A two-photon transition atomic beam fluorescence collection system

Abstract

The present application relates to a kind of two-photon transition atomic beam fluorescence collection systems, including gas chamber heating device, collimating laser light source, mirror and fluorescence collection unit;Collimating laser beam passes through atomic gas chamber after laser incidence window, is reflected by mirror at laser reflection window, and acts on atom in atomic gas chamber, forms two-photon transition, uses the reasonable combination of light collecting mirror and cylindrical lens with the surface type as parabolic mirror, and the fluorescence is reflected by parabolic mirror, and the collection space angle of atomic beam fluorescence is greatly improved relative to plane mirror again.By the reasonable combination of cylindrical lens, fluorescence beam is collected to photomultiplier with limited photosensitive area, can effectively enhance the detection of two-photon transition atomic beam fluorescence signal, to improve signal-to-noise ratio.

Description

Technical Field

[0001] This invention relates to the field of optoelectronics technology, and more specifically to a two-photon transition atomic beam fluorescence collection system. Background Technology

[0002] Thermo-atomic optical clocks based on two-photon transitions use alkali metal atoms encapsulated in atomic gas chambers as frequency references. They do not require complex and bulky laser cooling systems, have the characteristics of system simplicity, and have the potential for miniaturization.

[0003] To maximize the stability of hot atomic clocks, it is necessary to improve the collection efficiency of two-photon fluorescence. When a pair of co-current laser beams propagate collinearly in opposite directions within an atomic gas cell, they are absorbed by atoms, generating fluorescent photons. Since hot atoms are distributed throughout the entire atomic gas cell, the fluorescent photon source within the cell is a linear source collinear with the laser beams, and its length is equal to the length of the atomic gas cell in the laser propagation direction. The wavelength of two-photon fluorescence is approximately 420 nm, and photomultiplier tubes are typically used as the photoelectric conversion device. Because the fluorescence source to be collected is linear, and the area of ​​the photomultiplier tube used for collection is very limited, using a single parabolic mirror cannot achieve high-efficiency fluorescence collection. Summary of the Invention

[0004] Based on the above description, this invention provides a two-photon transition atomic beam fluorescence collection system to solve the technical problems of low collection efficiency and low signal-to-noise ratio in existing two-photon transition atomic beam fluorescence collection technologies. The technical solution of this invention to solve the above-mentioned technical problems is as follows:

[0005] A two-photon transition atomic beam fluorescence collection system includes a gas cell heating device, a collimating laser source, a mirror, and a fluorescence collection unit;

[0006] The gas chamber heating device has a vacuum chamber, in which an atomic gas chamber is horizontally arranged. At both ends of the gas chamber heating device, corresponding to the central axis of the atomic gas chamber, there are laser incident windows and laser reflection windows, respectively. On both sides of the gas chamber heating device, corresponding to the atomic gas chamber, there are fluorescence transmission windows and fluorescence collection transmission windows, respectively.

[0007] The collimated laser source and the reflector are respectively positioned corresponding to the laser incident window and the laser reflection window, and a polarizer is provided between the collimated laser source and the laser incident window;

[0008] The fluorescence collection unit includes a focusing mirror, a plano-concave cylindrical mirror, a plano-convex cylindrical mirror, a filter, and a photomultiplier tube. The focusing mirror is positioned on one side of the atomic gas cell, corresponding to the fluorescence transmission window. The focusing mirror is a parabolic concave mirror with its focal point located on the central axis of the atomic gas cell, and its axis is perpendicular to the central axis of the atomic gas cell. The plano-concave cylindrical mirror, plano-convex cylindrical mirror, filter, and photomultiplier tube are positioned on the other side of the atomic gas cell, corresponding to the fluorescence collection transmission window. The plano-concave cylindrical mirror, plano-convex cylindrical mirror, filter, and photomultiplier tube are distributed sequentially in a direction away from the atomic gas cell, and the distance between the plano-concave cylindrical mirror and the plano-convex cylindrical mirror is the difference in their focal lengths. The filter is a narrow-band filter, and the photomultiplier tube is used to collect the fluorescence of the atomic beam undergoing two-photon transitions.

[0009] Compared with the prior art, the technical solution of this application has the following beneficial technical effects:

[0010] The two-photon transition atomic beam fluorescence collection system provided in this application involves a collimated laser beam passing through an atomic gas cell via a laser incident window. The beam is then reflected by a mirror at a laser reflection window and interacts with the atoms in the atomic gas cell, forming a two-photon transition. A reasonable combination of a parabolic mirror and cylindrical mirrors is used, with the parabolic mirror reflecting the fluorescence, significantly increasing the collection angle of the atomic beam fluorescence compared to a plane mirror. Furthermore, a reasonable combination of cylindrical mirrors collects the fluorescence beam onto a photomultiplier tube with a limited photosensitive area, effectively enhancing the detection of the two-photon transition atomic beam fluorescence signal and thus improving the signal-to-noise ratio.

[0011] Based on the above technical solution, the present invention can be further improved as follows.

[0012] Furthermore, the polarizer is a Glan Taylor prism with a polarization splitting ratio of 100,000:1.

[0013] Furthermore, the gas chamber heating device uses a non-magnetic heating film to heat the atomic gas chamber.

[0014] Furthermore, a cylindrical atomic glass bubble is installed in the atomic gas chamber, the atomic glass bubble containing working atoms and filled with buffer gas.

[0015] Furthermore, the collimated laser beam emitted by the collimated laser source and the reflected light reflected by the mirror are combined to form an atomic beam fluorescence by two-photon transitions, which is a linear fluorescence beam.

[0016] Furthermore, the concave surface of the plano-concave cylindrical mirror is directly opposite the atomic gas cell, and its major axis is parallel to the central axis of the atomic gas cell.

[0017] Furthermore, the convex surface of the plano-convex cylindrical mirror is directly opposite the plano-concave cylindrical mirror, and its major axis is orthogonal to the major axis of the plano-concave cylindrical mirror.

[0018] Furthermore, the transmittance band of the narrowband filter is the corresponding two-photon transition fluorescence band, and its transmittance is better than 99.9%.

[0019] Furthermore, the light transmission bands of the plano-concave cylindrical mirror and the plano-convex cylindrical mirror are the corresponding two-photon transition fluorescence bands, and their transmittance is better than 99.9%.

[0020] Furthermore, the inner side of the parabolic surface of the reflector and the light-collecting lens is coated with a high-reflectivity film with a reflectivity better than 99.9%. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of a two-photon transition atomic beam fluorescence collection system provided in an embodiment of the present invention;

[0022] Figure 2 This is a schematic diagram of the combined structure of a plano-concave cylindrical mirror and a plano-convex cylindrical mirror in an embodiment of the present invention. Detailed Implementation

[0023] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.

[0024] Unless otherwise defined, 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 belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0025] It is understood that spatial relation terms such as "below," "under," "below," "below," "above," "above," etc., can be used here to describe the relationship between one element or feature shown in the figure and other elements or features. It should be understood that, in addition to the orientation shown in the figure, spatial relation terms also include different orientations of the device in use and operation. For example, if the device in the figure is flipped, the element or feature described as "below" or "below" of the other element or feature will be oriented "above" the other element or feature. Therefore, the exemplary terms "below" and "below" can include both upper and lower orientations. Furthermore, the device may also include other orientations (e.g., rotated 90° or other orientations), and the spatial descriptive terms used herein will be interpreted accordingly.

[0026] It should be noted that when one element is considered to be "connected" to another element, it can be directly connected to the other element or connected to the other element through an intermediary element. In the following embodiments, "connection" should be understood as "electrical connection," "communication connection," etc., if the connected circuits, modules, units, etc., have the transmission of electrical signals or data between them.

[0027] When used herein, the singular forms of “a,” “an,” and “the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising,” “including,” or “having,” etc., specify the presence of the stated feature, whole, step, operation, component, part, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof.

[0028] like Figures 1 to 2 As shown in the figure, this application provides a two-photon transition atomic beam fluorescence collection system, which includes a gas chamber heating device 10, a collimated laser source 20, a reflector 30 and a fluorescence collection unit 40.

[0029] The gas chamber heating device 10 has a vacuum chamber, and an atomic gas chamber 11 is horizontally arranged in the vacuum chamber. In this embodiment, the gas chamber heating device 10 uses a non-magnetic heating film to heat the atomic gas chamber 11, which can be heated to a set temperature range as needed and perform precise temperature control.

[0030] The atomic chamber 11 contains a cylindrical atomic glass bubble, which contains working atoms and is filled with buffer gas.

[0031] The gas chamber heating device 11 has a laser incident window and a laser reflection window at its two ends corresponding to the central axis of the atomic gas chamber 11, and the gas chamber heating device 10 has a fluorescence transmission window and a fluorescence collection transmission window at its two sides corresponding to the atomic gas chamber 11.

[0032] In this embodiment, XYZ are three coordinate axes that are perpendicular to each other in space, with the central axis of the atomic gas chamber 11 set according to the X-axis.

[0033] The collimated laser source 20 and the reflector 30 are respectively positioned corresponding to the laser incident window and the laser reflection window, and a polarizer 21 is provided between the collimated laser source 20 and the laser incident window.

[0034] In this embodiment, the collimated laser source is a line source, the light polarized by the polarizer 21 is linearly polarized light, and the atomic beam fluorescence formed by the two-photon transition of the collimated laser beam and the reflected light reflected by the mirror 30 is a linear fluorescence beam.

[0035] Preferably, the polarizer 21 is a Glan Taylor prism with a polarization splitting ratio of 100000:1.

[0036] In this embodiment, the fluorescence collection unit 40 includes a light-collecting mirror 41, a plano-concave cylindrical mirror 42, a plano-convex cylindrical mirror 43, a filter 44, and a photomultiplier tube 45.

[0037] The light-collecting mirror 41 is disposed on one side of the atomic gas cell 11, corresponding to the fluorescence transmission window. The light-collecting mirror 41 is a parabolic concave mirror, and its focal point is located on the central axis of the atomic gas cell 11. The axis of the light-collecting mirror 41 is perpendicular to the central axis of the atomic gas cell 11. The plano-concave cylindrical mirror 42, the plano-convex cylindrical mirror 43, the filter 44, and the photomultiplier tube 45 are disposed on the other side of the atomic gas cell 11, corresponding to the fluorescence collection and transmission window. The plano-concave cylindrical mirror 42, the plano-convex cylindrical mirror 43, the filter 44, and the photomultiplier tube 45 are distributed sequentially in a direction away from the atomic gas cell 11.

[0038] In this embodiment, the light-collecting lens 41, the plano-concave cylindrical lens 42, the plano-convex cylindrical lens 43, the filter 44, and the photomultiplier tube 45 are arranged along the Y-axis.

[0039] The distance between the plano-concave cylindrical mirror 42 and the plano-convex cylindrical mirror 43 is the difference in their focal lengths; the filter 44 is a narrow-band filter; and the photomultiplier tube 45 is used to collect the atomic beam fluorescence of two-photon transitions.

[0040] The inner side of the parabolic surface of the reflector 40 and the light-collecting mirror is coated with a high-reflectivity film with a reflectivity better than 99.9%.

[0041] To increase fluorescence collection efficiency, the concave surface of the plano-concave cylindrical mirror 42 is directly opposite the atomic gas cell 11, and its major axis is parallel to the central axis of the atomic gas cell 11; the convex surface of the plano-convex cylindrical mirror 43 is directly opposite the plano-concave cylindrical mirror 42, and its major axis is orthogonal to the major axis of the plano-concave cylindrical mirror 42.

[0042] More preferably, the light transmission bands of the plano-concave cylindrical mirror 42 and the plano-convex cylindrical mirror 43 are the corresponding two-photon transition fluorescence bands, and their transmittance is better than 99.9%. The light transmission band of the narrowband filter is the corresponding two-photon transition fluorescence band, and its transmittance is better than 99.9%.

[0043] The two-photon transition atomic beam fluorescence collection system provided in this application involves a collimated laser beam passing through the atomic gas cell 11 via the laser incident window. After being reflected by the reflector 30 at the laser reflection window, the beam acts on the hot atoms in the atomic gas cell, forming two-photon transition fluorescence. The parallel linear fluorescence beam transmitted through the fluorescence collection transmission window is focused in one direction by the plano-concave cylindrical mirror 42, and then focused in a direction orthogonal to it by the plano-convex cylindrical mirror 43. After passing through a high-quality narrowband filter 44, it is collected and focused onto the photomultiplier tube 45, thereby realizing the collection of two-photon transition atomic fluorescence.

[0044] This application utilizes a reasonable combination of a parabolic mirror and a cylindrical mirror. The parabolic mirror reflects the fluorescence, significantly increasing the collection angle of the atomic beam fluorescence compared to a plane mirror. Furthermore, the reasonable combination of cylindrical mirrors collects the fluorescence beam onto a photomultiplier tube with a limited photosensitive area, effectively enhancing the detection of the two-photon transition atomic beam fluorescence signal and thus improving the signal-to-noise ratio.

[0045] In a specific implementation scenario:

[0046] The 778nm laser beam emitted by the laser collimating source has a beam waist focal length of over 1 meter and a spot size of over 2mm. After passing through a GlanTeller prism, the polarization splitting ratio is 100,000:1. The collimated laser beam passes through the atomic gas chamber 11 through the laser incident window. The atomic gas chamber 11 is equipped with a gas chamber filled with... 87 A cylindrical glass bulb containing Rb and other buffer gases, and a laser beam reflected by a plane mirror 30 at the laser reflection window, acts in the glass bulb in the opposite direction and collinearly with the incident laser beam. 87 Rb atoms undergo two-photon transitions and emit a 420 nm linear atomic beam fluorescence into the atomic gas cell.

[0047] The focal point of the focusing lens 41 is located on the horizontal central axis of the atomic gas cell 11. The 420nm linear atomic fluorescence beam is collected and reflected by the focusing lens 41 through the fluorescence transmission window. The reflected fluorescence beam becomes a parallel beam and enters the plano-concave cylindrical mirror 42 through the fluorescence transmission collection window. The concave surface of the plano-concave cylindrical mirror 42 is directly opposite to the direction of the atomic gas cell 11, and its major axis is parallel to the central axis of the atomic gas cell 11. The convex surface of the plano-convex cylindrical mirror 43 is directly opposite to the plano-concave cylindrical mirror 42, and its major axis is orthogonal to the major axis of the plano-concave cylindrical mirror 42. The distance between the plano-concave cylindrical mirror 42 and the plano-convex cylindrical mirror 43 is the difference in their focal lengths. The parallel linear fluorescence beam from the fluorescence transmission collection window is converged in one direction after passing through the plano-concave cylindrical mirror 42, and then converged in a direction orthogonal to the plano-convex cylindrical mirror 43. After passing through a narrow-band filter, it is collected and converged to the photomultiplier tube, thereby realizing the collection of the current two-photon transition atomic fluorescence.

[0048] In this invention, in order to enhance87 The full interaction between Rb atoms and the laser beam enhances the two-photon transition probability. Throughout the operation, the temperature of the atomic gas chamber is maintained at 110 degrees Celsius, and precise temperature control technology is employed to minimize temperature fluctuations. The atomic gas chamber heating device uses a non-magnetic electric heating film to heat the atomic gas chamber, and the magnetic field generated by the non-magnetic heating film on the atomic gas chamber during heating should be suppressed to below 1 mGs.

[0049] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A two-photon transition atomic beam fluorescence collection system, characterized in that, Includes a gas chamber heating device, a collimated laser source, a reflector, and a fluorescence collection unit; The gas chamber heating device has a vacuum chamber, in which an atomic gas chamber is horizontally arranged. At both ends of the gas chamber heating device, corresponding to the central axis of the atomic gas chamber, there are laser incident windows and laser reflection windows, respectively. On both sides of the gas chamber heating device, corresponding to the atomic gas chamber, there are fluorescence transmission windows and fluorescence collection transmission windows, respectively. The collimated laser source and the reflector are respectively positioned corresponding to the laser incident window and the laser reflection window, and a polarizer is provided between the collimated laser source and the laser incident window; The fluorescence collection unit includes a focusing mirror, a plano-concave cylindrical mirror, a plano-convex cylindrical mirror, a filter, and a photomultiplier tube. The focusing mirror is positioned on one side of the atomic gas cell, corresponding to the fluorescence transmission window. The focusing mirror is a parabolic concave mirror with its focal point located on the central axis of the atomic gas cell, and its axis is perpendicular to the central axis of the atomic gas cell. The plano-concave cylindrical mirror, plano-convex cylindrical mirror, filter, and photomultiplier tube are positioned on the other side of the atomic gas cell, corresponding to the fluorescence collection transmission window. The plano-concave cylindrical mirror, plano-convex cylindrical mirror, filter, and photomultiplier tube are distributed sequentially in a direction away from the atomic gas cell, and the distance between the plano-concave cylindrical mirror and the plano-convex cylindrical mirror is the difference in their focal lengths. The filter is a narrow-band filter, and the photomultiplier tube is used to collect the fluorescence of the atomic beam undergoing two-photon transitions. The collimated laser beam emitted by the collimated laser source and the reflected light reflected by the mirror are combined to form an atomic beam fluorescence by two-photon transitions, which is a linear fluorescence beam. The concave surface of the plano-concave cylindrical mirror is directly opposite the atomic gas cell, and its major axis is parallel to the central axis of the atomic gas cell. The convex surface of the plano-convex cylindrical mirror is directly opposite the plano-concave cylindrical mirror, and its major axis is orthogonal to the major axis of the plano-concave cylindrical mirror.

2. The two-photon transition atomic beam fluorescence collection system according to claim 1, characterized in that, The polarizer is a Glan Taylor prism with a polarization splitting ratio of 100,000:

1.

3. The two-photon transition atomic beam fluorescence collection system according to claim 1, characterized in that, The gas chamber heating device uses a non-magnetic heating film to heat the atomic gas chamber.

4. The two-photon transition atomic beam fluorescence collection system according to claim 1, characterized in that, The atomic chamber is equipped with a cylindrical atomic glass bubble, which contains working atoms and is filled with a buffer gas.

5. The two-photon transition atomic beam fluorescence collection system according to claim 1, characterized in that, The transmittance band of the narrowband filter is the corresponding two-photon transition fluorescence band, and its transmittance is better than 99.9%.

6. The two-photon transition atomic beam fluorescence collection system according to claim 1, characterized in that, The light transmission bands of the plano-concave cylindrical mirror and the plano-convex cylindrical mirror are the corresponding two-photon transition fluorescence bands, and their transmittance is better than 99.9%.

7. The two-photon transition atomic beam fluorescence collection system according to claim 1, characterized in that, The inner side of the parabolic surface of the reflector and the light-collecting mirror is coated with a high-reflectivity film with a reflectivity better than 99.9%.

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