Multi-wave mixing signal generating device and spectrum, light spot generating device and method thereof

Abstract

The present invention proposes a multi-wave mixing signal based on a vector light field and its spectrum, spot generating device and generating method, wherein the multi-wave mixing signal generating device includes a laser, a vector light generating device, a polarizer, a beam expander, a first spatial light filter, a focusing lens and an atomic molecular vapor absorption chamber arranged in the same optical path. The laser output laser beam is passed through the vector light generating device to generate a vector light field whose polarization state is distributed in a specific regular pattern in the beam cross section, and then a plurality of parallel distributed polarized lights of the same frequency and phase are generated through the polarizer. After filtering out one or more of the beams, a multi-wave mixing signal output is generated in the atomic molecular vapor absorption chamber based on multi-order nonlinear effects. The device described in the present invention has strong versatility, and the device has a simple structure, is easy to control, has a reasonable design, is low in cost and easy to promote, and has strong practicality.

Description

Technical Field

[0001] The present invention belongs to the technical field of nonlinear optical applications, and specifically relates to a multi-wave mixing signal generating device based on a vector light field, a multi-wave mixing signal spectrum generating device and a generating method, and a multi-wave mixing signal spot generating device and a generating method. Background Art

[0002] Four-wave mixing is an important third-order nonlinear process. Three incident light beams interact with the sample at the same time. Under the condition of phase matching, a fourth light beam is generated, which is called a four-wave mixing (FWM) signal. If the three incident light beams have equal frequencies, it is called degenerate four-wave mixing (DFWM). DFWM is a high-sensitivity, high-resolution, and high-signal-to-noise ratio spectroscopy technology. In the prior art, the three beams of light in the traditional DFWM device are independent of each other, the device is complex, difficult to control, and susceptible to external interference. The higher-order multi-wave mixing process based on this is more complex, which brings great difficulty to the experiment. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a multi-wave mixing signal generating device based on vector light field, a multi-wave mixing signal spectrum generating device and generating method, and a multi-wave mixing signal spot generating device and generating method in view of the deficiencies in the above-mentioned prior art. The multi-wave mixing signal generating device utilizes the extinction characteristics of column vector light through a polarizer to obtain multiple beams of parallel and symmetrically distributed in-phase linear polarized light, which are then converged in a sample through a focusing lens to generate a degenerate four-wave mixing signal (DFWM), and other more complex multi-wave mixing signals can be obtained by changing the topological charge number of the column vector light. The device has strong versatility, simple structure, easy control, reasonable design, low cost, and easy promotion, and strong practicality.

[0004] The technical solution adopted by the present invention to solve the above technical problems is as follows:

[0005] A multi-wave mixing signal generating device based on a vector light field comprises: a laser 1, a vector light generating device 2, a polarizer 3, a beam expander 4, a first spatial light filter 5, a focusing lens 6 and an atomic molecular vapor absorption chamber 7, wherein the laser 1, the vector light generating device 2, the polarizer 3, the beam expander 4, the first spatial light filter 5, the focusing lens 6 and the atomic molecular vapor absorption chamber 7 are sequentially arranged on the same optical path, and the laser beam output by the laser generates a vector light field whose polarization state is distributed in a specific regular pattern in the beam cross section after passing through the vector light generating device 2, and the vector light field After passing through the polarizer 3, a plurality of parallel-distributed polarized lights of the same frequency and phase are generated. After being expanded by the beam expander 4, the plurality of parallel-distributed polarized lights of the same frequency and phase are incident on the first spatial light filter 5. After one or more of the polarized lights of the same frequency and phase are filtered out by the first spatial light filter 5, the remaining plurality of polarized lights of the same frequency and phase that meet the multi-wave mixing conditions are formed. The remaining plurality of polarized lights of the same frequency and phase are focused on the atomic and molecular vapor absorption chamber 7 through the focusing lens 6, and a multi-wave mixing signal output is generated in the atomic and molecular vapor absorption chamber 7 based on the multi-order nonlinear effect.

[0006] Further, according to the multi-wave mixing signal generating device described in the present invention, the laser beam output by the laser is a linearly polarized beam, the laser wavelength is at the resonant absorption wavelength of the atomic and molecular vapor absorption chamber, and the vector light generating device 2 is composed of a plurality of half-wave plates, and the fast axis directions of each half-wave plate are arranged in order according to a specific rule. When the laser beam passes through the vector light generating device 2, the polarization direction of the corresponding beam portion passing through each half-wave plate is deflected at a corresponding angle based on the fast axis direction of the half-wave plate, so that after the laser beam passes through the vector light generating device 2, the polarization directions of different beam portions are deflected at different angles corresponding to the fast axis directions of different half-wave plates, and finally a vector light field is generated in which the polarization state is distributed in a specific rule in the cross section of the beam, and the specific rule corresponds to the specific arrangement rule of the fast axis directions of each half-wave plate in the vector light generating device 2.

[0007] Further according to the multi-wave mixing signal generating device described in the present invention, the vector light generating device 2 is a cylindrical vector light generating device, and the cylindrical vector light generating device is a vortex wave plate spliced ​​from multiple half-wave plates, and the fast axis direction of each half-wave plate is uniformly arranged according to the rule of deflection angle mπ around a circle; the laser beam output by the laser passes through the cylindrical vector light generating device to generate a cylindrical vector light field whose polarization state is axially symmetrical or rotationally symmetrically distributed in the cross-section of the beam, and the deflection angle of the polarization direction of the cylindrical vector light field around the circle is 2mπ, where m represents the topological charge number, and the cylindrical vector light generating device can generate cylindrical vector light fields with a variety of topological charges.

[0008] Further according to the multi-wave mixing signal generating device described in the present invention, the polarizer 3 is a linear polarizer, and the vector light field generates multiple beams of parallel distributed linear polarized light with the same frequency, phase and polarization after passing through the polarizer 3. The beam expander 4 expands the linear polarized light to the first spatial light filter 5, and makes one or more of the linear polarized light beams incident on the specific filtering position corresponding to the first spatial light filter 5. The first spatial light filter 5 has a filtering function at its specific position, and the remaining multiple beams of parallel distributed linear polarized light with the same frequency, phase and polarization after passing through the first spatial light filter 5 meet the multi-wave mixing conditions of the atomic and molecular vapor absorption chamber 7, wherein the atomic and molecular vapor absorption chamber 7 generates multi-wave mixing signals based on third-order, fifth-order or higher-order nonlinear effects.

[0009] Further, according to the multi-wave mixing signal generating device described in the present invention, the multi-wave mixing signal generating device is a degenerate four-wave mixing signal generating device, wherein the laser is a continuously tunable ring titanium sapphire laser, and the vector light generating device 2 is a column vector light generating device with a topological charge number equal to two. The laser beam output by the laser generates a column vector light field whose polarization state is axially symmetrically distributed in the beam cross section after passing through the column vector light generating device. The column vector light field generates four parallel distributed linear polarized lights with the same frequency, phase and polarization after passing through the polarizer 3. After one of the beams is filtered out by the first spatial light filter 5, the remaining three parallel distributed linear polarized lights with the same frequency, phase and polarization are focused and incident on the atomic and molecular vapor absorption chamber 7. The atomic and molecular vapor absorption chamber 7 is an atomic and molecular vapor absorption chamber containing rubidium vapor. The incident three parallel distributed linear polarized lights with the same frequency, phase and polarization generate degenerate four-wave mixing signals in the atomic and molecular vapor absorption chamber 7 based on the third-order nonlinear effect.

[0010] Further, according to the multi-wave mixing signal generating device described in the present invention, the multi-wave mixing signal generating device is a degenerate six-wave mixing signal generating device, wherein the laser is a continuously tunable ring titanium sapphire laser, and the vector light generating device 2 is a column vector light generating device with a topological charge number equal to three. The laser beam output by the laser generates a column vector light field whose polarization state is axially symmetrically distributed in the cross section of the beam after passing through the column vector light generating device. The column vector light field generates six beams of parallel distributed linear polarized light with the same frequency, phase and polarization after passing through the polarizer 3. After one beam is filtered out by the first spatial light filter 5, the remaining five beams of parallel distributed linear polarized light with the same frequency, phase and polarization are focused and incident on the atomic and molecular vapor absorption chamber 7. The atomic and molecular vapor absorption chamber 7 is an atomic and molecular vapor absorption chamber containing rubidium vapor. The incident five beams of parallel distributed linear polarized light with the same frequency, phase and polarization generate a degenerate six-wave mixing signal in the atomic and molecular vapor absorption chamber 7 based on the fifth-order nonlinear effect.

[0011] A multi-wave mixing signal spectrum generating device comprises: the multi-wave mixing signal generating device described in the present invention, and also comprises a second spatial light filter 8, a photodetector 9 and an oscilloscope 10, wherein the second spatial light filter 8 is arranged on the optical path behind the atomic molecular vapor absorption chamber 7 in the multi-wave mixing signal generating device, and filters out other light beam signals except the multi-wave mixing signal, the photodetector 9 is arranged directly behind the second spatial light filter 8, and is used to detect the multi-wave mixing signal, the oscilloscope 10 is connected to the photodetector 9, and is used to display the multi-wave mixing signal detected by the photodetector 9, and when the wavelength of the laser beam is adjusted, the intensity change of the multi-wave mixing signal can be recorded by the oscilloscope to obtain the spectrum of the multi-wave mixing signal.

[0012] A method for obtaining a multi-wave mixing signal spectrum based on the multi-wave mixing signal spectrum generating device of the present invention comprises the following steps:

[0013] Step 1: outputting the remaining incident light beam and the multi-wave mixing signal through the multi-wave mixing signal generating device;

[0014] Step 2: filtering out the remaining incident light beam through a second spatial light filter, so that the multi-wave mixing signal is incident on the photoelectric detector;

[0015] Step 3: Adjust the wavelength of the laser beam, record the intensity change of the multi-wave mixing signal through an oscilloscope, and obtain the spectrum of the multi-wave mixing signal.

[0016] A multi-wave mixing signal spot generating device comprises: the multi-wave mixing signal generating device of the present invention, and also comprises an imaging device 11, wherein the imaging device 11 is arranged on the rear optical path of the atomic and molecular vapor absorption chamber 7 in the multi-wave mixing signal generating device, the multi-wave mixing signal and the remaining incident light are incident on the imaging device together, and a spot diagram including the multi-wave mixing signal is obtained in the imaging device by changing the topological charge number of the vector light field.

[0017] A method for obtaining a multi-wave mixing signal spot based on the multi-wave mixing signal spot generating device of the present invention comprises the following steps:

[0018] Step 1: outputting the remaining incident light beam and the multi-wave mixing signal through the multi-wave mixing signal generating device;

[0019] Step 2, the remaining incident light beam and the multi-wave mixing signal are jointly injected into the imaging device;

[0020] Step 3: Adjust the vector light generating device to change the topological charge of the vector light field, and obtain a light spot diagram including a multi-wave mixing signal in the imaging device.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] 1) The present invention is the first to innovatively utilize the extinction characteristics of vector light through a polarizer to obtain multiple beams of parallel and symmetrically distributed linearly polarized light of the same frequency and phase, which are converged in the sample through a focusing lens to generate a degenerate multi-wave mixing signal. Since the incident multiple beams of light come from the same beam of vector light, their relative positions are fixed. After focusing with the lens, the phase matching condition is met. As long as the polarization distribution of the vector light itself is not affected, the generated signal quality is stable and has strong stability. This is a completely new multi-wave mixing signal generation technology that is completely unavailable in the prior art.

[0023] 2) The present invention can realize various multi-wave mixing processes by changing the topological charge number of the cylindrical vector light, without changing other experimental devices, and has strong versatility.

[0024] 3) The device of the present invention has a simple structure, convenient operation, reasonable design, low cost, easy promotion and strong practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the fast axis direction distribution of each half-wave plate in the vortex wave plate with topological charge m=1;

[0026] Figure 2 Schematic diagram of the polarization direction distribution of radially polarized light;

[0027] Figure 3 Schematic diagram of polarization direction distribution of angular polarized light;

[0028] Figure 4 The deflection angle distribution of the polarization direction of cylindrical vector light with topological charge numbers of m=2, m=3 and m=4 around the hollow ring and the distribution diagram of the number of beams split after passing through the linear polarizer;

[0029] Figure 5 It is a schematic diagram of the energy levels of degenerate four-wave mixing based on the third-order nonlinear effect;

[0030] Figure 6 It is a schematic diagram of the energy levels of degenerate six-wave mixing based on the fifth-order nonlinear effect;

[0031] Figure 7 It is a schematic structural diagram of the multi-wave mixing signal spectrum generating device based on a single beam vector light field according to the present invention;

[0032] Figure 8 It is a schematic structural diagram of the device for generating a multi-wave mixing signal spot based on a single beam vector light field according to the present invention;

[0033] Fig. 9This is the four-wave mixing signal spot diagram obtained in Example 1;

[0034] Fig.10 This is a spectrum diagram of the four-wave mixing signal obtained in Example 1;

[0035] Fig.11 This is the six-wave mixing signal spot diagram obtained in Example 2;

[0036] Description of the reference numerals in the figures:

[0037] 1—Laser; 2—Vector light generating device; 3—Polarizer; 4—Beam expander; 5—First spatial light filter; 6—Focusing lens; 7—Atomic and molecular vapor absorption chamber; 8—Second spatial light filter; 9—Photodetector; 10—Oscilloscope; 11—Imaging device. DETAILED DESCRIPTION

[0038] The technical solution of the present invention is described in detail below in conjunction with the accompanying drawings so that those skilled in the art can understand the present invention more clearly, but the protection scope of the present invention is not limited thereby.

[0039] First, the professional and technical terms involved in the present invention are explained.

[0040] Vector light refers to a light field with uneven polarization state distribution on the cross section of the light beam. There are many ways to generate vector light. A relatively simple method is to generate it by passing linearly polarized Gaussian light through a vortex wave plate. The vortex wave plate is composed of multiple half-wave plates. The fast axis directions of each half-wave plate are arranged in an orderly manner. As a vector light generating device, it causes the polarization direction of the cross section of the linearly polarized Gaussian light to deflect at different angles at different positions. Figure 1 is a vortex wave plate with topological charge m=1, where the direction of the arrow represents the fast axis direction of each fan-shaped half-wave plate. Gaussian light passes through the center of the vortex wave plate. The fast axis direction of the wave plate passed through each part of the cross section is different, and the polarization direction of the linearly polarized light is deflected at different angles (twice the deflection angle of the half-wave plate fast axis), resulting in the following Figure 2 The radially polarized light shown Figure 3 The angular polarized light shown and mixed light of other linear polarization states are called mixed polarized light, and the present invention uses mixed polarized light.

[0041] Cylindrical vector light refers to: a special light field in which the polarization state is distributed in an axially symmetrical or rotationally symmetrical manner in the cross section of the light beam. According to the different distributions of the polarization vector, it can be mainly divided into radially polarized light, angularly polarized light and mixed polarized light. Cylindrical vector light can selectively change the shape of the light spot when passing through a polarizer, and can further divide a beam of light into multiple beams of parallel light. The topological charge is used to represent the deflection angle of the polarization direction in the cylindrical vector light. The deflection angle is expressed as 2mπ. The topological charge m of radial and angular polarized light is 1, indicating that the polarization direction of the radial or angular polarized light is deflected by a total of 2π angles around the hollow ring. If the topological charge m is 2, the polarization direction of the cylindrical vector light is deflected by a total of 4π angles around the hollow ring. The number of beams split after the cylindrical vector light passes through the polarizer is 2m, attached. Figure 4 The deflection angle distribution of the polarization direction of cylindrical vector light with topological charge m=2, m=3 and m=4 around a hollow ring and the distribution diagram of the number of light beams split after passing through the linear polarizer are given.

[0042] Four-wave mixing is a third-order nonlinear effect. Three beams of incident light interact with the sample at the same time. Under the condition of phase matching, a fourth beam of light is generated, which is called a four-wave mixing signal. If the frequencies of the incident light are equal, it is called degenerate four-wave mixing. Degenerate six-wave mixing is a fifth-order nonlinear effect. The incident light is increased to five beams and is generated when phase matching is met. At the atomic resonance wavelength of the sample, the signal is significantly enhanced. At the same time, when the polarization directions of the incident light are the same, the signal is the strongest, so the efficiency of the device of the present invention in generating signals is relatively high. Appendix Figure 5 and 6 The energy level diagrams for degenerate four-wave mixing and degenerate six-wave mixing are given respectively, where E4 and E6 shown by the dotted lines are the generated four-wave mixing signals and six-wave mixing signals respectively.

[0043] The following is combined with Figure 7 and attached Figure 8 The structure and working principle of the multi-wave mixing signal generating device based on a single beam vector light field of the present invention are described in detail. Figure 7 and attached Figure 8 As shown, the multi-wave mixing signal generating device described in the present invention includes: a laser 1 for generating a Gaussian beam, a vector light generating device 2, a polarizer 3, a beam expander 4, a first spatial light filter 5, a focusing lens 6 and an atomic molecular vapor absorption chamber 7; the multi-wave mixing signal spectrum generating device in the present invention further includes a second spatial light filter 8, a photodetector 9 and an oscilloscope 10; the multi-wave mixing signal spot generating device in the present invention further includes an imaging device; wherein the laser 1, the vector light generating device 2, the polarizer 3, the beam expander 4, the first spatial light filter 5, the focusing lens 6, the atomic molecular vapor absorption chamber 7 and the second spatial light filter 8 are arranged in sequence on the same optical path.

[0044] The Gaussian beam generated by the laser is preferably a linearly polarized Gaussian beam or a Gaussian beam that has been linearly polarized in the light source. Further preferably, the laser is a continuously tunable ring titanium sapphire laser; the wavelength of the laser beam generated by the laser is at the absorption wavelength of the atomic and molecular vapor absorption chamber.

[0045] The vector light generating device 2 can deflect the polarization direction of the Gaussian light at different positions in the cross section at different angles. Preferably, the vector light generating device is a column vector light generating device, which has a vortex wave plate structure and is composed of a plurality of half-wave plates, and the fast axis directions of the half-wave plates are arranged in an orderly manner; further preferably, the topological charge number m of the column vector light generating device is 2.

[0046] The polarizer 3 is preferably a linear polarizer.

[0047] The beam expansion ratio of the beam expander 4 can meet the filtering requirements of the first spatial light filter.

[0048] The first spatial light filter 6 performs filtering according to the positional relationship, similar to a stop.

[0049] The atomic and molecular vapor absorption chamber 7 is used as a saturable absorption sample cell, and preferably uses an atomic and molecular vapor absorption chamber containing rubidium vapor, so the laser wavelength should be at the resonant absorption wavelength of the sample atoms, so that atomic resonance occurs in the sample cell after the laser beam is incident, and the signal is significantly enhanced. The atomic and molecular vapor absorption chamber 7 can also be other alkali metal atoms, but rubidium is more commonly used because it can produce atomic vapor of appropriate concentration in a vacuum state at above 20°C, which is conducive to the generation of signals.

[0050] In the multi-wave mixing signal spectrum generating device of the present invention, as shown in the attached Figure 7 As shown, the device disposed behind the atomic and molecular vapor absorption chamber 7 is attached Figure 7 The second spatial optical filter 8, the photodetector 9 and the oscilloscope 10 are shown in the figure. In this case, the photodetector is a silicon photodetector connected to the oscilloscope. The multi-wave mixing signal spot generating device of the present invention also includes the following Figure 8 In the imaging device shown, the laser, the vector light generating device, the polarizer, the beam expander, the first spatial light filter, the focusing lens and the atomic molecular vapor absorption chamber are sequentially arranged on the same optical path, and the signal light and the incident light beam enter the imaging device at the same time; the imaging device includes a CCD camera or a CMOS camera.

[0051] When the multi-wave mixing device based on a single-beam vector light field of the present invention is working, the laser beam generated by the laser generates a vector light field whose polarization state is distributed in a specific regular pattern in the cross section of the beam after passing through the vector light generating device 2. Preferably, a column vector light generating device is used to generate a column vector light field whose polarization state is distributed in an axially symmetrical or rotationally symmetrical manner in the cross section of the beam. The column vector light field is split into 2m beams of parallel and symmetrically distributed linearly polarized light of the same frequency and phase after passing through the linear polarizer 3. The linearly polarized light is expanded to the first spatial light filter 5 through a beam expander. One or several linearly polarized lights at a specific position are filtered out by the first spatial light filter 5. Then, the remaining light beams are converged into the sample pool of the atomic and molecular vapor absorption chamber 7 through the focusing lens. Based on third-order, fifth-order or higher-order nonlinear effects, three, five or more incident lights interact with the sample at the same time to generate mixing signals under the condition of satisfying phase matching. In the attached Figure 7 In the device structure shown, after the second spatial light filter filters out the remaining incident light beam at the predetermined position, the generated mixing signal enters the photodetector, and the photodetector is connected to an oscilloscope, and the oscilloscope is used to record the intensity change of the multi-wave mixing signal to obtain the multi-wave mixing signal spectrum; in the attached Figure 8 In the device structure shown, the generated mixing signal enters the imaging device, and by changing the vector light beam topological charge, a spot pattern can be obtained in the imaging device.

[0052] The present invention also provides a method for generating a multi-wave mixing signal spectrum using the above-mentioned device, comprising the following steps:

[0053] Step 1, obtaining a Gaussian beam from a laser, generating a cylindrical vector beam through a vector light generating device, and obtaining a plurality of symmetrically distributed linearly polarized lights through a polarizer, filtering out one or more linearly polarized lights through the first spatial light filter, and focusing the linearly polarized lights through the focusing lens in a sample pool to generate a multi-wave mixing signal;

[0054] Step 2: filtering the incident light through a second spatial light filter, so that the multi-wave mixing signal light is incident on the photodetector;

[0055] Step 3: Adjust the wavelength of the incident light beam, record the intensity change of the multi-wave mixing signal through the oscilloscope, and obtain the multi-wave mixing signal spectrum.

[0056] Furthermore, the present invention also provides a method for generating a multi-wave mixing signal spot pattern using the above-mentioned device, comprising the following steps:

[0057] Step 1, obtaining a Gaussian beam from a laser, generating a cylindrical vector beam through a vector light generating device, and obtaining a plurality of symmetrically distributed linearly polarized lights through a polarizer, filtering out one or more linearly polarized lights through the first spatial light filter, and focusing the linearly polarized lights through the focusing lens in a sample pool to generate a multi-wave mixing signal;

[0058] Step 2: the multi-wave mixing signal and the incident light are incident on an imaging device together;

[0059] Step 3: Adjust the vector light generating device, change the topological charge of the vector light beam, and obtain a spot pattern in the imaging device.

[0060] The application examples of the present invention are further given below.

[0061] Example 1

[0062] The method for generating a degenerate four-wave mixing signal and its spectrum and light spot by using the device of the present invention is as follows: first, a Gaussian beam is obtained from a laser 1, and the Gaussian beam is generated by a vector light generating device 2 with a topological charge number of 2 (m=2). Figure 4 The cylindrical vector beam corresponding to m=2, the cylindrical vector beam passes through the polarizer 3 to obtain four symmetrically distributed linear polarized lights as shown in the attached figure Fig. 9 (a), the four linearly polarized lights are filtered out by the first spatial light filter 5 and one of them is as shown in the attached figure. Fig. 9 As shown in (b), the remaining three beams are focused by the focusing lens 6 into the atomic and molecular vapor absorption chamber containing rubidium vapor, and a degenerate four-wave mixing signal is generated based on the third-order nonlinear effect, as shown in FIG. Fig. 9 (c) as shown.

[0063] get Fig. 9 (c) After the DFWM signal is shown, if you want to further observe the four-wave mixing signal spectrum, you can Figure 7 As shown, a second spatial optical filter 8, a photodetector 9 and an oscilloscope 10 are sequentially arranged behind the atomic and molecular vapor absorption chamber 7. After the second spatial optical filter 8 filters out the three remaining incident lights, the generated degenerate four-wave mixing signal light is incident on the photodetector 9. At this time, by adjusting the wavelength of the incident light beam generated by the laser, the intensity change of the multi-wave mixing signal can be recorded by the oscilloscope 10 to obtain a four-wave mixing signal spectrum diagram, as shown in FIG. Fig.10 As shown, this spectrum generation method is also applicable to the multi-wave mixing signal described later.

[0064] Or get Fig. 9 (c) After the DFWM signal is shown, if you want to further observe the spot pattern, you can Figure 8As shown, an imaging device 11 is arranged behind the atomic and molecular vapor absorption chamber 7, and the four-wave mixing signal and the incident light are incident into the imaging device together. By adjusting the vector light generating device and changing the vector light beam topological charge, a light spot diagram can be obtained in the imaging device. This light spot generating method is also applicable to the multi-wave mixing signal described later.

[0065] Example 2

[0066] The method for obtaining a degenerate six-wave mixing signal by using the device of the present invention is as follows: first, a Gaussian beam is obtained from a laser 1, and the Gaussian beam is generated by a vector light generating device 2 with a topological charge number of 3 (m=3). Figure 4 The cylindrical vector beam corresponding to m=3, the cylindrical vector beam passes through the polarizer 3 to obtain six symmetrically distributed linear polarized lights as shown in the attached figure. Fig.11 (a), the six linearly polarized lights are filtered out by the first spatial light filter 5 and one of them is as shown in the attached figure. Fig.11 As shown in (b), the remaining five beams are focused by the focusing lens 6 into the atomic and molecular vapor absorption chamber containing rubidium vapor, and a degenerate six-wave mixing signal is generated based on the fifth-order nonlinear effect, as shown in FIG. Fig.11 (c) as shown.

[0067] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent structural change made to the above embodiment based on the technical essence of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A multi-wave mixing signal generating device based on vector light field, characterized in that: include: A laser (1), a vector light generating device (2), a polarizer (3), a beam expander (4), a first spatial light filter (5), a focusing lens (6) and an atomic and molecular vapor absorption chamber (7); the laser (1), the vector light generating device (2), the polarizer (3), the beam expander (4), the first spatial light filter (5), the focusing lens (6) and the atomic and molecular vapor absorption chamber (7) are arranged in sequence on the same optical path; the laser beam output by the laser generates a vector light field whose polarization state is distributed in a specific regular pattern in the beam cross section after passing through the vector light generating device (2); the vector light field generates a plurality of parallel-distributed polarized lights of the same frequency and phase after passing through the polarizer (3); the plurality of parallel-distributed polarized lights of the same frequency and phase are expanded by the beam expander (4) and incident on the first spatial light filter (5); one or more of the beams of the same frequency and phase are filtered out by the first spatial light filter (5). After the phase polarized light is generated, a plurality of remaining beams of polarized light with the same frequency and phase that meet the multi-wave mixing condition are formed. The remaining plurality of polarized light with the same frequency and phase are focused on the atomic molecular vapor absorption chamber (7) through a focusing lens (6), and a multi-wave mixing signal output is generated in the atomic molecular vapor absorption chamber (7) based on a multi-order nonlinear effect; the vector light generating device (2) is a column vector light generating device, and the column vector light generating device is a vortex wave plate formed by splicing a plurality of half-wave plates, and the fast axis direction of each half-wave plate is uniformly arranged according to the law of deflection of mπ angle around a circle; after the laser beam output by the laser passes through the column vector light generating device, a column vector light field is generated, and the polarization state is distributed in an axially symmetrical or rotationally symmetrical manner in the cross section of the beam, and the deflection angle of the polarization direction of the column vector light field around a circle is 2mπ, wherein m represents the topological charge number, and the column vector light generating device can generate column vector light fields with various topological charges.

2. The multi-wave mixing signal generating device according to claim 1, characterized in that: The polarizer (3) is a linear polarizer. After passing through the polarizer (3), the vector light field generates multiple beams of linear polarized light with the same frequency, phase and polarization and distributed in parallel. The beam expander (4) expands the linear polarized light to the first spatial light filter (5), and makes one or more of the linear polarized light beams incident on a specific filtering position corresponding to the first spatial light filter (5). The first spatial light filter (5) has a filtering function at its specific position. After passing through the first spatial light filter (5), the remaining multiple beams of linear polarized light with the same frequency, phase and polarization and distributed in parallel meet the multi-wave mixing conditions of the atomic molecular vapor absorption chamber (7), wherein the atomic molecular vapor absorption chamber (7) generates a multi-wave mixing signal based on a third-order or fifth-order nonlinear effect.

3. The multi-wave mixing signal generating device according to claim 2, characterized in that: The multi-wave mixing signal generating device is a degenerate four-wave mixing signal generating device, wherein the laser is a continuously tunable ring titanium sapphire laser, the vector light generating device (2) is a column vector light generating device with a topological charge equal to two, the laser beam output by the laser generates a column vector light field whose polarization state is axially symmetrically distributed in the beam cross section after passing through the column vector light generating device, the column vector light field generates four beams of linear polarized light with the same frequency, phase and polarization distributed in parallel after passing through the polarizer (3), one of the beams is filtered out through the first spatial light filter (5), and the remaining three beams of linear polarized light with the same frequency, phase and polarization distributed in parallel are focused and incident on an atomic molecular vapor absorption chamber (7), the atomic molecular vapor absorption chamber (7) is an atomic molecular vapor absorption chamber containing rubidium vapor, and the incident three beams of linear polarized light with the same frequency, phase and polarization distributed in parallel generate a degenerate four-wave mixing signal in the atomic molecular vapor absorption chamber (7) based on a third-order nonlinear effect.

4. The multi-wave mixing signal generating device according to claim 2, characterized in that: The multi-wave mixing signal generating device is a degenerate six-wave mixing signal generating device, wherein the laser is a continuously tunable ring titanium sapphire laser, the vector light generating device (2) is a column vector light generating device with a topological charge number equal to three, the laser beam output by the laser generates a column vector light field whose polarization state is axially symmetrically distributed in the beam cross section after passing through the column vector light generating device, the column vector light field generates six beams of linear polarized light with the same frequency, phase and polarization distributed in parallel after passing through the polarizer (3), one of the beams is filtered out through the first spatial light filter (5), and the remaining five beams of linear polarized light with the same frequency, phase and polarization distributed in parallel are focused and incident on an atomic molecular vapor absorption chamber (7), the atomic molecular vapor absorption chamber (7) is an atomic molecular vapor absorption chamber containing rubidium vapor, and the incident five beams of linear polarized light with the same frequency, phase and polarization distributed in parallel generate a degenerate six-wave mixing signal in the atomic molecular vapor absorption chamber (7) based on a fifth-order nonlinear effect.

5. The multi-wave mixing signal generating device according to claim 4, characterized in that: The laser beam output by the laser is a linearly polarized beam, and the laser wavelength is at the resonant absorption wavelength of the atomic and molecular vapor absorption chamber. The vector light generating device (2) is composed of a plurality of half-wave plates, and the fast axis directions of the half-wave plates are arranged in order according to a specific rule. When the laser beam passes through the vector light generating device (2), the polarization direction of the corresponding beam portion passing through each half-wave plate is deflected at a corresponding angle based on the fast axis direction of the half-wave plate. Therefore, after the laser beam passes through the vector light generating device (2), the polarization directions of different beam portions are deflected at different angles corresponding to the fast axis directions of different half-wave plates, and finally a vector light field is generated in which the polarization state is distributed in a specific rule in the beam cross section. The specific rule corresponds to the specific arrangement rule of the fast axis directions of the half-wave plates in the vector light generating device (2).

6. A multi-wave mixing signal spectrum generating device, characterized in that: include: The multi-wave mixing signal generating device according to any one of claims 1 to 5 further comprises a second spatial light filter (8), a photodetector (9) and an oscilloscope (10), wherein the second spatial light filter (8) is arranged on the optical path behind the atomic molecular vapor absorption chamber (7) in the multi-wave mixing signal generating device, and filters out other light beam signals except the multi-wave mixing signal, the photodetector (9) is arranged directly behind the second spatial light filter (8), and is used to detect the multi-wave mixing signal, the oscilloscope (10) is connected to the photodetector (9), and is used to display the multi-wave mixing signal detected by the photodetector (9), and when the wavelength of the laser beam is adjusted, the intensity change of the multi-wave mixing signal can be recorded by the oscilloscope to obtain the spectrum of the multi-wave mixing signal.

7. A method for obtaining a multi-wave mixing signal spectrum based on the multi-wave mixing signal spectrum generating device according to claim 6, characterized in that: The following steps are involved: Step 1: outputting the remaining incident light beam and the multi-wave mixing signal through the multi-wave mixing signal generating device; Step 2: filtering out the remaining incident light beam through a second spatial light filter, so that the multi-wave mixing signal is incident on the photoelectric detector; Step 3: Adjust the wavelength of the laser beam, record the intensity change of the multi-wave mixing signal through an oscilloscope, and obtain the spectrum of the multi-wave mixing signal.

8. A multi-wave mixing signal spot generating device, characterized in that: include: The multi-wave mixing signal generating device according to any one of claims 1 to 5 further comprises an imaging device (11), wherein the imaging device (11) is arranged on a rear optical path of an atomic and molecular vapor absorption chamber (7) in the multi-wave mixing signal generating device, wherein the multi-wave mixing signal and the remaining incident light are incident together on the imaging device, and a light spot pattern including the multi-wave mixing signal is obtained in the imaging device by changing the topological charge number of the vector light field.

9. A method for obtaining a multi-wave mixing signal spot based on the multi-wave mixing signal spot generating device according to claim 8, characterized in that: The following steps are involved: Step 1: outputting the remaining incident light beam and the multi-wave mixing signal through the multi-wave mixing signal generating device; Step 2, the remaining incident light beam and the multi-wave mixing signal are jointly injected into the imaging device; Step 3: Adjust the vector light generating device to change the topological charge of the vector light field, and obtain a light spot diagram including a multi-wave mixing signal in the imaging device.

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