Apparatus and method for preparing two-dimensional ultracold atomic gas

Abstract

The application discloses a two-dimensional ultracold atomic gas preparation device, comprising: a main light path; an optical potential well forming assembly which generates an optical potential well in the preparation cavity; a light intensity detection light path which measures the light intensity of laser passing through the second mirror; a feedback system which receives the light intensity signal measured by the light intensity detection light path, the feedback system is preset with a light intensity value, and the feedback system adjusts the driving amplitude of the acousto-optic deflector so that the light intensity signal is close to the light intensity value. The application also discloses a two-dimensional ultracold atomic gas preparation method. The two-dimensional ultracold atomic gas preparation device and the preparation method can adjust the driving amplitude of the acousto-optic deflector through the feedback system to stabilize the power of laser, avoid the jump of the light intensity to reduce the number of ultracold atoms, and ensure that the ultracold atomic gas is loaded in a one-dimensional optical lattice in a single layer. The application can be applied to the field of ultracold atomic gas preparation.

Description

Technical Field

[0001] The present invention relates to the field of ultracold atomic gas preparation, and in particular to a two-dimensional ultracold atomic gas preparation device and preparation method. Background Art

[0002] Typically, Bose-Einstein condensates obtained by evaporation in a crossed dipole light trap are three-dimensional ellipsoids with pronounced anisotropy and a highly uneven internal distribution. To achieve a uniformly distributed two-dimensional Bose-Einstein condensate, various techniques have been employed to prepare it. Currently, using a one-dimensional optical lattice with a variable period, all atoms can be loaded into the dark stripes of the optical lattice. The cold atoms can then be adiabatically compressed into a smaller spatial scale, creating a quasi-two-dimensional ultracold atomic gas. However, any jitter in the dark stripes of the optical lattice can severely impact the lifetime and quantity of the ultracold atom load. Summary of the Invention

[0003] The purpose of the present invention is to provide a two-dimensional ultracold atomic gas preparation device and preparation method to solve one or more technical problems existing in the prior art and at least provide a beneficial choice or create conditions.

[0004] The technical solutions adopted to solve the above technical problems are:

[0005] A two-dimensional ultracold atomic gas preparation device, comprising:

[0006] A main optical path includes a first laser, a first half-wave plate, a first spherical lens, a cylindrical lens, an acousto-optic deflector, a first reflector, a second spherical lens, a second reflector, a second half-wave plate, a beam splitter, a third half-wave plate, an aspheric lens, a preparation cavity, a third spherical lens, a third reflector, a fourth spherical lens, an optical pinhole, and a first photodetector, wherein the main optical path forms an intersecting first bound laser and second bound laser in the preparation cavity, and the first photodetector measures the phase of the laser passing through the optical pinhole;

[0007] an optical potential well forming component, which generates an optical potential well in the preparation cavity;

[0008] a light intensity detection optical path for measuring the light intensity of the laser light passing through the second reflector;

[0009] A feedback system receives the light intensity signal measured by the light intensity detection optical path, the feedback system is preset with a light intensity value, and the feedback system adjusts the driving amplitude of the acousto-optic deflector to make the light intensity signal close to the light intensity value.

[0010] The beneficial effects of the present invention are as follows: after the laser is emitted by the first laser, the main optical path forms an intersecting first bound laser and a second bound laser in the preparation cavity, and the first bound laser and the second bound laser interfere to form a one-dimensional optical lattice. The optical potential well forming component generates an optical potential well in the preparation cavity, and the optical potential well cooperates with the one-dimensional optical lattice to load the ultracold atomic cloud in the preparation cavity into the one-dimensional optical lattice; the light intensity detection optical path measures the light intensity of the laser passing through the second reflector. The light intensity of the laser changes rapidly, so the driving amplitude of the acousto-optic deflector is adjusted through the feedback system to stabilize the power of the laser, so that the light intensity of the laser is close to the light intensity value preset by the feedback system, avoiding a large jump in the light intensity causing a decrease in the number of ultracold atoms Low; after the first bound laser and the second bound laser pass through the preparation cavity, they are re-converged into the optical pinhole by the third spherical lens and the fourth spherical lens. The first bound laser and the second bound laser interfere to form dark stripes. The optical pinhole can effectively select a single dark stripe, so that the phase of the laser passing through the optical pinhole can be measured by the first photodetector. The phase shift of the beam splitter is adjusted according to the measured phase, which can effectively suppress the phase drift caused by temperature and mechanical vibration, thereby reducing the jitter of the dark stripes formed after the interference of the first bound laser and the second bound laser, ensuring that the ultracold atomic gas is loaded in a monolayer in the one-dimensional optical lattice, and effectively suppressing the preparation of non-monolayer quasi-two-dimensional ultracold atomic gas.

[0011] As a further improvement of the above technical solution, the feedback system receives the phase signal measured by the first photodetector, the feedback system is preset with a phase value, and the feedback system adjusts the phase shift of the beam splitter so that the phase signal is close to the phase value.

[0012] The feedback system adjusts the phase shift of the beam splitter according to the phase signal, so that the phase of the first bound laser and the second bound laser can be adjusted to a preset phase value, thereby reducing the dark fringe jitter formed by the interference of the first bound laser and the second bound laser.

[0013] As a further improvement of the above technical solution, the light intensity detection optical path includes a fifth spherical lens and a second photodetector arranged in sequence. The light intensity detection optical path is arranged after the second reflector. The second photodetector measures the light intensity of the laser, and the second photodetector sends the measured light intensity signal to the feedback system.

[0014] Since the laser light passing through the second reflector is relatively weak, it is focused onto the second photodetector through the fifth spherical lens, which helps the second photodetector to accurately measure the light intensity of the laser light passing through the second reflector.

[0015] As a further improvement of the above technical solution, the optical potential well is a dipole potential well or a box potential well.

[0016] Both the dipole potential well and the box potential well can produce bound traps in the horizontal direction to confine ultracold atomic clouds. Quasi-two-dimensional ultracold atomic gases require very flat confinement, so the box potential well is easier to produce uniform quasi-two-dimensional ultracold atomic gases than the single-beam dipole potential well.

[0017] A method for preparing a two-dimensional ultracold atomic gas comprises the above-mentioned two-dimensional ultracold atomic gas preparation device, and further comprises the following steps:

[0018] preparing an ultracold atomic cloud in the preparation cavity;

[0019] respectively moving the first confining laser and the second confining laser to the ultracold atomic cloud;

[0020] gradually increasing the light intensity of the laser emitted by the first laser;

[0021] adjusting the phase shift of the beam splitter so that a dark fringe formed by the interference of the first confining laser and the second confining laser is located at the center of the ultracold atomic cloud, and the first confining laser and the second confining laser interfere to form a one-dimensional optical lattice;

[0022] Starting the optical potential well forming component and changing the driving frequency of the acousto-optic deflector, the ultracold atomic cloud is loaded into the one-dimensional optical lattice;

[0023] The driving frequency of the acousto-optic deflector is adjusted to compress the size of the ultracold atomic cloud.

[0024] After the ultracold atomic cloud is prepared, the first and second binding lasers of the main optical path interfere with each other in the preparation cavity to form a one-dimensional optical lattice. The dark stripes of the one-dimensional optical lattice are moved to the center of the ultracold atomic cloud to ensure that the dark stripes can load the ultracold atoms. The optical potential well forming component is started to load the ultracold atomic cloud into the one-dimensional optical lattice. Finally, the driving frequency of the acousto-optic deflector is adjusted to change the phase of the first and second binding lasers, thereby compressing the size of the one-dimensional optical lattice and the size of the ultracold atomic cloud. The driving amplitude of the acousto-optic deflector is adjusted through the feedback system to stabilize the power of the laser and avoid large jumps in light intensity that reduce the number of ultracold atoms. The first binding laser After the light and the second bound laser pass through the preparation cavity, they are re-converged into the optical pinhole by the third spherical lens and the fourth spherical lens. The first bound laser and the second bound laser interfere to form dark stripes. The optical pinhole can effectively select a single dark stripe so that the phase of the laser passing through the optical pinhole can be measured by the first photodetector. The phase shift of the beam splitter is adjusted according to the measured phase, which can effectively suppress the phase drift caused by temperature and mechanical vibration, thereby reducing the jitter of the dark stripes formed after the interference of the first bound laser and the second bound laser, ensuring that the ultracold atomic gas is loaded as a monolayer in the one-dimensional optical lattice, and effectively suppressing the preparation of non-monolayer quasi-two-dimensional ultracold atomic gas.

[0025] As a further improvement of the above technical solution, the beam splitter includes a fourth reflector, a polarization beam splitter prism, a quarter-wave plate, a fifth reflector, and a sixth reflector. The laser in the main light path is divided into the first bound laser and the second bound laser after passing through the fourth reflector and the polarization beam splitter prism. The first bound laser is reflected by the sixth reflector to the third half-wave plate, and the second bound laser passes through the quarter-wave plate and the fifth reflector and then passes through the polarization beam splitter prism to be incident on the third half-wave plate.

[0026] Changing the position of the sixth reflector changes the transmission angle of the first bound laser accordingly, and changing the position of the fifth reflector changes the transmission angle of the second bound laser accordingly, so that the transmission angles of the first bound laser and the second bound laser can be adjusted separately to change the position of the dark stripes formed by the interference of the first bound laser and the second bound laser.

[0027] As a further improvement of the above technical solution, the step of moving the first confining laser and the second confining laser to the ultracold atomic cloud in the preparation chamber comprises the following steps:

[0028] shielding the second confining laser and adjusting the position of the sixth reflector so that the first confining laser is aimed at the ultracold atomic cloud;

[0029] changing the driving frequency of the acousto-optic deflector and adjusting the distance between the aspheric lens and the preparation cavity until the first confined laser continues to irradiate the ultracold atomic cloud;

[0030] The first confining laser is shielded, and the position of the fifth reflecting mirror is adjusted so that the second confining laser is aligned with the center of the ultracold atomic cloud.

[0031] First, the second bound laser is blocked, and the position of the sixth reflector is changed to move the first bound laser to the center of the ultracold atomic cloud. After changing the driving frequency of the acousto-optic deflector to change the angle of the first bound laser, it will cause the first bound laser to deviate from the ultracold atomic cloud. Therefore, it is necessary to adjust the aspheric lens to move the first bound laser back to the ultracold atomic cloud, so that the first bound laser always remains in the ultracold atomic cloud within all driving frequency ranges of the acousto-optic deflector; the first bound laser is blocked, and the position of the fifth reflector is adjusted to align the second bound laser with the center of the ultracold atomic cloud, so that the first and second bound lasers are respectively moved to the center of the ultracold atomic cloud, ensuring that the one-dimensional optical lattice formed after the interference of the first and second bound lasers accurately corresponds to the position of the ultracold atomic cloud.

[0032] As a further improvement of the above technical solution, the beam splitter further comprises a moving mechanism connected to the fifth mirror, and the moving mechanism is electrically connected to the feedback system, and the adjusting the angle of the second beam laser comprises the following steps:

[0033] The first photodetector sends the measured phase signal to the feedback system.

[0034] The feedback system is preset with a phase value, and the feedback system drives the moving mechanism to drive the fifth mirror to make the phase signal close to the phase value.

[0035] Since the phases of the first beam laser and the second beam laser slowly drift with the mechanical vibration of the device and the temperature rise of the device, the feedback system receives the phase signal measured by the first photodetector, and if the phase of the laser changes, the feedback system adjusts the position of the fifth mirror to change the transmission angle of the second beam laser, thereby changing the position of the dark stripes generated after the first beam laser and the second beam laser interfere, to reduce the dark stripe jitter of the one-dimensional optical lattice in the preparation cavity.

[0036] As a further improvement of the above technical solution, in the step of gradually increasing the light intensity of the laser emitted by the first laser, the feedback system adjusts the driving amplitude of the acousto-optic deflector to stabilize the laser power.

[0037] When increasing the light intensity of the laser emitted by the first laser, the preset light intensity value of the feedback system also changes, so as to stabilize the laser power during the adjustment of the laser intensity and avoid the light intensity of the laser jumping sharply after the adjustment of the light intensity.

[0038] As a further improvement of the above technical solution, during the preparation of the super-cooled atomic cloud in the preparation cavity, the super-cooled atomic cloud is bound by the crossed dipole optical trap; after the optical potential well forming assembly is started, the binding light intensity of the crossed dipole optical trap starts to decrease; and during the process of changing the driving frequency of the acousto-optic deflector, the binding light intensity of the crossed dipole optical trap gradually decreases to zero.

[0039] The super-cooled atomic cloud is bound by the crossed dipole optical trap, and then after the optical potential well forming assembly is started, the binding light intensity of the crossed dipole optical trap can be gradually decreased, so that the super-cooled atoms gradually transfer to the one-dimensional optical lattice, until the binding light intensity of the crossed dipole optical trap is reduced to zero during the process of changing the driving frequency of the acousto-optic deflector, so that all the super-cooled atoms are transferred to the one-dimensional optical lattice. The gradual decrease of the binding light intensity of the crossed dipole optical trap helps the super-cooled atoms to be transferred to the one-dimensional optical lattice in a bound state, so as to reduce the loss of super-cooled atoms. BRIEF DESCRIPTION OF DRAWINGS

[0040] The present invention will be further described below with reference to the accompanying drawings and embodiments;

[0041] Figure 1 This is a schematic structural diagram of the first part of an embodiment of the two-dimensional ultracold atomic gas preparation device provided by the present invention;

[0042] Figure 2 This is a schematic structural diagram of the second part of one embodiment of the two-dimensional ultracold atomic gas preparation device provided by the present invention;

[0043] Figure 3 This is a flow chart of the steps of one embodiment of the method for preparing two-dimensional ultracold atomic gas provided by the present invention.

[0044] 10. Laser, 11. First bound laser, 12. Second bound laser, 110. First laser, 120. First half-wave plate, 130. First spherical lens, 140. Cylindrical lens, 150. Acousto-optic deflector, 160. First reflector, 170. Second spherical lens, 180. Second reflector, 190. Second half-wave plate, 200. Beam splitter, 201. Fourth reflector, 202. Polarization beam splitter, 203. Quarter-wave plate, 204. Fifth reflector, 205. Sixth reflecting mirror, 206. Moving mechanism, 210. Third half-wave plate, 220. Aspheric lens, 230. Preparation cavity, 240. Third spherical lens, 250. Third reflecting mirror, 260. Fourth spherical lens, 270. Optical pinhole, 280. First photodetector, 300. Optical potential well forming component, 301. Second laser, 302. Sixth spherical lens, 400. Light intensity detection optical path, 401. Fifth spherical lens, 402. Second photodetector. DETAILED DESCRIPTION

[0045] This section will describe in detail the specific embodiments of the present invention. The preferred embodiments of the present invention are shown in the accompanying drawings. The purpose of the accompanying drawings is to supplement the description of the text part of the specification with graphics, so that people can intuitively and vividly understand each technical feature and the overall technical solution of the present invention, but it should not be understood as a limitation on the scope of protection of the present invention.

[0046] In the description of the present invention, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on the present invention.

[0047] In the description of the present invention, if there are words such as "several", it means one or more, and "more" means more than two. Greater than, less than, and exceed are understood as not including the number itself, and above, below, and within are understood as including the number itself.

[0048] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, and connecting should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0049] Reference Figures 1 to 2 As shown, the two-dimensional ultracold atomic gas preparation device of the present invention makes the following embodiments:

[0050] The two-dimensional ultracold atomic gas preparation device includes a main optical path, an optical potential well forming component 300, and a light intensity detection optical path 400.

[0051] The main optical route consists of a first part and a second part. The first part is arranged on a horizontal plane, and the second part is arranged on a vertical plane.

[0052] Reference Figure 1 As shown, the first part is composed of a first laser 110, a first half-wave plate 120, a first spherical lens 130, a cylindrical lens 140, an acousto-optic deflector 150, a first reflector 160, a second spherical lens 170, a second reflector 180, a second half-wave plate 190, and a fourth reflector 201 of a beam splitter 200, which are arranged in sequence.

[0053] The light intensity detection optical path 400 is disposed on the first portion. The light intensity detection optical path 400 is composed of a fifth spherical lens 401 and a second photodetector 402 . The fifth spherical lens 401 and the second photodetector 402 are sequentially disposed behind the second reflector 180 .

[0054] Reference Figure 2 As shown, the second part consists of a beam splitter 200, a third half-wave plate 210, an aspheric lens 220, a preparation cavity 230, a third spherical lens 240, a third reflector 250, a fourth spherical lens 260, an optical pinhole 270, and a first photodetector 280, which are arranged in sequence.

[0055] The optical potential well forming component 300 is disposed on the second portion and includes a second laser 301 and a sixth spherical lens 302 . The laser light emitted by the second laser 301 passes through the sixth spherical lens 302 and is incident into the preparation chamber 230 .

[0056] A half-wave plate is a birefringent crystal of a certain thickness. When normally incident light passes through it, the phase difference between the ordinary light and the extraordinary light is equal to π or an odd multiple thereof. Such a crystal is called a half-wave plate, or simply a half-wave plate.

[0057] A spherical lens is a lens with a spherical refractive surface or one spherical surface and a flat surface. A spherical lens can be considered an infinite number of prisms. The degree of refraction of light changes gradually and evenly from the main axis to the edge, resulting in uniform convergence and divergence of light and the ability to form an image. The degree of convergence and divergence of light by a spherical lens depends primarily on the refractive index of the lens glass and the radius of curvature of the two refractive surfaces.

[0058] Cylindrical lens 140 is a cylindrical lens with a cross-section consisting of two circular arcs or a straight line. It can be biconvex, biconcave, plano-convex, plano-concave, or meniscus. Cylindrical lenses have a focal line parallel to the cylindrical surface. The distance between the focal line and the cylindrical surface depends on the radius of curvature of the lens surface and the refractive index of the glass.

[0059] The acousto-optic deflector 150 is a device based on the deflection principle. When mechanical waves are generated in a medium such as transparent glass or crystal, they cause periodic changes in the refractive index, forming a phase-type diffraction grating. When a laser beam is incident on this medium, it diffracts, and the intensity and direction of the diffracted light vary depending on the intensity and wavelength of the mechanical wave. This is the interaction between mechanical waves and light. This effect is the operating principle of modulators and deflectors. The acousto-optic deflector 150 can change the angle of the laser light based on this interaction mechanism.

[0060] Photodetectors work by converting light into electrical signals, based on the principle that radiation causes a change in the conductivity of the material being illuminated. They can be used to measure parameters such as laser intensity, wavelength, and phase.

[0061] Reference Figure 1 As shown, in this embodiment, the first laser 110 is a 532 nm laser, and the laser light 10 emitted by the first laser 110 passes through the first half-wave plate 120, the first spherical lens 130, the cylindrical lens 140, and the acousto-optic deflector 150 in sequence.

[0062] The first half-wave plate 120 can maximize the diffraction efficiency of the acousto-optic deflector 150 . The laser light 10 is collimated and parallelized by the first spherical lens 130 , and then passes through the cylindrical lens 140 and enters the acousto-optic deflector 150 .

[0063] By changing the driving frequency of the acousto-optic deflector 150, the -1 order diffraction light output by the acousto-optic deflector 150 is made parallel to the optical axis, and the +1 order diffraction light output by the acousto-optic deflector 150 is reflected by the first reflector 160 to the second spherical lens 170. The laser light 10 collimated and parallel by the second spherical lens 170 then passes through the second reflector 180, and the second reflector 180 has a certain light transmittance.

[0064] Among them, a small portion of the laser light 10 passes through the second reflector 180 and is incident on the fifth spherical lens 401. The fifth spherical lens 401 re-collimates this portion of the laser light 10 and focuses it onto the second photodetector 402. The second photodetector 402 measures the light intensity of this portion of the laser light 10 and generates a light intensity signal.

[0065] Most of the laser light 10 is reflected by the second reflector 180 to the second half-wave plate 190 , and then passes through the second half-wave plate 190 and enters the beam splitter 200 .

[0066] Reference Figure 2 As shown, the beam splitter 200 includes a fourth reflecting mirror 201 , a polarization beam splitting prism 202 , a quarter wave plate 203 , a fifth reflecting mirror 204 , a sixth reflecting mirror 205 , and a moving mechanism 206 .

[0067] The beam splitter 200 is an optical device that can split a beam of light into two or more beams of light. It is a key part of most interferometers.

[0068] The polarization beam splitter prism 202 is an optical element for separating the horizontal polarization and the vertical polarization of light.

[0069] The quarter wave plate 203 is a birefringent single crystal wave plate of a certain thickness. When light passes through the wave plate from normal incidence, the phase difference between the ordinary light and the extraordinary light is equal to π / 2 or an odd multiple thereof. Such a chip is called a quarter wave plate or 1 / 4 wave plate.

[0070] The laser light 10 entering the beam splitter 200 is first reflected by the fourth reflector 201 onto a vertical plane, that is, the laser light 10 is transformed from horizontal transmission to vertical transmission. The laser light 10 reflected by the fourth reflector 201 is then incident on the polarization beam splitter prism 202, which splits the laser light 10 into a first bound laser light 11 and a second bound laser light 12.

[0071] The first bound laser light 11 passes through the polarization beam splitting prism 202 and is incident on the sixth reflecting mirror 205 . The transmission direction of the first bound laser light 11 is changed by the sixth reflecting mirror 205 .

[0072] The second bound laser 12 is reflected by the polarization beam splitter prism 202 and then incident on the quarter-wave plate 203. After passing through the quarter-wave plate 203, the second bound laser 12 is incident on the fifth reflector 204. The fifth reflector 204 is perpendicular to the second bound laser 12, so that the second bound laser 12 passes through the quarter-wave plate 203 and the polarization beam splitter prism 202 again.

[0073] The moving mechanism 206 is connected to the fifth reflector 204 and is made of piezoelectric ceramics. The moving mechanism 206 can adjust the position of the fifth reflector 204 relative to the quarter-wave plate 203 and the polarization beam splitter prism 202 .

[0074] The first binding laser 11 and the second binding laser 12 are incident on the third half-wave plate 210 in parallel, and then the first binding laser 11 and the second binding laser 12 are incident on the aspheric lens 220. After being converged by the aspheric lens 220, the first binding laser 11 and the second binding laser 12 are incident on the preparation cavity 230. The preparation cavity 230 is an optical vacuum glass cavity, so as to facilitate the preparation of ultracold atomic gas in the preparation cavity 230.

[0075] Aspheric lens 220 is a lens with an aspheric refractive surface. Generally, it can be divided into two categories: simple curved surfaces (such as paraboloids) and compound curved surfaces. Aspheric lenses, after complex calculations, can be used to correct spherical aberration in lens systems. Because the aspheric surface is properly compounded, the center of the lens can be positive and the edges negative, thus simultaneously performing multiple correction functions and theoretically reducing spherical aberration to zero.

[0076] The first and second binding lasers 11, 12 interfere with each other in the preparation chamber 230. The first and second binding lasers 11, 12 then pass through the preparation chamber 230 and are incident on the third spherical lens 240. The third spherical lens 240 realigns the first and second binding lasers 11, 12 so that they are parallel to each other.

[0077] The third reflecting mirror 250 then changes the transmission direction of the first and second confined laser beams 11 and 12 so that they are incident on the fourth spherical lens 260 . The fourth spherical lens 260 then converges the first and second confined laser beams 11 and 12 into the optical pinhole 270 .

[0078] The first binding laser 11 and the second binding laser 12 interfere in the optical pinhole 270. The optical pinhole 270 selects the single stripe formed after the interference of the first binding laser 11 and the second binding laser 12 to facilitate the phase locking of the laser 10, so that the first photodetector 280 can detect the phase after the interference of the first binding laser 11 and the second binding laser 12 and generate a phase signal.

[0079] The acousto-optic deflector 150 and the cylindrical lens 140 can rotate, and both change the scanning direction and the aspect ratio of the laser beam respectively.

[0080] A feedback system is an automatic control system based on the feedback principle. It controls the system based on information about changes in system output, i.e., by comparing the deviation between system behavior (output) and expected behavior and eliminating the deviation to achieve the expected system performance.

[0081] The feedback system is electrically connected to the first photodetector 280, the second photodetector 402, the moving mechanism 206, and the acousto-optic deflector 150. The first photodetector 280 sends the measured phase signal to the feedback system, and the second photodetector 402 sends the measured light intensity signal to the feedback system.

[0082] The feedback system controls the moving mechanism 206 to drive the fifth reflector 204 to move, so that the fifth reflector 204 moves away from or closer to the quarter-wave plate 203 .

[0083] The feedback system controls the driving amplitude of the acousto-optic deflector 150 , so that the acousto-optic deflector 150 can change the intensity of the +1-order diffracted light, that is, change the light intensity of the laser 10 in the main optical path.

[0084] The feedback system is preset with a light intensity value, which can be set according to user needs. When the feedback system receives a light intensity signal, it compares the light intensity signal with the light intensity value.

[0085] When there is a difference between the light intensity signal and the light intensity value, the feedback system changes the driving amplitude of the acousto-optic deflector 150, causing the light intensity of the laser 10 to change. The light intensity signal measured by the second photodetector 402 changes so that the light intensity signal is close to the light intensity value, thereby stabilizing the power of the laser 10 and avoiding large jumps in the light intensity after the interference of the first binding laser 11 and the second binding laser 12.

[0086] Since the intensity of the laser 10 changes rapidly, a feedback system needs to be used to quickly respond so as to stabilize the power of the laser 10 as quickly as possible and avoid drastic jumps in the intensity of the laser.

[0087] The feedback system has a preset phase value, which can be set according to user needs. When the feedback system receives a phase signal, it compares the phase signal with the phase value.

[0088] When there is a difference between the phase signal and the phase value, the feedback system controls the moving mechanism 206 to change the position of the fifth reflector 204, causing the fifth reflector 204 to move away from or closer to the quarter-wave plate 203, thereby changing the phase of the fringes formed by the interference of the first binding laser 11 and the second binding laser 12, and causing the phase signal measured by the first photodetector 280 to change, so that the phase signal is close to the phase value, so as to facilitate the correction of the phase of the fringes formed by the interference of the first binding laser 11 and the second binding laser 12.

[0089] Since the fringes formed by the interference of the first binding laser 11 and the second binding laser 12 drift slowly due to factors such as device temperature and mechanical vibration, the phase can also be adjusted by manually observing the changes in the phase signal of the first photodetector 280 and manually operating the moving mechanism 206 to change the position of the fifth reflector 204.

[0090] Referring to Figure 2 As shown in the figure, the optical potential well forming assembly 300 is composed of a second laser 301 and a sixth spherical lens 302, the second laser 301 is a 1064nm laser, the laser emitted by the second laser 301 passes through the sixth spherical lens 302, and the laser is incident into the preparation cavity 230 to form a dipole potential well, thereby generating a binding well in the horizontal direction to bind the atoms in the horizontal direction.

[0091] Alternatively, in some embodiments, the optical potential well forming assembly 300 is composed of a 523nm laser and a spatial light modulator or a tapered lens, the laser emitted by the 523nm laser passes through the spatial light modulator or the tapered lens, so that the laser forms a tubular light beam (box light beam) projected into the preparation cavity 230, thereby forming a box potential well in the preparation cavity 230, generating a binding well in the horizontal direction to bind the atoms in the horizontal direction.

[0092] Referring to Figure 3 As shown in the figure, the two-dimensional ultracold atomic gas preparation method of the present application is as follows:

[0093] An ultracold atomic cloud is prepared in the preparation cavity 230 using the crossed dipole optical traps.

[0094] The acousto-optic deflector 150 sets an initial frequency, and the first laser 110 emits laser 10, the acousto-optic deflector 150 deflects the propagation angle of the laser 10, so that the laser 10 is split into first binding laser 11 and second binding laser 12 after passing through the beam splitter 200, and the first binding laser 11 and the second binding laser 12 are incident into the preparation cavity 230 after passing through the third half-wave plate 210 and the aspherical lens 220.

[0095] The second binding laser 12 split by the blocking polarization beam splitter prism 202 is blocked from entering the preparation cavity 230, and the first binding laser 11 is incident into the preparation cavity 230, at this time the first binding laser 11 may be out of alignment with the ultracold atomic cloud, so the position of the sixth mirror 205 is adjusted to align the first binding laser 11 with the center of the ultracold atomic cloud in the evaporation process in the crossed dipole optical trap.

[0096] At this time, according to the principle of horizontal absorption imaging, when the first binding laser 11 is irradiated to the ultracold atomic cloud, the first binding laser 11 will repel the ultracold atoms, so that a hole is formed on the ultracold atomic cloud, and when the position of the sixth mirror 205 is adjusted, the first binding laser 11 changes the transmission angle to change the position of the hole on the ultracold atomic cloud.

[0097] Moving the hole to the center of the ultracold atomic cloud means that the first binding laser 11 is aligned with the center of the ultracold atomic cloud.

[0098] By changing the driving frequency of the AOD 150 , the deflection angle of the laser 10 after passing through the AOD 150 changes, thereby changing the transmission angle of the first confined laser 11 , so that the first confined laser 11 may move outside the ultracold atomic cloud.

[0099] Therefore, by adjusting the positions of the aspheric lens 220 and the preparation cavity 230 , the aspheric lens 220 changes the position where the first confined laser 11 converges to the preparation cavity 230 , so that the first confined laser 11 moves back to the vicinity of the center of the ultracold atomic cloud.

[0100] The above process is repeated until the first confined laser 11 is maintained near the center of the ultracold atomic cloud within the driving frequency range of all the acousto-optic deflectors 150 .

[0101] The first confining laser 11 is blocked and the second confining laser 12 is enabled. The position of the fifth reflecting mirror 204 is adjusted by the moving mechanism 206 to change the transmission angle of the second confining laser 12 so that the second confining laser 12 is aligned with the center of gravity of the ultracold atomic cloud.

[0102] Similarly, the position of the second confining laser 12 relative to the ultracold atom cloud can be determined based on the hole formed by the second confining laser 12 repelling the ultracold atoms.

[0103] After the transmission angles of the first confining laser 11 and the second confining laser 12 are adjusted, the first confining laser 11 and the second confining laser 12 interfere with each other in the preparation cavity 230 to form a one-dimensional optical lattice.

[0104] After the ultracold atomic cloud is prepared, the crossed dipole light trap remains to confine the ultracold atomic cloud.

[0105] The second photodetector 402 measures the intensity of the laser light passing through the second reflector 180, gradually increases the intensity of the laser light emitted by the first laser 110, and adjusts the intensity value set on the feedback system accordingly, so that in the process of gradually increasing the intensity of the laser light emitted by the first laser 110, the intensity value of the feedback system also gradually increases, and the intensity value is used to guide the feedback system to adjust the driving amplitude change of the acousto-optic deflector 150, so that after each increase in the laser light emitted by the first laser 110, the intensity of the laser light passing through the acousto-optic deflector 150 is stabilized as soon as possible, avoiding drastic jumps in the intensity of the laser light deflected by the acousto-optic deflector 150, so as to stabilize the power of the laser 10.

[0106] After passing through the preparation chamber 230, the first and second confining laser beams 11 and 12 sequentially pass through the third spherical lens 240, the third reflector 250, the fourth spherical lens 260, and the optical pinhole 270. The first and second confining laser beams 11 and 12 interfere with each other again in the optical pinhole 270 to form dark fringes. The phase of the fringes formed after the interference is measured by the first photodetector 280. The first photodetector 280 measures the phase signal and sends it to the feedback system. The feedback system compares the phase signal with the phase value. The feedback system then controls the moving mechanism 206 to drive the fifth reflector 204 to move, thereby changing the optical path of the second confining laser beam 12, thereby changing the phase difference between the first and second confining laser beams 11 and 12, and changing the phase of the fringes formed after the interference of the first and second confining laser beams 11 and 12.

[0107] The dark stripes formed by the interference of the first confining laser 11 and the second confining laser 12 are moved to the center or west of the ultracold atomic cloud, and the one-dimensional optical lattice formed by the interference of the first confining laser 11 and the second confining laser 12 corresponds to the position of the ultracold atomic cloud.

[0108] The intensity of the laser light emitted by the first laser 110 is further increased, the optical potential well forming component 300 is started, and then the bound light intensity of the crossed dipole optical trap is gradually reduced.

[0109] The driving frequency of the acousto-optic deflector 150 is slowly changed to gradually reduce the bound light intensity of the crossed dipole light trap to zero, and gradually increase the light intensity of the optical potential well forming component 300, thereby transferring the ultracold atomic cloud from the crossed dipole light trap to the one-dimensional optical lattice.

[0110] Finally, the driving frequency of the acousto-optic deflector 150 is adjusted to change the period of the one-dimensional optical lattice, thereby compressing the size of the ultracold atomic cloud and allowing the ultracold atoms to be loaded into a single-layer two-dimensional optical lattice.

[0111] The above specifically describes the preferred embodiments of the present invention, but the invention is not limited to the embodiments. Those skilled in the art may make various equivalent modifications or substitutions without violating the spirit of the present invention. These equivalent modifications or substitutions are all included in the scope defined by the claims of this application.

Claims

1. A two-dimensional ultracold atomic gas preparation device, characterized by: include: A main optical path includes a first laser, a first half-wave plate, a first spherical lens, a cylindrical lens, an acousto-optic deflector, a first reflector, a second spherical lens, a second reflector, a second half-wave plate, a beam splitter, a third half-wave plate, an aspheric lens, a preparation cavity, a third spherical lens, a third reflector, a fourth spherical lens, an optical pinhole, and a first photodetector, wherein the main optical path forms an intersecting first bound laser and second bound laser in the preparation cavity, and the first photodetector measures the phase of the laser passing through the optical pinhole; an optical potential well forming component, which generates an optical potential well in the preparation cavity; a light intensity detection optical path for measuring the light intensity of the laser light passing through the second reflector; A feedback system receives the light intensity signal measured by the light intensity detection optical path, the feedback system is preset with a light intensity value, and the feedback system adjusts the driving amplitude of the acousto-optic deflector to make the light intensity signal close to the light intensity value.

2. The two-dimensional ultracold atomic gas preparation device according to claim 1, characterized in that: The feedback system receives the phase signal measured by the first photodetector. The feedback system is preset with a phase value. The feedback system adjusts the phase shift of the beam splitter so that the phase signal is close to the phase value.

3. The two-dimensional ultracold atomic gas preparation device according to claim 1, characterized in that: The light intensity detection optical path includes a fifth spherical lens and a second photodetector arranged in sequence. The light intensity detection optical path is arranged after the second reflector. The second photodetector measures the light intensity of the laser, and the second photodetector sends the measured light intensity signal to the feedback system.

4. The two-dimensional ultracold atomic gas preparation device according to claim 1, characterized in that: The optical potential well is a dipole potential well or a box potential well.

5. A method for preparing a two-dimensional ultracold atomic gas, characterized by: The device for preparing a two-dimensional ultracold atomic gas according to any one of claims 1 to 4, wherein the method for preparing a two-dimensional ultracold atomic gas further comprises the following steps: preparing an ultracold atomic cloud in the preparation cavity; respectively moving the first confining laser and the second confining laser to the ultracold atomic cloud; gradually increasing the light intensity of the laser emitted by the first laser; adjusting the phase shift of the beam splitter so that a dark fringe formed by the interference of the first confining laser and the second confining laser is located at the center of the ultracold atomic cloud, and the first confining laser and the second confining laser interfere to form a one-dimensional optical lattice; Starting the optical potential well forming component and changing the driving frequency of the acousto-optic deflector, the ultracold atomic cloud is loaded into the one-dimensional optical lattice; The driving frequency of the acousto-optic deflector is adjusted to compress the size of the ultracold atomic cloud.

6. The method for preparing a two-dimensional ultracold atomic gas according to claim 5, wherein: The beam splitter includes a fourth reflector, a polarization beam splitter prism, a quarter-wave plate, a fifth reflector, and a sixth reflector. The laser in the main light path is divided into the first bound laser and the second bound laser after passing through the fourth reflector and the polarization beam splitter prism. The first bound laser is reflected by the sixth reflector to the third half-wave plate, and the second bound laser passes through the quarter-wave plate and the fifth reflector and then passes through the polarization beam splitter prism to be incident on the third half-wave plate.

7. The method for preparing a two-dimensional ultracold atomic gas according to claim 6, wherein: The step of moving the first confining laser and the second confining laser to the ultracold atomic cloud in the preparation chamber comprises the following steps: shielding the second confining laser and adjusting the position of the sixth reflector so that the first confining laser is aimed at the ultracold atomic cloud; changing the driving frequency of the acousto-optic deflector and adjusting the distance between the aspheric lens and the preparation cavity until the first confined laser continues to irradiate the ultracold atomic cloud; The first confining laser is shielded, and the position of the fifth reflecting mirror is adjusted so that the second confining laser is aligned with the center of the ultracold atomic cloud.

8. The method for preparing a two-dimensional ultracold atomic gas according to claim 6, wherein: The beam splitter further includes a moving mechanism connected to the fifth reflector, and the moving mechanism is electrically connected to the feedback system. Adjusting the angle of the second bound laser includes the following steps: The first photodetector sends the measured phase signal to the feedback system; The feedback system is preset with a phase value, and the feedback system drives the moving mechanism to drive the fifth reflector so that the phase signal approaches the phase value.

9. The method for preparing a two-dimensional ultracold atomic gas according to claim 5, wherein: In the step of gradually increasing the light intensity of the laser light emitted by the first laser, the driving amplitude of the acousto-optic deflector is adjusted by the feedback system to stabilize the laser power.

10. The method for preparing a two-dimensional ultracold atomic gas according to claim 5, wherein: During the process of preparing the ultracold atomic cloud in the preparation cavity, a crossed dipole light trap is used to confine the ultracold atomic cloud; after the optical potential well forming component is started, the confining light intensity of the crossed dipole light trap begins to decrease; during the process of changing the driving frequency of the acousto-optic deflector, the confining light intensity of the crossed dipole light trap gradually decreases to zero.

Images