Integrated miniature VCSEL laser packaging structure based on non-magnetic material

Abstract

The invention discloses an integrated miniature VCSEL laser packaging structure based on a non-magnetic material. The integrated miniature VCSEL laser packaging structure comprises a frame, a VCSEL chip, a temperature control unit and an integrated flexible circuit, the frame is composed of a quarter-wave plate, a PEEK frame and an aluminum nitride substrate. The temperature control unit comprises an NTC thermistor, an upper layer 2N polar distance heating coil and a lower layer 2N polar distance heating coil, and the temperature control unit and the internal electrode are connected to an external circuit. The main body of the integrated flexible circuit part is an FPC flexible circuit, one side of the FPC flexible circuit close to the laser is provided with an inner side electrode which can be connected with other elements of the miniaturized atom magnetometer, and one side of the FPC flexible circuit far away from the laser is provided with an outer side electrode which can be connected with an external circuit. According to the invention, the PEEK material and the aluminum nitride are used as the frame, and the 2N polar distance heating coil is used for heating the VCSEL chip, so that the low-frequency magnetic field interference caused by packaging and heating is reduced. Meanwhile, a quarter-wave plate is installed, laser is shaped, circularly polarized light needed by the atom magnetometer is obtained, the height of the laser is controlled to be 2.5 mm, and miniaturization is better facilitated.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor laser packaging, and particularly relates to an integrated micro VCSEL laser packaging structure based on non-magnetic materials. Background Art

[0002] Semiconductor lasers have the characteristics of small volume, light weight, low power consumption, high reliability, long life, etc. compared with solid, gas, liquid lasers, etc. Semiconductor lasers are divided into edge-emitting lasers (EEL) and vertical-cavity surface-emitting lasers (VCSEL) according to different laser chip structures. VCSEL lasers emit laser light from the surface perpendicular to the substrate, and it is easier to achieve an array effect compared with edge-emitting lasers. At the same time, it has the advantages of small volume, circular output light spot, single-mode output, small threshold current, etc., and is widely used in the fields of optical communication, optical interconnection, etc. In the field of quantum sensing, VCSEL lasers are also the key components to realize the miniaturization of its sensors. Miniature atomic magnetometers are widely used in magnetoencephalography measurement, basic physics research, geomagnetic exploration, etc. due to their high sensitivity and high spatial resolution. However, due to the sensitivity of atomic magnetometers to magnetic field signals, an extremely weak ambient magnetic field is required, usually less than a few nanoteslas (nT). Therefore, it is necessary to minimize the magnetic noise brought by the light source packaging.

[0003] In the existing VCSEL packaging structure, such as transistor outline (TO) packaging, kovar alloy is usually used to make the shell, and ordinary glass lenses are installed on the shell by limiting or gluing. At the same time, the VCSEL chip and the thermoelectric cooler (TEC) are fixed on the copper substrate by wire bonding and led out by the pins below. This packaging structure has three problems: First, the kovar alloy shell has a large magnetism, which will reduce the response signal intensity of the magnetometer and is not conducive to improving the sensitivity of the magnetometer. Using a TEC to control its current for heating or cooling, this DC heating method will generate a large low-frequency magnetic field, affecting the measurement results and sensitivity of the atomic magnetometer. After measurement, the magnetic field of the VCSEL laser packaged by TO is still 40.83 nT at a distance of 4 cm, seriously affecting the measurement results of the atomic magnetometer. Second, the atomic magnetometer needs circularly polarized light to pump the atomic gas chamber. Therefore, a quarter-wave plate needs to be set to adjust the laser into circularly polarized light. However, the ordinary glass lens of TO packaging has no shaping effect and needs further shaping, which is not conducive to the miniaturization of the atomic magnetometer. Third, the size and integration of this structure are insufficient. The existing TO packaging often has a diameter of 8 mm and a height of 5 mm, and the pin length reaches 12 mm, which is not suitable for miniaturized and integrated atomic magnetometers. At the same time, as the bottom component of the magnetometer, the VCSEL laser needs to integrate the circuit interface of the upper component more, and the pins are not conducive to multi-interface coupling. To better adapt to miniaturized and integrated atomic magnetometers, it is necessary to design a micro VCSEL laser packaging structure made of non-magnetic materials. Summary of the Invention

[0004] The object of the present invention is to provide an integrated micro VCSEL laser packaging structure based on non-magnetic materials. This device uses non-magnetic polyether ether ketone (PEEK) and aluminum nitride materials to eliminate the influence of the housing material on the magnetic field. The laser heating device uses a double-layer heating coil instead of a thermoelectric cooler TEC to reduce the magnetic field generated by heating. A quarter-wave plate is integrated at the laser exit position to modulate the laser into circularly polarized light, improving the pumping effect of the atomic magnetometer. An FPC flexible circuit is integrated at the bottom of the laser, and electrode interfaces are provided on the inner side to facilitate connection with other components of the atomic magnetometer. After measurement, the magnetic field of the integrated micro VCSEL laser with overall non-magnetic packaging is only 0.3 nT at a distance of 4 cm, which is much smaller than 40.83 nT of the TO-packaged VCSEL laser, greatly reducing the influence of the laser magnetic field on the atomic magnetometer.

[0005] The technical solution of the present invention is as follows:

[0006] An integrated micro VCSEL laser packaging structure based on non-magnetic materials, characterized in that it includes a frame. The frame has a cavity surrounded by side walls on all sides. The frame is made of PEEK material. An aluminum nitride substrate is arranged in the cavity. An upper-layer 2 N pole-distance heating coil, where N is a positive integer. A lower-layer 2 N pole-distance heating coil is arranged on the lower surface of the aluminum nitride substrate. The center of the upper-layer 2 N pole-distance heating coil is provided with a VCSEL chip, an NTC thermistor, and an internal electrode. A quarter-wave plate fixed by a step structure in the cavity is arranged directly above the VCSEL chip. A lower-layer 2 N pole-distance heating coil is arranged below the FPC flexible circuit board. The FPC flexible circuit board has an inner electrode and an outer electrode for connecting to an external circuit.

[0007] The FPC flexible circuit board is respectively connected to the upper and lower-layer 2 N pole-distance heating coils, an atomic cell heating unit, a VCSEL chip, a PT1000 platinum resistor, an NTC negative feedback thermistor, a PD signal sensor, and an external control circuit. The VCSEL chip is respectively connected to the upper and lower-layer 2 N pole-distance heating coils, an NTC negative feedback thermistor, and a quarter-wave plate. The atomic cell is respectively connected to the atomic cell heating unit, a PD signal sensor, a PT1000 platinum resistor, and a quarter-wave plate.

[0008] The external control circuit controls the upper and lower-layer 2 NThe pole pitch of the heating coil is adjusted to stabilize the temperature near the VCSEL chip to the optimal temperature. The external control circuit powers the VCSEL chip through an FPC flexible circuit board. The external control circuit controls the atom cell heating unit to heat the atom cell in a PID control manner through the FPC flexible circuit board. The PT1000 platinum resistor feeds back the temperature of the atom cell to the FPC flexible circuit board. The PD signal sensor transmits the magnetic field measurement signal collected from the atom cell to the FPC flexible circuit board. The NTC negative feedback thermistor feeds back the temperature measured from the VCSEL chip to the FPC flexible circuit board. The quarter-wave plate pumps the laser from the VCSEL chip into the atom cell.

[0009] The outer electrode includes 12 ports. The port 1 corresponds to Laser Heat-, which is the negative electrode of the laser heating. The port 2 corresponds to Laser Heat+, which is the positive electrode of the laser heating. The port 3 corresponds to Cell Heat+, which is the positive electrode of the cell heating. The port 4 corresponds to Cell Heat-, which is the negative electrode of the cell heating. The port 5 corresponds to Laser-, which is the negative electrode of the laser power supply. The port 6 corresponds to Laser+, which is the positive electrode of the laser power supply. The port 7 corresponds to Ntc+, which is the positive electrode of the thermistor. The port 8 corresponds to Ntc-, which is the negative electrode of the thermistor. The port 9 corresponds to PT1000+, which is the positive electrode of the platinum resistor. The port 10 corresponds to PT1000-, which is the negative electrode of the platinum resistor. The port 11 corresponds to PD-, which is the negative electrode of the photodiode. The port 12 corresponds to PD+, which is the positive electrode of the photodiode.

[0010] The inner electrode is located on the side close to the laser, and the outer electrode is located on the side far from the laser.

[0011] The magnetic field of the integrally miniaturized VCSEL laser with overall non-magnetic encapsulation is only 0.3 nT at a distance of 4 cm.

[0012] The technical effects of the present invention are as follows: For the integrated miniaturized VCSEL laser packaging structure based on non-magnetic materials of the present invention, through measurement, the magnetic field of the integrally miniaturized VCSEL laser with overall non-magnetic encapsulation is only 0.3 nT at a distance of 4 cm, which is much smaller than the magnetic field of the TO-packaged VCSEL laser. Thus, a non-magnetic, miniaturized, and integrated VCSEL laser packaging is achieved.

[0013] The advantages of the present invention compared with the prior art are as follows:

[0014] (1) The present invention adopts non-magnetic structural materials, including PEEK and aluminum nitride. Compared with the kovar alloy shell used in the existing TO packaging, the magnetism is greatly reduced. At the same time, a 2N pole pitch heating coil is used to replace the TEC in the existing packaging to heat the VCSEL chip, improving the measurement sensitivity of the miniaturized atomic magnetometer.

[0015] (2) Considering the miniaturization requirements of the atomic magnetometer, the present invention integrates a quarter-wave plate onto the laser frame. After the laser emits light, the required pumping beam is obtained, thereby improving the pumping effect of the atomic magnetometer.

[0016] (3) Considering the integration requirements of the miniaturized atomic magnetometer, an FPC flexible circuit is placed at the bottom of the laser, and the inner electrodes are integrated and connected to other components, realizing the unified output and control of the atomic magnetometer. Description of the Drawings

[0017] Figure 1 is a schematic structural diagram of an integrated micro VCSEL laser packaging structure based on a non-magnetic material for implementing the present invention.

[0018] Figure 2 is a schematic working principle diagram of an integrated micro VCSEL laser packaging structure based on a non-magnetic material of the present invention. Figure 2 includes the upper and lower layer 2 N pole pitch heating coils (N is a positive integer), an atomic cell heating unit, a VCSEL chip (VCSEL, vertical cavity surface emitting laser), a PT1000 platinum resistance (PT1000, specification model), an NTC negative feedback thermistor (NTC - Negative Temperature Coefficient thermistor), a PD signal sensor (PD, photodiode), and an FPC flexible circuit of an external control circuit. The VCSEL chip is respectively connected to the upper and lower layer 2 N pole pitch heating coils, an NTC negative feedback thermistor, and a wave plate. The atomic cell is respectively connected to the atomic cell heating unit, a PD signal sensor, a PT1000 platinum resistance, and a wave plate. The external control circuit controls the upper and lower layer 2 N pole pitch heating coils in a PID control manner (PID, proportional integral derivative control algorithm) through the FPC flexible circuit to stabilize the temperature near the VCSEL chip to the optimal temperature. The external control circuit powers the VCSEL chip through the FPC flexible circuit. The external control circuit controls the atomic cell heating unit to heat the atomic cell in a PID control manner through the FPC flexible circuit, and the PT1000 platinum resistance feeds back the temperature of the atomic cell to the FPC flexible circuit. The PD signal sensor transmits the magnetic field measurement signal collected from the atomic cell to the FPC flexible circuit. The NTC negative feedback thermistor feeds back the temperature measured from the VCSEL chip to the FPC flexible circuit. The wave plate pumps the laser from the VCSEL chip into the atomic cell.

[0019] Figure 3 is Figure 1 a schematic diagram of the function definition of the outer electrode interface of the FPC flexible circuit inFigure 3 The LaserHeat corresponding to the middle port 1, i.e., the negative electrode of the laser heating; the Laser Heat+ corresponding to port 2, i.e., the positive electrode of the laser heating; the CellHeat+ corresponding to port 3, i.e., the positive electrode of the gas chamber heating; the Cell Heat- corresponding to port 4, i.e., the negative electrode of the gas chamber heating; the Laser- corresponding to port 5, i.e., the negative electrode of the laser power supply; the Laser+ corresponding to port 6, i.e., the positive electrode of the laser power supply; the Ntc+ corresponding to port 7, i.e., the positive electrode of the thermistor; the Ntc- corresponding to port 8, i.e., the negative electrode of the thermistor; the PT1000+ corresponding to port 9, i.e., the positive electrode of the platinum resistance; the PT1000- corresponding to port 10, i.e., the negative electrode of the platinum resistance; the PD- corresponding to port 11, i.e., the negative electrode of the photodiode; the PD+ corresponding to port 12, i.e., the positive electrode of the photodiode.

[0020] The description of the reference numerals is as follows: 1 is a quarter-wave plate; 2 is a peek frame (peek - polyetheretherketone); 3 is a VCSEL chip (VCSEL - vertical cavity surface emitting laser); 4 is an NTC thermistor (NTC - Negative Temperature Coefficient thermistor); 5 is an internal electrode; 6 is the upper layer 2 N The pole pitch heating coil (N is a positive integer); 7 is an aluminum nitride substrate; 8 is the lower layer 2 N The pole pitch heating coil; 9 is an FPC flexible circuit board (FPC - Flexible Printed Circuit) or an FPC flexible circuit; 10 is an inner electrode; 11 is an outer electrode. Specific embodiments

[0021] The following combines the accompanying drawings ( Figures 1 - 3 ) and embodiments to illustrate the present invention.

[0022] Figure 1 is a schematic structural diagram of an integrated micro VCSEL laser package structure based on non-magnetic materials according to the present invention. Figure 2 is a working principle diagram of an integrated micro VCSEL laser package structure based on non-magnetic materials according to the present invention.

[0023] Figure 3 is Figure 1 a schematic diagram of the function definition of the outer electrode interface of the FPC flexible circuit in Figures 1 to 3 As shown in the figure, an integrated micro VCSEL laser package structure based on non-magnetic materials includes a frame (i.e., the peek frame 2), the frame has a cavity surrounded by four side walls, the frame is a PEEK material product, and an aluminum nitride substrate 7 is arranged in the cavity. The upper surface of the aluminum nitride substrate 7 is provided with the upper layer 2 NThe pole pitch heating coil 6, where N is a positive integer, and a lower layer 2 is provided on the lower surface of the aluminum nitride substrate 7 N The pole pitch heating coil 8, and the upper layer 2 N A VCSEL chip 3, an NTC thermistor 4, and an internal electrode 5 are provided at the center of the pole pitch heating coil 6. A quarter-wave plate 1 fixed by the stepped structure in the cavity is provided directly above the VCSEL chip 3, and the lower layer 2 N An FPC flexible circuit board 9 is provided below the pole pitch heating coil 8. The FPC flexible circuit board 9 has an inner electrode 10 and an outer electrode 11 for connecting to an external circuit.

[0024] The FPC flexible circuit board 9 is respectively connected to the upper and lower layers 2 N The pole pitch heating coils (i.e., the upper layer 2 N The pole pitch heating coil 6 and the lower layer 2 N The pole pitch heating coils 8), the atomic gas chamber heating unit, the VCSEL chip 3, the PT1000 platinum resistance, the NTC negative feedback thermistor (i.e., the NTC thermistor 4), the PD signal sensor, and the external control circuit. The VCSEL chip 3 is respectively connected to the upper and lower layers 2 N The pole pitch heating coils (i.e., the upper layer 2 N The pole pitch heating coil 6 and the lower layer 2 N The pole pitch heating coils 8), the NTC negative feedback thermistor (i.e., the NTC thermistor 4), and the quarter-wave plate 1. The atomic gas chamber is respectively connected to the atomic gas chamber heating unit, the PD signal sensor, the PT1000 platinum resistance, and the quarter-wave plate 1.

[0025] The external control circuit controls the upper and lower layers 2 through the FPC flexible circuit board 9 in a PID control manner N The pole pitch heating coils (i.e., the upper layer 2 N The pole pitch heating coil 6 and the lower layer 2 N The pole pitch heating coils 8) to stabilize the temperature near the VCSEL chip 3 to the optimal temperature. The external control circuit supplies power to the VCSEL chip 3 through the FPC flexible circuit board 9. The external control circuit controls the atomic gas chamber heating unit to heat the atomic gas chamber through the FPC flexible circuit board 9 in a PID control manner. The PT1000 platinum resistance feeds back the temperature of the atomic gas chamber to the FPC flexible circuit board 9. The PD signal sensor transmits the magnetic field measurement signal collected from the atomic gas chamber to the FPC flexible circuit board 9. The NTC negative feedback thermistor (i.e., the NTC thermistor 4) feeds back the temperature measured from the VCSEL chip 3 to the FPC flexible circuit board 9. The quarter-wave plate 1 pumps the laser from the VCSEL chip 3 into the atomic gas chamber.

[0026] The outer electrode includes 12 ports. The port 1 corresponds to Laser Heat-, i.e., the negative electrode of laser heating. The port 2 corresponds to Laser Heat+, i.e., the positive electrode of laser heating. The port 3 corresponds to Cell Heat+, i.e., the positive electrode of cell heating. The port 4 corresponds to Cell Heat-, i.e., the negative electrode of cell heating. The port 5 corresponds to Laser-, i.e., the negative electrode of laser power supply. The port 6 corresponds to Laser+, i.e., the positive electrode of laser power supply. The port 7 corresponds to Ntc+, i.e., the positive electrode of the thermistor. The port 8 corresponds to Ntc-, i.e., the negative electrode of the thermistor. The port 9 corresponds to PT1000+, i.e., the positive electrode of the platinum resistance. The port 10 corresponds to PT1000-, i.e., the negative electrode of the platinum resistance. The port 11 corresponds to PD-, i.e., the negative electrode of the photodiode. The port 12 corresponds to PD+, i.e., the positive electrode of the photodiode.

[0027] The inner electrode 10 is located on the side close to the laser, and the outer electrode 11 is located on the side far from the laser. The magnetic field of the integrally miniaturized VCSEL laser with overall non-magnetic encapsulation is only 0.3 nT at a distance of 4 cm.

[0028] The present invention discloses an integrally miniaturized VCSEL laser packaging structure based on non-magnetic materials, which includes four parts: a frame, a VCSEL chip, a temperature control unit, and an integrated flexible circuit. The frame is composed of a quarter-wave plate (1), a PEEK frame, and an aluminum nitride substrate (7). The temperature control unit includes an NTC thermistor (4), an upper-layer 2 N pole-spacing heating coil (6) and a lower-layer 2 N pole-spacing heating coil (8), which are connected to the internal electrode (5) to an external circuit. The main body of the integrated flexible circuit part is an FPC flexible circuit (9). An inner electrode (10) is arranged on the side close to the laser, which can be connected to other components of the miniaturized atomic magnetometer. An outer electrode (11) is arranged on the side far from the laser, which can be connected to an external circuit. The present invention uses PEEK material and aluminum nitride as the frame, and uses 2 N pole-spacing heating coils to heat the VCSEL chip, reducing the low-frequency magnetic field interference caused by packaging and heating. At the same time, a quarter-wave plate is installed to shape the laser to obtain the circularly polarized light required by the atomic magnetometer, and the height of the laser is also controlled at 2.5 mm, which is more conducive to the miniaturization of the atomic magnetometer. Finally, an FPC flexible circuit is arranged at the bottom of the laser to connect each component of the atomic magnetometer to an external circuit, thereby controlling the atomic magnetometer as a whole. After measurement, the magnetic field of the integrally miniaturized VCSEL laser with overall non-magnetic encapsulation is only 0.3 nT at a distance of 4 cm, which is much smaller than the magnetic field of the TO-packaged VCSEL laser. Thus, a non-magnetic, miniaturized, and integrally packaged VCSEL laser is realized.

[0029] An integrated micro VCSEL laser packaging structure based on non-magnetic materials, comprising a frame, a VCSEL chip, a temperature control unit, and an integrated flexible circuit; the frame consists of a quarter-wave plate (1), a PEEK frame, and an aluminum nitride substrate (7); the temperature control unit includes an NTC thermistor (4), an upper-layer 2 N pole-distance heating coil (6) and a lower-layer 2 N pole-distance heating coil (8), which are connected to an external circuit through internal electrodes (5); the main body of the integrated flexible circuit part is an FPC flexible circuit (9), on one side close to the laser, an inner electrode (10) is arranged, which can be connected to other components of a miniaturized atomic magnetometer, and on the side far from the laser, an outer electrode (11) is arranged, which can be connected to an external circuit. The operation steps of each part are as follows:

[0030] Step 1, first, a control signal is sent by an external control circuit, and the upper and lower 2 N pole-distance heating coils (6)(8) are controlled to start heating through the FPC flexible circuit (9).

[0031] Step 2, it is fed back to the external control circuit through the NTC thermistor (4), and the PID algorithm is used to stabilize the temperature near the VCSEL chip (3) to the optimal temperature.

[0032] Step 3, when the laser reaches the optimal wavelength, the beam is shaped by the quarter-wave plate (1) installed on the frame to obtain the required circularly polarized light.

[0033] Step 4, the external control circuit controls the atom cell heating unit and the PT1000 platinum resistor to heat the atom cell through the inner electrode (10) of the FPC flexible circuit (9), and after PID control, the temperature of the atom cell is stabilized to the optimal working temperature.

[0034] Step 5, the top PD photodetector converts the laser with magnetic field information into an electrical signal, and transmits it to the external circuit through the FPC flexible circuit (9) to obtain the extremely weak magnetic field at this time.

[0035] In terms of material selection for this non-magnetic packaged VCSEL laser packaging structure for a miniaturized atomic magnetometer, considering less magnetic field interference and improving the sensitivity of the atomic magnetometer, PEEK and aluminum nitride are used as the frame structure, and non-magnetic glue is used for assembly to ensure the overall low magnetism.

[0036] This non-magnetic packaged VCSEL laser packaging structure for a miniaturized atomic magnetometer uses 2 N pole-distance heating coils to replace the existing TEC to heat the laser chip, solving the problem of low-frequency magnetic field in direct current heating and further improving the sensitivity of the atomic magnetometer.

[0037] The non-magnetic packaged VCSEL laser packaging structure for miniaturized atomic magnetometers integrates a quarter-wave plate, enabling beam shaping during laser emission, eliminating the need for further optical components in the atomic magnetometer, further reducing the volume of the atomic magnetometer, and improving the pumping effect of the atomic magnetometer.

[0038] The non-magnetic packaged VCSEL laser packaging structure for miniaturized atomic magnetometers integrates an FPC flexible circuit. The design of its inner electrodes can connect to other components of the atomic magnetometer, solving the problem of multi-component wiring in the miniaturized atomic magnetometer, achieving overall control of the atomic magnetometer, and improving stability.

[0039] As Figure 1 shown: An integrated micro VCSEL laser packaging structure based on non-magnetic materials includes a frame, a VCSEL chip, a temperature control unit, and an integrated flexible circuit. The frame consists of a quarter-wave plate (1), a PEEK frame (2), and an aluminum nitride substrate (7). The quarter-wave plate (1) is fixed directly above the VCSEL chip (3) by the stepped structure of the PEEK frame (2). The aluminum nitride substrate (7) is connected to the temperature control unit above and below. The temperature control unit includes an NTC thermistor (4), an upper 2 N pole-spacing heating coil (6), and a lower 2 N pole-spacing heating coil (8), which are connected to the external circuit through the internal electrodes (5). The NTC thermistor (4) is close to the VCSEL chip (3) and located in the middle of the upper 2 N pole-spacing heating coil (6) to collect the real-time temperature and control the heating coil through an external control circuit to adjust the temperature of the VCSEL chip (3). The main body of the integrated flexible circuit part is the FPC flexible circuit (9). Its inner electrodes (10) are arranged on the side close to the laser and can be connected to other components of the miniaturized atomic magnetometer. The outer electrodes (11) are arranged on the side far from the laser and can be connected to the external circuit to achieve overall control of the miniaturized atomic magnetometer.

[0040] Furthermore, the frame is made of non-magnetic materials. The outer frame is made of PEEK material with a size of 6mm * 6mm * 2.5mm. A stepped structure is provided 1mm deep inside, which can hold a quarter-wave plate. The corners are rounded outward to facilitate the picking and placing of the wave plate. A space of 5mm * 5mm * 0.7mm is dug out at the bottom to place other parts below. PEEK material is a special engineering plastic with excellent properties such as high temperature resistance, self-lubrication, easy processing, and high mechanical strength. It is non-magnetic itself and can be processed with high precision, suitable for the laser packaging of atomic magnetometers. Aluminum nitride is a covalent bond compound, without magnetism, has no influence on the measurement of the magnetometer, and at the same time has good thermal conductivity and a small thermal expansion coefficient. At the same time, aluminum nitride is an electrical insulator with good dielectric properties and is suitable as the substrate of the heating coil. The square quarter-wave plate has a thickness of 1mm and a side length of 4mm. Its optical axis is in the diagonal direction and is installed on the stepped structure in the PEEK frame using non-magnetic glue.

[0041] Furthermore, in the temperature control unit 2 N The pole pitch heating coil adopts the electroplated copper process with a size of 6mm * 6mm and a wire width of 0.15mm. Through 2 N The design of the coil type of the pole pitch, where N is a positive integer, ensures that the number of coils is even, and the currents are opposite, thereby canceling the magnetic field and further reducing the magnetic field brought by heating. The double-layer heating coil is connected to the external circuit through electrodes. The electrodes are made of pure copper and are gold-plated on the surface. A VCSEL chip, a thermistor, and an electrode are placed in the middle of the upper heating coil. The thermistor adopts a 10k ohm NTC thermistor (negative temperature coefficient thermistor). After collecting the temperature near the chip, the heating coil is controlled through the external circuit PID algorithm (proportional integral derivative control algorithm), so that the chip is stabilized to the optimal working temperature.

[0042] Furthermore, the integrated flexible circuit as a whole adopts an FPC flexible circuit. Six inner electrodes are provided on the side close to the laser, and outer electrodes are provided on the side far from the laser, which can be connected to the external control circuit. A flexible printed circuit board (Flexible Printed Circuit, abbreviated as FPC) is a highly reliable and extremely flexible printed circuit board made of polyimide or polyester film as the substrate. It has the characteristics of high wiring density, light weight, thin thickness, and good bendability. The specific port numbers and corresponding functions of the atomic magnetometer are given in Table 1. Among them, 3, 4, 9-12 correspond to other components above the laser and are connected to the gas chamber heating module, PT1000 (platinum resistance), and photodiode (PD) module of the atomic magnetometer through the inner electrodes of the FPC flexible circuit respectively. The other 1, 2, 5-8 are respectively connected to the heating coil, power supply, and temperature feedback resistor of the laser. Through this integrated flexible circuit, the overall control and output of the atomic magnetometer can be realized.

[0043] As Figure 2 shown: First, a control signal is sent by an external control circuit, and the upper and lower two N pole pitch heating coils (6) (8) are controlled by the FPC flexible circuit (9) to start heating. The temperature is fed back to the external control circuit through the NTC thermistor (4). Using the PID algorithm, the temperature near the VCSEL chip (3) is stabilized at the optimal temperature. At this time, the laser reaches the optimal wavelength, and the beam is shaped by the quarter-wave plate (1) installed on the frame to obtain the required circularly polarized light. Secondly, the external control circuit controls the atom cell heating unit and the PT1000 platinum resistor to heat the atom cell through the inner electrode (10) of the FPC flexible circuit (9). After being controlled by the PID algorithm and stabilizing the temperature of the atom cell at the optimal operating temperature, the top photodetector (PD) converts the laser with magnetic field information into an electrical signal, and transmits it to the external circuit through the FPC flexible circuit (9) to obtain the extremely weak magnetic field at this time.

[0044] As Figure 3 shown, the functions of ports 1 to 12 are respectively the negative electrode of laser heating (Laser Heat-), the positive electrode of laser heating (Laser Heat+), the positive electrode of cell heating (Cell Heat+), the negative electrode of cell heating (Cell Heat-), the negative electrode of laser power supply (Laser-), the positive electrode of laser power supply (Laser+), the positive electrode of NTC thermistor (Ntc+), the negative electrode of NTC thermistor (Ntc-), the positive electrode of platinum resistor (PT1000+), the negative electrode of platinum resistor (PT1000-), the negative electrode of photodiode (PD-), and the positive electrode of photodiode (PD+).

[0045] The content not described in detail in the specification of the present invention belongs to the prior art well-known to those skilled in the art. It is hereby pointed out that the above description helps those skilled in the art to understand the present invention, but does not limit the protection scope of the present invention. Any implementation that makes equivalent substitutions, modifications and improvements, and / or simplifies the above description without departing from the essential content of the present invention falls within the protection scope of the present invention.

Claims

1. An integrated micro VCSEL laser packaging structure based on non-magnetic materials, characterized in that: The frame comprises a cavity surrounded by side walls, the frame is made of PEEK material, an aluminum nitride substrate is arranged in the cavity, and an upper layer 2 is arranged on the upper surface of the aluminum nitride substrate N The inter-pole heating coil, N is a positive integer, and the lower surface of the aluminum nitride substrate is provided with a lower layer 2 N Pole pitch heating coil, the upper layer 2 N A VCSEL chip, an NTC thermistor and an internal electrode are arranged at the center of the inter-pole heating coil. A quarter wave plate fixed by a step structure in the cavity is arranged directly above the VCSEL chip. N An FPC flexible circuit board is arranged below the inter-pole heating coil, and the FPC flexible circuit board has an inner electrode and an outer electrode for connecting to an external circuit.

2. The integrated micro VCSEL laser packaging structure based on non-magnetic materials according to claim 1, characterized in that: The FPC flexible circuit board is connected to the upper and lower layers 2 N The inter-pole heating coil, atomic gas chamber heating unit, VCSEL chip, PT1000 platinum resistor, NTC negative feedback thermistor, PD signal sensor and external control circuit, the VCSEL chip is connected to the upper and lower layers 2 N The inter-pole heating coil, NTC negative feedback thermistor and quarter wave plate, and the atomic gas chamber are respectively connected to the atomic gas chamber heating unit, PD signal sensor, PT1000 platinum resistor and quarter wave plate.

3. The integrated micro VCSEL laser packaging structure based on non-magnetic materials according to claim 2, characterized in that: The external control circuit controls the upper and lower layers 2 by PID control through the FPC flexible circuit board N The polar spacing heating coil stabilizes the temperature near the VCSEL chip to the optimal temperature, the external control circuit supplies power to the VCSEL chip through the FPC flexible circuit board, the external control circuit controls the atomic gas chamber heating unit to heat the atomic gas chamber in a PID control manner through the FPC flexible circuit board, the PT1000 platinum resistor feeds back the temperature of the atomic gas chamber to the FPC flexible circuit board, the PD signal sensor transmits the magnetic field measurement signal collected from the atomic gas chamber to the FPC flexible circuit board, the NTC negative feedback thermistor feeds back the temperature measured by the VCSEL chip to the FPC flexible circuit board, and the quarter wave plate pumps the laser from the VCSEL chip to the atomic gas chamber.

4. The integrated micro VCSEL laser packaging structure based on non-magnetic materials according to claim 1, characterized in that: The outer electrode includes 12 ports, port 1 corresponds to Laser Heat-, that is, the negative electrode of laser heating, port 2 corresponds to Laser Heat+, that is, the positive electrode of laser heating, port 3 corresponds to Cell Heat+, that is, the positive electrode of air chamber heating, port 4 corresponds to Cell Heat-, that is, the negative electrode of air chamber heating, port 5 corresponds to Laser-, that is, the negative electrode of laser power supply, port 6 corresponds to Laser+, that is, the positive electrode of laser power supply, port 7 corresponds to Ntc+, that is, the positive electrode of thermistor, port 8 corresponds to Ntc-, that is, the negative electrode of thermistor, port 9 corresponds to PT1000+, that is, the positive electrode of platinum resistor, port 10 corresponds to PT1000-, that is, the negative electrode of platinum resistor, port 11 corresponds to PD-, that is, the negative electrode of photodiode, and port 12 corresponds to PD+, that is, the positive electrode of photodiode.

5. The integrated micro VCSEL laser packaging structure based on non-magnetic materials according to claim 1, characterized in that: The inner electrode is located at a side close to the laser, and the outer electrode is located at a side far from the laser.

6. The integrated micro VCSEL laser packaging structure based on non-magnetic materials according to claim 1, characterized in that: The integrated micro VCSEL laser in a monolithic, magnetic-free package has a magnetic field of only 0.3nT at a distance of 4cm.

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