the APD chip constant.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] 1) The present invention proposes an avalanche photodetector with integrated filter amplifier chip, which realizes the chip integration of APD and the chip integration of avalanche signal processing circuit connected to the output end of APD. The detector no longer needs to be connected to complex peripheral circuits, which greatly reduces the device size and improves the integration.

[0022] 2) The present invention proposes an avalanche photodetector with an integrated filter amplifier chip, which further realizes the chip integration of a driving circuit connected to the input end of the APD, further reduces the device size and improves the integration level.

[0023] 3) The present invention integrates an LTCC chip with filtering and amplifying functions into the detector. The detector signal output pin directly outputs the filtered and amplified avalanche signal, i.e., the photoelectric detection result. It is no longer necessary to process the original avalanche signal output by the APD through an external filtering circuit or a low-noise amplifier circuit, thereby simplifying the external circuit structure and reducing the overall size and weight of the detector in actual use.

[0024] 4) By replacing multiple discrete circuits with LTCC chips, the parasitic parameters of the signal link are reduced, the channel crosstalk between discrete circuits is reduced, the circuit noise is effectively reduced, and the complexity of system design and production is reduced.

[0025] 5) The present invention utilizes LTCC chips to implement the filtering and amplification function of the original avalanche signal, which greatly reduces the driving voltage and power consumption compared to the method of utilizing discrete circuit cascade.

[0026] 6) Through the design of the temperature control circuit, during the operation of the detector, the cooling power of the refrigerator is adjusted according to the temperature change, so that the APD works in a stable low-temperature environment, and the reverse bias voltage and the gate signal size remain unchanged, thereby ensuring that the APD dark current noise is low and the sensitivity is high. Therefore, the detector can maintain a stable detection efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solution of the present invention, the accompanying drawings required for use in the description of the present invention will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0028] Figure 1 It is a schematic diagram of the structure of an integrated refrigeration avalanche photodetector in the prior art;

[0029] Figure 2 This is a schematic diagram of a single-photon detector structure with stable efficiency in the prior art;

[0030] Figure 3 It is a circuit diagram of an avalanche photodetector with an integrated filter amplifier chip disclosed in Example 1 of the present invention;

[0031] Figure 4 It is a circuit schematic diagram of an LTCC chip of an avalanche photodetector with an integrated filter amplifier chip disclosed in an embodiment of the present invention;

[0032] Figure 5 is a circuit diagram of an avalanche photodetector with an integrated filter amplifier chip disclosed in Example 2 of the present invention;

[0033] Figure 6 is a circuit diagram of an avalanche photodetector with an integrated filter amplifier chip disclosed in Example 3 of the present invention;

[0034] Figure 7 It is a circuit diagram of an avalanche photodetector with an integrated filter amplifier chip disclosed in Example 4 of the present invention.

[0035] The numbers in the figure represent the corresponding parts names:

[0036] 1. First pin 2. Second pin 3. Third pin

[0037] 4. The fourth pin 5. The fifth pin 6. The sixth pin

[0038] 7. Seventh pin 8. Eighth pin 9. APD chip

[0039] 10.LTCC chip 11.Thermistor 12.Casing

[0040] 13. Temperature acquisition ADC 14. Processor 15. Refrigerator driver

[0041] 16. Ceramic substrate 17. APD driver chip 18. Refrigerator

[0042] 100. Avalanche photodiode 200. DC bias voltage generating circuit unit

[0043] 300. Sine gate pulse generating circuit unit 400. Filtering, amplifying and shaping circuit unit

[0044] 500. Temperature control circuit unit 600. FPGA circuit unit

[0045] 1001. First low-pass filter 1002. Second low-pass filter

[0046] 1003. First low noise amplifier 1004. Second low noise amplifier 1005. First inductor

[0047] 1006. First resistor 1007. Second inductor 1008. Second resistor

[0048] 1009. First capacitor 1010. Second capacitor 1011. Third inductor

[0049] 1012. third resistor 1013. fourth inductor 1014. fourth resistor

[0050] 1015. Third capacitor 1016. Fourth capacitor DETAILED DESCRIPTION

[0051] The following is a detailed description of an embodiment of the present invention. This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method and a specific operation process are given, but the protection scope of the present invention is not limited to the following embodiment.

[0052] Example 1

[0053] like Figure 3 As shown, an avalanche photodetector with integrated filter amplifier chip includes an APD chip 9 and an LTCC chip 10 (low temperature co-fired ceramic chip).

[0054] The output end of the APD chip 9 is electrically connected to the avalanche signal input end of the LTCC chip 10, the output end of the LTCC chip 10 outputs the processed avalanche signal, and the APD chip 9 is closely attached to the cold end surface of the refrigerator 18. The APD chip 9, the LTCC chip 10 and the refrigerator 18 are packaged in a housing 12.

[0055] The cold end surface of the refrigerator 18 is attached to the bottom of the APD chip 9, and can also be attached to the APD chip 9 from the top of the APD chip 9. And the cold end surface of the refrigerator 18 can be attached to the APD chip 9 through a heat conductive material.

[0056] The LTCC chip 10 is a chip with filtering and amplification functions. Optimally, the LTCC chip 10 integrates the functions of a filter and a low noise amplifier.

[0057] As a specific embodiment of the LTCC chip 10, Figure 4 As shown, the LTCC chip 10 includes a first low-pass filter 1001 , a second low-pass filter 1002 , a first low-noise amplifier 1003 and a second low-noise amplifier 1004 .

[0058] The first low-pass filter 1001, the first low-noise amplifier 1003, the second low-noise amplifier 1004 and the second low-pass filter 1002 are connected in sequence by means of capacitor AC coupling. The input end of the first low-noise amplifier 1003 is grounded through a first inductor 1005 and a first resistor 1006 connected in series. The input end of the second low-noise amplifier 1004 is grounded through a second inductor 1007 and a second resistor 1008 connected in series. One end of the first capacitor 1009 is connected to the node LB1 between the first inductor 1005 and the first resistor 1006, and the other end is grounded. One end of the second capacitor 1010 is connected to the node LB1 between the first inductor 1005 and the first resistor 1006, and the other end is grounded. 1007 and a node LB2 between the second resistor 1008, and the other end is grounded; the output end of the first low noise amplifier 1003 is connected to the power supply voltage Vcc through the third inductor 1011 and the third resistor 1012 connected in series; the output end of the second low noise amplifier 1004 is connected to the power supply voltage Vcc through the fourth inductor 1013 and the fourth resistor 1014 connected in series; one end of the third capacitor 1015 is connected to the node LD1 between the third inductor 1011 and the third resistor 1012, and the other end is grounded; one end of the fourth capacitor 1016 is connected to the node LD2 between the fourth inductor 1013 and the fourth resistor 1014, and the other end is grounded.

[0059] The circuits connected to the input and output ends of the first low noise amplifier 1003 and the second low noise amplifier 1004 provide a DC driving voltage for them. Specifically, for the first low noise amplifier 1003, the voltage at the node LD1 between the third inductor 1011 and the third resistor 1012 is the drain bias voltage of the first low noise amplifier 1003. The supply voltage Vcc passes through a third resistor 1012 with a stable bias voltage and then passes through the third inductor 1011 to provide a stable drain bias voltage to the first low noise amplifier 1003. The supply voltage Vcc passes through a fourth resistor 1014 with a stable bias voltage and then passes through the fourth inductor 1013 to provide a stable drain bias voltage to the second low noise amplifier 1004. The third capacitor 1015 connected in series beside LD1 is used to filter out the AC signal output by the first low noise amplifier 1003 to prevent the AC signal from coupling to the power supply circuit. Similarly, the fourth capacitor 1016 connected in series beside LD2 is used to filter out the AC signal output by the second low noise amplifier 1004 to prevent the AC signal from coupling to the power supply circuit. The voltage at the node LB1 between the first inductor 1005 and the first resistor 1006 is the base bias voltage of the first low noise amplifier 1003, wherein the first resistor 1006 connected in series to the ground and the first capacitor 1009 connected in parallel therewith are used to generate a suitable and stable base voltage, and the first inductor 1005 connected in series to the input terminal of the first low noise amplifier 1003 is used to suppress the external AC signal from flowing into the input terminal of the first low noise amplifier 1003. Similarly, the voltage at the node LD2 between the fourth inductor 1013 and the fourth resistor 1014 is the drain bias voltage of the second low noise amplifier 1004, and the voltage at the node LB2 between the second inductor 1007 and the second resistor 1008 is the base bias voltage of the second low noise amplifier 1004. The original avalanche signal output by the APD chip 9 passes through the first low-pass filter 1001 and then is AC-coupled to the first low-noise amplifier 1003 through a capacitor, and after low-noise amplification, it is AC-coupled to the second low-noise amplifier 1004 for amplification; the amplified signal is then AC-coupled to the final second low-pass filter 1002 for AC amplification, and finally the photocurrent generated by the detection is output.

[0060] The first low-pass filter 1001 and the second low-pass filter 1002 may also be notch filters.

[0061] The LTCC chip 10 is used as an avalanche signal processing chip, which is used to suppress the gate signal and the second and higher harmonic signals in the original avalanche signal output by the APD chip 9, and perform low-pass filtering and low-noise amplification on the avalanche signal.

[0062] The working principle of an avalanche photodetector with an integrated filter amplifier chip disclosed in Example 1 of the present invention is as follows: When the APD chip 9 is working, if an optical signal reaches the photosensitive surface of the APD chip 9, an avalanche effect will occur in the APD chip 9, and the generated original avalanche signal will be output to the LTCC chip 10. The LTCC chip 10 processes the original avalanche signal, filters the gate signal and the second and higher harmonic signal frequencies, and filters out the interference of the high-frequency gate signal. At the same time, the avalanche signal caused by the optical signal is low-pass filtered and low-noise amplified, thereby realizing the detection of the input optical signal.

[0063] Example 2

[0064] The difference between Embodiment 2 of the present invention and Embodiment 1 of the present invention is that:

[0065] The avalanche photodetector with integrated filter amplifier chip of this embodiment further integrates an APD driver chip.

[0066] like Figure 5 As shown, in addition to the same structure as in Example 1, the input end of the APD chip 9 is electrically connected to the APD driving chip 17, and the APD driving chip 17 provides a driving voltage for the APD chip 9.

[0067] The working principle of an avalanche photodetector with an integrated filter amplifier chip disclosed in Example 2 of the present invention is as follows: the APD driver chip 17 outputs a voltage signal to drive the APD chip 9 to work. At this time, if an optical signal reaches the photosensitive surface of the APD chip 9, an avalanche effect will occur in the APD chip 9, and the generated original avalanche signal will be output to the LTCC chip 10. The LTCC chip 10 processes the original avalanche signal, filters the gate signal and the second and higher harmonic signal frequencies, and filters out the interference of the high-frequency gate signal. At the same time, the avalanche signal caused by the optical signal is low-pass filtered and low-noise amplified, and the avalanche signal is output, thereby realizing the detection of the input optical signal.

[0068] In this embodiment, it is optimized that heat insulation treatment can be performed between the APD chip 9 and the APD driver chip 17 or the LTCC chip 10, and the heat insulation treatment includes placing the APD driver chip 17 or the LTCC chip 10 outside the refrigerator 18, or individually controlling the temperature of the APD driver chip 17 or the LTCC chip 10. The only chip in the detector that needs to work in a low-temperature environment (-55°C) is the APD chip 9. The APD driver chip 17 and the LTCC chip 10 can also work normally at room temperature. Therefore, the APD driver chip 17 and the LTCC chip 10 can be placed outside the refrigerator 18 without cooling them, but it should be noted that the heat between the chips is conducted to each other through the circuit connection, and air insulation measures can be taken or separate temperature control can be set for them to work at room temperature.

[0069] Example 3

[0070] The difference between Embodiment 3 of the present invention and Embodiment 2 of the present invention is that:

[0071] See also Figure 6 The avalanche photodetector further includes a ceramic substrate 16 , each chip can be placed on the ceramic substrate 16 , and the circuit connection between the chips can also be arranged on the ceramic substrate 16 , and the ceramic substrate 16 is packaged in the housing 12 .

[0072] Specifically, the ceramic substrate 16 is divided into a cooling area and a non-cooling area. The APD driver chip 17 and the LTCC chip 10 are arranged in the non-cooling area of ​​the ceramic substrate 16, and the APD chip 9 is arranged in the cooling area of ​​the ceramic substrate 16. Because the only chip in the detector that needs to work in a low-temperature environment (-55°C) is the APD chip 9, it is only necessary to place the APD chip 9 in the cooling area of ​​the ceramic substrate 16 for cooling. In this embodiment, the APD chip 9 is closely attached to the cold end surface of the refrigerator 18. The cold end surface of the refrigerator 18 can be directly attached to the bottom of the ceramic substrate 16 where the APD chip 9 is located, or it can be attached to the APD chip 9 from the top of the APD chip 9, thereby improving the cooling efficiency of the APD chip 9. The cooling area and the non-cooling area of ​​the ceramic substrate 16 are heat-insulated. The heat-insulating method can be that the refrigerator 18 is only arranged in the cooling area of ​​the ceramic substrate 16, and air insulation measures are taken between the cooling area and the non-cooling area of ​​the ceramic substrate 16, or the temperature of the non-cooling area of ​​the ceramic substrate 16 is separately controlled to make it work at room temperature.

[0073] Example 4

[0074] like Figure 7 As shown, the difference between Embodiment 4 of the present invention and Embodiment 3 of the present invention is that:

[0075] The avalanche photodetector of this embodiment integrates a temperature control function, and the specific structure is as follows:

[0076] An avalanche photodetector with integrated filter amplifier chip includes an APD driver chip 17, an APD chip 9, an LTCC chip 10 (low temperature co-fired ceramic chip), a thermistor 11, and a temperature control circuit. The photodetector has eight pins: a first pin 1 to an eighth pin 8. The thermistor 11 and the temperature control circuit are also packaged in the housing 12. The thermistor 11 is arranged in the cooling area of ​​the ceramic substrate 16, close to the APD chip 9, and the temperature control circuit is arranged in the non-cooling area of ​​the ceramic substrate 16.

[0077] The eighth pin 8 of the photodetector serves as the input end of the APD driver chip 17, and is connected to the power supply through the eighth pin 8; the output end of the APD driver chip 17 is connected to the input end of the APD chip 9, and provides a driving voltage for the APD chip 9; the output end of the APD chip 9 is electrically connected to the avalanche signal input end of the LTCC chip 10, and the output end of the LTCC chip 10 serves as the seventh pin 7 of the photodetector, outputting the processed avalanche signal; the sixth pin 6 of the photodetector serves as the driving signal input end of the LTCC chip 10, and inputs the driving signal; the grounding end of the LTCC chip 10 and the APD chip 9 serves as the third pin 3 of the photodetector. The two ends of the thermistor 11 serve as the first pin 1 and the second pin 2 of the photodetector, respectively. The fourth pin 4 and the fifth pin 5 of the photodetector are connected to the refrigerator 18.

[0078] It should be pointed out that, on the basis of ensuring that the functions remain unchanged, the positions of the first pin 1 to the eighth pin 8 can be changed according to the device or circuit layout connected thereto, and the positions in the schematic diagram are not the only limiting circumstances.

[0079] The temperature control circuit includes a temperature acquisition ADC 13, a processor 14, and a refrigerator driver 15. The temperature acquisition ADC 13 is connected in parallel to both ends of the thermistor 11, and the refrigerator driver 15 is connected to the refrigerator 18 through the fourth pin 4 and the fifth pin 5 of the photodetector. One end of the processor 14 is connected to the temperature acquisition ADC 13, and the other end is connected to the refrigerator driver 15.

[0080] The temperature control circuit provides a continuous low temperature environment for the APD chip 9 .

[0081] The working principle of an avalanche photodetector with an integrated filter amplifier chip disclosed in Example 4 of the present invention is as follows: the heat generated by the APD chip 9 is transmitted to the ceramic substrate 16, and the resistance of the thermistor 11 changes with the temperature of the ceramic substrate 16, and is fed back to the processor 14 through the temperature acquisition ADC13. The processor 14 controls the refrigerator driver 15 according to the resistance feedback from the temperature acquisition ADC13, thereby controlling the cooling power of the semiconductor refrigerator, cooling the cold end surface of the refrigerator 18, and ensuring that the ambient temperature of the APD chip 9 working remains constant.

[0082] Through the above technical scheme, the avalanche photodetector with integrated filter amplifier chip disclosed in the present invention has the advantages of small size and mass, simple circuit structure, low power consumption and stable detection efficiency. It integrates the LTCC chip with filter amplifier function into the detector, and the detector signal output pin directly outputs the avalanche signal after filtering and amplification; replaces multiple discrete circuits with LTCC chips, reduces the parasitic parameters of the signal link, reduces the channel crosstalk between discrete circuits, effectively reduces circuit noise, greatly reduces driving voltage, and reduces power consumption; through the design of temperature control circuit, during the operation of the detector, the cooling power of the refrigerator is adjusted according to the temperature change, so that the APD works in a stable low temperature environment, and the reverse bias voltage and gate signal size remain unchanged, thereby ensuring that the APD dark current noise is low and the sensitivity is high, so that the detector can maintain a stable detection efficiency.

[0083] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An avalanche photodetector with integrated filter amplifier chip, comprising an APD chip and a cooler, characterized in that: It also includes an avalanche signal processing chip, the output end of the APD chip is electrically connected to the signal input end of the avalanche signal processing chip, the output end of the avalanche signal processing chip outputs a processed avalanche signal, the APD chip is closely attached to the cold end surface of the refrigerator, the avalanche signal processing chip is used to suppress the gated signal and the second and higher harmonic signals in the original avalanche signal output by the APD chip, and filter and amplify the avalanche signal with low noise; the avalanche signal processing chip integrates the functions of the filter and the low-noise amplifier, and the APD chip, the refrigerator and the avalanche signal processing chip are integrally packaged in a shell.

2. The avalanche photodetector with integrated filter amplifier chip according to claim 1, characterized in that: It also includes an APD driver chip, the input end of the APD chip is electrically connected to the APD driver chip, and the APD driver chip is also packaged in the shell.

3. The avalanche photodetector with integrated filter amplifier chip according to claim 2, characterized in that: It also includes a ceramic substrate, the APD chip is arranged in the cooling area of ​​the ceramic substrate, the avalanche signal processing chip and the APD driving chip are arranged in the non-cooling area of ​​the ceramic substrate, and the ceramic substrate is also packaged in the shell.

4. The avalanche photodetector with integrated filter amplifier chip according to claim 3, characterized in that: It also includes a thermistor, which is arranged in the cooling area of ​​the ceramic substrate and close to the APD chip. The thermistor is also packaged in the shell.

5. The avalanche photodetector with integrated filter amplifier chip according to claim 4, characterized in that: It also includes a temperature control circuit, which includes a temperature acquisition ADC, a processor and a refrigerator driver. The temperature acquisition ADC is connected in parallel at both ends of the thermistor, and the refrigerator driver is connected to the refrigerator. One end of the processor is connected to the temperature acquisition ADC, and the other end is connected to the refrigerator driver. The temperature control circuit is arranged in the non-refrigeration area of ​​the ceramic substrate and is also encapsulated in the shell.

6. The avalanche photodetector with integrated filter amplifier chip according to claim 5, characterized in that: The refrigeration area and the non-refrigeration area of ​​the ceramic substrate are heat-insulated.

7. The avalanche photodetector with integrated filter amplifier chip according to claim 6, characterized in that: The refrigerator is only arranged in the cooling area of ​​the ceramic substrate.

8. The avalanche photodetector with integrated filter amplifier chip according to claim 7, characterized in that: The non-refrigeration area of ​​the ceramic substrate is temperature-controlled independently.

9. The avalanche photodetector with integrated filter amplifier chip according to any one of claims 1 to 8, characterized in that: The avalanche signal processing chip is a LTCC chip.

10. The avalanche photodetector with integrated filter amplifier chip according to claim 9, characterized in that: The LTCC chip includes a first filter, a second filter, a first low noise amplifier and a second low noise amplifier. The first filter, the first low noise amplifier, the second low noise amplifier and the second filter are connected in sequence by capacitor AC coupling. The input end of the first low noise amplifier is grounded through a first inductor and a first resistor connected in series, the input end of the second low noise amplifier is grounded through a second inductor and a second resistor connected in series, the output end of the first low noise amplifier is connected to a power supply voltage Vcc through a third inductor and a third resistor connected in series, and the output end of the second low noise amplifier is connected to a power supply voltage Vcc through a fourth inductor and a fourth resistor connected in series.

11. The avalanche photodetector with integrated filter amplifier chip according to claim 10, characterized in that: The LTCC chip also includes a first capacitor, a second capacitor, a third capacitor and a fourth capacitor, one end of the first capacitor is connected to the node between the first inductor and the first resistor, and the other end is grounded, one end of the second capacitor is connected to the node between the second inductor and the second resistor, and the other end is grounded, one end of the third capacitor is connected to the node between the third inductor and the third resistor, and the other end is grounded, one end of the fourth capacitor is connected to the node between the fourth inductor and the fourth resistor, and the other end is grounded.

12. A method for driving an avalanche photodetector according to any one of claims 1 to 11, characterized in that: The input signal drives the APD chip to work. At this time, if an optical signal reaches the photosensitive surface of the APD chip, an avalanche effect will occur in the APD chip, and the original avalanche signal generated will be output to the avalanche signal processing chip; the avalanche signal processing chip processes the original avalanche signal, filters the gate signal and the second and higher harmonic signal frequencies, and filters out the interference of the high-frequency gate signal; the avalanche signal processing chip filters and low-noise amplifies the avalanche signal caused by the optical signal, and then outputs it through the pin of the photodetector to realize the detection of the input optical signal.

13. The driving method of the avalanche photodetector according to claim 12, characterized in that: The avalanche photodetector also includes a thermistor. When the temperature of the APD chip changes, the resistance of the thermistor will change accordingly and be fed back to the processor through the temperature acquisition ADC. The processor controls the refrigerator drive according to the resistance feedback from the temperature acquisition ADC, and the refrigerator drive controls the cooling power of the refrigerator.

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