技术领域technical field
本发明涉及一种将空间激光耦合到空芯光子晶体光纤的耦合调节技术与监测方法。具体为一种用于冷原子导引的空间光激发光子晶体光纤纤芯基模的耦合调节技术与模式及功率监测方法，能够实现较高的激光耦合效率并实时监测光纤输出光场模式。The invention relates to a coupling adjustment technology and a monitoring method for coupling a space laser to a hollow-core photonic crystal fiber. Specifically, it is a coupling adjustment technology and mode and power monitoring method for spatial photonic crystal fiber core fundamental mode guided by cold atoms, which can achieve high laser coupling efficiency and monitor the fiber output light field mode in real time.
背景技术Background technique
原子导引是利用激光对原子的力学作用，使其相当自由地操纵原子的外部运动，将一群原子从一处输运至另一处。现有的操控技术利用复杂的光学元件产生可以用于导引的空间光场，离散的几何部件较多，不利于干涉式原子陀螺向实用化的方向发展。光纤以其损耗小，且在空间可自由弯曲的优点，逐步成为实验上用于导引原子的首要方法。Atom guidance is to use the mechanical effect of laser on atoms, so that it can manipulate the external movement of atoms quite freely, and transport a group of atoms from one place to another. The existing control technology uses complex optical elements to generate a spatial light field that can be used for guidance, and there are many discrete geometric components, which is not conducive to the practical development of the interferometric atomic gyroscope. With the advantages of low loss and free bending in space, optical fiber has gradually become the primary method for guiding atoms in experiments.
原子被空芯光子晶体光纤中的光俘获并且沿光纤中心轴向被导引的过程主要依赖于光纤中的导引激光对原子产生的偶极力作用，而偶极力产生于激光光强的不均匀分布。由于高斯光束光强分布为中间强两边弱，当激光频率高于原子共振频率时，原子趋近于光强强的方向，即在高斯光束的中心形成势阱将原子俘获在高斯光束中心，中心光强越强阱深越大。因此高效的原子导引的前提条件是增大导引激光耦合进光纤纤芯中的耦合效率(激光功率输出输入比值)，且优化光纤芯中的传播模式，使传播模式为基模。The process of atoms being captured by the light in the hollow-core photonic crystal fiber and guided along the central axis of the fiber mainly depends on the dipole force generated by the guiding laser in the fiber on the atoms, and the dipole force is generated by the unevenness of the laser light intensity. distributed. Since the light intensity distribution of the Gaussian beam is strong in the middle and weak on both sides, when the laser frequency is higher than the atomic resonance frequency, the atoms tend to the direction of the light intensity, that is, a potential well is formed at the center of the Gaussian beam to trap atoms in the center of the Gaussian beam, and the center The stronger the light intensity, the larger the well depth. Therefore, the prerequisite for efficient atomic guidance is to increase the coupling efficiency (laser power output-to-input ratio) of the guided laser coupling into the fiber core, and to optimize the propagation mode in the fiber core so that the propagation mode is the fundamental mode.
随着对空芯光子晶体光纤导引原子的研究不断深入，产生了多种将空间激光耦合进光纤的实验方案。一般的光纤耦合方法是直接采用耦合物镜将空间准直激光聚焦在光纤端面上，或将耦合光路中的最后一片聚焦透镜置于真空腔内。这两种方法的共同点是减小了光纤与透镜之间的距离(约10mm)，使耦合光束束腰直径减小，能获得较高的耦合效率。但上述方法不适用于受腔体结构限制，光纤距真空腔玻璃表面距离较远的情况。而将聚焦透镜置于腔内的前提条件是光纤与透镜的位置固定不变，也不适用于本装置中光纤轴向位置可调的实验设计。With the deepening of research on guiding atoms in hollow-core photonic crystal fibers, a variety of experimental schemes for coupling space lasers into optical fibers have emerged. The general fiber coupling method is to directly use the coupling objective lens to focus the spatially collimated laser on the fiber end face, or place the last focusing lens in the coupling optical path in a vacuum cavity. The common point of these two methods is that the distance between the optical fiber and the lens is reduced (about 10mm), so that the beam waist diameter of the coupling beam is reduced, and a higher coupling efficiency can be obtained. However, the above method is not suitable for the situation where the distance between the optical fiber and the glass surface of the vacuum chamber is relatively long due to the limitation of the cavity structure. The prerequisite for placing the focusing lens in the cavity is that the positions of the optical fiber and the lens are fixed, which is not suitable for the experimental design in which the axial position of the optical fiber is adjustable in this device.
另外，传统的耦合方案采用以输入输出功率的比值作为耦合效率的判别依据，忽略了光路偏移或倾斜而使激光耦合进光子晶体光纤包层中、或激发光纤高阶模式的情况。此时尽管激光光功率的耦合效率较高，但会激发多种模式，从而大大降低光对原子的俘获能力。In addition, the traditional coupling scheme uses the ratio of input and output power as the basis for judging the coupling efficiency, ignoring the optical path offset or tilt to couple the laser into the cladding of the photonic crystal fiber or excite the high-order mode of the fiber. At this time, although the coupling efficiency of laser light power is high, it will excite multiple modes, which greatly reduces the ability of light to capture atoms.
发明内容Contents of the invention
本发明的目的是解决上述问题，提出一种用于冷原子导引的空间激光——光纤的耦合调节与模式监测方法。The object of the present invention is to solve the above problems, and propose a method for coupling adjustment and mode monitoring of a cold atom-guided space laser-optical fiber.
空间激光——光纤的耦合调节与模式监测方法，具体为以下两个步骤：Space laser-optical fiber coupling adjustment and mode monitoring method, specifically the following two steps:
步骤一、空间激光——光纤的耦合调节；Step 1. Space laser-optical fiber coupling adjustment;
本实验中由于腔体结构的限制，聚焦透镜与光纤输入端相距较远，且陶瓷头直径较小，所用激光波长为不可见光，因此很难使聚焦光束直接照射在腔内陶瓷头上，也难以确保光纤端面恰好在聚焦透镜焦点上。为了降低耦合难度，设计了二次耦合方案，分别在真空腔封装前后进行一次光路准直调节。In this experiment, due to the limitation of the cavity structure, the distance between the focusing lens and the input end of the optical fiber is relatively long, and the diameter of the ceramic head is small, and the wavelength of the laser used is invisible light, so it is difficult to directly irradiate the focused beam on the ceramic head in the cavity. It is difficult to ensure that the fiber end face is exactly in focus of the focusing lens. In order to reduce the coupling difficulty, a secondary coupling scheme is designed, and the optical path collimation adjustment is performed once before and after the vacuum cavity packaging.
在安装MOT腔前侧窗玻璃与探测腔前侧窗玻璃以前先进行第一次光路初步准直，由于未安装窗玻璃及相应法兰，感光片和功率计探头可以放置在腔体内部精确定位聚焦光斑位置以及光纤输出光功率。第一次耦合中需记录最大耦合效率及最优光场模式时的五维调节台各维度精密螺杆数值，并在耦合面窗口上标定聚焦光束位置，作为第二次耦合调节的参照。Before installing the front side window glass of the MOT cavity and the front side window glass of the detection cavity, the first preliminary alignment of the optical path is carried out. Since the window glass and the corresponding flange are not installed, the photosensitive film and the power meter probe can be placed inside the cavity for precise positioning and focusing Spot position and fiber output optical power. In the first coupling, it is necessary to record the precision screw values of each dimension of the five-dimensional adjustment stage at the maximum coupling efficiency and the optimal light field mode, and calibrate the focused beam position on the coupling surface window as a reference for the second coupling adjustment.
第一次耦合后安装窗玻璃并将真空腔密封，进行加热与抽真空等操作。该系列操作后，由于腔体震动等因素，光纤与耦合光路的相对位置可能产生微小的变化。需进行第二次光路准直，在第一次的耦合基础上小范围进行微调。After the first coupling, the window glass is installed and the vacuum chamber is sealed, and operations such as heating and vacuuming are performed. After this series of operations, due to factors such as cavity vibration, the relative position of the optical fiber and the coupling optical path may change slightly. A second optical path alignment is required, and fine-tuning is performed in a small range on the basis of the first coupling.
步骤二、光纤输出的功率和模式监测；Step 2, the power and mode monitoring of the optical fiber output;
最优的光纤耦合条件既要获得较大的耦合光功率，也要使传输光模式为基模，将原子束缚在空芯中央光强最大的区域。因此本发明采用功率计及CCD在腔外对光纤输出光斑的功率和模式进行监测。The optimal fiber coupling conditions not only need to obtain a larger coupling optical power, but also make the transmitted optical mode the fundamental mode, and bind the atoms in the region with the highest optical intensity in the center of the hollow core. Therefore, the present invention uses a power meter and a CCD to monitor the power and mode of the optical fiber output spot outside the cavity.
本发明的优点在于：The advantages of the present invention are:
(1)本发明解决了由于空芯光子晶体光纤输入端距聚焦透镜较远而使耦合效率难以提高的难题，保证了空间激光——光纤耦合的调节精度，获得了较好的高斯型光场分布；(1) The present invention solves the problem that the coupling efficiency is difficult to improve because the input end of the hollow-core photonic crystal fiber is far away from the focusing lens, ensures the adjustment accuracy of the space laser-fiber coupling, and obtains a better Gaussian light field distributed;
(2)本发明采用CCD在真空腔外实时监测光纤的近场分布，解决了长距离成像时放大倍率较小的问题，辅助了空间激光——光纤的耦合调节过程；(2) The present invention adopts CCD to monitor the near-field distribution of optical fiber in real time outside the vacuum cavity, which solves the problem of small magnification during long-distance imaging, and assists the space laser-optical fiber coupling adjustment process;
(3)本发明是原子干涉的共性技术，可以应用于其他的需要原子操控或导引的干涉仪。(3) The present invention is a general technology of atomic interference, and can be applied to other interferometers that require atomic manipulation or guidance.
附图说明Description of drawings
图1为原子导引真空腔中光纤耦合基本光路；Figure 1 shows the basic optical path of fiber coupling in an atom-guided vacuum cavity;
图2为空间激光——光纤的耦合光路；Figure 2 is the coupling optical path of space laser-optical fiber;
图3为真空腔中功率计放置位置12、13；Fig. 3 shows the placement positions 12 and 13 of the power meter in the vacuum chamber;
图4为光纤输出端模式监测的方案；Fig. 4 is the scheme of optical fiber output mode monitoring;
图5为仿真所得的聚焦光束束腰与激光耦合效率的关系；Figure 5 is the relationship between the simulated beam waist of the focused beam and the laser coupling efficiency;
图6为实验上监测到的光纤输出光斑模式。Fig. 6 is the optical fiber output spot mode monitored experimentally.
图中：In the picture:
1-原子源腔 2-探测腔 3-空芯光子晶体光纤1-atom source cavity 2-detection cavity 3-hollow core photonic crystal fiber
4-窗玻璃 5-法兰 6-平凹透镜4-window glass 5-flange 6-plano-concave lens
7-平凸透镜 8-聚焦透镜 9-激光准直器7-plano-convex lens 8-focusing lens 9-laser collimator
10-透镜套筒 14-CCD 15-显微物镜10-lens tube 14-CCD 15-microscope objective lens
16-成像物镜16- Imaging objective lens
具体实施方式Detailed ways
下面将结合附图对本发明作进一步详细说明。The present invention will be described in further detail below in conjunction with the accompanying drawings.
本发明一种用于冷原子导引的空间激光—光纤的耦合调节与模式监测方法，具体步骤如下：The present invention is a space laser-fiber coupling adjustment and mode monitoring method for cold atom guidance, and the specific steps are as follows:
步骤一、空间激光——光纤的耦合调节；Step 1. Space laser-optical fiber coupling adjustment;
图1为空芯光子晶体光纤导引原子实验装置的基本结构。冷原子束流在原子源腔(MOT腔)1中产生，导引激光从探测腔2左侧耦合进空芯光子晶体光纤3中，并激发纤芯中的基模，光纤左端输出的光场形成势阱将原子束流陷俘于高斯光束中心，原子保持其初始速度沿光纤中心轴向匀速被导引。光子晶体光纤右端位于探测腔2中心，距右侧窗口法兰5的距离为45mm。本实验采用在腔外将激光器输出的准直光进行扩束后再聚焦在光纤端面的方法，因此对聚焦透镜的焦距要求大于45mm。光纤左端位于原子源腔1中1mm小孔波片4的小孔中心，与腔体最左侧窗口法兰5的距离为105mm。Figure 1 shows the basic structure of the experimental device for guiding atoms with a hollow-core photonic crystal fiber. The cold atomic beam is generated in the atomic source cavity (MOT cavity) 1, and the guiding laser is coupled into the hollow-core photonic crystal fiber 3 from the left side of the detection cavity 2, and excites the fundamental mode in the fiber core, and the light field output from the left end of the fiber A potential well is formed to trap the atomic beam in the center of the Gaussian beam, and the atoms are guided at a constant speed along the central axis of the optical fiber while maintaining their initial velocity. The right end of the photonic crystal fiber is located at the center of the detection cavity 2, and the distance from the flange 5 of the right window is 45mm. This experiment adopts the method of expanding the collimated light output by the laser outside the cavity and then focusing it on the end face of the fiber, so the focal length of the focusing lens is required to be greater than 45mm. The left end of the optical fiber is located at the center of the pinhole of the 1mm pinhole wave plate 4 in the atom source cavity 1, and the distance from the leftmost window flange 5 of the cavity is 105 mm.
图2为导引激光与空芯光子晶体光纤耦合调试装置的基本结构。波长为1064nm的激光经准直器出射后束腰直径ω0约1mm。准直激光先被平凹透镜6、平凸透镜7透镜组合扩束，再被聚焦透镜8聚焦在空芯光子晶体光纤端面上。聚焦光束束腰直径和光纤模场直径需要达到较好的匹配才能使耦合效率最大。在纤芯直径10μm时，可仿真计算光束束腰与空间激光——光纤耦合效率的关系，如图5。可知光束束腰直径为6.4μm时，激光耦合效率最大，约98％。本实验所用透镜及光纤参数如下表所示。经计算可得该实验条件下光束束腰直径约8.124μm，耦合效率91.9％。Fig. 2 shows the basic structure of the device for coupling and debugging the guiding laser and the hollow-core photonic crystal fiber. The beam waist diameter ω0 of the laser beam with a wavelength of 1064 nm is about 1 mm after exiting the collimator. The collimated laser beam is expanded by the combination of plano-concave lens 6 and plano-convex lens 7, and then focused by focusing lens 8 on the end face of the hollow-core photonic crystal fiber. The waist diameter of the focused beam and the mode field diameter of the fiber need to be well matched to maximize the coupling efficiency. When the core diameter is 10 μm, the relationship between the beam waist and the spatial laser-fiber coupling efficiency can be simulated and calculated, as shown in Figure 5. It can be seen that when the beam waist diameter is 6.4 μm, the laser coupling efficiency is the largest, about 98%. The lens and fiber parameters used in this experiment are shown in the table below. It can be calculated that under the experimental conditions, the beam waist diameter is about 8.124 μm, and the coupling efficiency is 91.9%.
耦合调节目的是使光纤3、透镜套筒10、激光准直器9三者位于同一水平线，且透镜套筒10中聚焦透镜8的焦点位于探测腔中的光纤端面上，此时聚焦光束束腰位置与光纤端面重合，光纤输入端光斑尺寸最小，光功率密度最大。The purpose of coupling adjustment is to make the optical fiber 3, the lens sleeve 10, and the laser collimator 9 lie on the same horizontal line, and the focal point of the focusing lens 8 in the lens sleeve 10 is located on the end surface of the optical fiber in the detection cavity. At this time, the beam waist of the focused beam The position coincides with the end face of the fiber, the spot size of the fiber input end is the smallest, and the optical power density is the largest.
第一次耦合：First coupling:
激光准直器9安装在三维平移台上，每个维度平移范围13mm，平移精度3μm；透镜套筒10整体安装在五维(X、Y、Z、)调节台上。透镜套筒10与光纤3及激光准直器9的准直通过五维调节台上的X、Y、调节；聚焦透镜8距光纤端面的距离通过螺杆Z调节。五维调节台X、Y、Z方向平移范围13mm，平移精度3μm；The laser collimator 9 is mounted on a three-dimensional translation stage, with a translation range of 13 mm in each dimension and a translation accuracy of 3 μm; the lens sleeve 10 is installed on a five-dimensional (X, Y, Z, ) on the adjustment table. The collimation of the lens sleeve 10, the optical fiber 3 and the laser collimator 9 passes through the X, Y, Adjustment; the distance between the focusing lens 8 and the end face of the optical fiber is adjusted by the screw Z. The five-dimensional adjustment platform has a translation range of 13mm in X, Y, and Z directions, and a translation accuracy of 3μm;
聚焦光束没有与光纤进行精确的对准时，高功率的聚焦光斑会对光纤包层结构造成损伤，同时也威胁实验者的安全。因此先采用小功率(约10mw)激光进行耦合调节。在MOT腔中位置12放置功率计探头，探头中心位置与光纤3水平；调节五维平移台使光纤3输出功率最大且光斑模式为高斯型分布，记录此时五维调节台各维度数值；利用感光片在耦合面窗玻璃上找到此时光斑位置并进行标定，便于真空腔封装后调节耦合光路与光纤的相对位置。When the focused beam is not precisely aligned with the fiber, the high-power focused spot will damage the cladding structure of the fiber and threaten the safety of the experimenter. Therefore, a low-power (about 10mw) laser is first used for coupling adjustment. Place a power meter probe at position 12 in the MOT cavity, and the center of the probe is at the level of the optical fiber 3; adjust the five-dimensional translation stage so that the output power of the optical fiber 3 is the maximum and the spot pattern is Gaussian, and record the values of each dimension of the five-dimensional adjustment stage at this time; use The photosensitive film finds the position of the light spot on the window glass of the coupling surface and calibrates it, which is convenient for adjusting the relative position of the coupling optical path and the optical fiber after vacuum cavity packaging.
第二次耦合：Second coupling:
若加热后光纤相对腔外耦合光路的位置只有微小变化，光斑应仍处于陶瓷头11端面上，可略微调节五维调节台将光斑移至陶瓷头中心。也可通过第一次耦合时在耦合面窗口上标定的光斑位置来调节聚焦光束相对陶瓷头11的位置。在第一次耦合调节基础上进行微调，光功率最大时可估算MOT腔1内光纤输出端的光功率，进而推算实际耦合效率。使用CCD观察此时光纤输出端的光场分布，如一部分光耦合进包层中或光场分布不均匀，需微调五维调节台使光场趋于高斯分布。If the position of the optical fiber relative to the coupling optical path outside the cavity changes only slightly after heating, the light spot should still be on the end face of the ceramic head 11, and the five-dimensional adjustment table can be slightly adjusted to move the light spot to the center of the ceramic head. The position of the focused beam relative to the ceramic head 11 can also be adjusted by the spot position marked on the coupling surface window during the first coupling. Fine-tuning is performed on the basis of the first coupling adjustment. When the optical power is at its maximum, the optical power at the output end of the optical fiber in the MOT cavity 1 can be estimated, and then the actual coupling efficiency can be estimated. Use the CCD to observe the light field distribution at the fiber output end at this time. If a part of the light is coupled into the cladding or the light field distribution is uneven, it is necessary to fine-tune the five-dimensional adjustment table to make the light field tend to Gaussian distribution.
步骤二、光纤输出的功率和模式监测；Step 2, the power and mode monitoring of the optical fiber output;
同上所述，安装MOT腔前侧窗玻璃与探测腔前侧窗玻璃前先进行一次光路初步准直，由于未安装窗玻璃及相应法兰，可分别测得光纤端面12到法兰13处的光功率，图3。尽管光纤输出光场在距光纤105mm的位置已有较大的发散，且功率值随距离增大衰减，可沿光束方向每隔一段距离测得相应功率值，拟合出功率随距离衰减曲线。若真空腔封装后所测13处最大耦合光功率P13，可根据拟合规律估算12处光功率P12，则耦合效率η＝P12/Pin。光纤输入光功率Pin可通过调节激光放大器电流进行调节。As mentioned above, before installing the front side window glass of the MOT cavity and the front side window glass of the detection cavity, perform a preliminary alignment of the optical path. Since the window glass and the corresponding flange are not installed, the optical fiber end face 12 to flange 13 can be measured respectively. Optical Power, Figure 3. Although the optical fiber output light field has a large divergence at the position of 105mm away from the optical fiber, and the power value attenuates with the increase of distance, the corresponding power value can be measured at intervals along the beam direction, and the power attenuation curve with distance can be fitted. If the maximum coupling optical power P13 at 13 locations is measured after the vacuum cavity is packaged, the optical power P12 at 12 locations can be estimated according to the fitting law, then the coupling efficiency η=P12 /Pin . The optical fiber input optical power Pin can be adjusted by adjusting the current of the laser amplifier.
监测耦合模式对CCD14物镜的参数要求主要有放大倍率与工作距离：The parameter requirements of the monitoring coupling mode for the CCD14 objective lens mainly include magnification and working distance:
1)放大倍率：由于光子晶体光纤3模场直径(1/e2)约7.5μm，而CCD传感面尺寸为mm量级，因此放大率需在10X～200X之间进行选择，放大率越大光斑成像细节越清晰；2)工作距离：从装置结构设计图1来看，若假设光纤端面和1mm小孔反射镜4齐平时，光纤端面距最左侧窗玻璃法兰5的距离为105mm。因此物镜工作距离大于105mm即可。1) Magnification: Since the 3-mode field diameter (1/e2 ) of photonic crystal fiber is about 7.5 μm, and the size of CCD sensing surface is on the order of mm, the magnification needs to be selected between 10X and 200X. Large spot imaging details are clearer; 2) Working distance: From the device structure design diagram 1, if it is assumed that the fiber end face is flush with the 1mm small hole reflector 4, the distance between the fiber end face and the leftmost window glass flange 5 is 105mm . Therefore, the working distance of the objective lens can be greater than 105mm.
由以上的分析可以看出，对本实验中光纤输出模场的成像既需要放大倍数大，也需要工作距离长的物镜。而普通成像物镜的设计中放大倍率和工作距离是两个相互制约的参数，CCD14前的显微物镜15工作距离只有mm量级，不能直接用于在实际装置中进行监控。因此设计了将成像物镜16与显微物镜15进行组合的光纤耦合输出的模式监测方案，如图4。采用工作距离为110mm左右的成像镜头16将光纤输出的近场分布成像在显微物镜15的焦点上进行二次放大。本发明中显微物镜可选的放大倍数为20X、40X、60X，成像物镜放大倍率1.725X～2.2X，因此总放大倍率约40X～120X。光纤输出的光斑模式如图6所示。It can be seen from the above analysis that the imaging of the fiber output mode field in this experiment requires both a large magnification and an objective lens with a long working distance. However, the magnification and working distance are two mutually restrictive parameters in the design of common imaging objective lenses. The working distance of the microscopic objective lens 15 in front of the CCD 14 is only on the order of mm, which cannot be directly used for monitoring in an actual device. Therefore, a fiber-coupled mode monitoring solution combining the imaging objective lens 16 and the microscopic objective lens 15 is designed, as shown in FIG. 4 . An imaging lens 16 with a working distance of about 110 mm is used to image the near-field distribution output by the optical fiber on the focal point of the microscope objective lens 15 for secondary amplification. The optional magnifications of the microscopic objective lens in the present invention are 20X, 40X, and 60X, and the magnification of the imaging objective lens is 1.725X to 2.2X, so the total magnification is about 40X to 120X. The spot mode of the fiber output is shown in Figure 6.
本发明提出了一种用于原子导引的空间激光——光纤的耦合调节与模式监测方法。解决了由于空芯光子晶体光纤输入端距聚焦透镜较远而使耦合效率难以提高的难题，保证了空间激光——光纤耦合的调节精度；并采用功率计与CCD在真空腔外实时监测耦合光功率与光纤的近场分布，解决了长距离成像时放大倍率较小的问题，为后续光纤导引原子过程奠定了基础。The invention proposes an atom-guided space laser-optical fiber coupling adjustment and mode monitoring method. It solves the problem that the coupling efficiency is difficult to improve because the input end of the hollow-core photonic crystal fiber is far away from the focusing lens, and ensures the adjustment accuracy of the space laser-fiber coupling; and uses a power meter and CCD to monitor the coupled light in real time outside the vacuum cavity The near-field distribution of power and optical fiber solves the problem of low magnification in long-distance imaging, and lays the foundation for the subsequent process of fiber-guided atoms.
本发明与现有技术的不同在于：The present invention differs from the prior art in that:
(1)为了简化腔体结构，耦合光路设计在腔外进行，因此聚焦透镜的焦距收到腔体结构约束。本发明解决了导引激光与空芯光纤进行长距离耦合时耦合效率难以增大的问题，需要光路中的各光学元件有较高的调节精度，且能根据激光器的准直输出激光的模场直径灵活改变光路中的透镜组合方式。(1) In order to simplify the cavity structure, the coupling optical path is designed outside the cavity, so the focal length of the focusing lens is restricted by the cavity structure. The invention solves the problem that the coupling efficiency is difficult to increase when the guiding laser is coupled with the hollow-core optical fiber for a long distance, and requires that each optical element in the optical path has a high adjustment accuracy, and can output the mode field of the laser according to the collimation of the laser The diameter flexibly changes the combination of lenses in the optical path.
(2)解决了长距离模式观测时成像放大倍率较小的问题，并采用功率计与CCD在真空腔外实时监测耦合光功率与光纤的近场分布，辅助激光与光纤的耦合调节过程。(2) Solve the problem of small imaging magnification in long-distance mode observation, and use power meter and CCD to monitor the near-field distribution of coupling optical power and optical fiber in real time outside the vacuum cavity, and assist the coupling adjustment process of laser and optical fiber.
图2为导引激光和空芯光子晶体光纤的耦合调试装置，图3为光纤输出的功率监测装置，图4为光纤输出的模式监测装置。图2对应步骤一的空间激光——光纤的耦合调节过程，图3和图4对应步骤二的光纤输出的功率和模式监测过程。Figure 2 is a coupling debugging device for guiding laser and hollow-core photonic crystal fiber, Figure 3 is a power monitoring device for fiber output, and Figure 4 is a mode monitoring device for fiber output. Figure 2 corresponds to the space laser-fiber coupling adjustment process in Step 1, and Figure 3 and Figure 4 correspond to the power and mode monitoring process of the fiber output in Step 2.
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| CN201711237579.3ACN107861200B (en) | 2017-11-30 | 2017-11-30 | A kind of the fiber coupling adjusting and monitoring method of the space laser for cold atom guiding |
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| CN201711237579.3ACN107861200B (en) | 2017-11-30 | 2017-11-30 | A kind of the fiber coupling adjusting and monitoring method of the space laser for cold atom guiding |
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