On-chip integrated three-dimensional magneto-optical trap device

Abstract

The invention discloses an on-chip integrated three-dimensional magneto-optical trap device, and relates to the field of magneto-optical trap device integration, the device comprises a light beam forming structure, a two-layer metasurface chip, 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 carrying out beam splitting operation on emergent light of the laser, and the grating coupler is used for carrying out beam splitting operation on the emergent light of the laser; a plurality of output lights formed by the beam splitter are incident to the grating coupler, emergent lights of the grating coupler are respectively guided to the two layers of metasurface chips, the two layers of metasurface chips carry out polarization state regulation and control on the emergent lights of the grating coupler, and finally, the obtained emergent lights are converged or intersected at the central position of the gas chamber. The metasurface chip is used for cooling and trapping atoms, molecules or ions, a traditional lens structure is replaced by the metasurface chip, the size of the magneto-optical trap device is reduced, and the integration level 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 in particular to an on-chip integrated three-dimensional magneto-optical trap device. Background Art

[0002] Magneto-Optical Trap (MOT) technology has become the backbone of the laser cooling field with its excellent cooling and atom trapping capabilities. MOT technology enables atoms to be cooled to extremely low temperatures close to absolute zero, making it possible to explore the properties of matter at extremely low kinetic energy. To date, MOT has made remarkable achievements in the fields of laser cooling and atom trapping, and is widely used in cutting-edge scientific and technological fields such as high-precision atomic clocks, quantum computers, quantum networks, and quantum memories. The traditional three-dimensional magneto-optical trap system uses six orthogonal laser beams and the magnetic field generated by the anti-Helmholtz coil to capture and cool neutral atoms. However, the optical path in the traditional MOT system relies on complex laser devices, optical components, and precise alignment processes, and has problems such as large size, complex operation, and high maintenance costs, which limits 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 bulky optical system. A common method is to use three sets of gratings to form a pyramid-shaped emitter, thereby replacing part of the optical structure. Although the current MOT structure is already highly integrated, it is still relatively large in size because it still requires traditional lenses to adjust the optical path. Therefore, there is an urgent need for a more compact on-chip integrated three-dimensional magneto-optical trap device. Summary of the invention

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

[0005] To achieve the above objectives, this application provides the following solutions:

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

[0007] The beam forming structure is used to form three third outgoing lights; the first-level metasurface structure includes three first-level metasurface chips with beam expansion and polarization state adjustment functions; the second-level metasurface structure includes three second-level metasurface chips with polarization state adjustment functions; each beam of third outgoing light is guided to a first-level metasurface chip;

[0008] The first-level metasurface chip is used to expand the third output light and adjust the polarization state to form three fourth output lights, and each fourth output light is incident on a second-level metasurface chip; the second-level metasurface chip is used to adjust the polarization state of the fourth output light to form three fifth output lights, and each fifth output light is returned to the original path to be incident on the corresponding first-level metasurface chip; the three fourth output lights and the three fifth output lights intersect at the center of the first air chamber;

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

[0010] Optionally, the beam forming structure includes a beam generating component, a first beam splitter with a one-to-three function, and three grating couplers; the beam generating component is used to form a first outgoing light, and the first outgoing light is input to the first beam splitter; the first beam splitter is used to perform a splitting operation on the first outgoing light to form three beams of second outgoing light; the three beams of second outgoing light are respectively transmitted to three grating couplers, each grating coupler converts the second outgoing light into a third outgoing light with a preset angle, and guides each beam of the third outgoing light to a first-level metasurface chip;

[0011] or,

[0012] The beam forming structure includes three groups of beam generating components and three grating couplers; the beam generating components are used to form three beams of first outgoing light; the three beams of first outgoing light are respectively transmitted to three grating couplers, each grating coupler converts the first outgoing light into a third outgoing light with a preset angle, and guides each beam of third outgoing light to a first-level metasurface chip.

[0013] Optionally, the beam generating means comprises a laser or a plurality of lasers, a frequency locking means, a laser frequency controlling means, an acousto-optic modulator and a polarization controller;

[0014] The frequency locking component includes a photodiode and a feedback control circuit, and is used to lock the optical frequency of the laser to a reference frequency;

[0015] The laser frequency control member is a frequency shifter or a laser frequency controller, which is used to lock the optical frequency of the pre-stabilized beam generating member to the optical frequency associated with at least one atomic transition;

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

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

[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; three second-level metasurface chips are arranged on the upper outer side of the first air chamber; each first-level metasurface chip and the second-level metasurface chip on which the emitted fourth output light is incident are centrally symmetrical about the center position of the first air chamber.

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

[0021] In a second aspect, the present application provides another 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 member;

[0022] The beam forming structure includes a 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 includes three first-level grating couplers; the second-level grating coupling structure includes three second-level grating couplers; the third-level metasurface structure includes three third-level metasurface chips with functions of regulating direction and polarization state; the fourth-level metasurface structure includes three fourth-level metasurface chips with functions of regulating direction and polarization state;

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

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

[0025] The third-level metasurface chip is used to refract and adjust the polarization state of the ninth outgoing light of the first level to form three beams of the tenth outgoing light of the first level; the fourth-level metasurface chip is used to refract and adjust the polarization state of the ninth outgoing light of the second level to form three beams of the tenth outgoing light of the second level; the three beams of the tenth outgoing light of the first level and the three beams of the tenth outgoing light of the second level converge at the center of the second air chamber;

[0026] The second gas chamber is used to cool and trap atoms, molecules or ions through 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 tenth emergent light of the first level is right-handed circularly polarized light, and the tenth emergent light of the second level is left-handed circularly polarized light; and the angle between the tenth emergent light of the first level and the tenth emergent light of the second level and the horizontal direction is 60 degrees.

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

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

[0030] According to the specific embodiments provided in this application, this application discloses the following technical effects:

[0031] The present application provides an on-chip integrated three-dimensional magneto-optical trap device, a beam forming structure, two-level metasurface chips, an air chamber and a coil component. The beam forming structure includes a laser, a beam splitter and a grating coupler. The beam splitter is used to split the output light of the laser, and the multiple output lights formed by the beam splitter are incident on the grating coupler. The output lights of the grating coupler are respectively introduced into the two-level metasurface chips. The two-level metasurface chips regulate the polarization state of the output light of the grating coupler. The output lights finally obtained converge or intersect at the center of the air chamber for cooling and trapping atoms, molecules or ions. The present application integrates the optical path part on chip, and replaces the traditional lens structure with metasurface chips with different functions, thereby reducing the volume of the magneto-optical trap device and improving the integration of the magneto-optical trap device. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0033] Figure 1 A schematic structural diagram of an on-chip integrated three-dimensional magneto-optical trap device provided in one embodiment of the present application;

[0034] Figure 2 A schematic diagram of the optical path of a pair of beam expansion metasurface chips and a gyroscopic metasurface chip provided in one embodiment of the present application;

[0035] Figure 3 A schematic structural diagram of a light beam generating component provided in one embodiment of the present application;

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

[0037] Reference numerals:

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

[0039] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0040] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

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

[0042] The beam forming structure is used to form three third outgoing lights; the first-level metasurface structure includes three first-level metasurface chips with beam expansion and polarization state adjustment functions; the second-level metasurface structure includes three second-level metasurface chips with polarization state adjustment functions; each beam of third outgoing light is guided to a first-level metasurface chip;

[0043] The first-level metasurface chip is used to expand the third outgoing light and adjust the polarization state to form three fourth outgoing light beams, and each fourth outgoing light beam is incident on a second-level metasurface chip; the second-level metasurface chip is used to adjust the polarization state of the fourth outgoing light to form three fifth outgoing light beams, and each fifth outgoing light beam is returned to the original path to be incident on the corresponding first-level metasurface chip; the three fourth outgoing light beams and the three fifth outgoing light beams intersect at the center of the first air chamber 10;

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

[0045] Among them, the beam forming structure can include two implementation schemes:

[0046] The first solution: the beam forming structure includes 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 output light 1, and the first output light is input to the first beam splitter 2; the first beam splitter 2 is used to perform a splitting operation on the first output light to form three beams of second output light; the three beams of second output light are respectively transmitted to three grating couplers, each grating coupler converts the second output light into a third output light with a preset angle, and guides each beam of the third output light to a first-level metasurface chip. Figure 1 To integrate a three-dimensional magneto-optical trap device on a chip under the first scheme.

[0047] The second solution: the beam forming structure includes three groups of beam generating components and three grating couplers; the beam generating components are used to form three beams of first outgoing light; the three beams of first outgoing light are respectively transmitted to three grating couplers, each grating coupler converts the first outgoing light into a third outgoing light with a preset angle, and guides each beam of third outgoing light to a first-level metasurface chip.

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

[0049] The beam generating component also includes one or more lasers, a frequency locking component, a laser frequency control component, an acousto-optic modulator and a polarization controller; the frequency locking component includes a photodiode and a feedback control circuit, which 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, which is used to lock the optical frequency of the pre-stabilized laser to an optical frequency associated with 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 including an atomic frequency reference and an optical cavity frequency reference. The acousto-optic modulator is used to simultaneously realize laser beam modulation and laser frequency control, and adjust the input laser power according to different requirements to meet the requirements of cooling and trapping atoms; the polarization controller is used to ensure that the laser output is a beam of a single polarization state, which is convenient for the subsequent metasurface chip to regulate the polarization state of the beam.

[0050] like Figure 3 As shown, the cooling light and the re-pumping light are generated by two lasers respectively, or one laser is divided into two paths to generate the cooling light and the re-pumping light. Figure 1 and Figure 4 Connected to the beam splitter in.

[0051] The optical frequency of the laser matches a transition selected from the group consisting of virtual atomic transitions, multiphoton transitions, direct transitions, and indirect transitions. The optical frequency of the laser is selected from a list consisting of 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-tuned to a fixed frequency when used. This can be consistent with the atomic transition frequency, the multiphoton transition frequency, the atomic direct transition frequency, or the atomic indirect transition frequency.

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

[0053] Figure 1In the embodiment, the extension lines of the center positions of the three grating couplers intersect inside the first air chamber 10; the angle between the three extension lines is 120 degrees. And each grating coupler is etched to emit a free-space beam at a selected angle, wherein the selected angle causes a group of free-space beams to intersect at a certain position inside the first air chamber 10 after passing through the first-level and second-level metasurface chips respectively. All free-space beams from the three grating couplers pass through the first-level and second-level metasurface chips respectively and enter the first air chamber 10 through at least one wall of the first air chamber 10. The grating coupler is configured to emit a polarization selected from a combination of circular polarization, elliptical polarization, and engineered polarization. The grating coupler is configured to emit an intensity profile selected from the group consisting of flat top, Gaussian, and engineered intensity profiles.

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

[0055] The laser is used to form a first outgoing light, and the first outgoing light is input to the first beam splitter 2; the first beam splitter 2 is used to split the first outgoing light to form three second outgoing lights; the three second outgoing lights are respectively transmitted to three grating couplers, each grating coupler converts the second outgoing light into a third outgoing light with a preset angle, and guides each third outgoing light to a first-level metasurface chip. The preset angle can range from 0 to 90 degrees.

[0056] The first-level metasurface structure includes three first-level metasurface chips with the functions of beam expansion and polarization state regulation; the second-level metasurface structure includes three second-level metasurface chips with the function of polarization state regulation. Among them, the first-level metasurface chip is a beam expansion metasurface chip, and the second-level metasurface chip is a gyroscopic metasurface chip. The first-level metasurface chips in the first-level metasurface structure are named the first beam expansion metasurface chip 6, the second beam expansion metasurface chip 7, and the third beam expansion metasurface chip 8; the second-level metasurface chips in the second-level metasurface structure are named the first gyroscopic metasurface chip 9, the second gyroscopic metasurface chip 12, and the third gyroscopic metasurface chip 11.

[0057] The metasurface chips are all located around the first air chamber 10. Three first-level metasurface chips are arranged on the lower outside of the first air chamber 10, that is, three beam expansion metasurface chips, which are installed around the first air chamber 10 near the bottom; three second-level metasurface chips are arranged on the upper outside of the first air chamber 10, that is, three cyclotron metasurface chips, which are installed around the atomic first air chamber 10 near the top; each first-level metasurface chip is symmetrical with the second-level metasurface chip on which the emitted fourth output light is incident about the center position of the first air chamber 10.

[0058] The first-level metasurface chip is used to expand the third output light and adjust the polarization state to form three fourth output lights, and each fourth output light is incident on a second-level metasurface chip; the second-level metasurface chip is used to adjust the polarization state of the fourth output light to form three fifth output lights, and each fifth output light is returned to the original path to be incident on the corresponding first-level metasurface chip; the three fourth output lights and the three fifth output lights intersect at the center of the first air chamber 10, so that the six light beams intersect at a certain position inside the first air chamber 10, and finally the six light beams overlap inside the first air chamber 10.

[0059] The fourth output light is circularly polarized light. The first-level metasurface chip is used to achieve beam expansion and convert the polarization state of the beam into circularly polarized light (such as converting linear polarized light into circularly polarized light). At least one first-level metasurface chip is configured to emit polarization in a combination of circular polarization and elliptical polarization, and at least one first-level metasurface chip is configured to expand the spot diameter from micrometer size to millimeter size.

[0060] The second-level metasurface chip is used to realize the reflection of the light beam and the control of the circular polarization state. The second-level metasurface chip is configured to fold the incident light back along its original path and change the circular polarization state at the same time. For example, when the fourth output light is left-handed circularly polarized light, the fifth output light is right-handed circularly polarized light, and when the fourth output light is right-handed circularly polarized light, the fifth output light is left-handed circularly polarized light.

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

[0062] In another exemplary embodiment of the present application, the present application can use a photon-integrated fiber-coupled photonic chip to achieve laser cooling and trapping of atoms in a three-dimensional magneto-optical trap. In addition to cooling and trapping, other light beams can also be used, such as atomic interrogation and optical transitions or clock readouts. In general, magneto-optical traps are used for neutral atoms, but ions and molecules can also be cooled and trapped. The photonic chip directly inputs cooling and re-pumping light and other light beams into the atomic gas chamber, and ion and molecular gas chambers are also possible, including their mixtures. 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 expansion, collimation and atomic gas chamber beams and magneto-optical traps and atomic, ion and molecular systems and other required functions.

[0063] Cold atoms are critical for precision atomic applications, including time keeping and sensing. In general, atoms, ions, molecules and their combinations can be used in precision scientific experiments and applications, and three-dimensional magneto-optical traps can be used to produce cold atoms, ions and molecular clouds. The three-dimensional magneto-optical trap can be improved by photonic waveguide integration, which can improve reliability and reduce size, weight and cost. Photonic integration can also improve the performance of the MOT by providing phase and optical stability as well as precision laser and optical performance. In this embodiment, the three-dimensional magneto-optical trap may require multiple, large-area and / or collimated laser beams to be delivered to the 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 magneto-optical trap 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 atomic sensors. In this embodiment, 87 Rb 3D MOT can use fiber-coupled photonic integrated circuits to deliver all necessary beams to cool and trap over 1x10 6 atoms, bringing them to nearly 200 μK in the trapping volume. In this embodiment, the trapping volume can be an order of magnitude smaller than a diffraction grating MOT with an equivalent number of atoms. A diffraction grating MOT is an example of a non-integrated bulk optical technology. Lower temperatures can be achieved by introducing other lasers and beams that use photonic integrated optical circuits to cool the atoms to sub-Doppler temperatures, such as introducing 20 μK in the trapping volume. Lower temperatures can be used for applications such as Bose-Einstein condensates (BECs) and atom interferometry. Other types of gratings may be desirable and necessary, such as gratings for lattice trap beam delivery, gratings for Raman cooling 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 exemplary embodiment of the present application, a photonic integrated optical circuit with a silicon nitride substrate can convert the fiber-coupled 780 nm cooling and re-pumping light provided by the laser into a chip waveguide (e.g., a waveguide mounted on the photonic integrated optical circuit). Other wavelengths can also be provided depending on the requirements of a specific atomic or molecular species. For example, neutral strontium may require 461 nm, 816 nm, 689 nm, 679 nm, 707 nm, and 728 nm for cooling, magic lattices, re-pumping, and optical clock transitions. Trapped strontium ions may require 422 nm, 461 nm, 405 nm, and 674 nm for cooling and optical clock transitions. The chip integrated waveguide can convert the provided cooling and re-pumping light into three orthogonal non-divergent free-space cooling and re-pumping beams (e.g., 2.5 mm × 3.5 mm free-space cooling and re-pumping beams) by transforming waveguides and / or waveguide gratings. Other beam configurations are possible and may be desirable and are not limited here. In a specific embodiment, three orthogonal non-divergent free-space cooling and re-pumping beams can be directly interfaced with the rubidium gas cell to cool and trap atoms. In this embodiment, a completely planar, CMOS foundry-compatible on-chip integrated 3D magneto-optical trap device can be equipped with waveguides and emitters to provide cooling and / or re-pumping beams to the atomic gas cell. In this embodiment, the on-chip integrated 3D magneto-optical trap device can include lasers and modulators for a system-on-chip solution for cold atom applications.

[0065] Figure 1The working principle of the on-chip integrated three-dimensional magneto-optical trap device is as follows: The on-chip integrated three-dimensional magneto-optical trap device uses optical fiber to transmit laser to achieve atomic cooling and trapping. It includes optical fiber, beam splitter, grating coupler, beam expansion metasurface chip, gyroscopic mirror metasurface chip and gas chamber. The first output light is emitted by the laser and transmitted to the first beam splitter 2 through the optical fiber, and is divided into three second output lights through the first beam splitter 2. The second output light is transmitted to the first grating coupler 3, the second grating coupler 4 and the third grating coupler 5 respectively. The free space light beam (third output light) is emitted at a preset angle through the first grating coupler 3, the second grating coupler 4 and the third grating coupler 5, and the angle between each grating coupler is about 120 degrees. A beam expansion metasurface chip is placed obliquely above each grating coupler. The first beam expansion metasurface chip 6, the second beam expansion metasurface chip 7 and the third beam expansion 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 at the same time adjust the polarization state of the third outgoing light so that its output polarization state is the fourth outgoing light of circular polarized light. The three beams of fourth outgoing light outputted by the beam expansion metasurface are orthogonal to each other and overlap in the middle of the air chamber (the light beams are represented by obliquely placed cylinders). Three gyroscopic metasurface chips are arranged on the outer side of the air chamber at the top. The first gyroscopic metasurface chip 9, the second gyroscopic metasurface chip 12 and the third gyroscopic metasurface chip 11 fold back the original path of the light transmitted by the first beam expansion metasurface chip 6, the second beam expansion metasurface chip 7 and the third beam expansion metasurface chip 8, and at the same time change its polarization state to obtain three beams of fifth outgoing light. Eventually, the three beams of light reflected back by the cyclotron metasurface chip and the three beams of light initially emitted by the beam expansion metasurface chip will overlap in the center of the gas chamber, achieving the cooling and trapping of atoms, molecules or ions.

[0066] Figure 2 In the process, the light beam is emitted by the grating coupler, and the beam expansion function is realized through the beam expansion metasurface chip, and the polarization state of the light beam is converted into circularly polarized light output (the angles in the figure are only examples and are not limited to this application). The circularly polarized light output by the beam expansion metasurface chip (which may be left-handed circularly polarized light or right-handed circularly polarized light) is directed to the interior of the air chamber, and then transmitted to the gyroscopic metasurface chip. The gyroscopic metasurface chip folds the incident light back along the original path and regulates the polarization state. In this way, a group (two beams) of light beams are formed for cooling atoms, molecules or ions. Six-beam light cooling and trapping of atoms, molecules or ions can be achieved through three groups of metasurface chips.

[0067] In another exemplary embodiment of the present application, Figure 4 As shown, the present application also provides another on-chip integrated three-dimensional magneto-optical trap device, which includes: a beam forming structure, a third-level metasurface structure, a fourth-level metasurface structure, a second air chamber 30 and a second coil component. The second coil component includes a third coil 31 and a fourth coil 32.

[0068] The beam forming structure includes a beam generating component, a second beam splitter 15 with a one-to-two function, a third beam splitter 16 and a fourth beam splitter 17 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 includes three first-level grating couplers; the second-level grating coupling structure includes three second-level grating couplers; the third-level metasurface structure includes three third-level metasurface chips with the function of adjusting direction and polarization state; the fourth-level metasurface structure includes three fourth-level metasurface chips with the function of adjusting direction and polarization state.

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

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

[0071] The light beam generating component is used to form a sixth output light, and input the sixth output light to the second beam splitter 15; the second beam splitter 15 is used to perform a splitting operation on the sixth output light to form two beams of seventh output light; the two beams of seventh output 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 perform a splitting operation on the seventh output light to form three beams of eighth output light respectively; the three beams of eighth output light formed by the third beam splitter 16 are respectively incident on three first-level grating couplers; the three beams of eighth output light formed by the third beam splitter 16 are respectively incident on three second-level grating couplers.

[0072] The first-level grating coupler is used to convert the eighth output light into a light beam in space, and amplify the mode spot of the light beam to form three first-level ninth output lights; the three first-level ninth output lights are respectively incident on three third-level metasurface chips; the second-level grating coupler is used to convert the eighth output light into a light beam in space, and amplify the mode spot of the light beam to form three second-level ninth output lights; the three second-level ninth output lights are respectively incident on three fourth-level metasurface chips.

[0073] The third-level metasurface chip is used to refract and adjust the polarization state of the ninth outgoing light of the first level to form three beams of the tenth outgoing light of the first level; the fourth-level metasurface chip is used to refract and adjust the polarization state of the ninth outgoing light of the second level to form three beams of the tenth outgoing light of the second level; the three beams of the tenth outgoing light of the first level and the three beams of the tenth outgoing light of the second level converge at the center of the second air chamber 30;

[0074] The second gas chamber 30 is used to cool and trap atoms, molecules or ions through the first-level tenth outgoing light and the second-level tenth outgoing light.

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

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

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

[0078] Figure 4The working principle of the on-chip integrated three-dimensional magneto-optical trap device is as follows: the laser output light (sixth output light) is firstly split into two second output lights by a one-to-two beam splitter, transmitted to a one-to-three beam splitter through a waveguide, split into six eighth output lights by a one-to-three beam splitter, and respectively input into six grating couplers. The light beam in the waveguide is converted into a light beam in space by a first-level first grating coupler 18, a first-level second grating coupler 19, a first-level third grating coupler 20, a second-level first grating coupler 21, a second-level second grating coupler 22, and a second-level third grating coupler 23, and the pattern spot of the light beam is amplified at the same time, so as to obtain three first-level ninth output lights and three second-level ninth output lights. Among them, the first-level first grating coupler 18, the first-level second grating coupler 19, and the first-level third grating coupler 20 are respectively connected to the fourth gyroscopic metasurface chip 27, the fifth gyroscopic metasurface chip 28, and the sixth gyroscopic metasurface chip 29. The fourth gyroscopic metasurface chip 27, the fifth gyroscopic metasurface chip 28, and the sixth gyroscopic metasurface chip 29 refract the input first-level ninth output light, and the angle with the horizontal direction is about 60 degrees, and the input light is converted into right-handed circularly polarized light, that is, the first-level tenth output light is right-handed circularly polarized light, and then connected to the second air chamber 30. The second-level first grating coupler 21, the second-level second grating coupler 22, and the second-level third grating coupler 23 are connected to 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 outgoing light incident by the second-level first grating coupler 21, the second-level second grating coupler 22, and the second-level third grating coupler 23 into left-handed circularly polarized light output, and the output second-level tenth outgoing light has an angle of about 60 degrees with the horizontal direction. Finally, six beams of light (three beams of the first-level tenth outgoing light and three beams of the second-level tenth outgoing light) are simultaneously input into the center of the second gas chamber to achieve cooling and trapping of atoms, molecules, or ions.

[0079] Polarization conversion metasurface chip: an array of nanostructure units composed of one or more high-refractive index materials, each nanostructure unit has independently designable collective parameters, including height, width and shape. By geometrically rotating or designing the shape of the nanostructure unit, the polarization state conversion of the incident light is achieved, mainly the conversion of linear polarization to circular polarization. Among them, the period of the nanostructure unit is smaller than the wavelength of the incident light to suppress high-order diffraction. The material of the nanostructure unit is a high-refractive index, 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 unit rotation angle, and its value is 2θ. Among them, the thickness of the nanostructure unit is between 300nm and 600nm to achieve high diffraction efficiency. The nanostructure unit has a polarization state conversion function within the wavelength range of 400nm to 1200nm.

[0080] Beam expansion metasurface chip: Based on the polarization conversion metasurface chip, the beam expansion function is added to obtain a beam expansion metasurface chip (the design of the polarization conversion part of the beam expansion metasurface chip is consistent with the previous one). The beam expansion function is mainly achieved by introducing the control of the incident light wavefront when designing the nanostructure. The beam expansion is controlled by the phase distribution Φ(x,y), which 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 unit. The beam expansion function is generated based on the quasi-parabolic wavefront distribution and is used to expand the beam diameter from 100um to 10mm or more. The nanostructure unit includes an elliptical, rectangular or L-shaped structure. Among them, the beam expansion metasurface chip is suitable for a wavelength range of 400nm to 1200nm, and has high beam expansion efficiency and polarization state conversion efficiency within this range.

[0081] Gyroscopic metasurface chip: The reflective function can be achieved through 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, so that the direction of the reflected light is exactly the same as the incident light. Single-layer solution: Through the combined regulation of PB phase rotation, local polarization regulation and wavefront reflection can be controlled simultaneously. Double-layer solution: The first layer realizes wavefront shaping, and the second layer realizes beam reflective. The two layers work together to ensure that the direction and path of the beam are exactly the same. High-refractive index and low-loss materials (such as titanium dioxide, gallium nitride or silicon) are used in the selection of materials to improve the reflection efficiency. Specifically, it is an array of nanostructure units composed of high-refractive index materials, each nanostructure unit has independently designable geometric parameters, and the phase distribution of the nanostructure nanoarray meets the reflective conditions, so that the incident light returns along the original path after passing through the gyroscopic metasurface chip, and can simultaneously realize efficient reflective reflection of light of different wavelengths, with a reflection efficiency of more than 90%.

[0082] The on-chip integrated three-dimensional magneto-optical trap device provided by the present application only needs one beam of light input to realize atomic trapping and cooling, and realizes the integration of the on-chip three-dimensional magneto-optical trap device through the combination of a beam splitter, a grating coupler, a beam expansion metasurface chip, and a gyroscopic metasurface chip. Compared with the existing solutions, the present application uses a metasurface chip to replace the traditional wave plate, and through the combination of a beam expansion metasurface chip and a gyroscopic 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 may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0084] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, according to the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. An on-chip integrated three-dimensional magneto-optical trap device, characterized in that: The on-chip integrated three-dimensional magneto-optical trap device comprises: a beam forming structure, a first-level supersurface structure, a second-level supersurface structure, a first air chamber and a first coil component; The beam forming structure is used to form three third outgoing lights; the first-level metasurface structure includes three first-level metasurface chips with beam expansion and polarization state adjustment functions; the second-level metasurface structure includes three second-level metasurface chips with polarization state adjustment functions; each beam of third outgoing light is guided to a first-level metasurface chip; The first-level metasurface chip is used to expand the third output light and adjust the polarization state to form three fourth output lights, and each fourth output light is incident on a second-level metasurface chip; the second-level metasurface chip is used to adjust the polarization state of the fourth output light to form three fifth output lights, and each fifth output light is returned to the original path to be incident on the corresponding first-level metasurface chip; the three fourth output lights and the three fifth output lights intersect at the center of the first air chamber; The first gas chamber is used to cool and trap atoms, molecules or ions through the magnetic field generated by the first coil component, the fourth output light and the fifth output light.

2. The on-chip integrated three-dimensional magneto-optical trap device according to claim 1, characterized in that: The beam forming structure includes a beam generating component, a first beam splitter with a one-to-three function, and three grating couplers; the beam generating component is used to form a first outgoing light, and the first outgoing light is input to the first beam splitter; the first beam splitter is used to perform a splitting operation on the first outgoing light to form three beams of second outgoing light; the three beams of second outgoing light are respectively transmitted to three grating couplers, each grating coupler converts the second outgoing light into a third outgoing light with a preset angle, and guides each beam of the third outgoing light to a first-level metasurface chip; or, The beam forming structure includes three groups of beam generating components and three grating couplers; the beam generating components are used to form three beams of first outgoing light; the three beams of first outgoing light are respectively transmitted to three grating couplers, each grating coupler converts the first outgoing light into a third outgoing light with a preset angle, and guides each beam of third outgoing light to a first-level metasurface chip.

3. The on-chip integrated three-dimensional magneto-optical trap device according to claim 1, characterized in that: The beam generating means comprises a laser or a plurality of lasers, a frequency locking means, a laser frequency controlling means, an acousto-optic modulator and a polarization controller; The frequency locking component includes 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 member is a frequency shifter or a laser frequency controller, which is used to lock the optical frequency of the pre-stabilized beam generating member to the optical frequency associated with 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 light beam in a single polarization state.

4. The on-chip integrated three-dimensional magneto-optical trap device according to claim 1, characterized in that: The fourth emitted light is circularly polarized light.

5. The on-chip integrated three-dimensional magneto-optical trap device according to claim 1, characterized in that: Three first-level metasurface chips are arranged on the lower outer side of the first air chamber; three second-level metasurface chips are arranged on the upper outer side of the first air chamber; each first-level metasurface chip and the second-level metasurface chip on which the emitted fourth outgoing light is incident are centrally symmetrical about the center position of the first air chamber.

6. The on-chip integrated three-dimensional magneto-optical trap device according to claim 1, characterized in that: The extension lines of the center positions of the three grating couplers intersect inside the first air chamber; the included angle of the three extension lines is 120 degrees.

7. An on-chip integrated three-dimensional magneto-optical trap device, characterized in that: The on-chip integrated three-dimensional magneto-optical trap device comprises: a beam forming structure, a third-level supersurface structure, a fourth-level supersurface structure, a second air chamber and a second coil component; The beam forming structure includes a 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 includes three first-level grating couplers; the second-level grating coupling structure includes three second-level grating couplers; the third-level metasurface structure includes three third-level metasurface chips with functions of regulating direction and polarization state; the fourth-level metasurface structure includes three fourth-level metasurface chips with functions of regulating direction and polarization state; The beam generating component is used to form a sixth outgoing light, and input the sixth outgoing light into the second beam splitter; the second beam splitter is used to perform a splitting operation on the sixth outgoing light to form two beams of seventh outgoing light; the two beams of seventh outgoing light are respectively transmitted to the third beam splitter and the fourth beam splitter, and the third beam splitter and the fourth beam splitter perform a splitting operation on the seventh outgoing light to form three beams of eighth outgoing light respectively; the three beams of eighth outgoing light formed by the third beam splitter are respectively incident on three first-level grating couplers; the three beams of eighth outgoing light formed by the third beam splitter are respectively incident on three second-level grating couplers; The first-level grating coupler is used to convert the eighth output light into a light beam in space, and amplify the mode spot of the light beam to form three first-level ninth output lights; the three first-level ninth output lights are respectively incident on three third-level metasurface chips; the second-level grating coupler is used to convert the eighth output light into a light beam in space, and amplify the mode spot of the light beam to form three second-level ninth output lights; the three second-level ninth output lights are respectively incident on three fourth-level metasurface chips; The third-level metasurface chip is used to refract and adjust the polarization state of the ninth outgoing light of the first level to form three beams of the tenth outgoing light of the first level; the fourth-level metasurface chip is used to refract and adjust the polarization state of the ninth outgoing light of the second level to form three beams of the tenth outgoing light of the second level; the three beams of the tenth outgoing light of the first level and the three beams of the tenth outgoing light of the second level converge at the center of the second air chamber; The second gas chamber is used to cool and trap atoms, molecules or ions through the magnetic field generated by the second coil component, the first-level tenth emergent light and the second-level tenth emergent light.

8. The on-chip integrated three-dimensional magneto-optical trap device according to claim 7, characterized in that: The tenth emergent light of the first level is right-handed circularly polarized light, and the tenth emergent light of the second level is left-handed circularly polarized light; the included angle between the tenth emergent light of the first level and the tenth emergent light of the second level and the horizontal direction is 60 degrees.

9. The on-chip integrated three-dimensional magneto-optical trap device according to claim 7, characterized in that: 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 according to claim 7, characterized in that: The extended lines of the center positions of the three first-level grating couplers intersect at one point; and the three second-level grating couplers are arranged in parallel.

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