Integrated miniaturized atomic magnetometer and non-magnetic vcsel laser module

Abstract

This invention discloses an integrated miniaturized atomic magnetometer and its non-magnetic VCSEL laser module, including a VCSEL chip, a heating coil, a current source, a signal source, and a power amplifier. The AC signal output from the signal source is amplified by the power amplifier with an adjustable amplification factor and then output to the heating coil to heat the VCSEL chip. It also includes a PID controller; by detecting the voltage across the input current of the VCSEL chip or by detecting the voltage across the heating coil, the power amplifier is controlled by the PID controller to achieve VCSEL chip temperature control. This avoids the magnetic field inherent in the device itself directly affecting the sensitivity of the atomic magnetometer and interfering with the measurement results. It also reduces the size of the laser module and the integrated atomic magnetometer.

Description

Technical Field

[0001] This invention belongs to the field of VCSEL laser driving and quantum precision measurement technology, specifically relating to a driving method for a non-magnetic VCSEL laser chip and the design of a miniaturized atomic magnetometer. In particular, it relates to a non-magnetic VCSEL laser module and an integrated miniaturized atomic magnetometer using this non-magnetic VCSEL laser module. Background Technology

[0002] With the continuous miniaturization and integration of optical devices, vertical-cavity surface-emitting lasers (VCSELs) have gradually attracted widespread attention due to their advantages such as narrow linewidth, low power consumption, high modulation speed, small size, and ease of integration. They are widely used in the field of miniaturized atomic magnetometers, atomic clocks, atomic gyroscopes, and other novel quantum sensors. These quantum precision measurement instruments have broad application prospects in fields such as national defense, biomedicine, and geological exploration.

[0003] For example, an optical atomic magnetometer developed using a miniaturized VCSEL laser can perform multi-channel magnetocardiography (MCG) and magnetoencephalography (MEG) measurements at room temperature. It is smaller in size than traditional superconducting magnetometers, accommodating more channels per unit volume. Typically, VCSEL lasers use magnetic packaging, which can interfere with measurements. A VCSEL laser solution with non-magnetic packaging and its driving technology can improve the accuracy, interference resistance, and environmental adaptability of these quantum sensors.

[0004] VCSEL lasers require operation within a specific current and temperature range. Typically, a high-precision current source and a Thermo Electric Cooler (TEC) control the laser chip's temperature. A thermistor detects the temperature near the laser chip, and an external feedback loop and the TEC heat or cool the VCSEL laser chip. The advantage of this approach is its ability to quickly and accurately control the temperature near the laser chip to near its operating point. However, the thermistor is usually placed at a distance from the laser chip and cannot accurately reflect its current operating temperature; there is a temperature difference and time delay between the two. Furthermore, the TEC generates a significant magnetic field. To reduce residual magnetic interference during laser chip operation, common practices include increasing the distance between the laser chip and subsequent measurement devices, or using magnetic shielding to reduce the residual magnetism of the laser module. Summary of the Invention

[0005] To address the aforementioned technical problems, the purpose of this invention is to provide an integrated miniaturized atomic magnetometer and its non-magnetic VCSEL laser module. It proposes a heating system based on a non-magnetic VCSEL laser to avoid the magnetic field inherent in the device itself directly affecting the sensitivity of the atomic magnetometer and interfering with measurement results. This reduces the size of the laser module, thereby reducing the overall size of the integrated atomic magnetometer and improving the sensitivity of quantum precision measurement sensors such as atomic magnetometers, atomic clocks, and atomic gyroscopes.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A non-magnetic VCSEL laser module, comprising:

[0008] VCSEL chips used to generate lasers;

[0009] Heating coils used to maintain the operating temperature of VCSEL chips;

[0010] Current source used to drive VCSEL chip;

[0011] Signal source and power amplifier;

[0012] The AC signal output from the signal source is amplified by a power amplifier with adjustable amplification factor and then output to the heating coil to complete the heating of the VCSEL chip.

[0013] It also includes a PID controller; by detecting the voltage across the input current of the VCSEL chip or by detecting the voltage across the heating coil, the power amplifier is controlled by feedback from the PID controller to achieve VCSEL chip temperature control.

[0014] In this way, temperature is measured by the resistance of the heating coil and / or the voltage of the VCSEL chip, replacing the original thermistor or thermocouple module in the laser module. Components that introduce residual magnetic fields are no longer retained, thus avoiding the direct impact of the magnetic field on the sensitivity of the atomic magnetometer and interference with the measurement results.

[0015] Preferably, the VCSEL chip and the heating coil are disposed on the same silicon substrate.

[0016] Preferably, the device also includes a heating coil parameter monitoring module, which detects the voltage change across the heating coil and outputs the data to a first PID controller. The first PID controller controls the power amplifier to achieve VCSEL chip temperature control based on the voltage-temperature relationship of the heating coil.

[0017] Preferably, the voltage-temperature relationship of the heating coil is obtained by pre-measurement and is pre-input as a function into the first PID controller; the first PID controller controls the output power of the power amplifier according to the error signal between the target temperature value and the actual temperature value, thereby stabilizing the temperature of the silicon substrate and the VCSEL laser chip.

[0018] Preferably, the device also includes a VCSEL chip voltage monitoring module. The VCSEL chip voltage monitoring module detects the voltage across the input current of the VCSEL chip and outputs the data to the second PID controller. The second PID controller controls the power amplifier to achieve VCSEL chip temperature control based on the voltage-temperature relationship of the VCSEL chip.

[0019] Preferably, the voltage-temperature relationship of the VCSEL chip is obtained by pre-measurement and is pre-input as a function into the second PID controller; the second PID controller controls the output power of the power amplifier based on the error signal between the target temperature value and the actual temperature value, thereby stabilizing the temperature of the VCSEL laser chip.

[0020] Preferably, the heating coil is arranged on the silicon substrate in a two-layer serpentine routing manner, with the current flowing in opposite directions in the two adjacent layers of routing; the heating coil and the VCSEL chip are electrically insulated from each other, and the VCSEL chip is located in the middle of the heating coil.

[0021] An integrated miniaturized atomic magnetometer based on a non-magnetic VCSEL laser chip includes an atomic magnetometer integrated module, on which the non-magnetic VCSEL laser module as described above is disposed, as well as a collimation module, a polarization control module, an atomic gas chamber insulation layer, a triaxial magnetic field coil, an atomic gas chamber with a heating system, an atomic magnetometer optical path, and a photodetector.

[0022] This invention, by employing the above-mentioned technical solution, utilizes the resistance of the heating coil or the operating voltage of the laser chip as an error signal, and controls the laser temperature through a first feedback loop, a second feedback loop, or a single feedback loop. This avoids the direct impact of the magnetic field inherent in the device itself on the sensitivity of the atomic magnetometer and interference with the measurement results. It reduces the size of the laser module and the integrated atomic magnetometer, thereby improving the sensitivity of quantum precision measurement sensors such as atomic magnetometers, atomic clocks, and atomic gyroscopes. Attached Figure Description

[0023] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments of this application and their descriptions are used to explain this application and do not constitute a limitation thereof.

[0024] Figure 1This is a schematic diagram of the miniaturized atomic magnetometer system based on a non-magnetic VCSEL laser integrated according to the present invention.

[0025] Figure 2 This is a schematic diagram of the non-magnetic VCSEL laser module of the present invention;

[0026] Figure 3 This is a schematic diagram of the VCSEL chip and heating coil of the present invention on a silicon substrate.

[0027] The components include: 1. Atomic magnetometer integrated module; 2. Non-magnetic VCSEL laser module; 3. Collimation module; 4. Polarization control module; 5. Atomic gas cell insulation layer; 6. Triaxial magnetic field coil; 7. Atomic gas cell with heating system; 8. Atomic magnetometer optical path; 9. Photodetector.

[0028] 201. VCSEL chip; 202. Heating coil; 203. Silicon substrate; 204. Heating coil parameter monitoring module; 205. First PID controller; 206. VCSEL chip voltage monitoring module; 207. Second PID controller; 208. Power amplifier; 209. Signal source; 210. Current source. Detailed Implementation

[0029] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0030] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0031] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0032] In the description of this invention, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0033] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0034] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more, unless explicitly defined otherwise.

[0035] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0036] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature. Example

[0037] like Figure 1 The illustrated integrated miniaturized atomic magnetometer based on a non-magnetic VCSEL laser chip includes an atomic magnetometer integrated module 1, a non-magnetic VCSEL laser module 2, a collimation module 3, a polarization control module 4, an atomic gas chamber insulation layer 5, a triaxial magnetic field coil 6, an atomic gas chamber 7 with a heating system, an atomic magnetometer optical path 8, and a photodetector 9, all disposed in the atomic magnetometer integrated module 1.

[0038] The non-magnetic VCSEL laser module 2 outputs a stable rubidium atom D1 line laser with a power >200μW. After passing through the collimation module 3, such as an aspherical lens with a diameter of 6.6mm, the diverging spot can be shaped into a uniformly collimated circular or elliptical spot. After passing through the polarization control module 4, such as a 5mm×5mm broadband circular polarizer, the polarization of the emitted laser is adjusted to collimated circularly polarized light. The collimated circularly polarized light is incident on the preheated rubidium atom gas cell, such as a 5mm×5mm×5mm saturated rubidium vapor cell, and interacts with the rubidium atoms. The triaxial magnetic field coil 6 can be designed and manufactured by flexible printed circuit board (FPC) to compensate for part of the triaxial magnetic field of the atomic gas cell and can independently superimpose an AC radio frequency modulation field of a certain frequency in three directions according to the principle of atomic magnetometer. The collimated circularly polarized light is finally incident on the photodetector 9. The D1 line laser output by the non-magnetic VCSEL laser module 2 can polarize rubidium atoms. When the external magnetic field perpendicular to the light direction changes, the polarization vector of the rubidium atoms changes, thus affecting the absorption of the laser by the rubidium atoms. The change pattern of the light absorption by the rubidium atoms can be obtained by the photodetector 9, thereby demodulating the change of the external magnetic field to achieve magnetic field measurement. The above design can be compactly integrated into a miniaturized atomic magnetometer of 17mm×15mm×12mm.

[0039] In this preferred embodiment, the non-magnetic VCSEL laser modules 2 are all connected to the atomic magnetometer integrated module 1 using high-temperature resistant plastic, wherein the heating wire, temperature test wire, and PD receiving wire are all FPCs and are all integrated onto the circuit board.

[0040] like Figure 2 As shown, the non-magnetic VCSEL laser module 2 includes a VCSEL chip 201, a heating coil 202, a silicon substrate 203, a heating coil parameter monitoring module 204, a first PID controller 205, a power amplifier 208, a second PID controller 207, a VCSEL chip voltage monitoring module 206, a signal source 209, and a precision current source 210.

[0041] In the non-magnetic VCSEL laser module 2, a precision current source 210 is used to generate a suitable high-precision current to drive the VCSEL laser chip 201, with a current of approximately 2mA. The VCSEL chip 201 generates a stable power, fixed wavelength rubidium atom D1-line laser. The heating coil 202 is used to maintain the stable operating temperature of the VCSEL laser chip. The AC signal output from the signal source 209 is amplified by the power amplifier 208 with an adjustable amplification factor and then output to the heating coil to complete the heating of the silicon substrate 203 and the VCSEL laser chip 201. The heating coil parameter monitoring module 204 can detect the voltage change across the heating coil 202 and output the data to the first PID controller. 205. The voltage change of the heating coil 202 is related to its temperature; the VCSEL chip voltage monitoring module 206 can monitor the voltage across the laser input current and output data to the second PID controller 207, which is related to the current temperature of the laser chip; both the first PID controller and the second PID controller can control the power amplifier amplification factor, wherein the first PID controller mainly controls the overall temperature of the laser module, and the second PID controller further precisely controls the temperature of the VCSEL laser chip, thereby achieving precise control of the laser temperature; in different situations, the requirements for the laser chip temperature control accuracy are not the same, and the two feedback control methods can be used alone or in combination.

[0042] In this preferred embodiment, both the VCSEL chip 201 and the heating coil 202 are electrically connected to the integrated circuit board; for example... Figure 3 As shown, the VCSEL chip 201 and the heating coil 202 are both fixed on the silicon substrate 203. The heating coil 202 can adopt a double-layer serpentine wiring, which has the advantage that the residual magnetic field generated by the straight part of each layer can cancel each other out. The wiring current flow between the two layers can be geometrically controlled to be opposite, thereby further canceling the residual magnetic field introduced by heating and minimizing the residual magnetic field introduced by VCSEL heating.

[0043] In this preferred embodiment, the signal source 209 is implemented using a DDS chip (Direct Digital Frequency Synthesis), such as AD9854, with an output frequency range that can be set to 100kHz to 1MHz. The AC signal generated by the signal source is output to the heating coil after passing through a power amplifier unit with adjustable amplification. The amplification of the power amplifier unit is jointly controlled by PID1 and PID2.

[0044] In this preferred embodiment, the resistance of the heating coil 202 increases with the increase of temperature. The AC voltage value of the heating coil load has a one-to-one correspondence with the temperature, which can be obtained by pre-measurement and input as a function into the first PID controller. The error signal between the target temperature value and the actual temperature value can be obtained. The first PID controller, made of a microcontroller or FPGA, controls the output power of the power amplifier unit, thereby stabilizing the temperature of the silicon substrate and the VCSEL laser chip.

[0045] In this preferred embodiment, the VCSEL chip voltage monitoring module 206 can collect the voltage across the laser current input terminals to detect the laser's operating status. The laser operating voltage and the real-time laser temperature have a one-to-one correspondence, which can be obtained through prior measurement. This voltage is then input as a function into the second PID controller. Based on the difference between the collected laser voltage signal and the target voltage, an error signal can be obtained. A microcontroller or FPGA is used to implement the second PID controller, which controls the output power of the power amplifier, further precisely stabilizing the VCSEL laser chip temperature. The first PID controller and the second PID controller jointly control the power amplifier's amplification factor, thereby stabilizing the temperature of the non-magnetic VCSEL laser chip at the set temperature.

[0046] In the description of this specification, the terms "one embodiment," "some embodiments," "one implementation," "specific implementation," "other implementation," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment, implementation, or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described above can also be combined in any suitable manner in one or more embodiments, implementations, or examples. The technical solutions described in this invention also include technical solutions formed by any one or more specific features, structures, materials, or characteristics described above, either individually or in combination.

[0047] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions, alterations, deletions of some features, additions of features, or recombinations of features to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the innovative principles of the present invention shall still fall within the scope of the technical solutions of the present invention.

Claims

1. A non-magnetic VCSEL laser module, comprising: VCSEL chips used to generate lasers; Heating coils used to maintain the operating temperature of VCSEL chips; Current source used to drive VCSEL chip; Signal source and power amplifier; The AC signal output from the signal source is amplified by a power amplifier with adjustable amplification factor and then output to the heating coil to complete the heating of the VCSEL chip. The feature is that it also includes a PID controller; the voltage across the input current of the VCSEL chip is detected by the VCSEL chip voltage monitoring module or the voltage across the heating coil is detected by the heating coil parameter monitoring module. The error signal between the target temperature value and the actual temperature value is obtained by using the correspondence between the AC voltage value of the heating coil load and the temperature or the correspondence between the laser working voltage and the laser real-time temperature obtained by pre-measurement. The VCSEL chip temperature control is achieved by combining the feedback control power amplifier of the PID controller.

2. The non-magnetic VCSEL laser module according to claim 1, characterized in that, The VCSEL chip and the heating coil are mounted on the same silicon substrate.

3. A non-magnetic VCSEL laser module according to claim 2, characterized in that, The heating coil parameter monitoring module detects the voltage change across the heating coil and outputs the data to the first PID controller. The first PID controller controls the power amplifier to achieve VCSEL chip temperature control based on the voltage-temperature relationship of the heating coil.

4. A non-magnetic VCSEL laser module according to claim 3, characterized in that, The voltage-temperature relationship of the heating coil is obtained through prior measurement and is pre-input as a function to the first PID controller. The first PID controller controls the output power of the power amplifier based on the error signal between the target temperature value and the actual temperature value, thereby stabilizing the temperature of the silicon substrate and the VCSEL laser chip.

5. A non-magnetic VCSEL laser module according to claim 2, characterized in that, The VCSEL chip voltage monitoring module detects the voltage across the input current terminals of the VCSEL chip and outputs the data to the second PID controller. The second PID controller controls the power amplifier to achieve VCSEL chip temperature control based on the voltage-temperature relationship of the VCSEL chip.

6. A non-magnetic VCSEL laser module according to claim 5, characterized in that, The voltage-temperature relationship of the VCSEL chip is obtained through prior measurement and is pre-input as a function to the second PID controller. The second PID controller controls the output power of the power amplifier based on the error signal between the target temperature value and the actual temperature value, thereby stabilizing the temperature of the VCSEL laser chip.

7. A non-magnetic VCSEL laser module according to claim 2, characterized in that, The heating coil is arranged on the silicon substrate through two layers of serpentine traces, with the current flowing in opposite directions in the two adjacent layers of traces; the heating coil and the VCSEL chip are electrically insulated from each other, and the VCSEL chip is located in the middle of the heating coil.

8. An integrated miniaturized atomic magnetometer based on a non-magnetic VCSEL laser chip, characterized in that, It includes an atomic magnetometer integrated module, on which a non-magnetic VCSEL laser module as described in any one of claims 1 to 7 is provided, as well as a collimation module, a polarization control module, an atomic gas chamber insulation layer, a triaxial magnetic field coil, an atomic gas chamber with a heating system, an atomic magnetometer optical path, and a photodetector.

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