A multi-wavelength solid-state laser based on Ho-doped crystal and its operation method

Abstract

This invention relates to a multi-wavelength solid-state laser based on a Ho-doped crystal and its operation method, belonging to the field of optoelectronic device manufacturing and optical engineering laser technology. To address the challenge of developing a multi-wavelength solid-state laser with a simpler operation process, this invention includes a 1940nm pump source connected to a fiber-coupled lens group via an optical fiber. Along the optical path on the right side of the fiber-coupled lens group, a microlens array, an input plane mirror, a Ho-doped hybrid crystal, an output plane mirror, and a 1900nm narrowband filter are arranged sequentially. The Ho-doped hybrid crystal is composed of a central cylindrical doped crystal and four surrounding ring-shaped doped crystals (first, second, third, and fourth sectors). This invention enables a single pump source and laser to generate multiple wavelengths of laser light, which is of great significance for wavelength division multiplexing (WDM) scenarios such as fiber optic communication and optical computing.

Description

Technical Field

[0001] This invention belongs to the field of optoelectronic device manufacturing and optical engineering laser technology, specifically relating to a multi-wavelength solid-state laser based on Ho-doped crystal and its operation method. Background Technology

[0002] Wavelength division multiplexing (WDM) technology, as a core technology in cutting-edge fields such as optical fiber communication and optical computing, is rapidly expanding into multiple sectors of the information industry. Its demand for efficient and highly integrated laser output poses a significant challenge to modern laser technology. However, due to the inherent absorption and emission spectral limitations of laser crystals, traditional lasers are mostly limited to single-wavelength operation. The ability to generate multi-wavelength signals is limited by the number of lasers. Moreover, independent lasers, due to their complex tuning characteristics, struggle to achieve stable multi-wavelength output. This poses a severe challenge to fields that widely apply WDM technology, such as optoelectronic integration (e.g., on-chip computing and data interconnection) and optical fiber communication.

[0003] The "Multi-wavelength Laser" authorized by CN203674555U utilizes three parallel laser modules—green, red, and blue—with their centers forming an equilateral triangle. The emitted light from each module has the same divergence angle and spot size. Different combinations of the red, blue, and green laser modules can be used to produce lasers of different colors. However, it can only output red, green, and blue lasers.

[0004] The patent application CN112928588B, entitled "A Multi-Wavelength Laser," utilizes a resonant cavity and cavity mirror coating process in an imaging structure to achieve different distribution regions for lasers of different wavelengths within the gain medium, thus avoiding competition between wavelengths. The laser is coated with films of different reflectivities for different wavelengths, resulting in varying losses for each wavelength in each coating region. This ensures that only one wavelength oscillates in each coating region, enabling the laser to simultaneously output different wavelengths. However, the fabrication process involves coating processes for different gain media, making its practical application extremely complex. It also raises questions about the availability of mature coating processes for the corresponding gain media and the need for different pump sources for different wavelength outputs. Summary of the Invention

[0005] The problem this invention aims to solve is to develop a multi-wavelength solid-state laser with a simpler operating process and higher value. It proposes a multi-wavelength solid-state laser based on Ho-doped crystals and its operating method.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A multi-wavelength solid-state laser based on Ho-doped crystal includes a 1940nm pump source, an optical fiber, an optical fiber coupled lens group, a microlens array, an input plane mirror, a Ho-doped hybrid crystal, an output plane mirror, and a 1900nm narrowband filter.

[0008] The 1940nm pump source is connected to a fiber-coupled lens group via an optical fiber. The right side of the fiber-coupled lens group is arranged along the optical path with a microlens array, an input plane mirror, a Ho-doped hybrid crystal, an output plane mirror, and a 1900nm narrowband filter.

[0009] The Ho-doped hybrid crystal is composed of a cylindrical doped crystal at the center and a first ring-shaped doped crystal, a second ring-shaped doped crystal, a third ring-shaped doped crystal, and a fourth ring-shaped doped crystal surrounding the cylindrical doped crystal. The cylindrical doped crystal is one of Ho:YAP crystals cut along different axes. The first ring-shaped doped crystal, the second ring-shaped doped crystal, the third ring-shaped doped crystal, and the fourth ring-shaped doped crystal are combinations of several Ho:LLF crystals, Ho:YAP crystals, and Ho:YLF crystals cut along different axes.

[0010] Alternatively, the Ho-doped mixed crystal can be replaced by a combination of a first sector-shaped doped crystal, a second sector-shaped doped crystal, a third sector-shaped doped crystal, and a fourth sector-shaped doped crystal, wherein the first sector-shaped doped crystal, the second sector-shaped doped crystal, the third sector-shaped doped crystal, and the fourth sector-shaped doped crystal are combinations of several Ho:LLF crystals, Ho:YAP crystals, and Ho:YLF crystals cut along different axes.

[0011] Furthermore, the surface of the input plane mirror is coated with a 2050nm narrowband reflective film, and the surface of the output plane mirror is coated with a 2050nm 5% transmission film.

[0012] Furthermore, in the Ho-doped mixed crystal, the cylindrical doped crystal is an a-axis cut Ho:YAP crystal, the first ring-shaped doped crystal is a c-axis cut Ho:LLF crystal, the second ring-shaped doped crystal is a c-axis cut Ho:YAP crystal, the third ring-shaped doped crystal is a c-axis cut Ho:YLF crystal, and the fourth ring-shaped doped crystal is a b-axis cut Ho:YAP crystal.

[0013] Furthermore, in the Ho-doped mixed crystal (6), the first sector-shaped doped crystal is a c-axis cut Ho:LLF crystal, the second sector-shaped doped crystal is a c-axis cut Ho:YAP crystal, the third sector-shaped doped crystal is a c-axis cut Ho:YLF crystal, and the fourth sector-shaped doped crystal is a b-axis cut Ho:YLF crystal.

[0014] Furthermore, in the Ho-doped mixed crystal, the angle range of each doped crystal is 0-90°.

[0015] An operation method for a multi-wavelength solid-state laser based on a Ho-doped crystal, comprising the following steps:

[0016] A 1940nm pump source outputs pump light, which is transmitted through an optical fiber and coupled into an optical fiber-coupled lens group to output parallel light. The parallel light is then split and focused by a microlens array and passed through an input plane mirror, resulting in 1940nm wavelength light converging on the front end of the Ho-doped hybrid crystal.

[0017] In a Ho-doped hybrid crystal, different doped crystals absorb the input light in the 1940nm band and output light in different bands.

[0018] Light of different wavelengths passes through the output plane mirror and is then filtered by a 1900nm narrowband filter to obtain 2μm band lasers with different frequency ranges.

[0019] Furthermore, based on crystal rotation angles ranging from 0 to 90°, the polarization direction of each input laser beam and the axial direction of the crystal at different focusing rotation angles are different. When an angle change α occurs between the polarization direction of the input laser and the crystal principal axis, it causes changes in the wavelengths of the σ-polarization and π-polarization states output by the doped crystal, resulting in the expression:

[0020] λ σ (θ1)=λ σ (θ0)+Δλ σ (α) (1)

[0021] λ π (θ1)=λ π (θ0)+Δλ π (α) (2)

[0022] Where θ0 is defined as the initial angle between the polarization direction of the input light and the principal axis of the crystal, and the angle becomes θ1 after rotation α. σ (θ0) and λ σ (θ1) is defined as the center wavelength of the output of the σ polarization state at angles θ0 and θ1, respectively. π (θ0) and λ π (θ1) is defined as the center wavelength of the π-polarized state output at angles θ0 and θ1, respectively, and Δλ is the center wavelength of the output of the π-polarized state. σ (α) and Δλ π (α) represents the change in the center wavelength of the σ polarization state and the change in the center wavelength of the π polarization state after rotation α;

[0023] The expression for the refractive index relationship between the a-axis and c-axis planes of a doped crystal is:

[0024]

[0025] Where, n a and n c These are the refractive indices along the a-axis and c-axis, respectively, and n c (θ) is the refractive index when the polarization direction of the input light is at an angle θ with the principal axis of the crystal;

[0026] Based on the constraint of the standing wave condition of the resonant cavity between the input and output mirrors on the output light, the expression is obtained as follows:

[0027] 2kL'=2mπ (4)

[0028] L'=n0L1+n c (θ)L2 (5)

[0029] Where k is the mode of the wave vector, L' is the total optical path, and n0L1 and n c (θ)L2 represents the optical path lengths outside and inside the crystal in the resonant cavity, respectively, where m is the first positive integer; L1 and L2 represent the propagation paths of light during oscillation in the resonant cavity outside and inside the crystal, respectively.

[0030] Combining equations (3), (4), and (5), we obtain:

[0031]

[0032] When the angle θ changes by α, equation (6) changes to:

[0033]

[0034] Where k' is the modulus of the transformed wave vector, and m' is the second positive integer;

[0035] Introducing wavelength λ into equation (7), we obtain the following expression:

[0036]

[0037] Where m1' and m2' are the third positive integer and the fourth positive integer, respectively, and θ π0 and θ σ0 These represent the angles between the output σ polarization and π polarization and the crystal principal axis, respectively.

[0038] Based on equations (8) and (9), the variable Δλ is obtained after introducing α. π (α) / Δλ σ (α) and m1' / m2' also change together; when the polarizer is rotated, the refractive index n changes with θ. c(θ) changes, thus changing the optical path L'. In order to satisfy the standing wave condition, the mode k of the wave vector will change accordingly, that is, the wavelength λ changes. Under the conditions of satisfying equations (8) and (9), the multi-wavelength solid-state laser based on Ho-doped crystal outputs 2μm band lasers with different frequency ranges.

[0039] The above derivation is based on c-axis cutting of Ho:LLF crystals. This theoretical model is also applicable to Ho:YLF and Ho:YAP, with the only difference being the output of single-wavelength laser and dual-wavelength laser.

[0040] A multi-wavelength solid-state laser based on Ho-doped crystal includes a 795nm LD pump source, an optical fiber, an optical fiber coupled lens group, a microlens array, an input plane mirror, a Tm:YAP crystal, a Ho-doped hybrid crystal, an output plane mirror, a 1000nm narrowband filter, and a 2000nm narrowband filter.

[0041] The 795nm LD pump source is connected to a fiber-coupled lens group via an optical fiber. The fiber-coupled lens group has a microlens array, an input plane mirror, a Tm:YAP crystal, a Ho-doped hybrid crystal, an output plane mirror, a 1000nm narrowband filter, and a 2000nm narrowband filter arranged sequentially along the optical path on the right side.

[0042] The Ho-doped hybrid crystal is composed of a cylindrical doped crystal at the center and a first ring-shaped doped crystal, a second ring-shaped doped crystal, a third ring-shaped doped crystal, and a fourth ring-shaped doped crystal surrounding the cylindrical doped crystal. The cylindrical doped crystal is one of Ho:YAP crystals cut along different axes. The first ring-shaped doped crystal, the second ring-shaped doped crystal, the third ring-shaped doped crystal, and the fourth ring-shaped doped crystal are combinations of several Ho:LLF crystals, Ho:YAP crystals, and Ho:YLF crystals cut along different axes.

[0043] Alternatively, the Ho-doped mixed crystal may be composed of a first sector-shaped doped crystal, a second sector-shaped doped crystal, a third sector-shaped doped crystal, and a fourth sector-shaped doped crystal, wherein the first sector-shaped doped crystal, the second sector-shaped doped crystal, the third sector-shaped doped crystal, and the fourth sector-shaped doped crystal are combinations of several Ho:LLF crystals, Ho:YAP crystals, and Ho:YLF crystals cut along different axes.

[0044] Furthermore, the surface of the input plane mirror is coated with a 2050nm narrowband reflective film, and the surface of the output plane mirror is coated with a 2050nm 5% transmission film.

[0045] Furthermore, in the Ho-doped mixed crystal, the cylindrical doped crystal is an a-axis cut Ho:YAP crystal, the first ring-shaped doped crystal is a c-axis cut Ho:LLF crystal, the second ring-shaped doped crystal is a c-axis cut Ho:YAP crystal, the third ring-shaped doped crystal is a c-axis cut Ho:YLF crystal, and the fourth ring-shaped doped crystal is a b-axis cut Ho:YAP crystal; the angle range of each doped crystal in the Ho-doped mixed crystal is 0-90°.

[0046] The beneficial effects of this invention are:

[0047] The present invention discloses a multi-wavelength solid-state laser based on Ho-doped crystal, which innovatively designs a special hybrid laser crystal and uses a pump and an optical cavity to output a large number of lasers with different wavelengths, thus achieving efficient multi-wavelength output.

[0048] This invention discloses a multi-wavelength solid-state laser based on Ho-doped crystals. Through derivation and analysis, wavelength output switching can be achieved by angle tuning. An innovative arc-shaped structure is designed, utilizing different crystal compositions and angle arrangements to achieve multi-wavelength output over a wide wavelength range. By combining different tangential directions and angles, different output wavelengths can be achieved, thus realizing multi-wavelength output.

[0049] The present invention discloses a multi-wavelength solid-state laser based on Ho-doped crystals, which utilizes the efficient absorption of 1940nm wavelength light by all components of the Ho-doped hybrid crystal and achieves multi-wavelength output in a single laser by combining Ho-doped crystals with different substrates.

[0050] This invention discloses a multi-wavelength solid-state laser based on Ho-doped crystals. Because orthogonally polarized dual-wavelength solid-state lasers can emit two laser beams with a fixed wavelength difference, they are ideally suited as the basic unit for wavelength division multiplexing (WDM) light sources. Furthermore, dual-wavelength lasers possess incoherent characteristics, allowing each wavelength to efficiently carry different information, thus significantly improving the efficiency of complex information transmission and processing. Therefore, when integrating multiple orthogonally polarized dual-wavelength lasers with strong absorption effects on the same pump, the system's light source will simultaneously possess extremely high efficiency and highly integrated multi-wavelength output capability. Utilizing the strong absorption characteristics of different Ho-doped substrate materials for the same pump source (1940nm), and frequency modulation methods such as angle tuning, a laser with the capability to output ultra-multi-wavelength lasers is designed, resolving the contradiction between multi-wavelength output and high integration. The key feature of this invention is that it requires only one pump source and one laser to excite multi-wavelength lasers, which is of great significance for wavelength division multiplexing scenarios such as fiber optic communication and optical computing, greatly reducing the size of the light source.

[0051] This invention discloses a multi-wavelength solid-state laser based on Ho-doped crystals, and its multi-wavelength output performance has been verified through theoretical analysis and experiments. This invention not only provides a new approach to addressing the challenges of current multi-wavelength laser sources, but also lays the foundation for future innovations in related fields such as optical communication and optical computing. Attached Figure Description

[0052] Figure 1 This is a schematic diagram of the first structure of a multi-wavelength solid-state laser based on a Ho-doped crystal constructed using a 1940nm pump source according to the present invention.

[0053] Figure 2 This is a schematic diagram of the structure of the Ho-doped hybrid crystal of the present invention. Figure 1 , and axial schematic diagrams of small crystals with different rotation angles, where a is a structural schematic diagram of Ho-doped mixed crystal, and b is an axial schematic diagram of small crystals with different rotation angles;

[0054] Figure 3 This is a schematic diagram of the c-axis cut portion of the Ho-doped hybrid crystal of the present invention;

[0055] Figure 4 This is a schematic diagram of the a-axis cut portion of the Ho-doped hybrid crystal of the present invention;

[0056] Figure 5 This is a c-axis cut refractive index ellipse diagram of Ho:LLF crystal according to the present invention;

[0057] Figure 6 This is a schematic diagram of the structure of the Ho-doped hybrid crystal of the present invention. Figure 2 ;

[0058] Figure 7 This is a schematic diagram of a multi-wavelength solid-state laser based on a Ho-doped crystal, constructed using a 795nm pump source according to the present invention. Detailed Implementation

[0059] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention; that is, the described specific embodiments are merely a part of the embodiments of the invention, and not all of them. The components of the specific embodiments of the invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations, and the invention may also have other embodiments.

[0060] Therefore, the following detailed description of specific embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected specific embodiments of the invention. All other specific embodiments obtained by those skilled in the art based on these specific embodiments without inventive effort are within the scope of protection of this invention.

[0061] To further understand the invention's content, features, and effects, the following specific embodiments are provided, along with accompanying drawings. Figure 1 -Appendix Figure 7 The detailed instructions are as follows:

[0062] Example 1:

[0063] A multi-wavelength solid-state laser based on Ho-doped crystal includes a 1940nm pump source 1, an optical fiber 2, an optical fiber coupled lens group 3, a microlens array 4, an input plane mirror 5, a Ho-doped hybrid crystal 6, an output plane mirror 7, and a 1900nm narrowband filter 8.

[0064] The 1940nm pump source 1 is connected to the fiber-coupled lens group 3 via the optical fiber 2. The right side of the fiber-coupled lens group 3 is arranged along the optical path as follows: microlens array 4, input plane mirror 5, Ho-doped hybrid crystal 6, output plane mirror 7, and 1900nm narrowband filter 8.

[0065] The Ho-doped hybrid crystal 6 is composed of a cylindrical doped crystal 16 at the center and a first ring-shaped doped crystal 12, a second ring-shaped doped crystal 13, a third ring-shaped doped crystal 14, and a fourth ring-shaped doped crystal 15 surrounding the cylindrical doped crystal 16. The cylindrical doped crystal 16 is one of Ho:YAP crystals cut along different axes. The first ring-shaped doped crystal 12, the second ring-shaped doped crystal 13, the third ring-shaped doped crystal 14, and the fourth ring-shaped doped crystal 15 are combinations of several Ho:LLF crystals, Ho:YAP crystals, and Ho:YLF crystals cut along different axes.

[0066] Furthermore, the surface of the input plane mirror 5 is coated with a 2050nm narrowband reflective film, and the surface of the output plane mirror 7 is coated with a 2050nm 5% transmission film.

[0067] Furthermore, in the Ho-doped mixed crystal 6, the cylindrical doped crystal 16 is a Ho:YAP crystal cut along the a-axis, the first ring-shaped doped crystal 12 is a Ho:LLF crystal cut along the c-axis, the second ring-shaped doped crystal 13 is a Ho:YAP crystal cut along the c-axis, the third ring-shaped doped crystal 14 is a Ho:YLF crystal cut along the c-axis, and the fourth ring-shaped doped crystal 15 is a Ho:YAP crystal cut along the b-axis.

[0068] Furthermore, the angle range of each doped crystal in the Ho-doped mixed crystal 6 is 0-90°. Furthermore, the Ho:LLF, Ho:YLF, and Ho:YAP crystals in the Ho-doped mixed crystal have high hardness and can be cut by conventional mechanical cutting or laser cutting. When assembling the Ho-doped mixed crystal, a heat sink of the required shape can be customized; placing the crystal within the heat sink completes the crystal fabrication. One method for crystal cutting is to cut all along the c-axis and then... Figure 2 The middle left image shows a spliced ​​arrangement placed on a heat sink. Another method is to cut small crystals directly from the large crystal cut along the c-axis at different angles to the c-axis, without cutting along the c-axis. This cutting direction is defined as "c-5° cutting", "c-10° cutting", ... "c-θ cutting", etc. After cutting, they can be directly spliced ​​and placed on a heat sink.

[0069] Furthermore, the microlens array is composed of microconvex lenses, the positions of which correspond to each small crystal in the Ho-doped mixed crystal, ensuring that each beam of laser light after beam splitting is focused onto the end face of the small crystal. During operation, the placement position of the Ho-doped crystal should be adjusted according to the focal length of the microlens array.

[0070] Furthermore, the function of the fiber coupling lens group 3 is to couple the pump light in the fiber and output parallel light;

[0071] Furthermore, the reason why the Ho-doped hybrid crystal 6 outputs multi-wavelength lasers is as follows: First, all three types of Ho-doped crystals absorb light intensity in the 1940nm band and output lasers in different bands. The Ho:LLF dual-wavelength output band is around 2060nm, the Ho:YAP output band is around 2130nm, and the Ho:YLF output band is around 2050nm. Therefore, due to the different substrate materials, the four crystals output lasers in four different bands. Second, for any one of the four c-axis cut crystals, taking the c-axis cut Ho:LLF crystal as an example, the polarization direction of each pump light output by the microlens array is the same. However, according to the different rotation angles (0-90°) of each small crystal that makes up the Ho:LLF part, the polarization state of each laser beam and the axis of the focused small crystal are different.

[0072] To verify the effect of crystal rotation on wavelength variation in the theory, taking c-axis cutting of Ho:LLF crystal as an example, Table 1 shows the wavelength variation of the output laser under angle tuning of 13°-80°, which is consistent with the theoretical derivation. The π-polarized wavelength variation range of the horizontal output is 2053-2056.3nm, and the σ-polarized wavelength variation range of the vertical output is 2063.1-2065.7nm. The test results verify the feasibility of a multi-wavelength solid-state laser based on Ho-doped crystal.

[0073] Table 1:

[0074] Angle\Polarization π-polarized wavelength (nm) σ-polarization wavelength (nm) 13° 2052 2063.9 27° 2052.6 2064.2 45° 2055.3 2065 55° 2056.3 2065.7 69° 2053.4 2064.7 80° 2052.1 2063

[0075] This embodiment describes a multi-wavelength solid-state laser based on Ho-doped crystals. It innovatively designs the laser crystal and utilizes the high absorption of each part of the hybrid crystal for the Tm:YAP output beam to output a series of 2μm band lasers with different wavelengths according to different crystal substrates, rotation angles, and cutting directions.

[0076] Example 2:

[0077] An operation method for a multi-wavelength solid-state laser based on a Ho-doped crystal, implemented according to the multi-wavelength solid-state laser based on a Ho-doped crystal described in Example 1, includes the following steps:

[0078] A 1940nm pump source outputs pump light, which is transmitted through an optical fiber and coupled into an optical fiber-coupled lens group to output parallel light. The parallel light is then split and focused by a microlens array and passed through an input plane mirror, resulting in 1940nm wavelength light converging on the front end of the Ho-doped hybrid crystal.

[0079] In a Ho-doped hybrid crystal, different doped crystals absorb the input light in the 1940nm band and output light in different bands.

[0080] Light of different wavelengths passes through the output plane mirror and is then filtered by a 1900nm narrowband filter to obtain 2μm band lasers with different frequency ranges.

[0081] Furthermore, based on crystal rotation angles ranging from 0 to 90°, the polarization direction of each input laser beam and the axial direction of the crystal at different focusing rotation angles are different. When an angle change α occurs between the polarization direction of the input laser and the crystal principal axis, it causes changes in the wavelengths of the σ-polarization and π-polarization states output by the doped crystal, resulting in the expression:

[0082] λ σ (θ1)=λ σ (θ0)+Δλ σ (α) (1)

[0083] λ π (θ1)=λ π (θ0)+Δλ π (α) (2)

[0084] Where θ0 is defined as the initial angle between the polarization direction of the input light and the principal axis of the crystal, and the angle becomes θ1 after rotation α. σ (θ0) and λ σ(θ1) is defined as the center wavelength of the output of the σ polarization state at angles θ0 and θ1, respectively. π (θ0) and λ π (θ1) is defined as the center wavelength of the π-polarized state output at angles θ0 and θ1, respectively, and Δλ is the center wavelength of the output of the π-polarized state. σ (α) and Δλ π (α) represents the change in the center wavelength of the σ polarization state and the change in the center wavelength of the π polarization state after rotation α;

[0085] The expression for the refractive index relationship between the a-axis and c-axis planes of a doped crystal is:

[0086]

[0087] Where, n a and n c These are the refractive indices along the a-axis and c-axis, respectively, and n c (θ) is the refractive index when the polarization direction of the input light is at an angle θ with the principal axis of the crystal;

[0088] Based on the constraint of the standing wave condition of the resonant cavity between the input and output mirrors on the output light, the expression is obtained as follows:

[0089] 2kL'=2mπ (4)

[0090] L'=n0L1+n c (θ)L2 (5)

[0091] Where k is the mode of the wave vector, L' is the total optical path, and n0L1 and n c (θ)L2 represents the optical path lengths outside and inside the crystal in the resonant cavity, respectively, where m is the first positive integer; L1 and L2 represent the propagation paths of light during oscillation in the resonant cavity outside and inside the crystal, respectively.

[0092] Combining equations (3), (4), and (5), we obtain:

[0093]

[0094] When the angle θ changes by α, equation (6) changes to:

[0095]

[0096] Where k' is the magnitude of the transformed wave vector, and m' is the second positive integer;

[0097] Introducing wavelength λ into equation (7), we obtain the following expression:

[0098]

[0099] Where m1' and m2' are the third positive integer and the fourth positive integer, respectively, and θπ0 and θ σ0 These represent the angles between the output σ polarization and π polarization and the crystal principal axis, respectively.

[0100] Based on equations (8) and (9), the variable Δλ is obtained after introducing α. π (α) / Δλ σ (α) and m1' / m2' also change together; when the polarizer is rotated, the refractive index n changes with θ. c (θ) changes, thus changing the optical path L'. In order to satisfy the standing wave condition, the mode k of the wave vector will change accordingly, that is, the wavelength λ changes. The above derivation is based on c-axis cutting of Ho:LLF crystal. This theoretical model is also applicable to Ho:YLF and Ho:YAP. The only difference is the output of single-wavelength laser and dual-wavelength laser. Under the conditions of satisfying equations (8) and (9), the multi-wavelength solid-state laser based on Ho doped crystal outputs 2μm band lasers with different frequency ranges.

[0101] Based on the above derivation, it can be seen that due to the special design of the Ho-doped mixed crystal, the refractive index n changes with θ. c The change in (θ) causes a change in the optical path L'. To satisfy the standing wave condition, the mode k of the wave vector changes accordingly, i.e., the wavelength λ changes. This theoretical model is also applicable to doped crystals including Ho:YLF and Ho:YAP, with the only difference being the output of single-wavelength lasers and dual-wavelength lasers. In other words, each part of the Ho-doped hybrid crystal outputs lasers of different wavelengths due to the change in polarization direction. Even within the same crystal, each part of the sector structure outputs lasers of different wavelengths due to different rotation angles.

[0102] Example 3:

[0103] The difference between this embodiment and Embodiment 1 is that the Ho-doped mixed crystal 6 described in this embodiment is replaced by a combination of a first sector-shaped doped crystal 18, a second sector-shaped doped crystal 19, a third sector-shaped doped crystal 20, and a fourth sector-shaped doped crystal 21. The first sector-shaped doped crystal 18, the second sector-shaped doped crystal 19, the third sector-shaped doped crystal 20, and the fourth sector-shaped doped crystal 21 are combinations of several Ho:LLF crystals, Ho:YAP crystals, and Ho:YLF crystals cut along different axes.

[0104] Furthermore, in the Ho-doped mixed crystal 6, the first sector-shaped doped crystal 18 is a c-axis cut Ho:LLF crystal, the second sector-shaped doped crystal 19 is a c-axis cut Ho:YAP crystal, the third sector-shaped doped crystal 20 is a c-axis cut Ho:YLF crystal, and the fourth sector-shaped doped crystal 21 is an a-axis cut Ho:YLF crystal.

[0105] Example 4:

[0106] The difference between this embodiment and Embodiment 1 is that the 1940nm pump source 1 is replaced by a 795nm LD pump source 9. The 795nm LD pump source 9 is connected to the fiber-coupled lens group 3 through the fiber optic 2. The fiber-coupled lens group 3 is arranged sequentially along the optical path on the right side, including a microlens array 4, an input plane mirror 5, a Tm:YAP crystal 17, a Ho-doped hybrid crystal 6, an output plane mirror 7, a 1000nm narrowband filter 10, and a 2000nm narrowband filter 11.

[0107] It should be noted that relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0108] Although this application has been described above with reference to specific embodiments, various modifications can be made and components can be replaced with equivalents without departing from the scope of this application. In particular, as long as there is no structural conflict, the features in the specific embodiments disclosed in this application can be combined with each other in any way. The lack of an exhaustive description of these combinations in this specification is merely for the sake of brevity and resource conservation. Therefore, this application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A multi-wavelength solid-state laser based on Ho-doped crystal, characterized in that, It includes a 1940nm pump source (1), an optical fiber (2), an optical fiber coupled lens group (3), a microlens array (4), an input plane mirror (5), a Ho-doped mixed crystal (6), an output plane mirror (7), and a 1900nm narrowband filter (8). The 1940nm pump source (1) is connected to the fiber-coupled lens group (3) via the optical fiber (2). The fiber-coupled lens group (3) is arranged in sequence along the optical path on the right side with a microlens array (4), an input plane mirror (5), a Ho-doped mixed crystal (6), an output plane mirror (7), and a 1900nm narrowband filter (8). The Ho-doped mixed crystal (6) is composed of a cylindrical doped crystal (16) at the center and a first ring-shaped doped crystal (12), a second ring-shaped doped crystal (13), a third ring-shaped doped crystal (14), and a fourth ring-shaped doped crystal (15) surrounding the cylindrical doped crystal (16). The cylindrical doped crystal (16) is one of Ho:YAP crystals cut along different axes. The first ring-shaped doped crystal (12), the second ring-shaped doped crystal (13), the third ring-shaped doped crystal (14), and the fourth ring-shaped doped crystal (15) are combinations of several Ho:LLF crystals, Ho:YAP crystals, and Ho:YLF crystals cut along different axes. Alternatively, the Ho-doped mixed crystal (6) may be composed of a first sector-shaped doped crystal (18), a second sector-shaped doped crystal (19), a third sector-shaped doped crystal (20), and a fourth sector-shaped doped crystal (21), wherein the first sector-shaped doped crystal (18), the second sector-shaped doped crystal (19), the third sector-shaped doped crystal (20), and the fourth sector-shaped doped crystal (21) are combinations of several Ho:LLF crystals, Ho:YAP crystals, and Ho:YLF crystals cut along different axes.

2. The multi-wavelength solid-state laser based on Ho-doped crystal according to claim 1, characterized in that, The surface of the input plane mirror (5) is coated with a 2050nm narrowband reflective film, and the surface of the output plane mirror (7) is coated with a 2050nm 5% transmission film.

3. A multi-wavelength solid-state laser based on a Ho-doped crystal according to claim 2, characterized in that, In the Ho-doped mixed crystal (6), the cylindrical doped crystal (16) is an a-axis cut Ho:YAP crystal, the first ring-shaped doped crystal (12) is a c-axis cut Ho:LLF crystal, the second ring-shaped doped crystal (13) is a c-axis cut Ho:YAP crystal, the third ring-shaped doped crystal (14) is a c-axis cut Ho:YLF crystal, and the fourth ring-shaped doped crystal (15) is a b-axis cut Ho:YAP crystal.

4. A multi-wavelength solid-state laser based on a Ho-doped crystal according to claim 3, characterized in that, In the Ho-doped mixed crystal (6), the first sector-shaped doped crystal (18) is a c-axis cut Ho:LLF crystal, the second sector-shaped doped crystal (19) is a c-axis cut Ho:YAP crystal, the third sector-shaped doped crystal (20) is a c-axis cut Ho:YLF crystal, and the fourth sector-shaped doped crystal (21) is a b-axis cut Ho:YLF crystal.

5. A multi-wavelength solid-state laser based on a Ho-doped crystal according to claim 4, characterized in that, The angle range of each doped crystal in the Ho-doped mixed crystal (6) is 0-90°.

6. An operation method for a multi-wavelength solid-state laser based on a Ho-doped crystal, implemented using the multi-wavelength solid-state laser based on a Ho-doped crystal as described in any one of claims 1-5, characterized in that, Includes the following steps: A 1940nm pump source outputs pump light, which is transmitted through an optical fiber and coupled into an optical fiber-coupled lens group to output parallel light. The parallel light is then split and focused by a microlens array and passed through an input plane mirror, resulting in 1940nm wavelength light converging on the front end of the Ho-doped hybrid crystal. In a Ho-doped hybrid crystal, different doped crystals absorb the input light in the 1940nm band and output light in different bands. Light of different wavelengths passes through the output plane mirror and is then filtered by a 1900nm narrowband filter to obtain 2μm band lasers with different frequency ranges.

7. The operation method of a multi-wavelength solid-state laser based on a Ho-doped crystal according to claim 6, characterized in that: In different doped crystals, based on a crystal rotation angle of 0-90°, the polarization direction of each input laser beam and the axial direction of the crystal at different focusing rotation angles are different. When an angle change α occurs between the polarization direction of the input laser and the crystal principal axis, it causes a change in the wavelength of the σ-polarization state and π-polarization state output by the doped crystal, resulting in the expression: l σ (θ1)=λ σ (θ0)+Δλ σ (a)(1) l π (θ1)=λ π (θ0)+Δλ π (a)(2) Where θ0 is defined as the initial angle between the polarization direction of the input light and the principal axis of the crystal, and the angle becomes θ1 after rotation α. σ (θ0) and λ σ (θ1) is defined as the center wavelength of the output of the σ polarization state at angles θ0 and θ1, respectively. π (θ0) and λ π (θ1) is defined as the center wavelength of the π-polarized state output at angles θ0 and θ1, respectively, and Δλ is the center wavelength of the output of the π-polarized state. σ (α) and Δλ π (α) represents the change in the center wavelength of the σ polarization state and the change in the center wavelength of the π polarization state after rotation α; The expression for the refractive index relationship between the a-axis and c-axis planes of a doped crystal is: Where, n a and n c These are the refractive indices along the a-axis and c-axis, respectively, and n c (θ) is the refractive index when the polarization direction of the input light is at an angle θ with the principal axis of the crystal; Based on the constraint of the output light on the standing wave condition of the resonant cavity between the input and output mirrors, the expression is obtained as follows: 2kL'=2mπ(4) L'=n0L1+n c (θ)L2(5) Where k is the mode of the wave vector, L' is the total optical path, and n0L1 and n c (θ)L2 represents the optical path lengths outside and inside the crystal in the resonant cavity, respectively, where m is the first positive integer; L1 and L2 represent the propagation paths of light during oscillation in the resonant cavity outside and inside the crystal, respectively. Combining equations (3), (4), and (5), we obtain: When the angle θ changes by α, equation (6) changes to: Where k' is the magnitude of the transformed wave vector, and m' is the second positive integer; Introducing wavelength λ into equation (7), we obtain the following expression: Where m1' and m2' are the third positive integer and the fourth positive integer, respectively, and θ π0 and θ σ0 These represent the angles between the output σ polarization and π polarization and the crystal principal axis, respectively. Based on equations (8) and (9), the variable Δλ is obtained after introducing α. π (α) / Δλ σ (α) and m1' / m2' also change together; when the polarizer is rotated, the refractive index n changes with θ. c (θ) changes, thus changing the optical path L', and the mode k of the wave vector changes accordingly, that is, the wavelength λ changes; under the conditions of satisfying equations (8) and (9), the multi-wavelength solid-state laser based on Ho-doped crystal outputs 2μm band lasers in different frequency ranges.

8. A multi-wavelength solid-state laser based on Ho-doped crystal, characterized in that, It includes a 795nm LD pump source (9), an optical fiber (2), an optical fiber coupled lens group (3), a microlens array (4), an input plane mirror (5), a Tm:YAP crystal (17), a Ho-doped mixed crystal (6), an output plane mirror (7), a 1000nm narrowband filter (10), and a 2000nm narrowband filter (11). The 795nm LD pump source (9) is connected to the fiber-coupled lens group (3) via the optical fiber (2). The fiber-coupled lens group (3) is arranged in sequence along the optical path on the right side with a microlens array (4), an input plane mirror (5), a Tm:YAP crystal (17), a Ho-doped mixed crystal (6), an output plane mirror (7), a 1000nm narrowband filter (10), and a 2000nm narrowband filter (11). The Ho-doped mixed crystal (6) is composed of a cylindrical doped crystal (16) at the center and a first ring-shaped doped crystal (12), a second ring-shaped doped crystal (13), a third ring-shaped doped crystal (14), and a fourth ring-shaped doped crystal (15) surrounding the cylindrical doped crystal (16). The cylindrical doped crystal (16) is one of Ho:YAP crystals cut along different axes. The first ring-shaped doped crystal (12), the second ring-shaped doped crystal (13), the third ring-shaped doped crystal (14), and the fourth ring-shaped doped crystal (15) are combinations of several Ho:LLF crystals, Ho:YAP crystals, and Ho:YLF crystals cut along different axes. Alternatively, the Ho-doped mixed crystal (6) may be composed of a first sector-shaped doped crystal (18), a second sector-shaped doped crystal (19), a third sector-shaped doped crystal (20), and a fourth sector-shaped doped crystal (21), wherein the first sector-shaped doped crystal (18), the second sector-shaped doped crystal (19), the third sector-shaped doped crystal (20), and the fourth sector-shaped doped crystal (21) are combinations of several Ho:LLF crystals, Ho:YAP crystals, and Ho:YLF crystals cut along different axes.

9. A multi-wavelength solid-state laser based on a Ho-doped crystal according to claim 8, characterized in that, The surface of the input plane mirror (5) is coated with a 2050nm narrowband reflective film, and the surface of the output plane mirror (7) is coated with a 2050nm 5% transmission film.

10. A multi-wavelength solid-state laser based on a Ho-doped crystal according to claim 9, characterized in that, In the Ho-doped mixed crystal (6), the cylindrical doped crystal (16) is an a-axis cut Ho:YAP crystal, the first ring-shaped doped crystal (12) is a c-axis cut Ho:LLF crystal, the second ring-shaped doped crystal (13) is a c-axis cut Ho:YAP crystal, the third ring-shaped doped crystal (14) is an a-axis cut Ho:YLF crystal, and the fourth ring-shaped doped crystal (15) is a b-axis cut Ho:YLF crystal; the angle range of each doped crystal in the Ho-doped mixed crystal (6) is 0-90°.

Images