Device and method for monitoring directivity and thickness measurement of ultrathin nano-film

Abstract

The invention discloses a monitoring device for measuring directivity and thickness of an ultrathin nano film, which forms the following light paths: an incident light path: S polarized light emitted by an S polarized light source is divided into two beams of S polarized light through a non-polarization beam splitting cube, one beam enters a first camera, the other beam enters a polarization beam splitting cube, and the other beam enters a second camera; incident S polarized light passes through the polarization beam splitting cube and then passes through the quarter-wave plate to form circularly polarized light, and the circularly polarized light enters the thin film. The incident light forms reflected light at the film, the reflected light forms P polarized light after passing through a quarter-wave plate, the P polarized light enters a polarization beam splitting cube, and the P polarized light is reflected to a second camera by the polarization beam splitting cube; and in the transmission light path, the incident light forms transmission light at the film, and the transmission light enters the third camera. According to the monitoring device for measuring the directivity and the thickness of the ultra-thin nano-film disclosed by the invention, accurate regulation and control of the directivity and the local film surface flatness and ultra-thin thickness measurement are realized through one system.

Description

Technical Field

[0001] The invention relates to a monitoring device for measuring the directivity and thickness of an ultra-thin nano film, and belongs to the technical field of laser target shooting. Background Art

[0002] In the high-repetition-rate target shooting process of laser ion acceleration, the ions generated by laser ion acceleration are usually set to be emitted along the normal of the film, and then a collimation hole is placed at a long distance to diagnose the ions behind the target. Therefore, if the normal of the target does not strictly point to the collimation hole, the measured ion signal will be inaccurate.

[0003] Currently, there is no method that can be integrated into the target cavity to measure the directivity of the film. For traditional solid film targets, the usual practice is to use a mechanical fixture to adjust the target angle; but for new targets such as liquid films that are suspended and self-supporting, their angle deviation cannot be measured by mechanical devices or any contact method. If the angle deviation cannot be measured, it is impossible to adjust the angle.

[0004] In addition, film thickness is also an important parameter in laser ion acceleration. In the existing methods, the thickness of the liquid film target is generally detected in advance and then treated as a solid film. However, the liquid film target is a dynamic target and the thickness of the liquid film target may change at any time. Therefore, the existing technology cannot achieve real-time measurement of the film thickness and lacks effective monitoring and adjustment methods for the film thickness.

[0005] For the reasons mentioned above, it is necessary to further study the monitoring methods of directivity and thickness measurement of ultra-thin nanofilms to solve the above problems. Summary of the invention

[0006] In order to overcome the above problems, the inventors conducted in-depth research and designed a monitoring device for directivity and thickness measurement of ultra-thin nanofilms. An S-polarized light source, a non-polarized beam splitter cube, a polarized beam splitter cube, a quarter-wave plate, a first camera, and a second camera are arranged at the front end of the film to form the following optical path:

[0007] The incident light path is that the S polarized light is emitted by the S polarized light source, and is split into two beams of S polarized light by the non-polarizing beam splitter cube. One beam enters the first camera, and the other beam enters the polarizing beam splitter cube. The incident S polarized light passes through the polarizing beam splitter cube and then passes through the quarter wave plate to form circularly polarized light. The circularly polarized light enters the film;

[0008] In the reflection light path, the circularly polarized light incident on the film forms reflected light at the film. The reflected light forms P-polarized light after passing through the quarter-wave plate. The P-polarized light enters the polarization beam splitter cube, which reflects the P-polarized light to the second camera.

[0009] In a preferred embodiment, the device further includes a third camera disposed at the rear end of the thin film.

[0010] The optical path further includes a transmission optical path. The circularly polarized light incident on the thin film forms transmitted light at the thin film, and the transmitted light enters the third camera.

[0011] In a preferred embodiment, the S-polarized light source includes a common light source, a half-wave plate, a beam shrinking unit, and a spatial filtering unit.

[0012] The light emitted by the common light source forms S-polarized light through the half-wave plate. The S-polarized light is shrunk by the beam shrinking unit and then the high-frequency components in the light beam are filtered out by the spatial filtering unit to obtain pure S-polarized light.

[0013] The present invention also provides a method for adjusting the directivity of an ultra-thin nano-film, including the following steps:

[0014] S11: Use S-polarized light to transmit through a polarization beam splitting cube. The transmitted light forms circularly polarized light through a quarter-wave plate, and the circularly polarized light is incident on the thin film. The incident circularly polarized light forms reflected light at the thin film. The reflected light forms P-polarized light after passing through the quarter-wave plate. The P-polarized light is incident on the polarization beam splitting cube 4, and the polarization beam splitting cube reflects the P-polarized light to the second camera, and the reflected light spot is output through the second camera.

[0015] S12: Adjust the thin film so that the reflected light spot is minimized. At this time, the normal direction of the thin film is parallel to the incident circularly polarized light.

[0016] In a preferred embodiment, the adjustment of the thin film includes: adjusting the angle of the thin film.

[0017] In a preferred embodiment, when the thin film is a liquid film formed by the collision of fluids ejected from two nozzles, the adjustment further includes: respectively adjusting the flow rates of the two nozzles so that the reflected light spot is mirror-symmetric.

[0018] In a preferred embodiment, before S12, there is also step S10: perform beam-target coupling. Receive the transmitted light formed by the incident circularly polarized light at the thin film through the third camera at the rear end of the thin film, and output the transmitted light spot. Adjust the front and rear positions of the thin film so that the transmitted light spot is minimized.

[0019] The present invention also provides a method for measuring the thickness of an ultra-thin nano-film, including the following steps:

[0020] S21. Use a non-polarizing beam-splitting cube to split an S-polarized light source into two beams of S-polarized light. One beam enters the first camera, and the incident light spot is output through the first camera. The other beam transmits through the polarizing beam-splitting cube. The transmitted light passes through a quarter-wave plate to form circularly polarized light, and the circularly polarized light is incident on the thin film. The incident circularly polarized light forms a reflected light at the thin film. The reflected light passes through the quarter-wave plate and then forms P-polarized light. The P-polarized light is incident on the polarizing beam-splitting cube, and the polarizing beam-splitting cube reflects the P-polarized light to the second camera, and the reflected light spot is output through the second camera.

[0021] S22. Compare the incident light spot and the reflected light spot to obtain the reflectivity of the thin film.

[0022] S23. Determine the thickness of the thin film according to the relationship between the reflectivity, the wavelength of the incident light, and the thickness of the thin film.

[0023] In a preferred embodiment, before S21, the directivity of the thin film is also adjusted.

[0024] In a preferred embodiment, in S23, the relationship between the reflectivity, the wavelength of the incident light, and the thickness of the thin film is as follows:

[0025]

[0026] Among them, λ represents the wavelength of the incident light, θ represents the incident angle, and h represents the thickness of the thin film.

[0027] R(h, λ, θ) represents the reflectivity of the thin film to the incident light, and R 0 (λ, θ) represents the reflectivity of the thin film interface determined by the Fresnel reflection law, and δ(h, λ, θ) represents the optical path difference of the thin film. The optical path difference of the thin film is expressed as:

[0028]

[0029] n(λ) represents the refractive index function of the thin film material.

[0030] The beneficial effects of the present invention include:

[0031] (1) Through a system, precise control of directivity, local film surface flatness, and ultra-thin thickness measurement is achieved.

[0032] (2) It can be set in the laser target chamber to perform real-time measurement and monitoring of the directivity of the liquid film, the flatness of the film surface, and the thickness of the liquid film.

[0033] (3) Cleverly use a polarization-dependent beam-splitting cube to eliminate the interference of the surface reflected light of the element on the return light of the low-reflectivity thin film. Description of the Drawings

[0034] Figure 1Shows the structural schematic diagram of a monitoring device for measuring the directivity and thickness of an ultra-thin nanometer film according to a preferred embodiment of the present invention;

[0035] Figure 2 Shows the reflected light spots of a flat liquid film and an uneven liquid film;

[0036] Figure 3 Shows the reflected light spots obtained during the flatness adjustment of an ultra-thin nanometer film according to a preferred embodiment of the present invention.

[0037] Reference numerals:

[0038] 1 - Film;

[0039] 22 - Half-wave plate;

[0040] 23 - Beam shrinking unit;

[0041] 24 - Spatial filtering unit;

[0042] 3 - Non-polarizing beam splitter cube;

[0043] 4 - Polarizing beam splitter cube;

[0044] 5 - Quarter-wave plate;

[0045] 61 - First camera;

[0046] 62 - Second camera;

[0047] 7 - Third camera. Detailed implementation manners

[0048] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Through these descriptions, the features and advantages of the present invention will become clearer and more definite.

[0049] The special term "exemplary" herein means "serving as an example, embodiment or illustration". Any embodiment described herein as "exemplary" does not necessarily have to be construed as superior to or better than other embodiments. Although various aspects of the embodiments are shown in the drawings, the drawings do not have to be drawn to scale unless otherwise specified.

[0050] The present invention provides a monitoring device for measuring the directivity and thickness of an ultra-thin nanometer film. As Figure 1 shown, a S-polarized light source, a non-polarizing beam splitter cube 3, a polarizing beam splitter cube 4, a quarter-wave plate 5, a first camera 61, and a second camera 62 are provided at the front end of the film 1, thereby forming the following optical path:

[0051] The incident light path: S-polarized light is emitted from an S-polarized light source and is split into two beams of S-polarized light by an unpolarized beam-splitting cube 3. One beam enters the first camera 61, and the other beam enters the polarization beam-splitting cube 4. The incident S-polarized light passes through a quarter-wave plate 5 after transmitting through the unpolarized beam-splitting cube 3 to form circularly polarized light, and the circularly polarized light is incident on the thin film 1.

[0052] The reflected light path: The circularly polarized light incident on the thin film 1 forms reflected light at the thin film 1. The reflected light forms P-polarized light after passing through the quarter-wave plate 5. The P-polarized light is incident on the polarization beam-splitting cube 4, and the polarization beam-splitting cube 4 reflects the P-polarized light to the second camera 62.

[0053] Since the reflected light of the thin film 1 is very weak and is comparable to the reflected light intensity of other devices in the light path, and the reflected light of the thin film 1 overlaps with the reflected light of other devices in the light path, it is difficult to accurately measure the reflected light of the thin film 1, and thus the detection of the directivity of the thin film cannot be achieved.

[0054] In the present invention, by using a polarization-dependent beam-splitting cube, the interference of the surface reflected light of the element on the backward light of the low-reflectivity thin film is eliminated.

[0055] The polarization beam-splitting cube 4 can transmit S-polarized light and reflect p-polarized light. In the above-mentioned incident light path, the reflected light generated by the glass surface of the polarization beam-splitting cube 4 is still S-polarized light, which will not enter the second camera but will return along the dotted line, thus not interfering with the acquisition of the reflected light by the second camera. Specifically, as Figure 1 shown, when the s-polarized light is reflected by the right surface of the polarization beam-splitting cube 4, the reflected light is still s-polarized light, and it will directly return along the original path, as shown by the dotted arrow in the figure, and will not be reflected by the polarization beam-splitting cube 4 into the second camera below; on the contrary, the reflected light of the thin film is p-polarized light and will enter the second camera 62. This design particularly solves the problem that it is difficult to measure the directivity of a thin film with a low self-reflectivity.

[0056] In the present invention, with the above structure, the measurement of the directivity and thickness of the thin film is simultaneously achieved by a set of devices.

[0057] In a preferred embodiment, the device further includes a third camera 7 disposed at the rear end of the thin film 1.

[0058] The light path further includes a transmission light path. The circularly polarized light incident on the thin film 1 forms transmitted light at the thin film 1, and the transmitted light enters the third camera 7.

[0059] With the above structure, the beam-target coupling of the thin film is also achieved.

[0060] In a preferred embodiment, the S-polarized light source includes a common light source, a half-wave plate 22, a beam shrinking unit 23, and a spatial filtering unit 24.

[0061] The light emitted by a common light source forms S-polarized light through a half-wave plate 22. The S-polarized light is beam-reduced by a beam-reducing unit 23 and then passes through a spatial filtering unit 24 to filter out the high-frequency components in the light beam, obtaining pure S-polarized light.

[0062] The beam-reducing unit 23 can adopt any unit capable of focusing light. For example, a lens or a combination of lenses can be used as the beam-reducing unit.

[0063] The spatial filtering unit 24 can adopt any unit capable of filtering. For example, it can be realized by the combination of a small hole and a lens, and the high-frequency components are filtered out through the small hole.

[0064] In a preferred embodiment, a lens is provided between the polarization beam splitting cube 4 and the second camera 62. The directivity measurement range and accuracy are adjusted through the lens. Specifically, by adjusting the position of the lens, different measurement ranges and accuracies can be achieved according to different object-image relationships.

[0065] The present invention also provides a method for adjusting the directivity of an ultra-thin nano-film, preferably carried out by using the above monitoring device for measuring the directivity and thickness of the ultra-thin nano-film, including the following steps:

[0066] S11: The S-polarized light is transmitted through the polarization beam splitting cube, and the transmitted light forms circularly polarized light through a quarter-wave plate. The circularly polarized light is incident on the film; the incident circularly polarized light forms reflected light at the film, and the reflected light forms P-polarized light after passing through the quarter-wave plate. The P-polarized light is incident on the polarization beam splitting cube 4, and the polarization beam splitting cube reflects the P-polarized light to the second camera, and the reflected light spot is output through the second camera.

[0067] S12: Adjust the film to make the reflected light spot minimum. At this time, the normal direction of the film is parallel to the incident circularly polarized light.

[0068] In the high-repetition-rate target shooting of laser ion acceleration, we need to set the ions generated by laser ion acceleration to exit along the normal of the film, that is, the laser emission direction needs to be parallel to the normal direction of the film.

[0069] In a preferred embodiment, adjusting the film includes adjusting the angle of the film. When the film is a flat solid film, the size of the reflected light spot can intuitively reflect whether the normal direction of the film is parallel to the incident circularly polarized light. When there is an angle between the two, the light spot will increase, and the larger the angle, the larger the light spot.

[0070] Furthermore, in the high-repetition-rate target shooting of laser ion acceleration, when the film is a liquid film, in addition to requiring the normal direction of the film to be parallel to the laser emission direction, it is also required that the liquid film has a high flatness. The existing methods currently cannot effectively adjust and detect the flatness of the liquid film.

[0071] In the present invention, when the film is a liquid film, the liquid film is formed by the collision of fluids ejected from two nozzles, and the adjustment further includes adjusting the flow rates of the two nozzles respectively, and adjusting the flow rates to make the reflected light spots symmetrical, thereby achieving adjustment of the flatness of the liquid film.

[0072] In traditional cognition, the flatness of the liquid film is mainly affected by the size of the two nozzles, and the flatness is adjusted by fine-tuning the size of the nozzles. In the traditional method, a main pump is used to supply liquid to the two nozzles at the same time to ensure that the liquid flow rate of the two nozzles is the same, and it is believed that this method can improve the flatness of the liquid film. However, this cognition is only a theoretical understanding, and there is currently no method to detect flatness.

[0073] In the present invention, the flatness of the liquid film is detected by the symmetry of the reflected light spot. The inventors found that when the flatness of the liquid film is higher, the reflected light spot is more symmetrical: when the incident light irradiates the liquid film non-vertically, the reflected light spot of the flat liquid film is a diffraction fringe such as Figure 2 As shown in (a), the reflected light spot of the uneven liquid film is Figure 2 (b) When the incident light irradiates the liquid film vertically, although the diffraction fringes no longer appear in the reflected light spot of the flat liquid film, the light spot is concentrated, while the reflected light spot of the uneven liquid film is messy and asymmetric.

[0074] In the present invention, unlike the traditional method of adjusting the nozzle size, the flow rate of liquid ejected from the two nozzles is adjusted separately to adjust the flatness of the liquid film. This method is quick to adjust and does not require frequent reprocessing of the nozzle size. Combined with the reflected light spot, the liquid film flatness can be quickly adjusted.

[0075] According to the present invention, when the thin film is a liquid film formed by the collision of fluids ejected from two nozzles, the adjustment further comprises: adjusting the flow rates of the two nozzles respectively so that the reflected light spots are mirror-symmetrical.

[0076] Further, Figure 3 The result obtained during a certain liquid film flatness adjustment process is shown. It can be seen that with the adjustment, the light spot gradually becomes mirror-symmetrical, indicating that the liquid film gradually becomes flat. When the light spot is symmetrical and the light spot is the smallest, it indicates that the liquid film is flat and perpendicular to the incident light.

[0077] In a preferred embodiment, before S12, there is further step S10, performing beam-target coupling: receiving the transmitted light formed by the incident circularly polarized light at the film through a third camera at the rear end of the film, and outputting a transmitted light spot; adjusting the front and rear positions of the film to minimize the transmitted light spot. At this time, the film is located at the focusing position of the light path.

[0078] The present invention also discloses a method for measuring the thickness of an ultra-thin nanofilm, which is preferably performed using the above-mentioned monitoring device for measuring the directivity and thickness of an ultra-thin nanofilm, and comprises the following steps:

[0079] S21. Use a non-polarizing beam-splitting cube to split an S-polarized light source into two beams of S-polarized light. One beam enters the first camera, and the incident light spot is output through the first camera. The other beam transmits through the polarizing beam-splitting cube. The transmitted light passes through a quarter-wave plate to form circularly polarized light, and the circularly polarized light is incident on the thin film. The incident circularly polarized light forms a reflected light at the thin film. The reflected light passes through the quarter-wave plate and then forms P-polarized light. The P-polarized light is incident on the polarizing beam-splitting cube 4, and the polarizing beam-splitting cube reflects the P-polarized light to the second camera, and the reflected light spot is output through the second camera.

[0080] S22. Compare the incident light spot and the reflected light spot to obtain the reflectivity of the thin film.

[0081] S23. Determine the thickness of the thin film according to the relationship between the reflectivity, the wavelength of the incident light, and the thickness of the thin film.

[0082] The traditional film thickness measurement method is generally the reflection spectroscopy method. According to the reflection spectroscopy method, the reflectivity spectrum corresponding to different thicknesses is unique. Therefore, the film thickness can be inversely solved by measuring the reflection spectrum of the thin film. However, the inventor found that this method has great limitations. When using a conventional light source for measurement, when the thickness of the film is very small, the oscillation of the reflectivity spectrum becomes very slow, and the oscillation frequency is close to the quasi-Gaussian envelope of the usually white light source, bringing large errors. Therefore, when the thickness of the film to be measured is less than 150 nm, the measurement accuracy is significantly deteriorated, and even the situation where the value cannot be measured appears. Although the measurement accuracy can be further improved by using an ultraviolet broadband light source, the cost is very high. Even when using an ultraviolet broadband light source, it can only measure the thickness of films above 60 nm, and still cannot achieve the measurement of film thickness below 50 nm.

[0083] In the present invention, instead of using the spectrum to measure the film thickness, a method for measuring the film thickness according to the relationship between the reflectivity, the wavelength of the incident light, and the thickness of the thin film is proposed.

[0084] In S22, preferably, the light intensity of the reflected light spot and the incident light spot are respectively integrated, and the ratio of the light intensity integration is used as the reflectivity of the thin film.

[0085] In S23, the relationship between the reflectivity, the wavelength of the incident light, and the thickness of the thin film is:

[0086]

[0087] Among them, λ represents the wavelength of the incident light, θ represents the incident angle, and h represents the thickness of the thin film;

[0088] R(h,λ,θ) represents the reflectivity of the thin film, R 0$(λ,θ)$ represents the reflectivity of the thin film interface determined by the Fresnel reflection law, and $δ(h,λ,θ)$ represents the optical path difference of the thin film. The optical path difference of the thin film is expressed as:

[0089]

[0090] $n(λ)$ represents the refractive index function of the thin film material.

[0091] Furthermore, the reflectivity $R$ of the thin film interface determined by the Fresnel reflection law 0 $(λ,θ)$ is expressed as:

[0092]

[0093]

[0094]

[0095] wherein, $R$ s $(λ,θ)$ and $R$ p $(λ,θ)$ are intermediate variables.

[0096] In a preferred embodiment, before S21, the directivity of the thin film is further adjusted so that the incident light is parallel to the normal direction of the thin film, that is, the incident angle $θ = π / 2$.

[0097] More preferably, the directivity adjustment of the thin film is performed by using the above-mentioned directivity adjustment method for ultra-thin nano-films.

[0098] Example

[0099] Example 1

[0100] Adopt Figure 1 The device shown for the directivity adjustment and thickness detection of the thin film. Among them, the directivity adjustment of the thin film includes the following steps:

[0101] S11: Use S-polarized light to transmit through the polarization beam splitting cube. The transmitted light forms circularly polarized light after passing through the quarter-wave plate. The circularly polarized light is incident on the thin film; the incident circularly polarized light forms reflected light at the thin film. The reflected light forms P-polarized light after passing through the quarter-wave plate. The P-polarized light is incident on the polarization beam splitting cube 4, and the polarization beam splitting cube reflects the P-polarized light to the second camera, and the reflected light spot is output through the second camera;

[0102] S12: Adjust the thin film so that the reflected light spot is minimized. At this time, the normal direction of the thin film is parallel to the incident circularly polarized light.

[0103] By directly irradiating the film with light, the directivity deviation of the film is detected by measuring the angle between the reflected light and the direct light of the film: Before adjusting the directivity deviation of the film, the reflection angle of the film can reach 3°. After laser targeting, the proton energy obtained is 8 MeV, and the proton charge is 4 nC. After adjustment, the emission angle of the film is close to 0°. After laser targeting, the proton energy obtained is 10 MeV, and the proton charge is 10 nC.

[0104] The thickness measurement includes the following steps:

[0105] S21: Use a non-polarizing beam-splitting cube to split the S-polarized light source into two beams of S-polarized light. One beam enters the first camera, and the incident light spot is output through the first camera. The other beam transmits through the polarizing beam-splitting cube. The transmitted light passes through a quarter-wave plate to form circularly polarized light, and the circularly polarized light is incident on the film. The incident circularly polarized light forms reflected light at the film. After passing through the quarter-wave plate, the reflected light forms P-polarized light, and the P-polarized light is incident on the polarizing beam-splitting cube 4. The polarizing beam-splitting cube reflects the P-polarized light to the second camera, and the reflected light spot is output through the second camera.

[0106] S22: Compare the incident light spot and the reflected light spot to obtain the film reflectivity.

[0107] S23: Determine the film thickness according to the relationship between the reflectivity, the incident light wavelength, and the film thickness.

[0108] In S23, the relationship between the reflectivity, the incident light wavelength, and the film thickness is as follows:

[0109]

[0110] The finally obtained film thickness is 232 nm. The film thickness is measured by the reflection spectroscopy method, and the measurement result is 238 nm. The error between the two is 2.5%, which proves that the above thickness measurement method has accurate results.

[0111] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "upper", "lower", "inner", "outer", "front", "rear", etc. is the orientation or positional relationship based on the working state of the present invention. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. In addition, the terms "first", "second", "third", "fourth" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0112] In the description of the present invention, it should be noted that unless otherwise clearly defined and limited, the terms "installed", "connected", and "coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection in general; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0113] The present invention has been described above in combination with preferred embodiments. However, these embodiments are merely exemplary and only serve an illustrative purpose. On this basis, various substitutions and improvements can be made to the present invention, and these all fall within the protection scope of the present invention.

Claims

1. A monitoring device for measuring the directivity and thickness of an ultra-thin nano-film, characterized in that, an S-polarized light source, an unpolarized beam splitter cube (3), a polarized beam splitter cube (4), a quarter-wave plate (5), a first camera (61), and a second camera (62) are arranged at the front end of the film (1), thereby forming the following optical path: Incident optical path: The S-polarized light emitted by the S-polarized light source is divided into two beams of S-polarized light by the unpolarized beam splitter cube (3). One beam enters the first camera (61), and the other beam enters the polarized beam splitter cube (4). The incident S-polarized light passes through the quarter-wave plate (5) after passing through the unpolarized beam splitter cube (3) to form circularly polarized light, and the circularly polarized light is incident on the film (1); Reflection optical path: The circularly polarized light incident on the film (1) forms reflected light at the film (1). The reflected light forms P-polarized light after passing through the quarter-wave plate (5). The P-polarized light is incident on the polarized beam splitter cube (4), and the polarized beam splitter cube (4) reflects the P-polarized light to the second camera (62).

2. The monitoring device for measuring the directivity and thickness of an ultra-thin nano-film according to claim 1, characterized in that, the device further includes a third camera (7) arranged at the rear end of the film (1), and the optical path further includes a transmission optical path. The circularly polarized light incident on the film (1) forms transmitted light at the film (1), and the transmitted light enters the third camera (7).

3. The monitoring device for measuring the directivity and thickness of an ultra-thin nano-film according to claim 1, characterized in that, the S-polarized light source includes a common light source, a half-wave plate (22), a beam reducing unit (23), and a spatial filtering unit (24), the light emitted by the common light source forms S-polarized light through the half-wave plate (22). The S-polarized light is reduced in beam size by the beam reducing unit (23), and then the high-frequency components in the light beam are filtered out by the spatial filtering unit (24) to obtain pure S-polarized light.

4. A method for adjusting the directivity of an ultra-thin nano-film, characterized in that, it includes the following steps: S11: Use S-polarized light to transmit through the polarized beam splitter cube. The transmitted light forms circularly polarized light through the quarter-wave plate, and the circularly polarized light is incident on the film; the incident circularly polarized light forms reflected light at the film. The reflected light forms P-polarized light after passing through the quarter-wave plate. The P-polarized light is incident on the polarized beam splitter cube, and the polarized beam splitter cube reflects the P-polarized light to the second camera, and the reflected light spot is output through the second camera; S12: Adjust the film so that the reflected light spot is the smallest. At this time, the normal direction of the film is parallel to the incident circularly polarized light.

5. The method for adjusting the directivity of an ultra-thin nano-film according to claim 4, characterized in that, the adjustment of the film includes: adjusting the angle of the film.

6. The method for adjusting the directivity of an ultra-thin nano-film according to claim 4, characterized in that, when the film is a liquid film formed by the collision of fluids ejected from two nozzles, the adjustment further includes: respectively adjusting the flow rates of the two nozzles so that the reflected light spot is mirror-symmetric.

7. The method for adjusting the directivity of an ultra-thin nano-film according to claim 4, characterized in that, Before S12, there is also step S10 of performing beam-target coupling: receiving, at the back end of the thin film, the transmitted light formed by the incident circularly polarized light at the thin film through a third camera, and outputting a transmitted light spot; adjusting the front and back positions of the thin film to minimize the transmitted light spot.

8. A method for measuring the thickness of an ultra-thin nano-thin film, characterized in that, it includes the following steps: S21. Using a non-polarizing beam-splitting cube to split an S-polarized light source into two beams of S-polarized light, one beam enters a first camera, and the incident light spot is output through the first camera; the other beam transmits through the polarizing beam-splitting cube, and the transmitted light forms circularly polarized light after passing through a quarter-wave plate, and the circularly polarized light is incident on the thin film; the incident circularly polarized light forms reflected light at the thin film, and the reflected light forms P-polarized light after passing through the quarter-wave plate, and the P-polarized light is incident on the polarizing beam-splitting cube 4, and the polarizing beam-splitting cube reflects the P-polarized light to a second camera, and the reflected light spot is output through the second camera; S22. Comparing the incident light spot and the reflected light spot to obtain the reflectivity of the thin film; S23. Determining the thickness of the thin film according to the relationship between the reflectivity, the wavelength of the incident light, and the thickness of the thin film.

9. The method for measuring the thickness of an ultra-thin nano-thin film according to claim 7, characterized in that, before S21, the directivity of the thin film is also adjusted.

10. The method for measuring the thickness of an ultra-thin nano-thin film according to claim 8, characterized in that, in S23, the relationship between the reflectivity, the wavelength of the incident light, and the thickness of the thin film is: where λ represents the wavelength of the incident light, θ represents the incident angle, and h represents the thickness of the thin film; R(h, λ, θ) represents the reflectivity of the thin film to the incident light, and R 0 (λ, θ) represents the reflectivity of the thin film interface determined by the Fresnel reflection law, and δ(h, λ, θ) represents the optical path difference of the thin film. The optical path difference of the thin film is expressed as: n(λ) represents the refractive index function of the thin film material.

Images