Flat cavity device based on diffusely reflected cooled atoms

Abstract

A flat cavity device based on diffuse reflection cooling atoms, comprising a flat vacuum cavity and an optical system. The present invention has the characteristics of lower complexity, higher robustness and higher controllability, and can obtain a quasi-two-dimensional distribution of cold atoms. The present invention has important application prospects and values in the research fields of atomic cooling and its applications such as microwave electric field detection, etc.

Description

Technical Field

[0001] The present invention belongs to the field of laser cooling of atoms, and particularly relates to a flat cavity device based on diffuse reflection cooling of atoms. Background Art

[0002] In 1979, Academician Wang Yuzhu proposed the idea of using a diffuse reflection cavity to generate a diffuse reflection light field to cool atoms at the Chengdu Optical Frequency Standard Conference. Subsequently, W. Ketterle et al. realized the cooling of sodium atoms using the diffuse reflection mechanism in 1992. Cooling atoms based on the diffuse reflection mechanism has no requirement for laser polarization and does not require an additional magnetic field, which greatly simplifies the experimental apparatus and reduces the experimental cost compared with common atomic cooling schemes such as magnetic traps and magneto-optical traps.

[0003] Different vacuum cavity structures and injection methods of cooling light have extremely important effects on the atomic distribution in the cavity. Therefore, the atomic distribution in the cavity can be adjusted by designing the structure of the vacuum cavity and the injection method of the diffuse reflection light field. Currently, the cavity structures for cooling atoms based on the diffuse reflection mechanism mainly include spherical, cylindrical, square, etc. Summary of the Invention

[0004] The purpose of the present invention is to provide a flat cavity device based on diffuse reflection cooling of atoms. The shape of the flat vacuum cavity device is close to two-dimensional, and a quasi-two-dimensional distribution of cold atoms can be obtained. This technology has important application prospects and values in research fields such as atomic cooling and its applications, such as microwave electric field detection.

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

[0006] A flat cavity device based on diffuse reflection cooling of atoms, characterized by comprising a flat vacuum cavity and an optical system.

[0007] The flat vacuum cavity mainly includes a flat cavity body, a quartz wafer, a quartz glass tube, a knife-edge flange, and a surface coating. The flat cavity body is composed of an upper plane, a lower plane, and side walls between the peripheries of the upper plane and the lower plane. A coating with extremely high diffuse reflectivity is evenly applied on the surfaces of the flat cavity body and the cylindrical quartz tube. A circumferential slit is opened on the diffuse reflection coating on the side wall of the flat cavity body. The notch on the side wall of the flat cavity body is connected to one end through-hole of the cylindrical quartz tube by the quartz wafer, and the other end of the cylindrical quartz tube is connected to a four-way or six-way device, etc., through the knife-edge flange to a vacuum system and an atomic source.

[0008] The described optical system includes cooling light, repumping light, and a detection device. The cooling light and the repumping light are first combined and then shaped into a combined beam with an elliptical shape. The longitudinal dimension of the spot of this combined beam is slightly smaller than the width of the slit. The combined beam is equally divided into multiple elliptical beams and symmetrically passes through the slit and enters the flat cavity body at a small downward or upward inclination angle (θ), forming a uniformly distributed diffuse reflection light field within the flat cavity body. The detection device includes a detection beam and a low-noise photodetector. The detection beam horizontally passes through the slit and the flat cavity and is incident on the low-noise photodetector located outside the flat cavity body to detect the cold atom signal within the flat cavity body.

[0009] The described flat cavity body is a rectangular flat quartz cavity, having obvious flat characteristics, that is, the dimensions in the X and Y directions are significantly larger than the dimension in the Z direction. In addition, this cavity can be extended from a rectangular flat cavity to a disc-shaped flat quartz cavity or a triangular flat quartz cavity.

[0010] The described flat cavity body is made of quartz glass, and there is a high diffuse reflectivity material outside the cavity. The cavity material can be extended to a metal material, that is, it can be a rectangular flat metal cavity, a disc-shaped flat metal cavity, or a triangular flat metal cavity.

[0011] The flat cavity body and the quartz glass tube are transitioned through an annular quartz thin sheet, which is used to reduce the stress generated between the flat cavity body and the quartz glass tube due to different local temperatures during the manufacturing process.

[0012] The optical system is controlled by timing. First, the cooling light and the repumping light are simultaneously turned on to cool the atoms in the cavity. The cooled atoms are affected by the flat cavity structure and the injection light field mode, and their distribution shows a quasi-two-dimensional sheet-like distribution. Subsequently, the cooling light and the repumping light are turned off and the detection light is turned on, and the cold atom signal is obtained through the photodetector.

[0013] The present invention has the following advantages:

[0014] 1. It has the advantages of other diffuse reflection cooling atom schemes. During the cooling process, there are no very strict requirements for the spatial position and polarization of the light beam, and no additional magnetic field is generated to affect the atomic energy levels and distribution.

[0015] 2. Compared with traditional diffuse reflection cooling, the present invention can obtain a quasi-two-dimensional atomic distribution, having obvious atomic distribution characteristics.

[0016] 3. According to different requirements of atomic morphology and distribution, the flat cavity structure can be expanded into a disc-shaped flat cavity, a triangular flat cavity, etc. The structure of the flat cavity is similar to that of some resonator configurations and can be further developed into a metal resonator, which has great expandability in applications.

[0017] The device of the present invention has the characteristics of relatively simple structure, high robustness and high controllability. The obtained cold atoms are in a quasi-two-dimensional distribution. This technology has important application prospects and values in research fields such as atomic cooling and its applications, such as microwave electric field detection. Brief Description of the Drawings

[0018] Figure 1 is an exploded view of the rectangular flat quartz vacuum cavity of the present invention

[0019] Figure 2 is a schematic diagram of laser cooling of a flat cavity including a diffuse reflection coating

[0020] Figure 3 is a schematic diagram of the combined beam incident on the flat cavity body at a small upward inclination angle

[0021] Figure 4 is the energy level transition of rubidium atoms corresponding to the laser frequency

[0022] Figure 5 is a timing diagram of atomic cooling

[0023] Figure 6 is a structural diagram of a triangular flat quartz vacuum cavity

[0024] In the figure: 1-1 is a knife-edge flange, 1-2 is a cylindrical quartz glass tube, 1-3 is the lower plane of the flat vacuum cavity, 1-4 is the side wall of the flat vacuum cavity, 1-5 is a through hole between the cylindrical quartz glass tube and the flat cavity body, 1-6 is a transition rectangular thin sheet between the quartz glass tube and the flat vacuum chamber, 1-7 is the upper plane of the flat vacuum chamber, 2-1 is a detection beam, 2-2, 2-5, 2-6 and 2-7 are elliptical beams after the cooling light and the repump light are combined, 2-3 is a diffuse reflection coating on the surface of the flat cavity body, 2-4 is a slit on the side wall surface of the flat cavity body without coating, 2-8 is the flat cavity body without surface diffuse reflection coating, 2-9 is a photodetector, and 3-1 is the incident direction of the combined beam. Detailed Embodiments

[0025] The present invention will be clearly and detailedly described below in conjunction with the embodiments and drawings of the present invention, but the protection scope of the present invention should not be limited thereby.

[0026] Please refer to Figure 1 、 Figure 2 、 Figure 3 , Figure 1It is an exploded view of the rectangular flat quartz vacuum chamber of the present invention. Figure 2 It is a schematic diagram of laser cooling of a flat chamber with a diffuse reflection coating. Figure 3 It is a schematic diagram of the combined beam incident on the flat chamber body at a small upward inclination angle. As can be seen from the figure, the flat chamber device of the present invention for cooling atoms based on diffuse reflection includes a flat vacuum chamber and an optical system.

[0027] The flat vacuum chamber mainly includes a flat chamber body 2-8, a quartz wafer 1-6, a quartz glass tube 1-2, a knife-edge flange 1-1, and a surface coating 2-3. The flat chamber body 2-8 is composed of an upper plane 1-7, a lower plane 1-3, and a side wall 1-4 located between the peripheries of the upper plane 1-7 and the lower plane 1-3. A coating 2-3 with extremely high diffuse reflectivity is evenly applied on the surfaces of the flat chamber body 2-8 and the cylindrical quartz tube 1-2. A circumferential slit 2-4 is opened on the diffuse reflection coating 2-3 of the side wall 1-4 of the flat chamber body 2-8; the notch of the side wall 1-4 of the flat chamber body 2-8 is connected to one end through-hole 1-5 of the cylindrical quartz tube 1-2 through a quartz wafer 1-6, and the other end of the cylindrical quartz tube 1-2 is connected to a four-way or six-way device through a knife-edge flange 1-1 to a vacuum system and an atomic source (not shown in the figure);

[0028] The optical system includes cooling light, repumping light, and a detection device. The cooling light and the repumping light are first combined and then shaped into a combined beam with an elliptical shape. The longitudinal dimension of the spot of the combined beam is slightly smaller than the width of the slit 2-4. The combined beam is equally divided into multiple elliptical beams 2-2, 2-5, 2-6, 2-7 and symmetrically passes through the slit 2-4 and enters the flat chamber body 2-8 at a small downward or upward inclination angle θ to form a uniformly distributed diffuse reflection light field in the flat chamber body 2-8; the detection device includes a detection beam 2-1 and a low-noise photodetector 2-9. The detection beam 2-1 horizontally passes through the slit 2-4 and the center of the flat chamber body 2-8 and is incident on the low-noise photodetector 2-9 located outside the flat chamber body 2-8 for detecting the cold atom signal in the flat chamber body 2-8.

[0029] Embodiment 1

[0030] See Figure 1 、 Figure 2, the flat cavity body 2-8 of this embodiment is a rectangular flat quartz cavity. The dimensions in the length and width directions of this rectangular flat quartz cavity are significantly larger than the dimension in the height direction. A rectangular quartz sheet 1-6 is used for transitional connection between one end of the rectangular flat quartz cavity and one end of the cylindrical quartz tube 1-2. The other end of the cylindrical quartz tube 1-2 is connected to a vacuum system and an atomic source (not shown in the figure) through a knife-edge flange 1-1 and devices such as a four-way or six-way connection;

[0031] See Figure 2 , a sufficiently thick highly diffuse reflection coating 2-3 is evenly applied on the surfaces of the flat cavity body 2-8 and the cylindrical quartz tube 1-2. A week of slits 2-4 are opened on the side of the diffuse reflection coating 2-3 of the flat cavity;

[0032] The optical system includes cooling light, repump light, and a detection device. The cooling light and the repump light are first combined and then shaped into a combined beam with an elliptical shape. The longitudinal dimension of the light spot of this combined beam is slightly smaller than the width of the slit 2-4. The combined beam is equally divided into four elliptical beams 2-2, 2-5, 2-6, and 2-7. These four elliptical beams symmetrically pass through the slit 2-4 and enter the flat cavity body 2-8 at a small downward (or upward) inclination angle θ (see Figure 3 ), and a uniformly distributed diffuse reflection light field is formed in the flat cavity body 2-8; see Figure 2 , the detection device includes a beam of detection light 2-1 and a low-noise photodetector 2-9. The detection light 2-1 horizontally passes through the slit 2-4 and the flat cavity body 2-8 and is incident on the low-noise photodetector 2-9 located outside the flat cavity body 2-8 for detecting the cold atom signal in the cavity.

[0033] See Figure 1 , the flat cavity body 2-8 is a cuboid-shaped quartz cavity, which is spliced by rectangular quartz glass. The cavity is in the shape of a flat cuboid, that is, the dimensions in the X and Y directions are significantly larger than the dimension in the Z direction. The side wall 1-4 of the vacuum cavity is sandwiched between the upper plane 1-7 and the lower plane 1-3, and the two short side walls are sandwiched between the long side walls.

[0034] The flat cavity body 2-8 can be extended to a disc-shaped flat quartz cavity, a triangular flat quartz cavity (see Figure 6 ); the flat cavity is not limited to a quartz cavity and can be extended to a metal cavity.

[0035] The transitional connection of the quartz sheet 1-6 is used to reduce the stress generated between the flat cavity body 2-8 and the quartz glass tube 1-2 due to different local temperatures during the manufacturing process.

[0036] A layer of diffuse reflection coating 2-3 with a thickness of about 2 mm is evenly applied to the surface of the flat cavity body 2-8. The diffuse reflectivity of this coating for 780 nm laser is greater than 98%. A slit 2-4 with a width of about 2 mm is opened in the side coating of the flat cavity body 2-8.

[0037] The optical system mainly includes cooling light, repumping light and probing light. The cooling light and the repumping light are first combined and then shaped into an elliptical shape. The longitudinal size of the light spot is smaller than the width of the slit 2-4 left by the diffuse reflection coating. The combined beam is equally divided into four combined beams 2-2, 2-5, 2-6, and 2-7 and symmetrically incident into the cavity. Please refer to Figure 3 , and the incident direction 3-1 of the combined beam has a small upward (or downward) inclination angle (θ).

[0038] The described probing light 2-1 passes horizontally through the center of the cavity and is incident on a low-noise photodetector 2-9 for detecting the absorption signal of atoms.

[0039] The laser frequency corresponds to the transition energy level of rubidium atoms. As Figure 4 shown, the cooling light frequency corresponds to the transition from 5S 1 / 2 , F = 2 to 5P 3 / 2 , F’ = 3 energy level transition and has a red detuning of about 20 MHz. The repumping light frequency corresponds to the transition from 5S 1 / 2 , F = 1 to 5P 3 / 2 , F’ = 2 energy level transition. The probing light frequency corresponds to the transition from 5S 1 / 2 , F = 2 to 5P 3 / 2 , F’ = 3 energy level transition.

[0040] The described timing mainly controls the optical frequency shift and the optical switch. As Figure 5 shown, the cooling stage of the cooling light and the repumping light is about 1 s. Subsequently, the cooling light and the repumping light are turned off and the probing light is turned on to obtain the cold atom signal through the phototube.

[0041] Embodiment 2

[0042] Please refer to Figure 6 , and the described flat vacuum cavity is a triangular flat cavity.

[0043] The device of the present invention has the characteristics of low complexity, high robustness and high controllability. The obtained cold atoms are in a quasi-two-dimensional distribution. This technology has important potential applications and values in research fields such as atomic cooling and its applications such as microwave electric field detection.

Claims

1. A flat cavity device based on diffuse reflection cooled atoms, characterized in that it includes a flat vacuum cavity and an optical system, the flat vacuum cavity mainly includes a flat cavity body (2-8), a quartz wafer (1-6), a cylindrical quartz tube (1-2), a knife-edge flange (1-1) and a surface coating (2-3). The flat cavity body (2-8) is composed of an upper plane (1-7), a lower plane (1-3), and a side wall (1-4) located between the peripheries of the upper plane (1-7) and the lower plane (1-3). A coating (2-3) with extremely high diffuse reflectivity is evenly applied on the surfaces of the flat cavity body (2-8) and the cylindrical quartz tube (1-2). A week of slits (2-4) are opened on the diffuse reflection coating (2-3) of the side wall (1-4) of the flat cavity body (2-8); the notch of the side wall (1-4) of the flat cavity body (2-8) is connected to one end through-hole (1-5) of the cylindrical quartz tube (1-2) through a quartz wafer (1-6). The other end of the cylindrical quartz tube (1-2) is connected to a four-way or six-way device through a knife-edge flange (1-1) to a vacuum system and an atomic source; the optical system includes cooling light, repumping light and a detection device. The cooling light and the repumping light are first combined and then shaped into a combined beam with an elliptical shape. The longitudinal dimension of the light spot of the combined beam is slightly smaller than the width of the slit (2-4). The combined beam is equally divided into multiple elliptical beams (2-2, 2-5, 2-6, 2-7) and symmetrically passes through the slit (2-4) and enters (3-1) into the flat cavity body (2-8) at a small downward or upward inclination angle (θ), forming a uniformly distributed diffuse reflection light field in the flat cavity body (2-8); the detection device includes a detection beam (2-1) and a low-noise photodetector (2-9). The detection beam (2-1) horizontally passes through the slit (2-4) and the flat cavity body (2-8) and enters the low-noise photodetector (2-9) located outside the flat cavity body (2-8) for detecting the cold atom signal in the flat cavity body (2-8).

2. The flat cavity device based on diffuse reflection cooled atoms according to claim 1, characterized in that, the flat cavity body (2-8) is a rectangular flat quartz cavity, a disc-shaped flat quartz cavity or a triangular flat quartz cavity, having obvious flat characteristics, that is, the dimensions in the X and Y directions are significantly larger than the dimension in the Z direction.

3. The flat cavity device based on diffuse reflection cooled atoms according to claim 1, characterized in that, the flat cavity body (2-8) is made of quartz glass material or metal material, and has a high diffuse reflectivity material outside the cavity.

4. The flat cavity device based on diffuse reflection cooled atoms according to claim 3, characterized in that, the flat cavity body (2-8) is a rectangular flat metal cavity, a disc-shaped flat metal cavity or a triangular flat metal cavity.

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