CN106024551B - A kind of device generating ultrafast electronics using ultrafast ultra-intense laser excitation carbon nanotube - Google Patents

Abstract

The present invention provides a kind of devices generating ultrafast electronics using ultrafast ultra-intense laser excitation carbon nanotube, including electron emission source, excitation light source and light focusing system, the electron emission source includes carbon nano-tube emitter and is used to prepare the cathode substrate of the carbon nanotube；The electron emission source cathode is set to one end in vacuum chamber, and the anode of electronics is collected in the other end setting in the vacuum chamber, and the vacuum chamber is equipped with the entrance window for laser light incident；The light source is ultrafast superpower pulse laser, for emitting ultrafast ultra intense laser pulse；The optical focusing system includes half-wave plate, polarizing film and condenser lens, and the optical focusing system is focused ultrafast ultra intense laser pulse；The ultrafast ultra intense laser pulse passes through half-wave plate, polarizing film and condenser lens and focuses successively；The ultrafast ultra intense laser pulse converges to the carbon nanotube tip region excitation carbon nanotube through the entrance window after focusing and generates ultrafast superpower electronic impulse.

Description

A device that uses ultrafast and ultraintense lasers to excite carbon nanotubes to generate ultrafast electrons

technical field

The invention relates to the technical field of vacuum electron emission, in particular to a device for exciting carbon nanotubes to generate ultrafast electrons with an ultrafast and ultrastrong laser

Background technique

Since the late last century, the birth of ultrafast and ultra-intense lasers has made ultrafast molecular dynamics a research hotspot. At first, all-optical methods such as time-resolved reflection/transmission spectroscopy or Raman spectroscopy were mostly used to explore ultrafast processes. Although these methods can detect the information of atomic and molecular structure changes, the relationship between spectra and atomic and molecular structure information has not been fully explained so far, which undoubtedly increases the analysis of structural change information in transient fast reaction kinetics difficulty. In addition, due to the influence of the optical properties of materials, the scope of application of these methods is very limited. The ultrafast electron microscopy/diffraction technology just makes up for this deficiency, can directly reflect the molecular structure, and provides a powerful tool for directly studying some complex ultrafast reaction processes. Due to the great advantages of high spatial resolution and high temporal resolution, ultrafast electron microscopy has gradually become an important technical means for studying many basic phenomena and mechanisms in physics, chemistry, biology and material science.

The ultrafast electron source is the core component of the above-mentioned advanced scientific equipment. It mainly introduces the ultrafast laser into the cathode of the electron gun to stimulate the emission of ultrafast photoelectron pulses. In ultrafast electron experiments, the time resolution determines the length of electron clusters. Many experiments require electron clusters to be as short as ultrafast and contain a sufficient number of electrons in order to achieve sufficient imaging contrast. At present, the materials used for ultrafast electron sources mainly include: 1. Metal materials, which have bottleneck problems such as low brightness, low current, and strong light required. 2. Low work function semiconductor materials have the disadvantages of low optical power, complicated preparation process, high vacuum requirement, and easy contamination.

Compared with the above materials, carbon nanotubes have the characteristics of small tip radius, high structural stability, high temperature resistance, good electrical conductivity, localized electronic state, etc., resulting in large field enhancement factor, low work function, and large emission current. The advantage is that it is an excellent electron-emitting electron-emitting material. Therefore, the present invention proposes an electron source device that excites carbon nanotubes to generate ultrafast electrons with an ultrafast and ultraintense laser.

Contents of the invention

The object of the present invention is to provide a device for exciting carbon nanotubes to generate ultrafast electrons with an ultrafast and ultra-intensive laser, including an electron emission source cathode, an excitation light source and a light modulation system, and the electron emission source cathode includes a high-brightness carbon nanotube and a for preparing the cathode substrate of the carbon nanotubes;

The cathode of the electron emission source is arranged at one end of the vacuum chamber, the other end of the vacuum chamber is provided with an anode for collecting electrons, and the vacuum chamber is provided with an incident window for laser light;

The light source is an ultra-fast ultra-intense pulse laser, and the ultra-fast ultra-intense pulse laser is used to emit ultra-fast ultra-intensive laser pulses; the optical modulation system includes a half-wave plate, a polarizer and a focusing lens, and the optical modulation system Modulate the parameters such as the peak power, polarization direction, and focus size of ultrafast and ultraintense laser pulses;

The ultra-fast and ultra-intense laser pulses are sequentially focused by a half-wave plate, a polarizer, and a focusing lens; the ultra-fast and ultra-intensive laser pulses are focused and converged to the tip region of the carbon nanotubes through the incident window to excite the carbon nanotubes to generate Ultra-fast and ultra-intense electron pulses.

Preferably, the tip radius of the carbon nanotube is less than 20 nm, and the aspect ratio of the carbon nanotube is greater than 100.

Preferably, the carbon nanotubes are arranged into a carbon nanotube array.

Preferably, the carbon nanotube array is a single carbon nanotube array.

Preferably, the carbon nanotube array is a carbon nanotube cluster array.

Preferably, the central wavelength of the ultrafast ultraintense pulse laser is 800nm, the output power is 30mW, and the repetition frequency is 80MHz.

Preferably, the angle between the incident direction of the ultrafast and ultraintense laser pulse and the vertical direction of the carbon nanotube tip of the electron emission source is between 0-90°.

The present invention provides a device for exciting carbon nanotubes to generate ultrafast electrons with ultrafast and superintense laser pulses. Ultrafast and superintense laser pulses are used to excite carbon nanotubes to generate femtosecond or subfemtosecond electronic pulses. At the same time, the use of carbon nanotubes as the cathode of the electron emission source overcomes the shortcomings of using metal materials as the cathode that require high light intensity, small emission current, and low brightness.

It should be understood that both the foregoing general description and the following detailed description are exemplary illustrations and explanations, and should not be used as limitations on the claimed content of the present invention.

Description of drawings

With reference to the accompanying drawings, more objects, functions and advantages of the present invention will be clarified through the following description of the embodiments of the present invention, wherein:

Fig. 1 schematically shows a schematic structural diagram of a device for exciting carbon nanotubes to generate ultrafast electrons by an ultrafast and ultraintensive laser in the present invention;

Fig. 2 schematically shows the schematic diagram of the ultrafast ultra-intense pulsed laser excitation of the carbon nanotube tip to generate ultrafast electrons in the present invention;

Fig. 3 shows a schematic diagram of a single carbon nanotube array in one embodiment of the present invention;

Fig. 4 shows the relationship between laser power and excitation current in one embodiment of the present invention;

Figure 5 shows a schematic diagram of a single carbon nanotube arrangement in another embodiment of the present invention;

Fig. 6 shows the relationship between laser power and excitation current in another embodiment of the present invention;

Figure 7 shows a schematic diagram of a carbon nanotube cluster array in another embodiment of the present invention;

Fig. 8 shows the relationship between laser power and excitation current in another embodiment of the present invention;

Fig. 9 shows a schematic diagram of a carbon nanotube cluster array in another embodiment of the present invention;

Fig. 10 shows the relationship between laser power and excitation current in another embodiment of the present invention.

Detailed ways

The objects and functions of the present invention and methods for achieving the objects and functions will be clarified by referring to the exemplary embodiments. However, the present invention is not limited to the exemplary embodiments disclosed below; it can be implemented in various forms. The essence of the description is only to help those skilled in the relevant art comprehensively understand the specific details of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the drawings, the same reference numerals represent the same or similar components, or the same or similar steps.

Example 1

As shown in FIG. 1 , a schematic structural diagram of a device for exciting carbon nanotubes to generate ultrafast electrons by an ultrafast and ultraintense laser according to the present invention. The electron source device includes an electron emission source cathode, an excitation light source and a light modulation system, and the electron emission source cathode includes a carbon nanotube 101 and a cathode substrate 102 for preparing the carbon nanotube. The cathode of the electron emission source is arranged in the vacuum chamber 111 at one end of the vacuum chamber; the other end of the vacuum chamber is provided with an anode 109 for collecting electrons; the vacuum chamber 111 is provided with an incident window 108 for laser light to enter. The cathode emits ultrafast electron pulses 110 , which propagate in the vacuum chamber and are collected at the anode 109 end. Preferably, the device for ultrafast electrons produced by the present invention can be used in an electron microscope system, and can also be used in an electron diffraction system. It should be noted that the vacuum chamber mentioned in the embodiments is a schematic example, and it should be understood that the vacuum chamber described in the present invention can be used in all devices that can be used in electron sources.

In the present invention, the light source adopts an ultra-fast ultra-intense pulse laser 103, the central wavelength of the ultra-fast ultra-intense pulse laser 103 is 800nm, the output power is 30mW, and the repetition frequency is 80MHz. The ultra-fast ultra-intense pulse laser 103 is used to emit ultra-fast Fast ultra-intense laser pulses 106 . For the purpose of illustration, the ultra-fast ultra-intense pulse laser in this embodiment and the following embodiments is a femtosecond laser, and the selection of the laser is not specifically limited in the present invention. According to the needs of actual electronic equipment, different central wavelengths, output Power and repetition rate of ultrafast ultraintense lasers.

The optical modulation system includes a half-wave plate 104 , a polarizer 105 and a focusing lens 107 , and the half-wave plate 104 , polarizer 105 and focusing lens 107 are sequentially arranged between the ultrafast and ultra-intense laser 103 and the vacuum cavity 111 . The optical modulation system modulates parameters such as the peak power, polarization direction, and focus size of the ultrafast and ultraintense laser pulse 106 .

The ultrafast ultraintense pulse laser provided by the present invention excites carbon nanotubes to generate ultrafast electrons. Ultrafast ultraintensive laser pulses 106 are emitted by ultrafast ultraintensive pulse lasers 103. During the propagation of ultrafast ultraintensive laser pulses, successively The half-wave plate 104, the polarizer 105 and the focusing lens 106 are focused, and the focused ultrafast and ultra-intense laser pulse 106 passes through the incident window 108 of the vacuum cavity and interacts with the carbon nanotube 101 prepared at one end of the vacuum cavity to generate ultrashort electron groups. As shown in Figure 2, the schematic diagram of the ultrafast and ultraintensive pulsed laser of the present invention exciting the tip of the carbon nanotube to generate ultrafast electrons, the ultrafast and ultraintensive laser pulse converges at the tip area of the carbon nanotube at a certain angle after being modulated by the optical modulation system, ultrafast The incident direction of the ultra-intensive laser pulse forms a certain angle 112 with the vertical direction of the tip of the carbon nanotube 101, and the angle is between 0-90°. Preferably, in this embodiment, the incident direction of the ultrafast and ultraintense laser pulse is 60° from the vertical direction of the tip of the carbon nanotube.

Example 2

This embodiment specifically illustrates the arrangement of carbon nanotubes and carbon nanotube cathode substrates. In this implementation, the tip radius of carbon nanotubes is less than 20 nm, and the aspect ratio of carbon nanotubes is greater than 100. As shown in Figure 3, the schematic diagram of a single carbon nanotube array in this embodiment, a single carbon nanotube array is prepared on the cathode substrate 202b, preferably, the radius of the carbon nanotube tip 213b is about 10nm; the length of the carbon nanotube 201b about 5 μm.

The ultra-fast and ultra-intense laser pulses are modulated by the optical modulation system and converge at the tip area of the carbon nanotubes at a certain angle. Preferably, in this embodiment, the incident direction of the ultrafast and ultraintense laser pulse is 60° from the vertical direction of the carbon nanotube tip. The focused ultra-fast and ultra-intense laser pulses converge on the tip region of the carbon nanotubes, and the intensity increases. On the one hand, when the electrons absorb enough photon energy, they can escape to the vacuum beyond the potential barrier; on the other hand, the strong laser light field can The vacuum barrier at the tip of the carbon nanotube is compressed, and when the barrier width is close to the electron wavelength, the carbon nanotube electrons tunnel through the barrier and escape. In the embodiment of the present invention, the electrons generated are ultra-fast and ultra-intensive electron pulses, as shown in FIG. 4 , the relationship between laser power and excitation current in this embodiment.

Example 3

This embodiment specifically illustrates the arrangement of carbon nanotubes and carbon nanotube cathode substrates. In this embodiment, the tip radius of carbon nanotubes is less than 20 nm, and the aspect ratio of carbon nanotubes is greater than 100. As shown in Figure 5, a schematic diagram of a single carbon nanotube array in this embodiment, the carbon nanotube is prepared in a single way, and the array is on the cathode substrate 202a, preferably, the radius of the carbon nanotube tip 213a is about 5nm; The length of the tube 201a is about 10 μm.

The ultra-fast and ultra-intense laser pulses are modulated by the optical modulation system and converge at the tip area of the carbon nanotubes at a certain angle. In the example, the incident direction of the ultrafast and ultraintense laser pulse is 60° to the vertical direction of the tip of the carbon nanotube. The focused ultra-fast and ultra-intense laser pulses converge on the tip region of the carbon nanotubes, and the intensity increases. On the one hand, when the electrons absorb enough photon energy, they can escape to the vacuum beyond the potential barrier; on the other hand, the strong laser light field can The vacuum barrier at the tip of the carbon nanotube is compressed, and when the barrier width is close to the electron wavelength, the carbon nanotube electrons tunnel through the barrier and escape. In the embodiment of the present invention, the electrons generated are ultra-fast and ultra-intensive electron pulses, as shown in FIG. 6 , the relationship between laser power and excitation current in this embodiment. Compared with Embodiment 2, this embodiment uses thinner carbon nanotube tips to excite electrons under the same laser power, resulting in shorter electron clusters, more electrons, and higher brightness.

Example 4

This implementation specifically illustrates another arrangement of carbon nanotubes and carbon nanotube cathode substrates. In this implementation, the tip radius of carbon nanotubes is less than 20 nm, and the aspect ratio of carbon nanotubes is greater than 100. As shown in Figure 7, the schematic diagram of the array of carbon nanotube clusters in this embodiment, the carbon nanotubes are prepared as nanotube clusters 314b, arrayed on the cathode substrate 302b, preferably, the radius of the carbon nanotube tip 313b in the carbon nanotube clusters It is about 10nm; the length of carbon nanotube is about 5μm.

The ultra-fast and ultra-intense laser pulses are modulated by the optical modulation system and converge at the tip area of the carbon nanotubes at a certain angle. In the example, the incident direction of the ultrafast and ultraintense laser pulse is 60° to the vertical direction of the tip of the carbon nanotube. The focused ultra-fast and ultra-intense laser pulses converge on the tip region of the carbon nanotubes, and the intensity increases. On the one hand, when the electrons absorb enough photon energy, they can escape to the vacuum beyond the potential barrier; on the other hand, the strong laser light field can The vacuum barrier at the tip of the carbon nanotube is compressed, and when the barrier width is close to the electron wavelength, the carbon nanotube electrons tunnel through the barrier and escape. . In the embodiment of the present invention, the electrons generated are ultra-fast and ultra-intensive electron pulses, as shown in FIG. 8 , the relationship between the laser power and the excitation current in this embodiment.

Example 5

This implementation specifically illustrates another arrangement of carbon nanotubes and carbon nanotube cathode substrates. In this implementation, the tip radius of carbon nanotubes is less than 20 nm, and the aspect ratio of carbon nanotubes is greater than 100. As shown in Figure 9, the schematic diagram of the array of carbon nanotube clusters in this embodiment, the carbon nanotubes are prepared as carbon nanotube clusters 314a, arrayed on the cathode substrate 302a, preferably, the radius of the carbon nanotube tip 313a in the carbon nanotube clusters About 5nm; carbon nanotube length about 10μm.

The ultra-fast and ultra-intense laser pulses are focused by the optical focusing system and converge at the tip area of the carbon nanotube at a certain angle. In the example, the incident direction of the ultrafast and ultraintense laser pulse is 60° to the vertical direction of the tip of the carbon nanotube. The focused ultra-fast and ultra-intense laser pulses converge on the tip region of the carbon nanotubes, and the intensity increases. On the one hand, when the electrons absorb enough photon energy, they can escape to the vacuum beyond the potential barrier; on the other hand, the strong laser light field can The vacuum barrier at the tip of the carbon nanotube is compressed, and when the barrier width is close to the electron wavelength, the carbon nanotube electrons tunnel through the barrier and escape. . In the embodiment of the present invention, the electrons generated are ultra-fast and ultra-intensive electron pulses, as shown in FIG. 10 , the relationship between the laser power and the excitation current in this embodiment. Compared with Embodiment 4, this embodiment uses thinner carbon nanotube tips to excite electrons under the same laser power, resulting in shorter electron clusters, more electrons, and higher brightness.

Other embodiments of the invention will be apparent to and understood by those skilled in the art from consideration of the specification and practice of the invention disclosed herein. The description and examples are considered exemplary only, with the true scope and spirit of the invention defined by the claims.

Claims (5)

1. a kind of device generating ultrafast electronics using ultrafast ultra-intense laser excitation carbon nanotube, including electron emission source cathode, Excitation light source and light modulation system, which is characterized in that the electron emission source cathode includes carbon nano-tube emitter and cathode lining Bottom prepares carbon nanotube in the cathode substrate, wherein the carbon nanotube tip radius is less than 20nm, the carbon nanometer Pipe draw ratio is more than 100, and the carbon nanotube arrangement is at carbon nano pipe array；

The electron emission source cathode is set to one end in vacuum chamber, and the sun for collecting electronics is arranged in the other end in the vacuum chamber Pole, the vacuum chamber are equipped with the entrance window for laser light incident；

The light source is ultrafast superpower pulse laser, and the ultrafast superpower pulse laser is for emitting ultrafast ultra-intense laser arteries and veins Punching；The light modulation system includes half-wave plate, polarizing film and condenser lens, and the light modulation system is to ultrafast ultra intense laser pulse Intensity, polarization and focus parameter be modulated；

The ultrafast ultra intense laser pulse passes through half-wave plate, polarizing film and condenser lens successively；The ultrafast ultra intense laser pulse The carbon nanotube tip region excitation carbon nanotube is converged to through the entrance window generate ultrafast electronic impulse after modulation.

2. the apparatus according to claim 1, which is characterized in that the carbon nano pipe array is single-root carbon nano-tube array.

3. the apparatus according to claim 1, which is characterized in that the carbon nano pipe array is carbon nanotube cluster array.

4. the apparatus according to claim 1, which is characterized in that the ultrafast superpower pulse laser centre wavelength is 800nm, output power 30mW, repetition rate 80MHz.

5. the apparatus according to claim 1, which is characterized in that the ultrafast ultra intense laser pulse incident direction and carbon nanometer Tip end vertical direction angle is between 0-90 °.