Transmission electron microscope sample rod system with optical focusing and focal spot continuous scanning
Technical Field
The invention relates to the technical field of accessories of transmission electron microscopes, in particular to a sample rod system of a transmission electron microscope with optical focusing and focal spot continuous scanning.
Background
In recent decades, the development of transmission electron microscopy has advanced the material structure characterization capabilities to the atomic scale, and can characterize electronic structures at the atomic scale. However, the traditional commercial electron microscope has single function except the structural representation capability, and the physical properties of materials cannot be directly researched, so that the research in the field of in-situ electron microscopes is promoted. In-situ electron microscope research is aimed at researching the properties of materials such as force, heat, electricity, light and the like in situ in a transmission electron microscope by introducing signal excitation such as mechanics, thermal, electricity or optics and the like into a transmission electron microscope cavity so as to directly relate the structure and physical properties of the materials. Optical technology is a very important effective means for studying physical properties of materials, for example, spectroscopy technology can study the interaction between light and materials through the spectral response of materials, and the development of ultrafast spectroscopy also improves the time detection resolution of spectroscopy technology to the order of femtoseconds, so that the ultrafast kinetic processes of material electrons or excitons and the like can be further studied. It would therefore be of great importance, both in terms of basic scientific research and in terms of application technology, if optical signals could be introduced in situ in the transmission electron mirror for establishing a direct connection between the microstructure and the properties of the material.
Disclosure of Invention
Therefore, the present invention is directed to overcoming the drawbacks of the prior art and providing a sample rod system for a transmission electron microscope with optical focusing and continuous focal spot scanning.
To achieve the above object, a first aspect of the present invention provides a transmission electron microscope sample rod system comprising: the device comprises a laser, a reflector, a first beam splitter prism, a microscope objective, a sample rod provided with an optical fiber and a 4f zooming system, a light source, a first lens, a second beam splitter prism, a second lens and an image acquisition device;
the 4f zooming system consists of two small-caliber lenses.
The system according to the first aspect of the present invention, wherein the aperture of the small-aperture lens of the 4f zoom system is 2mm to 8mm, preferably 5mm to 6.25 mm;
preferably, the sample rod is vacuum sealed by the small-bore lens.
The system according to the first aspect of the present invention, wherein the laser is selected from one or more of: continuous optical semiconductor laser, ultrafast pulse laser, solid laser, gas laser, and optical fiber coupled laser.
The system according to the first aspect of the present invention, wherein the optical fiber in the sample rod in which the optical fiber and the 4f zoom system are installed is a single mode or few mode optical fiber at the operating wavelength, or the optical fiber is a fiber bundle composed of single mode or few mode optical fibers.
The system according to the first aspect of the present invention, wherein the laser of the system is followed by a beam expanding collimator.
The system according to the first aspect of the present invention, wherein when the laser needs to perform pulse compensation, two turning mirrors and a dispersion compensation element are further disposed behind the beam expanding collimator;
preferably, the dispersion compensating element comprises a pair of parallel placed gratings and a mirror.
The system according to the first aspect of the present invention, wherein the sample rod with the optical fiber and the 4f zoom system mounted thereon further comprises:
the near end of the optical fiber is fixed on the three-dimensional displacement table;
a front end;
a sample-carrying clamp;
the piezoelectric ceramic tube is used for accurately adjusting the position of a focusing light spot in a plane perpendicular to the light propagation direction;
a centering device; and
a differential micrometer head that adjusts a focal plane of the laser in a beam propagation direction.
The system according to the first aspect of the present invention, wherein the system further comprises a secondary optical imaging system through which the focused spot produced when the sample rod is free of the mounted front tip and sample-carrying grip is observed.
The system according to the first aspect of the present invention, wherein the light source is selected from a white light source or a light emitting diode.
A second aspect of the invention provides a transmission electron microscope comprising a transmission electron microscope sample rod system as described in the first aspect.
The technology aims to solve the problems that the existing transmission electron microscope technology does not have physical property analysis capability and cannot be effectively combined with the optical characterization technology, and the focused optical signal is introduced into the transmission electron microscope, so that conditions are created for in-situ research on the microstructure and physical properties of the material in the transmission electron microscope.
The idea of the invention is that: the transmission electron microscope sample rod system with the optical confocal function is realized by mounting a single-mode or few-mode optical fiber or a 4f system consisting of a fiber bundle consisting of a large number of single-mode or few-mode optical fibers and two small-caliber lenses on a sample rod, and is used for introducing a focused optical signal into a transmission electron microscope. Firstly, expanding and collimating laser emitted by a laser, then coupling a collimated light beam into an optical fiber arranged on a sample rod from an optical fiber end surface positioned outside a transmission electron microscope, and enabling the light beam emitted from the optical fiber end surface inside the sample rod to pass through two small-caliber lenses to form a 2: the 4f zooming system of the 1 focuses on the sample chamber, and the position of a focusing light spot can be adjusted through a piezoelectric ceramic tube and a micro-measuring head, so that the transmission electron microscope sample rod system with optical focusing and focusing scanning is realized. When the laser is a femtosecond laser, in order to compensate pulse broadening caused by the optical fiber, firstly, the femtosecond pulse light is reversely broadened by using a dispersion compensation element, and then, the femtosecond pulse light is coupled into the optical fiber, so that the focused femtosecond pulse light is introduced into a transmission electron microscope.
A transmission electron microscope sample rod system with optical focusing and focused scanning, characterized by the steps of:
step 1: laser emitted by the laser is expanded and collimated at first, and by means of a white light reflection imaging system, a collimated light beam is coupled into a fiber core of an optical fiber from the near end of the optical fiber through a microscope objective, and finally, the light beam emitted from the far end of the optical fiber passes through a light source 2: 1, the 4f zoom system generates a focused light spot;
step 2: the piezoelectric ceramic tube is used for electrically adjusting the far end of the optical fiber, so that the focusing light spot generated in the step 1 can be accurately adjusted in a two-dimensional plane, and in addition, the differential micrometer head is used for manually adjusting the far end of the optical fiber out of the plane, so that the focusing plane of the focusing light spot is adjusted;
the transmission electron microscope sample rod system of the present invention may have the following beneficial effects, but is not limited to:
the invention provides a transmission electron microscope sample rod system with optical focusing and continuous scanning, which can introduce focused continuous light and ultrafast pulse light into a transmission electron microscope by utilizing a sample rod provided with an optical fiber and a small-caliber lens, and can realize the scanning of a focused light spot in a limited three-dimensional space, so that the in-situ research of material properties in the transmission electron microscope becomes possible.
Drawings
Embodiments of the invention are described in detail below with reference to the attached drawing figures, wherein:
FIG. 1 shows a schematic diagram of a TEM sample rod system with optical focusing and continuous scanning according to the present invention.
FIG. 2 shows a detailed view of the sample rod portion with the optical fiber mounted.
FIG. 3 shows the result of optical focusing of a beam exiting the distal end of an optical fiber by a 4f zoom system; wherein, fig. 3(a) shows an intensity map of a focused spot recorded by the auxiliary optical imaging system, and fig. 3(b) shows an intensity distribution of the focused spot in a horizontal direction.
Fig. 4 shows the intensity distribution after superposition of the focused spots for continuous scanning with a piezo-ceramic tube.
Description of reference numerals:
1. a laser; 2. a beam expanding collimator; 3. a first flip mirror; 4. a dispersion compensating element; 5. a second flipping mirror; 6. a mirror; 7. a first beam splitting prism; 8. a microscope objective; 9. a sample rod mounted with an optical fiber; 10. a white light source; 11. a first lens; 12. a second beam splitting prism; 13. a second lens; 14. an image acquisition device; 15. an auxiliary optical imaging system; 16. a front end; 17. a sample-carrying clamp; 18. a first small-caliber lens; 19. a second small-caliber lens; 20. an optical fiber mounted to the sample rod; 21. a piezoelectric ceramic tube; 22. a centering device; 23. and a differential micrometer head.
Detailed Description
The invention is further illustrated by the following specific examples, which, however, are to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever.
This section generally describes the materials used in the testing of the present invention, as well as the testing methods. Although many materials and methods of operation are known in the art for the purpose of carrying out the invention, the invention is nevertheless described herein in as detail as possible. It will be apparent to those skilled in the art that the materials and methods of operation used in the present invention are well within the skill of the art, provided that they are not specifically illustrated.
Example 1
This example illustrates the structure of a transmission electron microscope sample rod system according to the present invention.
The present invention relates to a transmission electron microscope sample rod system with optical focusing and scanning, as shown in fig. 1, comprising: the device comprises a laser 1, a beam expanding collimator 2, a first turnover reflector 3, a dispersion compensation element 4, a second turnover reflector 5, a reflector 6, a first beam splitter prism 7, a microscope objective 8, a sample rod 9 provided with optical fibers, a white light source 10, a first lens 11, a second beam splitter prism 12, a second lens 13, an image acquisition device 14 and an auxiliary optical imaging system 15.
The detailed information of the sample rod part with the optical fiber is shown in figure 2, and comprises a front end head 16, a sample bearing clamp 17, a first small-caliber lens 18, a second small-caliber lens 19, the optical fiber 20 arranged on the sample rod, a piezoelectric ceramic tube 21, a centering device 22 and a differential micrometer head 23.
As shown in fig. 1, taking a femtosecond pulse laser as an example for specific description, a femtosecond pulse light emitted from a laser 1 (with a wavelength of 800nm) is first converted into quasi-parallel light by a beam-expanding collimator 2, then reflected by a first turning mirror 3 and then irradiated to a dispersion compensation element 4 (including a parallel-arranged grating pair and a mirror) to expand the pulse, and the expanded pulse light is first reflected by a second turning mirror 5. It should be noted here that when pulse width compensation is not required or a continuous laser is used, the first flip mirror 3 and the second flip mirror 5 are moved out of the optical path system by rotating 90 °. The propagation direction of the pulse light reflected by the second turnover reflector 5 is the same as that before the pulse light is reflected by the first turnover reflector 3, then the pulse light is reflected by the first reflector 6 and the first beam splitter prism 7, and is focused on the near end of the optical fiber 20 arranged on the sample rod through the microscope objective 8, wherein the near end of the optical fiber is fixed on a three-dimensional displacement table, and the pulse light after being reflected by the end face is firstly collected through the microscope objective 8, then is reflected by the first beam splitter prism 7 and the second beam splitter prism 12, and finally reaches the target surface of the collecting device 14 through the second lens 13; in the white light imaging system, white light emitted by a white light source 10 sequentially passes through a first lens 11, a second beam splitter prism 12 and a second beam splitter prism 7, then reaches a back focal plane of a microscope objective 8, is focused by the microscope objective 8 and then irradiates the near end of an optical fiber 20 arranged on a sample rod, the path of the pulse light reflected by the end face is the same as that of the pulse light, and the white light reflected by the end face passes through the microscope objective 8, the first beam splitter prism 7, the second beam splitter prism 12 and the second lens 13 and finally reaches the target surface of an image acquisition device 14. The proximal end of the fiber 20 mounted to the sample rod is adjusted in the z-direction to enable the end face to be imaged clearly onto the target surface of the image capture device 14, the proximal end of the fiber 20 mounted to the sample rod is adjusted in the xy-direction, and the focused pulsed light is coupled into the core of the fiber 20 mounted to the sample rod according to the image captured in real time by the image capture device 14. In order to achieve focusing of a spot of size less than 2 μm on the sample-holding jig 17, the light beam exiting at the distal end of the optical fiber passes through a sample-holder-mounted optical fiber 20 composed of a second small-caliber lens 19 (diameter: 6.25mm, focal length: 15mm, numerical aperture: 0.21) and a first small-caliber lens 18 (diameter: 6.25mm, focal length: 7.5mm, numerical aperture: 0.42) according to the parameters (core diameter: about 3.5 μm and numerical aperture: about 0.35) of the optical fiber 2: 1, 4f scaling system. In the present embodiment, when the guaranteed numerical aperture of the first small-caliber lens 18 is not smaller than the numerical aperture of the used optical fiber and the laser utilization efficiency is maximized, according to the commercially available small-caliber lens, 2: the 4f scaling system of 1 achieves a focused spot size of less than 2 μm. When the front tip 16 of the sample rod 9 and the sample-carrying clamp 17 are not mounted, the resulting focused light spot can be observed by the auxiliary optical imaging system 15, as shown in fig. 3 (a). The spot size as measured by the intensity distribution of the recorded focused spot in the horizontal direction was 1.6 microns as shown in fig. 3 (b). In addition, the piezoelectric ceramic tube 21 can be used to precisely adjust the translation of the distal end of the optical fiber 20 in the plane, the piezoelectric ceramic tube 21 after voltage calibration is used to adjust the distal end of the optical fiber in the plane with the scanning step of 1 μm, the auxiliary optical imaging system 15 can observe the movement of the focused light spots in the plane in real time, and the intensity distribution of the continuously scanned focused light spots after superposition is shown in fig. 4. The differential micrometer head 23 can also move the distal end of the optical fiber 20 in the beam propagation (z) direction, thereby changing the position of the focused spot generated by the 4f zoom system, and realizing the adjustment of the focal plane of the spot.
Example 2
This example illustrates the method of using a transmission electron microscope sample rod system in accordance with the present invention.
The specific implementation steps are as follows:
step 1: the horizontal polarized light emitted by the laser 1 is firstly converted into parallel light by the beam expanding collimator 2;
step 2: focusing the parallel light obtained in the step (1) on the near end of an optical fiber arranged in a sample rod through a microscope objective 8;
and step 3: irradiating the whole end face of the near end of the optical fiber by a white light source 10 through a lens and a microscope objective 8;
and 4, step 4: adjusting the near end of the optical fiber in the z direction, and imaging the white light reflected in the step (3) to an image acquisition device;
and 5: adjusting the near end of the optical fiber in the xy direction by means of the optical fiber end face image obtained in the step 4, and accurately coupling the focused light in the step 2 into the fiber core of the optical fiber;
step 6: the laser coupled into the optical fiber in the step 5 is processed by a step 2 consisting of a second small-caliber lens 19 and a first small-caliber lens 18 with focal lengths of 15mm and 7.5mm at the far end of the optical fiber: 1, the 4f zoom system focuses on the sample chamber;
and 7: the focused light spot produced by step 6 can be adjusted in-plane by a piezo ceramic tube and out-of-plane by a differential micrometer head.
Although the present invention has been described to a certain extent, it is apparent that appropriate changes in the respective conditions may be made without departing from the spirit and scope of the present invention. It is to be understood that the invention is not limited to the described embodiments, but is to be accorded the scope consistent with the claims, including equivalents of each element described.