Narrow linewidth laser module

Abstract

The invention discloses a narrow-linewidth laser module, which belongs to the field of narrow-linewidth lasers, reduces the phase noise of the narrow-linewidth laser module from three aspects of a temperature control circuit, power supply fluctuation and heat dissipation, and can be better applied to the fields with high requirements on the phase noise, such as marine acoustic detection and modern naval antisubmarine combat. The device mainly comprises a lower shell and an upper shell, a circuit board is installed in the lower shell, a laser is arranged on the circuit board, the circuit board is installed on a plurality of heat dissipation tables of the lower shell through a heat conduction layer, laser installation grooves are formed in the lower shell and the upper shell, and the laser is fixedly installed in the laser installation grooves through the heat conduction layer. The circuit board comprises a temperature control circuit, the temperature control circuit comprises a load driving circuit and an instrument amplifier U1, the instrument amplifier U1 is connected with a digital-to-analog converter (DAC) through a Wheatstone bridge, and the load driving circuit is respectively connected with the instrument amplifier U1 and the TEC. The invention is mainly used for the narrow linewidth laser module.

Description

Technical Field

[0001] The present invention relates to the field of narrow line width lasers, and in particular to a narrow line width laser module. Background Art

[0002] Narrow linewidth laser modules are generally used in civilian fields such as laser radar and optical communications, and phase noise is not a concern; but when it is made into a fiber optic hydrophone for scientific research or military fields such as ocean acoustic detection and modern naval anti-submarine warfare, phase noise (especially low-frequency phase noise) is one of its most important indicators. The quality of the phase noise of a narrow linewidth laser module mainly depends on its internal temperature control circuit, power supply and heat dissipation.

[0003] Similar narrow linewidth laser products generally use mature TEC driver chips (such as MAX1978, ADN8835, LT8722, etc.) for temperature control. When designing these chips, they mainly focus on temperature control accuracy and energy conversion efficiency, and do not care about phase noise. Therefore, the phase noise of narrow linewidth laser modules made with these TEC driver chips is relatively large, such as a temperature control method and system for narrow linewidth lasers with publication number CN119070131A. In addition, factors such as power supply fluctuations interfering with the laser drive circuit and device heating will also cause the phase noise to deteriorate further, making it difficult for the module to meet the application requirements of marine acoustic detection, modern naval anti-submarine warfare and other application fields. Summary of the invention

[0004] The purpose of the present invention is to provide a narrow linewidth laser module, which reduces the phase noise of the narrow linewidth laser module from three aspects: temperature control circuit, power supply fluctuation and heat dissipation, so that it can be better applied to fields with high requirements on phase noise, such as marine acoustic detection and modern naval anti-submarine warfare.

[0005] The present invention is achieved through the following technical solutions:

[0006] A narrow line width laser module comprises a lower shell and an upper shell, wherein a circuit board is installed in the lower shell, a laser and a connector are arranged on the circuit board, the circuit board is installed on a plurality of heat sinks of the lower shell through a heat conductive layer, the lower shell and the upper shell are both provided with laser mounting grooves, the laser is fixedly installed in the laser mounting grooves through the heat conductive layer, the circuit board comprises a temperature control circuit, the temperature control circuit comprises a load drive circuit and an instrument amplifier U1, the instrument amplifier U1 is connected to a digital-to-analog converter DAC through a Wheatstone bridge, and the load drive circuit is respectively connected to the instrument amplifier U1 and TEC; the laser is a narrow line width laser, and the four surfaces of the laser are all heat dissipation surfaces, so that the laser reaches thermal equilibrium faster and has better shock resistance.

[0007] Furthermore, the Wheatstone bridge includes a fixed resistor R2, a fixed resistor R3, a fixed resistor R4 and a thermistor RT, the digital-to-analog converter DAC is connected between the fixed resistor R2 and the fixed resistor R4 through a current limiting resistor R1, the current limiting resistor R1 is also connected to the negative input terminal of the instrument amplifier U1, the positive input terminal of the instrument amplifier U1 is connected between the fixed resistor R3 and the thermistor RT, and the output terminal of the instrument amplifier U1 is connected to the load driving circuit.

[0008] Furthermore, the load driving circuit includes a PID circuit and an inverting amplifier circuit, the output end of the instrumentation amplifier U1 is connected to the PID circuit, the output end of the PID circuit is connected to the input end of the inverting amplifier circuit, the output end of the PID circuit is connected to the positive pole of the TEC, and the output end of the inverting amplifier circuit is connected to the negative pole of the TEC.

[0009] Furthermore, the load driving circuit includes a PID circuit and an inverting amplifier circuit, the output end of the instrumentation amplifier U1 is connected to the PID circuit, the output end of the PID circuit is connected to the input end of the inverting amplifier circuit, the output end of the PID circuit is connected to the positive pole of the TEC through a plurality of emitter followers and a ballast resistor, and the output end of the inverting amplifier circuit is connected to the negative pole of the TEC through a plurality of emitter follower circuits.

[0010] Furthermore, the PID circuit includes an operational amplifier U2, the negative input terminal of the operational amplifier U2 is connected to a resistor R10, the resistor R10 is connected in parallel with a capacitor C1, a resistor R9 and a capacitor C2 are also connected between the negative input terminal of the operational amplifier U2 and the output terminal of the operational amplifier U2, the output terminal of the instrumentation amplifier U1 is connected to the resistor R10, the output terminal of the operational amplifier U2 is also connected to a ballast resistor R5, and the ballast resistor R5 is connected to the positive pole of the TEC; the reverse amplifier circuit includes an operational amplifier U3, the output terminal of the operational amplifier U2 is connected to the negative input terminal of the operational amplifier U3 through a resistor R12, a resistor R11 is connected between the negative input terminal of the operational amplifier U3 and the output terminal of the operational amplifier U3, the output terminal of the operational amplifier U3 is connected to a ballast resistor R7, and the ballast resistor R7 is connected to the negative pole of the TEC.

[0011] Furthermore, the PID circuit includes an operational amplifier U2, the negative input terminal of the operational amplifier U2 is connected to a resistor R10, the resistor R10 is connected in parallel with a capacitor C1, a resistor R9 and a capacitor C2 are also connected between the negative input terminal of the operational amplifier U2 and the output terminal of the operational amplifier U2, the output terminal of the instrumentation amplifier U1 is connected to the resistor R10, the output terminal of the operational amplifier U2 is connected to the input terminal of a plurality of emitter follower circuits I, the output terminal of the operational amplifier U2 is also connected to a ballast resistor R5, and the ballast resistor R5 and the output terminal of the emitter follower circuit I are both connected to the positive electrode of the TEC; the reverse amplifier circuit includes an operational amplifier U3, the output terminal of the operational amplifier U2 is connected to the negative input terminal of the operational amplifier U3 through a resistor R12, a resistor R11 is connected between the negative input terminal of the operational amplifier U3 and the output terminal of the operational amplifier U3, the output terminal of the operational amplifier U3 is connected to a ballast resistor R7, the output terminal of the operational amplifier U3 is connected to the input terminal of a plurality of emitter follower circuits II, and the ballast resistor R7 and the output terminal of the emitter follower circuit II are both connected to the negative electrode of the TEC.

[0012] Furthermore, the emitter follower circuit I includes an emitter follower I and a ballast resistor R6, the output end of the operational amplifier U2 is connected to the positive input end of the emitter follower I, the output end of the emitter follower I is connected to the ballast resistor R6, and the ballast resistor R6 is connected to the positive electrode of the TEC; the emitter follower circuit II includes an emitter follower II and a ballast resistor R8, the output end of the operational amplifier U3 is connected to the positive input end of the emitter follower II, the output end of the emitter follower II is connected to the ballast resistor R8, and the ballast resistor R8 is connected to the negative electrode of the TEC.

[0013] Furthermore, it also includes a laser driving circuit, which includes a transistor Q1 and a rectifier and filter circuit. The laser is connected to the collector of the transistor Q1 through the rectifier and filter circuit. The base of the transistor Q1 is connected to the output end of the operational amplifier U21 through the resistor R22. The positive input end of the operational amplifier U21 is connected to the current control signal. The negative input end of the operational amplifier U21 is connected to the sampling resistor R23. The emitter of the transistor Q1 is connected to the sampling resistor R23.

[0014] Furthermore, the rectifier filter circuit includes a switching diode D1 and an inductor L1, the laser is respectively connected in parallel with the switching diode D1 and the capacitor C22, one end of the laser is connected to the inductor L1, and the other end of the laser is connected to an RC filter circuit composed of a resistor R21 and a capacitor C21, and the inductor L1 and the RC filter circuit are both connected to the collector of the transistor Q1.

[0015] Furthermore, the heat-conducting layer is a thermally conductive silicone pad and / or thermally conductive silicone grease, the back of the operational amplifier in the temperature control circuit of the circuit board is a forbidden area, and the bottom of the forbidden area is placed on a heat sink through a thermally conductive silicone pad and / or thermally conductive silicone grease to conduct away the heat generated when the operational amplifier is working and reduce the thermal noise of the operational amplifier. The surface of the operational amplifier is coated with three-proof glue for protection, and the forbidden area is not coated with three-proof glue to protect the circuit from damage under vibration, humidity, salt spray and high temperature.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1. A low-noise temperature control circuit based on an operational amplifier (especially phase noise in the low frequency band) is provided, which solves the problem of large phase noise of commonly used TEC driver chips; in view of the defect of insufficient driving capability of the operational amplifier, double or even multiple driving capabilities can be obtained by adding RF followers.

[0018] 2. The rectifier and filter circuits are used to suppress the interference of power supply fluctuations on the laser drive circuit.

[0019] 3. The circuit board is installed on the heat sink through the heat conductive layer. Without affecting the coating of the three-proof adhesive on the components, the heat generated by the operational amplifier during operation is conducted away, thereby reducing the thermal noise of the operational amplifier.

[0020] 4. The laser is installed in the laser mounting slot. Its heat dissipation and fixing method enable the laser to reach thermal equilibrium faster and have better shock resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the structure of the present invention;

[0022] Figure 2 It is a schematic diagram of the structure of the present invention;

[0023] Figure 3 Schematic diagram of the circuit principle of embodiment 2 of the present invention;

[0024] Figure 4 It is a schematic diagram of the circuit principle of a group of emitter follower circuits in Embodiment 3 of the present invention;

[0025] Figure 5 It is a detailed circuit principle diagram of a group of emitter follower circuits in Embodiment 3 of the present invention;

[0026] Figure 6 It is a schematic diagram of the circuit principle of connecting two groups of emitter follower circuits in embodiment 3 of the present invention;

[0027] Figure 7 It is a circuit principle diagram of the laser driving circuit of the present invention.

[0028] In the figure: 1. upper housing; 2. circuit board; 3. laser; 4. connector; 5. laser mounting slot; 6. heat sink; 7. lower housing. DETAILED DESCRIPTION

[0029] The present invention will be further described below in conjunction with the accompanying drawings.

[0030] Example 1

[0031] like Figure 1 – Figure 2 As shown, a narrow line width laser module includes a lower shell 7 and an upper shell 1, wherein a circuit board 2 is installed in the lower shell 7, and a laser 3 and a connector 4 (existing technology) are arranged on the circuit board 2, and the circuit board 2 is installed on a plurality of heat sinks 6 of the lower shell 7 through a heat conductive layer, and a laser mounting groove 5 is provided on both the lower shell 7 and the upper shell 1, and the laser 3 is fixedly installed in the laser mounting groove 5 through a heat conductive layer, and the circuit board 2 includes a temperature control circuit, and the temperature control circuit includes a load drive circuit and an instrument amplifier U1, and the instrument amplifier U1 is connected to a digital-to-analog converter DAC through a Wheatstone bridge, and the load drive circuit is respectively connected to the instrument amplifier U1 and TEC; the laser 3 is a narrow line width laser, and the four surfaces of the laser 3 are heat dissipation surfaces, so that the laser reaches thermal equilibrium faster and has better shock resistance; the Wheatstone bridge includes fixed resistors R2, R3, and R4 and thermistor RT, the digital-to-analog converter DAC is connected between the fixed resistor R2 and the fixed resistor R4 through the current limiting resistor R1, the current limiting resistor R1 is also connected to the negative input end of the instrument amplifier U1, the positive input end of the instrument amplifier U1 is connected between the fixed resistor R3 and the thermistor RT, and the output end of the instrument amplifier U1 is connected to the load driving circuit; the thermal conductive layer is a thermal conductive silicone pad and / or thermal conductive silicone grease, the back of the operational amplifier in the temperature control circuit of the circuit board 2 is a forbidden area (the forbidden area refers to the area where no components are placed), and the forbidden area is placed on the heat sink 6 through the thermal conductive silicone pad and / or thermal conductive silicone grease to conduct the heat generated when the operational amplifier is working and reduce the thermal noise of the operational amplifier. The surface of the operational amplifier and other components is coated with three-proof glue for protection, and the forbidden area is not coated with three-proof glue to protect the circuit from damage under vibration, humidity, salt spray, high temperature and the like.

[0032] Example 2

[0033] like Figure 3As shown, a narrow line width laser module, the load driving circuit includes a PID circuit and a reverse amplifier circuit, the output end of the instrument amplifier U1 is connected to the PID circuit, the output end of the PID circuit is connected to the input end of the reverse amplifier circuit, the output end of the PID circuit is connected to the positive electrode of the TEC, the output end of the reverse amplifier circuit is connected to the negative electrode of the TEC, the PID circuit includes an operational amplifier U2, the negative input end of the operational amplifier U2 is connected to a resistor R10, the resistor R10 is connected in parallel with a capacitor C1, and the negative input end of the operational amplifier U2 and the output end of the operational amplifier U2 are also connected The output end of the instrumentation amplifier U1 is connected to the resistor R10, and the output end of the operational amplifier U2 is also connected to the ballast resistor R5, which is connected to the positive electrode of the TEC; the reverse amplifier circuit includes an operational amplifier U3, the output end of the operational amplifier U2 is connected to the negative input end of the operational amplifier U3 through the resistor R12, a resistor R11 is connected between the negative input end of the operational amplifier U3 and the output end of the operational amplifier U3, and the output end of the operational amplifier U3 is connected to the ballast resistor R7, which is connected to the negative electrode of the TEC, and the rest is the same as in Example 1. In practical applications, if the required driving current is less than the maximum output current of an operational amplifier, the emitter follower can be removed (and the ballast resistors R5-R8 can be removed at the same time).

[0034] Example 3

[0035] like Figure 4 – Figure 6As shown, a narrow linewidth laser module, the load driving circuit includes a PID circuit and a reverse amplifier circuit, the output end of the instrument amplifier U1 is connected to the PID circuit, the output end of the PID circuit is connected to the input end of the reverse amplifier circuit, the output end of the PID circuit is connected to the positive electrode of the TEC through a plurality of emitter followers and ballast resistors, and the output end of the reverse amplifier circuit is connected to the negative electrode of the TEC through a plurality of emitter follower circuits; the PID circuit includes an operational amplifier U2, the negative input end of the operational amplifier U2 is connected to a resistor R10, the resistor R10 is connected in parallel with a capacitor C1, a resistor R9 and a capacitor C2 are further connected between the negative input end of the operational amplifier U2 and the output end of the operational amplifier U2, the output end of the instrument amplifier U1 is connected to the resistor R10, the output end of the operational amplifier U2 is connected to the input ends of a plurality of emitter follower circuits Ⅰ, the output end of the operational amplifier U2 is also connected to a ballast resistor R5, and the ballast resistor R5 and the output end of the emitter follower circuit Ⅰ are both connected to the positive electrode of the TEC; the reverse amplifier The emitter follower circuit includes an operational amplifier U3, the output end of the operational amplifier U2 is connected to the negative input end of the operational amplifier U3 through a resistor R12, a resistor R11 is connected between the negative input end of the operational amplifier U3 and the output end of the operational amplifier U3, the output end of the operational amplifier U3 is connected to a ballast resistor R7, the output end of the operational amplifier U3 is connected to the input end of a plurality of emitter follower circuits II, the ballast resistor R7 and the output end of the emitter follower circuit II are both connected to the negative electrode of the TEC; the emitter follower circuit I includes an emitter follower I and a ballast resistor R6, the output end of the operational amplifier U2 is connected to the positive input end of the emitter follower I, the output end of the emitter follower I is connected to the ballast resistor R6, and the ballast resistor R6 is connected to the positive electrode of the TEC; the emitter follower circuit II includes an emitter follower II and a ballast resistor R8, the output end of the operational amplifier U3 is connected to the positive input end of the emitter follower II, the output end of the emitter follower II is connected to the ballast resistor R8, and the ballast resistor R8 is connected to the negative electrode of the TEC; the rest is the same as in Example 1. Figure 4 and Figure 5 The structure shown is that the output end of the operational amplifier U2 is connected to a group of emitter follower circuits I, and the output end of the operational amplifier U3 is connected to a group of emitter follower circuits II. If the required driving current is very large, Figure 6 The circuit shown is for connecting two groups of emitter followers (adding a ballast resistor at the output end of each emitter follower). At this time, the driving capability can be three times that without emitter followers; the same is true for connecting three or more groups.

[0036] Example 4

[0037] like Figure 7As shown, a narrow linewidth laser module also includes a laser driving circuit, the laser driving circuit includes a transistor Q1 and a rectifier filter circuit, the laser 3 is connected to the collector of the transistor Q1 through the rectifier filter circuit, the base of the transistor Q1 is connected to the output end of the operational amplifier U21 through the resistor R22, the positive input end of the operational amplifier U21 is connected to the current control signal, the negative input end of the operational amplifier U21 is connected to the sampling resistor R23, and the emitter of the transistor Q1 is connected to the sampling resistor R23; the rectifier filter circuit includes a switching diode D1 and an inductor L1, the laser 3 is respectively connected in parallel with the switching diode D1 and the capacitor C22, one end of the laser 3 is connected to the inductor L1, and the other end of the laser 3 is connected to the RC filter circuit composed of the resistor R21 and the capacitor C21, the inductor L1 and the RC filter circuit are both connected to the collector of the transistor Q1, and the rest is the same as Example 1. The switching diode D1 and the capacitor C22 are used to prevent sudden voltage pulses from damaging the laser 3. The inductor L1 makes the current flowing through the laser 3 more stable. The RC filter circuit composed of the resistor R21 and the capacitor C21 can be used to remove interference signals of fixed frequency.

[0038] Working principle (with Figure 5 For example):

[0039] 1) The digital-to-analog converter DAC outputs a temperature control voltage V1, which corresponds to the target temperature.

[0040] 2) The thermistor RT is located inside the laser. The value of the thermistor RT corresponds to the current temperature, and Vcc is the power supply. A pair of voltages V2 and V3 are obtained using a Wheatstone bridge. According to Kirchhoff's theorem, V2 = Vcc*RT / (R3+RT), V3 = (V1*R2*R4+Vcc*R1*R4) / (R1*R2+R2*R4+R1*R4). Since the power supply Vcc and the resistors R1-R4 are fixed values, the voltage V2 can be calculated from the thermistor RT, which reflects the current temperature. The voltage V3 can be calculated from the voltage V1, which reflects the target temperature. If the current temperature is higher than the target temperature, V2 < V3; if the current temperature is equal to the target temperature, V2 = V3; if the current temperature is lower than the target temperature, V2 > V3.

[0041] 3) Input voltage V2 and voltage V3 into the positive input and negative input of the instrument amplifier respectively, and give the instrument amplifier a reference voltage Vref, and obtain the output voltage V4 = V2-V3+Vref. Obviously, voltage V4 reflects the difference between the current temperature and the target temperature. The reference voltage Vref is introduced here to give voltage V4 a positive bias voltage so that the value of voltage V4 is always positive.

[0042] 4) Input the voltage V4 into the PID circuit to obtain the output voltage V5. The PID circuit is a proportional-integral-differential control circuit, which improves the stability and reliability of temperature control. The capacitors C1 and C2 are known capacitors, and the resistors R9 and R10 are known resistors, so it can be calculated: And because V4=V2-V3+Vref,

[0043] 5) After the voltage V5 passes through the reverse amplifier, the voltage V6 is obtained, where the resistors R11 and R12 are known resistors. Since the PID circuit and the reverse amplifier circuit have a common reference voltage Vref, V6 can be calculated as (Vref-V5)*R11 / R12+Vref.

[0044] 6) The emitter follower circuit I is connected below the PID circuit, and the emitter follower circuit II is connected below the reverse amplifier to make up for the shortcomings of the operational amplifier, such as small output current and insufficient driving ability. These two emitter followers are also made of operational amplifiers, such as Figure 5 Operational amplifier U4 and operational amplifier U5 in. Adding an emitter follower at each end can obtain about twice the driving capacity without an emitter follower. The resistance values ​​of ballast resistors R5-R8 are equal, which is about 10% of the equivalent resistance value of TEC. For the convenience of calculation, the equivalent resistance value of TEC is set to Rt, then R5=R6=R7=R8=10%*Rt. Resistors R5 and R6 play the role of balancing the output voltage of PID and emitter follower I, and resistors R7 and R8 play the role of balancing the output voltage of the reverse operational amplifier U3 and emitter follower II. The output voltage of the emitter follower is equal to the input voltage, so the output voltage of emitter follower I is V5, and the output voltage of emitter follower II is V6. At this time, the driving current of the entire temperature control circuit can be calculated as It=(V5-V6) / (1.1*Rt).

[0045] 7) When It>0, TEC cools the laser; when It<0, TEC heats the laser. The larger the absolute value of It, the greater the heating / cooling power. The driving capability of the entire load driving circuit mainly depends on the maximum output current of operational amplifier U2-operational amplifier U5. The cooling driving capability (i.e., the maximum positive current flowing through TEC) is equal to the sum of the maximum output currents of operational amplifier U2 and operational amplifier U4, and the heating driving capability (i.e., the maximum negative current flowing through TEC) is equal to the sum of the maximum output currents of operational amplifier U3 and operational amplifier U5.

Claims

1. A narrow linewidth laser module, comprising a lower housing (7) and an upper housing (1), characterized in that: A circuit board (2) is installed in the lower shell (7), a laser (3) is arranged on the circuit board (2), the circuit board (2) is installed on a plurality of heat sinks (6) of the lower shell (7) via a heat conductive layer, a laser installation groove (5) is provided on both the lower shell (7) and the upper shell (1), the laser (3) is fixedly installed in the laser installation groove (5) via the heat conductive layer, the circuit board (2) comprises a temperature control circuit, the temperature control circuit comprises a load drive circuit and an instrument amplifier U1, the instrument amplifier U1 is connected to a digital-to-analog converter DAC via a Wheatstone bridge, and the load drive circuit is respectively connected to the instrument amplifier U1 and the TEC; the laser (3) is a narrow line width laser.

2. The narrow linewidth laser module according to claim 1, characterized in that: The Wheatstone bridge includes a fixed resistor R2, a fixed resistor R3, a fixed resistor R4 and a thermistor RT. The digital-to-analog converter DAC is connected between the fixed resistor R2 and the fixed resistor R4 through a current limiting resistor R1. The current limiting resistor R1 is also connected to the negative input terminal of the instrument amplifier U1. The positive input terminal of the instrument amplifier U1 is connected between the fixed resistor R3 and the thermistor RT. The output terminal of the instrument amplifier U1 is connected to the load driving circuit.

3. The narrow linewidth laser module according to claim 2, characterized in that: The load driving circuit includes a PID circuit and an inverting amplifier circuit. The output end of the instrument amplifier U1 is connected to the PID circuit, the output end of the PID circuit is connected to the input end of the inverting amplifier circuit, the output end of the PID circuit is connected to the positive pole of the TEC, and the output end of the inverting amplifier circuit is connected to the negative pole of the TEC.

4. The narrow linewidth laser module according to claim 2, characterized in that: The load driving circuit includes a PID circuit and an inverting amplifier circuit. The output end of the instrument amplifier U1 is connected to the PID circuit, the output end of the PID circuit is connected to the input end of the inverting amplifier circuit, the output end of the PID circuit is connected to the positive electrode of the TEC through a plurality of emitter followers and a ballast resistor, and the output end of the inverting amplifier circuit is connected to the negative electrode of the TEC through a plurality of emitter follower circuits.

5. The narrow linewidth laser module according to claim 3, characterized in that: The PID circuit includes an operational amplifier U2, the negative input terminal of the operational amplifier U2 is connected to a resistor R10, the resistor R10 is connected in parallel with a capacitor C1, a resistor R9 and a capacitor C2 are also connected between the negative input terminal of the operational amplifier U2 and the output terminal of the operational amplifier U2, the output terminal of the instrumentation amplifier U1 is connected to the resistor R10, the output terminal of the operational amplifier U2 is also connected to a ballast resistor R5, and the ballast resistor R5 is connected to the positive pole of the TEC; the reverse amplifier circuit includes an operational amplifier U3, the output terminal of the operational amplifier U2 is connected to the negative input terminal of the operational amplifier U3 through a resistor R12, a resistor R11 is connected between the negative input terminal of the operational amplifier U3 and the output terminal of the operational amplifier U3, the output terminal of the operational amplifier U3 is connected to a ballast resistor R7, and the ballast resistor R7 is connected to the negative pole of the TEC.

6. The narrow linewidth laser module according to claim 4, characterized in that: The PID circuit includes an operational amplifier U2, the negative input end of the operational amplifier U2 is connected to a resistor R10, the resistor R10 is connected in parallel with a capacitor C1, a resistor R9 and a capacitor C2 are also connected between the negative input end of the operational amplifier U2 and the output end of the operational amplifier U2, the output end of the instrumentation amplifier U1 is connected to the resistor R10, the output end of the operational amplifier U2 is connected to the input end of a plurality of emitter follower circuits I, the output end of the operational amplifier U2 is also connected to a ballast resistor R5, the ballast resistor R5 and the output end of the emitter follower circuit I are both connected to the positive electrode of the TEC; the reverse amplifier circuit includes an operational amplifier U3, the output end of the operational amplifier U2 is connected to the negative input end of the operational amplifier U3 through a resistor R12, a resistor R11 is connected between the negative input end of the operational amplifier U3 and the output end of the operational amplifier U3, the output end of the operational amplifier U3 is connected to a ballast resistor R7, the output end of the operational amplifier U3 is connected to the input end of a plurality of emitter follower circuits II, the ballast resistor R7 and the output end of the emitter follower circuit II are both connected to the negative electrode of the TEC.

7. The narrow linewidth laser module according to claim 6, characterized in that: The emitter follower circuit I includes an emitter follower I and a ballast resistor R6, the output end of the operational amplifier U2 is connected to the positive input end of the emitter follower I, the output end of the emitter follower I is connected to the ballast resistor R6, and the ballast resistor R6 is connected to the positive electrode of the TEC; the emitter follower circuit II includes an emitter follower II and a ballast resistor R8, the output end of the operational amplifier U3 is connected to the positive input end of the emitter follower II, the output end of the emitter follower II is connected to the ballast resistor R8, and the ballast resistor R8 is connected to the negative electrode of the TEC.

8. The narrow linewidth laser module according to claim 1, characterized in that: The laser driving circuit also includes a transistor Q1 and a rectifier filter circuit. The laser (3) is connected to the collector of the transistor Q1 through the rectifier filter circuit. The base of the transistor Q1 is connected to the output end of the operational amplifier U21 through a resistor R22. The positive input end of the operational amplifier U21 is connected to a current control signal. The negative input end of the operational amplifier U21 is connected to a sampling resistor R23. The emitter of the transistor Q1 is connected to the sampling resistor R23.

9. The narrow linewidth laser module according to claim 8, characterized in that: The rectifier filter circuit comprises a switching diode D1 and an inductor L1. The laser (3) is respectively connected in parallel with the switching diode D1 and the capacitor C22. One end of the laser (3) is connected to the inductor L1. The other end of the laser (3) is connected to an RC filter circuit composed of a resistor R21 and a capacitor C21. The inductor L1 and the RC filter circuit are both connected to the collector of the transistor Q1.

10. The narrow linewidth laser module according to claim 1, characterized in that: The heat-conducting layer is a heat-conducting silicone pad and / or heat-conducting silicone grease. The back of the operational amplifier in the temperature control circuit of the circuit board (2) is a no-clothing area. The bottom of the no-clothing area is placed on a heat sink (6) through a heat-conducting silicone pad and / or heat-conducting silicone grease to conduct away the heat generated when the operational amplifier is working and reduce the thermal noise of the operational amplifier. The surface of the operational amplifier is coated with three-proof glue for protection.

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