Broadband pulse light frequency doubling device based on PPLN waveguide

Abstract

The utility model discloses a broadband pulse light frequency doubling device based on PPLN waveguide, which comprises an optical fiber coupling module, a frequency doubling waveguide module, a collimating lens and a dispersion compensation module, the frequency doubling waveguide module is a lithium niobate crystal PPLN waveguide, the optical fiber coupling module is used for converting fundamental frequency light with the central wavelength of lambda1 into focused space light, and the dispersion compensation module is used for compensating the frequency doubling waveguide module. The frequency doubling waveguide module is used for converting the focused spatial light into frequency doubling light with the central wavelength of lambda2, outputting the frequency doubling light and then enabling the frequency doubling light to enter the collimating lens to be converted into a collimated light beam; and the dispersion compensation module is used for outputting the frequency doubling light after pulse width compression. The problem that the frequency multiplication technology in ultrafast optics cannot give consideration to the frequency multiplication efficiency and the frequency multiplication light beam quality at the same time is solved, the frequency multiplication technology can complete frequency conversion with high quality in practical application, and the field of ultrafast optical frequency multiplication is expanded. The problem of dispersion broadening in waveguide frequency doubling is solved, the dispersion compensation amount is adjustable, and the device can be matched with different frequency doubling crystals for use.

Description

Technical Field

[0001] The utility model belongs to the technical field of ultrafast optical frequency doubling, and in particular relates to a broadband pulse light frequency doubling device based on a PPLN waveguide. Technical Background

[0002] Ultrafast optics is an emerging field in optical science, which mainly studies the ultrafast phenomena of light. The application of ultrafast optics is very extensive, including the study of ultrafast dynamic processes of matter, ultrafast spectroscopy technology, ultrafast imaging technology and ultrafast laser micromachining. Among them, the study of ultrafast dynamic processes of matter is one of the important applications of ultrafast optics. Through femtosecond laser pulses, we can observe and study the dynamic changes of the electronic state and vibrational state of matter in real time. Ultrafast spectroscopy technology uses femtosecond laser pulses for spectral measurement to obtain the spectral information of the material. Ultrafast imaging technology uses femtosecond laser pulses for imaging, which can achieve ultra-high speed imaging. Ultrafast laser micromachining uses femtosecond laser pulses for micron-level precision processing, which can produce micron-level structures on the surfaces of various materials.

[0003] From the application of ultrafast optics, we can know that the birth background of this field is closely related to the development of laser technology. In ultrafast optics, one of the most important theories is the generation and propagation of femtosecond laser pulses, that is, ultrashort optical pulse technology. However, current lasers cannot produce arbitrary wavelength outputs, because the output wavelength of the laser is generally determined by the energy level structure of the microscopic particles in the gain medium. To obtain a larger spectral range, optical frequency conversion is the most direct means, especially through frequency doubling, tripling, quadrupling, etc., it is possible to enter the short wavelength range, which greatly expands the application field of ultrashort pulses.

[0004] The frequency conversion of ultrashort pulses is different from that of narrowband lasers. The fundamental reason is that the spectrum of ultrashort pulses is wide and contains multiple frequency components. The group velocities of each frequency component are different. Therefore, when using ultrashort pulses to achieve frequency conversion, the problems of phase mismatch and group velocity mismatch must be considered at the same time. Both will cause a decrease in frequency conversion efficiency and a change in the quality of the light beam. This is also a problem that needs to be solved in the broadband frequency doubling process. The quasi-phase matching technology based on periodically polarized crystals can design a reasonable polarization period according to actual needs, maximize the use of the effective nonlinear coefficient of the nonlinear optical crystal, and achieve matching in the selected direction, making it have a very high conversion efficiency. However, the broadening of the frequency-doubled optical pulse caused by group velocity mismatch cannot be solved.

[0005] Lithium niobate crystal PPLN has large electro-optical, acousto-optical and nonlinear optical coefficients, stable physical and chemical properties, low crystal production cost and easy to generate large-sized single crystals, so it is widely used in the preparation of various optical waveguide devices and has become a commonly used inorganic dielectric crystal material in optoelectronics and integrated optics. At present, optical waveguide devices based on lithium niobate substrate are at a relatively mature stage. Therefore, a broadband pulse light frequency doubling device based on PPLN waveguide can be developed. Utility Model Content

[0006] In the case of ultrashort pulse frequency doubling, there are two matching conditions, namely phase-phase velocity matching and group velocity matching. Ideally, it is hoped that both conditions can be met at the same time, which is very beneficial to the frequency doubling process. But in reality, it is very difficult to meet the above two matching conditions at the same time, and in most cases it is impossible. The usual practice is to first meet the phase matching condition, and at the same time use a relatively short frequency doubling crystal to reduce the impact of group velocity mismatch, thereby avoiding severe pulse width broadening. This method only takes the middle value for both frequency doubling efficiency and beam quality, and cannot simultaneously obtain the highest frequency doubling efficiency and the best beam quality.

[0007] Based on the above problems, the purpose of the utility model is to propose a broadband pulse light frequency doubling device based on PPLN waveguide, which can perform dispersion compensation for the broadened pulse while ensuring the maximum frequency doubling efficiency.

[0008] In order to solve the above problems, the technical solution adopted by the utility model is:

[0009] A broadband pulse light frequency doubling device based on PPLN waveguide comprises a fiber coupling module, a frequency doubling waveguide module, a collimating lens and a dispersion compensation module. The frequency doubling waveguide module is a lithium niobate crystal PPLN waveguide. The fiber coupling module is used to convert fundamental frequency light with a central wavelength of λ1 into focused spatial light. The frequency doubling waveguide module is used to convert the focused spatial light into frequency doubling light with a central wavelength of λ2, which is then output and enters the collimating lens to be converted into a collimated light beam. The dispersion compensation module is used to compress the pulse width and then output it.

[0010] The fiber coupling module is composed of a fiber collimator and a focusing lens. The fiber collimator is used to collimate the light, and the focusing lens is used to focus the collimated light.

[0011] As an implementation method, the dispersion compensation module includes a double Amici prism and a silicon-based liquid crystal spatial light modulator. The double Amici prism is composed of an upright Amici prism and an inverted Amici prism. The silicon-based liquid crystal spatial light modulator is placed between the two Amici prisms. The Amici prism is composed of two triangular prisms, an equilateral prism and a Littrow dispersion prism. The rectangular surface of the equilateral prism is close to the largest rectangular surface of the Littrow dispersion prism but not in contact. The light enters the upright Amici prism parallel to the bottom surface of the equilateral dispersion prism, is emitted perpendicular to the surface of the Littrow dispersion prism, enters the liquid crystal spatial light modulator, and then vertically enters the Littrow dispersion prism of the inverted Amici prism.

[0012] The Littrow dispersion prism is fixed on a movable bracket, and the movable bracket is used to drive the Littrow dispersion prism to move up and down along the interface between the two prisms.

[0013] The dispersion compensation module also includes a pulse width monitoring unit and a main controller. The main controller is connected to the pulse width monitoring unit and the silicon-based liquid crystal spatial light modulator respectively. The pulse width monitoring unit is used to monitor the display pulse width in real time and feed it back to the main controller. The main controller adjusts the voltage applied to the liquid crystal spatial light modulator according to the pulse width, and adaptively adjusts the dispersion amount by adjusting the applied electric field strength.

[0014] As another implementation method, the dispersion compensation module includes an Amisi prism, a first reflector, a second reflector, and a hollow 90-degree corner cone prism. The hollow 90-degree corner cone prism is composed of three mutually perpendicular reflecting surfaces, and the three reflecting surfaces are connected in pairs to form a hollow structure. The three reflecting surfaces are all coated with anti-reflection films. The first reflector and the second reflector are placed on the outside of the equilateral prism of the Amisi prism, and the hollow 90-degree corner cone prism is placed on the outside of the Littrow dispersion prism of the Amisi prism 7. After the light is reflected by the first reflector, it enters the Amisi prism parallel to the bottom surface of the equilateral dispersion prism and then is emitted perpendicular to the surface of the Littrow dispersion prism. After entering the hollow 90-degree corner cone prism and being reflected in turn by its three reflecting surfaces, the reflected light of the hollow 90-degree corner cone prism 10 is parallel to the incident light, returns to the Amisi prism, and is then reflected and emitted by the second reflector.

[0015] As another implementation, the dispersion compensation module includes an Amisi prism, a first reflector, a second reflector and a hollow 90-degree corner cube prism, the hollow 90-degree corner cube prism is divided into n hollow 90-degree corner cube prisms A and m hollow 90-degree corner cube prisms B, the n hollow 90-degree corner cube prisms A are arranged in sequence outside the Littrow dispersion prism of the Amisi prism, and are respectively the first hollow 90-degree corner cube prism A, the second hollow 90-degree corner cube prism A, the third hollow 90-degree corner cube prism A... and the nth hollow 90-degree corner cube prism A, and the m hollow 90-degree corner cube prisms B are arranged in sequence outside the equilateral prism of the Amisi prism, and are respectively the first hollow 90-degree corner cube prism B, the second hollow 90-degree corner cube prism B, the third hollow 90-degree corner cube prism degree corner cube B... and the mth hollow 90 degree corner cube B, nm=1, m and n are both positive integers, the light is incident on the first reflector parallel to the bottom surface of the equilateral prism, and after reflection, it enters the Amisi prism parallel to the bottom surface of the equilateral prism and then is emitted in a direction perpendicular to the surface of the Littrow dispersion prism in the Amisi prism, enters the first hollow 90 degree corner cube A, is reflected back to the Amisi prism, enters the first hollow 90 degree corner cube B, is reflected back to the Amisi prism, enters the second hollow 90 degree corner cube A, is reflected back to the Amisi prism, enters the second hollow 90 degree corner cube B, and so on and so forth until it enters the nth hollow 90 degree corner cube A, is reflected back to the Amisi prism, and finally is reflected and emitted by the second reflector 11.

[0016] The dispersion compensation module also includes a rotating mirror frame and an XY translation stage. The hollow 90-degree corner cube prism is installed in the rotating mirror frame, and the rotating mirror frame is installed on the XY translation stage. The rotating mirror frame is used to drive the hollow 90-degree corner cube prism to rotate 360° on a plane perpendicular to its incident light, and the XY translation stage is used to drive the hollow 90-degree corner cube prism to move in the X and Y directions of the plane perpendicular to its incident light.

[0017] The dispersion compensation module also includes a multidimensional adjustment frame, on which the first reflector and the second reflector are fixed. The multidimensional adjustment frame is used to adjust the first reflector and the second reflector in three directions: front, back, left, right, and up and down to adapt to the position of the incident light and the light after dispersion compensation.

[0018] Compared with the prior art, the utility model has the following advantages: the utility model solves the problem that the frequency doubling technology in ultrafast optics cannot take into account both the frequency doubling efficiency and the quality of the frequency doubling light beam at the same time, so that the frequency doubling technology can complete the frequency conversion with high quality in practical applications, and expands the field of ultrafast optical frequency doubling; the dispersion broadening problem in waveguide frequency doubling is solved, the dispersion compensation amount is adjustable, and it can be used in combination with different frequency doubling crystals. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of the structure of the broadband pulse light frequency doubling device based on PPLN waveguide involved in Example 1.

[0020] Figure 2 This is a schematic diagram of the structure of the dispersion compensation module involved in Example 1.

[0021] Figure 3 This is a schematic diagram of the structure of the dispersion compensation module involved in Example 1.

[0022] Figure 4 This is a schematic diagram of the structure of the dispersion compensation module involved in Example 1. DETAILED DESCRIPTION

[0023] In order to more clearly explain the content of the utility model, the utility model is further described below in conjunction with the drawings and specific embodiments. The first, second, etc. involved in this embodiment are only for distinguishing and explaining the components and do not constitute a limitation on the scope of protection.

[0024] Example 1

[0025] The frequency conversion efficiency of a focused Gaussian beam is expressed as the ratio of the frequency-doubled optical power (P2) to the fundamental optical power (P1):

[0026]

[0027] Where:

[0028] d eff ——The second-order nonlinear coefficient of the crystal;

[0029] L – length of the crystal;

[0030] P1——Intensity of fundamental frequency light;

[0031] n1——refractive index of fundamental frequency light in the crystal;

[0032] n2——the refractive index of the frequency-doubled light in the crystal;

[0033] ε0——vacuum dielectric constant, 8.854*10-12F / m;

[0034] λ1——wavelength of fundamental frequency light;

[0035] w0——beam waist radius of fundamental frequency light;

[0036] From formula (1), we can see that the frequency conversion efficiency of PPLN crystal is related to the optical power density intensity Therefore, PPLN crystal is made into a waveguide structure, and its strong optical confinement effect is used to focus and confine the light within a smaller aperture, which greatly enhances the optical power density, thereby greatly improving its optical conversion efficiency and broadening its application under low pump power. Therefore, in order to achieve higher frequency doubling efficiency, we will select waveguide materials as the main components of the frequency doubling module.

[0037] From formula (1), we can see that the frequency doubling conversion efficiency is proportional to the square of the crystal length and inversely proportional to the square of the fundamental wave optical waist. However, it does not mean that the longer the crystal length and the smaller the optical waist, the higher the conversion efficiency. There is a certain restrictive relationship between the crystal length and the spot size. From the confocal conditions, we can see that when When , the conversion efficiency reaches its maximum value, then the frequency doubling conversion efficiency formula can be simplified to

[0038]

[0039] It can be seen from formula (2) that the frequency doubling conversion efficiency is linearly related to the crystal length L.

[0040] Different parts of the broadband spectrum of the femtosecond laser pulse propagate at different speeds and are separated from each other in time, forming dispersion. In other words, the longer the length of the waveguide material, the higher the frequency doubling efficiency, and the greater the broadening of the frequency doubling light pulse. Taking the quasi-phase matching of the PPLN waveguide as an example, the input light is a femtosecond pulse light with a central wavelength of 1560nm, and after frequency doubling, it is a femtosecond pulse light of 780nm, and positive dispersion is introduced inside the PPLN, so that the pulse width of the 780nm light is broadened. In addition, the waveguide structure is formed by locally increasing the refractive index of the matrix crystal, which also makes the dispersion of the waveguide material larger. Then it is necessary to introduce negative dispersion into the dispersion compensation module for compensation without changing the propagation direction, so that the optical path continues to be coupled to other devices. For this reason, the utility model adds a dispersion compensation module after the frequency doubling waveguide module.

[0041] like Figure 1 As shown, the broadband pulse light frequency doubling device based on PPLN waveguide involved in this embodiment includes a fiber coupling module 1, a frequency doubling waveguide module 4, a collimating lens 5 and a dispersion compensation module 6. The frequency doubling waveguide module 4 is a lithium niobate crystal PPLN waveguide. The fiber coupling module 1 is used to convert the fundamental frequency light with a central wavelength of λ1 into focused spatial light. The frequency doubling waveguide module 4 is used to convert the focused spatial light into a frequency doubling light with a central wavelength of λ2 and then output it to the collimating lens 5 to convert it into a collimated light beam. The dispersion compensation module 6 is used to compress the pulse width and then output it. After that, focusing lenses, homogenizing mirrors, fiber couplers, etc. can be added according to needs for the next step of use.

[0042] The fiber coupling module 1 is composed of a fiber collimator 2 and a focusing lens 3. The focusing lens 3 is a double-cemented achromatic lens, which focuses the Gaussian beam into a small spot with good spot quality and enters the frequency doubling waveguide module 4 to improve the frequency doubling efficiency.

[0043] The frequency doubling waveguide module 4 integrates a temperature control unit, which controls the polarization period and operating temperature of the waveguide in the frequency doubling waveguide module to ensure stable conversion efficiency at the central wavelength.

[0044] like Figure 2 The dispersion compensation module 6 includes a double Amisi prism and a silicon-based liquid crystal spatial light modulator 8. The double Amisi prism is composed of a positive Amisi prism 7 and an inverted Amisi prism 7. The silicon-based liquid crystal spatial light modulator 8 is placed between the two Amisi prisms 7. The Amisi prism 7 is composed of two triangular prisms, an equilateral prism 701 and a Littrow dispersion prism 702. The rectangular surface of the equilateral prism 701 is close to the largest rectangular surface of the Littrow dispersion prism 702 but does not fit. The light enters the positive Amisi prism parallel to the bottom surface of the equilateral dispersion prism 701. The laser beam is first refracted when entering the Amici prism, then enters the interface between the two prisms, and then is emitted in a direction almost perpendicular to the surface of the Littrow dispersion prism 702, so that the light of different frequency components is sequentially distributed in space, and the liquid crystal spatial light modulator 8 located in the middle modulates the light of different frequency components independently, and then the laser beam is vertically incident into the inverted Amici prism Littrow dispersion prism 702, and then enters the interface between the two prisms for reflection and refraction, and finally the light emitted by the equilateral prism 701 is parallel to the incident light of the dispersion compensation module 6. At this point, the dispersion compensation of the incident laser beam is completed.

[0045] The Littrow dispersion prism 702 is fixed on a movable bracket, and the movable bracket drives the Littrow dispersion prism 702 to move up and down along the interface between the two prisms. The dispersion amount can be adjusted by moving the Littrow dispersion prism 702, which can be used for pulse broadening or pulse compression.

[0046] Specifically, the equilateral prism 701 is usually made of crown glass with medium dispersion power, and the Littrow dispersion prism 702 is made of flint glass with high dispersion power. The refractive index needs to be calculated based on different light sources.

[0047] The dispersion compensation module 6 also includes a pulse width monitoring unit and a main controller, and the main controller is connected to the pulse width monitoring unit and the silicon-based liquid crystal spatial light modulator 8 respectively, wherein the pulse width monitoring unit monitors the display pulse width in real time and feeds back to the main controller, and the main controller adjusts the voltage applied to the liquid crystal spatial light modulator according to the pulse width, and adaptively adjusts the dispersion amount by adjusting the applied electric field strength.

[0048] Example 2

[0049] Except for the dispersion compensation module 6, the other parts of this embodiment are the same as those of the first embodiment.

[0050] like Figure 3The dispersion compensation module 6 includes an Amisi prism 7, a first reflector 9, a second reflector 11, and a hollow 90-degree corner cube prism 10. The hollow 90-degree corner cube prism 10 is composed of three mutually perpendicular reflection surfaces, and the three reflection surfaces are connected in pairs to form a hollow structure. The three reflection surfaces are all coated with anti-reflection films. The first reflector 9 and the second reflector 11 are placed outside the equilateral prism 701 of the Amisi prism 7, and the hollow 90-degree corner cube prism 10 is placed outside the Littrow dispersion prism 702 of the Amisi prism 7.

[0051] After being reflected by the first reflector 9, the light enters the Amisi prism 7 parallel to the bottom surface of the equilateral dispersion prism 701 and is emitted in a direction almost perpendicular to the surface of the Littrow dispersion prism 702 in the Amisi prism 7. After entering the hollow 90-degree corner cube prism 10 and being reflected in sequence by its three reflecting surfaces, the reflected light of the hollow 90-degree corner cube prism 10 is parallel to the incident light, returns to the Amisi prism 7, and is then reflected and emitted by the second reflector 11.

[0052] Among them, the hollow 90-degree corner cube combines three reflectors at 90 degrees to ensure that the light path is accurately reversed by 180 degrees, and the three surfaces are coated with anti-reflection film to reduce the loss of optical power; the light beam in the hollow 90-degree corner cube is externally reflected on all surfaces, thus avoiding the wavelength dispersion and optical path change caused by the light beam entering the glass from the air in the ordinary corner cube. The hollow 90-degree corner cube can be a patent number of CN102736234A. Figure 2 (a) The hollow cube corner mirror involved.

[0053] The dispersion compensation module 6 also includes a rotating mirror frame and an XY translation stage. The hollow 90-degree corner cube prism 10 is installed in the rotating mirror frame. The rotating mirror frame is installed on the XY translation stage. The rotating mirror frame is used to drive the hollow 90-degree corner cube prism 10 to rotate 360 ​​degrees on a plane perpendicular to the incident light. The XY translation stage is used to drive the hollow 90-degree corner cube prism 10 to move along the X direction and Y direction of the plane perpendicular to the incident light. The XY translation stage and the rotating mirror frame drive the movement and rotation of the hollow 90-degree corner cube prism, thereby changing the position where the light enters the Amisi prism, thereby adjusting the dispersion amount.

[0054] The dispersion compensation module 6 also includes a multidimensional adjustment frame, on which the first reflector 9 and the second reflector 11 are fixed. The multidimensional adjustment frame is used to adjust the first reflector 9 and the second reflector 11 to move in three directions, front and back, left and right, and up and down, to adapt to the position of the incident light and the light after dispersion compensation, and to accurately reflect the light.

[0055] Among them, the Littrow dispersion prism 702 involved in this embodiment can also be fixed on a movable bracket, and the movable bracket drives the Littrow dispersion prism 702 to move up and down along the interface between the two prisms, and the dispersion amount is adjusted by moving the Littrow dispersion prism 702.

[0056] Example 3

[0057] Except for the dispersion compensation module 6, the other parts of this embodiment are the same as those of the first embodiment.

[0058] like Figure 4 The dispersion compensation module 6 includes an Amisi prism 7, a first reflector 9, a second reflector 11 and a hollow 90-degree corner cube prism 10. The hollow 90-degree corner cube prism 10 is divided into n hollow 90-degree corner cube prisms A 101 and m hollow 90-degree corner cube prisms B 102. The n hollow 90-degree corner cube prisms A 101 are sequentially arranged outside the Littrow dispersion prism 702 of the Amisi prism 7, and are respectively a first hollow 90-degree corner cube prism A 1011, a second hollow 90-degree corner cube prism A 1012, a third hollow 90-degree corner cube prism A 1013... and an nth hollow 90-degree corner cube prism A 101n.

[0059] m hollow 90-degree corner cube prisms B102 are sequentially arranged outside the equilateral prism 701 of the Amisi prism 7, namely, a first hollow 90-degree corner cube prism B1021, a second hollow 90-degree corner cube prism B1022, a third hollow 90-degree corner cube prism B1023, ... and an m-th hollow 90-degree corner cube prism B102m, nm=1, m and n are both positive integers,

[0060] The light is incident on the first reflector 9 parallel to the bottom surface of the equilateral prism 701, and after reflection, it enters the Amisi prism 7 parallel to the bottom surface of the equilateral prism 701, and then is emitted in a direction almost perpendicular to the surface of the Littrow dispersion prism 702 in the Amisi prism 7, enters the first hollow 90-degree corner cube prism A 1011, is reflected back to the Amisi prism 7, enters the first hollow 90-degree corner cube prism B 1021, is reflected back to the Amisi prism 7, enters the second hollow 90-degree corner cube prism A 1012, is reflected back to the Amisi prism 7, enters the second hollow 90-degree corner cube prism B 1022, and so on until it enters the nth hollow 90-degree corner cube prism A 101n, is reflected back to the Amisi prism 7, and finally is reflected and emitted by the second reflector 11. The light passes through two rows of n hollow 90-degree corner cube prisms A 101 and m hollow 90-degree corner cube prisms B 102 placed in parallel, and can be reflected multiple times in the Amici prism to perform multiple dispersion compensations.

Claims

1. A broadband pulse light frequency doubling device based on a PPLN waveguide, characterized in that: It includes a fiber coupling module, a frequency doubling waveguide module, a collimating lens and a dispersion compensation module. The frequency doubling waveguide module is a lithium niobate crystal PPLN waveguide. The fiber coupling module is used to convert fundamental frequency light with a central wavelength of λ1 into focused spatial light. The frequency doubling waveguide module is used to convert the focused spatial light into frequency doubling light with a central wavelength of λ2, which is then output to the collimating lens and converted into a collimated light beam. The dispersion compensation module is used to compress the pulse width and then output it.

2. The broadband pulse light frequency doubling device based on PPLN waveguide according to claim 1, characterized in that: The fiber coupling module consists of a fiber collimator and a focusing lens. The fiber collimator is used to collimate the light, and the focusing lens is used to focus the collimated light.

3. The broadband pulse light frequency doubling device based on PPLN waveguide according to claim 1, characterized in that: The dispersion compensation module includes a double Amisi prism and a silicon-based liquid crystal spatial light modulator. The double Amisi prism is composed of an upright Amisi prism and an inverted Amisi prism. The silicon-based liquid crystal spatial light modulator is placed between the two Amisi prisms. The Amisi prism is composed of two triangular prisms, an equilateral prism and a Littrow dispersion prism. The rectangular surface of the equilateral prism is close to the largest rectangular surface of the Littrow dispersion prism but not in contact. The light enters the upright Amisi prism parallel to the bottom surface of the equilateral dispersion prism, is emitted perpendicular to the surface of the Littrow dispersion prism, enters the liquid crystal spatial light modulator, and then vertically enters the Littrow dispersion prism of the inverted Amisi prism.

4. The broadband pulse light frequency doubling device based on PPLN waveguide according to claim 1, characterized in that: The dispersion compensation module includes an Amisi prism, a first reflector, a second reflector and a hollow 90-degree corner cube prism. The Amisi prism is composed of two triangular prisms, an equilateral prism and a Littrow dispersion prism. The rectangular surface of the equilateral prism is close to the largest rectangular surface of the Littrow dispersion prism but not fitted. The hollow 90-degree corner cube prism is composed of three mutually perpendicular reflective surfaces, which are connected in pairs to form a hollow structure. The three reflective surfaces are all coated with anti-reflection films. The first reflector and the second reflector are placed On the outside of the equilateral prism of the Amisi prism, a hollow 90-degree corner cube is placed on the outside of the Littrow dispersion prism of the Amisi prism. After being reflected by the first reflector, the light enters the Amisi prism parallel to the bottom surface of the equilateral dispersion prism and then is emitted perpendicular to the surface of the Littrow dispersion prism. After entering the hollow 90-degree corner cube and being reflected by its three reflecting surfaces in turn, the reflected light of the hollow 90-degree corner cube is parallel to the incident light, returns to the Amisi prism, and is then reflected and emitted by the second reflector.

5. The broadband pulse light frequency doubling device based on PPLN waveguide according to claim 1, characterized in that: The dispersion compensation module includes an Amisi prism, a first reflector, a second reflector and a hollow 90-degree corner cube prism. The Amisi prism is composed of two triangular prisms, an equilateral prism and a Littrow dispersion prism. The rectangular surface of the equilateral prism is close to the largest rectangular surface of the Littrow dispersion prism but not fitted. The hollow 90-degree corner cube prism is divided into n hollow 90-degree corner cube prisms A and m hollow 90-degree corner cube prisms B. The n hollow 90-degree corner cube prisms A are sequentially arranged outside the Littrow dispersion prism of the Amisi prism, namely the first hollow 90-degree corner cube prism A, the second hollow 90-degree corner cube prism A, the third hollow 90-degree corner cube prism A... and the nth hollow 90-degree corner cube prism A. The m hollow 90-degree corner cube prisms B are sequentially arranged outside the equilateral prism of the Amisi prism, namely the first hollow 90-degree corner cube prism Cone prism B, the second hollow 90 degree corner cube prism B, the third hollow 90 degree corner cube prism B... and the mth hollow 90 degree corner cube prism B, nm=1, m and n are both positive integers, the light is incident on the first reflector parallel to the bottom surface of the equilateral prism, and after reflection, it enters the Amisi prism parallel to the bottom surface of the equilateral prism and then emits in a direction perpendicular to the surface of the Littrow dispersion prism in the Amisi prism, enters the first hollow 90 degree corner cube prism A, is reflected back to the Amisi prism, enters the first hollow 90 degree corner cube prism B, is reflected back to the Amisi prism, enters the second hollow 90 degree corner cube prism A, is reflected back to the Amisi prism, enters the second hollow 90 degree corner cube prism B, and repeats until it enters the nth hollow 90 degree corner cube prism A, is reflected back to the Amisi prism, and finally is reflected and emitted through the second reflector.

6. The broadband pulse light frequency doubling device based on PPLN waveguide according to claim 4 or 5, characterized in that: The dispersion compensation module also includes a rotating mirror frame and an XY translation stage. The hollow 90-degree corner cube prism is installed in the rotating mirror frame, and the rotating mirror frame is installed on the XY translation stage. The rotating mirror frame is used to drive the hollow 90-degree corner cube prism to rotate 360° on a plane perpendicular to its incident light, and the XY translation stage is used to drive the hollow 90-degree corner cube prism to move in the X and Y directions of the plane perpendicular to its incident light.

7. The broadband pulse light frequency doubling device based on PPLN waveguide according to claim 4 or 5, characterized in that: The dispersion compensation module also includes a multidimensional adjustment frame, on which the first reflector and the second reflector are fixed. The multidimensional adjustment frame is used to adjust the first reflector and the second reflector in three directions: front, back, left, right, and up and down to adapt to the position of the incident light and the light after dispersion compensation.

8. The broadband pulse light frequency doubling device based on PPLN waveguide according to claim 3, 4 or 5, characterized in that: The Littrow dispersion prism is fixed on a movable bracket, and the movable bracket is used to drive the Littrow dispersion prism to move up and down along the interface between the two prisms.

9. The broadband pulse light frequency doubling device based on PPLN waveguide according to claim 3, 4 or 5, characterized in that: The dispersion compensation module also includes a pulse width monitoring unit and a main controller. The main controller is connected to the pulse width monitoring unit and the silicon-based liquid crystal spatial light modulator respectively. The pulse width monitoring unit is used to monitor the display pulse width in real time and feed it back to the main controller. The main controller adjusts the voltage applied to the liquid crystal spatial light modulator according to the pulse width, and adaptively adjusts the dispersion amount by adjusting the applied electric field strength.

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