Double-beam small-angle Zeeman speed reducer

Abstract

The invention relates to the technical field of Zeeman speed reducers, in particular to a double-beam small-angle Zeeman speed reducer which comprises an atomic beam vacuum pipeline, a vacuum speed reduction area and a cooling light vacuum pipeline which are sequentially connected and communicated, an atomic reaction furnace is arranged in the atomic beam vacuum pipeline, and a vacuum optical window is installed at the rear end of the cooling light vacuum pipeline. The number of the cooling light vacuum pipelines is two, the two cooling light vacuum pipelines are symmetrically arranged in a splayed shape, and the included angle between the axis of each cooling light vacuum pipeline and the axis of the atomic beam vacuum pipeline is 3-30 degrees. Damage of the vacuum optical window can be reduced, the miniaturization application requirement can be met, the device is compact and small, and the speed reduction effect can meet the experiment requirement.

Description

Technical Field

[0001] The invention relates to the field of laser cooling technology, and in particular to a small double-beam small-angle Zeeman reducer which can effectively protect a vacuum optical window. Background Art

[0002] Zeeman slowdown is a key technology for obtaining cold atoms. It is widely used in laser deceleration of high-temperature hot atoms (several hundred meters per second) and can effectively reduce the speed of atoms to several meters per second. Zeeman slowdown plays an indispensable and key role in many quantum physics experiments, especially in quantum physics experiments of alkaline earth metals or rare earth metal atoms. Currently, miniaturization and compactness are important directions for the further development of cold atom technology. Among them, the miniaturized universal Zeeman slowdown with high performance, compact structure, reliability and durability, and no need for complex water cooling is the key core of the development and application of cold atom technology in the next stage.

[0003] Structurally, the cooling beam (i.e., laser beam) in the Zeeman reducer needs to be directed opposite to the hot atomic beam. The vacuum optical window is located opposite to the atomic beam. The cooling light enters the Zeeman reducer through the vacuum optical window. The vacuum deceleration area is covered outside the rear end of the atomic beam vacuum pipe to perform laser cooling on the atomic beam. In this direction, the energized coil is used to provide a suitable gradient magnetic field to compensate for the Doppler frequency shift caused by the change in atomic velocity, so that the cooling light frequency always resonates with the atomic transition energy level, thereby producing a continuous laser deceleration effect, which greatly reduces the speed of high-temperature hot atoms within a shorter distance.

[0004] However, due to multiple physical factors, including length limitations, it is difficult for the Zeeman reducer to decelerate all hot atomic beams, and it can only produce a deceleration effect for a very small proportion of the atomic beam. During the deceleration process, although most of the hot atoms will be lost, there are still some high-temperature atoms that have not been cooled by the two-dimensional vacuum deceleration area and will reach the oncoming vacuum optical window, and have complex physical and chemical reactions with the vacuum optical window. On the one hand, it reduces the permeability of the vacuum optical window, and on the other hand, it destroys the airtightness of the vacuum optical window, causing vacuum leakage and affecting the long-term stability of the system. In order to solve the above problems, the usual method is to extend the distance between the Zeeman reducer atomic deceleration outlet and the vacuum optical window, and introduce a 45° metal reflector in the vacuum system to prevent hot atoms from directly hitting the vacuum optical window. However, the above method greatly increases the length and complexity of the system. On the other hand, atoms can still interact with the metal reflector (evaporation or corrosion), affecting its optical performance. Summary of the invention

[0005] The present invention aims to provide a high-performance Zeeman reducer which can reduce vacuum optical window damage and meet the needs of miniaturized applications.

[0006] To this end, the technical solution adopted by the present invention is: a dual-beam small-angle Zeeman reducer, including an atomic beam vacuum pipe, a vacuum deceleration area, and a cooling light vacuum pipe that are connected and communicated in sequence, an atomic reactor is arranged in the atomic beam vacuum pipe, and a vacuum optical window is installed at the rear end of the cooling light vacuum pipe. There are two cooling light vacuum pipes in total, and they are arranged symmetrically in an eight-shaped shape, and the angle between the axis of each cooling light vacuum pipe and the axis of the atomic beam vacuum pipe is 3 to 30 degrees.

[0007] As a preferred embodiment of the above scheme, a capillary array tube is coaxially installed in the atomic beam vacuum pipeline, and a plurality of capillary tubes arranged in an array and parallel to the axis of the atomic beam vacuum pipeline are opened on the capillary array tube, so that the atomic beam in the atomic beam vacuum pipeline enters the vacuum deceleration area after passing through the capillary array tube. The collimation of the atomic beam is enhanced by placing the capillary array tube in the atomic beam vacuum pipeline.

[0008] More preferably, a baffle is provided on the side wall of the atomic beam vacuum pipe, and the baffle is provided behind the capillary array tube. The baffle is added on the basis of the capillary array tube, the capillary array tube is used to collimate the angular distribution of the atomic beam once, and the baffle is used to collimate the angular distribution of the atomic beam twice. At the same time, the baffle can also increase the collimation length, provide a more collimated atomic beam, and improve the Zeeman deceleration efficiency.

[0009] Further preferably, the atomic beam vacuum pipe, cooling light vacuum pipe and capillary array tube are all circular pipes, and the capillary pipes on the capillary array tube are in the form of a multi-circular ring array or a regular polygonal ring array, and the regular polygonal ring is at least a regular pentagonal ring.

[0010] Further preferably, the baffle is in a circular ring shape and is welded and fixed on the inner wall of the atomic beam vacuum pipe.

[0011] More preferably, the atomic beam vacuum pipe and the cooling light vacuum pipe are cast as one piece, and the vacuum deceleration area is covered outside the rear end of the atomic beam vacuum pipe.

[0012] More preferably, the angle between the axis of the cooling light vacuum pipe and the axis of the atomic beam vacuum pipe is 5-7°.

[0013] The present invention has the beneficial effects of: by symmetrically arranging two cooling light vacuum pipes arranged in an eight-shaped shape, the cooling light direction of the Zeeman reducer is changed so that it forms a small angle with the direction of the atomic beam, which can greatly reduce the direct impact of the atomic beam that is not decelerated by the vacuum deceleration area on the vacuum optical window, so as to solve the problem that the atomic beam causes great damage to the vacuum optical window, and even has the risk of vacuum leakage for atoms with strong metallic properties, which can significantly reduce the damage of the atomic beam to the vacuum optical window and extend the service life of the Zeeman reducer;

[0014] Since the damage of the atomic beam to the vacuum optical window can be reduced without increasing the length of the cooling light vacuum pipe, its volume is more compact and smaller than that of the traditional Zeeman reducer, and the deceleration effect can also meet the experimental requirements;

[0015] In addition, the present invention adopts a symmetrical small-angle dual cooling optical path structure, which can reduce the requirements for single-path laser power. Not all wavelength optical fiber output laser powers can meet the power requirements of the Zeeman reducer. And because the angle between the cooling light of the Zeeman reducer and the direction of the atomic beam is very small, the deceleration range is almost the same as that of the traditional single-path structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the principle of the dual-beam small-angle Zeeman reducer proposed in the present invention;.

[0017] Figure 2 It is a structural schematic diagram of the double-beam small-angle Zeeman reducer proposed in the present invention;.

[0018] Figure 3 is a schematic structural diagram of a capillary array tube in the present invention;

[0019] Figure 4 is a ratio curve of the atomic beam that can reach the optical window under the cooling light conditions of the Zeeman reducer at different angles in the embodiment of the present invention;

[0020] Figure 5 This is a diagram showing the deceleration effect of the Zeeman decelerator on the atomic beam in an embodiment of the present invention;

[0021] Among them, 1. Atomic beam vacuum pipeline, 2. Capillary array tube, 3. Vacuum deceleration area, 4. Cooling light vacuum pipeline, 5. Atomic reactor, 6. Vacuum optical window, 7. Baffle. DETAILED DESCRIPTION

[0022] The present invention is further described below in conjunction with the accompanying drawings, but the protection scope of the present invention is not limited to the following description.

[0023] like Figure 1 , Figure 3 As shown, a dual-beam small-angle Zeeman reducer is mainly composed of an atomic beam vacuum pipe 1, a vacuum deceleration area 3, and a cooling light vacuum pipe 4 which are connected and communicated in sequence. An atomic reactor 5 is arranged in the atomic beam vacuum pipe 1 for generating a hot atomic beam. The vacuum deceleration area 3 is used for laser cooling of the atomic beam. A vacuum optical window 6 is installed at the rear end of the cooling light vacuum pipe 4. The atomic beam vacuum pipe 1 is for the hot atomic beam to pass through. The cooling beam (i.e., the laser beam) enters the Zeeman reducer through the vacuum optical window 6. The above belongs to the prior art and will not be repeated here.

[0024] The difference is that there are two cooling light vacuum pipes 4, which are arranged symmetrically in an eight-shaped shape, and the angle between the axis of each cooling light vacuum pipe 4 and the axis of the atomic beam vacuum pipe 1 is 3 to 30 degrees, preferably 5 to 8 degrees. With the axis of the atomic beam vacuum pipe 1 as the central axis, the two cooling light vacuum pipes 4 are arranged symmetrically in an eight-shaped shape.

[0025] The rear end of each cooling light vacuum pipe 4 is fixed with a light-transmitting glass by M6 screws, serving as a vacuum optical window 6. Two cooling light beams enter the cooling light vacuum pipe 4 through the vacuum optical window 6, and after combining, they are directed against the atomic beam.

[0026] A capillary array tube 2 is installed in the atomic beam vacuum pipeline 1, and the capillary array tube 2 is coaxially arranged with the atomic beam vacuum pipeline 1. The capillary array tube 2 is provided with a plurality of capillary tubes arranged in an array and parallel to the axis of the atomic beam vacuum pipeline 1, so that the atomic beam in the atomic beam vacuum pipeline 1 flows through the capillary array tube 2 and enters the vacuum deceleration area 3. With the axis of the atomic beam vacuum pipeline 1 as the central axis, the capillary tubes on the capillary array tube 2 are completely symmetrically arranged.

[0027] Preferably, a baffle 7 is provided on the side wall of the atomic beam vacuum pipe 1, and the baffle 7 is arranged behind the capillary array tube 2. The baffle 7 can be annular, or two plates arranged opposite to each other up and down, and the baffle 7 is welded and fixed on the inner wall of the atomic beam vacuum pipe 1.

[0028] In addition, the atomic beam vacuum pipe 1, the cooling light vacuum pipe 4, and the capillary array tube 2 are all circular pipes, and the capillary pipes on the capillary array tube 2 are in the form of a multi-circular ring array or a regular polygonal ring array, and the regular polygonal ring is at least a regular pentagonal ring, and can also be a hexagonal ring or more.

[0029] The atomic beam vacuum pipe 1 and the cooling light vacuum pipe 4 are cast as one piece, and the vacuum deceleration area 3 is covered outside the rear end of the atomic beam vacuum pipe 1 .

[0030] The Zeeman reducer can perform laser cooling on hot atomic beams such as rubidium and ytterbium that have been heated by the atomic reactor to form a low-speed, high-flux atomic beam. The following describes the specific operation method for rubidium atoms using the dual-beam small-angle Zeeman reducer of the present invention in combination with an example:

[0031] The first step is to model the capillary array tube and obtain the angular distribution of the atomic beam after passing through the capillary array tube. By optimizing the relevant parameters such as the capillary tube length, diameter and atomic reactor heating temperature, an atomic beam with good collimation, that is, a narrow angular distribution, is obtained.

[0032] In the second step, the atomic beam vacuum pipeline and the cooling light vacuum pipeline are analyzed, and the model is simplified into a solid angle model. By changing the cooling light vacuum pipeline and related parameters such as the diameter, the ratio curve of the atomic beam that can reach the optical window under the conditions of the Zeeman reducer cooling light at different angles can be obtained, such as Figure 4 This embodiment determines the design parameters of a dual-beam small-angle Zeeman reducer suitable for rubidium atoms through calculation: the cooling light vacuum pipe is 50 cm long and 20 mm in diameter, and the angle between the cooling light vacuum pipe and the atomic beam vacuum pipe is 7°.

[0033] The third step is to establish a Monte Carlo experimental model to simulate the deceleration experimental process of rubidium atoms under the conditions of this embodiment and the magnetic field of the permanent magnet. In the above Monte Carlo experimental process, the magnetic field distribution is optimized by adjusting the position and magnetization intensity of the permanent magnet so that more atoms are decelerated.

[0034] The fourth step is to evaluate through simulation that the dual-beam small-angle Zeeman decelerator in the embodiment of the present invention will reduce the damage of the atomic beam to the optical window by about 4 times, and obtain a Zeeman deceleration efficiency of about 200%-400%, which can meet the experimental requirements, such as Figure 5 shown.

[0035] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A dual-beam small-angle Zeeman reducer, comprising an atomic beam vacuum pipeline (1), a vacuum deceleration area (3), and a cooling light vacuum pipeline (4) which are sequentially connected and communicated with each other, an atomic reactor (5) is arranged in the atomic beam vacuum pipeline (1), and a vacuum optical window (6) is installed at the rear end of the cooling light vacuum pipeline (4), characterized in that: There are two cooling light vacuum pipes (4) in total, which are symmetrically arranged in an eight-shaped shape, and the angle between the axis of each cooling light vacuum pipe (4) and the axis of the atomic beam vacuum pipe (1) is 3 to 30 degrees.

2. A dual-beam small-angle Zeeman reducer according to claim 1, characterized in that: A capillary array tube (2) is coaxially installed in the atomic beam vacuum pipeline (1), and a plurality of capillary tubes arranged in an array and parallel to the axis of the atomic beam vacuum pipeline (1) are provided on the capillary array tube (2), so that the atomic beam in the atomic beam vacuum pipeline (1) flows through the capillary array tube (2) and enters a vacuum deceleration area (3).

3. A dual-beam small-angle Zeeman reducer according to claim 2, characterized in that: A baffle (7) is arranged on the side wall of the atomic beam vacuum pipe (1), and the baffle (7) is arranged behind the capillary array tube (2).

4. A dual-beam small-angle Zeeman reducer according to claim 2 or 3, characterized in that: The atomic beam vacuum pipe (1), the cooling light vacuum pipe (4) and the capillary array tube (2) are all circular pipes. The capillary pipes on the capillary array tube (2) are in the form of a multi-circular ring array or a regular polygonal ring array. The regular polygonal ring is at least a regular pentagonal ring.

5. The dual-beam small-angle Zeeman reducer according to claim 3, characterized in that: The baffle (7) is in the shape of a circular ring and is welded and fixed on the inner wall of the atomic beam vacuum pipe (1).

6. The dual-beam small-angle Zeeman reducer according to claim 1, characterized in that: The atomic beam vacuum pipeline (1) and the cooling light vacuum pipeline (4) are cast as one piece, and the vacuum deceleration area (3) is covered outside the rear end of the atomic beam vacuum pipeline (1).

7. The dual-beam small-angle Zeeman reducer according to claim 1, characterized in that: The included angle between the axis of the cooling light vacuum pipe (4) and the axis of the atomic beam vacuum pipe (1) is 5 to 7 degrees.

Images