Single laser modulation small magneto-optical trap

Abstract

A single laser modulation small magneto-optical trap comprises a laser device, and main laser emitted by the laser device forms a first cooling light beam, a second cooling light beam, a third cooling light beam and a feedback light beam through beam splitting and reflection; the cooling light beams form six magneto-optical trap light paths, wherein every two of the six light beams are oppositely emitted and intersect at one point in the vacuum cavity, and a magneto-optical trap is formed under the action of a gradient static magnetic field formed by the first magnetic field coil and the second magnetic field coil. The feedback light beam penetrates through the rubidium steam chamber and is converted into re-pumping light through the photoelectric probe, the modem, the frequency locking controller and the electro-optical modulator in sequence, and the laser combines the re-pumping light and generated main laser. The device is low in complexity of a laser light path, low in cost and high in precision; the vacuum glass cavity is low in scattering, high in transparency, low in thermal expansion coefficient and good in vacuum sealing performance, good optical performance and stability can be provided, and meanwhile the influence of magnetic field interference and thermal expansion is reduced.

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] Ultracold atom technology is often used in quantum precision measurement. Ultracold atom technology cools atomic gas to extremely low temperatures, close to absolute zero, in order to amplify quantum effects. This effect is mainly due to the slow movement of atoms in low temperature, stable distribution, high atomic spectrum fineness, and obvious quantum effects. It is very suitable for high-precision measurement applications. In the existing technology, precision measurement instruments such as cold atomic clocks, cold atomic gravimeters and gravity gradient meters, and cold atomic gyroscopes based on cold atom matter wave interference have reached the industrial level.

[0003] The 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 energy level 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 - photon, the atom will be subject to a 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 transition frequency, more absorbed photons will also be subject to a restoring force pointing to the origin of the coordinate system. Therefore, all atoms are subject to a restoring force pointing to the center, and the closer to the origin, the greater the detuning and the smaller the scattering force, similar to a parabolic potential well. Through the magnetic field provided by the Helmholtz coil and a pair of special circularly polarized light fields, a force that is not only related to speed but also to position can be provided, thereby achieving the cooling and trapping of atoms. At the same time, to achieve the cycle of the cooling process of atoms absorbing cooling light and spontaneously emitting radiation, the optical pumping effect is required to realize the transmission and modulation of light. Therefore, the magneto-optical trap system usually requires two or more lasers to emit two different lasers; one laser is used to provide cooling light, and the other is used to provide re-pumping light.

[0004] As the application demand for quantum precision measurement instruments in dynamic environments continues to develop, technicians in this field have put forward higher requirements for the volume, weight, stability and reliability of products. However, the traditional magneto-optical trap system has certain complexity in terms of optics and vacuum systems, which will bring a variety of unstable factors to the instrument.

[0005] The invention with the authorization announcement number CN 100464208 C discloses a single-beam magneto-optical trap system. Its design uses two lasers, one for providing cooling light for cooling atoms and forming a magneto-optical trap, and the other for providing a re-pumping light source. The design of the vacuum cavity using metal materials may introduce magnetic field interference to affect the magnetic field distribution in the magneto-optical trap, resulting in a decrease in the performance of the magneto-optical trap or instability, and the laser beam may reflect from the metal titanium surface, resulting in the deviation of the beam or the loss of interference effect, affecting the performance and accuracy of the magneto-optical trap.

[0006] The invention with the authorization announcement number CN 116230287 A discloses a laser system and method for a two-color magneto-optical trap of rubidium atoms, which also includes two lasers and a tapered amplifier. Its design does not take into account the needs and characteristics of cold atom precision measurement, and the magneto-optical trap system has the following obvious deficiencies: first, the use of two lasers will increase the complexity of the system, and precise control of the frequency, phase and power of the two lasers requires a more complex optical and electronic control system; second, the use of two lasers will also increase the cost of the system. In addition to the cost of the additional lasers themselves, more optical components, control electronics and stability measures are required, which may increase the construction and maintenance costs of the system.

[0007] Therefore, in order to meet the needs of industrial application of quantum precision measurement instruments and improve the stability and reliability of quantum precision measurement instruments, it is urgently necessary to reduce the size 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 comprises a laser optical path installation box, a laser is arranged on the top of the laser optical path installation box, an optical fiber amplification module, a temperature control module and a wavelength conversion module are arranged inside the laser, the laser is connected to the optical fiber collimator through an optical fiber, the optical fiber collimator emits a main laser, the main laser passes through the first half glass slide and arrives at the 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 intensity ratio 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, 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; 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 light beam maintains the direction of the third cooling 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 then is reflected by the seventh reflector and the eighth reflector 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 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 locking light, and the frequency locking light is transmitted to the electro-optical modulator through the optical fiber; the electro-optical modulator modulates and frequency-shifts the frequency locking light, and converts the frequency locking 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.

[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 surface of the glass sheets is 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-optic modulator is 6423.09 MHz, and the frequency of the pump 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 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 convert its central wavelength to 780nm. The laser emits a 780nm beam that enters the optical path from 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-optic 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-pumping 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, so that the light emitted from the laser contains two components, cooling light and re-pumping light; the first cooling light beam, the second cooling light beam, and the third cooling light 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, and a magneto-optical trap is formed under the action of the gradient static magnetic field formed by the first magnetic field coil and the second magnetic field coil. The magnetic field intensity at the intersection of the cooling beams is 0.

[0018] 2. The external ion pump evacuates the vacuum chamber. At this time, the atoms in the center of the magneto-optical trap will undergo Zeeman splitting of their magnetic sub-energy levels under the action of the magnetic field. At the same time, optical pumping is continuously achieved under the action of the re-pumping light, so that the cooling process can be repeated many times, ultimately achieving the purpose of cooling the atoms and completing the rapid loading of low-temperature cold atomic groups.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention is a miniaturized magneto-optical trap based on single laser modulation, which uses only one laser to generate two frequency laser beams 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 It is a structural diagram of a single laser modulated small magneto-optical trap of the present invention. DETAILED DESCRIPTION

[0021] The specific implementation of the embodiment of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here 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 is to 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”, etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element 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] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0024] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection, an electrical connection, or communication with each other; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0025] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0026] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means 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 may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

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

[0028] The single-laser modulated small magneto-optical trap comprises a laser optical path installation box, a laser 1 is arranged on the top of the laser optical path installation box, an optical fiber amplification module, a temperature control module and a wavelength conversion module are arranged inside the laser 1, the laser 1 is connected to the optical fiber collimator 2 through an optical fiber, the optical fiber collimator 2 emits a main laser, the main laser passes through the first half glass slide 3 and then reaches the first polarization beam splitter 4, the first polarization beam splitter 4 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 5 and then reaches the second polarization beam splitter 6; the second light beam passes through the third half glass slide 8 and then reaches the 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 light 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 is emitted while maintaining the direction of the first light beam, and sequentially passes through the first magnetic field coil 23, the vacuum cavity 22, and the second magnetic field coil 24 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 both sides of the vacuum cavity 22 on the laser light path mounting box through a coil frame; 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 light beam maintains the direction of the third cooling light beam and reaches the sixth reflector 10. After being reflected by the sixth reflector 10, the feedback light beam passes through the rubidium vapor chamber 11 and then 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 light 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, and the frequency locking controller 16 performs high frequency locking according to the analog signal to generate frequency locking light, and the frequency locking light is transmitted to the electro-optical modulator 17 through the optical fiber; the electro-optical modulator 17 modulates and frequency-shifts the frequency locking light to convert the frequency locking 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.

[0031] In some embodiments, the vacuum cavity is a hollow cuboid formed by bonding six rectangular glass sheets; the edges of the glass sheets are bonded 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 780nm; the locking frequency of the frequency locking controller is 384228103.20MHz; the shift frequency of the electro-optic modulator is 6423.09MHz, and the frequency of the pump light is 384234526.29MHz.

[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 the main laser beam that meets the power requirements of the cooling light and the 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 convert its central wavelength to 780nm. The laser emits a 780nm beam that enters the optical path from 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-optic 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-pumping 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, so that the light emitted from the laser contains two components, cooling light and re-pumping light; the first cooling light beam, the second cooling light beam, and the third cooling light 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, and a magneto-optical trap is formed under the action of the gradient static magnetic field formed by the first magnetic field coil and the second magnetic field coil. The magnetic field intensity at the intersection of the cooling beams is 0.

[0036] 2. The external ion pump evacuates the vacuum chamber. At this time, the atoms in the center of the magneto-optical trap will undergo Zeeman splitting of their magnetic sub-energy levels under the action of the magnetic field. At the same time, optical pumping is continuously achieved under the action of the re-pumping light, so that the cooling process can be repeated many times, ultimately achieving the purpose of cooling the atoms and completing the rapid loading of low-temperature cold atomic groups.

[0037] Compared with the prior art, 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 in that: It comprises a laser light path installation box, a laser is arranged on the top of the laser light path installation box, an optical fiber amplification module, a temperature control module and a wavelength conversion module are arranged inside the laser, the laser is connected to an optical fiber collimator through an optical fiber, 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 a second half glass slide and arrives at a second polarization beam splitter; the second light beam passes through a third half glass slide and arrives at a 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 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 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 a magneto-optical trap optical path of six beams that are mutually irradiated and intersect at a point inside the vacuum cavity, and a magneto-optical trap is formed 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; The feedback light beam maintains the direction of the third cooling 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 then is reflected by the seventh reflector and the eighth reflector 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 through 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 according to the analog signal to generate frequency-locked light, which is transmitted to the electro-optical modulator via optical fiber. The electro-optical modulator modulates and frequency-shifts the frequency-locked light to convert 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 small 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 surface of the glass sheets is coated with a 0-degree anti-reflection film.

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

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