A small magneto-optical trap modulated by a single laser

Abstract

A single-laser modulated small magneto-optical trap (MOT) comprises a laser. The main laser emitted by the laser is split and reflected to form a first cooling beam, a second cooling beam, a third cooling beam, and a feedback beam. The cooling beams form a MOT optical path in which six beams are emitted in pairs and converge at a point within a vacuum chamber. The MOT is formed under the influence of a gradient static magnetic field formed by a first magnetic field coil and a second magnetic field coil. The feedback beam passes through a rubidium vapor chamber and is converted into re-pumping light through a photoelectric probe, a modem, a frequency-locked controller, and an electro-optical modulator. The laser combines the re-pumping light with the generated main laser beam. The device features a low-complexity laser optical path, low cost, and high precision. The vacuum glass chamber has low scattering, high transparency, a low thermal expansion coefficient, and good vacuum sealing, providing excellent optical performance and stability while reducing the effects of magnetic field interference and thermal expansion.

Description

Technical Field

[0001] The invention belongs to the technical field of quantum precision measurement, and in particular relates to a single laser modulated small magneto-optical trap. Background Art

[0002] Quantum precision measurement often requires ultracold atom technology, which cools atomic gases to extremely low temperatures, close to absolute zero, to amplify quantum effects. This effect is primarily due to the slow motion and stable distribution of atoms at low temperatures, the high fineness of atomic spectra, and the pronounced quantum effects. This makes it ideally suited for high-precision measurement applications. Existing technologies, such as cold atomic clocks, cold atom gravimeters and gravity gradiometers, and cold atom gyroscopes, based on cold atom matter-wave interferometry, have already reached industrialization.

[0003] Magneto-optical trap (MOT) technology is often used in laser cooling and trapping to provide atomic sources for quantum precision measurement instruments. According to the Zeeman effect, the energy level of the magnon is split into ΔE=μ B m J g J B0Z, the two lasers are transmitted along the Z axis, where σ + and σ - When the laser frequency is negatively detuned, the laser frequency at Z>0 is closer to m due to the Doppler effect. J =0→m J = -1 transition frequency, more absorption σ - The atom will be affected by the restoring force pointing to the origin of the coordinate system: Similarly, at Z<0, the laser frequency is closer to m due to the Doppler effect. J =0→m J = -1, more absorbed photons will also be subject to a restoring force directed toward the origin. All atoms are therefore subject to a restoring force directed toward the center, and the closer to the origin, the greater the detuning and the smaller the scattering force, similar to a parabolic potential well. The magnetic field provided by the Helmholtz coil and a pair of special circularly polarized light fields can provide a force that is not only related to velocity but also to position, thereby achieving the cooling and trapping of atoms. At the same time, to achieve the cooling cycle of atomic absorption of cooling light and spontaneous emission, optical pumping effects are required to achieve light transmission and modulation. Therefore, a magneto-optical trap system typically requires two or more lasers to emit two different lasers: one laser to provide cooling light, and the other to provide re-pumping light.

[0004] As the demand for quantum precision measurement instruments in dynamic environments continues to grow, technical personnel are placing higher demands on product size, weight, stability, and reliability. However, the complexity of traditional magneto-optical trap systems in terms of optics and vacuum systems can introduce various instabilities to the instruments.

[0005] The invention, with authorization publication number CN 100464208 C, discloses a single-beam magneto-optical trap system. Its design utilizes two lasers: one to provide cooling light for atoms and the magneto-optical trap, and the other to provide a re-pumping light source. The metallic vacuum cavity design may introduce magnetic field interference, affecting the magnetic field distribution within the magneto-optical trap and leading to performance degradation or instability. Furthermore, the laser beam may reflect off the titanium surface, causing beam deviation or loss of interference, impacting the performance and accuracy of the magneto-optical trap.

[0006] Patent publication number CN 116230287 A discloses a laser system and method for a two-color magneto-optical trap of rubidium atoms. This laser system also includes two lasers and a tapered amplifier. Its design fails to take into account the requirements and characteristics of precision cold atom measurements, resulting in significant deficiencies in the magneto-optical trap system. First, the use of two lasers increases system complexity, requiring more complex optical and electronic control systems to precisely control the frequency, phase, and power of the two lasers. Second, the use of two lasers also increases system cost. Beyond the cost of the additional lasers themselves, additional optical components, control electronics, and stability measures are required, potentially increasing system construction and maintenance costs.

[0007] Therefore, in order to meet the industrial application needs of quantum precision measurement instruments and improve the stability and reliability of quantum precision measurement instruments, it is urgently necessary to reduce the volume and weight of the instrument based on the existing cold atom capture device. A new type of magneto-optical trap with compact structure, small size, light weight, low power consumption and reliable performance is needed. Summary of the Invention

[0008] In view of the above problems, the present invention discloses a single laser modulated small magneto-optical trap.

[0009] The single-laser modulated small magneto-optical trap includes a laser light path mounting box, a laser is provided on the top of the laser light path mounting box, and an optical fiber amplification module, a temperature control module, and a wavelength conversion module are provided inside the laser. The laser is connected to an optical fiber collimator via an optical fiber, and the optical fiber collimator emits a main laser. The main laser passes through a first half glass slide and arrives at a first polarization beam splitter. The first polarization beam splitter splits the main laser into a first light beam and a second light beam. The first light beam maintains the direction of the main laser and is emitted, passes through the second half glass slide and arrives at the second polarization beam splitter. The second light beam passes through the third half glass slide and arrives at the third polarization beam splitter. The first half glass slide, the second half glass slide, and the third half glass slide play a role in controlling the ratio of the intensities of different light beams.

[0010] The second polarization beam splitter splits the first light beam into a first cooling beam and a second cooling beam; the first cooling beam is emitted while maintaining the direction of the first light beam, and sequentially passes through the first magnetic field coil, the vacuum cavity, and the second magnetic field coil before arriving at the first reflector; the first magnetic field coil and the second magnetic field coil are both reverse Helmholtz coils, and are fixed to both sides of the vacuum cavity on the laser optical path mounting box through a coil frame; the first cooling beam is perpendicular to the first reflector; the second cooling beam arrives at the second reflector, is reflected by the second reflector, passes through the vacuum cavity, and arrives at the third reflector, and the second cooling beam is perpendicular to the third reflector; the third polarization beam splitter splits the second light beam into a third cooling beam and a feedback beam; the third cooling beam passes through the vacuum cavity after being reflected by the fourth reflector, and arrives at the fifth reflector, and the third cooling beam is perpendicular to the fifth reflector; the first cooling beam, the second cooling beam, and the third cooling beam all pass through the same point in the vacuum cavity;

[0011] The feedback beam maintains the direction of the third cooling beam and reaches the sixth reflector. After being reflected by the sixth reflector, the feedback beam passes through the rubidium vapor chamber and is reflected by the seventh reflector and the eighth reflector to reach the photoelectric probe. The photoelectric probe converts the feedback beam into a digital signal, and the photoelectric probe transmits the digital signal to the modem through the radio frequency coaxial cable. The modem converts the digital signal into an analog signal and transmits the analog signal to the frequency locking controller through the radio frequency coaxial cable. The frequency locking controller performs high-frequency locking according to the analog signal to generate frequency-locked light, and the frequency-locked light is transmitted to the electro-optical modulator through the optical fiber. The electro-optical modulator modulates and frequency-shifts the frequency-locked light to convert the frequency-locked light into re-pumping light. The electro-optical modulator transmits the re-pumping light to the laser through the optical fiber, and the laser combines the re-pumping light with the main laser beam.

[0012] More specifically, the vacuum cavity is a hollow cuboid formed by bonding six rectangular glass sheets; the edges of the glass sheets are bonded by optical adhesive and indium wire; and the surfaces of the glass sheets are coated with a 0-degree anti-reflection film.

[0013] More specifically, the wavelength conversion module converts the central wavelength of the main laser to a fixed value of 780 nm.

[0014] More specifically, the locking frequency of the frequency-locked controller is 384228103.20 MHz; the frequency shift of the electro-optical modulator is 6423.09 MHz; and the frequency of the re-pumping light is 384234526.29 MHz.

[0015] More specifically, the magnetic field strength formed between the first magnetic field coil and the second magnetic field coil is 10 G / cm.

[0016] The working steps of the present invention include:

[0017] 1. The laser generates laser light, and the fiber amplifier module amplifies the laser light power to generate a main laser beam that meets the power requirements of the cooling light and re-pumping light. The temperature control module in the laser controls the main laser beam, and the wavelength conversion module in the laser converts the wavelength of the main laser beam to 780nm. The laser emits a 780nm beam that enters the optical path through the fiber collimator, splitting the main laser light into the first cooling beam, the second cooling beam, the third cooling beam, and the feedback beam; the feedback beam passes through the rubidium vapor chamber and is reflected by the reflector to the vacuum probe, which converts the scanned optical signal into an electrical signal. , use an electro-optical modulator to calculate and modulate the frequency shift, use an RF coaxial cable to connect to the frequency locking controller for high-speed frequency locking, lock the re-pump light, use an RF coaxial cable to connect to the modulation and demodulation board for signal conversion, and the signal is fed back to the laser through the RF coaxial cable. In this way, the light emitted from the laser contains two components, cooling light and re-pumping light; the first cooling beam, the second cooling beam, and the third cooling beam are reflected to form six beams of light that are emitted in pairs and intersect at a point in the vacuum cavity. The magneto-optical trap optical path forms a magneto-optical trap under the action of the gradient static magnetic field formed by the first magnetic field coil and the second magnetic field coil, and the magnetic field intensity at the intersection of the cooling beams is 0.

[0018] 2. An external ion pump evacuates the vacuum chamber. At this point, the atoms at the center of the magneto-optical trap experience Zeeman splitting of their magnetic energy levels under the influence of the magnetic field. Simultaneously, optical pumping is continuously achieved under the action of re-pumping light, allowing the cooling process to be repeated multiple times, ultimately achieving the goal of cooling the atoms and completing the rapid loading of low-temperature cold atomic clusters.

[0019] Compared with the existing technology, the beneficial effects of the present invention are: the present invention is a miniaturized magneto-optical trap based on single laser modulation, which uses only one laser to generate two laser beams of frequencies for atomic cooling and trapping, thereby realizing the preparation and observation of cold atoms; the single laser design of the laser optical path reduces the complexity of the laser optical path, reduces the laser cost, and provides a more flexible, precise and stable means of cold atom preparation and manipulation; the vacuum glass cavity has low scattering, high transparency, low thermal expansion coefficient and good vacuum sealing, which can provide better optical performance and stability, while reducing the influence of magnetic field interference and thermal expansion. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a structural diagram of a single laser modulated small magneto-optical trap of the present invention. DETAILED DESCRIPTION

[0021] The following describes the specific implementation of the embodiment of the present invention in detail with reference to the accompanying drawings. It should be understood that the specific implementation described herein is only used to illustrate and explain the embodiment of the present invention and is not used to limit the embodiment of the present invention.

[0022] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and 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 should not be understood as limiting the present invention.

[0023] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0024] In the present invention, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection, or communication; direct connection or indirect connection through an intermediate medium; internal communication between two elements or interaction between two elements, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0025] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0026] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0027] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with exemplary embodiments.

[0028] The single-laser modulated small magneto-optical trap includes a laser light path mounting box, with a laser 1 provided on the top of the laser light path mounting box. The laser 1 is internally provided with an optical fiber amplification module, a temperature control module, and a wavelength conversion module. The laser 1 is connected to an optical fiber collimator 2 through an optical fiber. The optical fiber collimator 2 emits a main laser, which passes through a first half glass slide 3 and reaches a first polarization beam splitter 4. The first polarization beam splitter 4 splits the main laser into a first beam and a second beam. The first beam is emitted while maintaining the direction of the main laser, passes through a second half glass slide 5, and reaches a second polarization beam splitter 6. The second beam passes through a third half glass slide 8 and reaches a third polarization beam splitter 9. The first half glass slide 3, the second half glass slide 5, and the third half glass slide 8 play a role in controlling the intensity ratio of different beams.

[0029] The second polarization beam splitter 6 splits the first light beam into a first cooling beam and a second cooling beam; the first cooling beam maintains the direction of the first light beam and is emitted, and passes through the first magnetic field coil 23, the vacuum cavity 22, and the second magnetic field coil 24 in sequence before arriving at the first reflector 21; the first magnetic field coil 23 and the second magnetic field coil 24 are both reverse Helmholtz coils, and are fixed to the two sides of the vacuum cavity 22 on the laser light path mounting box through coil frames; the first cooling beam is perpendicular to the first reflector 21; the second cooling beam arrives at the second reflector 7, is reflected by the second reflector 7 and passes through the vacuum cavity before arriving at the third reflector 20, and the second cooling beam is perpendicular to the third reflector 20; the third polarization beam splitter 9 splits the second light beam into a third cooling beam and a feedback beam; the third cooling beam passes through the vacuum cavity 22 after being reflected by the fourth reflector 18 and arrives at the fifth reflector 19, and the third cooling beam is perpendicular to the fifth reflector 19; the first cooling beam, the second cooling beam and the third cooling beam all pass through the same point in the vacuum cavity 22;

[0030] The feedback beam maintains the direction of the third cooling beam and reaches the sixth reflector 10. After being reflected by the sixth reflector 10, the feedback beam passes through the rubidium vapor chamber 11 and is reflected by the seventh reflector 12 and the eighth reflector 13 to reach the photoelectric probe 141; the photoelectric probe 4 converts the feedback beam into a digital signal, and the photoelectric probe 14 transmits the digital signal to the modem 15 through the radio frequency coaxial cable; the modem 15 converts the digital signal into an analog signal, and transmits the analog signal to the frequency locking controller 16 through the radio frequency coaxial cable. The frequency locking controller 16 performs high-frequency locking according to the analog signal to generate frequency-locked light, and the frequency-locked light is transmitted to the electro-optical modulator 17 through the optical fiber; the electro-optical modulator 17 modulates and frequency-shifts the frequency-locked light to convert the frequency-locked light into re-pumping light; the electro-optical modulator 17 transmits the re-pumping light to the laser 1 through the optical fiber, and the laser combines the re-pumping light with the main laser beam.

[0031] In some embodiments, the vacuum chamber is a hollow cuboid formed by gluing six rectangular glass sheets together; the edges of the glass sheets are glued together by optical glue and indium wire; and the surface of the glass sheets is coated with a 0-degree anti-reflection film.

[0032] More specifically, the wavelength conversion module converts the central wavelength of the main laser to a fixed 780 nm; the locking frequency of the frequency-locked controller is 384228103.20 MHz; the shift frequency of the electro-optical modulator is 6423.09 MHz, and the frequency of the re-pump light is 384234526.29 MHz.

[0033] More specifically, the magnetic field strength formed between the first magnetic field coil and the second magnetic field coil is 10 G / cm.

[0034] The working steps of the present invention include:

[0035] 1. The laser generates the main laser, and the fiber amplifier module amplifies the laser light power to generate a main laser beam that meets the power requirements of the cooling light and re-pumping light. The temperature control module in the laser controls the main laser beam, and the wavelength conversion module in the laser converts the wavelength of the main laser beam to 780nm. The laser emits a 780nm beam that enters the optical path through the fiber collimator, splitting the main laser light into the first cooling beam, the second cooling beam, the third cooling beam, and the feedback beam; the feedback beam passes through the rubidium vapor chamber and is reflected by the reflector to the vacuum probe, which converts the scanned optical signal into an electrical signal. , use an electro-optical modulator to calculate and modulate the frequency shift, use an RF coaxial cable to connect to the frequency locking controller for high-speed frequency locking, lock the re-pump light, use an RF coaxial cable to connect to the modulation and demodulation board for signal conversion, and the signal is fed back to the laser through the RF coaxial cable. In this way, the light emitted from the laser contains two components, cooling light and re-pumping light; the first cooling beam, the second cooling beam, and the third cooling beam are reflected to form six beams of light that are emitted in pairs and intersect at a point in the vacuum cavity. The magneto-optical trap optical path forms a magneto-optical trap under the action of the gradient static magnetic field formed by the first magnetic field coil and the second magnetic field coil, and the magnetic field intensity at the intersection of the cooling beams is 0.

[0036] 2. An external ion pump evacuates the vacuum chamber. At this point, the atoms at the center of the magneto-optical trap experience Zeeman splitting of their magnetic energy levels under the influence of the magnetic field. Simultaneously, optical pumping is continuously achieved under the action of re-pumping light, allowing the cooling process to be repeated multiple times, ultimately achieving the goal of cooling the atoms and completing the rapid loading of low-temperature cold atomic clusters.

[0037] Compared with the existing technology, the beneficial effects of the present invention are: the laser optical path of the single laser design reduces the complexity of the laser optical path, reduces the laser cost, and provides a more flexible, precise and stable means of cold atom preparation and manipulation; the vacuum glass cavity has low scattering, high transparency, low thermal expansion coefficient and good vacuum sealing, which can provide better optical performance and stability, while reducing the influence of magnetic field interference and thermal expansion.

Claims

1. A single-laser modulated small magneto-optical trap, characterized by: The laser light path installation box includes a laser light path installation box, a laser light path installation box top is provided, and the laser light path installation box is provided with an optical fiber amplification module, a temperature control module and a wavelength conversion module inside. The laser light is connected to the optical fiber collimator via an optical fiber, and the optical fiber collimator emits a main laser light, which passes through the first half glass slide and arrives at the first polarization beam splitter. The first polarization beam splitter splits the main laser light into a first beam and a second beam. The first beam maintains the direction of the main laser light and is emitted, passes through the second half glass slide and arrives at the second polarization beam splitter. The second beam passes through the third half glass slide and arrives at the third polarization beam splitter. The second polarization beam splitter splits the first light beam into a first cooling beam and a second cooling beam; the first cooling beam maintains the direction of the first beam and is emitted, and passes through the first magnetic field coil, the vacuum cavity, and the second magnetic field coil in sequence before arriving at the first reflector; the first cooling beam is perpendicular to the first reflector; the second cooling beam arrives at the second reflector, is reflected by the second reflector and passes through the vacuum cavity before arriving at the third reflector, and the second cooling beam is perpendicular to the third reflector; the third polarization beam splitter splits the second light beam into a third cooling beam and a feedback beam; the third cooling beam passes through the vacuum cavity after being reflected by the fourth reflector and arrives at the fifth reflector, and the third cooling beam is perpendicular to the fifth reflector; after reflection, the first cooling beam, the second cooling beam, and the third cooling beam form six beams of magneto-optical trap optical paths that are two-to-two and intersect at a point inside the vacuum cavity, and form a magneto-optical trap under the action of the gradient static magnetic field formed by the first magnetic field coil and the second magnetic field coil, and the magnetic field intensity at the intersection point of the cooling beams is 0; The feedback light beam maintains the direction of the second light beam and reaches the sixth reflector. After being reflected by the sixth reflector, the feedback light beam passes through the rubidium vapor chamber and is further reflected by the seventh and eighth reflectors to reach the photoelectric probe. The photoelectric probe converts the feedback light beam into a digital signal, and the photoelectric probe transmits the digital signal to the modem via a radio frequency coaxial cable. The modem converts the digital signal into an analog signal and transmits the analog signal to the frequency-locking controller via a radio frequency coaxial cable. The frequency-locking controller performs high-frequency locking based on the analog signal to generate frequency-locked light, which is then transmitted to the electro-optical modulator via optical fiber. The electro-optical modulator modulates and frequency-shifts the frequency-locked light, converting it into re-pumping light. The electro-optical modulator transmits the re-pumping light to the laser via optical fiber, and the laser combines the re-pumping light with the main laser beam.

2. A single-laser modulated miniature magneto-optical trap according to claim 1, characterized in that: The vacuum cavity is a hollow cuboid formed by bonding six rectangular glass sheets; the edges of the glass sheets are bonded by optical adhesive and indium wire; and the surfaces of the glass sheets are coated with a 0-degree anti-reflection film.

3. A single-laser modulated miniature magneto-optical trap according to claim 1, characterized in that: The wavelength conversion module converts the central wavelength of the main laser to a fixed wavelength of 780 nm.

4. A single-laser modulated miniature magneto-optical trap according to claim 2, characterized in that: The locking frequency of the frequency-locked controller is 384228103.20 MHz; the frequency shift of the electro-optical modulator is 6423.09 MHz; and the frequency of the re-pumping light is 384234526.29 MHz.

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