Physical System of CPT Atomic Clock

Abstract

This application relates to the physical system of a CPT atomic clock, including a mounting substrate and a laser component, a collimating lens component, and a magnetic shielding shell component arranged in sequence thereon. An alkali metal gas chamber is provided inside the magnetic shielding shell component, and light passing holes are formed on opposite sides of the magnetic shielding gas chamber component. The optical axis of the laser component, the optical axis of the collimating lens component, and the light passing holes on the magnetic shielding shell component are coaxially arranged. The laser component includes a first adiabatic bracket, a first power field effect transistor, a VCSEL laser diode, and a first thermistor. The lower part of the first adiabatic bracket is fixedly connected to the mounting substrate, the first power field effect transistor is arranged on the first adiabatic bracket, and both the VCSEL laser diode and the first thermistor are fixed to the heat sink of the first power field effect transistor. By connecting the S pole and D pole of the first power field effect transistor to the power supply and the ground respectively, the self-heating of the field effect transistor is directly used to heat the laser diode, and the utilization efficiency of electric energy is high.

Description

Technical Field

[0001] This application relates to the field of atomic clocks, and particularly to a physical system of a CPT atomic clock. Background Art

[0002] The CPT atomic clock is a practical atomic clock that can be miniaturized and has low power consumption, with great application potential. The CPT atomic clock consists of a physical part and a circuit part. During operation, the physical part needs to be heated and temperature-controlled, so it is an important energy-consuming part of the main unit. The overall power consumption of a typical CPT atomic clock is usually about 1W, which has certain advantages compared with traditional rubidium atomic clocks (typical power consumption of 8W - 15W) and oven-controlled crystal oscillators (typical power consumption of 2W - 5W), but the advantage is not particularly obvious. The physical part of the new CPT atomic clock uses MEMS technology to reduce the size, and uses technologies such as high-vacuum insulation to increase the thermal resistance, and the power consumption can be reduced to 0.1W - 0.25W, which has obvious advantages compared with traditional atomic clocks and oven-controlled crystal oscillators. However, the MEMS technology and high-vacuum insulation are difficult, the manufacturing is complex, and the product cost is high. Summary of the Invention

[0003] In view of this, this application proposes a physical system of a CPT atomic clock, including a mounting substrate and a laser component, a collimating lens component, and a magnetic shielding shell component arranged in sequence on the mounting substrate; an alkali metal gas chamber is arranged inside the magnetic shielding shell component, and light passing holes are opened on opposite sides of the magnetic shielding gas chamber component; the optical axis of the laser component, the optical axis of the collimating lens component, and the light passing holes on the magnetic shielding shell component are coaxially arranged; the laser component includes a first adiabatic bracket, a first power field effect transistor, a VCSEL laser diode, and a first thermistor; the lower part of the first adiabatic bracket is fixedly connected to the mounting substrate; the first power field effect transistor is arranged on the first adiabatic bracket; both the VCSEL laser diode and the first thermistor are fixed to the heat sink of the first power field effect transistor.

[0004] In a possible implementation, the VCSEL laser diode is adhesively fixed to the heat sink of the first power field effect transistor through conductive adhesive.

[0005] In a possible implementation, one end of the first thermistor is fixedly welded to the heat sink of the first power field effect transistor.

[0006] In a possible implementation, the first power field effect transistor is a P-type power field effect transistor. The S terminal of the first power field effect transistor is electrically connected to the power supply. The D terminal of the first power field effect transistor is connected to the heat sink on the first power field effect transistor to ground the D terminal of the first power field effect transistor. The negative electrode of the VCSEL laser diode is electrically connected to the D terminal of the first power field effect transistor and is grounded. One end of the first thermistor is electrically connected to the D terminal of the first power field effect transistor and is grounded. The D terminal of the first power field effect transistor, the negative electrode of the VCSEL laser diode, and one end of the first thermistor are equipotential points.

[0007] In a possible implementation, the magnetic shielding shell assembly includes an outer shielding box, a second adiabatic bracket, and an inner shielding box. The outer shielding box is fixedly arranged on the mounting substrate. The second adiabatic bracket is in a "Π" shape and is fixed to the bottom inner wall of the outer shielding box. The inner shielding box is located inside the outer shielding box. The inner shielding box is fixed to the second adiabatic bracket, and the alkali metal gas chamber is placed inside the inner shielding box.

[0008] In a possible implementation, the magnetic shielding shell assembly further includes coils. The inner shielding box is in a "convex" shape and is horizontally placed on the second adiabatic bracket. Coils are respectively installed in the symmetric two side chambers of the inner shielding box. The coils are coaxially arranged with the light passing hole. The alkali metal gas chamber is made of a cylindrical light-transmitting material, and the coils on both sides are respectively attached to the two light-transmitting surfaces of the alkali metal gas chamber.

[0009] In a possible implementation, a second power field effect transistor and a second thermistor are fixedly installed outside the relatively protruding side walls of the inner shielding box.

[0010] In a possible implementation, the distance between the outer shielding box and the inner shielding box is greater than 1 mm.

[0011] In a possible implementation, a quarter-wave plate and a light attenuator are arranged on the light incident side of the outer shielding box. A photodiode is arranged on the light output side of the outer shielding box. The outer shielding box is a square box. The first thermistor and the second thermistor are both NTC thermistors. The material of the alkali metal gas chamber is glass. The gaps between the coils, the alkali metal gas chamber, and the inner wall of the inner shielding box are filled with filling glue.

[0012] In a possible implementation, the collimating lens assembly includes a lens bracket and a collimating lens body. The lens bracket is in an inverted "U" shape and is fixedly arranged on the mounting substrate. The collimating lens body is installed inside the top of the lens bracket and matches the arc structure of the lens bracket.

[0013] Advantages of the present application: By optimizing the structure on the laser component, the VCSEL laser diode and the first thermistor are adhesively or soldered and directly fixed on the heat sink of the first power field-effect transistor, eliminating the need for an external power resistor. The S pole and D pole of the field-effect transistor are respectively connected to the power supply and the ground, and the self-heating of the field-effect transistor is directly used for temperature control heating, with high utilization efficiency of electric energy. And the entire field-effect transistor is fixed to the adiabatic bracket. The high thermal conductivity of the metal connection helps to keep the temperature consistent at various positions of the laser source component. The design of the first adiabatic bracket and its small volume minimizes the overall heat loss of the constant temperature body as much as possible, so as to improve the temperature control efficiency of the laser source component. While meeting the basic electrical performance of this physical structure, it effectively reduces the power consumption and volume of the whole machine, and improves the overall cost performance of the CPT atomic clock of the present application.

[0014] Other features and aspects of the present application will become clear from the following detailed description of the exemplary embodiments with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The drawings included in the specification and constituting a part of the specification, together with the specification, illustrate the exemplary embodiments, features, and aspects of the present application and are used to explain the principles of the present application.

[0016] Figure 1 A side view of the physical system of the CPT atomic clock showing an embodiment of the present application;

[0017] Figure 2 A perspective view of the magnetic shielding shell assembly showing an embodiment of the present application;

[0018] Figure 3 A front view of the laser component showing an embodiment of the present application.

[0019] Figure 4 A schematic diagram of the circuit part of the laser component showing an embodiment of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] The following will detail various exemplary embodiments, features, and aspects of the present application with reference to the accompanying drawings. The same reference numerals in the drawings denote elements having the same or similar functions. Although various aspects of the embodiments are shown in the drawings, the drawings do not have to be drawn to scale unless otherwise specified.

[0021] Among them, it should be understood that the orientation or positional relationship indicated by terms such as "center", "longitudinal", "transverse", "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present application or simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be construed as a limitation on the present application.

[0022] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present application, "a plurality" means two or more unless otherwise specifically defined.

[0023] The special term "exemplary" here means "serving as an example, embodiment or illustration". Any embodiment illustrated as "exemplary" here does not have to be construed as superior or better than other embodiments.

[0024] In addition, for better illustration of the present application, numerous specific details are given in the following specific implementation manners. Those skilled in the art should understand that the present application can be implemented without some specific details. In some instances, methods, means, elements and circuits well-known to those skilled in the art are not described in detail so as to highlight the gist of the present application.

[0025] As Figures 1-4 shown, the physical system of the CPT atomic clock includes: a mounting substrate 40 and a laser assembly 10, a collimating lens assembly 20, and a magnetic shielding shell assembly 30 arranged in sequence on the mounting substrate 40. An alkali metal gas chamber 34 is provided inside the magnetic shielding shell assembly 30. Light passing holes are formed on opposite sides of the magnetic shielding gas chamber assembly. The optical axes of the laser assembly 10, the collimating lens assembly 20, and the light passing holes on the magnetic shielding shell assembly 30 are coaxially arranged. The laser assembly 10 includes a first adiabatic bracket 14, a first power field effect transistor 12, a VCSEL laser diode 11, and a first thermistor 13. The lower part of the first adiabatic bracket 14 is fixedly connected to the mounting substrate 40. The first power field effect transistor 12 is arranged on the first adiabatic bracket 14. Both the VCSEL laser diode 11 and the first thermistor 13 are fixed to the heat sink of the first power field effect transistor 12.

[0026] As Figure 3 、 Figure 4As shown, in this embodiment, by optimizing the structure on the laser component 10, the VCSEL laser diode 11 and the first thermistor 13 are adhesively bonded or welded directly to the heat sink of the first power field-effect transistor 12, eliminating the need for an external power resistor. The S pole and D pole of the first power field-effect transistor 12 are respectively connected to the power supply and the ground. The bottom of the heated VCSEL laser diode 11 is tightly fixed to the D pole of the field-effect transistor heat sink. Utilizing the self-heating of the field-effect transistor, the utilization efficiency of electrical energy is high. And the entire field-effect transistor is fixed to the adiabatic bracket. The high thermal conductivity of the metal connection helps to keep the temperature consistent at each position of the laser source component. The design of the first adiabatic bracket 14 and its small size minimize the overall heat loss of the constant temperature body as much as possible, so as to improve the temperature control efficiency of the laser source component. While meeting the basic electrical performance of this physical structure, it effectively reduces the power consumption and volume of the whole machine, and improves the overall cost performance of the CPT atomic clock of this application.

[0027] Figure 1 The optical axis of the laser component 10, the optical axis of the collimating lens component 20, and the optical path 1 on the light passing hole of the magnetic shielding shell component 30 are schematic diagrams.

[0028] In one specific embodiment, the VCSEL laser diode 11 is adhesively bonded to the heat sink of the first power field-effect transistor 12 through conductive adhesive.

[0029] In this embodiment, preferably, the bottom of the heated VCSEL laser diode 11 and the D pole of the first power field-effect transistor 12 are tightly connected together by conductive silver paste. Compared with setting an external series power resistor and a field-effect transistor between the power supply and the ground to heat the heated object, and the energy consumed by the self-heating of the field-effect transistor is not utilized, the conductive silver paste has a higher electrical energy utilization efficiency for making the two closely adhere.

[0030] As Figure 3 shown, in one specific embodiment, one end of the first thermistor 13 is welded and fixed to the heat sink of the first power field-effect transistor 12.

[0031] As Figure 3 、 Figure 4As shown, in one specific embodiment, the first power field-effect transistor 12 is a P-type power field-effect transistor. The first power field-effect transistor 12 is a P-type power field-effect transistor. The S pole of the first power field-effect transistor 12 is electrically connected to the power supply. The D pole of the first power field-effect transistor 12 is connected to the heat sink on the first power field-effect transistor 12 to ground the D pole of the first power field-effect transistor 12; the negative pole of the VCSEL laser diode 11 is electrically connected to the D pole of the first power field-effect transistor 12 and is grounded; one end of the first thermistor 13 is electrically connected to the D pole of the first power field-effect transistor 12 and is grounded; the D pole of the first power field-effect transistor 12, the negative pole of the VCSEL laser diode 11, and one end of the first thermistor 13 are equipotential points.

[0032] In this embodiment, it is preferably a P-type power field-effect transistor with a metal heat sink. Its metal heat sink is connected to the D pole. When working, the D pole can be grounded. Since the negative pole of the VCSEL laser diode and one end of the thermistor can also be grounded, the three can be directly connected, making the negative pole of the VCSEL laser diode 11, the D pole of the heat sink of the first power field-effect transistor 12, and one end of the first thermistor 13 all equipotential points connected to GND. They can be directly lapped with each other, simplifying the internal and external wiring, making the design of the laser assembly 10 more reasonable, the structure simpler, and facilitating the installation by those skilled in the art. More space can be saved, enabling the overall volume of the CPT atomic clock to be made smaller.

[0033] In addition, for an N-type power field-effect transistor, the D pole must be connected to the power supply and the S pole must be grounded when working. The heat sink (D pole) cannot be connected to the negative pole of the VCSEL light-emitting diode and one end of the thermistor. Instead, insulation treatment is required. After using insulation, the overall structure becomes more complex, and the addition of the insulating material is not conducive to heat conduction. Therefore, the selection of the P-type power field-effect transistor is superior to that of the N-type power field-effect transistor.

[0034] In one specific embodiment, the magnetic shielding shell assembly 30 further includes an outer shielding box 31, a second adiabatic bracket 33, and an inner shielding box 32. The outer shielding box 31 is fixedly arranged on the mounting substrate 40. The second adiabatic bracket 33 is in a "Π" shape and is fixed to the bottom inner wall of the outer shielding box 31. The inner shielding box 32 is located inside the outer shielding box 31. The inner shielding box 32 is fixed to the second adiabatic bracket 33, and the alkali metal gas chamber 34 is placed inside the inner shielding box 32.

[0035] In this embodiment, the outer shielding box 31, the second adiabatic bracket 33, and the inner shielding box 32. Through holes of the same size are provided on opposite sides of the outer shielding box 31 and the inner shielding box 32, and one side is a light incident hole and the other side is a light exit hole.

[0036] More specifically, the outer shielding box 31 is at room temperature and does not require temperature control. The inner shielding box 32 needs to be heated and temperature-controlled. A second adiabatic bracket 33 is installed in the middle of the bottom of the outer shielding box 31. The second adiabatic bracket 33 supports and fixes the inner shielding box 32, and the alkali metal gas chamber 34 is located inside the inner shielding box 32.

[0037] As Figure 2 shown, in one specific embodiment, the magnetic shielding shell assembly 30 further includes coils 35. The inner shielding box 32 is in a "convex" shape and is horizontally placed on the second adiabatic bracket 33. Coils 35 are respectively installed in the symmetrically arranged two side chambers of the inner shielding box 32. The coils 35 are coaxially arranged with the light passing holes. The alkali metal gas chamber 34 is made of a square light-transmitting material, and the coils 35 on both sides are respectively attached to the two light-transmitting surfaces of the alkali metal gas chamber 34.

[0038] In this embodiment, the longitudinal projection of the inner shielding box 32 is in a "convex" shape, that is, the convex-shaped inner shielding box 32 is horizontally placed inside the outer shielding box 31. The center line of the convex character is the axis of symmetry. The cavities on both sides of the convex character are used to place the coils 35 on both sides of the alkali metal gas chamber 34 respectively. The inner side of the coil 35 is closely attached to the light-transmitting surface of the gas chamber, and the outer side fills the reserved gap between the coil 35 and the alkali metal gas chamber 34 in the inner shielding chamber with heat-conducting glue to ensure that the overall structure will not shake inside the inner shielding chamber. It should be particularly noted that the light-transmitting surface of the alkali metal gas chamber 34 cannot be covered by heat-conducting glue or the like.

[0039] A small part of gap allowance is left in the top cavity set as convex to adjust the light-transmitting surface of the alkali metal gas chamber 34 to be consistent with the center of the light passing hole. This structure can effectively facilitate the fine adjustment for those skilled in the art.

[0040] In one specific embodiment, a second power field effect transistor 36 and a second thermistor are fixedly installed on the outer side walls of the opposite side walls of the inner shielding box 32 that bulge outwards.

[0041] In this embodiment, on the opposite side of the top bulge of the convex character, that is, the second power field effect transistor 36 and the second thermistor are fixedly installed on the side walls at the bottom of the convex character and are controlled by an external heating control circuit.

[0042] As Figure 2 shown, in one specific embodiment, the distance between the outer shielding box 31 and the inner shielding box 32 is greater than 1 mm.

[0043] In this embodiment, the distance between the outer shielding box 31 and the inner shielding box 32 is greater than 1 mm, that is, the height of the second heat-insulating bracket 33 is greater than 1 mm, to avoid insufficient distance between the bottom outer shielding box 31 and the inner shielding box 32. Moreover, the selected material has good heat insulation performance, can withstand high and low temperatures, and has a certain strength. Preferably, for example, cork sheets, glass sheets, rigid polyurethane foams, etc. The second heat-insulating bracket 33 is fixed to the inner and outer shielding boxes by adhesive. This structure can not only reduce heat conduction, but also has relatively high structural strength, and is simple to install and manufacture.

[0044] In one specific embodiment, a quarter-wave plate 37 and a light-reducing plate 38 are arranged on the light incident side of the outer shielding box 31, and a photodiode 39 is arranged on the light exit side of the outer shielding box 31.

[0045] In this embodiment, the quarter-wave plate 37 is adhesively bonded to the outer side of the light incident hole of the outer shielding box 31, the light-reducing plate 38 is adhesively bonded to the inner side, and the photodiode 39 is adhesively bonded at the light exit hole of the outer shielding box 31 for reception.

[0046] In one specific embodiment, the outer shielding box 31 is a square box, the first thermistor 13 and the second thermistor are both NTC thermistors, the material of the alkali metal gas chamber 34 is glass, and the coil 35, the alkali metal gas chamber 34 and the inner wall gap of the inner shielding box 32 are filled with thermal conductive glue.

[0047] In one specific embodiment, the collimating lens assembly 20 includes a lens bracket and a collimating lens body. The lens bracket is in an inverted "U" shape and is fixedly arranged on the mounting substrate 40. The collimating lens body is installed inside the top of the lens bracket and matches the arc structure of the lens bracket.

[0048] In this embodiment, the collimating lens assembly 20 does not need temperature control. A mounting bracket for the collimating lens is made of a metal wire with an appropriate thickness (such as a 0.5-mm-diameter copper wire). The metal wire is in a "U" shape. The inner diameter of the middle arc is the same as the outer diameter of the lens. The length of the straight legs is within 10 mm. The arc is attached to the collimating lens, and a small amount of glue is applied at the contact position to bond them together. The pins are inserted into two straight-through pad holes reserved on the mounting substrate 40. The distance between the collimating lens and the mounting substrate 40 is not less than the distance between the VCSEL laser diode 11 and the mounting substrate 40. Then, the bracket metal wire is soldered to the pads on the mounting substrate 40. The mounting bracket can effectively support the small and light collimating lens. Moreover, after a certain external force is applied, the metal wire can undergo plastic deformation to adjust the position and attitude of the collimating lens, thereby finely adjusting the optical path 1. Finally, the optical axis of the collimating lens coincides with the line connecting the centers of the VCSEL laser diode 11 and the photodiode 39, and the VCSEL laser diode 11 is located at the focal point of the collimating lens, so that the effect of receiving the laser reaches the best. After the adjustment of the optical path 1 is completed, if it is desired to further increase the strength of the bracket, a curable colloid can be applied to the mounting bracket, and the strength will be enhanced after the colloid is cured.

[0049] The embodiments of the present application have been described above. The above description is exemplary and not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations are obvious to those of ordinary skill in the art in the technical field without departing from the scope and spirit of the described embodiments. The choice of terms used herein is intended to best explain the principles of the embodiments, the practical application, or the improvement of the technology in the market, or to enable other ordinary skill in the art in the technical field to understand the embodiments disclosed herein.

Claims

1. A physical system of a CPT atomic clock, characterized in that, it includes an installation substrate and a laser assembly, a collimating lens assembly, and a magnetic shielding shell assembly arranged in sequence on the installation substrate; an alkali metal gas chamber is arranged inside the magnetic shielding shell assembly, and light passing holes are opened on opposite sides of the magnetic shielding shell assembly; the optical axis of the laser assembly, the optical axis of the collimating lens assembly, and the light passing holes on the magnetic shielding shell assembly are coaxially arranged; the laser assembly includes a first adiabatic bracket, a first power field effect transistor, a VCSEL laser diode, and a first thermistor; the lower part of the first adiabatic bracket is fixedly connected to the installation substrate; the first power field effect transistor is arranged on the first adiabatic bracket; both the VCSEL laser diode and the first thermistor are fixed to the heat sink of the first power field effect transistor; the first power field effect transistor is a P-type power field effect transistor, the S pole of the first power field effect transistor is electrically connected to a power supply, the D pole of the first power field effect transistor is connected to the heat sink on the first power field effect transistor to make the D pole of the first power field effect transistor grounded; the negative pole of the VCSEL laser diode is electrically connected to the D pole of the first power field effect transistor and is grounded; one end of the first thermistor is electrically connected to the D pole of the first power field effect transistor and is grounded; the D pole of the first power field effect transistor, the negative pole of the VCSEL laser diode, and one end of the first thermistor are equipotential points.

2. The physical system of a CPT atomic clock according to claim 1, characterized in that, the VCSEL laser diode is adhesively fixed to the heat sink of the first power field effect transistor through a conductive adhesive.

3. The physical system of a CPT atomic clock according to claim 2, characterized in that, one end of the first thermistor is fixedly welded to the heat sink of the first power field effect transistor.

4. The physical system of a CPT atomic clock according to any one of claims 1-3, characterized in that, the magnetic shielding shell assembly includes an outer shielding box, a second adiabatic bracket, and an inner shielding box; the outer shielding box is fixedly arranged on the installation substrate; the second adiabatic bracket is in a "Π" shape and is fixed to the bottom inner wall of the outer shielding box; the inner shielding box is located inside the outer shielding box, the inner shielding box is fixed to the second adiabatic bracket, and the alkali metal gas chamber is placed inside the inner shielding box.

5. The physical system of a CPT atomic clock according to claim 4, characterized in that, the magnetic shielding shell assembly further includes a coil; the inner shielding box is in a "convex" shape and is horizontally placed on the second adiabatic bracket. Coils are respectively installed in the symmetrically arranged two side chambers of the inner shielding box, and the coils are coaxially arranged with the light passing holes; the alkali metal gas chamber is made of a cylindrical light-transmitting material, and the coils on both sides are respectively attached to the two light-passing surfaces of the alkali metal gas chamber.

6. The physical system of a CPT atomic clock according to claim 5, characterized in that, a second power field effect transistor and a second thermistor are fixedly installed outside the outwardly protruding opposite side walls of the inner shielding box.

7. The physical system of the CPT atomic clock according to claim 4, characterized in that, the distance between the outer shielding box and the inner shielding box is greater than 1 mm.

8. The physical system of the CPT atomic clock according to claim 6, characterized in that, a quarter-wave plate and a light-reducing filter are provided on the light-incident side of the outer shielding box; a photodiode is provided on the light-emitting side of the outer shielding box; the outer shielding box is a square box; both the first thermistor and the second thermistor are NTC thermistors; the material of the alkali metal gas cell is glass; a filling adhesive is filled in the gap between the coil, the alkali metal gas cell and the inner wall of the inner shielding box.

9. The physical system of the CPT atomic clock according to any one of claims 1-3, characterized in that, the collimating lens assembly includes a lens bracket and a collimating lens body; the lens bracket is in an inverted "U" shape and is fixedly arranged on the mounting substrate; the collimating lens body is installed inside the top of the lens bracket and matches the arc structure of the lens bracket.

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