An on-chip integrated three-dimensional magneto-optical trap device

Abstract

The application discloses an on-chip integrated three-dimensional magneto-optical trap device, relates to the field of magneto-optical trap device integration, and comprises a light beam forming structure, two levels of metasurface chips, a gas chamber and a coil component. The light beam forming structure comprises a laser, a beam splitter and a grating coupler. The beam splitter is used for performing a beam splitting operation on emergent light of the laser, and multiple output lights formed by the beam splitter are incident to the grating coupler. The emergent light of the grating coupler is introduced to the two levels of metasurface chips respectively. The two levels of metasurface chips perform polarization state regulation on the emergent light of the grating coupler. Finally, the obtained emergent light converges or intersects at a central position of the gas chamber, and is used for cooling and confining atoms, molecules or ions. The metasurface chip is used to replace a traditional lens structure, the volume of the magneto-optical trap device is reduced, and the integration degree of the magneto-optical trap device is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of magneto-optical trap device integration, and particularly to a three-dimensional magneto-optical trap device integrated on a chip. BACKGROUND

[0002] Magneto-Optical Trap (MOT) technology has become a backbone in the field of laser cooling due to its excellent cooling and atomic trapping capabilities. MOT technology enables atoms to be cooled to extremely low temperatures close to absolute zero, providing the possibility to explore the properties of matter in a state of extremely low kinetic energy. To date, MOT has made remarkable achievements in the field of laser cooling and atomic trapping, and is widely used in cutting-edge technology fields such as high-precision atomic clocks, quantum computers, quantum networks, and quantum memories. Traditional three-dimensional magneto-optical trap systems use six orthogonal laser beams and magnetic fields generated by anti-Helmholtz coils to capture and cool neutral atoms. However, the optical path in the traditional MOT system relies on complex laser devices, optical elements, and precise alignment processes, which has problems such as large volume, complex operation, high maintenance cost, etc., limiting its application in miniaturized, integrated, and low-cost devices.

[0003] In recent years, on-chip integrated magneto-optical traps have become a new research hotspot, mainly to reduce the size of the optical system. The common way is to replace part of the optical structure by forming a pyramid-shaped emitter through three groups of gratings. Although the current MOT structure has a relatively high degree of integration, the volume is still relatively large because the traditional mirrors are still needed to adjust the optical path, therefore, there is an urgent need for a three-dimensional magneto-optical trap device integrated on a chip with a smaller volume. SUMMARY

[0004] The purpose of the present application is to provide a three-dimensional magneto-optical trap device integrated on a chip, which can realize miniaturization, integration and low cost of the three-dimensional magneto-optical trap device.

[0005] To achieve the above purpose, the present application provides the following solutions:

[0006] In a first aspect, the present application provides a three-dimensional magneto-optical trap device integrated on a chip, comprising: a beam forming structure, a first level metasurface structure, a second level metasurface structure, a first gas chamber and a first coil component.

[0007] The beam forming structure is used to form three third exit lights; the first level metasurface structure comprises three first level metasurface chips with beam expanding and polarization state control functions; the second level metasurface structure comprises three second level metasurface chips with polarization state control functions; each third exit light is guided to a first level metasurface chip.

[0008] The first hierarchical metasurface chip is configured to expand and control the polarization state of the third emergent light, form three fourth emergent lights, and make each fourth emergent light incident on a second hierarchical metasurface chip; the second hierarchical metasurface chip is configured to control the polarization state of the fourth emergent light, form three fifth emergent lights, and make each fifth emergent light incident on the corresponding first hierarchical metasurface chip in the original path; the three fourth emergent lights and the three fifth emergent lights intersect at the center of the first gas chamber.

[0009] The first gas chamber is configured to cool and trap atoms, molecules or ions by the magnetic field generated by the first coil component, the fourth emergent light and the fifth emergent light.

[0010] Optionally, the light beam forming structure comprises a light beam generating component, a first beam splitter with a one-to-three function, and three grating couplers; the light beam generating component is configured to form a first emergent light and input the first emergent light into the first beam splitter; the first beam splitter is configured to split the first emergent light to form three second emergent lights; the three second emergent lights are respectively transmitted to the three grating couplers, each grating coupler converts the second emergent light into a third emergent light with a preset angle, and each third emergent light is guided to a first hierarchical metasurface chip.

[0011] Or,

[0012] The light beam forming structure comprises three groups of light beam generating components and three grating couplers; the light beam generating component is configured to form three first emergent lights; the three first emergent lights are respectively transmitted to the three grating couplers, each grating coupler converts the first emergent light into a third emergent light with a preset angle, and each third emergent light is guided to a first hierarchical metasurface chip.

[0013] Optionally, the light beam generating component comprises a laser or a plurality of lasers, a frequency locking component, a laser frequency control component, an acousto-optic modulator and a polarization controller.

[0014] The frequency locking component comprises a photodiode and a feedback control circuit, and is configured to lock the optical frequency of the laser to a reference frequency.

[0015] The laser frequency control component is a frequency shifter or a laser frequency controller, and is configured to lock the optical frequency of the pre-stabilized light beam generating component to an optical frequency related to at least one atomic transition.

[0016] The acousto-optic modulator is configured to simultaneously realize laser beam modulation and laser frequency control.

[0017] The polarization controller is configured to ensure that the laser output is a single polarization state light beam.

[0018] Optionally, the fourth emergent light is circularly polarized light.

[0019] Optionally, three first-level metasurface chips are arranged on the lower outer side of the first air chamber, and three second-level metasurface chips are arranged on the upper outer side of the first air chamber; each first-level metasurface chip is centrosymmetric to the second-level metasurface chip on which the fourth emergent light is incident, with respect to the center position of the first air chamber.

[0020] Optionally, the center positions of the three grating couplers intersect at the inside of the first air chamber, and the included angle of the three extended lines is 120 degrees.

[0021] In a second aspect, the application provides another kind of on-chip integrated three-dimensional magneto-optical trap device, comprising: a beam forming structure, a third-level metasurface structure, a fourth-level metasurface structure, a second air chamber and a second coil component;

[0022] The beam forming structure comprises a beam generating component, a second beam splitter with a two-way function, third and fourth beam splitters with a three-way function, a first-level grating coupling structure and a second-level grating coupling structure; the first-level grating coupling structure comprises three first-level grating couplers; the second-level grating coupling structure comprises three second-level grating couplers; the third-level metasurface structure comprises three third-level metasurface chips with the functions of regulating direction and polarization state; the fourth-level metasurface structure comprises three fourth-level metasurface chips with the functions of regulating direction and polarization state;

[0023] The beam generating component is used to form a sixth emergent light and input the sixth emergent light into the second beam splitter; the second beam splitter is used to perform a light splitting operation on the sixth emergent light to form two seventh emergent lights; the two seventh emergent lights are transmitted to the third and fourth beam splitters respectively, and the third and fourth beam splitters perform a light splitting operation on the seventh emergent light to form three eighth emergent lights respectively; the three eighth emergent lights formed by the third beam splitter are incident to the three first-level grating couplers respectively; the three eighth emergent lights formed by the third beam splitter are incident to the three second-level grating couplers respectively;

[0024] The first-level grating coupler is used to convert the eighth emergent light into a light beam in space and amplify the mode spot of the light beam to form three first-level ninth emergent lights; the three first-level ninth emergent lights are incident to the three third-level metasurface chips respectively; the second-level grating coupler is used to convert the eighth emergent light into a light beam in space and amplify the mode spot of the light beam to form three second-level ninth emergent lights; the three second-level ninth emergent lights are incident to the three fourth-level metasurface chips respectively;

[0025] The third-level metasurface chip is used for refracting and regulating the polarization state of the first-level ninth emergent light to form three beams of first-level tenth emergent light; the fourth-level metasurface chip is used for refracting and regulating the polarization state of the second-level ninth emergent light to form three beams of second-level tenth emergent light; the three beams of first-level tenth emergent light and the three beams of second-level tenth emergent light converge at the center position of the second gas chamber.

[0026] The second gas chamber is used for cooling and trapping atoms, molecules or ions by the magnetic field generated by the second coil component, the first-level tenth emergent light and the second-level tenth emergent light.

[0027] Optionally, the first-level tenth emergent light is right-handed circularly polarized light, and the second-level tenth emergent light is left-handed circularly polarized light; the included angle between the first-level tenth emergent light and the second-level tenth emergent light and the horizontal direction is 60 degrees.

[0028] Optionally, three third-level metasurface chips are arranged on the upper outer side of the second gas chamber; three fourth-level metasurface chips are arranged on the lower outer side of the second gas chamber.

[0029] Optionally, the extension lines of the center positions of the three first-level grating couplers intersect at a point; the three second-level grating couplers are arranged in parallel.

[0030] According to the specific embodiments provided in the present application, the following technical effects are disclosed:

[0031] The present application provides a three-dimensional magneto-optical trap device integrated on a chip, a light beam forming structure, two levels of metasurface chips, a gas chamber and a coil component. The light beam forming structure includes a laser, a beam splitter and a grating coupler. The beam splitter is used for beam splitting operation on the emergent light of the laser, and the multiple output lights formed by the beam splitter are incident to the grating coupler. The emergent light of the grating coupler is introduced into the two levels of metasurface chips, respectively. The two levels of metasurface chips regulate the polarization state of the emergent light of the grating coupler, and finally the emergent light converges or intersects at the center position of the gas chamber, which is used for cooling and trapping atoms, molecules or ions. The present application integrates the optical path part on the chip, replaces the traditional lens structure with metasurface chips with different functions, reduces the volume of the magneto-optical trap device, and improves the integration of the magneto-optical trap device. BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed in the embodiments. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0033] Figure 1 A structural schematic diagram of an on-chip integrated three-dimensional magneto-optical trap device provided by an embodiment of the present application is shown in FIG. 1.

[0034] Figure 2 A light path schematic diagram of a pair of beam expanding metasurface chips and a gyrator metasurface chip provided by an embodiment of the present application is shown in FIG. 2.

[0035] Figure 3 A structural schematic diagram of a light beam generating component provided by an embodiment of the present application is shown in FIG. 3.

[0036] Figure 4 A structural schematic diagram of another on-chip integrated three-dimensional magneto-optical trap device provided by an embodiment of the present application is shown in FIG. 4.

[0037] Reference signs:

[0038] First exit light - 1, first beam splitter - 2, first grating coupler - 3, second grating coupler - 4, third grating coupler - 5, first beam expanding metasurface chip - 6, second beam expanding metasurface chip - 7, third beam expanding metasurface chip - 8, first gyrator metasurface chip - 9, first gas chamber - 10, third gyrator metasurface chip - 11, second gyrator metasurface chip - 12, first coil - 13, second coil - 14, second beam splitter - 15, third beam splitter - 16, fourth beam splitter - 17, first level first grating coupler - 18, first level second grating coupler - 19, first level third grating coupler - 20, second level first grating coupler - 21, second level second grating coupler - 22, second level third grating coupler - 23, first polarization conversion metasurface chip - 24, second polarization conversion metasurface chip - 25, third polarization conversion metasurface chip - 26, fourth gyrator metasurface chip - 27, fifth gyrator metasurface chip - 28, sixth gyrator metasurface chip - 29, second gas chamber - 30, third coil - 31, fourth coil - 32. DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0040] The above purposes, features and advantages of the present application will be more apparent and understandable. The present application will be further described in detail below with reference to the drawings and specific embodiments.

[0041] In one example embodiment of the present application, the embodiment provides an on-chip integrated three-dimensional magneto-optical trap device, which comprises a beam forming structure, a first-level metasurface structure, a second-level metasurface structure, a first gas chamber 10 and a first coil component. The first coil component comprises a first coil 13 and a second coil 14.

[0042] The beam forming structure is used to form three third exit lights; the first-level metasurface structure comprises three first-level metasurface chips with beam expanding and polarization state control functions; the second-level metasurface structure comprises three second-level metasurface chips with polarization state control functions; each third exit light is guided to a first-level metasurface chip;

[0043] The first-level metasurface chip is used to perform beam expanding and polarization state control operations on the third exit light, form three fourth exit lights, and make each fourth exit light incident on a second-level metasurface chip; the second-level metasurface chip is used to perform polarization state control operations on the fourth exit light, form three fifth exit lights, and make each fifth exit light incident on the corresponding first-level metasurface chip in the original path; three fourth exit lights and three fifth exit lights intersect at the center position of the first gas chamber 10;

[0044] The first gas chamber 10 is used to cool and trap atoms, molecules or ions by the magnetic field generated by the first coil component, the fourth exit light and the fifth exit light.

[0045] The beam forming structure can include two implementation schemes:

[0046] The first scheme: the beam forming structure comprises a beam generating component, a first beam splitter 2 with a one-to-three function and three grating couplers; the beam generating component is used to form a first exit light 1 and input the first exit light to the first beam splitter 2; the first beam splitter 2 is used to perform light splitting operations on the first exit light to form three second exit lights; three second exit lights are transmitted to three grating couplers respectively, each grating coupler converts the second exit light into a third exit light with a preset angle, and each third exit light is guided to a first-level metasurface chip. Figure 1 The on-chip integrated three-dimensional magneto-optical trap device under the first scheme.

[0047] The second scheme: the beam forming structure comprises three groups of beam generating components and three grating couplers; the beam generating component is used to form three first exit lights; three first exit lights are transmitted to three grating couplers respectively, each grating coupler converts the first exit light into a third exit light with a preset angle, and each third exit light is guided to a first-level metasurface chip.

[0048] The three grating couplers are named as a first grating coupler 3, a second grating coupler 4 and a third grating coupler 5 respectively. The grating couplers are used to convert the light in the waveguide into spatial light beams and achieve mode spot amplification.

[0049] The beam generation component further comprises one laser or multiple lasers, a frequency locking component, a laser frequency control component, an acousto-optic modulator and a polarization controller; the frequency locking component comprises a photodiode and a feedback control circuit, and is used to lock the optical frequency of the laser to a reference frequency; the laser frequency control component is a frequency shifter or a laser frequency controller, and is used to lock the optical frequency of the pre-stabilized laser to an optical frequency related to at least one atomic transition. The laser is pre-stabilized to at least one frequency effect, and the laser is locked to at least one frequency reference, which is selected from a group comprising an atomic frequency reference and an optical cavity frequency reference. The acousto-optic modulator is used to simultaneously achieve laser beam modulation and laser frequency control, adjust the input laser power according to different requirements, and meet the requirements of cooling and trapping atoms; the polarization controller is used to ensure that the laser output is a single polarization state of light beam, facilitating the subsequent regulation of the polarization state of the light beam by the metasurface chip.

[0050] As shown in Figure 3 , the cooling light and the repumping light are generated by two lasers respectively, or one laser is divided into two paths to generate the cooling light and the repumping light. The above-mentioned beam generation component can be directly connected with the beam splitter in Figure 1 and Figure 4 .

[0051] The optical frequency of the laser matches a transition selected from a group comprising a virtual atomic transition, a multi-photon transition, a direct transition and an indirect transition. The optical frequency of the laser is selected from a list comprising deep ultraviolet, ultraviolet, near ultraviolet, visible light, near infrared, mid-infrared and infrared wavelengths. The frequency of the laser is adjustable, and needs to be pre-adjusted to a fixed frequency when used. This can be consistent with the atomic transition frequency, or consistent with the multi-photon transition frequency, or consistent with the direct atomic transition frequency, or consistent with the indirect atomic transition frequency.

[0052] The beam generation component is coupled with the three grating couplers, and the output coupling grating of the grating coupler is combined with the first-level metasurface chip and the second-level metasurface chip, and is used to communicate with the target. The target is selected from a list comprising at least one atom in the first gas chamber 10, at least one ion in an ion trap and a molecule in the first gas chamber 10, and specifically, the target is selected from a group comprising a vapor chamber, an ion trap, a 1D MOT, a 2D MOT and a 3D MOT.

[0053] Figure 1In some embodiments, the three grating couplers are configured to emit light at a selected angle that causes the set of free-space beams to intersect at a location inside the first gas cell 10. In some embodiments, the three grating couplers are configured to emit light at a selected polarization selected from the group consisting of circular polarization, elliptical polarization, and engineered degree of polarization. In some embodiments, the three grating couplers are configured to emit light at a selected intensity profile selected from the group consisting of flat top, Gaussian, and engineered intensity profile.

[0054] The laser, the photodiode, the laser frequency control component, and the grating coupler are integrated into an integrated circuit that integrates the grating coupler into a monolithically integrated three-dimensional magneto-optical trap device. The monolithically integrated three-dimensional magneto-optical trap device is a CMOS foundry-compatible silicon nitride waveguide optical circuit in which a set of relative positions of the grating coupler is fixed during the manufacturing process, while the relative positions of the grating coupler and the metasurface chip are also fixed. The substrate material used in the photonic integrated optical circuit is selected from silicon nitride, tin oxide, aluminum nitride, aluminum oxide, or tantalum pentoxide.

[0055] The laser is configured to form a first outgoing light and input the first outgoing light to the first beam splitter 2. The first beam splitter 2 is configured to split the first outgoing light to form three second outgoing lights. The three second outgoing lights are transmitted to three grating couplers respectively. Each grating coupler converts the second outgoing light to a third outgoing light having a preset angle and directs each third outgoing light to a first-level metasurface chip. The preset angle can be in a range of 0-90 degrees.

[0056] The first-level metasurface structure includes three first-level metasurface chips having beam expanding and polarization state control functions. The second-level metasurface structure includes three second-level metasurface chips having polarization state control functions. The first-level metasurface chips are beam expanding metasurface chips, and the second-level metasurface chips are gyrator metasurface chips. The first-level metasurface chips in the first-level metasurface structure are named as a first beam expanding metasurface chip 6, a second beam expanding metasurface chip 7, and a third beam expanding metasurface chip 8 respectively. The second-level metasurface chips in the second-level metasurface structure are named as a first gyrator metasurface chip 9, a second gyrator metasurface chip 12, and a third gyrator metasurface chip 11.

[0057] The super surface chips are located around the first gas chamber 10. Three first-level super surface chips are arranged on the outer side below the first gas chamber 10, that is, three beam expanding super surface chips are installed on the bottom of the first gas chamber 10. Three second-level super surface chips are arranged on the outer side above the first gas chamber 10, that is, three galvanometer mirror super surface chips are installed on the top of the first gas chamber 10. Each first-level super surface chip is symmetrically centered with respect to the center position of the first gas chamber 10 with the fourth outgoing light incident on the second-level super surface chip.

[0058] The first-level super surface chip is used for beam expanding and polarization state control of the third outgoing light, forming three fourth outgoing lights, and each fourth outgoing light is incident on a second-level super surface chip. The second-level super surface chip is used for polarization state control of the fourth outgoing light, forming three fifth outgoing lights, and each fifth outgoing light is incident on the corresponding first-level super surface chip. The three fourth outgoing lights and the three fifth outgoing lights intersect at the center position of the first gas chamber 10, so that six lights intersect at a certain position inside the first gas chamber 10, and finally form six lights overlapping inside the first gas chamber 10.

[0059] The fourth outgoing light is circularly polarized light. The first-level super surface chip is used to expand the beam and convert the polarization state of the beam into circularly polarized light (such as converting linearly polarized light into circularly polarized light). At least one first-level super surface chip is configured to emit polarization in the combination of circular polarization and elliptical polarization. At least one first-level super surface chip is configured to expand the spot diameter from micrometer size to millimeter size.

[0060] The second-level super surface chip is used to realize the reflection of the light beam and the control of the circular polarization state. The second-level super surface chip is configured to fold back the incident light and change the state of the circular polarization state. For example, when the input fourth outgoing light is left-handed circularly polarized light, the output fifth outgoing light is right-handed circularly polarized light. When the input fourth outgoing light is right-handed circularly polarized light, the output fifth outgoing light is left-handed circularly polarized light.

[0061] The first gas chamber 10 is used to cool and confine atoms, molecules or ions by the fifth outgoing light. The confined object is the first gas chamber 10 containing atoms or the vacuum first gas chamber 10 containing ions or molecules. The shape of the first gas chamber 10 can be one of a cuboid, a cylinder, a hexagonal prism or an octagonal prism.

[0062] In another exemplary embodiment of this application, a photonic integrated fiber-coupled photonic chip can be used to realize laser cooling and trapping of atoms in a three-dimensional magneto-optical trap. Besides cooling and trapping, other beams can be used, such as atomic interrogation and optical transitions or clock readout. Generally, magneto-optical traps are used for neutral atoms, but cooling and trapping of ions and molecules can also be performed. The photonic chip directly inputs cooling and repumping light, as well as other beams, into the atomic gas cell, which is also possible with ion and molecular gas cells, including mixtures thereof. The on-chip integrated three-dimensional magneto-optical trap device can be a CMOS foundry-compatible silicon nitride waveguide optical path. It can provide fiber coupling, beam spreading, collimation, and atomic gas cell beams and magneto-optical trap and atomic, ion, and molecular systems, as well as other required functions.

[0063] Cold atoms are crucial for precision atomic applications, including time preservation and sensing. Generally, atoms, ions, molecules, and combinations thereof can be used for precision scientific experiments and applications, and three-dimensional magneto-optical traps (MOTs) can be used to generate cold atoms, ions, and molecular clouds. 3D MOTs can be improved through photonic waveguide integration, which can increase reliability and reduce size, weight, and cost. Photonic integration can also improve the performance of MOTs by providing phase and optical stability, as well as precision laser and optical performance. In this embodiment, the 3D MOT may require delivering multiple, large-area, and / or collimated laser beams to an atomic vacuum chamber. The atomic vacuum chamber may also be referred to as a vapor chamber and / or an atomic gas chamber. In several embodiments, the MOT can be designed to cool and trap various atoms, such as rubidium (Rb). MOTs designed to cool and trap various atoms are advantageous for various types of cold atom sensors. In this embodiment, 87 The Rb 3D magneto-optical trap can use fiber-coupled photonic integrated optical paths to transmit all the necessary beams for cooling and trapping more than 1x10 6 The trapping volume is approximately 200 μK, which is the number of atoms. In this embodiment, the trapping volume can be an order of magnitude smaller than that of a diffraction grating MOT with an equivalent number of atoms. The diffraction grating MOT is an example of non-integrated bulk optics. Lower temperatures can be achieved by introducing lasers and beams that cool atoms to sub-Doppler temperatures using photonic integrated optical paths, such as introducing 20 μK into the trapping volume. Lower temperatures can be used in applications such as Bose-Einstein condensates (BECs) and atomic interferometry. Other types of gratings may be desirable and necessary, such as gratings for lattice-trapped beam transport, gratings for Raman-cooled beams, and gratings for optical tweezers. Optical tweezers and equivalent techniques can be used to trap single and / or small groups of atoms, ions, particles, and / or molecules using optical forces.

[0064] In another example embodiment of the application, a silicon nitride photonic integrated optical circuit can convert fiber-coupled 780 nm cooling and repumping light provided by a laser into on-chip waveguides (e.g., waveguides mounted on the photonic integrated optical circuit). Other wavelengths can also be provided depending on the requirements of the particular atomic or molecular species. For example, neutral strontium can require 461 nm, 816 nm, 689 nm, 679 nm, 707 nm, and 728 nm for cooling, magic-lattice, repumping, and optical clock transitions. Trapped strontium ions can require 422 nm, 461 nm, 405 nm, and 674 nm for cooling and optical clock transitions. The on-chip integrated waveguides can convert the provided cooling and repumping light into three orthogonal non-diverging free-space cooling and repumping beams (e.g., 2.5 mm x 3.5 mm free-space cooling and repumping beams) by means of transforming waveguides and / or waveguide gratings. Other beam configurations are possible and can be desirable, and are not limited herein. In one particular embodiment, the three orthogonal non-diverging free-space cooling and repumping beams can interface directly with a rubidium cell to cool and trap atoms. In this embodiment, a fully planar, CMOS foundry-compatible on-chip integrated three-dimensional magneto-optical trap device can mount the waveguides and emitters to provide cooling and / or repumping beams to an atomic cell. In this embodiment, the on-chip integrated three-dimensional magneto-optical trap device can include lasers and modulators for a system-on-a-chip solution for cold atom applications.

[0065] Figure 1The working principle of the on-chip integrated three-dimensional magnetic optical trap device is as follows: the on-chip integrated three-dimensional magnetic optical trap device uses optical fiber to transmit laser to achieve atom cooling and trapping. It includes an optical fiber, a beam splitter, a grating coupler, a beam expanding metasurface chip, a retroreflector metasurface chip and a gas chamber. The first outgoing light is emitted by a laser and transmitted to the first beam splitter 2 through the optical fiber. The first beam splitter 2 divides the first outgoing light into three second outgoing lights. The second outgoing lights are transmitted to the first grating coupler 3, the second grating coupler 4 and the third grating coupler 5 respectively. The first grating coupler 3, the second grating coupler 4 and the third grating coupler 5 emit free space beams (third outgoing light) at a preset angle. The angle between each grating coupler is about 120 degrees. Each grating coupler is placed obliquely above a beam expanding metasurface chip. The first beam expanding metasurface chip 6, the second beam expanding metasurface chip 7 and the third beam expanding metasurface chip 8 expand the third outgoing light from the first grating coupler 3, the second grating coupler 4 and the third grating coupler 5, and control the polarization state of the third outgoing light, so that the fourth outgoing light with a circularly polarized light output polarization state is output. The three fourth outgoing lights output by the beam expanding metasurface are orthogonal to each other and overlap in the middle of the gas chamber (the light beams are represented by obliquely placed cylinders). Three retroreflector metasurface chips are arranged on the outer side of the upper part of the gas chamber. The first retroreflector metasurface chip 9, the second retroreflector metasurface chip 12 and the third retroreflector metasurface chip 11 fold back the light transmitted by the first beam expanding metasurface chip 6, the second beam expanding metasurface chip 7 and the third beam expanding metasurface chip 8, and change the polarization state of the light, so that three fifth outgoing lights are obtained. Finally, the three lights folded back by the retroreflector metasurface chip and the three lights initially output by the beam expanding metasurface chip overlap in the center of the gas chamber, so that atom, molecule or ion cooling and trapping is achieved.

[0066] Figure 2 In the middle, the light beams are emitted by the grating coupler, expanded by the beam expanding metasurface chip, and the polarization state of the light beams is converted into a circularly polarized light output (the angle in the figure is only an example and is not a limitation of the present application). The circularly polarized light (which can be left-handed circularly polarized light or right-handed circularly polarized light) output by the beam expanding metasurface chip hits the inside of the gas chamber, and then is transmitted to the retroreflector metasurface chip. The retroreflector metasurface chip folds back the incident light and controls the polarization state. In this way, a set of (two) light beams for cooling atoms, molecules or ions is formed. Through three sets of metasurface chips, six light beams can be used to cool and trap atoms, molecules or ions.

[0067] In another exemplary embodiment of the present application, as shown in Figure 4 The present application also provides another on-chip integrated three-dimensional magnetic optical trap device, which comprises a light beam forming structure, a third level metasurface structure, a fourth level metasurface structure, a second gas chamber 30 and a second coil member. The second coil member comprises a third coil 31 and a fourth coil 32.

[0068] The light beam forming structure comprises a light beam generating component, a second beam splitter 15 with a two-way splitting function, a third beam splitter 16 and a fourth beam splitter 17 with a three-way splitting function, a first-level grating coupling structure, and a second-level grating coupling structure; the first-level grating coupling structure comprises three first-level grating couplers; the second-level grating coupling structure comprises three second-level grating couplers; the third-level metasurface structure comprises three third-level metasurface chips with the functions of regulating direction and polarization state; and the fourth-level metasurface structure comprises three fourth-level metasurface chips with the functions of regulating direction and polarization state.

[0069] The three first-level grating couplers are respectively named as a first-level first grating coupler 18, a first-level second grating coupler 19, and a first-level third grating coupler 20. The three second-level grating couplers are respectively named as a second-level first grating coupler 21, a second-level second grating coupler 22, and a second-level third grating coupler 23.

[0070] The third-level metasurface chips are gyroscope metasurface chips, and the three third-level metasurface chips are named as a fourth gyroscope metasurface chip 27, a fifth gyroscope metasurface chip 28, and a sixth gyroscope metasurface chip 29; and the three fourth-level metasurface chips are named as a first polarization conversion type metasurface chip 24, a second polarization conversion type metasurface chip 25, and a third polarization conversion type metasurface chip 26.

[0071] The light beam generating component is used to form sixth emergent light and input the sixth emergent light into the second beam splitter 15; the second beam splitter 15 is used to split the sixth emergent light to form two beams of seventh emergent light; the two beams of seventh emergent light are respectively transmitted to the third beam splitter 16 and the fourth beam splitter 17, and the third beam splitter 16 and the fourth beam splitter 17 split the seventh emergent light to respectively form three beams of eighth emergent light; the three beams of eighth emergent light formed by the third beam splitter 16 are respectively incident on the three first-level grating couplers; and the three beams of eighth emergent light formed by the third beam splitter 16 are respectively incident on the three second-level grating couplers.

[0072] The first-level grating couplers are used to convert the eighth emergent light into light beams in space and amplify the mode spots of the light beams to form three beams of first-level ninth emergent light; the three beams of first-level ninth emergent light are respectively incident on the three third-level metasurface chips; and the second-level grating couplers are used to convert the eighth emergent light into light beams in space and amplify the mode spots of the light beams to form three beams of second-level ninth emergent light; the three beams of second-level ninth emergent light are respectively incident on the three fourth-level metasurface chips.

[0073] The third-level metasurface chip is used for refracting and regulating the polarization state of the first-level ninth emergent light to form three beams of first-level tenth emergent light; the fourth-level metasurface chip is used for refracting and regulating the polarization state of the second-level ninth emergent light to form three beams of second-level tenth emergent light; the three beams of first-level tenth emergent light and the three beams of second-level tenth emergent light converge at the center position of the second gas chamber 30.

[0074] The second gas chamber 30 is used for cooling and trapping atoms, molecules or ions by the first-level tenth emergent light and the second-level tenth emergent light.

[0075] As an optional implementation, the first-level tenth emergent light is right-handed circularly polarized light, and the second-level tenth emergent light is left-handed circularly polarized light; the included angle between the first-level tenth emergent light and the second-level tenth emergent light and the horizontal direction is 60 degrees.

[0076] Three third-level metasurface chips are arranged on the upper outer side of the second gas chamber 30; three fourth-level metasurface chips are arranged on the lower outer side of the second gas chamber 30.

[0077] The extension lines of the center positions of the three first-level grating couplers intersect at a point; the three second-level grating couplers are arranged in parallel.

[0078] Figure 4In the embodiment, the working principle of the three-dimensional magneto-optical trap device integrated on a chip is as follows: the laser output light (the sixth emergent light) is first divided into two beams of second emergent light via a 1:2 beam splitter, transmitted through a waveguide to a 1:3 beam splitter, divided into six beams of eighth emergent light via the 1:3 beam splitter, and input into six grating couplers respectively. The beams in the waveguide are converted into beams in space through the first grating coupler 18, the second grating coupler 19, the third grating coupler 20, the first grating coupler 21, the second grating coupler 22 and the third grating coupler 23 of the second level, and the mode spot of the beams is amplified at the same time, so that three beams of first-level ninth emergent light and three beams of second-level ninth emergent light are obtained. The first grating coupler 18, the second grating coupler 19 and the third grating coupler 20 of the first level are connected with the fourth rotary mirror metasurface chip 27, the fifth rotary mirror metasurface chip 28 and the sixth rotary mirror metasurface chip 29 respectively, the fourth rotary mirror metasurface chip 27, the fifth rotary mirror metasurface chip 28 and the sixth rotary mirror metasurface chip 29 refract the input first-level ninth emergent light, and the angle with the horizontal direction is about 60 degrees, and at the same time, the input light is converted into right circularly polarized light, that is, the first-level tenth emergent light is right circularly polarized light, and then connected with the second gas chamber 30. The first grating coupler 21, the second grating coupler 22 and the third grating coupler 23 of the second level are connected with the first polarization conversion metasurface chip 24, the second polarization conversion metasurface chip 25 and the third polarization conversion metasurface chip 26 respectively, the first polarization conversion metasurface chip 24, the second polarization conversion metasurface chip 25 and the third polarization conversion metasurface chip 26 convert the second-level ninth emergent light incident by the first grating coupler 21, the second grating coupler 22 and the third grating coupler 23 of the second level into left circularly polarized light output, and the angle of the output second-level tenth emergent light with the horizontal direction is about 60 degrees. Finally, the six beams (three beams of first-level tenth emergent light and three beams of second-level tenth emergent light) are simultaneously input into the center position of the second gas chamber to realize the cooling and trapping of atoms, molecules or ions.

[0079] Polarization conversion type metasurface chip: an array of nanostructure units composed of one or more high refractive index materials, each nanostructure unit having independently designed collective parameters including height, width, and shape. By geometric rotation or shape design of the nanostructure unit, the polarization state conversion of the incident light is realized, mainly linear polarization conversion to circular polarization. Among them, the period of the nanostructure unit is less than the wavelength of the incident light to suppress high-order diffraction. The material of the nanostructure unit is a high refractive index and low absorption material, including but not limited to titanium dioxide, silicon or gallium nitride. The polarization state conversion is based on the Pancharatnam-Berry (PB) phase principle, and the PB phase is controlled by the rotation angle of the unit, which is 2θ. Among them, the thickness of the nanostructure unit is between 300 nm and 600 nm to achieve high diffraction efficiency. The nanostructure unit has a polarization state conversion function in the wavelength range of 400 nm to 1200 nm.

[0080] Beam expanding metasurface chip: based on the polarization conversion type metasurface chip, the function of beam expanding is added to obtain the beam expanding metasurface chip (the design of the polarization conversion part of the beam expanding metasurface chip is consistent with the previous one). The function of beam expanding is mainly achieved by introducing the regulation of the incident light wavefront when designing the nanostructure, and the beam expanding is controlled by the phase distribution Φ(x, y) to meet the following formula: λ is the wavelength of light, f is the effective focal length, and r is the radial distance of the light beam, which is achieved by adjusting the period and arrangement of the nanostructure unit. The beam expanding function is based on the generation of quasi-parabolic wavefront distribution, which is used to expand the light beam diameter from 100 um to 10 mm or more. The nanostructure unit includes elliptical, rectangular or L-shaped structure. Among them, the beam expanding metasurface chip is suitable for the wavelength range of 400 nm to 1200 nm, and has high beam expanding efficiency and polarization state conversion efficiency in this range.

[0081] Horn metasurface chip: the function of back reflection can be realized by double-layer metasurface design or single-layer special phase distribution, so that each nanostructure unit provides precise phase compensation for the light beam, and the direction of the reflected light is completely consistent with that of the incident light. Single-layer scheme: through the combination regulation of PB phase rotation, local polarization adjustment and wavefront reflection are simultaneously controlled. Double-layer scheme: the first layer realizes wavefront shaping, and the second layer realizes light beam back reflection. The two layers work together to ensure that the direction and path of the light beam are completely consistent. The material selection adopts high refractive index and low loss materials (such as titanium dioxide, gallium nitride or silicon) to improve the reflection efficiency. Specifically, it is an array of nanostructure units composed of high refractive index materials, each nanostructure unit having independently designed geometric parameters, and the phase distribution of the nanostructure array meets the back reflection condition, so that the incident light returns along the original path after passing through the horn metasurface chip, and high-efficiency back reflection of different wavelengths of light can be realized at the same time, and the reflection efficiency is greater than 90%.

[0082] The on-chip integrated three-dimensional magneto-optical trap device provided in the application only needs one light input to realize atom trapping and cooling. The combination of a beam splitter, a grating coupler, a beam expanding metasurface chip and a retro-reflector metasurface chip realizes the integration of the on-chip three-dimensional magneto-optical trap device. Compared with the existing scheme, the application uses a metasurface chip to replace the traditional wave plate, and the combination of the beam expanding metasurface chip and the retro-reflector metasurface chip completely replaces the traditional wave plate, further reduces the volume of the magneto-optical trap device, and improves the integration of the magneto-optical trap device.

[0083] The technical features of the above embodiments can be combined in any manner. To make the description concise, all possible combinations of the technical features in the above embodiments are not described, but as long as the combinations of the technical features do not exist contradictions, they should be considered as the scope of the present application.

[0084] The principles and implementation modes of the application are described by using specific examples in this paper, and the above embodiments are only used to help understand the method and its core idea of the application. Meanwhile, for those skilled in the art, the specific implementation modes and application ranges will be changed according to the idea of the application. In conclusion, the content of the specification should not be understood as a limitation of the application.

Claims

1. An on-chip integrated three-dimensional magneto-optical trap device, characterized by, The on-chip integrated three-dimensional magneto-optical trap device comprises a beam forming structure, a first-level metasurface structure, a second-level metasurface structure, a first gas chamber and a first coil component; The beam forming structure is used for forming three third emergent lights; the first-level metasurface structure comprises three first-level metasurface chips with the functions of beam expansion and polarization state regulation; the second-level metasurface structure comprises three second-level metasurface chips with the function of polarization state regulation; each third emergent light is guided to a first-level metasurface chip; The first-level metasurface chip is used for performing the operations of beam expansion and polarization state regulation on the third emergent light, forming three fourth emergent lights, and making each fourth emergent light incident on a second-level metasurface chip; the second-level metasurface chip is used for performing the operation of polarization state regulation on the fourth emergent light, forming three fifth emergent lights, and making each fifth emergent light incident on the corresponding first-level metasurface chip in the original path; the three fourth emergent lights and the three fifth emergent lights intersect at the central position of the first gas chamber; The first gas chamber is used for cooling and trapping atoms, molecules or ions by the magnetic field generated by the first coil component, the fourth emergent light and the fifth emergent light; The first-level metasurface chips in the first-level metasurface structure are respectively a first beam expansion metasurface chip, a second beam expansion metasurface chip and a third beam expansion metasurface chip; the second-level metasurface chips in the second-level metasurface structure are a first optical rotator metasurface chip, a second optical rotator metasurface chip and a third optical rotator metasurface chip; the three fourth emergent lights output by the beam expansion metasurface chips are orthogonal to each other and overlap in the middle of the gas chamber; the first optical rotator metasurface chip, the second optical rotator metasurface chip and the third optical rotator metasurface chip fold back the light transmitted by the first beam expansion metasurface chip, the second beam expansion metasurface chip and the third beam expansion metasurface chip in the original path while changing the polarization state thereof, to obtain three fifth emergent lights; finally, the three lights folded back by the optical rotator metasurface chips and the three lights originally emitted by the beam expansion metasurface chips overlap in the central gas chamber, to realize the cooling and trapping of atoms, molecules or ions; The beam expanding metasurface chip is an array of nanostructure units composed of one or more high refractive index materials, and the beam expanding function is achieved by introducing the regulation of the incident light wave front when designing the nanostructure. The beam expanding is controlled by the phase distribution Φ(x, y) and satisfies the following formula: λ is the wavelength of light, f is the effective focal length, and r is the radial distance of the light beam, which is achieved by adjusting the period and arrangement of the nanostructure units. The beam expanding function is generated based on the quasi-parabolic wave front distribution, which is used to expand the light beam diameter from 100 um to 10 mm or more. The beam expanding metasurface chip is suitable for a wavelength range of 400 nm to 1200 nm and simultaneously has high beam expanding efficiency and polarization state conversion efficiency in this range. The optical rotator metasurface chip is an array of nanostructure units composed of a high refractive index material; the back reflection function is realized by a double-layer metasurface design or a single-layer special phase distribution, so that each nanostructure unit provides precise phase compensation for the light beam, and the direction of the reflected light is completely consistent with that of the incident light; in the single-layer scheme, the local polarization adjustment and wavefront reflection are simultaneously controlled through the combination regulation of PB phase rotation; in the double-layer scheme, the first layer realizes wavefront shaping, and the second layer realizes light beam back reflection, and the two layers jointly ensure that the direction and path of the light beam are completely consistent; each nanostructure unit has independently designed geometric parameters, and the phase distribution of the nanostructure array satisfies the back reflection condition, so that the incident light returns along the original path after passing through the optical rotator metasurface chip, and the back reflection of light beams of different wavelengths can be realized at the same time.

2. The on-chip integrated three-dimensional magneto-optical trap device of claim 1, wherein, The light beam forming structure comprises a light beam generating component, a first beam splitter with a one-to-three function, and three grating couplers; the light beam generating component is used to form a first emergent light and input the first emergent light into the first beam splitter; the first beam splitter is used to perform a light splitting operation on the first emergent light to form three second emergent lights; the three second emergent lights are transmitted to the three grating couplers respectively, each grating coupler converts the second emergent light into a third emergent light with a preset angle, and each third emergent light is guided to a first-level metasurface chip; Or, The light beam forming structure comprises three groups of light beam generating components and three grating couplers; the light beam generating components are used to form three first emergent lights; the three first emergent lights are transmitted to the three grating couplers respectively, each grating coupler converts the first emergent light into a third emergent light with a preset angle, and each third emergent light is guided to a first-level metasurface chip.

3. The on-chip integrated three-dimensional magneto-optical trap device of claim 1, wherein, The light beam generating component comprises a laser or a plurality of lasers, a frequency locking component, a laser frequency control component, an acousto-optic modulator, and a polarization controller; The frequency locking component comprises a photodiode and a feedback control circuit, and is used to lock the optical frequency of the laser to a reference frequency; The laser frequency control component is a frequency shifter or a laser frequency controller, and is used to lock the optical frequency of the pre-stabilized light beam generating component to an optical frequency related to at least one atomic transition; The acousto-optic modulator is used to simultaneously realize laser beam modulation and laser frequency control; The polarization controller is used to ensure that the laser output is a single polarization state light beam.

4. The on-chip integrated three-dimensional magneto-optical trap device of claim 1, wherein, The fourth emergent light is circularly polarized light.

5. The on-chip integrated three-dimensional magneto-optical trap device of claim 1, wherein, Three first-level metasurface chips are arranged on the lower outer side of the first gas chamber; three second-level metasurface chips are arranged on the upper outer side of the first gas chamber; each first-level metasurface chip is centrosymmetric to the second-level metasurface chip on which the fourth emergent light is incident, with respect to the center position of the first gas chamber.

6. The on-chip integrated three-dimensional magneto-optical trap device of claim 1, wherein, The extension lines of the center positions of the three grating couplers intersect at the inside of the first gas chamber; the included angle of the three extension lines is 120 degrees.

7. An on-chip integrated three-dimensional magneto-optical trap device, characterized by, The on-chip integrated three-dimensional magneto-optical trap device comprises a light beam forming structure, a third-level metasurface structure, a fourth-level metasurface structure, a second gas chamber, and a second coil component; The light beam forming structure comprises a light beam generating component, a second beam splitter with a one-to-two function, a third beam splitter and a fourth beam splitter with a one-to-three function, a first-level grating coupling structure, and a second-level grating coupling structure; the first-level grating coupling structure comprises three first-level grating couplers; the second-level grating coupling structure comprises three second-level grating couplers; the third-level metasurface structure comprises three third-level metasurface chips with a function of regulating and controlling direction and polarization state; and the fourth-level metasurface structure comprises three fourth-level metasurface chips with a function of regulating and controlling direction and polarization state. The light beam generating component is used to form sixth emergent light and input the sixth emergent light to the second beam splitter; the second beam splitter is used to perform light splitting operation on the sixth emergent light to form two seventh emergent lights; the two seventh emergent lights are transmitted to a third beam splitter and a fourth beam splitter respectively, the third beam splitter and the fourth beam splitter perform light splitting operation on the seventh emergent light to form three eighth emergent lights respectively; the three eighth emergent lights formed by the third beam splitter are incident to three first-level grating couplers respectively; the three eighth emergent lights formed by the third beam splitter are incident to three second-level grating couplers respectively; The first-level grating couplers are used to convert the eighth emergent light into a light beam in space and amplify the mode spot of the light beam to form three first-level ninth emergent lights; the three first-level ninth emergent lights are incident to three third-level metasurface chips respectively; the second-level grating couplers are used to convert the eighth emergent light into a light beam in space and amplify the mode spot of the light beam to form three second-level ninth emergent lights; the three second-level ninth emergent lights are incident to three fourth-level metasurface chips respectively; The third-level metasurface chips are used to refract and regulate the polarization state of the first-level ninth emergent light to form three first-level tenth emergent lights; the fourth-level metasurface chips are used to refract and regulate the polarization state of the second-level ninth emergent light to form three second-level tenth emergent lights; the three first-level tenth emergent lights and the three second-level tenth emergent lights converge at the center position of the second gas chamber; The second gas chamber is used to cool and trap atoms, molecules or ions by the magnetic field generated by the second coil component, the first-level tenth emergent light and the second-level tenth emergent light; The three third-level metasurface chips are a fourth rotary mirror metasurface chip, a fifth rotary mirror metasurface chip and a sixth rotary mirror metasurface chip; the three fourth-level metasurface chips are a first polarization transformation type metasurface chip, a second polarization transformation type metasurface chip and a third polarization transformation type metasurface chip; The rotary mirror metasurface chip is an array of nano structure units composed of high refractive index material, the reflection function is realized by double-layer metasurface design or single-layer special phase distribution, so that each nano structure unit provides accurate phase compensation for the light beam, and the direction of the reflected light is completely consistent with that of the incident light; the single-layer scheme: through the combination regulation of PB phase rotation, the local polarization adjustment and wavefront reflection are simultaneously controlled; the double-layer scheme: the first layer realizes wavefront shaping, and the second layer realizes light beam reflection, and the two layers jointly ensure that the light beam direction and path are completely consistent; each nano structure unit has independently designed geometric parameters, and the phase distribution of the nano structure nano array satisfies the reflection condition, so that the incident light returns along the original path after passing through the rotary mirror metasurface chip, and the reflection of different wavelengths of light can be realized at the same time; The polarization conversion type super surface chip is an array of nano structure units composed of one or more high refractive index materials, each nano structure unit has independently designed collective parameters including height, width and shape; by geometric rotation or shape design of the nano structure unit, polarization state conversion of incident light is realized, which is linear polarization conversion to circular polarization; wherein, the period of the nano structure unit is less than the wavelength of the incident light to suppress high order diffraction; the polarization state conversion is based on PB phase principle, the PB phase is controlled by the unit rotation angle, the value is 2θ, the thickness of the nano structure unit is between 300nm and 600nm to realize high diffraction efficiency, the nano structure unit has polarization state conversion function in the wavelength range of 400nm to 1200nm.

8. The on-chip integrated three-dimensional magneto-optical trap device of claim 7, wherein, The tenth exit light of the first level is right circularly polarized light, and the tenth exit light of the second level is left circularly polarized light; the angle between the tenth exit light of the first level and the second level and the horizontal direction is 60 degrees.

9. The on-chip integrated three-dimensional magneto-optical trap device of claim 7, wherein, Three third level super surface chips are arranged on the upper outer side of the second air chamber; three fourth level super surface chips are arranged on the lower outer side of the second air chamber.

10. The on-chip integrated three-dimensional magneto-optical trap device of claim 7, wherein, The extension lines of the center positions of the three first level grating couplers intersect at a point; the three second level grating couplers are arranged in parallel.

Images