Holmium-doped laser and control method therefor

Abstract

A holmium-doped laser (100) and a control method therefor. The laser (100) comprises a pump and seed source (101), a pump source amplifier (102), and a spatial resonant cavity (103); the pump and seed source (101) is configured for generating wavelength-tunable pump-seed light; the pump source amplifier (102) is configured for amplifying the pump-seed light to obtain amplified pump light; and the spatial resonant cavity (103) is configured for converting the amplified pump light into output laser light. By means of tuning the pump light wavelength, the holmium-doped laser (100) effectively achieves a 2-μm laser output with an optimal optical-to-optical conversion efficiency.

Description

Ho-doped laser and control method thereof TECHNICAL FIELD

[0001] The present application relates to the technical field of laser, in particular to Ho-doped laser and control method thereof. BACKGROUND

[0002] 2-m solid-state laser has wide application prospect in many fields, including medical surgery, spectrum analysis, laser radar and material processing. Current 2-m solid-state laser develops towards high average power, high conversion efficiency and high single pulse energy. Among numerous 2-m gain media, Ho:YAG crystal (Ho-doped yttrium aluminum garnet) has the characteristics of large effective emission cross section, long fluorescence lifetime, high damage threshold and high pump light utilization efficiency, and is the medium with the most excellent comprehensive performance. Single-doped Ho:YAG crystal has many absorption peaks, and there are strong absorption peaks near 1880 nm, 1908 nm, 1913 nm, 1919 nm, 1928 nm and 1931 nm, so there are many choices of pump wavelength. The traditional pump light source usually uses Tm:YLF (Tm-doped yttrium lithium fluoride) laser, and the emission wavelength of which is near the 1908 nm absorption peak of Ho:YAG. However, the traditional pump light source has single output wavelength, and the output beam quality is low (M 2 >1.5). Low beam quality will cause the waist radius of the pump light to be too large when collimating and focusing, so that the pump light cannot be effectively concentrated, and the energy density is not high enough, thereby reducing the optical conversion efficiency (theoretically, the waist radius should be controlled between 0.2-0.3 mm). SUMMARY

[0003] The present application provides a pump light wavelength tunable Ho-doped laser and a control method thereof, aiming to improve the output laser quality of 2-m solid-state laser, and uses Tm-doped polarization maintaining fiber laser as pump source, the output wavelength of which can be tuned in the range of 1880-1950 nm, covering all absorption peaks of Ho-doped crystal. By tuning the pump light wavelength, the pump light wavelength matched with the strong absorption peak is selected, so that the Ho-doped crystal can effectively absorb the energy of the pump light, reduce the energy loss, and more pump light energy is converted into excited state, thereby enhancing the efficiency of optical excitation, and realizing the 2-m laser output with optimized optical conversion efficiency. And the beam quality (M 2 <1.2) is effectively improved, so that when the pump light is collimated and focused on the Ho-doped crystal, the waist radius is controlled within the theoretical optimal value, and the optical conversion efficiency is further optimized. In addition, the working distance of the pump source and the focusing mirror is increased, the optical path adjustment and optimization process is simplified, the length of effective Rayleigh alignment is increased, the tolerance of longitudinal alignment is improved, and the stability and fault tolerance of the Ho-doped laser as a whole are enhanced.

[0004] In a first aspect, the present application provides a holmium-doped laser, characterized in that the laser comprises a pump seed source, a pump source amplifier and a spatial resonant cavity, wherein

[0005] The pump seed source is configured to generate pump seed light with tunable wavelength.

[0006] The pump source amplifier is configured to amplify the pump seed light to obtain amplified pump light.

[0007] The spatial resonant cavity is configured to convert the amplified pump light into output laser light.

[0008] In a second aspect, the present application further provides a control method of a holmium-doped laser, characterized in that the method comprises:

[0009] detecting the wavelength of the pump seed light and / or detecting the power of the output laser light;

[0010] adjusting the wavelength of the amplified pump seed light according to the power of the output laser light of the holmium-doped laser and / or directly adjusting the wavelength of the pump seed light input into the pump source amplifier.

[0011] The holmium-doped laser and the control method thereof provided by the present application provide pump light with tunable wavelength, and the efficiency of the pumping process is optimized by adjusting the wavelength of the pump light, so that the optical-to-optical conversion efficiency is optimized. The holmium-doped polarization maintaining fiber laser is used as the pump source, and the TFP polarizer, the grating and the polarization maintaining fiber are used, so that the polarization state stability and quality of the light beam are ensured, the quality of the light beam is significantly improved, the pump light collimation and focusing process is optimized, the beam waist radius is kept within the theoretically optimal range, and the optical-to-optical conversion efficiency is further improved. In addition, the structure is optimized, the working distance of the pump source and the focusing mirror is increased, the light path adjustment and optimization are facilitated, the operation flexibility and stability are improved, the effective Rayleigh alignment length is increased, and the overall stability and fault tolerance are improved. In addition, the automatic detection device and the control unit are provided, and the output power detection device feeds back the real-time detected output laser power to the control unit, so that the wavelength of the pump seed light is adjusted to make the power of the output laser light the highest. The efficiency and performance of the laser are optimized, and the automatic adjustment process reduces human intervention, improves the reliability and use convenience. BRIEF DESCRIPTION OF DRAWINGS

[0012] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0013] Fig. 1 is a schematic diagram of a holmium-doped laser structure according to an embodiment of the present application;

[0014] Fig. 2 is a schematic diagram of a pump seed source structure according to an embodiment of the present application;

[0015] Fig. 3 is a schematic diagram of a pump source pre-amplifier structure according to an embodiment of the present application;

[0016] Fig. 4 is a schematic diagram of a pump source main amplifier structure according to an embodiment of the present application;

[0017] Fig. 5 is a schematic diagram of a spatial resonant cavity structure according to an embodiment of the present application;

[0018] Fig. 6 is a flowchart of a control method of a holmium-doped laser according to an embodiment of the present application. DETAILED DESCRIPTION

[0019] The technical solutions of the present application will be further described in detail below with reference to the accompanying drawings and embodiments. SUMMARY

[0020] As described above, the present application provides a holmium-doped laser and a control method thereof, and effectively realizes 2 μm laser output with optimal optical-optical conversion efficiency by tuning the wavelength of pump light.

[0021] Exemplary apparatus

[0022] Fig. 1 is a schematic diagram of a holmium-doped laser according to an embodiment of the present application. As shown in Fig. 1, the holmium-doped laser 100 according to the present embodiment comprises a pump seed source 101, a pump source amplifier 102 and a spatial resonant cavity 103.

[0023] The pump seed source 101 is configured to generate pump seed light with tunable wavelength.

[0024] The pump source amplifier 102 is configured to amplify the pump seed light to obtain amplified pump light.

[0025] The spatial resonant cavity 103 is configured to convert the amplified pump light into output laser.

[0026] The pump seed source 101 is a wavelength-tunable ring cavity, which generates linearly polarized pump seed light with a center wavelength of 1930-2050 nm after oscillation. The pump source amplifier 102 is configured to amplify the power of the pump seed light to obtain polarization-maintained amplified pump light with tunable wavelength and high beam quality. The amplified pump light is then focused and coupled into the spatial resonant cavity 103 to obtain holmium-doped output laser with a center wavelength of 2000-2200 nm.

[0027] The output fiber end of the pump source amplifier 102 can be connected to an end cap for beam adjustment of the amplified pump light. The adjusted amplified pump light is input into the spatial resonant cavity 103.

[0028] The wavelength variation of the pump seed light affects the wavelength of the amplified pump light, and thus the power of the output laser. In a laser, the pump seed light (or seed laser) is the initial light source used to initiate the laser amplification process. The characteristics of the pump seed light, such as wavelength, frequency, and phase, all affect the characteristics of the final output laser.

[0029] Specifically, the gain medium of a laser typically has a specific gain band range. The wavelength of the pump seed light must fall within this range to be effectively amplified. If the wavelength of the pump seed light changes but still falls within the gain band of the gain medium, the wavelength of the amplified pump light will also change accordingly. In some tunable lasers, the wavelength of the amplified pump light can be tuned by adjusting the wavelength of the pump seed light, which is commonly used in applications that require precise control of the wavelength of the amplified pump light. In some laser systems, the wavelength variation of the pump seed light can also induce nonlinear effects, such as frequency conversion or optical parametric amplification, further affecting the wavelength of the amplified pump light.

[0030] Specifically, as shown in FIG. 2, the pump seed source 101 includes at least one first pump source 106, a first beam combiner 107, a first gain fiber 108, a tunable filter 109, and a fiber beam splitter 110.

[0031] The first pump source 106 is configured to provide initial pump light at a first wavelength.

[0032] To effectively pump the thulium-doped first gain fiber 108 and generate seed light in the desired wavelength range, the first wavelength is selected to be 793 nm. In a thulium-doped fiber, the thulium-doped fiber has high absorption efficiency at a wavelength of 793 nm, and longer wavelength light can be effectively generated through the upconversion process.

[0033] The first beam combiner 107 is configured to combine the initial pump light and part of the seed light from the fiber beam splitter 110 to obtain first combined light for subsequent amplification.

[0034] The main function of a beam combiner is to combine light from different sources into the same fiber for transmission. Typically, a fiber coupler or waveguide coupler is used to combine two optical signals into one fiber, forming a combined light. The beam combiner makes the optical path design more compact and efficient, reducing the amount of fiber used and optical path loss.

[0035] The first beam combiner 107 includes at least two first input ends and one first output end. The first beam combiner 107 receives optical signals from different sources through its multiple input ends and outputs the combined optical signals through its unique output end.

[0036] The multiple first input ends are respectively connected to the first pump fiber and the first signal input fiber.

[0037] The other end of the first pump fiber is connected with the first pump source 106 for transmitting the initial pump light. The core-clad diameter of the first pump fiber is 105 / 125.

[0038] The other end of the first signal input fiber is connected with the optical fiber coupler 110 for transmitting the partial seed light. The first signal input fiber is a polarization maintaining fiber with a core-clad diameter of 5 / 125. The partial seed light transmitted from the optical fiber coupler 110 is ensured to maintain a stable polarization state, thereby improving the coupling efficiency in the first coupler 107.

[0039] The first output end is connected with a first output fiber, and the other end of the first output fiber is connected with the first gain fiber 108 for transmitting the first coupled light after coupling. The first output fiber is a polarization maintaining fiber with a core-clad diameter of 5 / 125. The first coupled light after coupling is ensured to maintain a stable polarization state when transmitted to the first gain fiber 108, thereby improving the amplification efficiency and beam quality of the seed light.

[0040] In summary, the polarization maintaining fiber is used as the signal input fiber and the output fiber, which can maintain the polarization state of the transmitted light, reduce the change of the polarization state during transmission, and improve the beam quality, reduce the beam divergence and spot expansion, and help to improve the optical-to-optical conversion efficiency.

[0041] The first gain fiber 108 amplifies the partial seed light by using the initial pump light in the first coupled light to obtain the seed light.

[0042] The first gain fiber 108 is a thulium-doped polarization maintaining fiber with a core-clad diameter of 5 / 125. Similarly, the polarization maintaining fiber can effectively maintain the polarization state of the optical signal, improve the beam quality and output stability.

[0043] The gain bandwidth and operating wavelength range of the thulium-doped fiber are highly matched with the 2 μm band of the holmium-doped laser. The thulium ions can effectively absorb the pump light to excite the energy level transition and generate high-efficiency laser amplification in the 2 μm band.

[0044] The pump seed source 101 can further include a first stripper 111 located between the first gain fiber 108 and the tunable filter 109 for stripping the initial pump light that is not converted into the seed light and outputting to the tunable filter 109.

[0045] The first stripper 111 is a polarization maintaining fiber with stripped outer cladding, and the core-clad diameter is 5 / 125.

[0046] The tunable filter 109 is used to tune the wavelength of the seed light to obtain the second wavelength of the seed light with tunable wavelength.

[0047] The tunable filter 109 comprises a Bragg grating and an adjusting device.

[0048] The adjusting device adjusts the reflection wavelength of the Bragg grating, and outputs the seed light of the second wavelength. The adjusting device changes the reflection characteristics of the Bragg grating by physical means (such as mechanical stretching device or compression device) or optical means (such as strain, temperature, etc.), so as to adjust the wavelength of the reflected light. This adjustment enables the filter to selectively reflect or pass light of a certain wavelength, thereby outputting seed light of a target wavelength.

[0049] In order to achieve high optical-to-optical conversion efficiency covering the main absorption peak of the holmium-doped crystal, the wavelength tunable range of the seed light of the second wavelength is 1930-2050 nm.

[0050] The fiber beam splitter 110 is used to split the power of the seed light of the second wavelength according to a set splitting ratio to obtain the partial seed light and the pump seed light, and output them to the first beam combiner 107 and the pump source amplifier 102 respectively.

[0051] Specifically, the fiber beam splitter 110 splits the power of the seed light of the second wavelength according to a splitting ratio of 2:8 to obtain the partial seed light and the pump seed light. 20% of the power of the seed light is allocated as the partial seed light, and 80% of the power is allocated as the pump seed light. The partial seed light is sent back to the first beam combiner 107 for further pumping and amplification process, forming a feedback loop to enhance the stability and output consistency of the laser 100. The pump seed light is sent to the pump source amplifier 102 for further power amplification, ensuring that the finally output pump light has sufficient power to drive the subsequent spatial harmonic cavity 103. The splitting ratio of 2:8 ensures the overall energy utilization efficiency, ensuring that both the feedback and amplification processes can obtain sufficient optical power.

[0052] The pump seed source 101 can further comprise an isolator 112 located after the fiber beam splitter 110 and before the first beam combiner 112, for preventing the reverse propagation of the initial pump light and the partial seed light.

[0053] Since the power range of the tunable filter 109 is limited, the pump seed light needs to be adjusted to a suitable wavelength first, and then amplified in power by the pump source amplifier 102.

[0054] Specifically, the pump source amplifier 102 includes a pump source pre-amplifier 104 and at least one pump source main amplifier 105 for staging amplification of the pump seed light. The pump source pre-amplifier 104 is used to preliminarily amplify the pump seed light and boost its power to an intermediate level so as to enter the pump source main amplifier for higher power amplification. The pump source main amplifier 105 is used to further amplify the pre-amplified pump seed light at a high power to finally obtain the required high-power amplified pump light.

[0055] Staging amplification can gradually boost the power of the pump light, avoiding the efficiency reduction and equipment overload problems caused by single-stage amplification; and the amplification gain of each stage can be better controlled, thereby reducing nonlinear effects such as self-phase modulation and Raman scattering in the optical fiber; in addition, staging amplification allows the thermal load of each stage amplifier to be more evenly distributed, which helps heat dissipation and thermal management, maintaining overall stability and reliability; finally, the pump source main amplifier can be configured with multiple stages of amplifiers according to actual needs, providing greater flexibility and scalability to adapt to different power levels of laser applications.

[0056] As shown in FIG. 3, the pump source pre-amplifier 104 includes at least one second pump source 113, a second combiner 114, a second gain fiber 115, and a grating 116.

[0057] The second pump source 113 is used to provide enhanced pump light.

[0058] The second pump source 113 is a 793 nm pump source.

[0059] The second combiner 114 is used to combine the enhanced pump light from the second pump source 113 with the pump seed light to obtain second combined light.

[0060] The second combiner 114 includes at least two second input ends and one second output end.

[0061] The plurality of second input ends are respectively connected with a second pump fiber and a second signal input fiber, the other end of the second pump fiber is connected with the second pump source 113, and the other end of the second signal input fiber is connected with the optical fiber splitter 110.

[0062] The second output end is connected with a second output fiber, and the other end of the second output fiber is connected with the second gain fiber 115.

[0063] The core-clad diameter of the second pump fiber is 105 / 125.

[0064] The second signal input fiber is a polarization maintaining fiber, and the core-clad diameter thereof is 5 / 125.

[0065] The second output fiber is a polarization maintaining fiber with a core-clad diameter of 10 / 130.

[0066] The second gain fiber 115 amplifies the pump seed light using the enhanced pump light in the second combined light to obtain second pump seed light.

[0067] The second gain fiber 115 is a thulium-doped polarization maintaining fiber.

[0068] The core-clad diameter of the second gain fiber 115 is 10 / 130.

[0069] The grating 116 is used to strip the non-linear polarization state pump light in the second pump seed light to obtain pre-amplified pump seed light. By stripping these non-linear polarization state pump light, it can ensure that the output pre-amplified pump seed light is mainly linear polarization state, with better beam quality and stability.

[0070] The grating 116 is a Brewster fiber grating using a polarization maintaining fiber with a core-clad diameter of 10 / 130. The polarization maintaining fiber ensures that the grating can effectively maintain the polarization state of the optical signal and reduce the disturbance of the polarization state.

[0071] The Brewster fiber grating uses the principle of Brewster angle to only allow light of a specific polarization state to pass through, thereby achieving the stripping of non-linear polarization state pump light. This principle ensures the selectivity of the polarization state and improves the polarization purity of the optical signal.

[0072] Due to the limited power range of the grating 116, the pump source pre-amplifier 104 is needed to first increase the polarization purity of the pre-amplified pump seed light to a certain value in the pre-amplification stage, and then perform power amplification through the pump source main amplifier 105.

[0073] The pump source pre-amplifier 104 further includes a second stripper 117 for stripping the enhanced pump light that has not been converted into the second pump seed light and outputting it to the grating 116.

[0074] The second stripper 117 is a stripper outer cladding polarization maintaining fiber with a core-clad diameter of 10 / 130.

[0075] As shown in FIG. 4, the pump source main amplifier 105 includes a plurality of third pump sources 118, a third combiner 119, and a third gain fiber 120. Among them

[0076] The third pump source 118 is used to provide enhanced pump light.

[0077] The third pump source 118 is a 793 nm pump source.

[0078] The third combiner 119 is configured to combine the amplified pump light from the third pump source 118 and the pre-amplified pump seed light to obtain third combined light.

[0079] The third combiner 119 comprises a plurality of third input ends and a third output end.

[0080] The plurality of third input ends are respectively connected with a third pump fiber and a third signal input fiber, the other end of the third pump fiber is connected with the third pump source 118, and the other end of the third signal input fiber is connected with the grating 116.

[0081] The third output end is connected with a third output fiber, and the other end of the third output fiber is connected with the third gain fiber 120.

[0082] The core-clad diameter of the third pump fiber is 200 / 220.

[0083] The third signal input fiber is a polarization maintaining fiber, and the core-clad diameter thereof is 10 / 125.

[0084] The third output fiber is a polarization maintaining fiber, and the core-clad diameter thereof is 25 / 250 or 25 / 400.

[0085] The third gain fiber 120 amplifies the pre-amplified pump seed light by using the amplified pump light in the third combined light to obtain the amplified pump light of the second wavelength.

[0086] The third gain fiber 120 is a thulium-doped polarization maintaining fiber.

[0087] The core-clad diameter of the third gain fiber 120 is 25 / 250 or 25 / 400. For example, a polarization maintaining 25 / 250 thulium-doped gain fiber is used, and the corresponding 793 nm pump light absorption rate is 1-2 dB / m.

[0088] The pump source main amplifier 105 further comprises a third stripper 121 configured to strip the amplified pump light that is not converted into the amplified pump light and output to the spatial resonant cavity 103.

[0089] The third stripper 121 is a polarization maintaining fiber with stripped outer cladding, and the core-clad diameter thereof is 25 / 250.

[0090] As shown in FIG. 5, the spatial resonant cavity 103 comprises a focusing mirror 122, a polarizer 123, a planar cavity mirror 124, a holmium-doped crystal 125, and a planar concave mirror output mirror 126.

[0091] The focusing mirror 122 is used to focus the amplified pump light and focus it to the holmium-doped crystal 125 through the polarizer 123. That is, the focusing mirror 122 focuses the amplified pump light output from the pump source amplifier 102 into a small spot to increase the power density of the pump light, thereby enhancing the pumping efficiency; the amplified pump light focuses through the polarizer 123, further ensuring that the light beam enters the holmium-doped crystal 125 in the correct direction and polarization state.

[0092] The polarizer 123 is used to highly reflect the amplified pump light and highly reflect the first polarization direction of the oscillation light and highly transmit the second polarization direction of the oscillation light. For example, the polarizer 123, when placed at 45°, highly reflects the vertical polarization of the oscillation light and highly transmits the horizontal polarization of the oscillation light, and highly reflects the horizontal and vertical polarizations of the amplified pump light.

[0093] The polarizer 123 is a TFP polarizer (thin film polarizer) with high polarization selectivity and high damage threshold, suitable for high-power laser applications.

[0094] The holmium-doped crystal 125 is used to convert the amplified pump light into the output laser of the third wavelength. After absorbing the pump light, the holmium-doped crystal 125 emits a laser in the 2 μm (2000 nm) wavelength band through the stimulated emission process.

[0095] The third wavelength is 2000-2200 nm.

[0096] The holmium-doped crystal 125 is a Ho:YAG crystal. Compared with other holmium-doped materials, the Ho:YAG crystal performs best in 2 μm wavelength band lasers in terms of laser efficiency, thermal management, pump light utilization, stability, and maturity in practical applications. Therefore, selecting the Ho:YAG crystal can maximize the performance and reliability of the laser and meet the needs of a wide range of applications.

[0097] The planar cavity mirror 124 is placed at 0° and is used to highly transmit the pump light and highly reflect the oscillation light, ensuring that the oscillation light is reflected and amplified multiple times in the spatial resonant cavity 103.

[0098] The plano-concave mirror output mirror 126 is placed at 0° and is used to transmit a specified proportion of the oscillation light, allowing part of the oscillation light to exit the spatial resonant cavity 103 as output laser.

[0099] The specified proportion is 25%-35%.

[0100] The concave radius of curvature of the plano-concave mirror output mirror 126 is 290-310 mm, effectively controlling the divergence and focusing of the light beam.

[0101] The spatial resonant cavity 103 can also include a total reflection mirror 127 and a half-wave plate.

[0102] The total reflection mirror 127 is placed at 45° to reflect the amplified pump light focused by the focusing mirror 122 to the polarizer 123.

[0103] The half-wave plate is located behind the focusing mirror 122 to adjust the polarization angle of the amplified pump light. By adjusting the polarization angle, the polarization state of the amplified pump light can be optimized to meet the polarization requirements in the spatial resonator 103, improving the pumping efficiency and the quality of the output laser.

[0104] In addition, the spatial resonator 103 can have both sides as plane mirrors or both sides as concave mirrors, in addition to one side as a plane mirror and the other side as a concave mirror, depending on the specific application requirements and design requirements of the laser. The design of one side as a plane mirror and the other side as a concave mirror is more common because the concave mirror can provide better beam focusing and improve the stability of the resonator. The design of both sides as plane mirrors is relatively simple, but requires higher accuracy in the position and alignment of the mirrors, which can easily lead to instability. The design of both sides as concave mirrors can further improve the stability of the resonator and the quality of the beam, but requires a more stringent requirement for the radius of curvature of the mirrors.

[0105] One of the advantages of using curved mirrors (concave mirrors) is that it can better control and focus the laser beam, thereby improving the stability of the resonator and the quality of the output beam. In high-power and high-precision lasers, plane-concave or concave-concave resonator designs are more common to meet higher stability and beam quality requirements.

[0106] The laser 100 further comprises a control unit for adjusting the wavelength of the pump seed light input to the pump source amplifier 102 and / or directly adjusting the wavelength of the pump seed light input to the pump source amplifier 102 according to the power of the output laser;

[0107] The laser 100 further comprises a frequency detection device and / or an output power detection device; wherein

[0108] The frequency detection device is used to detect the wavelength of the pump seed light;

[0109] The output power detection device is used to detect the power of the output laser.

[0110] In particular, the control unit is used to adjust the wavelength of the pump seed light so that the power of the output laser is the highest or directly adjust the wavelength of the pump seed light to a specified wavelength.

[0111] The specified wavelength is an empirical value determined through a large number of experiments and data analysis. The specific steps can include: first, adjusting the wavelength of the pump seed light before the laser 100 leaves the factory, and recording the output laser power at each wavelength; second, using the frequency detection device and the output power detection device to monitor and record data in real time; third, drawing a curve of the relationship between the wavelength of the pump seed light and the output laser power, and finding the optimal wavelength range; fourth, fine adjustment and testing within the optimal wavelength range, and repeating the experimental verification results; and finally, summarizing the optimal pump seed light wavelength empirical value and recording it in the control unit.

[0112] The method of directly adjusting the wavelength of the pump seed light to the specified wavelength based on the specified wavelength does not require detection of the power of the output laser compared to adjusting the wavelength of the pump seed light so that the power of the output laser is the highest.

[0113] Through real-time monitoring of the frequency detection device and the output power detection device, combined with the adjustment function of the control unit, the output power of the laser and the wavelength of the pump seed light can be accurately controlled. The adjustment mechanism of the present application not only optimizes the performance of the laser to achieve the highest output power, but also continuously adjusts the pump seed light to the specified wavelength according to specific requirements, avoiding the trouble of replacing different wavelength pump seed sources, and increasing the flexibility and applicability of the laser.

[0114] Exemplary method

[0115] Correspondingly, the embodiment of the present application also provides a control method of a holmium-doped laser. FIG. 6 is a flow chart of the control method of the holmium-doped laser provided by the embodiment of the present application, which includes the following steps:

[0116] S601: detecting the wavelength of the pump seed light and / or detecting the power of the output laser;

[0117] S602: adjusting the wavelength of the amplified pump seed light according to the power of the output laser of the holmium-doped laser and / or directly adjusting the wavelength of the pump seed light input into the pump source amplifier.

[0118] Specifically, the wavelength of the pump seed light is adjusted so that the power of the output laser is the highest or the wavelength of the pump seed light is directly adjusted to the specified wavelength by adjusting the working parameters (for example, pressure, deformation degree, etc.) of the tunable filter 109.

[0119] The specified wavelength is an empirical value determined through a large number of experiments and data analysis. The specific steps can include: first, adjusting the wavelength of the pump seed light before the laser 100 leaves the factory, and recording the output laser power at each wavelength; second, using a frequency detection device and an output power detection device to monitor and record data in real time; third, drawing a curve of the relationship between the wavelength of the pump seed light and the output laser power, and finding the optimal wavelength range; then, fine adjustment and testing are carried out in the optimal wavelength range, and the experimental results are repeatedly verified; finally, the optimal pump seed light wavelength is summarized as an empirical value and recorded in the control unit.

[0120] It should be noted that although several means, units, or modules of the holmium-doped laser are mentioned in the foregoing detailed description, such division is merely exemplary and not mandatory. Indeed, according to embodiments of the application, the features and functions of two or more modules described above can be embodied in one module. Conversely, the features and functions of one module described above can be further divided into modules embodied by multiple modules.

[0121] Furthermore, although the operations of the control method of the holmium-doped laser of the present application are described in a particular order in the accompanying drawings, this is not required or implied in any way as to the order or as to the necessity of performing all of the operations to achieve desirable results. Additionally or alternatively, certain steps can be omitted, multiple steps can be combined into one step, and / or one step can be divided into multiple steps.

[0122] While the principles and uses of the present application have been described in particular embodiments, it is understood that numerous modifications can be made to the embodiments described above, and that the principles and concepts of the present application can be applied to other embodiments without departing from the spirit and scope of the application. The present application is not limited to the embodiments described above, but rather is intended to encompass all modifications and equivalents thereof within the spirit and scope of the appended claims.

[0123] The present application provides:

[0124] 1、 A holmium-doped laser, characterized in that the laser comprises a pump seed source, a pump source amplifier, and a spatial resonant cavity; wherein

[0125] The pump seed source is configured to generate pump seed light with tunable wavelength.

[0126] The pump source amplifier is configured to amplify the pump seed light to obtain amplified pump light.

[0127] The spatial resonant cavity is configured to convert the amplified pump light into output laser.

[0128] 2. The laser of item 1, wherein the pump seed source comprises at least one first pump source, a first combiner, a first gain fiber, a tunable filter and a fiber splitter; wherein

[0129] the first pump source is configured to provide initial pump light at a first wavelength;

[0130] the first combiner is configured to combine the initial pump light and a portion of seed light from the fiber splitter to obtain first combined light;

[0131] the first gain fiber is configured to amplify the portion of seed light using the initial pump light in the first combined light to obtain seed light;

[0132] the tunable filter is configured to tune the wavelength of the seed light to obtain seed light at a second wavelength that is tunable;

[0133] the fiber splitter is configured to split the power of the seed light at the second wavelength according to a set splitting ratio to obtain the portion of seed light and the pump seed light, and output them to the first combiner and the pump source amplifier, respectively.

[0134] 3. The laser of item 2, wherein the tunable wavelength range of the seed light at the second wavelength is 1930-2050 nm.

[0135] 4. The laser of item 2 or 3, wherein the tunable filter comprises a Bragg grating and an adjusting device;

[0136] the adjusting device is configured to adjust the reflection wavelength of the Bragg grating to output the seed light at the second wavelength.

[0137] 5. The laser of item 2 or 3, wherein the pump seed source further comprises a first stripper configured to strip the initial pump light that is not converted into the seed light and output it to the tunable filter;

[0138] the first stripper is a polarization maintaining fiber with stripped outer cladding, and has a core cladding diameter of 5 / 125.

[0139] 6. The laser of item 2 or 3, wherein the first wavelength is 793 nm.

[0140] 7. The laser of item 2 or 3, wherein the first gain fiber is a thulium-doped polarization maintaining fiber;

[0141] the first gain fiber has a core cladding diameter of 5 / 125.

[0142] 8. The laser of any of claims 2 or 3, wherein the first combiner comprises at least two first input ends and one first output end.

[0143] The at least two first input ends are respectively connected with a first pump fiber and a first signal input fiber, the other end of the first pump fiber is connected with the first pump source, and the other end of the first signal input fiber is connected with the fiber splitter.

[0144] The first output end is connected with a first output fiber, and the other end of the first output fiber is connected with the first gain fiber.

[0145] 9. The laser of claim 8, wherein the first pump fiber has a core-clad diameter of 105 / 125.

[0146] The first signal input fiber is a polarization maintaining fiber, and has a core-clad diameter of 5 / 125.

[0147] The first output fiber is a polarization maintaining fiber, and has a core-clad diameter of 5 / 125.

[0148] 10. The laser of any of claims 2 or 3, wherein the fiber splitter splits the seed light of the second wavelength according to a splitting ratio of 2:8 to obtain the partial seed light and the pump seed light.

[0149] 11. The laser of any of claims 1-3, wherein the pump source amplifier comprises a pump source pre-amplifier and at least one stage of pump source main amplifiers, and is configured to amplify the pump seed light in stages.

[0150] 12. The laser of claim 11, wherein the pump source pre-amplifier comprises at least one second pump source, a second combiner, a second gain fiber, and an optical grating.

[0151] The second pump source is configured to provide enhanced pump light.

[0152] The second combiner is configured to combine the enhanced pump light from the second pump source with the pump seed light to obtain second combined light.

[0153] The second gain fiber amplifies the pump seed light using the enhanced pump light in the second combined light to obtain second pump seed light.

[0154] The optical grating is configured to remove non-linear polarization state pump light from the second pump seed light to obtain pre-amplified pump seed light.

[0155] 13. The laser of claim 12, wherein the grating is a Bragg fiber grating using a polarization maintaining fiber with a core-clad diameter of 10 / 130.

[0156] 14. The laser of claim 12, wherein the pump source pre-amplifier further comprises a second stripper for stripping the enhanced pump light that is not converted into the second pump seed light and outputting to the grating.

[0157] The second stripper is a polarization maintaining fiber stripper that strips the outer cladding.

[0158] 15. The laser of claim 12, wherein the second pump source is a 793 nm pump source.

[0159] 16. The laser of claim 12, wherein the second gain fiber is a thulium-doped polarization maintaining fiber.

[0160] The second gain fiber has a core-clad diameter of 10 / 130.

[0161] 17. The laser of claim 12, wherein the second combiner comprises at least two second input ends and one second output end.

[0162] The second input ends are respectively connected to a second pump fiber and a second signal input fiber, the other end of the second pump fiber is connected to the second pump source, and the other end of the second signal input fiber is connected to the fiber splitter.

[0163] The second output end is connected to a second output fiber, and the other end of the second output fiber is connected to the second gain fiber.

[0164] 18. The laser of claim 17, wherein the second pump fiber has a core-clad diameter of 105 / 125.

[0165] The second signal input fiber is a polarization maintaining fiber with a core-clad diameter of 5 / 125.

[0166] The second output fiber is a polarization maintaining fiber with a core-clad diameter of 10 / 130.

[0167] 19. The laser of claim 11, wherein the pump source main amplifier comprises a plurality of third pump sources, a third combiner, and a third gain fiber, wherein

[0168] The third pump sources are configured to provide enhanced pump light.

[0169] The third combiner is used for combining the enhanced pump light from the third pump source with the pre-amplified pump seed light to obtain third combined light;

[0170] The third gain fiber amplifies the pre-amplified pump seed light by using the enhanced pump light in the third combined light to obtain the amplified pump light of the second wavelength.

[0171] 20. The laser of claim 19, wherein the pump source master amplifier further comprises a third stripper for stripping the enhanced pump light that is not converted into the amplified pump light and outputting to the spatially resonant cavity.

[0172] The third stripper is a polarization maintaining fiber with stripped outer cladding, and the core cladding diameter is 25 / 250.

[0173] 21. The laser of claim 19, wherein the third pump source is a 793 nm pump source.

[0174] 22. The laser of claim 19, wherein the third gain fiber is a thulium-doped polarization maintaining fiber.

[0175] The core cladding diameter of the third gain fiber is 25 / 250 or 25 / 400.

[0176] 23. The laser of claim 19, wherein the third combiner comprises a plurality of third input ends and a third output end.

[0177] The plurality of third input ends are respectively connected with a third pump fiber and a third signal input fiber, the other end of the third pump fiber is connected with the third pump source, and the other end of the third signal input fiber is connected with the grating.

[0178] The third output end is connected with a third output fiber, and the other end of the third output fiber is connected with the third gain fiber.

[0179] 24. The laser of claim 19, wherein the core cladding diameter of the third pump fiber is 200 / 220.

[0180] The third signal input fiber is a polarization maintaining fiber with a core cladding diameter of 10 / 125.

[0181] The third output fiber is a polarization maintaining fiber with a core cladding diameter of 25 / 250 or 25 / 400.

[0182] 25. The laser of claim 1 or 2, wherein the spatially resonant cavity comprises a focusing mirror, a polarizer, a planar cavity mirror, a holmium-doped crystal, and a plano-concave output mirror; wherein

[0183] The focusing mirror is used for focusing the amplified pump light and focusing it to the holmium-doped crystal through the polarizer;

[0184] The polarizer is used for high reflection of the amplified pump light, high reflection of polarized light of the first polarization direction of the oscillation light, and high transmission of polarized light of the second polarization direction;

[0185] The holmium-doped crystal is used for converting the amplified pump light into the output laser of the third wavelength;

[0186] The plane cavity mirror is used for high transmission of the pump light and high reflection of the oscillation light;

[0187] The plane-concave mirror output mirror is used for specified proportion transmission of the oscillation light.

[0188] 26. The laser according to item 25, characterized in that the radius of curvature of the concave surface of the plane-concave mirror output mirror is 290-310 mm.

[0189] 27. The laser according to item 25, characterized in that the holmium-doped crystal is a Ho:YAG crystal.

[0190] 28. The laser according to item 25, characterized in that the spatial resonator further comprises a total reflection mirror and a half-wave plate;

[0191] The total reflection mirror is used for reflecting the amplified pump light focused by the focusing mirror to the polarizer;

[0192] The half-wave plate is used for adjusting the polarization angle of the amplified pump light.

[0193] 29. The laser according to item 25, characterized in that the specified proportion is 25-35%.

[0194] 30. The laser according to item 25, characterized in that the polarizer is a TFP polarizer.

[0195] 31. The laser according to item 25, characterized in that the third wavelength is 2000-2200 nm.

[0196] 32. The laser according to item 1 or item 2, characterized in that the laser further comprises a control unit for adjusting the wavelength of the pump seed light input into the pump source amplifier and / or directly adjusting the wavelength of the pump seed light input into the pump source amplifier according to the power of the output laser;

[0197] The laser further comprises a frequency detection device and / or an output power detection device; wherein

[0198] The frequency detecting device is used to detect the wavelength of the pump seed light.

[0199] The output power detecting device is used to detect the power of the output laser.

[0200] 33. The laser according to item 32, wherein the control unit is used to adjust the wavelength of the pump seed light so that the power of the output laser is the highest or directly adjust the wavelength of the pump seed light to a specified wavelength.

[0201] 34. A control method of a holmium-doped laser according to any one of items 1-33, wherein the method comprises:

[0202] detecting the wavelength of the pump seed light and / or detecting the power of the output laser;

[0203] adjusting the wavelength of the amplified pump seed light according to the power of the output laser of the holmium-doped laser and / or directly adjusting the wavelength of the pump seed light input to the pump source amplifier.

[0204] 35. The control method according to item 34, wherein the step of adjusting the wavelength of the amplified pump seed light according to the power of the output laser of the holmium-doped laser is specifically adjusting the wavelength of the pump seed light so that the power of the output laser is the highest or directly adjusting the wavelength of the pump seed light to a specified wavelength.

Claims

1. A holmium-doped laser, characterized by, The laser comprises a pump seed source, a pump source amplifier and a spatial resonant cavity; wherein The pump seed source is configured to generate pump seed light with tunable wavelength; The pump source amplifier is configured to amplify the pump seed light to obtain amplified pump light; The spatial resonant cavity is configured to convert the amplified pump light into output laser light.

2. The laser of claim 1, wherein, The pump seed source comprises at least one first pump source, a first combiner, a first gain fiber, a tunable filter and a fiber splitter; wherein The first pump source is configured to provide initial pump light with a first wavelength; The first combiner is configured to combine the initial pump light and part of seed light from the fiber splitter to obtain first combined light; The first gain fiber amplifies the part of seed light by using the initial pump light in the first combined light to obtain seed light; The tunable filter is configured to tune the wavelength of the seed light to obtain seed light with a second wavelength with tunable wavelength; The fiber splitter is configured to split the power of the seed light with the second wavelength according to a set splitting ratio to obtain the part of seed light and the pump seed light, and output them to the first combiner and the pump source amplifier respectively.

3. The laser of claim 2, wherein, The tunable wavelength range of the seed light with the second wavelength is 1930-2050 nm.

4. The laser of claim 2 or 3, wherein, The tunable filter comprises a Bragg grating and an adjusting device; The adjusting device is configured to adjust the reflection wavelength of the Bragg grating to output the seed light with the second wavelength.

5. The laser of claim 2 or 3, wherein, The pump seed source further comprises a first stripper configured to strip the initial pump light that is not converted into the seed light and output it to the tunable filter; The first stripper is a polarization maintaining fiber with stripped outer cladding, and the core cladding diameter thereof is 5 / 125.

6. The laser of claim 2 or 3, wherein, The first wavelength is 793 nm.

7. The laser of claim 2 or 3, wherein, The first gain fiber is a thulium-doped polarization maintaining fiber; The core cladding diameter of the first gain fiber is 5 / 125.

8. The laser of claim 2 or 3, wherein, The first combiner comprises at least two first input ends and one first output end; The first input ends are respectively connected with a first pump fiber and a first signal input fiber, the other end of the first pump fiber is connected with the first pump source, and the other end of the first signal input fiber is connected with the fiber splitter; The first output end is connected with a first output fiber, and the other end of the first output fiber is connected with the first gain fiber.

9. The laser of claim 8, wherein, The core cladding diameter of the first pump fiber is 105 / 125; The first signal input fiber is a polarization maintaining fiber, and the core cladding diameter thereof is 5 / 125; The first output fiber is a polarization maintaining fiber, and the core cladding diameter thereof is 5 / 125.

10. A control method of a holmium-doped laser as claimed in any one of claims 1 to 9, characterized in that, The method comprises: detecting the wavelength of the pump seed light and / or detecting the power of the output laser light; adjusting the wavelength of the amplified pump seed light and / or directly adjusting the wavelength of the pump seed light input into the pump source amplifier according to the power of the output laser light of the holmium-doped laser.

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