CN108414452A - A kind of nanostructure magnetic measuring device - Google Patents
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Abstract
本发明涉及物理测量技术领域，一种纳米结构磁性测量装置，包括激光器、分束器、凸透镜I、光电探测器、锁相放大器、棱镜偏振器、凸透镜II、保偏光纤I、电光调制器、保偏光纤II、凸透镜III、波片I、透镜台、原子力显微镜、探针、样品、磁铁、样品台、信号发生器、示波器、波片II、凸透镜IV、平面镜，样品、磁铁及样品台依次位于探针正下方，探针为圆台形状，探针中的通孔I和通孔II的轴线分别位于探针圆台轴线的两侧、且均与探针圆台轴线成45度角，保偏光纤I具有慢轴和快轴，棱镜偏振器的透射轴与保偏光纤I的慢轴平行，保偏光纤I的慢轴位于电光调制器的横磁轴和横电轴之间夹角的角平分线上，电光调制器的横磁轴与保偏光纤II的慢轴平行。
The invention relates to the technical field of physical measurement, a nanostructure magnetic measurement device, comprising a laser, a beam splitter, a convex lens I, a photodetector, a lock-in amplifier, a prism polarizer, a convex lens II, a polarization maintaining fiber I, an electro-optical modulator, Polarization maintaining fiber II, convex lens III, wave plate I, lens stage, atomic force microscope, probe, sample, magnet, sample stage, signal generator, oscilloscope, wave plate II, convex lens IV, plane mirror, sample, magnet and sample stage in order Located directly below the probe, the probe is in the shape of a truncated cone, the axes of the through hole I and the through hole II in the probe are respectively located on both sides of the axis of the circular pedestal of the probe, and are at an angle of 45 degrees to the axis of the circular pedestal of the probe, and the polarization-maintaining optical fiber I has a slow axis and a fast axis, the transmission axis of the prism polarizer is parallel to the slow axis of the polarization maintaining fiber I, and the slow axis of the polarization maintaining fiber I is located at the angle bisector of the angle between the transverse magnetic axis and the transverse electric axis of the electro-optic modulator On the line, the transverse magnetic axis of the electro-optic modulator is parallel to the slow axis of the polarization-maintaining fiber II.
Description
技术领域technical field
本发明涉及物理测量技术领域，尤其是一种采用光束干涉方法来研究材料表面单个纳米结构磁光克尔信号的一种纳米结构磁性测量装置。The invention relates to the technical field of physical measurement, in particular to a nanostructure magnetic measurement device for studying the magneto-optic Kerr signal of a single nanostructure on the surface of a material by using a beam interference method.
背景技术Background technique
磁光克尔效应测量装置是材料表面磁性研究中的一种重要手段，其工作原理是基于由光与磁化介质间相互作用而引起的磁光克尔效应，其不仅能够进行单原子层厚度材料的磁性检测，而且可实现非接触式测量，在磁性超薄膜的磁有序、磁各向异性、层间耦合和磁性超薄膜的相变行为等方面的研究中都有重要应用。磁光克尔效应测量装置主要是通过检测一束线偏振光在材料表面反射后的偏振态变化引起的光强变化进行样品表面的磁化观测。现有技术缺陷一：传统的聚焦克尔显微镜的空间分辨率由光学衍射极限所决定，其成像的效果极易受到光学元件限制，因此无法得到纳米尺度的磁化动态特征。现有技术缺陷二：在某些通过测量两束光在样品表面的干涉来得到样品的磁化信息的方法中，两束光的光路是分开控制的，而且需要在探测之前重新合并，因此需要较多的光学元件，因此得到的信号的信噪比较低，现有技术缺陷三：现有技术的干涉法测样品的克尔旋转的装置中，只能测量极向克尔效应，所述一种纳米结构磁性测量装置能解决问题。The magneto-optical Kerr effect measurement device is an important means in the study of material surface magnetism. Its working principle is based on the magneto-optic Kerr effect caused by the interaction between light and magnetized media. Magnetic detection, and non-contact measurement can be realized, and it has important applications in the research of magnetic order, magnetic anisotropy, interlayer coupling and phase transition behavior of magnetic ultrathin films. The magneto-optical Kerr effect measurement device is mainly used to observe the magnetization of the sample surface by detecting the change of the polarization state of a beam of linearly polarized light caused by the change of the polarization state after the material surface is reflected. Defect 1 of the existing technology: the spatial resolution of the traditional focusing Kerr microscope is determined by the optical diffraction limit, and its imaging effect is easily limited by optical elements, so it is impossible to obtain the dynamic characteristics of magnetization at the nanometer scale. Defect 2 of the prior art: In some methods of obtaining the magnetization information of the sample by measuring the interference of two beams of light on the surface of the sample, the optical paths of the two beams of light are controlled separately and need to be recombined before detection, so more There are many optical components, so the signal-to-noise ratio of the obtained signal is low. The third defect of the prior art: in the device for measuring the Kerr rotation of the sample by interferometry in the prior art, only the polar Kerr effect can be measured. A nanostructured magnetic measurement device could solve the problem.
发明内容Contents of the invention
为了解决上述问题，本发明采用同一束光的两个正交偏振分量干涉的方法来获得样品表面的磁化信息，光的两个正交偏振分量共用一个光路，减少光路中的光学元件，提高了信噪比，本发明装置通过采用斜入射的光束能够测量克尔效应的纵向、横向和极向三个分量；另外，本发明装置采用具有通孔的原子力显微镜探针，能够得到样品表面纳米尺度结构的磁化动态特征。In order to solve the above problems, the present invention adopts the method of two orthogonal polarization components interference of the same beam of light to obtain the magnetization information of the sample surface, the two orthogonal polarization components of light share one optical path, reduce the optical elements in the optical path, and improve the Signal-to-noise ratio, the device of the present invention can measure the longitudinal, lateral and polar components of the Kerr effect by using obliquely incident light beams; in addition, the device of the present invention uses an atomic force microscope probe with a through hole, which can obtain the nanometer scale of the sample surface. Magnetization dynamics of structures.
本发明所采用的技术方案是：The technical scheme adopted in the present invention is:
所述一种纳米结构磁性测量装置主要包括激光器、分束器、凸透镜I、光电探测器、锁相放大器、棱镜偏振器、凸透镜II、保偏光纤I、电光调制器、保偏光纤II、凸透镜III、波片I、透镜台、原子力显微镜、探针、样品、磁铁、样品台、信号发生器、示波器、波片 II、凸透镜IV、平面镜，激光器的波长在400纳米到800纳米范围可调，xyz为空间直角坐标系、xy平面为水平面，zx平面与水平面垂直，原子力显微镜位于透镜台下方，探针位于原子力显微镜下方，所述探针为原子力显微镜探针且为圆台形状，所述圆台的上底面直径为3 微米、下底面直径为1.5微米，所述圆台轴线方向与水平面垂直，样品、磁铁及样品台依次位于探针的正下方，波片I为半波片，波片II为1/4波片，所述探针中具有通孔I和通孔II，所述通孔I、通孔II的轴线和探针圆台的轴线均位于zx平面内，所述通孔I和通孔II的轴线分别位于探针圆台轴线的两侧、且均与所述探针圆台轴线成45度角，光电探测器与锁相放大器电缆连接，信号发生器、示波器分别电缆连接样品台，保偏光纤I具有慢轴和快轴，棱镜偏振器的透射轴与保偏光纤I的慢轴平行，保偏光纤I的慢轴位于电光调制器的横磁轴和横电轴之间夹角的角平分线上，电光调制器的横磁轴与保偏光纤II的慢轴平行，所述探针中的通孔I和通孔II的直径均为200纳米，所述保偏光纤I长度为2米，所述保偏光纤II长度为 9米。激光器发出的光依次经过分束器、棱镜偏振器、凸透镜II、保偏光纤I后，进入电光调制器，光在电光调制器中形成两个正交的偏振分量为面内偏振和面外偏振，且每个分量加上相位φ(t)＝φ0cos(ωt)，两个光分量的相位时间差为τ，光束从电光调制器出来后进入保偏光纤II，光的两个正交的偏振分量分别沿保偏光纤II的快轴和慢轴传输，光离开保偏光纤II 后，依次通过凸透镜III、波片I、透镜台、原子力显微镜、通孔I到达样品表面，并第一次被反射，第一次反射光依次经过通孔II、原子力显微镜、透镜台、波片II、凸透镜IV到达平面镜，并第二次被反射，第二次反射光依次经过凸透镜IV、波片II、透镜台、原子力显微镜、通孔II到达样品表面，并第三次被样品表面反射，第三次反射光依次经过通孔I、原子力显微镜、透镜台、波片I、凸透镜III、保偏光纤II、电光调制器、保偏光纤I、凸透镜II、棱镜偏振器，再被分束器偏转后，经过凸透镜I进入光电探测器，第三次反射光的两个偏振分量在光电探测器处发生干涉，分别沿保偏光纤II的慢轴和快轴传输的光的两个正交偏振分量，从保偏光纤II输出后对应的琼斯矩阵分别表示为和在经过波片I后，所述光的两个正交偏振分量对应的琼斯矩阵转变为和其中 为相位角，定义为表示光束在经过样品表面的两次反射后回到电光调制器整个过程的琼斯矩阵，光电探测器中得到的光的两个正交偏振分量的相位差表示为相位差在x、y、z方向的分量分别为αx、αy、αz，对光电探测器中得到的光电流进行傅里叶分析，锁相放大器得到光电流的一阶谐波分量：和二阶谐波分量：考虑对称性，αk简化为其中ω是电光调制器的时间依赖的相位φ(t)的角频率，Iinc是激光器发射的光的光强，γ为光束两次经过下列光学元件分束器、棱镜偏振器、凸透镜II、保偏光纤I、电光调制器、保偏光纤II、凸透镜III、凸透镜IV，并被样品表面反射两次后光强的剩余比例，J1和J2分别是一阶和二阶是贝塞尔方程，αk是样品磁化分量的线性方程，x、y、z方向的样品磁化分量mx、my、mz对αk的贡献取决于 样品的反射系数、光路中的光学元件等。Described a kind of nanostructure magnetic measurement device mainly comprises laser, beam splitter, convex lens I, photodetector, lock-in amplifier, prism polarizer, convex lens II, polarization maintaining fiber I, electro-optic modulator, polarization maintaining fiber II, convex lens III, wave plate I, lens stage, atomic force microscope, probe, sample, magnet, sample stage, signal generator, oscilloscope, wave plate II, convex lens IV, plane mirror, the wavelength of the laser is adjustable from 400 nm to 800 nm, xyz is a space Cartesian coordinate system, the xy plane is a horizontal plane, the zx plane is perpendicular to the horizontal plane, the atomic force microscope is located under the lens stage, the probe is located under the atomic force microscope, the probe is an atomic force microscope probe and is in the shape of a circular truncated table, the circular table The diameter of the upper bottom surface is 3 microns, and the diameter of the lower bottom surface is 1.5 microns. The axis direction of the circular platform is perpendicular to the horizontal plane. The sample, magnet and sample stage are located directly below the probe in turn. The wave plate I is a half-wave plate, and the wave plate II is 1 /4 wave plate, the probe has a through hole I and a through hole II, the axis of the through hole I, the through hole II and the axis of the probe circular platform are all located in the zx plane, the through hole I and the through hole The axes of II are respectively located on both sides of the axis of the probe round table, and are at an angle of 45 degrees to the axis of the probe round table. The photodetector is connected to the lock-in amplifier cable, and the signal generator and oscilloscope are respectively connected to the sample stage by cables, and the polarization maintaining The optical fiber I has a slow axis and a fast axis, the transmission axis of the prism polarizer is parallel to the slow axis of the polarization maintaining fiber I, and the slow axis of the polarization maintaining fiber I is located at the angle between the transverse magnetic axis and the transverse electric axis of the electro-optic modulator On the bisector, the transverse magnetic axis of the electro-optic modulator is parallel to the slow axis of the polarization-maintaining fiber II, the diameters of the through-hole I and the through-hole II in the probe are both 200 nanometers, and the length of the polarization-maintaining fiber I is 2 meters, and the length of the polarization-maintaining fiber II is 9 meters. The light emitted by the laser passes through the beam splitter, prism polarizer, convex lens II, and polarization-maintaining fiber I in sequence, and then enters the electro-optic modulator. The light forms two orthogonal polarization components in the electro-optic modulator, which are in-plane polarization and out-of-plane polarization. , and each component is added with phase φ(t)=φ 0 cos(ωt), the phase time difference of the two optical components is τ, the light beam enters the polarization-maintaining fiber II after coming out of the electro-optic modulator, and the two orthogonal The polarization components are respectively transmitted along the fast axis and slow axis of the polarization maintaining fiber II. After the light leaves the polarization maintaining fiber II, it passes through the convex lens III, the wave plate I, the lens stage, the atomic force microscope, and the through hole I to reach the sample surface, and for the first time is reflected, the first reflected light passes through hole II, atomic force microscope, lens stage, wave plate II, and convex lens IV to reach the plane mirror, and is reflected for the second time, and the second reflected light passes through convex lens IV, wave plate II, The lens stage, the atomic force microscope, and the through hole II reach the sample surface, and are reflected by the sample surface for the third time, and the third reflected light passes through the through hole I, the atomic force microscope, the lens stage, the wave plate I, the convex lens III, and the polarization-maintaining fiber II in sequence , electro-optic modulator, polarization maintaining fiber I, convex lens II, prism polarizer, after being deflected by the beam splitter, it enters the photodetector through the convex lens I, and the two polarization components of the third reflected light interfere at the photodetector , the two orthogonal polarization components of the light transmitted along the slow axis and the fast axis of the polarization maintaining fiber II respectively, and the corresponding Jones matrices after output from the polarization maintaining fiber II are expressed as and After passing through the wave plate I, the Jones matrix corresponding to the two orthogonal polarization components of the light is transformed into and in is the phase angle, defined as In order to represent the Jones matrix of the whole process of the light beam returning to the electro-optic modulator after two reflections on the sample surface, the phase difference of the two orthogonal polarization components of the light obtained in the photodetector is expressed as The components of the phase difference in the x, y, and z directions are α x , α y , and α z respectively. Fourier analysis is performed on the photocurrent obtained in the photodetector, and the lock-in amplifier obtains the first-order harmonic component of the photocurrent: and second harmonic components: Considering the symmetry, α k simplifies to where ω is the angular frequency of the time-dependent phase φ(t) of the electro-optic modulator, I inc is the light intensity of the light emitted by the laser, and γ is the beam passing through the following optical components twice: beam splitter, prism polarizer, convex lens II, Polarization-maintaining fiber I, electro-optic modulator, polarization-maintaining fiber II, convex lens III, convex lens IV, and the remaining proportion of light intensity after being reflected twice by the sample surface, J 1 and J 2 are the first-order and second-order Bessel Equation, α k is the linear equation of the sample magnetization component, the contribution of the sample magnetization components m x , m y , m z in the x, y , z directions to α k depends on The reflection coefficient of the sample, the optical elements in the light path, etc.
极向克尔效应对应于磁化的z方向的分量，纵向克尔效应对应于磁化的y方向的分量，横向克尔效应对应于磁化的x方向的分量，由于样品磁化分量在不同的晶体对称操作下的转变不同，应该选择合适的P1和P2以及光路中的光学元件，以使得极向或纵向或横向磁光克尔效应的贡献占主要部分。The polar Kerr effect corresponds to the z-direction component of the magnetization, the longitudinal Kerr effect corresponds to the y-direction component of the magnetization, and the transverse Kerr effect corresponds to the x-direction component of the magnetization, since the sample magnetization components operate symmetrically in different crystals The transformation under different conditions should choose the appropriate P 1 and P 2 and the optical elements in the optical path so that the contribution of the polar or longitudinal or transverse magneto-optical Kerr effect accounts for the main part.
本发明装置采用具有通孔的原子力显微镜探针，能够得到样品表面纳米尺度结构的磁化信息，其次，本发明采用同一束光的两个正交偏振分量干涉的方法来获得样品表面的磁化信息，两个偏振光分量共用一个光路，避免光束分离和重新汇集，能够相对较容易地保证两个光束以同样的光路传播，并减少光路中的光学元件，使得信号较少地受样品以及干涉环路中光学元件的移动影响，提高了信噪比。The device of the present invention adopts an atomic force microscope probe with a through hole, which can obtain the magnetization information of the nanoscale structure of the sample surface. Secondly, the present invention uses the interference method of two orthogonal polarization components of the same beam of light to obtain the magnetization information of the sample surface. The two polarized light components share one optical path, avoiding beam separation and recombination, it is relatively easy to ensure that the two beams propagate in the same optical path, and reduce the optical components in the optical path, so that the signal is less affected by the sample and the interference loop The effect of the movement of the optical components in the middle improves the signal-to-noise ratio.
利用所述一种纳米结构磁性测量装置进行测量的方法为：The method that utilizes described a kind of nanostructure magnetic measuring device to measure is:
测量纵向克尔效应的方法：Methods for measuring the longitudinal Kerr effect:
一.调整波片I的快轴与y方向成22.5度，调整波片II的快轴与y方向一致，使得在经过波片I后，入射光的两个正交偏振分量对应的琼斯矩阵为 1. Adjust the fast axis of wave plate I to be 22.5 degrees to the y direction, and adjust the fast axis of wave plate II to be consistent with the y direction, so that after passing through wave plate I, the Jones matrix corresponding to the two orthogonal polarization components of the incident light is
二.通过原子力显微镜使得探针逼近样品表面，令探针在二微米范围内扫描，扫描速度2纳米/秒，通过扫描中得到的样品表面轮廓来确定样品边缘位置；2. Make the probe approach the surface of the sample through the atomic force microscope, scan the probe within the range of 2 microns at a scanning speed of 2 nm/s, and determine the edge position of the sample through the surface profile of the sample obtained during scanning;
三.探针向上回缩距离50纳米，并关闭原子力显微镜的扫描反馈；3. The probe is retracted upward by 50 nanometers, and the scanning feedback of the atomic force microscope is turned off;
四.调整激光器的位置，使得激光器发出的激光束进入探针的通孔I，激光束在样品表面反射后形成的第一次反射光依次通过探针的通孔II、波片II、凸透镜IV到达平面镜，并被平面镜反射形成第二次反射光；4. Adjust the position of the laser so that the laser beam emitted by the laser enters the through hole I of the probe, and the first reflected light formed after the laser beam is reflected on the sample surface passes through the through hole II of the probe, the wave plate II, and the convex lens IV in turn. It reaches the plane mirror and is reflected by the plane mirror to form the second reflected light;
五.调整凸透镜IV和平面镜位置，使得第二次反射光通过探针的通孔II射到样品表面，并形成第三次反射光；5. Adjust the position of the convex lens IV and the plane mirror so that the second reflected light hits the sample surface through the through hole II of the probe, and forms the third reflected light;
六.第三次反射光依次经过探针的通孔I、原子力显微镜、透镜台、波片I、凸透镜III、保偏光纤II、电光调制器、保偏光纤I、凸透镜II、棱镜偏振器后被分束器偏转，经过凸透镜I进入光电探测器，光束的两个偏振分量在光电探测器处发生干涉；6. The third reflected light passes through the through hole I of the probe, the atomic force microscope, the lens stage, the wave plate I, the convex lens III, the polarization maintaining fiber II, the electro-optic modulator, the polarization maintaining fiber I, the convex lens II, and the prism polarizer. It is deflected by the beam splitter, enters the photodetector through the convex lens I, and the two polarization components of the beam interfere at the photodetector;
七.光电探测器输出信号至锁相放大器进行傅里叶分析后得到差分相位，在这个条件下，光强一阶谐波分量纵向克尔旋转rp和rs分别为P偏振光和S偏振光在样品表面的反射率；Seven. The output signal of the photodetector is sent to the lock-in amplifier for Fourier analysis to obtain the differential phase. Under this condition, the first-order harmonic component of the light intensity Vertical Kerr Rotation r p and rs are the reflectivity of P polarized light and S polarized light on the sample surface, respectively;
八.由公式计算得到克尔旋转。Eight. By the formula Calculate the Kerr rotation.
测量极向克尔效应方法：Measuring Pole Kerr Effect Method:
一.调整波片I的快轴与y方向成22.5度，调整波片II的快轴与y方向一致，使得在经过波片I后，入射光的两个正交偏振分量对应的琼斯矩阵为 1. Adjust the fast axis of wave plate I to be 22.5 degrees to the y direction, and adjust the fast axis of wave plate II to be consistent with the y direction, so that after passing through wave plate I, the Jones matrix corresponding to the two orthogonal polarization components of the incident light is
二.通过原子力显微镜使得探针逼近样品表面，令探针在二微米范围内扫描，扫描速度2纳米/秒，通过扫描中得到的样品表面轮廓来确定样品边缘位置；2. Make the probe approach the surface of the sample through the atomic force microscope, scan the probe within the range of 2 microns at a scanning speed of 2 nm/s, and determine the edge position of the sample through the surface profile of the sample obtained during scanning;
三.探针向上回缩距离50纳米，并关闭原子力显微镜的扫描反馈；3. The probe is retracted upward by 50 nanometers, and the scanning feedback of the atomic force microscope is turned off;
四.调整激光器的位置，使得激光器发出的激光束进入探针的通孔I，激光束在样品表面反射后形成的第一次反射光依次通过探针的通孔II、波片II、凸透镜IV到达平面镜，并被平面镜反射形成第二次反射光；4. Adjust the position of the laser so that the laser beam emitted by the laser enters the through hole I of the probe, and the first reflected light formed after the laser beam is reflected on the sample surface passes through the through hole II of the probe, the wave plate II, and the convex lens IV in turn. It reaches the plane mirror and is reflected by the plane mirror to form the second reflected light;
五.调整凸透镜IV和平面镜位置，使得第二次反射光通过探针的通孔II射到样品表面，并形成第三次反射光；5. Adjust the position of the convex lens IV and the plane mirror so that the second reflected light hits the sample surface through the through hole II of the probe, and forms the third reflected light;
六.第三次反射光依次经过探针的通孔I、原子力显微镜、透镜台、波片I、凸透镜III、保偏光纤II、电光调制器、保偏光纤I、凸透镜II、棱镜偏振器后被分束器偏转，经过凸透镜I进入光电探测器，光束的两个偏振分量在光电探测器处发生干涉；6. The third reflected light passes through the through hole I of the probe, the atomic force microscope, the lens stage, the wave plate I, the convex lens III, the polarization maintaining fiber II, the electro-optic modulator, the polarization maintaining fiber I, the convex lens II, and the prism polarizer. It is deflected by the beam splitter, enters the photodetector through the convex lens I, and the two polarization components of the beam interfere at the photodetector;
七.光电探测器输出信号至锁相放大器进行傅里叶分析后得到差分相位，在这个条件下，光强一阶谐波分量极向克尔旋转rp和rs分别为P偏振光和S偏振光在样品表面的反射率，Seven. The output signal of the photodetector is sent to the lock-in amplifier for Fourier analysis to obtain the differential phase. Under this condition, the first-order harmonic component of the light intensity Pole to Kerr rotation r p and rs are the reflectivity of P polarized light and S polarized light on the sample surface, respectively,
八.由公式计算得到克尔旋转。Eight. By the formula Calculate the Kerr rotation.
测量横向克尔效应方法：Method for measuring the transverse Kerr effect:
一.移除波片I，调整波片II的快轴与y方向成45度，使得在经过波片I后，入射光的两个正交偏振分量对应的琼斯矩阵为和 1. Remove the wave plate I, adjust the fast axis of the wave plate II to be 45 degrees to the y direction, so that after passing through the wave plate I, the Jones matrix corresponding to the two orthogonal polarization components of the incident light is and
二.通过原子力显微镜使得探针逼近样品表面，令探针在二微米范围内扫描，扫描速度2纳米/秒，通过扫描中得到的样品表面轮廓来确定样品边缘位置；2. Make the probe approach the surface of the sample through the atomic force microscope, scan the probe within the range of 2 microns at a scanning speed of 2 nm/s, and determine the edge position of the sample through the surface profile of the sample obtained during scanning;
三.探针向上回缩距离50纳米，并关闭原子力显微镜的扫描反馈；3. The probe is retracted upward by 50 nanometers, and the scanning feedback of the atomic force microscope is turned off;
四.调整激光器的位置，使得激光器发出的激光束进入探针的通孔I，激光束在样品表面反射后形成的第一次反射光依次通过探针的通孔II、波片II、凸透镜IV到达平面镜，并被平面镜反射形成第二次反射光；4. Adjust the position of the laser so that the laser beam emitted by the laser enters the through hole I of the probe, and the first reflected light formed after the laser beam is reflected on the sample surface passes through the through hole II of the probe, the wave plate II, and the convex lens IV in turn. It reaches the plane mirror and is reflected by the plane mirror to form the second reflected light;
五.调整凸透镜IV和平面镜位置，使得第二次反射光通过探针的通孔II射到样品表面，并形成第三次反射光；5. Adjust the position of the convex lens IV and the plane mirror so that the second reflected light hits the sample surface through the through hole II of the probe, and forms the third reflected light;
六.第三次反射光依次经过探针的通孔I、原子力显微镜、透镜台、波片I、凸透镜III、保偏光纤II、电光调制器、保偏光纤I、凸透镜II、棱镜偏振器后被分束器偏转，经过凸透镜I进入光电探测器，光束的两个偏振分量在光电探测器处发生干涉；6. The third reflected light passes through the through hole I of the probe, the atomic force microscope, the lens stage, the wave plate I, the convex lens III, the polarization maintaining fiber II, the electro-optic modulator, the polarization maintaining fiber I, the convex lens II, and the prism polarizer. It is deflected by the beam splitter, enters the photodetector through the convex lens I, and the two polarization components of the beam interfere at the photodetector;
七.光电探测器输出信号至锁相放大器进行傅里叶分析后得到差分相位，在这个条件下，光强一阶谐波分量横向克尔旋转rp和rs分别为P偏振光和S偏振光在样品表面的反射率；Seven. The output signal of the photodetector is sent to the lock-in amplifier for Fourier analysis to obtain the differential phase. Under this condition, the first-order harmonic component of the light intensity Lateral Kerr Rotation r p and rs are the reflectivity of P polarized light and S polarized light on the sample surface, respectively;
八.由公式计算得到克尔旋转。Eight. By the formula Calculate the Kerr rotation.
本发明的有益效果是：The beneficial effects of the present invention are:
现有技术的干涉法测样品的克尔旋转的装置中，光路的干涉环路有一定的面积，本发明装置通过同一个光束的两个正交的偏振分量代替两个独立光束来进行干涉测量，优点是：通过避免光束分离和重新汇集来相对较容易地保证两个光束以同样的光路传播，使得信号较少地受样品以及干涉环路中光学元件的移动影响。In the device for measuring the Kerr rotation of the sample by interferometry in the prior art, the interference loop of the optical path has a certain area, and the device of the present invention uses two orthogonal polarization components of the same beam instead of two independent beams to perform interferometry , the advantage is that it is relatively easy to ensure that the two beams propagate along the same optical path by avoiding beam splitting and recombining, making the signal less affected by the movement of the sample and optical components in the interference loop.
附图说明Description of drawings
下面结合本发明的图形进一步说明：Below in conjunction with figure of the present invention further illustrate:
图1是本发明示意图。Figure 1 is a schematic diagram of the present invention.
图中，1.激光器，2.分束器，3.凸透镜I，4.光电探测器，5.锁相放大器，6.棱镜偏振器，7.凸透镜II，8.保偏光纤I，9.电光调制器，10.保偏光纤II，11.凸透镜III，12. 波片I，13.透镜台，14.原子力显微镜，15.探针，16.样品，17.磁铁，18.样品台，19.信号发生器，20.示波器，21.波片II，22.凸透镜IV，23.平面镜。Among the figure, 1. Laser, 2. Beam splitter, 3. Convex lens I, 4. Photodetector, 5. Lock-in amplifier, 6. Prism polarizer, 7. Convex lens II, 8. Polarization maintaining fiber I, 9. Electro-optic modulator, 10. Polarization maintaining fiber II, 11. Convex lens III, 12. Wave plate I, 13. Lens stage, 14. Atomic force microscope, 15. Probe, 16. Sample, 17. Magnet, 18. Sample stage, 19. Signal generator, 20. Oscilloscope, 21. Waveplate II, 22. Convex lens IV, 23. Plane mirror.
具体实施方式Detailed ways
如图1是本发明示意图，左下角具有xyz三维方向标，xyz为空间直角坐标系、xy平面为水平面，zx平面与水平面垂直，所述一种纳米结构磁性测量装置主要包括激光器1、分束器2、凸透镜I 3、光电探测器4、锁相放大器5、棱镜偏振器6、凸透镜II 7、保偏光纤I 8、电光调制器9、保偏光纤II 10、凸透镜III11、波片I 12、透镜台13、原子力显微镜14、探针 15、样品16、磁铁17、样品台18、信号发生器19、示波器20、波片II21、凸透镜IV22、平面镜23，激光器1的波长在400纳米到800纳米范围可调，原子力显微镜14位于透镜台13 下方，探针15位于原子力显微镜14下方，所述探针15为原子力显微镜探针且为圆台形状，所述圆台的上底面直径为3微米、下底面直径为1.5微米，所述圆台轴线方向与水平面垂直，样品16、磁铁17及样品台18依次位于探针15的正下方，波片I 12为半波片，波片II21为 1/4波片，所述探针15中具有通孔I和通孔II，所述通孔I、通孔II的轴线和探针15圆台的轴线均位于zx平面内，所述通孔I和通孔II的轴线分别位于探针15圆台轴线的两侧、且均与所述探针15圆台轴线成45度角，光电探测器4与锁相放大器5电缆连接，信号发生器 19、示波器20分别电缆连接样品台18，保偏光纤I 8具有慢轴和快轴，棱镜偏振器6的透射轴与保偏光纤I 8的慢轴平行，保偏光纤I 8的慢轴位于电光调制器9的横磁轴和横电轴之间夹角的角平分线上，电光调制器9的横磁轴与保偏光纤II 10的慢轴平行，所述探针15中的通孔I和通孔II的直径均为200纳米，所述保偏光纤I 8长度为2米，所述保偏光纤II 10长度为9米。激光器1发出的光依次经过分束器2、棱镜偏振器6、凸透镜II7、保偏光纤I 8 后，进入电光调制器9，光在电光调制器9中形成两个正交的偏振分量为面内偏振和面外偏振，且每个分量加上相位φ(t)＝φ0cos(ωt)，两个光分量的相位时间差为τ，光束从电光调制器9出来后进入保偏光纤II10，光的两个正交的偏振分量分别沿保偏光纤II 10的快轴和慢轴传输，光离开保偏光纤II10后，依次通过凸透镜III11、波片I 12、透镜台13、原子力显微镜 14、通孔I到达样品16表面，并第一次被反射，第一次反射光依次经过通孔II、原子力显微镜14、透镜台13、波片II21、凸透镜IV22到达平面镜23，并第二次被反射，第二次反射光依次经过凸透镜IV22、波片II 21、透镜台13、原子力显微镜14、通孔II到达样品表面，并第三次被样品16表面反射，第三次反射光依次经过通孔I、原子力显微镜14、透镜台13、波片I 12、凸透镜III11、保偏光纤II 10、电光调制器9、保偏光纤I 8、凸透镜II7、棱镜偏振器6，再被分束器2偏转后，经过凸透镜I 3进入光电探测器4，第三次反射光的两个偏振分量在光电探测器4处发生干涉，分别沿保偏光纤II 10的慢轴和快轴传输的光的两个正交偏振分量，从保偏光纤II 10输出后对应的琼斯矩阵分别表示为和在经过波片I 12 后，所述光的两个正交偏振分量对应的琼斯矩阵转变为和其中 为相位角，定义为表示光束在经过样品表面的两次反射后回到电光调制器9的整个过程的琼斯矩阵，光电探测器4中得到的光的两个正交偏振分量的相位差表示为相位差在x、y、z方向的分量分别为αx、αy、αz，对光电探测器4中得到的光电流进行傅里叶分析，锁相放大器5得到光电流的一阶谐波分量：和二阶谐波分量：考虑对称性，αk简化为其中ω是电光调制器9的时间依赖的相位φ(t)的角频率，Iinc是激光器发射的光的光强，γ为光束两次经过下列光学元件分束器2、棱镜偏振器6、凸透镜II 7、保偏光纤I 8、电光调制器9、保偏光纤II 10、凸透镜III11、凸透镜IV22，并被样品16表面反射两次后光强的剩余比例，J1和J2分别是一阶和二阶是贝塞尔方程，αk是样品磁化分量的线性方程，x、y、z方向的样品磁化分量mx、my、mz对αk的贡献取决于样品的反射系数、光路中的光学元件等。Fig. 1 is a schematic diagram of the present invention, the lower left corner has an xyz three-dimensional direction mark, xyz is a space Cartesian coordinate system, the xy plane is a horizontal plane, and the zx plane is perpendicular to the horizontal plane. Device 2, convex lens I 3, photodetector 4, lock-in amplifier 5, prism polarizer 6, convex lens II 7, polarization maintaining fiber I 8, electro-optic modulator 9, polarization maintaining fiber II 10, convex lens III 11, wave plate I 12 , lens stage 13, atomic force microscope 14, probe 15, sample 16, magnet 17, sample stage 18, signal generator 19, oscilloscope 20, wave plate II21, convex lens IV22, plane mirror 23, the wavelength of laser 1 is in 400 nanometers to 800 The nanometer range is adjustable, the atomic force microscope 14 is positioned under the lens stand 13, and the probe 15 is positioned under the atomic force microscope 14. The probe 15 is an atomic force microscope probe and is in the shape of a circular truncated cone. The diameter of the bottom surface is 1.5 microns, the axial direction of the circular platform is perpendicular to the horizontal plane, the sample 16, the magnet 17 and the sample stage 18 are located directly below the probe 15, the wave plate I 12 is a half wave plate, and the wave plate II21 is a 1/4 wave plate sheet, the probe 15 has a through hole I and a through hole II, the axes of the through hole I, the through hole II and the axis of the probe 15 circular platform are all located in the zx plane, the through hole I and the through hole II The axes of are respectively located on both sides of the axis of the probe 15 round table, and all form an angle of 45 degrees with the axis of the round table of the probe 15. The photodetector 4 is connected with the lock-in amplifier 5 cables, and the signal generator 19 and the oscilloscope 20 are connected with cables respectively. Sample stage 18, polarization maintaining fiber I 8 has a slow axis and a fast axis, the transmission axis of prism polarizer 6 is parallel to the slow axis of polarization maintaining fiber I 8, and the slow axis of polarization maintaining fiber I 8 is located at the transverse magnetic field of electro-optic modulator 9 On the angle bisector of the angle between the axis and the transverse electric axis, the transverse magnetic axis of the electro-optic modulator 9 is parallel to the slow axis of the polarization-maintaining fiber II 10, and the diameters of the through hole I and the through hole II in the probe 15 Both are 200 nanometers, the length of the polarization-maintaining fiber I 8 is 2 meters, and the length of the polarization-maintaining fiber II 10 is 9 meters. The light emitted by the laser 1 passes through the beam splitter 2, the prism polarizer 6, the convex lens II7, and the polarization-maintaining fiber I 8 in sequence, and then enters the electro-optic modulator 9, where the light forms two orthogonal polarization components as plane In-plane polarization and out-of-plane polarization, and each component adds phase φ(t)= φ0 cos(ωt), the phase time difference of the two light components is τ, and the light beam enters the polarization-maintaining fiber II10 after coming out of the electro-optic modulator 9, The two orthogonal polarization components of the light are respectively transmitted along the fast axis and the slow axis of the polarization maintaining fiber II 10. After the light leaves the polarization maintaining fiber II10, it passes through the convex lens III11, wave plate I12, lens stage 13, atomic force microscope 14, The through hole I reaches the surface of the sample 16 and is reflected for the first time. The first reflected light passes through the through hole II, the atomic force microscope 14, the lens stage 13, the wave plate II21, and the convex lens IV22 to the plane mirror 23 and is reflected for the second time. , the second reflected light passes through the convex lens IV22, the wave plate II 21, the lens stage 13, the atomic force microscope 14, and the through hole II to reach the sample surface, and is reflected by the surface of the sample 16 for the third time, and the third reflected light passes through the through hole in turn I, atomic force microscope 14, lens stand 13, wave plate I 12, convex lens III11, polarization maintaining fiber II 10, electro-optic modulator 9, polarization maintaining fiber I 8, convex lens II7, prism polarizer 6, and then deflected by beam splitter 2 Finally, it enters the photodetector 4 through the convex lens I3, and the two polarization components of the reflected light for the third time interfere at the photodetector 4, and two of the light transmitted along the slow axis and the fast axis of the polarization maintaining fiber II Orthogonal polarization components, the corresponding Jones matrices after output from the polarization maintaining fiber II 10 are expressed as and After passing through the wave plate I 12 , the Jones matrix corresponding to the two orthogonal polarization components of the light is transformed into and in is the phase angle, defined as To represent the Jones matrix of the whole process of the light beam returning to the electro-optic modulator 9 after two reflections on the sample surface, the phase difference of the two orthogonal polarization components of the light obtained in the photodetector 4 is expressed as The components of the phase difference in the x, y, and z directions are α x , α y , and α z , respectively. Fourier analysis is performed on the photocurrent obtained in the photodetector 4, and the lock-in amplifier 5 obtains the first-order harmonic of the photocurrent Portion: and second harmonic components: Considering the symmetry, α k simplifies to Where ω is the angular frequency of the time-dependent phase φ(t) of the electro-optic modulator 9, I inc is the light intensity of the light emitted by the laser, and γ is the light beam passing through the following optical elements beam splitter 2, prism polarizer 6, Convex lens II 7, polarization-maintaining fiber I 8, electro-optic modulator 9, polarization-maintaining fiber II 10, convex lens III11, convex lens IV22, and the remaining ratio of the light intensity after being reflected twice by the surface of the sample 16, J 1 and J 2 are respectively The first and second order are Bessel equations, α k is the linear equation of the sample magnetization component, and the contribution of the sample magnetization components m x , m y , m z in the x, y , and z directions to α k depends on The reflection coefficient of the sample, the optical elements in the light path, etc.
极向克尔效应对应于磁化的z方向的分量，纵向克尔效应对应于磁化的y方向的分量，横向克尔效应对应于磁化的x方向的分量，由于样品磁化分量在不同的晶体对称操作下的转变不同，应该选择合适的P1和P2以及光路中的光学元件，以使得极向或纵向或横向磁光克尔效应的贡献占主要部分。The polar Kerr effect corresponds to the z-direction component of the magnetization, the longitudinal Kerr effect corresponds to the y-direction component of the magnetization, and the transverse Kerr effect corresponds to the x-direction component of the magnetization, since the sample magnetization components operate symmetrically in different crystals The transformation under different conditions should choose the appropriate P 1 and P 2 and the optical elements in the optical path so that the contribution of the polar or longitudinal or transverse magneto-optical Kerr effect accounts for the main part.
本发明装置采用具有通孔的原子力显微镜探针，能够得到样品表面纳米尺度结构的磁化信息，其次，本发明采用同一束光的两个正交偏振分量干涉的方法来获得样品表面的磁化信息，两个偏振光分量共用一个光路，避免光束分离和重新汇集，能够相对较容易地保证两个光束以同样的光路传播，并减少光路中的光学元件，使得信号较少地受样品以及干涉环路中光学元件的移动影响，提高了信噪比，另外，本发明装置通过采用斜入射的光束，能够实现在无需对装置中光路做较大改变的情况下，测量克尔效应的纵向、横向和极向三个分量。The device of the present invention adopts an atomic force microscope probe with a through hole, which can obtain the magnetization information of the nanoscale structure of the sample surface. Secondly, the present invention uses the interference method of two orthogonal polarization components of the same beam of light to obtain the magnetization information of the sample surface. The two polarized light components share one optical path, avoiding beam separation and recombination, it is relatively easy to ensure that the two beams propagate in the same optical path, and reduce the optical components in the optical path, so that the signal is less affected by the sample and the interference loop Influenced by the movement of the optical elements in the device, the signal-to-noise ratio is improved. In addition, the device of the present invention can measure the longitudinal, lateral and Pole to three components.
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| CN116500523B (en) * | 2023-06-21 | 2023-10-20 | 赫智科技(苏州)有限公司 | Mode switching device for magneto-optical Kerr measurement and magneto-optical Kerr measurement device |
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