Cold atom regulation and control chip device based on composite waveguide holographic grating

Abstract

The invention discloses a cold atom regulation and control chip device based on a composite waveguide holographic grating, and the structure is mainly composed of a silicon nitride waveguide disposed on a silicon dioxide substrate, and the silicon nitride waveguide comprises a group of x-direction waveguides and two groups of y-direction waveguides. A composite waveguide holographic grating G1 and a composite waveguide holographic grating G2 are respectively etched in the crossed area of the waveguides; the port of the y-direction waveguide is diffracted by the composite waveguide holographic grating G1 and the composite waveguide holographic grating G2 to generate two beams of vortex light, and the two beams of vortex light are intersected above the chip to form an optical dipole trap for trapping cold atoms; the x-direction waveguide is diffracted by the composite waveguide holographic grating G1 through the port Pin to generate Gaussian light, and the Gaussian light is focused and aligned with the center of the optical dipole trap. According to the invention, the functions of atom capture, atom internal state excitation and fluorescence detection can be realized on the chip, and the problem of contradictory integration compatibility of a device for regulating and controlling a plurality of cold atoms in the existing photon-atom chip is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of integrated optical information processing, and particularly relates to an integrated photon-atom chip device for cold atom control based on a composite waveguide holographic grating. Background Art

[0002] With the continuous development of technologies for laser cooling, trapping, and controlling cold atoms, cold atom systems have shown great application potential in fields such as precision measurement, quantum computing, and quantum information. However, traditional cold atom experimental systems usually consist of multiple complex components such as laser systems, vacuum systems, and electromagnetic systems, which are bulky and costly to maintain, limiting their feasibility in portable and large-scale applications.

[0003] Therefore, the prior art further proposed the concept of an integrated photon-atom chip, aiming to miniaturize the cold atom control system and improve its practicality through on-chip integration.

[0004] The integrated photon-atom chip uses micro-nano processing technology to construct microstructures on the chip surface to generate adjustable optical fields, electric fields, or magnetic fields for precise control of cold atoms. Compared with traditional experimental systems, this chip-based solution has the advantages of high integration, strong scalability, good environmental stability, and low cost, making it have broad application prospects in fields such as micro atomic clocks, quantum computing, quantum measurement, and quantum communication. For example, in quantum computing, photons can be used as carriers of quantum information, while atoms can be used as quantum bits, and efficient quantum information processing can be achieved through photon-atom coupling. In addition, the chip can be used in quantum repeaters and quantum key distribution systems in quantum communication to transmit quantum information over long distances using photons, and at the same time, a large-scale quantum network can be constructed through atomic storage and entanglement swapping.

[0005] Currently, photon-atom chip solutions for cold atom control have been proposed. For example, a magneto-optical trap is constructed using a diffraction grating structure to cool cold atoms to prepare a cold atom cloud, and then the cold atoms are controlled through on-chip free-space optical fields, or the cold atoms are controlled through strong coupling between the evanescent field on the waveguide surface and the atoms. However, these solutions have not integrated the functions of cold atom trapping, internal state excitation, and fluorescence collection on a single chip, limiting the compactness and practicality of the system.

[0006] Therefore, this application specifically proposes a cold atom control chip device based on a composite waveguide holographic grating to solve the above technical problems. Summary of the Invention

[0007] The main object of the present invention is to provide a cold atom control chip device based on a composite waveguide holographic grating, which can integrate multiple cold atom control functions onto the chip to achieve the capture and detection of cold atoms, so as to solve the technical problems proposed in the background art.

[0008] The present invention adopts the following technical solutions to solve the above technical problems: A cold atom control chip device based on a composite waveguide holographic grating, the structure of which is mainly composed of silicon nitride waveguides placed on a silica substrate. The silicon nitride waveguides are composed of two parallel waveguides and a waveguide perpendicular to them, specifically including a group of x-direction waveguides and two groups of y-direction waveguides. Composite waveguide holographic gratings G1 and G2 are respectively etched in the crossing regions of the waveguides; Two vortex lights are diffracted from the ports of the y-direction waveguides by the composite waveguide holographic gratings G1 and G2, and are used to intersect above the chip to form an optical dipole trap for confining cold atoms; The x-direction waveguide passes through the port Gaussian light is diffracted by the composite waveguide holographic grating G1, and is focused and aligned with the center of the optical dipole trap, and can act on the cold atoms confined therein.

[0009] Preferably, the y-direction waveguide passes through the port and The input blue-detuned TE0 mode generates two vortex lights diffracted by the composite waveguide holographic gratings G1 and G2. Preferably, the x-direction waveguide passes through the port The input TE0 mode generates Gaussian light diffracted by the composite waveguide holographic grating G1. According to the principle of optical path reversibility, the composite waveguide holographic grating G2 is used to collect atomic fluorescence and convert it into a waveguide mode, and is output to the detector through the port to realize the collection and detection of atomic fluorescence signals.

[0010] Preferably, the gap distances between the composite waveguide holographic gratings G1 and G2 are both set in the range of 1μm ± 0.2μm.

[0011] Preferably, both the composite waveguide holographic gratings G1 and G2 are formed by superimposing a holographic grating pattern R1 and a holographic grating pattern R2, where: The holographic grating pattern R1 is formed by interfering the TE0 mode of the y-direction waveguide as the reference light and the vortex light perpendicular to the waveguide surface as the target light; The holographic grating pattern R2 is formed by interfering the TE0 mode of the x-direction waveguide as the reference light and the Gaussian light perpendicular to the waveguide surface as the target light.

[0012] Preferably, the additional phase gradient in the x direction introduced by the vortex light in the holographic grating pattern R1 , by changing the phase gradient , realizes the directional emission of the diffracted vortex light in the x direction; The synthetic phase distribution of the holographic grating pattern R1 satisfies the following conditions:

[0013]

[0014]

[0015] Wherein, is the imaginary unit, is the order of the orbital angular momentum, which is used to determine the helical phase structure of the vortex light, is the azimuth angle, is the additional phase gradient introduced in the x direction, which is used to control the diffraction angle of the vortex light, is the effective wave vector of the waveguide mode propagating in the y direction, is the effective refractive index of the waveguide mode, is the excitation wavelength, is the vector of the beam propagation path, and respectively represent the unit vectors in the z direction and the y direction, is the focusing height, that is, the height of the beam focus relative to the grating plane, is the phase distribution of the vortex light.

[0016] Preferably, the phase gradients of the holographic grating patterns R1 of the composite waveguide holographic grating G1 and the composite waveguide holographic grating G2 have the same value but opposite signs, and the diffraction angles of the vortex lights generated by diffraction are the same in magnitude but opposite in direction. The two groups of vortex lights generated by diffraction converge above the center of the chip to form an optical dipole trap for confining cold atoms.

[0017] Preferably, the additional phase gradient introduced by the Gaussian light in the holographic grating pattern R2, by changing the phase gradient , realizes the directional emission of the Gaussian light in the x direction; The synthetic phase distribution of the holographic grating pattern R2 satisfies the following conditions:

[0018]

[0019]

[0020] Wherein, is the imaginary unit, is the effective wave vector of the waveguide mode propagating in the x direction, is the additional phase gradient introduced in the x direction, which is used to control the diffraction angle of the Gaussian light, is the coordinate of the center position of the grating pattern in the x direction, is the effective refractive index of the waveguide mode, is the excitation wavelength, is the vector of the light beam propagation path, and respectively represent the unit vectors in the z direction and the y direction, is the focusing height, that is, the height of the light beam focus relative to the grating plane, is the Gaussian light phase distribution.

[0021] Preferably, the linear phase gradients of the holographic patterns R2 of the composite waveguide holographic grating G1 and the composite waveguide holographic grating G2 are the same but with opposite signs, and the diffraction angles of the diffracted light are the same but in opposite directions.

[0022] As can be seen from the above technical solutions, the present invention provides a cold atom control chip device based on a composite waveguide holographic grating. Compared with the prior art, the present invention has the following advantages: 1. By integrating the functions of multiple cold atom controls onto a chip, the present invention can utilize the composite waveguide holographic grating to achieve functions such as atomic trapping, atomic internal state excitation, and fluorescence detection, solving the problem of the integration compatibility contradiction of multiple cold atom control devices in existing photon-atom chips, and improving the stability and scalability of the device.

[0023] 2. The optical dipole trap of the present invention is composed of crossed vortex light, forming an ellipsoidal tubular structure with an approximately zero light intensity in the central region and completely surrounded by high-intensity light on all sides. When the vortex light is blue-detuned (frequency higher than the atomic resonance frequency), the high-intensity light around the center point will form a repulsive potential barrier, enabling the atoms to be trapped at the light intensity minimum point, avoiding the damage to the atoms caused by the photoinduced heating effect, and prolonging the atomic coherence time.

[0024] It should be understood that the content described in this part is not intended to identify the key or important features of the embodiments of the present invention, nor is it used to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. Of course, any product implementing the present invention does not necessarily need to achieve all the above-mentioned advantages simultaneously. Description of the Drawings

[0025] The specification drawings forming a part of this application are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings: Figure 1 is the schematic diagram of the microstructure of the multi-composite waveguide holographic grating of the present invention; Figure 2Amplitude distribution diagram of the vortex light of the present invention, where: (a) is the amplitude distribution of the vortex light on the x-y plane, (b) is the phase distribution of the vortex light on the x-y plane, (c) is the amplitude distribution of the vortex light on the x-z plane, and (d) is the amplitude distribution of the vortex light on the y-z plane; Figure 3 Numerical simulation diagram of the directional emission of the vortex light of the present invention, where: (a) is the change curve of the linear phase gradient and diffraction efficiency of the 760nm vortex light, (b) is the change curve of the linear phase gradient and diffraction efficiency of the 765nm vortex light, (c) is the change curve of the linear phase gradient and beam diffraction angle of the 760nm vortex light, and (d) is the change curve of the linear phase gradient and beam diffraction angle of the 765nm vortex light; Figure 4 Optical dipole trap distribution diagram of the crossed vortex light of the present invention, where: the white cross pattern represents the trapped cold atoms, (a) is the potential well distribution on the x-y plane, (b) is the potential well distribution on the x-z plane, (c) is the potential well distribution on the y-z plane, and (d) is the relationship distribution between the incident light power and the potential well depth; Figure 5 Optical field distribution and numerical simulation diagram of the Gaussian light of the present invention, where: the white cross pattern represents the trapped cold atoms, (a) is the optical field intensity distribution of the Gaussian light on the x-z plane, (b) is the optical field intensity distribution of the Gaussian light on the y-z plane, (c) is the optical field intensity distribution of the Gaussian light on the x-y plane, (d) is the Gaussian fitting curve of the optical field intensity along the y direction, (e) is the Gaussian fitting curve of the optical field intensity along the x direction, and (f) is the relationship curve between the phase gradient, diffraction angle, and diffraction efficiency; Figure 6 For the present invention Optical field distribution and numerical simulation diagram of the composite Gaussian light incident on the port, where: the white cross pattern represents the trapped cold atoms, (a) is the optical field intensity distribution of the composite Gaussian light on the x-z plane, (b) is the optical field intensity distribution of the composite Gaussian light on the y-z plane, (c) is the optical field intensity distribution of the composite Gaussian light on the x-y plane, and (d) is the relationship curve between the excitation wavelength, the offset of the maximum value of the optical field intensity, and the light intensity distribution; Figure 7 For the present invention Optical field distribution and numerical simulation diagram of the composite Gaussian light incident on the port, where: the white cross pattern represents the trapped cold atoms, (a) is the optical field intensity distribution of the composite Gaussian light on the x-z plane, (b) is the optical field intensity distribution of the composite Gaussian light on the y-z plane, (c) is the optical field intensity distribution of the composite Gaussian light on the x-y plane, and (d) is the comparison curve of the atomic fluorescence collection efficiency. Detailed implementation mode

[0026] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0027] In the embodiments, please refer in detail to Figures 1 to 7 .

[0028] As Figure 1 shown, the cold atom control chip device based on the composite waveguide holographic grating proposed in the embodiment of the present invention realizes the functions of on-chip cold atom capture, internal state excitation and detection through the composite waveguide holographic grating. The device is composed of silicon nitride waveguides placed on a silica substrate. There are two parallel waveguides in the y direction and one waveguide in the x direction. A composite waveguide holographic grating is etched in their cross region, which are respectively marked as composite waveguide holographic grating G1 and composite waveguide holographic grating G2. The left side of the waveguide in the x direction is the waveguide port , and the right side is the waveguide port . The two waveguide ports in the y direction are respectively marked as and .

[0029] The blue-detuned TE0 modes input from the waveguide ports and in the y direction are diffracted by the composite waveguide holographic gratings G1 and G2 respectively to generate two beams of vortex light. These two beams of vortex light intersect at the focus above the center of the chip to form an optical dipole trap, realizing the trapping of cold atoms.

[0030] The TE0 mode input from the waveguide port in the x direction is diffracted by the holographic grating G1 into Gaussian light. By adjusting the emission direction of the Gaussian light, it is focused and aligned with the center of the optical dipole trap, and can act on the trapped cold atoms.

[0031] According to the principle of reversibility of the optical path, the holographic grating G2 can collect atomic fluorescence and convert it into a waveguide mode, and output it to the detector through the port to realize the collection and detection of atomic fluorescence signals.

[0032] The composite waveguide holographic grating fringes are formed by superimposing the interference patterns of the target light and the reference light. Interference pattern one is formed by the interference of the vortex light perpendicular to the waveguide surface and the TE0 mode parallel to the waveguide in the y direction. Interference pattern two is formed by the interference of the Gaussian light perpendicular to the waveguide surface and the TE0 mode parallel to the waveguide in the x direction. These two interference patterns are superimposed to form the composite waveguide holographic grating fringes.

[0033] To control the emission direction of the diffracted light, a linear phase gradient is introduced on the basis of the interference phase in the waveguide holographic grating to form a synthetic phase. By changing the topological charge number and the phase gradient, the orbital angular momentum and the emission direction of the diffracted light can be precisely controlled, realizing the directional and independent control of the vortex light and the Gaussian light.

[0034] For the functions of cold atom excitation and atomic fluorescence collection, the device can be operated in reverse, that is, the TE0 mode can be input from the waveguide port and diffracted into Gaussian light by the holographic grating G2, and focused and aligned with the center of the optical dipole trap to act on the trapped cold atoms. The holographic grating G1 collects the atomic fluorescence and converts it into a waveguide mode and outputs it to the detector through the port to realize the function of atomic fluorescence collection.

[0035] In a specific implementation process, the holographic grating is etched based on a silicon nitride waveguide. The height of the silicon nitride waveguide is 300 nm, the etching depth of the grating is 200 nm, the length and width of the grating are 3 μm, and the grating gap is 1 μm.

[0036] In a specific implementation process, the wavelengths of the vortex light are 760 nm and 765 nm respectively, and the wavelength of the Gaussian light is 780 nm.

[0037] In a specific implementation process, the topological charge numbers of the 760 nm and 765 nm vortex lights are both +1.

[0038] In a specific implementation process, in the holographic grating pattern R1 of the composite waveguide holographic grating, an additional linear phase gradient in the x direction is introduced to the vortex light as the target light , and by changing the phase gradient the emission direction of the vortex light is controlled. The synthetic phase distribution is expressed as:

[0039]

[0040]

[0041] Among them, is the imaginary unit, is the order of the orbital angular momentum, which is used to determine the helical phase structure of the vortex light, is the azimuth angle, The additional phase gradient introduced in the x direction is used to regulate the diffraction angle of the vortex light. is the effective wave vector of the waveguide mode propagating in the y direction. is the effective refractive index of the waveguide mode. is the excitation wavelength. is the vector of the light beam propagation path. and respectively represent the unit vectors in the z direction and the y direction. is the focusing height, that is, the height of the light beam focus relative to the grating plane.

[0042] According to a specific embodiment of the present invention, in the holographic grating pattern R2 of the composite waveguide holographic grating, an additional phase gradient in the x direction is introduced to the Gaussian light as the target light. , changing the phase gradient realizes the regulation of the emission direction of the Gaussian light, and the synthesized phase distribution is expressed as:

[0043]

[0044]

[0045] Among them, is the imaginary unit. is the effective wave vector of the waveguide mode propagating in the x direction. is the additional phase gradient introduced in the x direction for regulating the diffraction angle of the Gaussian light. is the coordinate of the center position of the grating pattern in the x direction. is the effective refractive index of the waveguide mode. is the excitation wavelength. is the vector of the light beam propagation path. and respectively represent the unit vectors in the z direction and the y direction. is the focusing height, that is, the height of the light beam focus relative to the grating plane.

[0046] In a specific embodiment, the following result explanations exist in the actual use process of the method of the present application: (1) Explanation of the light field distribution of the vortex light and the formation of the optical dipole trap by the crossed vortex light Figure 2 (a) and (b) in are respectively the amplitude and phase distributions of the vortex beam diffracted by the grating G1 at the imaging plane. According to Figure 2 , the amplitude shows an annular distribution with a near-zero center, and the phase shows circumferential variation and the existence of a central phase singularity. When the phase gradient When the diffraction beam is inclined in the x-z plane, the angle with the normal of the chip surface is , as shown in Figure 2 (c) in Figure 2 (d) in is the amplitude distribution in the y-z plane. By selecting a 6×6 area for calculation at the plane, the diffraction efficiency of grating G1 is Figure 3 The amplitude and phase distributions of the vortex beam generated by G2 are similar to those of G1 and will not be elaborated here. Figure 3 (a), (b), and (c) in are the potential well distributions of the optical dipole trap formed by the crossed vortex light at the focus in the x-y plane, x-z plane, and y-z plane respectively. The 760nm and 765nm vortex lights are diffracted to the upper focus of the chip (x = 0um, y = 0um, z = 5um) with opposite diffraction angles = 21.8 . The incident power Pb of the vortex lights (760nm and 765nm) forming the potential well is 20mw, and the potential well depth is 0.087mk. Figure 3 (d) in Figure 3 is the result graph of the relationship between the incident light power Pb and the potential well depth. The incident light power and the potential well depth show a linear variation relationship. As the incident light power increases, the potential well depth of the dipole trap also increases.

[0047] The diffraction angles of the vortex beams generated by G1 and G2 can be regulated by the phase gradient . Figure 4 (a) and (b) in Figure 4 show the variation relationships of the diffraction angles of G1 and G2 with the phase gradient respectively. As the phase gradient increases, the diffraction angle decreases linearly. When varies from to , the diffraction angle of the 760nm vortex light varies from about 25.4° to -24°, while the diffraction angle of the 765nm vortex light varies from 26° to -25°. Figure 4 (c) and (d) in Figure 4 give the relationships between the diffraction efficiency and the phase gradient respectively: When varies within the same range, the diffraction efficiency of the 760nm vortex light fluctuates between 13.1% - 14.2%, and the diffraction efficiency of the 765nm vortex light fluctuates between 13.1% - 13.8%. This small efficiency fluctuation is mainly due to the simulation error.

[0048] (2) Explanation of the Gaussian light field intensity distribution and the result of the holographic grating's directional regulation of the Gaussian light emission direction In addition to the diffraction of the incident TE0 mode in the y direction by the holographic grating to generate a vortex beam, the incident TE0 mode in the x direction can excite the grating G1 to generate a Gaussian beam. When the 780 nm wavelength TE0 mode is incident in the x direction from the port, the phase gradient in the second interference pattern of G1 , generates a diffracted Gaussian beam with a diffraction angle in the x-z plane, as shown in (a) of Figure 5 . This diffracted Gaussian beam can reach point f and interact with the trapped atoms in the optical trap formed by the vortex beam, and its diffraction efficiency is about 13.3%. Figure 5 (b) and (c) in Figure 5 are used to show the light intensity distributions at the y-z plane (x = 0 um) and the x-y plane (z = 5 um). As shown in (c) of Figure 5 , the light intensity distributions (dashed lines) along the y and x directions are fitted with a Gaussian function (solid lines), as shown in (d) and (e) of Figure 5 , and the fitting is good, verifying the Gaussian characteristics of the beam.

[0049] According to the condition that the synthesized phase distribution of the holographic grating pattern R2 is satisfied, by changing the phase gradient in the second interference pattern of the grating, the diffraction angle of the Gaussian light can be regulated. The simulation results are shown in (f) of Figure 5 . As shown by the square curve, when the phase gradient increases from to , the diffraction angle linearly changes from 24° to -25°. At the same time, the circular curve in (f) of Figure 5 shows that the diffraction efficiency fluctuates in the range of 11% - 15.1% within the phase gradient range from to .

[0050] (3) The light field intensity distribution of the composite Gaussian light (incident from the port) and the numerical simulation results show that Figure 6 (a)-(c) in show the light intensity distributions after the superposition of G1 and G2 in the x-z, y-z, and x-y planes when the 780 nm TE0 mode is incident in the x direction from the port. Compared with the case where only G1 acts alone in Figure 5 , since G1 and G2 are etched on the same waveguide, part of the TE mode incident in the x direction is diffracted by G1, and the remaining light field continues to propagate to G2 and is diffracted again. The diffracted beam of G2 also reaches point f and interferes with the diffracted light field of G1, and the interference effect significantly affects the characteristics of the light field distribution. The intensity distribution of the diffracted Gaussian beam of G1 is also related to the excitation wavelength. Based on Figure 6 (d), the offset of the maximum value of the light field relative to point f is shown using a square curve.As for the variation relationship with the excitation wavelength, when the wavelength increases from 750 nm to 810 nm, it linearly shifts from 0.34 to -0.34. Based on Figure 6 (d) in a circular curve is used to show that the light intensity at point f

[0051] increases first and then decreases with the wavelength, and reaches the peak at 790 nm. Although the G2 diffracted beam will introduce interference, the diffracted Gaussian beam generated by G1 can still effectively interact with the trapped atoms at the optical trap at point f. The results of the light intensity distribution of the composite Gaussian optical field ( incident from the port) and the fluorescence collection efficiency show that to collect the fluorescence of the trapped atoms, the interference pattern design of grating G2 is similar to that of G1, but with a reverse phase gradient. When Figure 7 in (a)-(c) of shows the light intensity distribution after the superposition of G1 and G2 in the x-z, y-z, and x-y planes when the TE0 mode is incident in the reverse x direction at 780 nm ( Figure 7 incident from the port). (d) in is used to show the influence of the dipole polarization direction on the atomic fluorescence collection efficiency. A dipole is placed at the focus to simulate the atomic fluorescence emission. is the angle between the projection of the dipole polarization direction in the x-y plane and the x-axis, and

[0052] is the angle between the dipole light source polarization direction and the z-axis. When = 90°, = 90°, the atomic fluorescence collection efficiency is about 1.03%.

[0052] In the above embodiments, it can be implemented in whole or in part by software, hardware, firmware, or any combination thereof.

[0053] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

[0054] In addition, it should be noted that if there are directional indications (such as up, down, left, right, front, back...) involved in the embodiments of the present invention, the directional indications are only used to explain the relative positional relationship and movement conditions between components in a specific posture. If the specific posture changes, the directional indications will also change accordingly.

[0055] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In addition, the meaning of "and / or" appearing throughout the text includes three parallel scenarios. Taking "A and / or B" as an example, it includes scenario A, or scenario B, or the scenario where both A and B are satisfied simultaneously. In addition, in the embodiments of the present invention, "a plurality of" means two or more. In addition, the technical solutions between various embodiments can be combined with each other, but it must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

Claims

1. A cold atom control chip device based on a composite waveguide holographic grating, characterized in that It is composed of silicon nitride waveguides placed on a silica substrate. The silicon nitride waveguides include a group of waveguides in the x direction and two groups of waveguides in the y direction. Composite waveguide holographic gratings G1 and composite waveguide holographic gratings G2 are respectively etched in the cross - regions of the waveguides; The ports of the waveguides in the y direction diffract two beams of vortex light by the composite waveguide holographic gratings G1 and the composite waveguide holographic gratings G2, which are used to intersect above the chip to form an optical dipole trap for confining cold atoms; The x-direction waveguide passes through the port Gaussian light is generated by diffraction of the composite waveguide holographic grating G1 and focused and aligned with the center of the optical dipole trap.

2. The cold atom control chip device based on a composite waveguide holographic grating according to claim 1, characterized in that The waveguide in the y direction passes through the port and The input blue-detuned TE0 mode is diffracted by the composite waveguide holographic grating G1 and the composite waveguide holographic grating G2 to generate two beams of vortex light.

3. The cold atom control chip device based on a composite waveguide holographic grating according to claim 1, characterized in that, The x-direction waveguide passes through the port The input TE0 mode is diffracted by the composite waveguide holographic grating G1 to generate Gaussian light. The composite waveguide holographic grating G2 is used to collect atomic fluorescence and convert it into a waveguide mode, and passes through the port Output to the detector to realize the collection and detection of atomic fluorescence signals.

4. The cold atom control chip device based on a composite waveguide holographic grating according to claim 1, characterized in that, The gap distances between the composite waveguide holographic gratings G1 and the composite waveguide holographic gratings G2 are both set within the range of 1μm ± 0.2μm.

5. The cold atom control chip device based on a composite waveguide holographic grating according to claim 1, characterized in that, Both the composite waveguide holographic gratings G1 and the composite waveguide holographic gratings G2 are formed by the superposition of a holographic grating pattern R1 and a holographic grating pattern R2, where: The holographic grating pattern R1 is formed by the interference of the TE0 mode of the waveguide in the y direction as the reference light and the vortex light perpendicular to the waveguide surface as the target light; The holographic grating pattern R2 is formed by the interference of the TE0 mode of the waveguide in the x direction as the reference light and the Gaussian light perpendicular to the waveguide surface as the target light.

6. The cold atom control chip device based on a composite waveguide holographic grating according to claim 5, wherein In the holographic grating pattern R1, an additional phase gradient in the x direction is introduced by the vortex light , and by changing the phase gradient , the directional emission of the diffracted vortex light in the x direction is achieved; The synthetic phase distribution of the holographic grating pattern R1 satisfies the following conditions: wherein, is the imaginary unit, is the order of the orbital angular momentum, which is used to determine the helical phase structure of the vortex light, is the azimuth angle, is the additional phase gradient introduced in the x direction, which is used to control the diffraction angle of the vortex light, is the effective wave vector of the waveguide mode propagating in the y direction, is the effective refractive index of the waveguide mode, is the excitation wavelength, is the vector of the beam propagation path, and respectively represent the unit vectors in the z direction and the y direction, is the focusing height, that is, the height of the beam focus relative to the grating plane, is the phase distribution of the vortex light.

7. The cold atom control chip device based on a composite waveguide holographic grating according to claim 6, characterized in that, The phase gradients of the holographic grating patterns R1 of the composite waveguide holographic grating G1 and the composite waveguide holographic grating G2 have the same value but opposite signs, the diffraction angles of the diffracted vortex light are the same in magnitude but opposite in direction, and the two sets of diffracted vortex light converge above the center of the chip to form an optical dipole trap for confining cold atoms.

8. The cold atom control chip device based on a composite waveguide holographic grating according to claim 5, characterized in that The additional phase gradient of the Gaussian light introduced in the x direction in the holographic grating pattern R2 , by changing the phase gradient , realizes the directional emission of the Gaussian light in the x direction; The synthetic phase distribution of the holographic grating pattern R2 satisfies the following conditions: Among them, is the imaginary unit, is the effective wave vector of the waveguide mode propagating in the x direction, is the additional phase gradient introduced in the x direction for regulating the diffraction angle of the Gaussian light, is the coordinate of the center position of the grating pattern in the x direction, is the effective refractive index of the waveguide mode, is the excitation wavelength, is the vector of the light beam propagation path, and respectively represent the unit vectors in the z direction and the y direction, is the focusing height, that is, the height of the light beam focus relative to the grating plane, is the Gaussian light phase distribution.

9. The cold atom control chip device based on a composite waveguide holographic grating according to claim 8, wherein The linear phase gradients of the holographic patterns R2 of the composite waveguide holographic grating G1 and the composite waveguide holographic grating G2 have the same value but opposite signs, and the diffraction angles of the diffracted light are the same in magnitude but opposite in direction.

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