A broughst window stack polarization modulation device

Abstract

The application discloses a Brewster window stack polarization modulation device. The device comprises a Brewster window stack assembly, a clamping assembly, and an installation base. The Brewster window stack assembly comprises a plurality of optical window pieces arranged in parallel and at intervals, and the included angle between the surface normal and the incident light is a Brewster angle. The installation base has a vertical part and a horizontal part. The clamping baffle is arranged opposite to the vertical part of the installation base at intervals. The optical window pieces and the gaskets are alternately arranged in parallel at intervals. One adjusting screw is arranged on each side of the installation base. The adjusting screw passes through the clamping baffle and each gasket in sequence, and is screwed with the vertical part of the installation base. The rotation of the adjusting screw is converted into the linear motion of the clamping baffle along the support surface, so as to change the distance between the clamping baffle and the vertical part and / or realize the clamping and fixing of the Brewster window stack assembly. The device can realize linearly polarized light output with high extinction ratio and high stability in a wide range of incident angles and spectral bands.

Description

Technical Field

[0001] This invention relates to the field of polarization modulation technology, specifically to a polarization modulation device comprising a Brewster window stack and a dedicated clamping structure working in concert, which is particularly suitable for scenarios such as laser polarization state control and optical detection. Background Technology

[0002] With the rapid development of modern industrial technology, especially the in-depth application of laser technology, optical sensing, and optoelectronics in precision manufacturing and inspection, the frequency and importance of light in measurement, processing, and quality control processes have significantly increased. In precision measurement fields (such as nanoscale interferometers, optical profilometers, and high-resolution imaging systems) and semiconductor manufacturing fields (such as photolithography, thin film deposition, and defect detection processes), the stringent requirements for measurement accuracy and process stability are becoming increasingly prominent, directly relying on the precise control of the beam polarization state. Specifically, these high-precision applications must ensure that the incident beam has a single, pure, and stable polarization state, because polarization inhomogeneity can lead to distortion of beam focusing characteristics, abnormal material response, and a decrease in the signal-to-noise ratio of the measurement signal, thereby causing systematic errors, reduced manufacturing yield, and even product failure. For example, in semiconductor photolithography, even small deviations in polarization state can cause resolution loss and linewidth fluctuations in pattern transfer, severely affecting chip integration and performance. Therefore, achieving high-purity linearly polarized light output has become a key technological requirement in modern industry for improving measurement reliability and manufacturing accuracy.

[0003] Natural light is typically unpolarized, meaning its electric field vector vibrates randomly in a plane perpendicular to its propagation direction. As a transverse wave, this polarization characteristic of light has a decisive influence on the behavior of optical systems: it not only modulates the focusing characteristics of the beam (such as focal size and intensity distribution) but also significantly affects the absorption, scattering, and reflection responses of materials to incident light, while simultaneously determining the reflection and transmission behavior at optical interfaces (such as the polarization-dependent effects described by the Fresnel equations). Therefore, precise modulation of the polarization state is crucial for optimizing the performance of optical systems.

[0004] Currently, common polarization modulation methods mainly include birefringence, reflection, and dichroism. Among them, Brewster windows based on the reflection principle are widely used in the generation and modulation of polarized light due to their advantages such as no need for coating, high damage threshold, wide applicable wavelength range, and simple structure.

[0005] However, the linearly polarized light produced by traditional monolithic Brewster windows has limited purity, which is insufficient to meet the requirements of high-precision applications. Furthermore, in the assembly and adjustment of classical optical systems, existing optical clamping devices for placing components and modulating optical paths still have shortcomings in terms of stability, computational accuracy, and ease of assembly and adjustment if precise control of the pose and spacing between optical components is required. Summary of the Invention

[0006] To address the problems existing in the background art, the present invention provides a Brewster window stacked polarization modulation device. This device, through a structurally stable and easily adjustable clamping device, reliably fixes the relative positions and orientations of multiple Brewster windows over a wide range of incident angles and spectral bands, thereby stably obtaining linearly polarized light output with a high extinction ratio.

[0007] The technical solution adopted in this invention is:

[0008] I. A Brewster window stacked polarization modulation device

[0009] The Brewster window stacking assembly includes:

[0010] Multiple optical windows are arranged in parallel intervals, and the angle between the surface normal of each optical window and the incident light is Brewster's angle.

[0011] The clamping assembly includes multiple gaskets, a clamping baffle, adjusting screws, and a mounting base. The mounting base has a vertical portion and a horizontal portion. The Brewster window stacking assembly, the gaskets, and the clamping baffle are arranged above the horizontal portion. The clamping baffle is arranged at intervals relative to the vertical portion of the mounting base, and the Brewster window stacking assembly and the gaskets are arranged between them. The optical window panes and the gaskets are arranged alternately and are all parallel to the clamping baffle and the vertical portion of the mounting base.

[0012] An adjusting screw is arranged on each side of the mounting base. The adjusting screw passes through the clamping baffle and each washer in sequence and then engages with the vertical part of the mounting base. This converts the rotational movement of the adjusting screw into the linear movement of the clamping baffle, thereby changing the distance between the clamping baffle and the vertical part of the mounting base and / or achieving the clamping and fixing of the Brewster window stacking assembly.

[0013] Specifically, the Brewster window stacking assembly includes eight optical window panes, and the clamping assembly includes seven spacers.

[0014] Specifically, threaded holes are provided on both sides of the vertical part of the mounting base, and through holes are provided on both sides of the gasket and the clamping baffle. The two through holes on the same side and the threaded holes on the vertical part of the mounting base correspond to each other and are aligned axially. The same adjusting screw is inserted into the two through holes and the threaded hole on each side. The adjusting screw passes through the through holes on the clamping baffle and each gasket in sequence, and then screws into the threaded hole on the vertical part of the mounting base and engages with the threaded hole.

[0015] Specifically, the gasket is dumbbell-shaped, consisting of a narrower first rectangular portion in the middle and wider second rectangular portions at both ends. Each of the two second rectangular portions has a through hole for the adjusting screw to pass through. The centers of the two through holes are located on the horizontal center line of the gasket and are symmetrically distributed on both sides of the vertical center line of the gasket.

[0016] Specifically, the gasket is made of a ductile material.

[0017] Specifically, the gasket is made of copper.

[0018] Specifically, the gasket has a thickness of 0.1 mm and a surface parallelism of less than or equal to 0.01°.

[0019] Specifically, both the clamping baffle and the vertical part of the mounting base are provided with inwardly extending bosses on their opposing surfaces, and the surfaces of the two bosses contact the optical window plates on both sides respectively.

[0020] Specifically, the adjusting screw is a fine-thread knurled screw.

[0021] Specifically, the optical window is rectangular in shape, and the width of the clamped portion does not exceed 38mm.

[0022] The beneficial effects of this invention are:

[0023] 1. In the polarization modulation device provided by the present invention, on the one hand, the polarization purity of the transmitted light is significantly improved to over 90% by stacking multiple Brewster windows and filtering them through multiple reflections. On the other hand, a clamping mechanism is specially designed for the Brewster window stacking assembly. Compared with existing general clamping tools, this clamping device has a simple and efficient assembly and adjustment process with high repeatability. It can not only reliably maintain the precise positional relationship between the windows and control the parallelism between the windows within 0.01°, but also ensure the high stability of the relative parallelism and spacing between the windows. This avoids the parallelism drift caused by changes in ambient temperature or mechanical vibration, which ultimately leads to problems such as unstable extinction ratio performance.

[0024] 2. This invention provides a novel polarization modulation device that, through the coordinated high-precision stacking and stable clamping of Brewster windows within a wide range of incident angles and spectral bands, ensures that multiple window plates maintain a stable relative position and orientation during long-term use, thereby achieving high extinction ratio and high stability linear polarized light output. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the Brewster window stacking assembly disclosed in this invention.

[0026] Figure 2 This is a graph showing the variation of polarization degree and transmittance of the polarization modulation device disclosed in this invention with the number of windows.

[0027] Figure 3 This is a graph showing the polarization degree (N=8) and transmittance of the polarization modulation device disclosed in this invention as a function of the incident angle.

[0028] Figure 4 This is a graph showing the polarization degree (N=8) and transmittance of the polarization modulation device disclosed in this invention as a function of wavelength.

[0029] Figure 5 This is a three-dimensional structural view of the polarization modulation device disclosed in this invention.

[0030] Figure 6 This is a left view of the structure of the polarization modulation device disclosed in this invention.

[0031] Figure 7 This is a top view of the structure of the polarization modulation device disclosed in this invention.

[0032] Figure 8 This is a force analysis diagram of the polarization modulation device disclosed in this invention.

[0033] The components include: 1. Optical window, 2. Gasket, 3. Clamping baffle, 4. Adjusting screw, and 5. Mounting base. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0035] This invention provides a Brewster window stacked polarization modulation device. For example... Figure 5 As shown, the Brewster window stacked polarization modulation device of the present invention includes a Brewster window stacking assembly and a clamping assembly.

[0036] The Brewster window stack assembly comprises multiple parallel, spaced-apart optical window panes 1. For example... Figure 1 As shown, the angle between the surface normal of each optical window 1 and the incident light is Brewster angle, that is, the incident light is incident on the incident surface of the first optical window 1 at Brewster angle.

[0037] like Figure 5 As shown, the clamping assembly includes multiple washers 2, clamping baffles 3, adjusting screws 4, and a mounting base 5. Figure 6As shown, the mounting base 5 has a vertical part and a horizontal part that are perpendicular to each other. The upper surface of the horizontal part serves as a support surface. A Brewster window stacking assembly, a gasket 2, and a clamping baffle 3 are arranged on the top of the horizontal part. The bottom surfaces of the Brewster window stacking assembly, the gasket 2, and the clamping baffle 3 are all in sliding contact with the support surface. The clamping baffle 3 is arranged at intervals relative to the vertical part of the mounting base 5 and is parallel to each other. The relative surfaces of the clamping baffle 3 and the vertical part of the mounting base 5 serve as the first positioning reference surface and the second positioning reference surface, respectively. The clamping baffle 3 cooperates with the vertical part of the mounting base 5, so that a clamping force can be applied evenly along the normal direction of the window piece, avoiding the window piece from tilting due to the additional torque, thereby ensuring the parallelism accuracy between multiple window pieces.

[0038] A Brewster window stacking assembly and a gasket 2 are arranged between the clamping baffle 3 and the vertical part of the mounting base 5. The optical window pieces 1 and the gasket 2 in the Brewster window stacking assembly are arranged alternately and parallel to each other. That is, a gasket 2 is arranged between two adjacent optical window pieces 1. No gasket 2 is set between the first optical window piece 1 and the last optical window piece 1 and the two positioning reference surfaces, the first positioning reference surface and the second positioning reference surface.

[0039] like Figure 7 As shown, an adjusting screw 4 is arranged on each side above the mounting base 5. The adjusting screw 4 passes through the clamping baffle 3 and each washer 2 in sequence, and then engages with the vertical part of the mounting base 5 through thread. By converting the rotational movement of the adjusting screw 4 into the linear movement of the clamping baffle 3 along the support surface, the distance between the two positioning reference surfaces (the first positioning reference surface and the second positioning reference surface) is changed and / or the Brewster window stacking assembly is clamped and fixed.

[0040] During use, the relative distance and clamping force between the clamping baffle 3 and the vertical part of the mounting base 5 are adjusted by adjusting the adjusting screw 4, so that the two work together to stack the window pieces and each pad 2, thereby simultaneously achieving reliable clamping of multiple window pieces, precise control of the parallelism between adjacent window pieces, and determination of the window piece spacing.

[0041] The specific operating steps of the clamping device of the present invention are as follows:

[0042] 1. Spacing and Clamping of Multiple Window Pieces: First, based on the number and thickness of the optical window pieces 1 to be clamped, and the preset adjacent spacing, loosen the adjusting screws 4 to create a sufficient initial gap between the clamping baffle 3 and the mounting base 5. Then, insert the shims 2 sequentially, dividing the total gap into multiple independent sub-gap spaces. Next, place the optical window pieces 1 one by one into these sub-gap spaces. Finally, simultaneously and evenly tighten the adjusting screws 4 on both sides. During this process, the clamping baffle 3 and the mounting base 5 work together to apply a uniform clamping force, which is transmitted to each window piece through the highly parallel shims 2, thereby achieving reliable fixation, parallelism constraint, and spacing maintenance of all window pieces in one operation.

[0043] 2. Removal and replacement of specific window pieces: If it is necessary to adjust the stacked structure (such as removing one piece), simply loosen adjusting screw 4 to widen the gap, and the target window piece can be safely removed. Then, tighten the screw again to re-secure the remaining structure. This process is simple and quick, and does not easily disturb the position of other window pieces.

[0044] Preferably, the Brewster window stacking assembly includes eight optical window panes 1, and the clamping assembly includes seven spacers 2.

[0045] Preferably, threaded holes are provided on both sides of the vertical part of the mounting base 5, and through holes are provided on both sides of the gasket 2 and the clamping baffle 3. The two through holes on the same side and the threaded holes on the vertical part of the mounting base 5 are arranged in a corresponding manner and aligned in the axial direction. The same adjusting screw 4 is inserted into the two through holes and the threaded holes on each side. The end of the adjusting screw 4 passes through the through holes on the clamping baffle 3 and each gasket 2 in sequence, and then screws into the threaded hole of the vertical part of the mounting base 5 and engages with the threaded hole.

[0046] Preferably, the washer 2 is dumbbell-shaped, consisting of a first rectangular portion that is narrower in the middle and second rectangular portions that are wider at both ends. Each of the two second rectangular portions has a through hole for the adjusting screw 4 to pass through. Figure 8 As shown, in the clamping assembly, the holes of the clamping baffle 3, the holes of the mounting base 5, and the midpoint of the shim 2 are all on the same axis. This ensures that the application of force (to the adjusting screw 4 and the mounting base 5) and its transmission (to the shim 2 and the optical window 1) are also kept in a straight line. For each optical window 1 and shim 2, the vertical direction is subject to gravity and the supporting force of the clamping base, while the horizontal direction is subject to the clamping forces from both sides (all on a straight line; analyzing the rotational torque with any point as the axis of rotation will cancel each other out), preventing the generation of additional torque that could cause tilting.

[0047] It should be noted that in the clamping assembly, the centers of the two through holes must be located on the horizontal center line of the gasket 2 and symmetrically distributed on both sides of the vertical center line of the gasket 2. Otherwise, the gasket 2 will tilt, failing to provide uniform force to the window pane and causing an uneven wedge-shaped gap at the top of the window pane.

[0048] Preferably, the gasket 2 is made of a ductile material, which can evenly distribute the clamping stress and reduce the risk of deformation of the window sheet.

[0049] Preferably, gasket 2 is made of copper.

[0050] Preferably, the thickness of the gasket 2 is 0.1 mm, and the surface parallelism is less than or equal to 0.01°.

[0051] Preferably, the centers of the through holes on both sides of the gasket 2 are located on the horizontal center line of the gasket 2, and are symmetrically distributed on both sides of the vertical center line of the gasket 2.

[0052] Preferably, the vertical surfaces of the clamping baffle 3 and the mounting base 5 are provided with protrusions extending inward, and the surfaces of the two protrusions contact the optical window plates 1 on both sides respectively, which can avoid scratching the optical surface of the window plates during clamping and further reduce the concentration of contact stress.

[0053] Preferably, the adjusting screw 4 is a fine-pitch knurled screw. Specifically, the adjusting screw 4 is a precision fine-pitch adjusting screw with a knurled elongated cylindrical head for easy manual tightening; the fine-pitch thread significantly improves the adjustment resolution and enables precise distance control.

[0054] Specific embodiments of the present invention are as follows:

[0055] Example

[0056] This embodiment provides a Brewster window stacked polarization modulation device comprising eight optical windows 1 and seven spacers 2. In this embodiment, the size of the optical windows 1 is 25×36×1mm.

[0057] In this embodiment, the adjusting screw 4 is an M3×0.25 single-ended fine-pitch adjusting screw. One full rotation of this screw results in an axial feed lead of 0.25 mm, and approximately 0.69 μm of axial feed per 1° rotation. In contrast, a standard M3 coarse-pitch screw provides approximately 1.39 μm of axial feed per 1° rotation. This demonstrates that the fine-pitch adjusting screw achieves sub-micron level precision fine-tuning, significantly reducing the risk of over-adjustment. Furthermore, the shorter pitch of the fine-pitch thread allows for smaller clearance control and lower backlash error in the threaded drive, further improving the repeatability of the fine-tuning. In addition, the smaller helix angle of the fine-pitch thread results in significantly better frictional self-locking than coarse-pitch threads. After adjustment, it is less prone to loosening or displacement due to vibration or external forces, maintaining stable precision over a long period and avoiding repeated calibration.

[0058] The optical performance of the Brewster window stacked assembly in this embodiment will be explained below using optical principles and numerical analysis.

[0059] When light is incident at a certain angle on the interface between two media, the reflection and transmission behavior can be described by Fresnel's equations. For the s-polarized component (electric field vector perpendicular to the incident plane) and the p-polarized component (electric field vector parallel to the incident plane), its amplitude reflection coefficient... With amplitude transmission coefficient The following formulas are given respectively:

[0060]

[0061]

[0062]

[0063]

[0064] in, and These are the refractive indices of the incident medium and the transmitted medium, respectively. and These are the angle of incidence and the angle of refraction, respectively.

[0065] According to Fresnel's equations, when the incident angle satisfies the Brewster angle condition, the reflection coefficient of the p-polarized component is... When the polarization is zero, total transmission occurs with no reflection. In this case, the reflected light is completely linearly polarized (s-polarized), while the transmitted light is purified due to partial reflection of the s-component, resulting in an increased degree of polarization. Brewster's angle. The angle of refraction and the angle of incidence must be complementary. Combined with Snell's Law ( It can be deduced that:

[0066]

[0067] For a beam with a wavelength of 633 nm and an initial p-polarization degree of 50% (i.e. 45° linearly polarized light from air ( )Incidentally injected into a stack of fused silica windows ( Brewster's angle was calculated. From this perspective, the transmittance of a single air-fused silica interface is calculated. For the s-component, its transmittance is... For the p component, its transmittance is When a light beam passes through a window (passing through two interfaces), the total transmittance of each component is the product of the transmittances of the corresponding interfaces. Simultaneously, the overall absorption coefficient of the window for transmitted light is considered to be... .

[0068] Based on this, it is assumed that the air-glass interface and the glass-air interface of the same window pane exhibit the same refractive and reflective behavior, i.e., T s With T p Assuming the polarization P remains constant and neglecting multiple reflections within the glass (meaning light only undergoes two interface transmissions through the window: air → glass and glass → air), it can be deduced that after the incident light passes through N parallel window panes, the p-polarization P of the output beam and the overall transmittance T are respectively:

[0069]

[0070]

[0071] The transmittance of the s-component and the p-component are expressed as follows:

[0072]

[0073]

[0074] In polarization modulation, high polarization degree and high overall transmittance are often mutually restrictive indicators. To comprehensively evaluate performance, this embodiment introduces a balanced quality factor composed of polarization degree and overall transmittance:

[0075]

[0076] Calculations show that when the number of windows N=8, the p-polarization degree of the output beam reaches 90.2%, while the overall transmittance remains above 55%, achieving the best performance balance.

[0077] Figure 2 The curves showing the change of polarization degree and overall transmittance with the increase of the number of windows clearly show that when N=8, the s-polarization component has been effectively filtered out, while the transmitted light intensity remains at a practical level.

[0078] Figure 3 The curves showing the polarization degree as a function of the incident angle are presented. It can be seen that within a relatively wide range of incident angles near the Brewster angle (fluctuating within 5° above and below the Brewster angle), the polarization degree consistently remains above 74%, and the transmittance remains above 55%, indicating that the device has a certain tolerance for incident angle deviations. This demonstrates that the polarization modulation device provided in this embodiment maintains excellent performance within a certain range close to the Brewster angle.

[0079] Figure 4 The stacked structure was demonstrated to achieve a polarization degree better than 89.5% across a wide spectral range from 210 nm to 1200 nm, thus proving its wide-band applicability.

[0080] The aforementioned high performance relies heavily on the extremely high parallelism and spacing accuracy of the window plate stacking structure. Therefore, this invention specifically designs a dedicated clamping device, achieving a high degree of synergy between optical and mechanical design.

[0081] In summary, this invention effectively solves the technical challenge of maintaining parallelism and spacing when stacking multiple Brewster windows by combining a Brewster window stacking structure with a dedicated high-precision clamping device. The device of this invention not only stably generates highly polarized linearly polarized light over a wide wavelength and angle range, but also boasts advantages such as easy assembly and adjustment, high stability, and ease of maintenance. It is highly suitable for laser optical systems, precision optical inspection, and other cutting-edge optical applications with stringent requirements for polarization purity.

[0082] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this invention, and these modifications or substitutions should all be covered within the scope of protection of this invention. Therefore, the scope of protection of this invention should be determined by the scope of the claims.

Claims

1. A Brewster window stacked polarization modulation device, characterized in that, include: Brewster window stacking assembly includes multiple optical window pieces (1) arranged in parallel intervals, and the angle between the surface normal of each optical window piece (1) and the incident light is a Brewster angle. The clamping assembly includes multiple gaskets (2), clamping baffles (3), adjusting screws (4), and mounting base (5); the mounting base (5) has a vertical part and a horizontal part, the Brewster window stacking assembly, the gaskets (2), and the clamping baffles (3) are arranged above the horizontal part, the clamping baffles (3) are arranged at intervals relative to the vertical part of the mounting base (5), the Brewster window stacking assembly and the gaskets (2) are arranged between them, the optical window pieces (1) and the gaskets (2) are arranged alternately and are parallel to the clamping baffles (3) and the vertical part of the mounting base (5); An adjusting screw (4) is arranged on each side of the mounting base (5). The adjusting screw (4) passes through the clamping baffle (3) and each washer (2) in sequence, and then engages with the vertical part of the mounting base (5) through a thread. This converts the rotational movement of the adjusting screw (4) into the linear movement of the clamping baffle (3), thereby changing the distance between the clamping baffle (3) and the vertical part of the mounting base (5) and / or achieving the clamping and fixing of the Brewster window stacking assembly. The vertical part of the mounting base (5) is provided with threaded holes on both sides, and the gasket (2) and the clamping baffle (3) are provided with through holes on both sides. The two through holes on the same side and the threaded holes of the vertical part of the mounting base (5) are arranged in a corresponding manner and aligned in the axial direction. The same adjusting screw (4) is inserted in the two through holes and the threaded hole on each side. The adjusting screw (4) passes through the through holes on the clamping baffle (3) and each gasket (2) in sequence, and then screws into the threaded hole of the vertical part of the mounting base (5) and engages with the threaded hole. The gasket (2) is dumbbell-shaped, consisting of a narrower first rectangular part in the middle and a wider second rectangular part at both ends. Each of the two second rectangular parts has a through hole for the adjusting screw (4) to pass through. The center of the two through holes is located on the horizontal center line of the gasket (2) and is symmetrically distributed on both sides of the vertical center line of the gasket (2). The gasket (2) is made of a ductile material; The surface parallelism of the gasket (2) is less than or equal to 0.01°.

2. The Brewster window stacked polarization modulation device according to claim 1, characterized in that: The Brewster window stacking assembly includes eight optical window pieces (1), and the clamping assembly includes seven spacers (2).

3. The Brewster window stacked polarization modulation device according to claim 1, characterized in that: The optical window (1) is rectangular in shape, and the width of the clamped part does not exceed 38mm.

4. The Brewster window stacked polarization modulation device according to claim 1, characterized in that: The gasket (2) is made of copper.

5. The Brewster window stacked polarization modulation device according to claim 1 or 4, characterized in that: The thickness of the gasket (2) is 0.1 mm.

6. The Brewster window stacked polarization modulation device according to claim 1, characterized in that: The clamping baffle (3) and the mounting base (5) are provided with protrusions extending inward on the opposite surfaces of their vertical parts, and the surfaces of the two protrusions are in contact with the optical window plates (1) on both sides respectively.

7. The Brewster window stacked polarization modulation device according to claim 1, characterized in that: The adjusting screw (4) is a fine-tooth knurled screw.

8. A polarization modulation method employing a Brewster window stacked polarization modulation device as described in any one of claims 1 to 7, characterized in that, Includes the following steps: According to the number, thickness and preset interval of the optical window pieces (1) to be clamped, loosen the adjusting screw (4) to create a sufficient initial total gap between the clamping baffle (3) and the mounting base (5). Place the gaskets (2) into the initial total gap in sequence, and divide the initial total gap into multiple independent sub-gap; The optical window (1) is placed into each sub-gap one by one; Tighten the adjusting screws on both sides simultaneously and evenly (4); The angle between the surface normal of the optical window (1) and the incident light is Brewster's angle, thereby achieving polarization modulation of the incident light.

Images