Laser introduction device for electron gun and ultrafast scanning electron microscope comprising same

Abstract

The application provides a laser introduction device for introducing pulsed laser into an electron gun, wherein the electron gun comprises a main body with a cavity, an anode cap, an electron gun filament arranged on a top wall of the main body, and a grid cap surrounding the electron gun filament and having a grid cap hole; a side wall of the main body has a first window, a bottom wall of the main body has a first exit hole or passage arranged opposite to the grid cap hole, and the anode cap is arranged on the first exit hole; the laser introduction device comprises: a reflection assembly arranged in the main body; a reflecting device arranged on a top surface of the anode cap to face the grid cap, and the reflection assembly is configured such that pulsed laser incident from the first window and guided through the reflection assembly can be reflected by the reflecting device to irradiate the electron gun filament through the grid cap hole. The laser introduction device according to the application can introduce an ultrafast light source into an existing scanning electron microscope at a better incident angle, eliminate electric field distortion, and has lower cost and higher detection performance and application range.

Description

Technical Field

[0001] This invention relates to the field of microscopic material detection and imaging, and more specifically to a laser introduction device for an electron gun and an ultrafast scanning electron microscope including the same. Background Technology

[0002] A scanning electron microscope (SEM) allows the observation and characterization of the three-dimensional properties of various materials at spatial scales ranging from micrometers (μm) to nanometers (nm). Its electron gun generates a focused electron beam that scans the sample surface. The interaction between the electron beam and the material excites various physical signals. These signals are collected, amplified, and re-imaged to characterize the microscopic morphology and chemical composition of the material.

[0003] A current research focus in this field is combining scanning electron microscopes (SEMs) and ultrafast lasers using a pump-probe approach to create ultrafast SEMs with temporal analysis capabilities, capable of capturing the dynamic processes of surface charge carriers under pump excitation. Compared to conventional SEMs using thermionic or field-emission (including cold-field, hot-field, and Schottky) modes, ultrafast SEMs primarily generate probe electrons by using femtosecond-level ultrafast lasers to irradiate the electron gun filament cathode, producing pulsed photoelectrons. The temporal broadening of these pulsed photoelectrons determines the temporal resolution. The time delay between these pulsed photoelectrons and the pump laser introduced to the sample enables the temporal resolution capability of the ultrafast SEM.

[0004] Since conventional scanning electron microscopes on the market only focus on the basic function of static imaging of samples through electrons, they do not currently have the need to be combined with ultrafast lasers. Therefore, they will not consider adding a window for laser settings, thus limiting their potential for expansion.

[0005] Figure 1 A simplified schematic diagram of the electron gun in a prior art scanning electron microscope is shown, illustrating the femtosecond laser pathway. Figure 1 The diagram shows a cross-section and internal layout of the remaining half after the electron gun 1 is cut in half. The electron gun 1 has a cylindrical cavity 10. Inside the cavity, at opposite positions along the central axis A1 of the cylindrical cavity, are an electron gun cathode 11 and an emission port 12. The electron gun cathode 11 has a thermal field emission electron gun filament 14 at its conical tip. The electron gun cathode 11 is covered with a grid cap (not shown for the purpose of showing the electron gun cathode 11). An anode cap (not shown for the purpose of showing the emission port 12) is also covered above the emission port 12. A filament temperature measurement window 13 is provided on the side wall of the cylindrical housing 10.

[0006] In this arrangement of the prior art, in order to ensure that the ultrafast laser introduced from the filament temperature measurement window 13 can precisely irradiate the thermal field emission electron gun filament 14, the ultrafast laser source, the filament temperature measurement window 13, and the thermal field emission electron gun filament 14 must be aligned on a horizontal straight line, and a corresponding through hole needs to be drilled outside the gate cap hole on the gate cap outside the electron gun cathode 11. After having such a lateral light channel, the thermal field emission electron gun filament 14, irradiated by the ultrafast laser, generates pulsed electrons. These electrons move along the central axis A1 under the action of an external electric field, that is, they are emitted out of the emission hole 12 along the cap hole.

[0007] However, the above scheme has the following drawbacks: First, the premise for this scheme is that the scanning electron microscope must have a temperature measurement window in a suitable position, which is just enough to allow the externally introduced laser to irradiate the tip of the filament in a horizontal direction. However, most existing scanning electron microscopes do not have such a suitable temperature measurement window, thus limiting their application range. Second, in this arrangement, the filament temperature measurement window 13 is located on the side wall almost flush with the conical tip of the filament 11. The femtosecond laser can only directly irradiate the thermal emission electron gun filament from the side. The angle between the irradiation direction and the target emission direction of the excited electrons is too large, resulting in low electron excitation efficiency. At the same time, for a thermal emission scanning electron microscope, even if a suitable temperature measurement window is available, an additional lateral entrance hole for light to pass through is required on the shell-shaped grid cap covering the cathode filament 11. This will cause the grid electric field symmetry to be destroyed, causing the electron motion to deviate from the electron gun optical axis and potentially generating harmful X-rays. Summary of the Invention

[0008] To address the aforementioned deficiencies in existing scanning electron microscopes, a first aspect of the present invention provides a laser introduction device for introducing pulsed laser light into an electron gun. The electron gun includes a body with a cavity, an anode cap, an electron gun filament disposed on the inner top wall of the body, and a grid cap surrounding the electron gun filament and having a grid cap aperture. The body has a first window on its side wall and a first exit aperture disposed on its bottom wall opposite the grid cap aperture. The anode cap is disposed on the first exit aperture.

[0009] The laser introduction device includes:

[0010] A reflective assembly arranged within the main body;

[0011] A reflective device is arranged on the top surface of the anode cap so as to face the gate cap.

[0012] The reflective component is configured such that pulsed laser light incident from the first window and guided by the reflective component can be reflected by the reflective device to pass through the gate cap aperture and illuminate the electron gun filament.

[0013] Preferably, the reflective component includes:

[0014] A first and second reflecting mirror having relatively parallel axes of rotation, and

[0015] A support assembly for the mirror, which arranges the first and second mirrors at intervals relative to each other.

[0016] Preferably, the lens support assembly includes a long strip-shaped first lens support portion, a second lens support portion, and a connecting portion, as well as two long strip-shaped support portions arranged opposite to each other, wherein...

[0017] The first reflector is disposed on the first mirror holder, and the second reflector is disposed on the second mirror holder. The first and second mirror holders are arranged parallel to each other between the two support portions and are capable of rotating along their respective length axes to form the rotation axes of the first and second reflectors; and

[0018] The connecting part is fixedly connected between the two support parts, and the first lens holder part is arranged between the second lens holder part and the connecting part.

[0019] Preferably, each of the two support portions has a hollow groove extending along the length direction, and each of the first and second lens holder portions extends through the two hollow grooves so that it can slide or rotate along the two hollow grooves, and is fixed from the outside of the two hollow grooves by bolt components.

[0020] Preferably, the support lens assembly is made of a conductive material to guide electrons accumulated on the surface of the reflective assembly out of the electron gun.

[0021] Preferably, the laser introduction device further includes at least one mating lens holder assembly, which has the same shape and material as the supporting lens holder assembly and is arranged relatively dispersedly on the bottom wall around the anode cap.

[0022] Preferably, the arrangement of the at least one mating lens holder assembly and the supporting lens holder assembly is axially symmetrical with respect to the axial direction of the gate cap hole pointing towards the first emission hole.

[0023] Preferably, the reflective device is a thin circular layer with a central through-hole, and its surface area is large enough that the pulsed laser light incident from the first window can be reflected by the outer edge of the reflective device and enter the gate cap aperture to irradiate the electron gun filament.

[0024] The reflective device and the anode cap are integrally formed.

[0025] Preferably, the pulsed laser can enter the gate cap hole at a predetermined small angle relative to the axis direction of the gate cap hole pointing towards the first emission hole and irradiate the electron gun filament, the predetermined small angle being in the range of 10° to 45°.

[0026] Preferably, the sidewalls of the electron gun are configured to be detachably connected, for example, the top wall of the electron gun is similar to a cap, which can be detached from the cup-shaped remaining part of the electron gun (the sidewalls and bottom walls are formed as one piece). The laser introduction device also includes a tubular extension that can engage with the detached sidewalls of the electron gun to form a complete sidewall and seal it with the cap-shaped top wall.

[0027] Preferably, the mirror support assembly controls the translation or rotation of the reflective assembly via a microelectromechanical system.

[0028] Another aspect of the present invention provides a scanning electron microscope having an ultrafast laser source, which further includes a laser introduction device as described in any of the above embodiments for introducing the pulsed laser generated by the ultrafast laser source into its electron gun.

[0029] Compared to existing technologies, the laser introduction device according to embodiments of the present invention can introduce an ultrafast light source into an existing scanning electron microscope at a smaller incident angle. Its arrangement is flexible and can eliminate electric field distortion, enabling scanning electron microscopes that do not have an ultrafast light source in the prior art to be upgraded quickly at extremely low cost and easy to maintain, with lower cost and higher detection performance and applicability. Attached Figure Description

[0030] The embodiments of the present invention will be further described below with reference to the accompanying drawings, wherein:

[0031] Figure 1 This is a simplified schematic diagram of the electron gun in a scanning electron microscope (SEM) that generates femtosecond lasers in the prior art.

[0032] Figure 2 This is a schematic diagram viewed from the side of a laser introduction device according to a preferred embodiment of the present invention;

[0033] Figure 3 yes Figure 2 The top view corresponding to the side view of the laser introduction device shown;

[0034] Figure 4 A schematic diagram is shown, viewed from one side of the support frame assembly according to a preferred embodiment of the present invention;

[0035] Figure 5 It shows from and Figure 4 A schematic diagram showing the view from the side perpendicular to the side described above;

[0036] Figure 6 This diagram illustrates a preferred embodiment of the laser introduction device of the present invention introducing a pulsed laser into an electron gun.

[0037] Figure 7 A simplified schematic diagram of an embodiment of the collaboration between an ultrafast laser source, a laser introduction device, and a scanning electron microscope, according to a preferred embodiment of the present invention, is shown. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The structures, proportions, sizes, etc., illustrated in this description are merely for illustrative purposes and to aid those skilled in the art; they do not constitute an undue limitation on the invention and have no technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, provided they do not affect the effects and objectives achieved by the invention, should be included within the scope of the technical content disclosed in this invention.

[0039] Figure 2 This is a schematic diagram of a laser introduction device according to a preferred embodiment of the present invention, viewed from the side. The laser introduction device 20 includes a reflector assembly (a support mirror assembly 21 and a mating mirror assembly 22), a thin-layer reflective portion attached to or coated on the surface of a hollow tubular anode cap 23, a first reflector 24, and a second reflector 25. The laser introduction device 20 is coupled inside the cavity of an electron gun 30, which has a first window 31 and a first emission port 32. The first window 31 can utilize the temperature measuring window on the side wall of an existing electron gun, or it can be formed on the cavity wall of an existing electron gun. Since the laser introduction device 20 has a wide range of optical path angle adjustment, the opening position of the first window 31 is not strictly limited, thus providing good adaptability. The first emission port 32 is an electron emission channel already present in existing electron guns.

[0040] For ease of explanation, Figure 2 The electron gun 30 structure is simplified to a simple cavity-like body with a top wall, a bottom wall, and annular side walls. The electron gun filament is arranged on the top wall inside the body, and its exterior is covered by a grid cap 33. The grid cap has a grid cap hole 34. Its detailed structure will be discussed later. Figure 6 The description continues. The support frame 21 is located near the first window 31 and positioned on the bottom wall of the main body of the electron gun 30; it is roughly a hollow rectangular frame. Figure 2Only one narrower side view is shown, matching the shape of the mirror holder assembly 22 and the supporting mirror holder assembly 21. A first reflecting mirror 24 and a second reflecting mirror 25 are fixed on the supporting mirror holder assembly 21. These mirrors receive laser light incident from the adjacent first window 31 and reflect it onto the polished anode cap surface, and then onto the thermionic electron gun filament inside the grid cap 33 (where the filament is blocked by the outer grid cap 33). The anode cap 23 and the grid cap 33 are arranged opposite each other, forming an axisymmetric accelerating electric field between their opposing end faces. The anode cap 23 is generally a disk shape with a certain thickness, on which a thin layer of highly reflective material, called a reflective part 231, is attached or coated. The reflective part 231 is a circular plane, shaped into a highly reflective end face, and has a through hole 232 extending inward and penetrating the anode cap at its center. The second surface 233, opposite to the circular reflective portion 231, has an anode cap tubular portion 234 that protrudes outward along the disc-shaped second surface 233 by a certain distance. A portion of the hollow interior of the anode cap tubular portion 234 forms a through-hole 232. The outer wall of the anode cap tubular portion 234 has a threaded portion 2341, which couples the anode cap tubular portion 234 to a tube 37 on the bottom wall of the electron gun 30. The tube 37 extends a certain depth from the center of the bottom wall of the electron gun 30 into the cavity. The through-hole on the inner side of the tube 37 forms the first emission port 32, and the through-hole 232 communicates with the first emission port 32. The through-hole 232 of the anode cap 23 is aligned with the first emission port 32. Therefore, in the energized state, electrons within the gate cap 33 are guided by the uniform electric field between the anode cap 23 and the gate cap 33 and emitted through the first emission port 32.

[0041] Figure 3 yes Figure 2 The top view corresponding to the side view of the laser introduction device shown. Figure 3 The electron gun 30 shown is a cylindrical cavity. The support lens assembly 21 and the mating lens assembly 22 of the laser introduction device 20 are each perpendicular to the circular bottom wall of the electron gun 30 and symmetrically distributed on both sides of the center point of the circular bottom wall. The first exit hole 32 and the anode cap 23 are arranged at the center of the circular bottom wall of the electron gun 30. In this embodiment, the reflective part 231 on the top surface of the anode cap is polished to increase its reflectivity to the incident pulsed laser.

[0042] Figure 4 A schematic diagram is shown, viewed from one side of the support frame assembly according to a preferred embodiment of the present invention. Figure 5 It shows from and Figure 4Schematic diagram observed from another side perpendicular to the side. The carrier mirror holder assembly 21 is a rectangular frame structure, which includes a long strip-shaped first bracket 211 and a second bracket 212 arranged opposite and parallel to each other. Between the first bracket 211 and the second bracket 212, a strip-shaped first mirror holder 213, a second mirror holder 214 and a joint part 215 are arranged transversely. The three have threaded holes at both ends along the length direction. Among them, the first mirror holder 213 is used to fix the first mirror 24 and make its reflecting surface face the second mirror holder 214, and the second mirror holder 214 is used to fix the second mirror 25 and make its reflecting surface face the first mirror holder 213. The fixing method between the mirror and the mirror holder can adopt vacuum glue bonding or be fixed by other fixing parts or snap parts and other implementation methods well-known to those skilled in the art. Here, it is not intended to limit it, Figure 4 and Figure 5 shown as bolt connection in and shows multiple bolts 216. The first mirror 24 and the second mirror 25 are coated with an anti-reflection film layer suitable for the frequency domain of the pulsed laser reflected on their respective back surfaces of the reflecting surfaces. The carrier mirror holder assembly 21 is formed of a conductive material and forms a conductive path with the outside to conduct away the electrons that may accumulate on the mirror surface. Among them, a conductive channel can be established between the mirror and the mirror holder by a conductive material, for example, by soldering connection.

[0043] By Figure 5 shown, the first bracket 211 and the second bracket 212 are relatively distributed with long and narrow first hollow grooves 2111 and second hollow grooves 2121 on at least a part of their length directions (the second hollow groove 2121 is blocked in Figure 4 ), and the hollow grooves have suitable sizes so that multiple bolts 216 can pass through the hollow grooves from both sides and fix the first mirror holder 213 and the second mirror holder 214 to the first bracket 211 and the second bracket 212 through their respective threaded holes, forming a rectangular frame structure大致为 Figure 4 shown in the shape of "日". Figure 5 In, the first mirror holder 213 and the second mirror holder 214 are blocked by bolts.

[0044] At the same time, the strip-shaped wholes formed by the first mirror holder 213, the second mirror holder 214 and the bolts 216 at their respective two ends can slide parallel to each other along the first hollow groove 2111 and the second hollow groove 2121 respectively so that the first mirror and the second mirror can approach or move away from each other parallelly to a certain distance and then tighten the bolts to fix at this position, so that the height and spacing of the two mirrors can be easily adjusted; the first mirror holder 213 and the second mirror holder 214 can also be rotated around the axes of their respective length directions to any angle and then tightened by the bolts 216, so that the relative reflection angles between the first or second mirrors can be easily adjusted.

[0045] The first bracket 211 and the second bracket 212 also have threaded holes at their respective ends away from the first hollow groove 2111 and the second hollow groove 2121, so that bolts 216 on both sides pass through the threaded holes to fix the joint 215 to the first bracket 211 and the second bracket 212.

[0046] However, this bolted connection method is merely an example. In other embodiments, other frame structures can be used, as long as the first reflector 24 and the second reflector 25 are arranged opposite each other, allowing them to translate relative to each other to move closer or further apart, or to rotate to adjust the reflection angle. For example, the joint 215 and the first bracket 211 and the second bracket 212 can also be integrally formed, or the support mirror assembly 21 can have a microelectromechanical system (MEMS) to control the respective reflection angles of the first reflector 24 and the second reflector 25, thus enabling control of the femtosecond laser's incident path outside the transmission electron microscope and achieving more precise angle adjustment. The end of the support mirror assembly 21 near the joint 215 is fixed to the circular bottom wall of the electron gun 30, and the fixing method is not limited to adhesive bonding, snap-fit ​​connection, or connection through threaded components.

[0047] The matching mirror support assembly 22 has a similar structure to the supporting mirror support assembly, which will not be described in detail here. However, it is not used as a laser introduction light path, but a reflector can be arranged on it to increase the electric field uniformity in the electron gun cavity.

[0048] Figure 6 A schematic diagram of a laser introduction device according to a preferred embodiment of the present invention is shown, illustrating the introduction of a pulsed laser into an electron gun. The cavity-shaped electron gun 40 mainly includes a first window 41 and a first emission port 42, and a shell-shaped gate cap 43. The electron gun 40 is generally cylindrical and has an axis A2, the axis of which coincides with axis A2. The gate cap 43 has a circular first surface 431, and a gate cap aperture 432 is located at the center of the first surface 431. A thermionic electron gun filament 44 is arranged inside the shell-shaped gate cap 43 near the gate cap aperture 432. The circular bottom wall 45 of the electron gun 40 is parallel to and opposite the first surface 431 of the gate cap, and its central portion has an inwardly protruding tubular extension 451.

[0049] Laser introduction device 20 and Figures 2 to 5The laser introduction device shown is consistent with the one described above. The support mirror assembly 21 and the mating mirror assembly 22 are symmetrically fixed to the circular bottom wall 45 of the electron gun 40 with respect to axis A2. The anode cap 23 is screwed and coupled to the inner side of the tube 37 on the circular bottom wall 45 via its outer threaded portion, so that its internal through hole 232 communicates with the first emission hole 42 to form a continuous channel. The rotational orientation of the first reflector 24 and the second reflector 25, as well as their respective positions along the support mirror assembly 21, are adjusted as needed. When the incident pulsed laser enters through the first window 41 and irradiates the surface of the first reflector 24, it is reflected by the first reflector 24 to the surface of the second reflector 25 and then reflected again to the reflective part 231 of the anode cap 23. The reflective part 231 of the anode cap reflects the pulsed laser into the gate cap hole 432 of the gate cap 43 and irradiates the thermionic electron gun filament 44 within the gate cap hole 432. Typically, the opening size of the gate cap hole 432 is only a few millimeters. However, the laser introduction device 20 according to this embodiment can adjust the incident pulse laser to an incident angle with a very small angle to the normal (i.e., axis A2) of the gate cap hole 432. On the one hand, this enhances the interaction efficiency between the incident pulse laser and the thermionic electron gun filament 44. On the other hand, it eliminates the need for opening holes on the side of the gate cap 43, reducing the potential risk of X-ray leakage.

[0050] like Figure 6 As shown, the main body of the electron gun 40 can be detachable, for example, at a suitable location on the side wall of the main body (e.g., avoiding the temperature measuring window or the first window). In the disassembled electron gun, the first part includes the electron gun cathode filament, the grid cap, and a cap-shaped top; the second part includes the anode cap, side walls, and a cup-shaped portion on the bottom surface. After internal vacuuming, the two parts are pressed together by a rubber sealing ring. Furthermore, a tubular extension 46 (shown by the grid lines) can be added between the two parts. The dimensions of the tubular extension 46 are consistent with the annular side wall of the electron gun 40 to form a complete side wall, so that the first part, the tubular extension, and the second part are coupled to form a complete cavity. Therefore, the internal space of the electron gun 40 is enlarged in a sealed manner, increasing the distance between the grid cap 43 and the anode cap 23, allowing for a wider adjustable range of the incident angle of the laser introduction device 20, and further reducing the incident angle. In another embodiment, the annular side wall portion 46 is not necessary, and the laser introduction device can be directly arranged within the existing electron gun cavity.

[0051] like Figure 6As shown, on the circular bottom wall 45 of the electron gun 40, the support mirror assembly 21 and the mating mirror assembly 22 are symmetrically distributed with respect to the axis A2. The similar shape of the support mirror assembly 21 and the mating mirror assembly 22 makes the electric field distribution inside the electron gun 40 more uniform along the axis A2. Therefore, it can solve the problem that the uniformity of the electric field distribution inside the electron gun 40 is destroyed when there is only a single support mirror assembly 21, which leads to the deviation of the path of the excited electrons from the grid cap to the anode cap.

[0052] The reflective portion 231 on the top surface of the anode cap 23 has a moderately larger top surface area compared to anode caps in the prior art, even though it has a larger radius. Therefore, it can have a larger range of incident light reflection point selection to provide the laser introduction device 20 with a larger range of reflection angle adjustment.

[0053] Figure 7 A simplified schematic diagram of the laser introduction device according to a preferred embodiment of the present invention and the converging optical path after focusing by the convex lens is shown. The ultrafast laser emitted by the convex lens 701 (the laser source is not shown for emphasis) passes horizontally through the first window 741 of the electron gun 740, is reflected sequentially by the first reflector 724, the second reflector 725 and the anode cap 723, and is incident on the thermionic electron gun filament 744 in the grid cap of the electron gun 740. The thermionic electron gun filament 744 interacts with the thermionic electron gun filament 744 to excite pulsed probe electrons. These probe electrons (as opposed to the pump laser below) are emitted through the first exit hole 742 under the action of the accelerating electric field between the grid cap (not shown) and the anode cap 723, pass through the internal optical channel of the scanning electron microscope 703 and are focused on the sample 702. The convex lens 705 introduces the pump laser into the scanning electron microscope 703 to irradiate the sample 702 from another direction and pump it. By controlling the time difference between the irradiation of sample 702 by probe electrons and pump laser, and detecting the various physical signals excited after interaction with the sample, collecting, amplifying and imaging or analyzing these signals, it is possible to accurately characterize the sample's microstructure, chemical composition or the time dimension information of its ultrafast processes.

[0054] In another embodiment, the pulsed laser is incident perpendicularly to the axis A2 onto the first reflector 24, which is a 45° reflector, and the second reflector 25 is a 15° reflector. Therefore, the angle between the pulsed laser reflected by the reflective part 231 of the anode cap and the thermionic electron gun filament 44 and the axis A2 is around 30°, for example, within the incident angle range of 10° to 45°, thereby obtaining better interaction efficiency between the incident pulsed laser and the thermionic electron gun filament 44.

[0055] In another embodiment, multiple fixing parts can be arranged symmetrically with respect to axis A2 inside the electron gun cavity. For example, at least one fixing part has a shape similar to the support mirror assembly (on which two mirrors with the same angle as the first and second mirrors can also be mounted). The spacing between adjacent fixing parts is equal and they are arranged symmetrically about axis A2 on the circular bottom wall inside the electron gun cavity, thereby ensuring that the electric field inside the electron gun cavity is relatively uniformly distributed between the gate cap and the anode cap. This ensures that the excited electrons can move effectively from the gate cap to the anode cap and exit through the first exit hole of the electron gun.

[0056] In another embodiment, this application proposes a method to improve the prior art scanning electron microscope (SEM) so that it can use an ultrafast laser source. The method is for SEMs that do not have a side window (e.g., a temperature measurement window) with an electron gun, or SEMs in which the side window position cannot allow the ultrafast laser to be aligned with the electron gun cathode filament. The laser introduction device 20 or a variation thereof is arranged in the electron gun, and the introduced ultrafast laser is used to irradiate the filament at a minimum working angle to excite pulsed electrons.

[0057] The method includes: firstly, a through-hole first window is opened in the side wall of the electron gun cavity, or the side wall of the electron gun cavity itself already has a first window, wherein the position of the first window does not need to be horizontally aligned with the cathode filament and can be flexibly selected; then, the support mirror assembly 21 of the laser introduction device 20 is arranged in a preferred position inside the electron gun cavity near the first window (e.g., bonded and fixed to the side wall or bottom wall of the electron gun cavity), and a first reflector 24 and a second reflector 25 are installed on it; the original anode cap of the electron gun is replaced with a polished anode cap 23 with a large circular top surface; so that the first reflector 24... 4. The second reflector 25 and the anode cap 23 sequentially form a reflected light path. The rotation angle of the first reflector 24 and the second reflector 25 is adjusted so that the pulsed laser reflected by the anode cap 23 into the electron gun interior arranged opposite to it is incident at the minimum working angle. The matching mirror support assembly 22 or more fixing parts (which have the same shape as the supporting mirror support assembly) are arranged in the cavity of the electron gun so that the at least two fixing parts are symmetrically distributed in the direction from the grid cap to the anode cap (i.e., the electron emission direction) relative to the electron gun, thereby reducing or eliminating the distortion of the electric field between the relative planes of the grid cap and the anode cap.

[0058] While the present invention has been described through preferred embodiments, it is not limited to the embodiments described herein, and various changes and modifications are made without departing from the scope of the invention.

Claims

1. A laser introduction device for introducing pulsed laser light into an electron gun, wherein the electron gun comprises a body having a cavity, an anode cap, an electron gun filament disposed on the inner top wall of the body, and a grid cap surrounding the electron gun filament and having a grid cap aperture, wherein a first window is provided on the side wall of the body, and a first emission aperture is provided on the bottom wall of the body opposite to the grid cap aperture, the anode cap being disposed on the first emission aperture, characterized in that, The laser introduction device includes: Reflective components arranged within the cavity body; A reflective device is arranged on the top surface of the anode cap so as to face the grid cap. The reflective component is configured such that pulsed laser light incident from the first window and guided by the reflective component can be reflected by the reflective device to pass through the gate cap hole and illuminate the electron gun filament. The reflective component includes: A first and second mirror having relatively parallel axes of rotation, and a mirror support assembly that arranges the first and second mirrors relatively at intervals. At least one mating lens holder assembly, the at least one mating lens holder assembly having the same shape and material as the supporting lens holder assembly, and being arranged relatively dispersed from the supporting lens holder assembly on the bottom wall around the anode cap; The arrangement of the at least one mating lens holder assembly and the supporting lens holder assembly is axially symmetrical with respect to the axial direction of the gate cap hole pointing towards the first emission hole.

2. The laser introduction device according to claim 1, characterized in that, The lens support assembly includes a long, narrow first lens support portion, a second lens support portion, and a connecting portion, as well as two long, narrow, oppositely arranged support portions. The first reflector is arranged on the first mirror support, and the second reflector is arranged on the second mirror support. The first mirror support and the second mirror support are arranged in parallel between the two support parts and can rotate along their respective length directions to form the rotation axis of the first reflector and the second reflector. as well as The connecting part is fixedly connected between the two support parts, and the first lens holder part is arranged between the second lens holder part and the connecting part.

3. The laser introduction device according to claim 2, characterized in that, Each of the two support portions has a hollow groove extending along its length, and each of the first and second lens holder portions extends through the two hollow grooves so that it can slide or rotate along the two hollow grooves and can be secured from the outside of the two hollow grooves by bolt components.

4. The laser introduction device according to claim 1, characterized in that, The support lens assembly is made of a conductive material to allow electrons accumulated on the surface of the reflective assembly to be discharged from the electron gun.

5. The laser introduction device according to claim 1, characterized in that, The reflective device is a thin, circular layer with a central through-hole. Its surface area is large enough that pulsed laser light incident from the first window can be reflected by the outer edge of the reflective device and enter the gate cap aperture to illuminate the electron gun filament. The reflective device and the anode cap are integrally formed.

6. The laser introduction device according to claim 5, characterized in that, The pulsed laser can enter the gate cap hole at a predetermined small angle relative to the axis pointing towards the first emission hole and irradiate the electron gun filament, the predetermined small angle being in the range of 10° to 45°.

7. The laser introduction device according to claim 1, characterized in that, The sidewall of the electron gun is configured to be detachably connected, and the laser introduction device further includes a tubular extension that can engage with the disassembled electron gun at its sidewall to form a sealed, complete cavity.

8. The laser introduction device according to claim 1, characterized in that, The support frame assembly controls the translation or rotation of the reflective component via a microelectromechanical system.

9. A scanning electron microscope with an ultrafast laser source, characterized in that, It also includes a laser introduction device as described in any one of claims 1 to 7, which is used to introduce the pulsed laser generated by the ultrafast laser source into the electron gun of the scanning electron microscope.

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