A fiber-coupled integrated Rydberg atom coupling laser frequency locking device and method

Abstract

The application provides a kind of optical fiber coupling integrated Rydberg atom coupling laser frequency locking device and method, device includes: probe laser, coupling laser, atom gas chamber filled with alkali metal atom, first fiber collimator, second fiber collimator, third fiber collimator, double color prism, photoelectric detector and proportional-integral-differential PID control circuit. Wherein, between probe laser and first fiber collimator, between coupling laser and second fiber collimator, and between third fiber collimator and photoelectric detector are connected by transmission fiber. In this way, not only can the precision and stability of laser frequency locking be improved. And, by the way of optical fiber coupling, optical integration is realized, i.e. probe laser, coupling laser, optical elements and photoelectric detector are integrated together, which can reduce the volume and weight of Rydberg atom coupling laser frequency locking device, and improve portability and maintainability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of laser frequency locking, and particularly relates to a fiber-coupled integrated Rydberg atom coupling laser frequency locking device and method. BACKGROUND

[0002] The laser frequency output by a laser often has a drift, especially when the environmental temperature, vibration condition, etc. change, the laser frequency changes more significantly. In some application scenarios with high requirements for laser frequency, the laser frequency output by the laser needs to be locked, i.e. frequency locking. The laser frequency locking usually refers to locking the laser frequency on a frequency reference which is not easily affected by the outside world and has high stability, such as atomic resonance absorption transition spectral line, etc.

[0003] The Rydberg atom laser frequency locking technology is one of the laser frequency locking technologies. Specifically, the Rydberg atom refers to an atom in a highly excited state, and the electron of the atom is excited to a state close to ionization, so the Rydberg atom has some special properties, such as long lifetime, large dipole moment and strong interaction, etc. The Rydberg atom laser frequency locking technology uses the special properties of the Rydberg atom to realize the locking of the laser frequency. Specifically, by interacting the laser beam with the Rydberg atom, the resonance transition of the Rydberg atom is used to detect the drift of the laser frequency, and the laser frequency is locked on the target value through a feedback mechanism. Since the Rydberg atom has the characteristics of high sensitivity and high resolution, the system can realize high-precision and high-stability laser frequency locking.

[0004] However, the Rydberg atom laser frequency locking device based on the Rydberg atom laser frequency locking technology has large volume and weight, and low portability and maintainability. SUMMARY

[0005] The technical problem to be solved by the present application is the problem of low portability and maintainability caused by the large volume of the existing Rydberg atom laser frequency locking device.

[0006] To solve the above technical problems, the present application provides a fiber-coupled integrated Rydberg atom coupling laser frequency locking device and method, which specifically adopts the following technical solutions:

[0007] In a first aspect, the present application provides a fiber-coupled integrated Rydberg atom coupling laser frequency locking device, comprising: a probe laser, a coupling laser, an atomic cell filled with alkali metal atoms, a first fiber collimator, a second fiber collimator, a third fiber collimator, a bichromatic prism, a photodetector, and a proportional-integral-derivative (PID) control circuit. The probe laser is connected to the first fiber collimator, the coupling laser is connected to the second fiber collimator, and the third fiber collimator is connected to the photodetector through transmission fibers. The coupling laser is connected to the PID control circuit, and the PID control circuit is connected to the photodetector through electrical wires. The probe laser is used to output a probe laser beam with a first frequency, which is associated with the intermediate state of the alkali metal atoms, and couple the probe laser beam into the transmission fiber. The probe laser beam is collimated by the first fiber collimator and enters the atomic cell, and is used to excite the alkali metal atoms to the intermediate state. The coupling laser is used to output a coupling laser beam with a second frequency, which is associated with the energy level difference from the intermediate state to the Rydberg state of the alkali metal atoms, and couple the coupling laser beam into the transmission fiber. The coupling laser beam is collimated by the second fiber collimator and the bichromatic prism and enters the atomic cell, and overlaps with the probe laser beam in the atomic cell. The coupling laser beam is used to excite the alkali metal atoms to the Rydberg state. When the alkali metal atoms are excited to the Rydberg state, the probe light beam passes through the atomic cell, the bichromatic prism, and the third fiber collimator, and is coupled into the transmission fiber. The transmission fiber transmits the probe light beam to the photodetector, which converts the probe light beam into a probe photo signal and outputs it to the PID control circuit. The PID control circuit processes the probe photo signal into a feedback signal and outputs it to the coupling laser. The coupling laser adjusts the second frequency according to the feedback signal to achieve frequency locking.

[0008] In this device, the interaction between the alkali metal atoms in the Rydberg state and the coupling laser with a specific frequency is used to achieve frequency locking. The overall design of the device is fiber-coupled integrated, which facilitates the transmission and control of the laser, and also improves the stability and anti-interference ability. The selection and layout of the transmission fiber ensure stable transmission and minimal loss of the laser. In addition, the fiber coupling technology also allows long-distance transmission of the laser, making the design of the Rydberg atom coupling laser frequency locking device more flexible and convenient. The excellent transmission characteristics of the fiber can ensure the stability and anti-interference ability of the laser signal during transmission, thereby improving the precision and stability of the laser frequency locking. Moreover, by integrating the probe laser, the coupling laser, the optical elements, and the detector together, the volume and weight of the Rydberg atom coupling laser frequency locking device can be greatly reduced, and the portability and maintainability can be improved.

[0009] With reference to the first aspect, in a possible implementation form of the first aspect, the PID control circuit is further configured to: perform frequency triangular wave scanning on the coupling laser to obtain the frequency of the coupling laser output coupling laser beam; and perform frequency modulation on the coupling laser output coupling laser beam.

[0010] With reference to the first aspect, in a possible implementation form of the first aspect, the PID control circuit is further configured to: demodulate the probe optical signal to obtain a frequency discrimination signal; and perform proportional, integral and differential control on the frequency discrimination signal to obtain the feedback signal, the feedback signal being used to represent the frequency error.

[0011] In this implementation form, the probe optical signal is processed by the PID control circuit to obtain the frequency discrimination signal. Further, the feedback signal is obtained according to the frequency discrimination signal. In this way, the frequency error can be accurately determined, and the accuracy of frequency locking of the coupling laser is improved.

[0012] With reference to the first aspect, in a possible implementation form of the first aspect, the alkali metal atom is one of: a potassium (K) atom, a rubidium (Rb) atom, and a cesium (Cs) atom. In the case where the alkali metal atom is the K atom, the first frequency corresponds to a D2 line of a saturated spectrum of the K atom, and the second frequency corresponds to an energy level difference from an intermediate state to a Rydberg atomic state of the K atom. In the case where the alkali metal atom is the Rb atom, the first frequency corresponds to a D2 line of a saturated spectrum of the Rb atom, and the second frequency corresponds to an energy level difference from an intermediate state to a Rydberg atomic state of the Rb atom. In the case where the alkali metal atom is the Cs atom, the first frequency corresponds to a D2 line of a saturated spectrum of the Cs atom, and the second frequency corresponds to an energy level difference from an intermediate state to a Rydberg atomic state of the Cs atom.

[0013] With reference to the first aspect, in a possible implementation form of the first aspect, the transmission optical fiber is a single-mode polarization maintaining optical fiber.

[0014] In this implementation form, the single-mode polarization maintaining optical fiber is used as the transmission optical fiber, which can ensure the stability and anti-interference capability of the laser beam during transmission, thereby improving the precision and stability of laser frequency locking.

[0015] With reference to the first aspect, in a possible implementation form of the first aspect, the bichromatic prism is configured to: reflect the coupling laser beam, and transmit the probe light beam.

[0016] With reference to the first aspect, in a possible implementation form of the first aspect, the apparatus further comprises a control and monitoring module, the control and monitoring module being connected to the probe laser, the coupling laser and the PID control circuit. The control and monitoring module is configured to control the probe laser to output the probe laser beam with the first frequency, and control the coupling laser to output the coupling laser beam with the second frequency. The control and monitoring module is further configured to monitor the excitation state of the alkali metal atom.

[0017] In the present implementation, the frequency locking operation of the coupling laser can be remotely realized by the control and monitoring module, so as to improve the efficiency and convenience of the frequency locking operation of the coupling laser.

[0018] In combination with the first aspect, in an alternative implementation, one end of the first fiber collimator is connected to the transmission fiber through a capillary glass tube, and the other end of the first fiber collimator is bonded to the atomic cell. One end of the second fiber collimator is connected to the transmission fiber, and the other end of the second fiber collimator is fixed and bonded to the dichroic prism through a capillary glass tube. One end of the third fiber collimator is connected to the transmission fiber, and the other end of the third fiber collimator is fixed and bonded to the dichroic prism through a capillary glass tube.

[0019] In the present implementation, the first fiber collimator, the second fiber collimator and the third fiber collimator are all connected to the transmission fiber through capillary glass tubes, so that the collimation of the light output by the transmission fiber can be realized.

[0020] In combination with the first aspect, in an alternative implementation, the probe laser beam of the probe laser is coupled into the transmission fiber and connected to the first fiber collimator through a polarization maintaining fusion splice, and the coupling laser beam of the coupling laser is coupled into the transmission fiber and connected to the second fiber collimator through a polarization maintaining fusion splice.

[0021] In the present implementation, the linear polarization direction of the probe laser beam and the coupling laser beam during transmission can be ensured to be unchanged. In this way, the stability and anti-interference capability of the light beams during transmission can be ensured.

[0022] Secondly, the coupling laser beam of a second frequency is output and coupled into the transmission fiber, and the second frequency is associated with the energy level difference of the alkali metal atom from the intermediate state to the Rydberg atomic state. Next, the coupling laser beam is collimated and shot into the atomic cell opposite and coinciding with the probe laser beam, so as to excite the alkali metal atom to the Rydberg atomic state. Further, in the case that the alkali metal atom is excited to the Rydberg atomic state, the probe laser beam after passing through the atomic cell is detected and converted into a probe photoelectric signal. The feedback signal is determined according to the probe photoelectric signal, and the feedback signal is used to characterize the frequency error. Finally, the second frequency is adjusted according to the feedback signal to realize frequency locking.

[0023] In the method, the stability and anti-interference capability of the laser beam during transmission can be ensured through the excellent transmission characteristics of the transmission optical fiber, so that the precision and stability of the laser frequency locking can be improved. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 A structural schematic diagram of a fiber-coupled integrated Rydberg atom coupling laser frequency locking device is provided for an embodiment of the present application.

[0025] Figure 2 A flowchart of a fiber-coupled integrated Rydberg atom coupling laser frequency locking method is provided for an embodiment of the present application.

[0026] BRIEF DESCRIPTION OF DRAWINGS

[0027] 101 - probe laser; 102 - coupling laser; 103 - atomic cell; 104 - first fiber collimator; 105 - second fiber collimator; 106 - third fiber collimator; 107 - bichromatic prism; 108 - photodetector; 109 - PID control circuit; 110 - control and monitoring module. DETAILED DESCRIPTION

[0028] The embodiments will be described in detail below with reference to the drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The implementations described in the following embodiments are not meant to represent all implementations consistent with the present application. Rather, they are merely examples of systems and methods consistent with some aspects of the present application as detailed in the appended claims.

[0029] The laser frequency output by the laser often has a drift, especially when the environmental temperature, vibration condition, etc. change, the laser frequency changes more significantly. In some applications with high requirements for laser frequency, it is necessary to lock the laser frequency output by the laser, i.e. frequency locking. The frequency locking of laser generally refers to locking the laser frequency on a frequency reference which is not easily affected by the outside world and has high stability, such as atomic resonance absorption transition spectral line, etc.

[0030] The Rydberg atom laser frequency locking technology is one of the laser frequency locking technologies. Specifically, the Rydberg atom refers to an atom in a high excited state, and the electron of the atom is excited to a state close to ionization, so the Rydberg atom has some special properties, such as long lifetime, large dipole moment and strong interaction. The Rydberg atom laser frequency locking technology uses the special properties of the Rydberg atom to realize the locking of the laser frequency. Specifically, by interacting the laser beam with the Rydberg atom, the resonance transition of the Rydberg atom is used to detect the drift of the laser frequency, and the laser frequency is locked on the target value through the feedback mechanism. Since the Rydberg atom has the characteristics of high sensitivity and high resolution, the system can realize high-precision and high-stability laser frequency locking.

[0031] However, the Rydberg atom laser frequency locking device based on the Rydberg atom laser frequency locking technology has large volume and weight, low portability and maintainability.

[0032] To solve the above problems, the embodiment of the present application provides a fiber-coupled integrated Rydberg atom coupling laser frequency locking device and method, which integrates the Rydberg atom laser, optical elements and a detector together to realize high-precision locking of the laser frequency. In this way, the volume and weight of the Rydberg atom coupling laser frequency locking device can be greatly reduced, and its portability and maintainability can be improved. At the same time, the excellent transmission characteristics of the optical fiber can ensure the stability and anti-interference ability of the laser signal in the transmission process, thereby improving the precision and stability of the laser frequency locking.

[0033] The fiber-coupled integrated Rydberg atom coupling laser frequency locking device provided by the embodiment of the present application can provide a new type of laser frequency locking solution for the fields of Rydberg atom microwave detection, atomic magnetometer, optical communication, spectral analysis, etc., and has important scientific significance and practical application value.

[0034] The scheme provided by the embodiment of the present application will be introduced below in combination with the drawings.

[0035] Specifically, referring to Figure 1 The structure diagram of the fiber-coupled integrated Rydberg atom coupling laser frequency locking device provided by the embodiment of the present application is shown in Figure 1 As shown, the fiber-coupled integrated Rydberg atom coupling laser frequency locking device provided by the present application comprises a detection laser 101, a coupling laser 102, an atom cell 103 filled with alkali metal atoms, a first fiber collimator 104, a second fiber collimator 105, a third fiber collimator 106, a two-color prism 107, a photodetector 108 and a proportional-integral-derivative (PID) control circuit 109.

[0036] The transmission optical fiber is connected between the probe laser 101 and the first optical fiber collimator 104, between the coupling laser 102 and the second optical fiber collimator 105, and between the third optical fiber collimator 106 and the photodetector 108.

[0037] The coupling laser 102 and the PID control circuit 109 are connected by an electric wire, and the PID control circuit 109 and the photodetector 108 are also connected by an electric wire.

[0038] Specifically, the probe laser 101 is configured to output a probe laser beam at a first frequency, and the probe laser beam is coupled into the transmission optical fiber, the first frequency being associated with an intermediate state of the alkali metal atom. The probe laser beam is collimated by the first optical fiber collimator 104 after passing through the transmission optical fiber, and then enters the atomic cell 103. The probe laser beam is configured to excite the alkali metal atom to the intermediate state.

[0039] The first optical fiber collimator 104 is configured to collimate the probe laser beam. The atomic cell 103 can have a cylindrical shape, a cuboid shape, or a special shape according to actual application requirements.

[0040] The coupling laser 102 is configured to output a coupling laser beam at a second frequency, and the coupling laser beam is coupled into the transmission optical fiber, the second frequency being associated with an energy level difference of the alkali metal atom from the intermediate state to the Rydberg atomic state. The coupling laser beam enters the atomic cell 103 through the second optical fiber collimator 105 and the bichromatic prism 107. The coupling laser beam and the probe laser beam are opposite and coincident in the atomic cell 103. The coupling laser beam is configured to excite the alkali metal atom to the Rydberg atomic state.

[0041] The second optical fiber collimator 105 is configured to collimate the coupling laser beam.

[0042] Further, when the alkali metal atom is excited to the Rydberg atomic state, the probe light beam passes through the atomic cell 103, and then is coupled into the transmission optical fiber through the bichromatic prism 107 and the third optical fiber collimator 106. The probe light beam is transmitted to the photodetector 108 through the transmission optical fiber, and is converted into a probe photoelectric signal by the photodetector 108 and output to the PID control circuit 109. The probe photoelectric signal is processed into a feedback signal by the PID control circuit 109 and output to the coupling laser 102. The coupling laser 102 adjusts the second frequency according to the feedback signal to achieve frequency locking.

[0043] Specifically, in the atomic cell 103, the coupling laser beam and the probe laser beam are mutually overlapped and transmitted oppositely. The probe laser beam excites the alkali metal atoms to an intermediate state. When the frequency of the coupling laser beam matches the energy level difference of the alkali metal atoms, the laser is absorbed by the alkali metal atoms, exciting the alkali metal atoms to the Rydberg atomic state. This laser absorption process is used to monitor and adjust the frequency (i.e., the second frequency) of the coupling laser.

[0044] The fiber-coupled integrated Rydberg atom coupling laser frequency locking device provided by the embodiments of the present application realizes the locking of the laser frequency by monitoring the interaction between the laser and the alkali metal atoms, i.e., the absorption of the laser. When the frequency of the coupling laser beam matches the energy level difference of the alkali metal atoms, the absorption of the probe laser beam decreases, forming an electromagnetically induced transparency phenomenon, i.e., the EIT effect. The Rydberg atom coupling laser frequency locking device can adjust the frequency (i.e., the second frequency) of the coupling laser beam through the PID control circuit 109 to minimize the absorption signal of the probe light beam, thereby realizing the locking of the laser frequency.

[0045] The fiber-coupled integrated Rydberg atom coupling laser frequency locking device provided by the embodiments of the present application realizes the locking of the laser frequency by monitoring the interaction between the laser and the alkali metal atoms, i.e., the absorption of the laser. When the frequency of the coupling laser beam matches the energy level difference of the alkali metal atoms, the absorption of the probe laser beam decreases, forming an electromagnetically induced transparency phenomenon, i.e., the EIT effect. The Rydberg atom coupling laser frequency locking device can adjust the frequency (i.e., the second frequency) of the coupling laser beam through the PID control circuit 109 to minimize the absorption signal of the probe light beam, thereby realizing the locking of the laser frequency.

[0046] In some embodiments, the PID control circuit 109 is further configured to perform frequency triangular wave scanning on the coupling laser 102 to obtain the frequency of the coupling laser beam output by the coupling laser 102. The coupling laser beam output by the coupling laser 102 is frequency modulated.

[0047] In some embodiments, the PID control circuit 109 is further configured to demodulate the probe photoelectric signal to obtain a frequency discrimination signal. The frequency discrimination signal is subjected to proportional, integral, and differential control to obtain a feedback signal, and the feedback signal is used to represent the frequency error.

[0048] Specifically, when the frequency of the coupling laser beam matches the energy level difference of the alkali metal atom, the absorption of the probe laser beam is reduced, forming an electromagnetic induced transparency phenomenon, i.e., an EIT effect.

[0049] At the frequency to be locked, i.e., at the specific Rydberg state transition frequency of the coupling light, the PID control circuit 109 can perform a triangular wave scan on the frequency of the coupling laser 102, and simultaneously apply a frequency modulation ω. The signal of the probe laser beam received by the photodetector 108, i.e., the probe photoelectric signal, will receive a 2-fold frequency signal, i.e., a signal with a frequency of 2ω. After demodulating the probe photoelectric signal, the obtained signal is a frequency discrimination signal, and the zero-crossing point of the frequency discrimination signal corresponds to the EIT peak value of the probe photoelectric signal. When the triangular wave scan is reduced to zero, the demodulated signal is the frequency discrimination signal. The PID control circuit 109 can convert the frequency discrimination signal into a feedback signal and input the feedback signal into the coupling laser 102, so as to realize the second frequency locking of the coupling laser 102 to the peak value of the atom EIT.

[0050] In some embodiments, the alkali metal atom filled in the atomic cell 103 is one of the following: a potassium K atom, a rubidium Rb atom, and a cesium Cs atom.

[0051] Specifically, in the case where the alkali metal atom is a K atom, the first frequency corresponds to the D2 line of the saturated spectrum of the K atom, and the second frequency corresponds to the energy level difference from the intermediate state to the Rydberg atomic state of the K atom.

[0052] In the case where the alkali metal atom is a Rb atom, the first frequency corresponds to the D2 line of the saturated spectrum of the Rb atom, and the second frequency corresponds to the energy level difference from the intermediate state to the Rydberg atomic state of the Rb atom.

[0053] In the case where the alkali metal atom is a Cs atom, the first frequency corresponds to the D2 line of the saturated spectrum of the Cs atom, and the second frequency corresponds to the energy level difference from the intermediate state to the Rydberg atomic state of the Cs atom.

[0054] For example, in the case where the alkali metal atom is a Cs atom, the first frequency of the probe laser 101 can correspond to the D2 line of the saturated spectrum of the Cs atom, i.e., can correspond to a wavelength of 852 nanometers (nm).

[0055] The probe laser beam with the first frequency can excite the alkali metal atom from the ground state 6S 1 / 2 to the intermediate state 6P 3 / 2 . The coupling laser beam with the second frequency further excites the alkali metal atom from the intermediate state to the Rydberg atomic state. For example, the coupling laser beam with a wavelength of 509.394 nm can further excite the Cs atom from the intermediate state 6P 3 / 2 to 53D 5 / 2 .

[0056] When the wavelength is near 509.394 nm, the PID control circuit 109 can linearly scan the frequency of the coupling laser 102, and a sharp peak signal can appear in the scanned signal, corresponding to an electromagnetically induced transparency (EIT) signal. By locking the EIT peak, the second frequency of the coupling laser 102 can be locked at the transition frequency point of 6P 3 / 2 to 53D 5 / 2 , that is, 509.394 nm. The frequency locking here can control the frequency drift range of the coupling laser 102 to within 1 MHz. In some embodiments, different alkali metal atoms and their Rydberg atomic states can correspond to different locking frequency points of the coupling laser.

[0057] In some embodiments, the transmission optical fiber in the embodiment of the present application is a single-mode polarization maintaining optical fiber. The single-mode polarization maintaining optical fiber can only transmit a single fundamental mode, is suitable for large-capacity long-distance transmission, and can ensure that the linear polarization direction of the transmitted light is unchanged. In this way, the stability and anti-interference ability of the laser beam during transmission can be ensured, thereby improving the precision and stability of the laser frequency locking.

[0058] In some embodiments, the two-color prism 107 is configured to reflect the coupling laser beam and transmit the probe light beam. In this way, the coupling laser beam can be injected into the atomic cell 103, and the probe light beam can be injected out of the atomic cell 103, so as to realize the frequency locking of the coupling laser 102.

[0059] In some embodiments, as shown in Figure 1 , the apparatus further includes a control and monitoring module 110. The control and monitoring module 110 is connected with the probe laser 101, the coupling laser 102, and the PID control circuit 109. The control and monitoring module 110 can be configured to control the probe laser 101 to output the probe laser beam with the first frequency, and control the coupling laser 102 to output the coupling laser beam with the second frequency. The control and monitoring module 110 can also be configured to monitor the excitation state of the alkali metal atom.

[0060] Specifically, the control and monitoring module 110 can be configured to adjust the laser frequency, monitor the absorption of the laser, and ensure the stable operation of the system. The control and monitoring module 110 can be remotely controlled by an electronic device, so that the frequency locking operation of the coupling laser 102 is more convenient and efficient.

[0061] In some embodiments, the first optical fiber collimator 104, the second optical fiber collimator 105, and the third optical fiber collimator 106 can be micro collimators, so as to further reduce the volume of the modulation transfer spectrum frequency locking apparatus.

[0062] For example, the first fiber collimator 104, the second fiber collimator 105 and the third fiber collimator 106 can be composed of C-lens or L-lens.

[0063] In some embodiments, one end of the first fiber collimator 104 is connected with the transmission fiber through a capillary glass tube, and the other end of the first fiber collimator 104 is bonded with the atomic cell 103. One end of the second fiber collimator 105 is connected with the transmission fiber, and the other end of the second fiber collimator 105 is fixed and bonded to the dichroic prism 107 through a capillary glass tube. One end of the third fiber collimator 106 is connected with the transmission fiber, and the other end of the third fiber collimator 106 is fixed and bonded to the dichroic prism 107 through a capillary glass tube.

[0064] In some embodiments, the probe laser beam of the probe laser 101 is coupled into the transmission fiber, and is connected with the first fiber collimator 104 through a polarization maintaining fusion splice. The coupling laser beam of the coupling laser 102 is coupled into the transmission fiber, and is connected with the second fiber collimator 105 through a polarization maintaining fusion splice.

[0065] In some embodiments, the probe laser beam of the probe laser 101 is coupled into the transmission fiber, and is connected with the first fiber collimator 104 through a polarization maintaining fusion splice. The coupling laser beam of the coupling laser 102 is coupled into the transmission fiber, and is connected with the second fiber collimator 105 through a polarization maintaining fusion splice. Figure 1 The fiber-coupled integrated Rydberg atom coupling laser frequency locking device shown in the figure is taken as an example to illustrate the preparation and frequency locking steps of the fiber-coupled integrated Rydberg atom coupling laser frequency locking device provided by the embodiments of the present application.

[0066] First, the micro fiber collimator coupled atomic cell 103 is made. The first fiber collimator 104, the second fiber collimator 105 and the third fiber collimator 106 can be composed of cylindrical C-lens. The first fiber collimator 104, the second fiber collimator 105 and the third fiber collimator 106 are connected with the transmission fiber through capillary glass tubes to realize the collimation of the light emitted by the transmission fiber. The atomic cell 103 has a dichroic prism 107 bonded to one end thereof. The first fiber collimator 104 is bonded to one end of the atomic cell 103, and the second fiber collimator 105 and the third fiber collimator 106 are bonded to two faces of the dichroic prism 107 respectively. During the bonding process, it is ensured that the light emitted by the first fiber collimator 104, the second fiber collimator 105 and the third fiber collimator 106 can converge to a point, and the light emitted by the first fiber collimator 104 and the second fiber collimator 105 can coincide.

[0067] Then, the probe laser beam output by the probe laser 101 is coupled into the transmission fiber, and the other end of the transmission fiber is connected with the first fiber collimator 104 through a polarization maintaining fusion splice. The coupling laser beam output by the coupling laser 102 is coupled into the transmission fiber, and the other end of the transmission fiber is connected with the second fiber collimator 105 through a polarization maintaining fusion splice.

[0068] Further, the probe laser 101 is coupled into the third fiber collimator 106 through the probe laser beam of the atomic cell 103 and the bichromatic prism 107, and the probe laser beam is received by the photodetector 108. The spectral signal of the probe laser beam is converted into a probe photoelectric signal by the amplification circuit of the photodetector 108, and the probe photoelectric signal is transmitted to the PID control circuit 109.

[0069] Finally, the frequency demodulation signal of the probe photoelectric signal of the photodetector 108 is processed in the PID control circuit 109 to obtain a feedback signal, and the feedback signal is transmitted to the coupling laser 102 to realize frequency locking of the second frequency.

[0070] The embodiment of the present application also provides a fiber-coupled integrated Rydberg atom coupling laser frequency locking method, which can be applied to the fiber-coupled integrated Rydberg atom coupling laser frequency locking device provided in the above embodiment. Figure 2 The flowchart of the fiber-coupled integrated Rydberg atom coupling laser frequency locking method provided in the embodiment of the present application is shown in FIG. 1, and the fiber-coupled integrated Rydberg atom coupling laser frequency locking method provided in the present application comprises the following steps S101-S107. Figure 2

[0071] S101, output a probe laser beam of a first frequency, and couple the probe laser beam into a transmission fiber.

[0072] The first frequency is associated with an intermediate state of an alkali metal atom, and the transmission fiber is used for transmitting the probe laser beam.

[0073] S102, collimate the probe laser beam and inject it into an atomic cell.

[0074] The atomic cell is filled with alkali metal atoms.

[0075] S103, output a coupling laser beam of a second frequency, and couple the coupling laser beam into the transmission fiber.

[0076] The second frequency is associated with an energy level difference of the alkali metal atom from the intermediate state to a Rydberg atomic state.

[0077] S104, collimate the coupling laser beam, and inject it into the atomic cell opposite to and coinciding with the probe laser beam, so as to excite the alkali metal atom to the Rydberg atomic state.

[0078] S105, in the case that the alkali metal atom is excited to the Rydberg atomic state, detect the probe laser beam after passing through the atomic cell, and convert it into a probe photoelectric signal.

[0079] S106, determine a feedback signal according to the probe photoelectric signal, and the feedback signal is used for characterizing a frequency error.​

[0080] S107, adjust the second frequency according to the feedback signal to realize frequency locking.

[0081] Thus, by the fiber-coupled integrated Rydberg atom coupling laser frequency locking method shown in S101-S107, the stability and anti-interference ability of the laser beam in the transmission process can be ensured by the excellent transmission characteristics of the transmission fiber, so as to improve the precision and stability of the laser frequency locking.

[0082] Through the description of the above embodiments, those skilled in the art can clearly understand that, for the convenience and brevity of description, only the division of the above functional modules is exemplified, and in actual application, the above functions can be completed by different functional modules according to needs, that is, the internal structure of the device is divided into different functional modules to complete all or part of the functions described above.

[0083] In the description of the present application, it should be understood that the terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first", "second" can be explicitly or implicitly included at least one of the features. In the description of the present application, the meaning of "a plurality of" is at least two, such as two, three, etc., unless otherwise specifically limited.

[0084] In the present application, unless otherwise specifically defined and limited, the terms "mounting", "connection", "connection", "fixing" and the like should be understood in a broad sense, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship of two elements, unless otherwise specifically limited. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0085] In the description of the present application, the description of the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" 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 application. In the present application, the illustrative description of the above terms is not necessarily for 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 the different embodiments or examples described in the present application and the features of the different embodiments or examples without contradiction.

[0086] The similar parts among the embodiments provided in the present application can be referred to each other, the specific embodiments provided above are only several examples under the general concept of the present application, and do not constitute the limitation of the protection scope of the present application. Any other embodiments extended according to the present application scheme without creative labor for the person skilled in the art shall fall within the protection scope of the present application.

Claims

1. A fiber-coupled integrated Rydberg atom coupling laser frequency locking device, characterized in that, The application relates to a frequency locking device for a coupling laser, comprising: a probe laser, a coupling laser, an atomic cell filled with alkali metal atoms, a first fiber collimator, a second fiber collimator, a third fiber collimator, a bichromatic prism, a photodetector and a proportional-integral-differential (PID) control circuit; wherein the probe laser and the first fiber collimator, the coupling laser and the second fiber collimator, and the third fiber collimator and the photodetector are connected through transmission optical fibers; the coupling laser and the PID control circuit, and the PID control circuit and the photodetector are connected through wires; the probe laser is used for outputting a probe laser beam with a first frequency, and coupling the probe laser beam into the transmission optical fiber, the first frequency being associated with an intermediate state of the alkali metal atoms; the probe laser beam is collimated through the first fiber collimator and injected into the atomic cell through the transmission optical fiber, and the probe laser beam is used for exciting the alkali metal atoms to the intermediate state; the coupling laser is used for outputting a coupling laser beam with a second frequency, and coupling the coupling laser beam into the transmission optical fiber, the second frequency being associated with an energy level difference of the alkali metal atoms from the intermediate state to a Rydberg atomic state; the coupling laser beam is injected into the atomic cell through the second fiber collimator and the bichromatic prism, and the coupling laser beam and the probe laser beam are opposite and coincident in the atomic cell, and the coupling laser beam is used for exciting the alkali metal atoms to the Rydberg atomic state; in the case that the alkali metal atoms are excited to the Rydberg atomic state, a probe light beam is coupled into the transmission optical fiber through the bichromatic prism and the third fiber collimator after passing through the atomic cell, and is transmitted to the photodetector through the transmission optical fiber, is converted into a probe photoelectric signal through the photodetector and is output to the PID control circuit, the probe photoelectric signal is processed into a feedback signal through the PID control circuit and is output to the coupling laser, and the coupling laser adjusts the second frequency according to the feedback signal to realize frequency locking.

2. The apparatus of claim 1, wherein, The PID control circuit is further used for: carrying out frequency triangular wave scanning on the coupling laser to obtain the frequency of the coupling laser output coupling laser beam; carrying out frequency modulation on the coupling laser output coupling laser beam.

3. The apparatus of claim 2, wherein, The PID control circuit is further used for: demodulating the probe photoelectric signal to obtain a frequency discrimination signal; carrying out proportional, integral and differential control on the frequency discrimination signal to obtain the feedback signal, and the feedback signal is used for characterizing frequency error.

4. The device according to any of claims 1-3, characterized in that The alkali metal atoms are one of the following: potassium (K) atoms, rubidium (Rb) atoms and cesium (Cs) atoms; in the case that the alkali metal atoms are K atoms, the first frequency corresponds to a D2 line of a K atom saturated spectrum, and the second frequency corresponds to an energy level difference of the K atoms from the intermediate state to the Rydberg atomic state. In the case that the alkali metal atom is a Rb atom, the first frequency corresponds to a D2 line of a saturated spectrum of the Rb atom, and the second frequency corresponds to an energy level difference of the Rb atom from an intermediate state to a Rydberg atomic state; In the case that the alkali metal atom is a Cs atom, the first frequency corresponds to a D2 line of a saturated spectrum of the Cs atom, and the second frequency corresponds to an energy level difference of the Cs atom from an intermediate state to a Rydberg atomic state.

5. The device of any one of claims 1-3, wherein, The transmission optical fiber is a single-mode polarization maintaining optical fiber.

6. The device of any one of claims 1-3, wherein, The two-color prism is configured to reflect the coupling laser beam and transmit the probe light beam.

7. The device of any one of claims 1-3, wherein, The device further comprises a control and monitoring module, which is connected with the probe laser, the coupling laser, and the PID control circuit. The control and monitoring module is configured to control the probe laser to output a probe laser beam with a first frequency, and control the coupling laser to output a coupling laser beam with a second frequency. The control and monitoring module is further configured to monitor an excitation state of the alkali metal atom.

8. The device of any one of claims 1-3, wherein, One end of the first fiber collimator is connected with the transmission optical fiber through a capillary glass tube, and the other end of the first fiber collimator is bonded to the atomic cell; one end of the second fiber collimator is connected with the transmission optical fiber, and the other end of the second fiber collimator is fixed and bonded to the two-color prism through a capillary glass tube; one end of the third fiber collimator is connected with the transmission optical fiber, and the other end of the third fiber collimator is fixed and bonded to the two-color prism through a capillary glass tube.

9. The device of any one of claims 1-3, wherein, The probe laser beam of the probe laser is coupled into the transmission optical fiber and connected with the first fiber collimator through a polarization maintaining fusion splice, and the coupling laser beam of the coupling laser is coupled into the transmission optical fiber and connected with the second fiber collimator through a polarization maintaining fusion splice.

10. A method of fiber-coupled integrated Rydberg atom coupling laser frequency locking, characterized in that, The device comprises: outputting a probe laser beam with a first frequency, and coupling the probe laser beam into a transmission optical fiber, the first frequency being associated with an intermediate state of an alkali metal atom, the transmission optical fiber being configured to transmit the probe laser beam; collimating the probe laser beam and injecting the collimated probe laser beam into an atomic cell, the atomic cell being filled with the alkali metal atom; outputting a coupling laser beam with a second frequency, and coupling the coupling laser beam into the transmission optical fiber, the second frequency being associated with an energy level difference of the alkali metal atom from the intermediate state to a Rydberg atomic state; collimating the coupling laser beam, and injecting the collimated coupling laser beam into the atomic cell opposite to and coinciding with the probe laser beam, so as to excite the alkali metal atom to the Rydberg atomic state; in the case that the alkali metal atom is excited to the Rydberg atomic state, detecting the probe laser beam after passing through the atomic cell and converting the probe laser beam into a probe photoelectric signal; determining a feedback signal according to the probe photoelectric signal, the feedback signal being configured to represent a frequency error; adjusting the second frequency according to the feedback signal, so as to realize frequency locking.

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