Method and device for generating spatially separated dual-wavelength blue laser

Abstract

The invention relates to a method and device for generating spatially separated dual-wavelength blue laser, and the method comprises the following steps: (1) obtaining 852 nm pumping laser and 921 nm pumping laser, and enabling the two beams of pumping laser to have circular polarization in the same rotation direction; (2) the two beams of pumping laser enter the cesium atom steam chamber, the included angle of the two beams of pumping laser entering the cesium atom steam chamber is theta, and theta is larger than or equal to 2 degrees and smaller than or equal to 3 degrees; (3) exciting a four-wave mixing process in the cesium atom steam chamber by 852 nm and 921 nm pumping laser to generate blue laser with dual wavelengths of 455 nm and 459 nm; and (4) processing the two beams of pump laser and the two beams of blue laser emitted from the cesium atom steam chamber through a lens and a diaphragm in sequence to obtain spatially separated dual-wavelength blue laser. The corresponding device is designed according to the method. According to the method and the device, the dual-wavelength blue laser with the wavelength of 455nm and the wavelength of 459nm can be generated at the same time, the dual-wavelength blue laser directly corresponds to the 6S1 / 2-7P3 / 2 absorption line and the 6S1 / 2-7P1 / 2 absorption line of cesium atoms, the output power of the blue laser is high, and the frequency stability is high.

Description

Technical Field:

[0001] The present invention relates to the technical field of the interaction between light and atoms in quantum optics, and particularly relates to a method and device for generating spatially separated dual-wavelength blue lasers. Background Art:

[0002] Blue lasers have characteristics such as short wavelength and high energy density, so they have been widely used in fields such as underwater wireless communication, bio-fluorescence imaging, high-density data storage, laser processing, and laser etching. With the emergence of commercial continuous narrow-linewidth blue lasers, blue lasers have gradually been used in the basic research of quantum optics and related technology development. Blue lasers can excite atoms to higher energy states, enabling more atomic energy states and a wider spectral range to be involved in the interaction between light and atoms, greatly expanding the research and application scope in fields such as four-wave mixing, frequency conversion, and quantum light source preparation.

[0003] Research shows that by using the 5S 1 / 2 →6P 3 / 2 →5D 5 / 2 transition of rubidium atoms or the 6S 1 / 2 →7P 3 / 2 →6D 5 / 2 transition, the electromagnetic induction transparency effect and the nonlinear four-wave mixing effect involving blue lasers and mid- and long-wave infrared light can be generated, which have potential application value in mid- and long-wave infrared detection. In these applications, in order to efficiently excite atoms, it is required that the frequency and linewidth of the blue laser precisely correspond to the atomic absorption line. Therefore, preparing blue lasers corresponding to the atomic absorption line is of great significance for the basic research and technology development in related aspects of quantum optics.

[0004] At present, there are mainly three types of technical solutions for preparing blue lasers: (1) blue lasers based on semiconductor laser diodes; (2) blue lasers based on the frequency doubling or frequency conversion process of nonlinear crystals; (3) blue lasers based on the four-wave mixing process of alkali metal atoms. In the first type of solution, the semiconductor laser diode directly emits blue laser after applying current, but the emitted blue laser generally has a relatively large linewidth. To obtain a narrow-linewidth blue laser, a frequency selection element is needed to select the frequency of the blue laser emitted by the laser diode. Commercial tunable single-frequency blue semiconductor lasers mainly adopt the external cavity grating feedback technology to achieve single-frequency operation. In the second type of solution, the nonlinear crystal can convert the near-infrared laser into blue laser through the optical frequency doubling or frequency up-conversion process, and then realize the single-frequency operation of the laser through the optical resonator. In these two types of solutions, in order to achieve the single-frequency operation of the laser, a very precise and complex optical resonator servo system is often required, and the laser diode or nonlinear crystal is highly sensitive to working conditions such as current and temperature. Therefore, it is very difficult to stably tune the laser to the atomic absorption line for a long time. In the third type of solution, the alkali metal atom vapor cell converts the near-infrared laser into blue laser through the four-wave mixing process. Compared with the first and second types of solutions, the blue laser generated by this solution directly corresponds to the atomic absorption line. However, in this type of solution, the generated blue laser and the near-infrared pump laser overlap, and a dichroic mirror or interference filter is needed to filter out the near-infrared pump laser. While the blue laser is separated, a relatively large power loss also occurs. In addition, the four-wave mixing process excited in the atomic vapor cell does not strictly satisfy the phase matching condition, which will greatly reduce the output power of the blue laser.

[0005] It should be noted that the above content belongs to the technical cognition scope of the inventor and does not necessarily constitute the prior art. Summary of the Invention:

[0006] The purpose of the present invention is to solve the problems existing in the prior art, and provide a method and device for generating spatially separated dual-wavelength blue lasers, subverting the existing technical ideas for preparing blue lasers. Innovatively, two near-infrared pump lasers are used to act on a cesium atom vapor cell to excite the four-wave mixing effect, and through 7P 3 / 2 →6S 1 / 2 and 7P 1 / 2 →6S 1 / 2 transitions to radiate spatially separated dual-wavelength blue lasers.

[0007] A method for generating spatially separated dual-wavelength blue lasers includes the following steps:

[0008] (1) Obtain the 852 nm pump laser and the 921 nm pump laser, and process the 852 nm pump laser and the 921 nm pump laser respectively so that the two pump lasers have circular polarization with the same rotation direction;

[0009] (2) The two pump lasers enter the cesium atomic vapor cell, and the included angle between the two pump lasers entering the cesium atomic vapor cell is θ, 2° ≤ θ ≤ 3°, and the two pump lasers intersect at the center of the cesium atomic vapor cell;

[0010] (3) The 852 nm pump laser and the 921 nm pump laser excite the four-wave mixing process in the cesium atomic vapor cell, and radiate blue laser with a wavelength of 455 nm through the 7P 3 / 2 →6S 1 / 2 transition, and radiate blue laser with a wavelength of 459 nm through the 7P 1 / 2 →6S 1 / 2 transition, thereby generating dual-wavelength blue laser;

[0011] (4) The two pump lasers and the two blue lasers emitted from the cesium atomic vapor cell become spatially separated parallel light beams after passing through the lens; then the two pump lasers are blocked by the aperture, so as to obtain spatially separated dual-wavelength blue laser with parallel output.

[0012] Further, the method for adjusting the included angle between the two pump lasers entering the cesium atomic vapor cell in step (2) includes the following steps:

[0013] S1. First, adjust the two pump lasers to be parallel;

[0014] S2. The parallel two pump lasers are adjusted in angle through the lens, and the rear focal point of the lens is located at the center of the cesium atomic vapor cell, so as to ensure that the two pump lasers intersect at the center of the cesium atomic vapor cell;

[0015] S3. Keep one of the pump lasers passing through the center of the lens without changing its direction, and the other pump laser refracts through one side of the lens, so as to realize that the two pump lasers enter the cesium atomic vapor cell at a set included angle, and the size of the included angle can be adjusted by adjusting the distance between the two pump lasers.

[0016] A device for generating spatially separated dual-wavelength blue laser, comprising:

[0017] Laser A, the laser A emits pump laser A with a wavelength of 852 nm, the pump laser A is divided into two beams after passing through a half-wave plate A and a polarization beam splitter prism A, one beam is the reflected pump laser A entering the pump laser frequency monitoring system, and the other beam is the transmitted pump laser A, which is prepared to the right-handed circular polarization state through a half-wave plate B and a quarter-wave plate A;

[0018] Laser B, which emits pump laser B with a wavelength of 921 nm. The pump laser B is divided into two beams after passing through a half-wave plate C and a polarization beam splitter prism B. One beam is the reflected pump laser B that enters the pump laser frequency monitoring system, and the other beam is the transmitted pump laser B that is prepared into a right-handed circular polarization state through a reflecting mirror, a half-wave plate D, and a quarter-wave plate B. The pump laser B is reflected by a D-shaped mirror and becomes parallel to the pump laser A.

[0019] The pump laser A and the pump laser B pass through lens A in parallel and enter the cesium atomic vapor cell at a set angle. The center of the cesium atomic vapor cell is located at the rear focal point of lens A, so as to ensure that the pump laser A and the pump laser B intersect at the center of the cesium atomic vapor cell. The pump laser A and the pump laser B excite a four-wave mixing process in the cesium atomic vapor cell, thereby generating blue lasers with wavelengths of 455 nm and 459 nm and long-wave infrared light with wavelengths of 15.6 μm and 12.1 μm. A lens B and a diaphragm are respectively arranged at intervals at the outlet end of the cesium atomic vapor cell. Among them, the 15.6 μm and 12.1 μm long-wave infrared light cannot penetrate the glass end face of the cesium atomic vapor cell. The two beams of pump laser and two beams of blue laser emitted from the cesium atomic vapor cell become spatially separated parallel beams after passing through lens B, and then the two beams of pump laser are blocked by the diaphragm, so as to obtain spatially separated dual-wavelength blue laser with parallel output.

[0020] The laser A and the laser B adopt continuously tunable semiconductor lasers.

[0021] Both end faces of the cesium atomic vapor cell are coated with a broadband antireflection dielectric film of 400 nm to 1100 nm.

[0022] The cesium atomic vapor cell is wrapped in multiple layers of μ-metal foil.

[0023] The cesium atomic vapor cell is fixed in a heating furnace, and the heating furnace is connected to a temperature controller.

[0024] The propagation directions of the pump laser, the long-wave infrared light, and the blue laser must satisfy the phase matching condition, and its expression is:

[0025] n 852 k 852 +n 921 k 921 =n 455 k 455 +n 15.6 k 15.6

[0026] n 852 k 852 +n 921 k 921 =n 459 k 459 +n12.1 k 12.1

[0027] In the formula, n 852 is the refractive index of the 852 nm pump laser, and k 852 is the vacuum wave vector of the 852 nm pump laser, and n 921 is the refractive index of the 921 nm pump laser, and k 921 is the vacuum wave vector of the 921 nm pump laser, and n 455 is the refractive index of the 455 nm blue laser, and k 455 is the vacuum wave vector of the 455 nm blue laser, and n 459 is the refractive index of the 459 nm blue laser, and k 459 is the vacuum wave vector of the 459 nm blue laser, and n 15.6 is the refractive index of the 15.6 μm long-wave infrared light, and k 15.6 is the vacuum wave vector of the 15.6 μm long-wave infrared light, and n 12.1 is the refractive index of the 12.1 μm long-wave infrared light, and k 12.1 is the vacuum wave vector of the 12.1 μm long-wave infrared light.

[0028] The pump laser frequency monitoring system includes:

[0029] Laser C emits a probe laser with a wavelength of 852 nm. The probe laser is divided into two beams after passing through a half-wave plate E and a polarization beam splitter prism C:

[0030] One beam is the reflected probe laser A that enters a saturated absorption spectroscopy device composed of a beam splitter A, a mirror A, a cesium atomic vapor cell A, and a beam splitter B. The intensity of the probe laser A is measured by a photodetector A, and the photodetector A is connected to a digital oscilloscope;

[0031] The other beam is the transmitted probe laser B that is further divided into two beams after passing through a half-wave plate F and a polarization beam splitter prism D:

[0032] One beam is the transmitted probe laser C that enters the cesium atomic vapor cell B. The pump laser B that is reflected from the polarization beam splitter B and then reflected from the polarization beam splitter E enters the cesium atomic vapor cell B in the opposite direction. The probe laser C and the pump laser B respectively excite the 6S 1 / 2 →6P 3 / 2 transition and the 6P 3 / 2 →6D 3 / 2 transition to produce an electromagnetically induced transparency effect. The beam collector A is used to block the pump laser B reflected from the polarization beam splitter D; the photodetector B measures the intensity of the probe laser C transmitted from the polarization beam splitter E, and the photodetector B is connected to a digital oscilloscope;

[0033] Another beam is the reflected probe laser D. After passing through the mirror B, the half-wave plate G, and the polarization beam splitter prism F, it enters the cesium atomic vapor cell C. The pump laser A reflected from the polarization beam splitter prism A and then reflected from the polarization beam splitter prism F enters the cesium atomic vapor cell C along the same direction. The probe laser D and the pump laser A respectively excite the 6S 1 / 2 →6P 3 / 2 different hyperfine transitions, thereby generating the electromagnetically induced transparency effect. A polarization beam splitter prism G is provided at the output end of the cesium atomic vapor cell C. The beam collector B is used to block the pump laser A reflected from the polarization beam splitter prism G. The photodetector C measures the light intensity of the probe laser D transmitted through the polarization beam splitter prism G. The photodetector C is connected to a digital oscilloscope.

[0034] The present invention adopts the above method and can bring the following beneficial effects:

[0035] (1) It can simultaneously generate dual-wavelength blue laser with wavelengths of 455 nm and 459 nm that are spatially separated, directly corresponding to the 6S of cesium atoms 1 / 2 →7P 3 / 2 absorption line and 6S 1 / 2 →7P 1 / 2 absorption line;

[0036] (2) The generated dual-wavelength blue laser is spatially separated from the pump laser, avoiding the loss of the blue laser output power caused by using a dichroic mirror or an interference filter to filter out the near-infrared pump laser;

[0037] (3) It satisfies the phase matching condition to the greatest extent, thereby improving the output power of the dual-wavelength blue laser;

[0038] (4) The transition frequency of cesium atoms is highly stable. Single-frequency operation can be achieved without an optical resonator, avoiding expensive optical resonators and complex servo systems, and the core components are easy to integrate. Description of the Drawings:

[0039] Figure 1 It is a schematic structural diagram of the device for generating spatially separated dual-wavelength blue laser according to the present invention;

[0040] Figure 2 It is a schematic diagram of the energy states of cesium atoms according to the present invention;

[0041] Figure 3 It is a schematic structural diagram of the blue laser spot recorded according to the present invention;

[0042] Figure 4 It is a curve of the blue laser light intensity varying with the frequency detuning of the 852 nm pump laser according to the present invention;

[0043] Figure 5The curve of the blue laser power varying with the 852 nm pump laser power when the 921 nm pump laser power of the present invention is maintained at 26 mW;

[0044] Figure 6 The curve of the blue laser power varying with the 921 nm pump laser power when the 852 nm pump laser power of the present invention is maintained at 50 mW;

[0045] Figure 7 The curve of the blue laser power of the present invention varying with the temperature of the cesium atomic vapor cell;

[0046] Among them, 1. Laser A, 2. Half-wave plate A, 3. Polarizing beam splitter prism A, 4. Half-wave plate B, 5. Quarter-wave plate A, 6. Laser B, 7. Half-wave plate C, 8. Polarizing beam splitter prism B, 9. Reflecting mirror, 10. Half-wave plate D, 11. Quarter-wave plate B, 12. D-shaped reflecting mirror, 13. Lens A, 14. Cesium atomic vapor cell, 15. Lens B, 16. Diaphragm, 17. 455 nm blue laser, 18. 459 nm blue laser, 19. Heating furnace, 20. Temperature controller, 21. Laser C, 22. Half-wave plate E, 23. Polarizing beam splitter prism C, 24. Beam splitter A, 25. Reflecting mirror A, 26. Cesium atomic vapor cell A, 27. Beam splitter B, 28. Photoelectric detector A, 29. Half-wave plate F, 30. Polarizing beam splitter prism D, 31. Cesium atomic vapor cell B, 32. Polarizing beam splitter prism E, 33. Beam collector A, 34. Photoelectric detector B, 35. Reflecting mirror B, 36. Half-wave plate G, 37. Polarizing beam splitter prism F, 38. Cesium atomic vapor cell C, 39. Polarizing beam splitter prism G, 40. Beam collector B, 41. Photoelectric detector C, 42. Digital oscilloscope. Specific embodiments:

[0047] In order to more clearly explain the overall concept of the present invention, the following will be described in detail by way of examples in conjunction with the accompanying drawings of the specification.

[0048] In the following description, many specific details are set forth in order to fully understand the present invention. However, the present invention may be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited by the specific embodiments disclosed below.

[0049] Each embodiment in this specification is described in a progressive manner. The same or similar parts among the embodiments can be referred to each other, and the key points of each embodiment are to illustrate the differences from other embodiments.

[0050] As Figure 1-7 shown, a method for generating spatially separated dual-wavelength blue lasers includes the following steps:

[0051] (1) Obtain the 852 nm pump laser and the 921 nm pump laser, and process the 852 nm pump laser and the 921 nm pump laser respectively so that the two pump lasers have circular polarization with the same rotation direction;

[0052] (2) The two pump lasers enter the cesium atomic vapor cell 14, and the included angle between the two pump lasers entering the cesium atomic vapor cell 14 is θ, 2° ≤ θ ≤ 3°, and the two pump lasers intersect at the center of the cesium atomic vapor cell;

[0053] (3) The 852 nm pump laser and the 921 nm pump laser excite a four-wave mixing process in the cesium atomic vapor cell 14, and radiate blue laser light with a wavelength of 455 nm 17 through the 7P 3 / 2 →6S 1 / 2 transition, and radiate blue laser light with a wavelength of 459 nm 18 through the 7P 1 / 2 →6S 1 / 2 transition, thereby generating dual-wavelength blue laser light;

[0054] (4) The two pump lasers and the two blue laser beams emerging from the cesium atomic vapor cell 14 become spatially separated parallel light beams after passing through a lens; then the two pump lasers are blocked by the aperture 16, so as to obtain spatially separated dual-wavelength blue laser light with parallel output.

[0055] As Figure 2 shown, the four-wave mixing effect in this method mainly refers to: two near-infrared pump lasers with wavelengths of 852 nm and 921 nm respectively excite cesium atoms from the ground state 6S 1 / 2 to the high-energy state 6D 3 / 2 . According to the transition selection rule, cesium atoms can return to the ground state 6S 3 / 2 and 7P 1 / 2 through spontaneous emission. Since the transition probability of 6D 1 / 2 →7P 3 / 2 is much smaller than the transition probability of 7P 3 / 2(1 / 2) →6S 3 / 2(1 / 2) →6S 1 / 2 →6S 3 / 2 and the energy state 7P 3 / 2(1 / 2) between the energy states will have a large population inversion, and cesium atoms will undergo an amplified spontaneous emission process to generate long-wave infrared light of 15.6 μm (12.1 μm). This long-wave infrared light and the two near-infrared pump lasers act on cesium atoms to generate coherence between the energy state 7P 3 / 2(1 / 2) and the energy state 6S 1 / 2 , resulting in the occurrence of the four-wave mixing process of cesium atoms, and thus radiating coherent blue laser light with a wavelength of 455 nm (459 nm) through the 7P 3 / 2(1 / 2) →6S 1 / 2 transition.

[0056] Further, the method for adjusting the included angle between the two pump lasers entering the cesium atomic vapor cell 14 in step (2) includes the following steps:

[0057] S1. First, adjust the two pump lasers to be parallel; specifically, one of the pump lasers can be adjusted by the D-shaped mirror 12 so that the two pump lasers are arranged in parallel.

[0058] S2. The included angle between the two parallel pump lasers is adjusted by a lens, and the rear focal point of the lens is located at the center of the cesium atomic vapor cell 14, so as to ensure that the two pump lasers intersect at the center of the cesium atomic vapor cell 14.

[0059] S3. Keep the direction of one of the pump lasers passing through the center of the lens unchanged, and the other pump laser passes through by refraction from one side of the lens, so as to realize that the two pump lasers enter the cesium atomic vapor cell 14 at a set included angle. The size of the included angle can be adjusted by adjusting the distance between the two pump lasers while keeping the position of the lens unchanged. When using the D-shaped mirror 12, the distance can be directly adjusted by adjusting the position of the D-shaped mirror 12.

[0060] A device for generating spatially separated dual-wavelength blue laser light includes:

[0061] Laser A1, the laser A1 emits pump laser A with a wavelength of 852 nm. The pump laser A is divided into two beams after passing through the half-wave plate A2 and the polarization beam splitter prism A3. By rotating the half-wave plate A2, the light intensity ratio of the reflected light and the transmitted light can be adjusted. One beam is the reflected pump laser A entering the pump laser frequency monitoring system, and the other beam is the transmitted pump laser A. After passing through the half-wave plate B4 and the quarter-wave plate A5 (cooperating with each other), the pump laser A is prepared into a right-handed circular polarization state.

[0062] Laser B6, the laser B6 emits pump laser B with a wavelength of 921 nm. The pump laser B is divided into two beams after passing through the half-wave plate C7 and the polarization beam splitter prism B8. By rotating the half-wave plate C7, the light intensity ratio of the reflected light and the transmitted light can be adjusted. One beam is the reflected pump laser B entering the pump laser frequency monitoring system, and the other beam is the transmitted pump laser B. After passing through the mirror 9, the half-wave plate D10 and the quarter-wave plate B11 (cooperating with each other), the pump laser B is prepared into a right-handed circular polarization state. The pump laser B is reflected by the D-shaped mirror 12 and is parallel to the pump laser A. In practical applications or experiments, the D-shaped mirror 12 is fixed on a precision translation stage (prior art). By moving the position of the D-shaped mirror 12 through the precision translation stage, the distance between the 921 nm pump laser and the 852 nm pump laser can be precisely adjusted, so that the included angle θ between the two pump lasers when passing through the lens A13 and entering the cesium atomic vapor cell 14 can be precisely adjusted.

[0063] The pump laser A and the pump laser B pass through the lens A13 in parallel and enter the cesium atomic vapor cell 14 at a set angle. The center of the cesium atomic vapor cell 14 is located at the rear focal point of the lens A13, so as to ensure that the pump laser A and the pump laser B intersect at the center of the cesium atomic vapor cell 14. The pump laser A and the pump laser B excite a four-wave mixing process in the cesium atomic vapor cell 14, thereby generating blue light lasers with wavelengths of 455 nm and 459 nm and long-wave infrared light with wavelengths of 15.6 μm and 12.1 μm. A lens B15 and a diaphragm 16 are respectively arranged at intervals at the outlet end of the cesium atomic vapor cell 14. Among them, the 15.6 μm and 12.1 μm long-wave infrared light cannot penetrate the glass end face of the cesium atomic vapor cell 14. Therefore, the two pump lasers and the two blue light lasers emitted from the cesium atomic vapor cell 14 become spatially separated parallel light beams after passing through the lens B15, and then the two pump lasers are blocked by the diaphragm 16, thereby obtaining a spatially separated dual-wavelength blue light laser with parallel output, that is, the 455 nm blue light laser 17 and the 459 nm blue light laser 18.

[0064] Both end faces of the cesium atomic vapor cell 14 are coated with a broadband antireflection dielectric film of 400 nm to 1100 nm, which is used to reduce the reflection loss of the blue light laser on the end face of the vapor cell and avoid the back-and-forth reflection of the near-infrared pump laser between the two end faces of the vapor cell.

[0065] The cesium atomic vapor cell 14 is wrapped in multiple layers of μ-metal foil, which is used to reduce the interference of the external magnetic field.

[0066] The cesium atomic vapor cell 14 is fixed in the heating furnace 19, and the heating furnace 19 is connected to the temperature controller 20. The temperature controller 20 controls the temperature of the heating furnace 19 and thus controls the temperature of the cesium atomic vapor cell 14. Since the atomic number density in the cesium atomic vapor cell 14 depends on the temperature of the vapor cell, the atomic number density of the cesium atomic vapor cell 14 can be adjusted by the temperature controller 20.

[0067] In order to optimize the four-wave mixing efficiency, the propagation directions of the pump laser, the long-wave infrared light, and the blue light laser must satisfy the phase matching condition, and its expression is:

[0068] n 852 k 852 +n 921 k 921 =n 455 k 455 +n 15.6 k 15.6

[0069] n 852 k 852 +n 921 k 921 =n 459 k 459 +n 12.1 k12.1

[0070] In the formula, n 852 is the refractive index of the 852 nm pump laser, and k 852 is the vacuum wave vector of the 852 nm pump laser, and n 921 is the refractive index of the 921 nm pump laser, and k 921 is the vacuum wave vector of the 921 nm pump laser, and n 455 is the refractive index of the 455 nm blue laser, and k 455 is the vacuum wave vector of the 455 nm blue laser, and n 459 is the refractive index of the 459 nm blue laser, and k 459 is the vacuum wave vector of the 459 nm blue laser, and n 15.6 is the refractive index of the 15.6 μm long-wave infrared light, and k 15.6 is the vacuum wave vector of the 15.6 μm long-wave infrared light, and n 12.1 is the refractive index of the 12.1 μm long-wave infrared light, and k 12.1 is the vacuum wave vector of the 12.1 μm long-wave infrared light. For specific experimental conditions, it is necessary to precisely adjust the angle θ between the two pump lasers to find the working point of the optimal phase-matching condition.

[0071] The pump laser frequency monitoring system includes:

[0072] Laser C21, which emits a probe laser with a wavelength of 852 nm. The frequency of the probe laser scans near the hyperfine transition resonance frequency of 6S 1 / 2 (F = 4) → 6P 3 / 2 (F = 5). The probe laser is divided into two beams after passing through a half-wave plate E22 (the intensity ratio of the reflected light and the transmitted light can be adjusted by rotating the half-wave plate E22) and a polarization beam splitter prism C23:

[0073] One beam is the reflected probe laser A that enters a saturated absorption spectroscopy device composed of a beam splitter A24, a mirror A25, a cesium atomic vapor cell A26, and a beam splitter B27. The intensity of the probe laser A is measured by a photodetector A28, and the photodetector A28 is connected to a digital oscilloscope 42; the photodetector A28 is connected to the digital oscilloscope 42 through a BNC cable to monitor the saturated absorption spectrum of the probe laser, which is used to determine the detuning of the frequency of the probe laser relative to the hyperfine transition resonance frequency of 6S 1 / 2 (F = 4) → 6P 3 / 2 (F = 5).

[0074] The other beam is the transmitted probe laser B, which is further divided into two beams after passing through a half-wave plate F29 (the intensity ratio of the reflected light and the transmitted light can be adjusted by rotating the half-wave plate F29) and a polarization beam splitter prism D30:

[0075] A beam of transmitted probe laser C enters cesium atomic vapor cell B31, and the pump laser B (921 nm pump laser) reflected from polarization beam splitter B8 and then reflected from polarization beam splitter E32 enters cesium atomic vapor cell B31 along the opposite direction. The probe laser C (852 nm probe laser) and the pump laser B (921 nm pump laser) respectively excite the 6S 1 / 2 →6P 3 / 2 transition and 6P 3 / 2 →6D 3 / 2 transition to generate the electromagnetically induced transparency effect. The beam collector A33 is used to block the pump laser B (921 nm pump laser) reflected from polarization beam splitter D30; the photodetector B34 measures the light intensity of the probe laser C (852 nm probe laser) transmitted through polarization beam splitter E32, and the photodetector B34 is connected to the digital oscilloscope 42; the photodetector B34 is connected to the digital oscilloscope 42 through a BNC cable to monitor the electromagnetically induced transparency spectrum of the probe laser, so as to monitor the frequency of the 921 nm pump laser relative to 6P 3 / 2 (F = 5)→6D 3 / 2 the detuning of the (F = 5) hyperfine transition resonance frequency.

[0076] Another beam of reflected probe laser D passes through mirror B35, a half-wave plate G36 (the half-wave plate G36 is used to transform the 852 nm probe laser from vertical polarization to horizontal polarization, so that it can be transmitted through polarization beam splitter F37) and polarization beam splitter F37 and then enters cesium atomic vapor cell C38. The pump laser A (852 nm pump laser) reflected from polarization beam splitter A3 and then reflected from polarization beam splitter F37 enters cesium atomic vapor cell C38 along the same direction. The probe laser D (852 nm probe laser) and the pump laser A (852 nm pump laser) respectively excite different 6S 1 / 2 →6P 3 / 2 hyperfine transitions to generate the electromagnetically induced transparency effect. A polarization beam splitter G39 is provided at the output end of cesium atomic vapor cell C38. The beam collector B40 is used to block the pump laser A (852 nm pump laser) reflected from polarization beam splitter G39. The photodetector C41 measures the light intensity of the probe laser D (852 nm probe laser) transmitted through polarization beam splitter G39, and the photodetector C41 is connected to the digital oscilloscope 42. The photodetector C41 is connected to the digital oscilloscope 42 through a BNC cable to monitor the electromagnetically induced transparency spectrum of the probe laser, so as to monitor the frequency of the 852 nm pump laser relative to 6S 1 / 2 (F = 4)→6P 3 / 2 (F = 5) the detuning of the hyperfine transition resonance frequency.

[0077] The lasers A1, B6, and C21 adopt continuously tunable semiconductor lasers.

[0078] The key technologies of this application are as follows: (1) The 852-nm pump laser and the 921-nm pump laser simultaneously establish the coherence between the energy states 7P 3 / 2 and 6S 1 / 2 and between the energy states 7P 1 / 2 and 6S 1 / 2 to realize the generation of dual-wavelength blue laser; (2) Precisely adjust the phase matching condition of the four-wave mixing process to achieve the spatial separation of the pump laser and the blue laser while increasing the output power of the blue laser; (3) Adopt co-directional circularly polarized pump excitation to avoid the transfer of atomic population to other hyperfine energy states to the greatest extent and improve the four-wave mixing efficiency.

[0079] Experimental part:

[0080] Experimental parameters: The included angle between the 852-nm pump laser and the 921-nm pump laser when entering the cesium atomic vapor cell 14 is 2.82 degrees (θ = 2.82°), and the polarization states are both right-handed circular polarization. The powers are 50 mW and 26 mW respectively, and the spot diameters are 0.632 mm and 0.512 mm respectively. The temperature of the cesium atomic vapor cell is 115 °C. The detuning of the 921-nm pump laser with respect to the resonance frequency of the 6P 3 / 2 (F = 5) → 6D 3 / 2 hyperfine transition is -500 MHz. When the detunings of the 852-nm pump laser with respect to the resonance frequencies of the 6S 1 / 2 (F = 4) → 6P 3 / 2 (F = 5) hyperfine transitions are 420 MHz and 190 MHz respectively, the output powers of the 455-nm and 459-nm blue lasers reach the maximum values, which are 66 μW and 28 μW respectively. As Figure 3 shown is the blue laser spot recorded by the CCD camera; as Figure 4 shown is the variation curve of the blue laser intensity with the detuning of the 852-nm pump laser frequency; as Figure 5 shown is the variation curve of the blue laser power with the 852-nm pump laser power when the 921-nm pump laser power is maintained at 26 mW; as Figure 6 shown is the variation curve of the blue laser power with the 921-nm pump laser power when the 852-nm pump laser power is maintained at 50 mW; as Figure 7 shown is the variation curve of the blue laser power with the temperature of the cesium atomic vapor cell.

[0081] Through the above experiments, it is concluded that the method and device for generating spatially separated dual-wavelength blue laser in this application are feasible, and it is possible to simultaneously generate dual-wavelength blue lasers with wavelengths of 455 nm and 459 nm that are spatially separated, directly corresponding to the 6S 1 / 2 →7P 3 / 2 absorption line and 6S 1 / 2 →7P 1 / 2 absorption line, and the output power of the blue laser is high, and the transition frequency of cesium atoms is highly stable.

[0082] The above specific embodiments cannot be used as a limitation on the protection scope of the present invention. For those skilled in the art of this technology, any alternative improvement or transformation made to the embodiments of the present invention falls within the protection scope of the present invention.

[0083] Where the present invention is not described in detail, it is the well-known technology of those skilled in the art of this technology.

Claims

1. A method for generating spatially separated dual-wavelength blue laser, characterized in that: The following steps are involved: (1) obtaining an 852 nm pump laser and a 921 nm pump laser, and processing the 852 nm pump laser and the 921 nm pump laser respectively so that the two pump lasers have circular polarizations with the same rotation direction; (2) Two pump laser beams enter the cesium atomic vapor cell, and the angle between the two pump laser beams entering the cesium atomic vapor cell is θ, 2°≤θ≤3°, and the two pump laser beams intersect at the center of the cesium atomic vapor cell; (3) 852nm pump laser and 921nm pump laser stimulate four-wave mixing process in cesium atomic vapor chamber, through 7P 3 / 2 →6S 1 / 2 The transition radiates a 455nm blue laser, which is then 1 / 2 →6S 1 / 2 The transition radiates blue laser with a wavelength of 459nm, thus producing dual-wavelength blue laser; (4) The two pump laser beams and two blue laser beams emitted from the cesium atomic vapor chamber are transformed into spatially separated parallel beams after passing through a lens; the two pump laser beams are then shielded by an aperture, thereby obtaining parallel output spatially separated dual-wavelength blue laser beams.

2. A method for generating spatially separated dual-wavelength blue laser according to claim 1, characterized in that: Furthermore, the method for adjusting the angle between the two pump laser beams entering the cesium atomic vapor chamber in step (2) comprises the following steps: S1, first adjust the two pump laser beams to be parallel; S2. The two parallel pump laser beams are adjusted at an angle through a lens, and the rear focus of the lens is located at the center of the cesium atomic vapor cell, thereby ensuring that the two pump laser beams intersect at the center of the cesium atomic vapor cell; S3. Pass one of the pump laser beams through the center of the lens while keeping the direction unchanged, and refract the other pump laser beam through one side of the lens, so that the two pump laser beams enter the cesium atomic vapor chamber at a set angle. The size of the angle can be adjusted by adjusting the distance between the two pump laser beams.

3. A device for generating spatially separated dual-wavelength blue laser, characterized in that: include: Laser A, the laser A emits a pump laser A with a wavelength of 852nm, the pump laser A is divided into two beams after passing through a half wave plate A and a polarization beam splitter prism A, one beam is the reflected pump laser A entering the pump laser frequency monitoring system, and the other beam is the transmitted pump laser A passing through a half wave plate B and a quarter wave plate A to prepare the pump laser A into a right-handed circular polarization state; A laser B, wherein the laser B emits a pump laser B with a wavelength of 921 nm, and the pump laser B is divided into two beams after passing through a half-wave plate C and a polarization beam splitter prism B. One beam is the reflected pump laser B that enters the pump laser frequency monitoring system, and the other beam is the transmitted pump laser B that is prepared into a right-handed circular polarization state through a reflector, a half-wave plate D and a quarter-wave plate B. The pump laser B is reflected by a D-shaped reflector and is parallel to the pump laser A; The pump laser A and the pump laser B enter the cesium atom vapor chamber in parallel through the lens A at a set angle, the center of the cesium atom vapor chamber is located at the rear focus of the lens A, so as to ensure that the pump laser A and the pump laser B intersect at the center of the cesium atom vapor chamber, the pump laser A and the pump laser B excite a four-wave mixing process in the cesium atom vapor chamber, so as to generate blue light lasers with wavelengths of 455nm and 459nm and long-wave infrared light with wavelengths of 15.6μm and 12.1μm, and the lens B and the aperture are respectively arranged at intervals at the outlet end of the cesium atom vapor chamber, wherein the long-wave infrared light of 15.6μm and 12.1μm cannot pass through the glass end face of the cesium atom vapor chamber, and the two pump lasers and the two blue light lasers emitted from the cesium atom vapor chamber are transformed into spatially separated parallel light beams after passing through the lens B, and then the two pump lasers are shielded by the aperture, so as to obtain spatially separated dual-wavelength blue light lasers with parallel output.

4. The device for generating spatially separated dual-wavelength blue laser according to claim 3, characterized in that: The two end surfaces of the cesium atomic vapor chamber are plated with a 400nm-1100nm wide-band anti-reflection dielectric film.

5. The device for generating spatially separated dual-wavelength blue laser according to claim 3 or 4, characterized in that: The cesium atom vapor cell is wrapped in multiple layers of μ-metal foil.

6. The device for generating spatially separated dual-wavelength blue laser according to claim 5, characterized in that: The cesium atomic vapor chamber is fixed in a heating furnace, and the heating furnace is connected to a temperature controller.

7. The device for generating spatially separated dual-wavelength blue laser according to claim 6, characterized in that: The propagation directions of the pump laser, long-wave infrared light and blue laser must satisfy the phase matching condition, which is expressed as: n 852 k 852 +n 921 k 921 =n 455 k 455 +n 15.6 k 15.6 n 852 k 852 +n 921 k 921 =n 459 k 459 +n 12.1 k 12.1 Where n 852 is the refractive index of the 852nm pump laser, k 852 is the vacuum wave vector of the 852nm pump laser, n 921 is the refractive index of the 921nm pump laser, k 921 is the vacuum wave vector of the 921nm pump laser, n 455 is the refractive index of 455nm blue laser, k 455 is the vacuum wave vector of 455nm blue laser, n 459 is the refractive index of 459nm blue laser, k 459 is the vacuum wave vector of 459nm blue laser, n 15.6 is the refractive index of 15.6μm long-wave infrared light, k 15.6 is the vacuum wave vector of 15.6 μm long-wave infrared light, n 12.1 is the refractive index of 12.1 μm long-wave infrared light, k 12.1 It is the vacuum wave vector of 12.1μm long-wave infrared light.

8. The device for generating spatially separated dual-wavelength blue laser according to claim 3 or 7, characterized in that: The pump laser frequency monitoring system comprises: Laser C emits a probe laser with a wavelength of 852nm, which is divided into two beams after passing through a half-wave plate E and a polarization beam splitter prism C: A beam of probe laser A that is reflected enters a saturation absorption spectrometer consisting of a spectroscope A, a reflector A, a cesium atomic vapor chamber A and a spectroscope B. The light intensity of the probe laser A is measured by a photodetector A, and the photodetector A is connected to a digital oscilloscope. The other beam is the transmitted probe laser B which is split into two beams by the half-wave plate F and the polarization beam splitter prism D: A beam of probe laser C is transmitted into the cesium atomic vapor chamber B, and the pump laser B is reflected from the polarization beam splitter prism B and then reflected from the polarization beam splitter prism E and enters the cesium atomic vapor chamber B in the opposite direction. The probe laser C and the pump laser B excite 6S 1 / 2 →6P 3 / 2 Transition and 6P 3 / 2 →6D 3 / 2 The transition produces an electromagnetically induced transparent effect, and the beam collector A is used to block the pump laser B reflected from the polarization beam splitter prism D; the photodetector B measures the intensity of the probe laser C transmitted from the polarization beam splitter E, and the photodetector B is connected to a digital oscilloscope; The other beam is the reflected probe laser D, which passes through the reflector B, half-wave plate G and polarization beam splitter F and then enters the cesium atomic vapor chamber C. The pump laser A, which is reflected from the polarization beam splitter A and then reflected from the polarization beam splitter F, enters the cesium atomic vapor chamber C along the same direction. The probe laser D and the pump laser A excite 6S 1 / 2 →6P 3 / 2 Different hyperfine transitions produce electromagnetically induced transparency effect. A polarization beam splitter prism G is provided at the output end of the cesium atomic vapor cell C. The beam collector B is used to block the pump laser A reflected from the polarization beam splitter prism G. The photodetector C measures the intensity of the probe laser D transmitted from the polarization beam splitter prism G. The photodetector C is connected to a digital oscilloscope.

9. The device for generating spatially separated dual-wavelength blue laser according to claim 8, characterized in that: The laser A and the laser B are continuously tunable semiconductor lasers.

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