Frequency doubling laser line width narrowing device

Abstract

The utility model provides a frequency-doubled laser linewidth narrowing device. The device comprises a pumping module and a laser resonant cavity, the pumping module is used for providing linearly polarized light in a specific polarization direction to a light path; the laser resonant cavity is internally provided with a gain medium, at least one birefringence optical filter and a frequency doubling crystal which are sequentially arranged along an optical path, and the at least one birefringence optical filter is inserted into the optical path at a Brewster angle; wherein the linearly polarized light is focused in the gain medium, the central wavelength of the linearly polarized light is the same as the absorption peak wavelength of the gain medium, and the polarization direction of the linearly polarized light is the same as the maximum absorption direction of the gain medium. According to the invention, the birefringence optical filter (group) inserted into the laser resonant cavity can be specifically adjusted, so that narrow-band filtering can be conveniently and quickly realized in various intracavity frequency doubling lasers, and compared with the prior art, the introduced power loss is relatively small.

Description

Technical Field

[0001] This disclosure relates to the field of optoelectronic technology, specifically to a frequency doubling laser linewidth narrowing device. Background Technology

[0002] All-solid-state continuous narrow-linewidth lasers possess advantages such as good monochromaticity, low noise, high beam quality, and high stability, and are widely used in fields such as precision measurement, hyperfine spectroscopy, cold atom physics, quantum communication, lidar, laser remote sensing, and materials processing. Output linewidth is one of the important parameters for evaluating the performance of solid-state lasers, directly affecting the coherence of the laser and its performance in specific applications.

[0003] With the development of science and technology and the deepening of basic research, higher requirements have been placed on the output spectral linewidth of all-solid-state lasers. The main factors affecting the output linewidth of solid-state lasers include the characteristics of the gain medium, the design of the resonant cavity, the stability of the pump source, and external environmental factors. However, among these decisive factors, it is difficult to significantly change them after the laser's optical path is constructed. Therefore, it is necessary to use other optical components to compress the output spectral linewidth. As mentioned above, for all-solid-state lasers, most of the factors determining the output laser linewidth are determined at the initial design stage of the laser itself. Therefore, it is necessary to find suitable optical components to insert into the laser's optical path to achieve linewidth compression.

[0004] Most existing all-solid-state lasers do not incorporate linewidth compression elements because inserting additional optical components into the laser cavity would introduce significant power loss and reduce output power. Lasers without linewidth compression typically have a full width at half maximum (FWHM) in the nanometer range, resulting in lower spectral purity, poor monochromaticity, low peak density, and a lower signal-to-noise ratio, potentially failing to meet the requirements of certain applications.

[0005] Therefore, how to perform narrowband filtering on the output spectrum with relatively little power loss, thereby outputting a narrow-linewidth laser, is a technical problem that urgently needs to be solved in this field. Utility Model Content

[0006] The purpose of this application is to provide a frequency doubling laser linewidth narrowing device.

[0007] This application provides a frequency-doubled laser linewidth narrowing device, comprising:

[0008] A pump module is used to provide linearly polarized light with a specific polarization direction into the optical path;

[0009] A laser resonant cavity, wherein a gain medium, at least one birefringent filter and a frequency doubling crystal are arranged sequentially along the optical path, and the at least one birefringent filter is inserted into the optical path at Brewster angle;

[0010] The linearly polarized light is focused in the gain medium, the center wavelength of the linearly polarized light is the same as the absorption peak wavelength of the gain medium, and the polarization direction of the linearly polarized light is the same as the maximum absorption direction of the gain medium.

[0011] In some embodiments of this application, the number of birefringent filters is greater than one, and the thickness of all birefringent filters is in a preset ratio.

[0012] In some embodiments of this application, the gain medium is any one of the following solid-state laser crystals:

[0013] Nd:YVO4, Nd:YAG, Nd:YLF, Yb:YAG, Tm:YAG, Er:YAG and Cr 3+ :BeAl2O4.

[0014] In some embodiments of this application, the frequency doubling crystal is any one of the following:

[0015] KDP crystals, LBO crystals, and BBO crystals.

[0016] In some embodiments of this application, the linearly polarized light is focused at the center of the gain medium.

[0017] In some embodiments of this application, the laser resonant cavity is of any one of the following types:

[0018] Plane-to-planar critical cavity, plane-to-concave cavity, annular cavity, X-shaped cavity and V-shaped cavity.

[0019] In some embodiments of this application, the pumping module is pumped by side pumping.

[0020] In some embodiments of this application, the pumping method of the pumping module is end-face pumping.

[0021] Compared to existing technologies, the frequency-doubled laser linewidth narrowing device provided in this application includes a pump module and a laser resonant cavity. The pump module is used to provide linearly polarized light with a specific polarization direction into the optical path. The laser resonant cavity contains a gain medium, at least one birefringent filter, and a frequency-doubled crystal arranged sequentially along the optical path. The at least one birefringent filter is inserted into the optical path at a Brewster angle. The linearly polarized light is focused in the gain medium, the center wavelength of the linearly polarized light is the same as the absorption peak wavelength of the gain medium, and the polarization direction of the linearly polarized light is the same as the maximum absorption direction of the gain medium. This application can conveniently and quickly achieve narrowband filtering in various intracavity frequency-doubled lasers by specifically adjusting the birefringent filter (group) inserted into the laser resonant cavity. Compared to existing technologies, this application introduces less power loss. Attached Figure Description

[0022] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this disclosure. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0023] Figure 1 A schematic diagram of the structure of a frequency doubling laser linewidth narrowing device provided in this disclosure is shown;

[0024] Figure 2 A schematic diagram of another frequency-doubled laser linewidth narrowing device provided in this disclosure is shown;

[0025] Figure 3 A flowchart of a method for narrowing the linewidth of a frequency-doubled laser provided in this disclosure is shown;

[0026] Figure 4 A schematic diagram of the spectral linewidths obtained without using the apparatus of this application is shown;

[0027] Figure 5 A schematic diagram of the spectral linewidth obtained using the apparatus of this application is shown. Detailed Implementation

[0028] Embodiments of the present disclosure will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the disclosure. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concepts of the present disclosure.

[0029] The accompanying drawings illustrate various structural schematics according to embodiments of the present disclosure. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0030] In the context of this disclosure, when a layer / element is referred to as being "above" another layer / element, the layer / element may be directly above the other layer / element, or there may be an intermediate layer / element between them. Additionally, if a layer / element is "above" another layer / element in one orientation, then when the orientation is reversed, the layer / element may be "below" the other layer / element.

[0031] Most existing all-solid-state lasers do not incorporate linewidth compression optical elements for two reasons: first, conventional linewidth compression devices are inconvenient to adjust, making the entire system more complex and increasing its instability; second, inserting linewidth compression elements would increase power loss, leading to a decrease in output power. Therefore, a suitable method is needed to effectively narrow the output laser linewidth while minimizing the aforementioned drawbacks.

[0032] In view of this, embodiments of this application provide a frequency-doubled laser linewidth narrowing device and a frequency-doubled laser linewidth narrowing method, which will be described below with reference to the accompanying drawings.

[0033] Please refer to Figure 1 It shows a schematic diagram of the structure of a frequency doubling laser linewidth narrowing device provided in an embodiment of this application, such as... Figure 1 As shown, the device includes a pump module 100 and a laser resonant cavity 200.

[0034] The pump module 100 can provide linearly polarized light with a specific polarization direction into the optical path. The pump module 100 can be pumped from the end face or from the side; different pumping methods can be selected as long as the design is appropriate.

[0035] The laser resonant cavity 200 can be selected from various types, such as a planar-planar critical cavity, a planar-concave cavity, or a cavity composed of more mirrors, such as a ring cavity, an X-shaped cavity, or a V-shaped cavity, to suit specific needs.

[0036] like Figure 1As shown, the laser resonant cavity 200 is composed of a reflector 201 and a reflector 202. Inside the laser resonant cavity 200, there is a gain medium 300, at least one birefringent filter 400 and a frequency doubling crystal 500 arranged sequentially along the optical path. The at least one birefringent filter 400 is inserted into the optical path at Brewster angle.

[0037] The linearly polarized light provided by the pump module 100 is focused in the gain medium 300. Specifically, the focusing position can be at the center of the gain medium 300. The center wavelength of the linearly polarized light is the same as the absorption peak wavelength of the gain medium 300, and the polarization direction of the linearly polarized light is the same as the maximum absorption direction of the gain medium 300.

[0038] Specifically, the gain medium 300 can be Nd:YVO4, Nd:YAG, Nd:YLF, Yb:YAG, Tm:YAG, Er:YAG, and Cr. 3+ Solid-state laser crystals such as BeAl2O4.

[0039] Specifically, the frequency doubling crystal 500 can be a KDP crystal (potassium dihydrogen phosphate crystal), an LBO crystal (lithium triborate crystal), or a BBO crystal (barium metaborate crystal), etc.

[0040] like Figure 1 The working principle of the frequency doubling laser linewidth narrowing device shown is as follows:

[0041] The principle of narrowing linewidth using birefringent filters is based on the birefringence effect. When linearly polarized light passes through, the o-ray and e-ray produce a certain phase difference δ, which can be expressed as:

[0042]

[0043] Where, n e and n o Let represent the refractive indices of the e-ray and o-ray, respectively; d is the thickness of the birefringent filter; γ is the angle between the optical axis and the ordinary wave vector; λ is the laser wavelength; and θ represents the incident angle at Brewster's angle.

[0044] If the phase difference δ is an integer multiple of 2π, then the birefringent filter is equivalent to a full-wave plate. Lasers meeting this condition can be output without loss, and the peak transmission wavelength λ is:

[0045]

[0046] Where k represents the interference order. For fundamental and harmonic light, if the fundamental light can pass through completely, the harmonic light can theoretically also pass through completely, only the interference order k is twice. However, in reality, because the refractive index of light in a quartz crystal varies with wavelength, i.e., quartz crystals exhibit material dispersion, this can be expressed as follows:

[0047] n 2 =a0+a1·λ 2 +a2·λ -2 +a3·λ -4 +a4·λ -6 +a5·λ -8 ;

[0048] This results in the transmittance peaks of the fundamental and frequency-doubled light not completely corresponding, but rather offset to a certain extent. The linewidth compressed by the birefringent filter will be compressed again after frequency doubling. Thus, the birefringent filter 400 can simultaneously compress the spectral linewidths of both the fundamental and frequency-doubled lasers. The final output laser spectrum of the entire device should be influenced and generated by the combined effects of various components such as the laser crystal, birefringent filter, frequency-doubled crystal, and reflector. By finely adjusting the birefringent filter, the smaller the overlap between the main transmittance peaks of the fundamental and frequency-doubled light, the narrower the linewidth of the ultraviolet laser output can be produced. Furthermore, theoretical and experimental verification shows that the birefringent filter 400 inserted at the Brewster angle can significantly reduce the reflection of the fundamental p-polarized light, while also having a low reflectivity for the frequency-doubled s-polarized light (approximately 0.14). Therefore, the loss introduced by narrowing the spectral linewidth of the frequency-doubled laser in this application is relatively small.

[0049] By placing the designed birefringent filter 400 into the optical path at Brewster angle and rotating the birefringent filter around the surface normal, the position of the transmittance peak can be adjusted, thereby achieving the effect of narrowing the laser linewidth over a wide range of wavelengths.

[0050] Specifically, the birefringent filter 400 can be selected not only as a single birefringent filter of a certain thickness, but also as a combination of multiple birefringent filters with thicknesses in a certain ratio, such as 1:2:4 or 1:2:5:9. All birefringent filters are inserted into the laser resonant cavity with their surfaces and optical axes parallel to each other and at Brewster's angle. This can further narrow the output laser linewidth, but at the same time, there will be greater power loss. The advantages and disadvantages can be weighed and selected and designed according to specific needs.

[0051] One side of the laser resonator mirror 201 is coated with an anti-reflection film for the pump light band, and the other side is coated with a high-reflection film for the laser band. The mirror 202 is coated with a high-reflection film for the fundamental frequency band and an anti-reflection film for the frequency-doubled frequency band. After the frequency-doubled crystal 500 is correctly placed in the cavity, the birefringent filter 400 and the frequency-doubled crystal 500 are repeatedly adjusted to output a narrow-linewidth frequency-doubled laser.

[0052] This application achieves convenient and quick narrowband filtering in various intracavity frequency-doubled lasers by specifically adjusting the inserted birefringent filter (group), and also allows for tuning of the center wavelength of the output laser. When the designed birefringent filter is inserted into the optical path, the phase delay effect caused by birefringence gives the birefringent filter a unique transmittance curve for each wavelength band. Furthermore, rotating the birefringent filter around its surface normal allows adjustment of the position of the transmittance peak, thereby achieving laser linewidth narrowing and tuning over a wide wavelength range.

[0053] For ease of understanding, this application also provides, as follows: Figure 2 Another frequency-doubled laser linewidth narrowing device is shown, in which the laser resonator adopts a V-shaped folded cavity.

[0054] like Figure 2 The V-shaped folded cavity alexandrite intracavity frequency-doubled ultraviolet laser shown uses a single birefringent filter to narrow the output laser linewidth. The entire device includes a pump module 100, a pump light collimation system 110, half-wave plates 121 and 122, a polarizing beam splitter 130, a focusing mirror 140, laser resonator mirrors 601, 602 and 603, a gain medium 300, a single birefringent filter 400, and a frequency-doubled crystal 500.

[0055] The pump module 100 consists of a 638nm red LD (laser diode, with a maximum output power of 40W) and a coupling fiber. After the pump light is collimated by the collimation system 110, it is adjusted by the half-wave plate 121 to make the horizontal polarization component dominant. Then, after passing through the polarization beam splitter prism 130, the remaining light is almost entirely horizontally polarized linear light. The function of the half-wave plate 122 is to further finely adjust the polarization direction so that the polarization direction of the pump light is parallel to the maximum absorption axis of the subsequent gain medium, thereby improving the overall efficiency. The focusing lens 140 is a lens with a focal length of f = 50mm, which focuses the pump light. Reflectors 601, 602, and 603 together form a V-shaped folded cavity: Reflector 601 has a 638nm anti-reflection coating on its front side and a 756nm high-reflection coating on its rear side, achieving a reflectivity of 99.9%; Plano-concave reflector 602 is a laser output coupling mirror, with its concave surface coated with a high-transmission coating for the 378nm band and a high-reflection coating for the 756nm band at a 10° incident angle, and its radius of curvature RC = 150mm. Its planar surface is coated with a 378nm anti-reflection coating to allow the frequency-doubled ultraviolet laser to output at this location; Reflector 603 has high reflectivity for both 756nm and 378nm. 400 is emerald green crystal, i.e., Cr. 3+The BeAl2O4 crystal serves as the gain medium for the laser. A temperature control device is connected to ensure operational stability. Its b-axis is horizontally positioned, and the focusing lens 140 is adjusted to direct the linearly polarized pump light to the center of the gain medium for maximum absorption efficiency. A single-piece birefringent filter 400, with a certain thickness, is fixed to a waveplate holder and placed in the optical path at a Brewster angle. Its thickness can be adjusted to achieve the required linewidth; a thickness of 2mm is generally sufficient. The birefringent filter 400 is inserted at a Brewster angle between the reflector 602 and the frequency-doubling crystal 500. The frequency-doubling crystal 500 is a lithium triborate (LBO) crystal, with a cutting angle corresponding to the type I phase-matching angle for 756nm photon frequency doubling, and is connected to a water-cooling device to ensure operational stability.

[0056] First, the laser setup is adjusted to maximize the fundamental frequency power at mirror 603. Then, a birefringent filter 400 and a frequency doubling crystal 500 are added sequentially. The birefringent filter 400 is first positioned, its position and pitch angle adjusted, and it rotated to select the wavelength of the output fundamental frequency light. At this point, the spectral linewidth of the fundamental frequency light has been narrowed by the birefringent filter, resulting in higher monochromaticity of the fundamental frequency photons. Next, the frequency doubling crystal 500 is placed in the optical path. The frequency doubling crystal is connected to a temperature control device to ensure temperature stability. Its position and angle are then adjusted to achieve the phase-matching angle required to generate the second harmonic. The second harmonic generated at the frequency doubling crystal, after reflection by mirror 603, will pass again through the birefringent filter 400.

[0057] As explained above, the frequency-doubled spectrum will be compressed again by the birefringent filter 400, resulting in a narrow-linewidth frequency-doubled ultraviolet laser output at the reflector 602. The output spectrum can be measured using a spectrometer. Finally, by repeatedly adjusting the birefringent filter 400 and the frequency-doubled crystal 500 based on the output spectrum, a narrower frequency-doubled laser spectrum can be obtained. This application can achieve this by specifically adjusting the birefringent filter (group) inserted into the laser resonant cavity, so that the transmittance peaks of the fundamental and frequency-doubled light within the resonant cavity do not perfectly correspond. Thus, after the fundamental laser undergoes one linewidth compression, it is converted into a second harmonic and then compressed again by the same birefringent filter (group), ultimately resulting in a frequency-doubled laser with a significantly narrower spectral linewidth.

[0058] Therefore, based on the frequency-doubled laser linewidth narrowing device provided in the above embodiments, this application also provides a frequency-doubled laser linewidth narrowing method, please refer to... Figure 3 The figure shows a flowchart of a method for narrowing the linewidth of a frequency-doubled laser provided in an embodiment of this application. As shown, the method includes:

[0059] Step S101: Remove the birefringent filter and frequency doubling crystal from the laser resonant cavity into the optical path;

[0060] Step S102: Control the pump module to provide linearly polarized light with a specific polarization direction into the optical path;

[0061] Step S103: Adjust the gain medium to maximize the power of the fundamental frequency laser output from the laser resonator.

[0062] Step S104: Insert the birefringent filter into the optical path at Brewster angle, and adjust the birefringent filter to select the wavelength of the output fundamental frequency laser;

[0063] Step S105: Insert the frequency doubling crystal into the optical path, adjust the frequency doubling crystal to achieve the phase matching angle for generating the second harmonic, and output frequency doubling laser with narrowed spectral linewidth to generate frequency doubling laser;

[0064] Step S106: Fine-tune the birefringent filter and the frequency doubling crystal again to change the transmittance peak position of the birefringent filter for the fundamental frequency laser and the frequency doubling laser, so that the birefringent filter simultaneously narrows the spectral linewidth of the fundamental frequency laser and the frequency doubling laser, thereby obtaining a frequency doubling laser with narrowed spectral linewidth.

[0065] Figure 4 The spectral linewidth obtained without using the device described in this application. Figure 5 The spectral linewidth obtained using the device described in this application, Figure 4 and Figure 5 A comparison of the spectral linewidth results showed that the linewidth (FWHM) decreased from 479.9 pm to 7.599 pm, narrowing it to 1 / 63 of its original value. This demonstrates that the device and method for narrowing the output laser spectral linewidth provided in this application are effective.

[0066] This application achieves the effect of narrowing the output laser linewidth by inserting a designed birefringent filter at a Brewster angle into the resonant cavity. The birefringent filter itself is made of quartz crystal, which has the following advantages: low cost and easy processing; good stability and resistance to deliquescence; high damage threshold, allowing it to be inserted into high-power laser cavities; quartz crystal has high transmittance for near-ultraviolet, visible, and infrared light bands, and as an optical element, it inherently has low insertion loss. This method of narrowing the linewidth is relatively simple, requires a small number of components, is easy to operate, and can be applied to various common lasers, achieving good linewidth compression effects.

[0067] It should be noted that the flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of this application. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions marked in the blocks may occur in a different order than those marked in the drawings. For example, two consecutive blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, can be implemented using a dedicated hardware-based system that performs the specified function or action, or using a combination of dedicated hardware and computer instructions.

[0068] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0069] In the several embodiments provided in this application, it should be understood that the disclosed apparatus and methods can be implemented in other ways. The apparatus embodiments described above are merely illustrative. For example, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. Furthermore, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Additionally, the displayed or discussed mutual couplings, direct couplings, or communication connections may be through some communication interfaces; indirect couplings or communication connections between devices or units may be electrical, mechanical, or other forms.

[0070] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0071] In addition, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0072] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0073] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application.

Claims

1. A frequency-doubled laser linewidth narrowing device, characterized in that, include: A pump module is used to provide linearly polarized light with a specific polarization direction into the optical path; A laser resonant cavity, wherein a gain medium, at least one birefringent filter and a frequency doubling crystal are arranged sequentially along the optical path, and the at least one birefringent filter is inserted into the optical path at Brewster angle; The linearly polarized light is focused in the gain medium, the center wavelength of the linearly polarized light is the same as the absorption peak wavelength of the gain medium, and the polarization direction of the linearly polarized light is the same as the maximum absorption direction of the gain medium.

2. The frequency doubling laser linewidth narrowing device according to claim 1, characterized in that, The number of birefringent filters is greater than one, and the thickness of all birefringent filters is in a preset ratio.

3. The frequency doubling laser linewidth narrowing device according to claim 1, characterized in that, The gain medium is any one of the following solid-state laser crystals: Nd:YVO4, Nd:YAG, Nd:YLF, Yb:YAG, Tm:YAG, Er:YAG and Cr 3+ :BeAl2O4.

4. The frequency doubling laser linewidth narrowing device according to claim 1, characterized in that, The frequency doubling crystal is any one of the following: KDP crystals, LBO crystals, and BBO crystals.

5. The frequency doubling laser linewidth narrowing device according to claim 1, characterized in that, The linearly polarized light is focused at the center of the gain medium.

6. The frequency doubling laser linewidth narrowing device according to claim 1, characterized in that, The laser resonant cavity is of any one of the following types: Plane-to-planar critical cavity, plane-to-concave cavity, annular cavity, X-shaped cavity and V-shaped cavity.

7. The frequency doubling laser linewidth narrowing device according to claim 1, characterized in that, The pumping module uses side pumping.

8. The frequency doubling laser linewidth narrowing device according to claim 1, characterized in that, The pumping module uses end-face pumping.

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