Optical system for atomic interference Raman laser pointing control

Abstract

The invention provides an optical system for atomic interference Raman laser pointing control. The optical system comprises a laser leading-in optical fiber, a first lens group, a reflecting mirror, a second lens group and an ultrahigh vacuum cavity, the laser leading-in optical fiber is used for providing an incident light beam; the first lens group is arranged on one side of the laser leading-in optical fiber along the light path direction of the incident light beam and is used for outputting Gaussian light beams which are approximately parallel light; the reflector is arranged between the first lens group and the second lens group and is used for reflecting the Gaussian beam to the second lens group; the ultrahigh vacuum cavity is arranged on one side, deviating from the reflector, of the second lens group; and emergent light of the second lens group is emitted into the ultrahigh vacuum cavity and coincides with an atomic group in the ultrahigh vacuum cavity. The optical system can accurately measure a target physical quantity; high-performance control on Raman laser pointing is realized; and the positions of light beams and atomic groups are not changed in the laser pointing control process, Gaussian laser beams with required characteristics can be generated, and installation, adjustment and manufacturing are facilitated.

Description

Technical Field

[0001] The invention relates to the field of optical fiber technology, and in particular to an optical system for atomic interference Raman laser pointing control. Background Art

[0002] Quantum precision measurement based on atomic interference is a technology that achieves precise measurement of physical quantities by manipulating the atomic quantum state, obtaining atomic interference signals, and cleverly associating the physical quantity to be measured with the physical properties of the atoms, thus greatly improving the measurement accuracy. This technology is widely used in quantum communication, atomic clocks, cold atom gravimeters, quantum computing and other fields.

[0003] However, its core technology and challenge is that the measurement axis vector is closely related to the Raman laser pointing and needs to be precisely controlled. In particular, in complex outdoor environments, high-precision control of the measurement axis becomes the key. The optical system needs to ensure that the positions of the light beam and the atomic group are stable during laser pointing manipulation. In addition to completing laser pointing manipulation, how to ensure the generation of a specific Gaussian laser beam and that the system is easy to assemble and manufacture are all difficult problems that need to be considered and solved in this field.

[0004] In the prior art, when an atom interferometer is used to measure vector physical quantities, the direction of the measurement vector is associated with the transmission direction of the Raman laser beam. However, when the atom interferometer works on a moving carrier, the shaking of the carrier causes the transmission direction of the Raman laser beam to vibrate, reducing the measurement accuracy and even rendering the atom interferometer unusable. Based on this, the present invention proposes a high-performance optical system for achieving precise control of the Raman laser pointing while meeting the beam stability, characteristic requirements and manufacturing convenience. Summary of the invention

[0005] Based on the above description, the present invention provides an optical system for atomic interference Raman laser pointing control to achieve precise control of Raman laser pointing while meeting the beam stability, characteristic requirements and manufacturing convenience.

[0006] The technical solution of the present invention to solve the above technical problems is as follows: The present invention provides an optical system for atomic interference Raman laser pointing control, comprising: a laser introduction optical fiber, a first lens group, a reflector, a second lens group and an ultra-high vacuum cavity; The laser introduction optical fiber is used to provide an incident light beam; The first lens group is arranged on one side of the laser introduction optical fiber along the optical path direction of the incident light beam, and is used to output a Gaussian beam of approximately parallel light; The reflector is disposed between the first lens group and the second lens group, and is used to reflect the Gaussian beam to the second lens group; The ultra-high vacuum cavity is arranged on a side of the second lens group away from the reflector; the output light of the second lens group is emitted into the ultra-high vacuum cavity and keeps coincidence with the atomic group located in the ultra-high vacuum cavity.

[0007] Based on the above technical solution, the present invention can also be improved as follows.

[0008] Furthermore, the first lens group includes a first meniscus positive lens, a first biconvex positive lens, a first biconcave positive lens and a second meniscus positive lens which are sequentially arranged in an interval along the optical path direction.

[0009] Furthermore, the total length of the first lens group does not exceed 75 mm; The distance between the first meniscus positive lens and the laser introduction optical fiber is not less than 55 mm; The distance between the second meniscus positive lens and the reflector is not less than 20 mm.

[0010] Furthermore, the second lens group includes a second biconvex positive lens, a first meniscus negative lens, a second meniscus negative lens, a third meniscus negative lens, a second biconvex positive lens, a fourth meniscus negative lens and a third meniscus positive lens, which are arranged in sequence along the optical path.

[0011] Furthermore, the total length of the second lens group does not exceed 164 mm; The distance between the second biconvex positive lens and the reflector is not less than 30 mm; The distance between the third meniscus positive lens and the atomic cluster in the ultra-high vacuum cavity is no less than 36 mm.

[0012] Furthermore, the ultra-high vacuum cavity comprises a cavity shell, a cavity optical window and an atomic group; The cavity optical window is arranged on a side of the cavity housing facing the second lens group; The atomic group is arranged in the inner cavity formed by the cavity shell.

[0013] Furthermore, the optical system also includes a deflection actuator; The deflection actuator is connected to the reflector and is used to drive the reflector to deflect so as to change the transmission direction of the incident light.

[0014] Furthermore, the aperture of the optical system is located on the reflector, and the exit pupil position is located at the atomic cluster; when the reflector is deflected at different angles, the center deviation of the laser beam of the optical system is less than 1 μm.

[0015] Furthermore, the laser introduction optical fiber is a polarization-maintaining optical fiber.

[0016] Furthermore, the refractive index of the lens materials in the first lens group and the second lens group at the working wavelength ranges from 1.50 to 1.82.

[0017] Compared with the prior art, the technical solution of this application has the following beneficial technical effects: The optical system for atomic interference Raman laser pointing control provided by the present invention realizes the interference of matter waves of two superpositions of different quantum states by manipulating atoms to transition between ground state energy levels through Raman laser. By measuring the interference phase offset, the target physical quantity can be accurately measured; high-performance control of Raman laser pointing can be achieved. In addition to completing laser pointing control, the optical system can also keep the positions of the light beam and the atomic group unchanged during the laser pointing control process, can generate a Gaussian laser beam with the required characteristics, and is easy to assemble and manufacture.

[0018] Compared with the prior art, the advantages of the optical system for atomic interference Raman laser pointing control are: (1) By utilizing existing optical design methods, a transmissive optical structure consisting of a first lens group and a second lens group is adopted to achieve an optical system design with a laser beam diameter of no less than 10 mm, a beam pointing control range of no less than + / -10 degrees, a wavefront aberration RMS better than 1 / 35λ, and the beam position remaining coincident with the position of the atomic cluster, meeting the requirements of the current advanced atomic interferometry precision measurement device.

[0019] (2) Compared with the current method of using actuators such as rotating motors to achieve the deflection of the entire optical system and then achieve the control of the Raman laser pointing, the present invention only needs to control the rotation of the reflector through the actuator, which can greatly reduce the actuator load, improve the bandwidth of Raman laser pointing control, and reduce the volume and weight of atomic interferometry precision measurement equipment.

[0020] (3) Compared with directly controlling the deflection angle of the divergent laser beam, the present invention adopts the design of "laser collimator + folding and reflecting optical system + telescopic optical system" to reduce the difficulty of overall assembly and manufacturing.

[0021] (4) The present invention uses commonly used optical materials and devices and has a lower production cost.

[0022] (5) The present invention has a large object-space working distance and exit pupil distance, providing sufficient space margin for the subsequent design of atomic interferometry precision measurement equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 A schematic diagram of the structure of an optical system for atomic interference Raman laser pointing control provided by an embodiment of the present invention; Figure 2 A wave aberration curve diagram of an optical system for atomic interference Raman laser pointing control provided by an embodiment of the present invention; Figure 3 An MTF curve diagram of an optical system for atomic interference Raman laser pointing control provided by an embodiment of the present invention; Figure 4 Wavefront diagrams of different fields of view of an optical system for atomic interference Raman laser pointing control provided by an embodiment of the present invention; In the accompanying drawings, the components represented by the reference numerals are listed as follows: 1. Laser introduction optical fiber; 2. The first lens group; 3. Reflector; 4. The second lens group; 5. Ultra-high vacuum cavity; 501. Cavity shell; 502. Cavity optical window; 503. Atomic cluster. DETAILED DESCRIPTION

[0025] In the description of the present invention, it should be noted that, unless otherwise clearly stipulated and limited, the terms "provided with", "set", etc. should be understood in a broad sense. For ordinary technicians in this field, they can understand the specific meanings of the above terms in the present invention according to the specific circumstances, and they do not constitute specific limitations.

[0026] In the description of the embodiments of the present invention, the terms "first" and "second" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance. Unless otherwise specified, "plurality" means two or more.

[0027] In the description of the embodiments of the present invention, the terms "upper", "lower", "inside", "outside", etc. indicate orientations or positional relationships that are customarily placed when the disclosed product is used, or are orientations or positional relationships that are customarily understood by those skilled in the art. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0028] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] The following is combined with Figures 1 to 4 The embodiments of the present invention are further described in detail with examples. The following examples are used to illustrate the present invention but cannot be used to limit the scope of the present invention.

[0030] The optical system for atomic interference Raman laser pointing control provided by the embodiment of the present invention is as follows: Figure 1 As shown, it includes: a laser introduction optical fiber 1, a first lens group 2, a reflector 3, a second lens group 4 and an ultra-high vacuum cavity 5.

[0031] The laser introduction optical fiber 1 is used to provide an incident light beam.

[0032] Specifically, the laser introduction optical fiber 1 emits a Gaussian laser beam with a certain emission angle from the end face of the optical fiber.

[0033] Preferably, the laser introduction optical fiber 1 is a polarization-maintaining optical fiber, for example, a polarization-maintaining optical fiber such as PM850 is selected.

[0034] The first lens group 2 is arranged on one side of the laser introduction optical fiber 1 along the optical path direction of the incident light beam, and is used to output a Gaussian beam of approximately parallel light. This will reduce the position accuracy requirements of the first lens group 2, the reflector 3, and the second lens group 4.

[0035] Specifically, the first lens group 2 includes a first meniscus positive lens L1, a first biconvex positive lens L2, a first biconcave positive lens L3 and a second meniscus positive lens L4 which are sequentially arranged in an interval along the optical path direction.

[0036] The reflector 3 is disposed between the first lens group 2 and the second lens group 4 , and is used for reflecting the Gaussian beam to the second lens group 4 .

[0037] Specifically, the second lens group 4 includes a second biconvex positive lens L5, a first meniscus negative lens L6, a second meniscus negative lens L7, a third meniscus negative lens L8, a second biconvex positive lens L9, a fourth meniscus negative lens L10 and a third meniscus positive lens L11, which are arranged in sequence along the optical path.

[0038] The refractive index of the lens materials in the first lens group 2 and the second lens group 4 at the working wavelength ranges from 1.50 to 1.82.

[0039] Furthermore, in an optional embodiment, the optical system further includes a deflection actuator; the deflection actuator is connected to the reflector 3 and is used to drive the reflector 3 to deflect so as to change the transmission direction of the incident light.

[0040] Specifically, the transmission direction of the incident light can be changed by deflecting the angle of the reflector 3 , and the deflection actuator can be a piezoelectric ceramic actuator, a voice coil motor actuator, etc.

[0041] In a specific example, if Figure 1 As shown, the first lens group 2 and the second lens group 4 include 11 lenses, which are represented by L1 to L11 in order from front to back. The first lens group 2 is composed of L1 to L4, and the second lens group 4I is composed of L5 to L11, among which L1, L2, L3, L4, L5, L9, L11 are positive lenses; L6, L7, L8, L10 are negative lenses.

[0042] Specifically, in this embodiment, according to the requirements of the atomic interferometer Raman laser, the optical indicators of the optical system provided in this example are as follows: Working wavelength: 780.2nm+ / -2pm Image side half field angle: 10°; Object space working distance: 56mm; Image-side working distance: infinite; Exit pupil distance: 36mm; Total length of lens group: 320mm; Exit pupil diameter: 10mm.

[0043] The specific lens parameters are shown in Table 1 below: Table 1 Parameters of optical system components

[0044] Among them, the object plane refers to the object plane of the optical system, that is, the location of the incident optical fiber; the image plane is located at infinity, and the laser emitted from the surface is collimated laser. INF means infinity, indicating that the radius of the spherical surface is infinite, that is, a plane.

[0045] Figure 2 The figure shows the wavefront aberration curve of the optical system. The wavefront aberration RMS is better than 1 / 35λ, and the wavefront aberration PV is better than 1 / 8λ.

[0046] Figure 3 The figure shows the MTF curve of the optical system. The full name of the modulation transfer function MTF is Modulation Transfer Function. MTF comprehensively reflects the contrast and resolution characteristics of the lens. It is measured by instruments and can completely eliminate the influence of objective factors such as film and the influence of subjective factors of manual interpretation.

[0047] MTF is one of the best tools for quantifying the overall imaging performance of a system in terms of resolution and contrast. The higher the MTF value, the higher the resolution of the system, capable of delivering smaller details. MTF is a way of combining resolution and contrast into a single specification or rule. The MTF curve shows both resolution and contrast information, which makes it possible to evaluate a lens based on the needs of a specific application and can be used to compare the performance of multiple lenses.

[0048] In this MTF performance graph, the higher the MTF curve, the higher the lens MTF score and the better the performance. The solid line represents the MTF curve generated parallel to the diameter direction, called the sagittal curve; the dotted line represents the MTF curve generated perpendicular to the diameter direction, called the meridian curve. The closer the solid line and the dotted line are, the closer the MTF performance of the lens in the meridian and sagittal directions is, and the better the lens performance is.

[0049] Figure 4 Shown are wavefront profiles for different fields of view of the optical system.

[0050] By observing the wavefront shape diagram, one can intuitively understand the deformation area and degree of the wavefront; the smaller the deformation area and the slighter the deformation, the better the imaging quality of the optical system.

[0051] The wavefront shape diagram also reflects the size of the wave aberration, which is the optical path difference between the actual wavefront and the ideal spherical wave. The smaller the wave aberration, the closer the actual wavefront is to the ideal wavefront, and the better the imaging quality.

[0052] By comparing the wavefront graphs of different fields of view, we can understand the difference in imaging quality of the optical system under different fields of view; the wavefront graphs of each field of view are relatively close to the ideal wavefront, indicating that the optical system has good imaging quality in the entire field of view.

[0053] The working wavelength laser of the optical system composed of the first lens group 2 and the second lens group 4 comes from a narrow line width laser, and the influence of chromatic aberration can be ignored.

[0054] Among them, the total length of the first lens group 2 does not exceed 75 mm; the distance between the first meniscus positive lens L1 and the laser introduction optical fiber 1 is not less than 55 mm; the distance between the second meniscus positive lens L4 and the reflector 3 is not less than 20 mm.

[0055] The total length of the second lens group 4 does not exceed 164 mm; the distance between the second biconvex positive lens L5 and the reflector 3 is not less than 30 mm; the distance between the third meniscus positive lens L11 and the atomic group 503 in the ultra-high vacuum cavity 5 is not less than 36 mm.

[0056] The ultra-high vacuum cavity 5 is arranged on the side of the second lens group 4 away from the reflector 3; the outgoing light of the second lens group 4 is emitted into the ultra-high vacuum cavity 5, and keeps coincidence with the atomic group 503 located in the ultra-high vacuum cavity 5. That is, under different deflection angles, that is, under different fields of view of the optical system of the second lens group 4, the main light is strictly located on the optical axis at the aperture and the exit pupil.

[0057] Specifically, the ultra-high vacuum cavity 5 includes a cavity shell 501 , a cavity optical window 502 and an atomic group 503 .

[0058] The cavity optical window 502 is disposed on a side of the cavity housing 501 facing the second lens group 4 .

[0059] The atomic group 503 is disposed in the inner cavity formed by the cavity shell 501 .

[0060] Specifically, the incident light beam input by the laser introduction optical fiber 1 is output as a Gaussian beam of approximately parallel light after passing through the first lens group 2, and then after being reflected by the deflectable reflector 3, enters the second lens group 4, and finally irradiates the ultra-high vacuum cavity 5.

[0061] The aperture of the optical system is located on the reflector 3, and the exit pupil position is located at the atomic cluster 503; when the reflector 3 is deflected at different angles, the center deviation of the laser beam of the optical system is less than 1 μm.

[0062] The optical system has an exit pupil diameter greater than or equal to 10 mm, and an image-side field of view angle greater than or equal to + / -10 degrees, which can meet the beam diameter and pointing control angle range of the Raman laser.

[0063] The optical system's full-field wavefront aberration RMS is better than 1 / 35λ.

[0064] The total distance from the laser introduction optical fiber 1 to the atomic cluster 503 does not exceed 320 mm.

[0065] It should be noted that, in this embodiment, the entire optical system can be divided into three components: the first lens group 2 (laser collimator), the reflector 3 (folding and reflecting optical system) and the second lens group 4 (telephoto optical system) for assembly and adjustment, thereby reducing the difficulty of overall assembly and manufacturing.

[0066] The optical system provided by the embodiment of the present invention is an optical system with laser pointing control capability, which can be applied to atomic interference precision measurement equipment. The first lens group 2 and the second lens group 4 are 20 mm away from the deflection mirror 3, and the exit pupil distance is not less than 36 mm, which reserves sufficient design space for the mirror 3 and the ultra-high vacuum cavity 5; the exit pupil diameter is not less than 10 mm, which can provide a beam size and collimation that meet the requirements of atomic interference; the beam pointing angle control of not less than - / +10 degrees is achieved by angular deflection of the deflection mirror 3, and the lasers at various angles overlap at the position of the atomic group 503; the wave aberration of the full field of view is better than 1 / 35λ, which meets the accuracy requirements of atomic interference precision measurement.

[0067] In summary, the advantages of the embodiments of the present invention compared with the prior art are: (1) By utilizing existing optical design methods, a transmission optical structure consisting of no less than 11 objective lenses is adopted to achieve an optical system design with a laser beam diameter of no less than 10 mm, a beam pointing control range of no less than + / -10 degrees, a wavefront aberration RMS better than 1 / 35λ, and the beam position kept coincident with the position of the atomic cluster, meeting the requirements of the current advanced atomic interferometry precision measurement device.

[0068] (2) Compared with the current method of using actuators such as rotating motors to achieve the deflection of the entire optical system and then achieve the control of the Raman laser pointing, the present invention only needs to control the rotation of the reflector through the actuator, which can greatly reduce the actuator load, improve the bandwidth of Raman laser pointing control, and reduce the volume and weight of atomic interferometry precision measurement equipment.

[0069] (3) Compared with directly controlling the deflection angle of the divergent laser beam, the present invention adopts the design of "laser collimator + folding and reflecting optical system + telescopic optical system" to reduce the difficulty of overall assembly and manufacturing.

[0070] (4) The embodiments of the present invention use commonly used optical materials and devices, and have a lower production cost.

[0071] (5) The embodiments of the present invention have a large object-space working distance and exit pupil distance, which provides sufficient space margin for the subsequent design of atomic interferometry precision measurement equipment.

[0072] In the description of this specification, the description with reference to the terms "specific example" or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiment of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example.

[0073] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An optical system for atomic interference Raman laser pointing control, characterized in that: include: Laser introduction optical fiber, first lens group, reflecting mirror, second lens group and ultra-high vacuum cavity; The laser introduction optical fiber is used to provide an incident light beam; The first lens group is arranged on one side of the laser introduction optical fiber along the optical path direction of the incident light beam, and is used to output a Gaussian beam of approximately parallel light; The reflector is disposed between the first lens group and the second lens group, and is used to reflect the Gaussian beam to the second lens group; The ultra-high vacuum cavity is arranged on a side of the second lens group away from the reflector; the output light of the second lens group is emitted into the ultra-high vacuum cavity and keeps coincidence with the atomic group located in the ultra-high vacuum cavity.

2. The optical system for atomic interference Raman laser pointing control according to claim 1, characterized in that: The first lens group includes a first meniscus positive lens, a first biconvex positive lens, a first biconcave positive lens and a second meniscus positive lens which are sequentially arranged in an interval along the optical path.

3. The optical system for atomic interference Raman laser pointing control according to claim 2, characterized in that: The total length of the first lens group does not exceed 75 mm; The distance between the first meniscus positive lens and the laser introduction optical fiber is not less than 55 mm; The distance between the second meniscus positive lens and the reflector is not less than 20 mm.

4. The optical system for atomic interference Raman laser pointing control according to claim 1, characterized in that: The second lens group includes a second biconvex positive lens, a first meniscus negative lens, a second meniscus negative lens, a third meniscus negative lens, a second biconvex positive lens, a fourth meniscus negative lens and a third meniscus positive lens which are sequentially arranged in an interval along the optical path.

5. The optical system for atomic interference Raman laser pointing control according to claim 4, characterized in that: The total length of the second lens group does not exceed 164 mm; The distance between the second biconvex positive lens and the reflector is not less than 30 mm; The distance between the third meniscus positive lens and the atomic cluster in the ultra-high vacuum cavity is no less than 36 mm.

6. The optical system for atomic interference Raman laser pointing control according to claim 1, characterized in that: The ultra-high vacuum cavity comprises a cavity shell, a cavity optical window and an atomic group; The cavity optical window is arranged on a side of the cavity housing facing the second lens group; The atomic group is arranged in the inner cavity formed by the cavity shell.

7. The optical system for atomic interference Raman laser pointing control according to claim 6, characterized in that: The optical system also includes a deflection actuator; The deflection actuator is connected to the reflector and is used to drive the reflector to deflect so as to change the transmission direction of the incident light.

8. The optical system for atomic interference Raman laser pointing control according to claim 7, characterized in that: The aperture of the optical system is located on the reflector, and the exit pupil position is located at the atomic cluster; when the reflector is deflected at different angles, the center deviation of the laser beam of the optical system is less than 1 μm.

9. The optical system for atomic interference Raman laser pointing control according to claim 1, characterized in that: The laser introduction optical fiber is a polarization-maintaining optical fiber.

10. The optical system for atomic interference Raman laser pointing control according to claim 1, characterized in that: The refractive index of the lens materials in the first lens group and the second lens group at the working wavelength ranges from 1.50 to 1.82.

Images