Preparation method of thickness-adjustable zero-order wave plate for full-band application and zero-order wave plate

Abstract

The present invention belongs to the technical field of optical polarization elements. To address the limitations of the existing technology that are not free from the inherent limitations of the crystal itself, a method for preparing a zero-order wave plate with adjustable thickness for full-band applications and a zero-order wave plate are provided. The method for preparing a zero-order wave plate with adjustable thickness for full-band applications includes determining the crystal material corresponding to the operating band, calculating the spatial distribution data of the birefringence of the crystal corresponding to the operating band, and calculating the theoretical thickness of the zero-order wave plate device for the current operating band corresponding to different light incident directions; determining the crystal cutting angle of the zero-order wave plate device for the current operating wavelength, and cutting the crystal based on the theoretical thickness of the zero-order wave plate device to obtain an initial zero-order wave plate device; gradually adjusting the thickness of the initial zero-order wave plate device to perform phase delay correction on the adjusted initial zero-order wave plate device until the phase delay error is zero, thereby preparing the final zero-order wave plate. The method can achieve optimal design of birefringence and wave plate thickness in the direction of the non-refractive index principal axis.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical polarization elements, and in particular relates to a preparation method of a thickness-adjustable zero-order wave plate for full-band application and the zero-order wave plate. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] Wave plates are important optical components used to control the polarization state of lasers. Currently, commercial wave plate devices mainly include zero-order wave plates and multi-order wave plates. Compared with multi-order wave plates, zero-order wave plates have the advantages of low wavelength sensitivity, high temperature stability, and a large effective reception angle. Due to the large birefringence of existing wave plate materials, zero-order wave plates on the market are very thin. The thickness of a commercial 355 nm quartz wave plate is only 18 μm, which is very difficult to process and use. Due to the large birefringence of commercial wave plate materials in the ultraviolet band, zero-order wave plates with an operating wavelength below 300 nm cannot be processed and put into use due to their thin thickness. Therefore, the development of wave plate devices that can achieve thickness control and full-band application has become a key issue that urgently needs to be solved in the fields of materials and optics.

[0004] It is well known that the birefringence in a crystal increases with decreasing wavelength. Currently, there are no zero-order waveplate crystals or devices suitable for the deep ultraviolet (DUV) band. Moreover, common waveplate crystals such as quartz and mica cannot be used in the mid- and far-infrared bands. With the development of new wavelength lasers, zero-order waveplates with application bands covering the deep UV and far-infrared bands have attracted widespread attention. In recent years, many research teams have attempted to develop new waveplate materials with lower birefringence to increase the thickness of zero-order waveplates and address their fragility during fabrication and use. New waveplate crystals such as Fe(C5H5)2, Cs4PbBr6, Cs3B3O3F6, Na4Be2PO4F, PEA2CuCl4, Na2KP3O9, and Na2AlSO4F3 have been reported, but the birefringence of these crystals remains relatively high (>0.001). In addition, many polymer materials, such as liquid crystal polymer (PDMS), are also receiving increasing attention as new wave plate materials. However, their practical application is limited by some inherent defects, such as unstable physical and chemical properties, easy deliquesce, and poor resistance to laser damage. To date, no zero-order wave plates with millimeter-level thickness and wide application band have been developed and applied. Currently, the research on wave plate crystals and devices has not yet broken away from the limitations of the crystal itself. All wave plate crystals are limited to uniaxial crystals, and the birefringence used in current device design is a fixed value, which is determined by the intrinsic properties of the crystal. Therefore, it is urgent to develop a new wave plate design method to provide a zero-order wave plate with full-band application and sufficient thickness. Summary of the Invention

[0005] In order to solve the technical problems existing in the above-mentioned background technology, the present invention provides a preparation method of a thickness-adjustable zero-order wave plate for full-band application and a zero-order wave plate, which can achieve optimal design of birefringence and wave plate thickness in the direction of the non-refractive index principal axis.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A first aspect of the present invention provides a method for preparing a thickness-adjustable zero-order wave plate for full-band applications.

[0008] A method for preparing a thickness-adjustable zero-order wave plate for full-band applications, comprising:

[0009] Select the working band of the zero-order wave plate device to be prepared, determine the crystal material corresponding to the working band, and then calculate the spatial distribution data of the birefringence of the crystal corresponding to the working band;

[0010] According to the spatial distribution data of the birefringence of the crystal in the corresponding working band, the theoretical thickness of the zero-order wave plate device in the current working band corresponding to different light incident directions is calculated;

[0011] According to the theoretical thickness of the zero-order wave plate device in the current working band, the crystal cutting angle of the zero-order wave plate device of the current working wavelength is determined;

[0012] The crystal is cut according to the determined crystal cutting angle and the theoretical thickness of the zero-order wave plate device to obtain an initial zero-order wave plate device;

[0013] The thickness of the initial zero-order wave plate device is gradually adjusted to perform phase delay correction on the adjusted initial zero-order wave plate device until the phase delay error is 0, thereby preparing the final zero-order wave plate.

[0014] Based on the refractive index ellipsoid equation, the anisotropic refractive index generated by the light vector incident on the anisotropic crystal at any angle is solved, and the birefringence of the biaxial crystal and the uniaxial crystal under different incident conditions is determined in combination with the crystal refractive index dispersion equation, and used as the birefringence spatial distribution data.

[0015] As an embodiment, when a light wave is incident along any angle (θ, φ), the resulting birefringence is given by the formula: Calculated; among them, and are the refractive indices of slow light and fast light propagating in the biaxial crystal, respectively; θ and φ are the directions of the incident light in the spherical coordinate system.

[0016] In one embodiment, the birefringence is a function of the direction of incidence.

[0017] As an embodiment, when light propagates in a crystal along a set direction, the generated birefringence is zero, and this direction is the optical axis in the crystal.

[0018] As an implementation method, the calculation formula for the theoretical thickness of the zero-order wave plate device is:

[0019] ;

[0020] in, is the theoretical thickness of the zero-order wave plate device; is the wavelength of the incident light; is the birefringence; is the phase delay difference.

[0021] As an embodiment, the crystal material for ultraviolet to near infrared bands is at least one of borates, silicates and fluorides.

[0022] As an embodiment, the crystal material for the mid-infrared band adopts at least one of phosphate, niobate, molybdate, tantalate, gallate, titanate, tellurate and tungstate.

[0023] As an embodiment, the crystal material for the far-infrared band adopts at least one of sulfide, selenide and phosphide.

[0024] A second aspect of the present invention provides a zero-order wave plate.

[0025] A zero-order wave plate is prepared by using the steps in the above-mentioned method for preparing a thickness-adjustable zero-order wave plate for full-band application.

[0026] The beneficial effects of the present invention are:

[0027] The present invention adjusts the crystal cutting angle based on the spatial distribution data of the anisotropic crystal birefringence to achieve free control of the wave plate thickness. The prepared zero-order wave plate has a thickness of millimeters and is easy to process, store and use. The present invention breaks through the limitations of the inherent birefringence performance of the material and can achieve wide-band optical applications from deep ultraviolet to far infrared by selecting different crystal materials. The zero-order wave plate prepared by the present invention has a phase delay error of 0 and has excellent polarization control capabilities.

[0028] Advantages of additional aspects of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0030] Figure 1 This is the relationship between the thickness of the SiO2 crystal zero-order 1 / 2 wave plate and the incident direction of light at a wavelength of 355 nm;

[0031] Figure 2 This is the relationship between the thickness of the SiO2 crystal zero-order 1 / 2 wave plate and the incident direction of light at a wavelength of 633 nm;

[0032] Figure 3 This is the relationship between the thickness of the SiO2 crystal zero-order 1 / 2 wave plate and the incident direction of light at a wavelength of 796 nm;

[0033] Figure 4 This is the relationship between the thickness of the zero-order 1 / 2 wave plate of the KTP crystal and the incident direction of light at a wavelength of 2700 nm;

[0034] Figure 5 The relationship between the thickness of the zero-order 1 / 2 wave plate of LiInSe2 crystal and the incident direction of light at a wavelength of 5000 nm;

[0035] Figure 6 The relationship between the thickness of the zero-order 1 / 2 wave plate of LiInSe2 crystal and the incident direction of light at a wavelength of 10000 nm;

[0036] Figure 7 A diagram of a polarization control experimental setup independently constructed according to an embodiment of the present invention;

[0037] Figure 8 The test results of the 633nm zero-order SiO2 crystal half-wave plate device prepared in the embodiment of the present invention;

[0038] Figure 9 This is a flow chart of a method for preparing a thickness-adjustable zero-order wave plate for full-band applications according to an embodiment of the present invention. DETAILED DESCRIPTION

[0039] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0040] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0041] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0042] In order to solve the problems in the background technology, the present invention provides a method for preparing a thickness-adjustable zero-order wave plate for full-band application. By solving the refractive index ellipsoid equation, the method studies the polarization direction of light and the spatial distribution of birefringence in all anisotropic crystals, and can achieve the optimal design of birefringence and wave plate thickness in the direction of the non-refractive index principal axis, breaking through the bottlenecks of traditional wave plate devices and the optical performance limitations of the matrix material, and also providing a variety of wave plate crystals with excellent performance in the full band.

[0043] Example 1

[0044] In this embodiment, if Figure 9 As shown, a method for preparing a thickness-adjustable zero-order wave plate for full-band applications is provided, comprising:

[0045] Step 1: Select the working band of the zero-order wave plate device to be prepared, determine the crystal material corresponding to the working band, and then calculate the spatial distribution data of the birefringence of the crystal in the corresponding working band;

[0046] Step 2: Calculate the theoretical thickness of the zero-order wave plate device for the current working band corresponding to different light incident directions based on the birefringence spatial distribution data of the crystal in the corresponding working band;

[0047] Step 3: Determine the crystal cutting angle of the zero-order wave plate device at the current working wavelength based on the theoretical thickness of the zero-order wave plate device at the current working band;

[0048] Step 4: Cut the crystal according to the determined crystal cutting angle and the theoretical thickness of the zero-order wave plate device to obtain the initial zero-order wave plate device;

[0049] Step 5: Gradually adjust the thickness of the initial zero-order wave plate device to perform phase delay correction on the adjusted initial zero-order wave plate device until the phase delay error is 0, thereby preparing the final zero-order wave plate.

[0050] In step 1, in the ultraviolet to near-infrared band, it includes but is not limited to borates, silicates and fluorides, such as BaB2O4, KBe2BO3F2, LiB3O5, MgF2 and SiO2; in the mid-infrared band, it includes but is not limited to phosphates, niobates, molybdates, tantalates, gallates, titanates, tellurates and tungstates, such as KTiOPO4 (KTP), LiNbO3, TiO2, MgTe2O5, KTiOAsO4 and LiTaO3; in the far-infrared band, it includes but is not limited to sulfides, selenides and phosphides, such as GdSiP2, BaGaSe7, LilnSe2 and ZnGeP2.

[0051] It should be noted here that the crystal materials for different working bands can be selected according to actual conditions.

[0052] In this embodiment, SiO2, KTP, and LiInSe2 are used as wave plate crystals for the deep ultraviolet to near infrared, mid-infrared, and far infrared bands, respectively, to verify the wave plate design method proposed in this invention. The physical properties of the crystal, such as the light transmission band, mechanical properties, and physicochemical stability, are important guarantees for achieving band widening, stable device performance, and convenient processing technology. SiO2 crystals have advantages such as stable physicochemical properties, good crystal growth habits, high laser damage threshold, and short ultraviolet cutoff edge, making them the preferred wave plate material for the deep ultraviolet to near infrared band. Based on the same considerations, KTP and LiInSe2 crystals are used as wave plate materials for the mid-infrared and far-infrared bands, respectively.

[0053] In step 1, based on the refractive index ellipsoid equation, the anisotropic refractive index generated by the light vector incident on the anisotropic crystal at any angle is solved, and the birefringence of the biaxial crystal and the uniaxial crystal under different incident conditions is determined in combination with the crystal refractive index dispersion equation, and used as the birefringence spatial distribution data.

[0054] In a biaxial crystal, light is incident along a non-principal axis direction to determine the refractive index. The refractive index ellipsoid is an important tool for describing the light propagation characteristics in anisotropic crystals. In anisotropic crystals, the refractive index of light depends not only on the wavelength, but also on its propagation direction and polarization direction. The refractive index ellipsoid provides a visual method that helps to understand and calculate the refractive index, polarization direction, and birefringence effect of light in anisotropic crystals. The refractive index ellipsoid equation of a biaxial crystal can be expressed in the principal axis coordinate system as:

[0055] (1);

[0056] In any refractive index ellipsoid, the incident light vector is incident in a direction perpendicular to the ellipsoid. The intersection of the tangent plane perpendicular to the light vector and passing through the coordinate origin and the refractive index ellipsoid is an ellipse. The difference between the major and minor axes of the ellipse is the birefringence generated by the light vector passing through the material. Assume that the directions of the incident light in the spherical coordinate system are θ and φ. First, through coordinate transformation, make one of the rectangular coordinate axes consistent with the direction of the incident light. Let the X and Y axes rotate around the Z axis by an angle φ. The relationship between the axes in the original coordinate system and the axes in the new coordinate system is:

[0057] (2);

[0058] exist In the coordinate system. Let and X′ axis around The axis rotation angle θ, the relationship between the axes in the original coordinate system and the axes in the new coordinate system is:

[0059] (3);

[0060] Substituting formulas (2) and (3) into formula (1), we obtain:

[0061] (4);

[0062] After two coordinate transformations, The axis is consistent with the direction of the incident light. Equation (4) is the expression of the refractive index ellipsoid equation in the coordinate system that meets this requirement. According to the principles of crystal optics, a plane is made through the coordinate origin and perpendicular to the wave vector. The intersection of this plane and the refractive index ellipsoid is an ellipse. The lengths of the major and minor semi-axes of the ellipse are the refractive indices of slow light and fast light propagating in the crystal. In the coordinate system, the plane equation is expressed as:

[0063] (5);

[0064] Substituting the above equation into equation (4) yields the elliptical equations representing the refractive indices of slow and fast light propagating in the crystal. To determine the lengths of their major and minor semi-axes, i.e., the refractive indices of the two light waves, we convert them into principal axes. and Shaft winding Axis rotation angle Similar to the derivation of formula (3) and formula (4), we can get:

[0065] (6);

[0066] (7);

[0067] (8);

[0068] and are the refractive indices of slow light and fast light propagating in the biaxial crystal, respectively. The direction is the vibration direction of the electric displacement vector D1 of the slow light, is the vibration direction of the electric displacement vector D2 of the fast light.

[0069] Equation (6) is the principal axis ellipse equation. 、 The coefficient of the term must be equal to 0, so we can solve it:

[0070] (9);

[0071] In a uniaxial crystal, = ,but ,

[0072] (10);

[0073] (11);

[0074] When light waves are incident along any angle (θ, φ), the resulting birefringence can be expressed by the formula: The above solution results confirm that when light propagates in the crystal along a specific direction, the birefringence generated is zero, and this direction is the optical axis in the crystal. When light is incident on the crystal along the Y axis, the maximum birefringence can be achieved, which is By adjusting the incident direction of light, the birefringence of anisotropic crystals can be freely controlled. By cutting the crystal along a non-principal axis, the birefringence becomes a function of the incident direction, which can be flexibly controlled according to specific requirements, breaking through the inherent birefringence limit of the material itself.

[0075] In step 2, based on the birefringence spatial distribution data of crystals in different working bands, the process of calculating the theoretical thickness of the zero-order wave plate device in different working bands corresponding to different light incident directions is as follows:

[0076] ;

[0077] in, is the theoretical thickness of the zero-order wave plate device; is the wavelength of the incident light; is the birefringence; is the phase retardation difference. The phase retardation difference of the zero-order half-wave plate is π.

[0078] In step 4, preferably, according to the present invention, the zero-order 1 / 4 and 1 / 2 wave plates of SiO2 crystal with an operating wavelength of 355 nm have a crystal tangent angle θ of 6.3° and device thicknesses of 0.759 and 1.518 mm, respectively.

[0079] Preferably, according to the present invention, the SiO2 crystal zero-order 1 / 4 and 1 / 2 wave plates have an operating wavelength of 633 nm, a crystal tangent angle θ of 8.6°, and device thicknesses of 0.789 and 1.578 mm, respectively.

[0080] Preferably, according to the present invention, the zero-order 1 / 4 and 1 / 2 wave plates of SiO2 crystal have an operating wavelength of 796nm, a crystal tangent angle θ of 10°, and device thicknesses of 0.748 and 1.496 mm respectively.

[0081] According to the preferred embodiment of the present invention, the KTP crystal zero-order 1 / 4 and 1 / 2 wave plates with an operating wavelength of 2700 nm have crystal tangent angles (θ, φ) of (18.2°, 0°), and device thicknesses of 1.102 and 2.204 mm, respectively.

[0082] According to the preferred embodiment of the present invention, the zero-order 1 / 4 and 1 / 2 wave plates of LiInSe2 crystal with an operating wavelength of 5000 nm have a crystal tangent angle (θ, φ) of (63.7°, 0°), and the device thicknesses are 1.045 and 2.091 mm respectively.

[0083] According to the preferred embodiment of the present invention, the zero-order 1 / 4 and 1 / 2 wave plates of LiInSe2 crystal with an operating wavelength of 10000 nm have a crystal tangent angle (θ, φ) of (67.6°, 0°), and device thicknesses of 1.007 and 2.013 mm, respectively.

[0084] In step 5, the process of performing phase delay correction on the cut crystal is as follows:

[0085] Grind on a polishing machine, first coarsely grind to the theoretical thickness, then calibrate on the fiber optic spectrometer, and repeatedly fine-grind until the phase delay error is 0.

[0086] This example also constructs a polarization test experimental setup to test the polarization control performance of the fabricated zero-order wave plate. The setup consists of a laser source, a polarizer, and an analyzer. By adjusting the angles of the polarizer and analyzer relative to the optical axis of the zero-order wave plate, and recording the output power, the polarization state of the light can be determined.

[0087] Example 2

[0088] This embodiment adopts the steps in the preparation method of the thickness-adjustable zero-order wave plate for full-band application as described in Example 1, and calculates the relationship between the thickness of the SiO2 crystal zero-order 1 / 2 wave plate and the incident direction of light at a wavelength of 355 nm as follows: Figure 1 Based on this, a SiO2 crystal zero-order 1 / 2 wave plate with a working wavelength of 355nm was prepared. The light transmission area of the wave plate is 10×10 mm 2 , the tangential angle θ is 6.3°, and the device thickness is 1.486 mm.

[0089] Example 3

[0090] This embodiment adopts the steps of the method for preparing a thickness-adjustable zero-order wave plate for full-band application as described in Example 1 to prepare a SiO2 crystal zero-order quarter-wave plate with an operating wavelength of 355nm. The light-transmitting area of the wave plate is 10×10mm. 2 , the tangential angle θ is 6.3°, and the device thickness is 0.743 mm.

[0091] Example 4

[0092] This embodiment adopts the steps in the method for preparing a thickness-adjustable zero-order wave plate for full-band application as described in Example 1, and calculates the relationship between the thickness of the SiO2 crystal zero-order 1 / 2 wave plate and the incident direction of light at a wavelength of 633 nm as follows: Figure 2 Based on this, a SiO2 crystal zero-order 1 / 2 wave plate with a working wavelength of 633 nm was prepared. The light transmission area of the wave plate is 10×10 mm 2 , the tangential angle θ is 8.6°, and the device thickness is 1.577 mm.

[0093] Example 5

[0094] This embodiment provides a SiO2 crystal zero-order quarter-wave plate with an operating wavelength of 633 nm and a light-transmitting area of 10 × 10 mm. 2 , the tangential angle θ is 8.6°, and the device thickness is 0.788 mm.

[0095] Example 6

[0096] This embodiment adopts the steps in the preparation method of the thickness-adjustable zero-order wave plate for full-band application as described in Example 1, and calculates the relationship between the thickness of the SiO2 crystal zero-order 1 / 2 wave plate and the incident direction of light at a wavelength of 796 nm as follows: Figure 3 Based on this, a SiO2 crystal zero-order 1 / 2 wave plate with a working wavelength of 796nm was prepared. The light transmission area of the wave plate is 10×10 mm 2 , the tangential angle θ is 10°, and the device thickness is 1.496 mm.

[0097] Example 7

[0098] This embodiment adopts the steps of the method for preparing a thickness-adjustable zero-order wave plate for full-band application as described in Example 1 to prepare a SiO2 crystal zero-order quarter-wave plate with an operating wavelength of 796 nm. The light-transmitting area of the wave plate is 10×10 mm. 2 , the tangential angle θ is 10°, and the device thickness is 0.748 mm.

[0099] Example 8

[0100] This embodiment adopts the steps in the preparation method of the thickness-adjustable zero-order wave plate for full-band application as described in Example 1, and calculates the relationship between the thickness of the KTP crystal zero-order 1 / 2 wave plate and the incident direction of light at a wavelength of 2700 nm as follows: Figure 4 Based on this, a KTP crystal zero-order 1 / 2 wave plate with a working wavelength of 2700 nm was prepared. The light-transmitting area of the wave plate is 10×10 mm 2 , the tangential angle (θ, φ) is (18.2°, 0°), and the device thickness is 2.204 mm.

[0101] Example 9

[0102] This embodiment adopts the steps of the method for preparing a thickness-adjustable zero-order wave plate for full-band application as described in Example 1 to prepare a KTP crystal zero-order quarter-wave plate with an operating wavelength of 2700 nm. The light-transmitting area of the wave plate is 10×10 mm. 2 , the tangential angle (θ, φ) is (18.2°, 0°), and the device thickness is 1.102 mm.

[0103] Example 10

[0104] This embodiment adopts the steps in the preparation method of the thickness-adjustable zero-order wave plate for full-band application as described in Example 1, and calculates the relationship between the thickness of the LiInSe2 crystal zero-order 1 / 2 wave plate and the light incident direction at a wavelength of 5000nm as follows: Figure 5 Based on this, a LiInSe2 crystal zero-order 1 / 2 wave plate with a working wavelength of 5000nm was prepared. The light-transmitting area of the wave plate is 10×10mm 2 , the tangential angle (θ, φ) is (63.7°, 0°), and the device thickness is 2.091 mm.

[0105] Example 11

[0106] This embodiment provides a LiInSe2 crystal zero-order quarter-wave plate with an operating wavelength of 5000 nm. The light-transmitting area of the wave plate is 10×10 mm. 2 , the tangential angle (θ, φ) is (63.7°, 0°), and the device thickness is 1.045 mm.

[0107] Example 12

[0108] This embodiment adopts the steps in the preparation method of the thickness-adjustable zero-order wave plate for full-band application as described in Example 1, and calculates the relationship between the thickness of the LiInSe2 crystal zero-order 1 / 2 wave plate and the light incident direction at a wavelength of 10000nm as follows: Figure 6 Based on this, a LiInSe2 crystal zero-order 1 / 2 wave plate with a working wavelength of 10000nm was prepared. The light transmission area of the wave plate is 10×10 mm 2 , the tangential angle (θ, φ) is (67.6°, 0°), and the device thickness is 2.013 mm.

[0109] Example 13

[0110] This embodiment provides a LiInSe2 crystal zero-order quarter-wave plate with an operating wavelength of 10000 nm and a light-transmitting area of 10×10 mm. 2, the tangential angle (θ, φ) is (67.6°, 0°), and the device thickness is 1.007 mm.

[0111] The crystal cutting angle and thickness information of the zero-order wave plates prepared in Examples 2-13 are summarized in Table 1. To ensure that the phase delay accuracy of the optical crystal element meets the design requirements, a high-precision wavelength-tunable fiber spectrometer combined with a polarization analysis system is used to calibrate the zero-order wave plate device.

[0112] During the experiment, the SiO2, KTP and LiInSe2 crystals were first precisely oriented using a RAL diffractometer. They were then cut to their initial thickness (theoretical value + 50μm) using a CNC diamond wire cutting machine. These crystals were then precision-polished in a constant temperature and humidity laboratory environment until the phase delay error of the device was zero at the target wavelength.

[0113] The following is a self-built polarization control experimental device, such as Figure 7 The polarization control capability of the zero-order wave plate device prepared in the present invention was tested. The specific experimental steps are as follows:

[0114] (1) Turn on the laser light source. To ensure the stability of the laser output power during the test, turn on the laser and preheat it for about 15 minutes before testing.

[0115] (2) Finding the wave plate optical axis. First, adjust the position of the polarizer and analyzer so that the polarization of the polarizer and analyzer are parallel (the point where the power meter detects maximum energy). Then, introduce the wave plate into the polarizer and analyzer. Continuously rotate the wave plate and record the energy received by the power meter at this time. Find the point where the power meter has maximum energy, at which the optical axes of the polarizer, wave plate, and analyzer are parallel. Record the position of the optical axis for subsequent testing.

[0116] (3) Perform polarization state tests on half-wave plates and quarter-wave plates. Rotate the polarizer so that the light vector of the incident linearly polarized light forms a certain angle with the optical axis of the wave plate. Then rotate the analyzer and test the energy corresponding to different rotation angles to record the polarization state of the output light.

[0117] The test results of 633nm zero-order SiO2 crystal 1 / 2 wave plate are as follows Figure 8As shown in (a)-(h), θ and φ correspond to the rotation angles of the polarizer and analyzer relative to the horizontal line, respectively. When linearly polarized light passes through the half-wave plate, the output light is still linearly polarized light, but the polarization direction is rotated by θ relative to the fast axis of the wave plate. When θ=45°, the polarization direction of linearly polarized light after passing through the half-wave plate is rotated by 90° relative to before passing through the half-wave plate. When θ=150°, the polarization direction of linearly polarized light after passing through the half-wave plate is rotated by 150° relative to the optical axis of the wave plate. The output light power received by the power meter and the rotation angle of the analyzer are in accordance with Malus's law, indicating that the zero-order wave plate device prepared by the present invention has excellent polarization state control capabilities.

[0118] In one or more embodiments, a zero-order wave plate is further provided, which is prepared using the steps of the method for preparing a thickness-adjustable zero-order wave plate for full-band applications as described in any of the above embodiments. The prepared zero-order wave plates of different operating wavelengths are shown in Table 1.

[0119] Table 1 Prepared zero-order wave plates with different working wavelengths;

[0120]

[0121] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing a thickness-adjustable zero-order wave plate for full-band applications, characterized in that: include: Select the working band of the zero-order wave plate device to be prepared, determine the crystal material corresponding to the working band, and then calculate the spatial distribution data of the birefringence of the crystal corresponding to the working band; Based on the refractive index ellipsoid equation, the anisotropic refractive index generated by the light vector incident on the anisotropic crystal at any angle is solved, and the birefringence of the biaxial crystal and the uniaxial crystal under different incidence conditions is determined by combining the crystal refractive index dispersion equation, and is used as the birefringence spatial distribution data; When light waves are incident along any angle (θ, φ), the resulting birefringence is given by the formula: To solve, ； ； ； and are the refractive indices of slow light and fast light propagating in the biaxial crystal, θ and φ are the directions of the incident light in the spherical coordinate system, The direction is the vibration direction of the electric displacement vector D1 of the slow light, is the vibration direction of the electric displacement vector D2 of the fast light, for and Shaft winding Axis rotation angle; 、 The coefficient of the term must be equal to 0, so we can solve it: ； According to the spatial distribution data of the birefringence of the crystal in the corresponding working band, the theoretical thickness of the zero-order wave plate device in the current working band corresponding to different light incident directions is calculated; According to the theoretical thickness of the zero-order wave plate device in the current working band, the crystal cutting angle of the zero-order wave plate device of the current working wavelength is determined; The crystal is cut according to the determined crystal cutting angle and the theoretical thickness of the zero-order wave plate device to obtain an initial zero-order wave plate device; The thickness of the initial zero-order wave plate device is gradually adjusted to perform phase delay correction on the adjusted initial zero-order wave plate device until the phase delay error is 0, thereby preparing the final zero-order wave plate.

2. The method for preparing a thickness-adjustable zero-order wave plate for full-band applications according to claim 1, wherein: Birefringence is a function of the direction of incidence.

3. The method for preparing a thickness-adjustable zero-order wave plate for full-band applications according to claim 1, wherein: When light propagates in a crystal along a set direction, the resulting birefringence is zero, and this direction is the optical axis in the crystal.

4. The method for preparing a thickness-adjustable zero-order wave plate for full-band applications according to claim 1, wherein: The calculation formula for the theoretical thickness of the zero-order wave plate device is: ； in, is the theoretical thickness of the zero-order wave plate device; is the wavelength of the incident light; is the birefringence; is the phase delay difference.

5. The method for preparing a thickness-adjustable zero-order wave plate for full-band applications according to claim 1, wherein: The crystal material for ultraviolet to near infrared bands adopts at least one of borate, silicate and fluoride.

6. The method for preparing a thickness-adjustable zero-order wave plate for full-band applications according to claim 1, wherein: The crystal material for the mid-infrared band is at least one of phosphate, niobate, molybdate, tantalate, gallate, titanate, tellurate and tungstate.

7. The method for preparing a thickness-adjustable zero-order wave plate for full-band applications according to claim 1, wherein: The crystal material for the far infrared band is at least one of sulfide, selenide and phosphide.

8. A zero-order wave plate, characterized in that: The zero-order wave plate with adjustable thickness for full-band application is prepared by the method described in any one of claims 1 to 7.

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