Passively q-switched pulsed fiber gas laser

Abstract

In view of the fact that in traditional fiber gas laser, pulse output needs to rely on high-cost pulse pumping source to be realized or to be realized through active Q switching technology, the application provides a kind of passive Q modulation pulse fiber gas laser, comprising pumping source, output coupling mirror, input gas sealed cavity, hollow optical fiber, gain gas, saturable absorber mirror, output gas sealed cavity, passive Q switching is realized in combination with fiber gas laser and saturable absorber mirror, pulse generation is automatically realized by using nonlinear optical characteristics of saturable absorber mirror, and the structure is simple, without external driving, and suitable for miniaturization and integration.

Description

TECHNICAL FIELD

[0001] The present application mainly relates to the technical field of fiber laser, in particular to a passive Q-modulated pulsed fiber gas laser. BACKGROUND

[0002] Fiber lasers have great development prospects in the field of lasers due to high beam quality, excellent thermal management, compact structure and high-efficiency pump conversion efficiency, especially in the fields of industrial processing, national defense and medical treatment. The number of applications of high-peak-power and narrow-pulse-width lasers is rapidly increasing. However, pure fiber systems are easily limited by nonlinear effects (such as stimulated Brillouin scattering) when outputting high-peak-power. Gas lasers based on hollow-core fibers are a new type of laser light source developed with the emergence of hollow-core fibers, which combines the advantages of traditional gas lasers and fiber lasers. Fiber gas lasers use hollow-core fibers as the transmission carrier of laser and use gas molecules as the gain medium, which can make up for the deficiency of fiber in a specific waveband (such as mid-infrared), have a longer action distance and a higher damage threshold, and can output different wavelengths of laser by replacing different types of gain gas (such as C2H2, CO, HBr, etc.).

[0003] As for pulsed fiber lasers, they have the characteristics of high peak power and have specific application scenarios in the fields of precision cutting, laser surgery, tissue cutting, and photoelectric countermeasures. However, the means for realizing pulsed output of fiber gas lasers is very limited. One method is to rely on a pulsed output laser as a pump source to realize pulsed output. This technical means completely depends on the performance of the pump source and cannot flexibly adjust the output repetition frequency, pulse width, and peak power of the pulsed fiber gas laser, which is lower than that of the pump source. The system is complex, the device is large, and the cost of the pulsed pump source is high. Another method is active Q-switching technology, which uses active Q-switching devices such as acousto-optic crystals, electro-optic crystals and choppers to realize pulsed fiber gas lasers. However, this technical method relies on complex external modulators, the system is large in size, the realization of pulsed output needs to rely on active devices, and the cost is high. The system is mostly a spatial optical path, and the active device increases the complexity of the system and makes the device cumbersome and susceptible to environmental interference. SUMMARY

[0004] In view of the technical problems existing in the prior art, the present application provides a passive Q-modulated pulsed fiber gas laser. The passive Q-switched pulsed fiber gas laser of the present application automatically realizes pulsed output by using the nonlinear optical properties of a saturable absorber mirror, which is simple in structure, does not need external driving, and is suitable for miniaturization and integration.

[0005] To achieve the above-mentioned purposes, the technical solutions adopted by the present application are as follows:

[0006] The passive Q-modulated pulse fiber gas laser comprises a pump source, an output coupling mirror, an input gas sealed cavity, an air core optical fiber, a gain gas, a saturable absorber mirror and an output gas sealed cavity; two ends of the air core optical fiber are respectively sealed by the input gas sealed cavity and the output gas sealed cavity, and the core of the air core optical fiber is filled with the gain gas; the output coupling mirror, the input gas sealed cavity, the air core optical fiber, the saturable absorber mirror and the output gas sealed cavity constitute a resonant cavity, the saturable absorber mirror is used as a passive Q-switching device, the saturable absorber mirror comprises a saturable absorber, a mirror and a substrate, the absorption coefficient of the saturable absorber decreases with the increase of the intensity of incident light, and the absorption bandwidth of the saturable absorber on the saturable absorber mirror is adjusted to realize different waveband pulse fiber gas laser outputs.

[0007] Further, the saturable absorber and the mirror are sequentially grown on the substrate, when the intensity of incident laser on the saturable absorber is less than a set threshold, the incident laser is absorbed by the saturable absorber and cannot reach the mirror; when the intensity of incident laser on the saturable absorber is greater than or equal to the set threshold, the absorption of the saturable absorber to the incident laser is small, and the laser can pass through the saturable absorber and be incident on the mirror, after reflection of the mirror, the reflected laser passes through the saturable absorber and returns along the original path.

[0008] Preferably, after the pump light enters the air core optical fiber, the gain gas absorbs the pump light energy to cause population inversion, and then generates output laser through energy level transition, and the laser spectrum of the output laser contains two wavelength components, which are first wavelength output laser and second wavelength output laser, the first wavelength is less than the second wavelength, the cutoff wavelength of the absorption bandwidth of the saturable absorber is controlled to realize simultaneous output of pulse fiber gas laser and continuous fiber gas laser, when the absorption bandwidth of the saturable absorber is cut off to the first wavelength, the absorption of the second wavelength output laser at the second wavelength can be ignored, at this time, the first wavelength output laser realizes pulse output by using the saturable absorber, and the second wavelength output laser realizes continuous laser mode output because the saturable absorber has high transmittance to the second wavelength output laser. In this way, the present application realizes simultaneous output of pulse / continuous fiber gas laser.

[0009] Further, the present application further comprises a pump light coupling system and a dichroic mirror, and the pump source, the pump light coupling system, the dichroic mirror and the output coupling mirror are sequentially arranged.

[0010] The pump light coupling system is used for efficiently coupling the pump light output by the pump source into the core of the air core optical fiber; the dichroic mirror has high transmittance to the pump light and high reflectivity to the laser generated by the resonant cavity.

[0011] Further, the pump light coupling system comprises a pump light collimating lens and a pump light focusing lens; the pump light collimating lens collimates the pump light emitted by the pump source into parallel light, and the pump light focusing lens efficiently couples the collimated pump light into the core of the hollow core fiber.

[0012] Further, the output coupling mirror is a plane mirror, has high transmittance for the pump light and partial transmittance for the laser generated by the resonant cavity.

[0013] Further, the output coupling mirror is arranged on a side wall of the input gas sealed cavity, and the saturable absorption mirror is arranged in the output gas sealed cavity.

[0014] Further, when the pump light output by the pump source starts to be injected into the core of the hollow core fiber, the laser intensity generated in the resonant cavity is small in the initial state, the laser is strongly absorbed by the saturable absorber after being incident on the saturable absorber, and the resonant cavity has large loss and cannot realize laser amplification output.

[0015] Under the continuous pumping of the pump light, the laser intensity generated in the resonant cavity gradually increases, and the absorption coefficient of the saturable absorber decreases, at this time, the laser passes through the saturable absorber to the mirror with low loss, further, the laser is reflected by the mirror and passes through the saturable absorber again with low loss, the reflected laser enters the hollow core fiber and is transmitted to the output coupling mirror, and part of the laser passes through the output coupling mirror and is reflected by the dichroic mirror to become the final output laser.

[0016] Further, the application further comprises a gas filling and pumping device for pumping the hollow core fiber through the input gas sealed cavity and the output gas sealed cavity.

[0017] Further, the hollow core fiber has low transmission loss for the pump light laser waveband and the laser waveband generated by the resonant cavity.

[0018] Further, the pump source is a tunable, narrow-line-width continuous laser source, and the output wavelength corresponds to the absorption peak of the used gain gas.

[0019] In order to solve the problems that the prior art fiber gas laser completely depends on the performance of the pump source, cannot flexibly adjust the output repetition frequency and pulse width, the peak power of the pulse output obtained by the fiber gas laser cannot exceed the peak power of the pump source, the system is complex and cumbersome due to the external driving device in the active Q-switched pulse fiber gas laser, and the fiber gas laser cannot realize simultaneous output of pulse / continuous fiber gas laser, the application provides a passive Q-modulated pulse fiber gas laser, compared with the prior art, the technical effects of the application are:

[0020] Q-switching technology is a method for generating high peak power pulses by periodically changing the Q value (quality factor) of the laser resonant cavity. The principle is: in the pumping stage, the laser oscillation is actively inhibited (low Q value, energy is stored in the gain medium), and when the energy accumulates to the saturation threshold, the high Q value is suddenly restored, so that the stored energy is released in a very short time, forming a nanosecond, megawatt level pulse. In the traditional fiber gas laser, pulse output needs to rely on high-cost pulse pumping source to achieve or through active Q-switching technology to achieve. The fiber gas laser has the characteristics of flexible output wavelength, and the present application combines the fiber gas laser and the saturable absorber to realize passive Q-switching, and proposes a pulse laser obtaining technology applicable in multiple wave bands.

[0021] The present application adopts an oscillator structure, adopts a saturable absorber as a passive Q-switching device, and obtains pulse output by adjusting the Q value of the resonant cavity. The saturable absorber realizes passive Q-switching, which belongs to a passive Q-switching technology, and other passive devices such as organic dye can also be replaced to realize passive Q-switching.

[0022] The passive Q-switching technology of the present application realizes pulse output without the aid of external modulation devices, and the pumping source can use a continuous wave output laser source, so that the dependence on the performance of the pumping source is less, the requirements on the pumping are reduced, the system complexity is reduced, and the cost is reduced.

[0023] The passive Q-switching technology proposed in the present application can realize flexible adjustment of the repetition frequency and pulse width of the pulse laser by changing the size of the pumping power or the parameters of the passive Q-switching device.

[0024] The present application realizes simultaneous output of pulse / continuous fiber gas laser by designing the saturable absorber absorption bandwidth, and the working mode is more flexible.

[0025] The present application can obtain pulse output without pulse pumping source and external driving device, reduces the system cost, and reduces the complexity of the device. The Q-switching technology adopted in the present application is not affected by the output wavelength, and is applicable in multiple wave bands, and has wider applicability. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or 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 also be obtained according to the structures shown in the drawings without creative labor for those skilled in the art.

[0027] Figure 1 It is a structural schematic diagram of passive Q-modulated pulse fiber gas laser in an embodiment;

[0028] Figure 2 Figure 1 is a structural schematic diagram of a passive Q-modulated pulsed fiber gas laser in an embodiment;

[0029] Figure 3 Figure 2 is a schematic diagram of a saturable absorber;

[0030] Figure 4 Figure 3 is an output spectrum diagram of an acetylene fiber gas laser;

[0031] Figure 1 is a structural schematic diagram of a passive Q-modulated pulsed fiber gas laser in an embodiment;

[0032] 1 is a pump source; 2 is a pump collimating lens; 3 is a pump focusing lens; 4 is a dichroic mirror; 5 is output laser; 6 is an output coupling mirror; 7 is an input gas sealed cavity; 8 is a hollow core fiber; 9 is laser light emitted from an output end of the hollow core fiber; 10 is a saturable absorber; 11 is an output gas sealed cavity; 12 is a window sheet; 13 is a gas filling and pumping device;

[0033] 101 is a saturable absorber; 102 is a mirror; 103 is a substrate. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0035] Reference Figure 1 Figure 1 is a structural schematic diagram of a passive Q-modulated pulsed fiber gas laser in an embodiment, including a pump source, an output coupling mirror 6, an input gas sealed cavity 7, a hollow core fiber 8, a gain gas, a saturable absorber 10, and an output gas sealed cavity 11. The input gas sealed cavity 7 and the output gas sealed cavity 11 are connected with a gas filling and pumping device 13, which is used to perform vacuumizing and filling of the gain gas on the hollow core fiber 8. The gas filling and pumping device 13 includes a vacuum pump, a gas cylinder, a gas pressure gauge, etc., and can perform the operations of vacuumizing and filling on the hollow core fiber 8, and can also adjust and detect the gas pressure of the gain gas in the hollow core fiber. The input gas sealed cavity 7 and the output gas sealed cavity 11 are located at two ends of the hollow core fiber 8, and are used to seal the gas molecules in the hollow core fiber 8; the hollow core fiber 8 can effectively confine the pump light in the core of the hollow core fiber 8, and provide an effective interaction distance between the pump light and the gain gas; the gas filling and pumping device 13 performs vacuumizing and filling of the gain gas with appropriate pressure on the hollow core fiber 8 through the input gas sealed cavity 7 and the output gas sealed cavity 11.

[0036] The pump source is a tunable, narrow-linewidth continuous laser source, and the output wavelength corresponds to the absorption peak of the used gain gas.

[0037] The two ends of the hollow core fiber 8 are respectively sealed by an input gas sealing cavity 7 and an output gas sealing cavity 11, and the core of the hollow core fiber 8 is filled with gain gas; the output coupling mirror 6, the input gas sealing cavity 7, the hollow core fiber 8, the saturable absorption mirror 10 and the output gas sealing cavity 11 constitute a resonant cavity, and the saturable absorption mirror 10 functions as a Q-switching device to realize pulsed laser generation. The hollow core fiber 8 has low transmission loss for laser in the pump light laser band and the laser band generated by the resonant cavity. The type of gain gas is not limited, such as C2H2, CO, HBr, etc.

[0038] The output coupling mirror 6 is arranged on one side wall of the input gas sealing cavity 7, and the output coupling mirror 6 is a plane mirror, which has high transmittance for pump light and partial transmittance for laser generated by the resonant cavity. The saturable absorption mirror 10 is arranged in the output gas sealing cavity 11, and the output gas sealing cavity 11 is sealed by a window sheet 12, which is a plane mirror sheet and is used to fix and arrange the saturable absorption mirror 10.

[0039] The saturable absorption mirror 10 is a passive device, which includes a saturable absorber and a mirror. The saturable absorber has a decreasing absorption coefficient with increasing incident light intensity, and its absorption bandwidth can be adjusted. The mirror has high reflectivity for laser in the pump light laser band and the laser band generated by the resonant cavity. By adjusting the absorption bandwidth of the saturable absorber on the saturable absorption mirror, pulsed fiber gas laser output in different bands can be realized. By controlling the cutoff wavelength of the absorption bandwidth of the saturable absorber, pulsed fiber gas laser and continuous fiber gas laser can be simultaneously output.

[0040] The saturable absorption mirror 10 is as shown in Figure 3As shown, it comprises a saturable absorber 101, a mirror 102 and a substrate 103, the saturable absorber 101 and the mirror 102 are grown on the substrate 103 in sequence. The saturable absorber 101 is an optical nonlinear material, whose absorption coefficient will decrease with the increase of the incident light intensity, and finally reaches a "saturated" state (i.e. the absorption capacity is significantly weakened or almost not absorbed). The absorption coefficient of the saturable absorber 101 decreases with the increase of the incident light intensity, when the laser intensity incident on the saturable absorber 101 is small, the incident laser is absorbed by the saturable absorber 101 and cannot reach the mirror 102; when the laser intensity incident on the saturable absorber 101 is strong enough, the absorption of the saturable absorber 101 to the incident laser is small, and the laser can pass through the saturable absorber 101 and be incident on the mirror 102, after reflection of the mirror 102, the reflected laser passes through the saturable absorber 101 and returns along the original path.

[0041] When the pump light output by the pump source begins to inject into the core of the hollow core optical fiber 8, the initial state of the laser intensity generated in the resonant cavity is small, and after the laser is incident on the saturable absorber mirror 10, it is strongly absorbed by the saturable absorber 101, and the resonant cavity loss is large and cannot realize laser amplification output;

[0042] Under the continuous pumping of the pump light, the laser intensity generated in the resonant cavity gradually increases, and the absorption coefficient of the saturable absorber 101 decreases, at this time the laser passes through the saturable absorber to the mirror 102 with low loss, further, after the laser is reflected by the mirror 102, it will also pass through the saturable absorber 101 again with low loss, the reflected laser enters the hollow core optical fiber 8 and is transmitted to the output coupling mirror 6, part of the laser is output after passing through the output coupling mirror 6.

[0043] Referring to Figure 2Fig. 1 is a schematic diagram of a passive Q-switched pulsed fiber gas laser according to an embodiment of the present application. The passive Q-switched pulsed fiber gas laser comprises a pump source 1, a pump light coupling system, a dichroic mirror 4, an output coupling mirror 6, an input gas sealed cavity 7, a hollow core fiber 8, a gain gas, a saturable absorber mirror 10, an output gas sealed cavity 11, a window sheet 12, and a gas filling and pumping device 13. The pump light coupling system is used to couple the pump light outputted from the pump source into the core of the hollow core fiber efficiently. The dichroic mirror 4 is a dichroic mirror, which has high transmittance for the pump light and high reflectance for the laser light generated in the resonant cavity, thereby separating the pump light and the final output laser light 5. The pump light coupling system comprises a pump light collimating lens 2 and a pump light focusing lens 3. The pump light collimating lens 2 collimates the pump light outputted from the pump source 1 into parallel light, and the pump light focusing lens 3 couples the collimated pump light into the core of the hollow core fiber 8 efficiently. The pump source 1, the pump light collimating lens 2, the pump light focusing lens 3, the dichroic mirror 4, and the output coupling mirror 6 are arranged in sequence. The output coupling mirror 6, the input gas sealed cavity 7, the hollow core fiber 8, the gain gas, the saturable absorber mirror 10, the output gas sealed cavity 11, the window sheet 12, and the gas filling and pumping device 13 are arranged in the same way as in the previous embodiment, and thus will not be described again.

[0044] The pump source 1 outputs pump light with a wavelength corresponding to the absorption peak of the gain gas molecules. The pump light collimating lens 2 collimates the pump light into parallel light. The pump light focusing lens 3 couples the collimated pump light into the hollow core fiber 8. The dichroic mirror 4 has high transmittance for the pump light and high reflectance for the laser light generated in the resonant cavity. The output coupling mirror 6 has high transmittance for the pump light and partial transmittance for the laser light generated in the resonant cavity. The hollow core fiber 8 provides an ideal environment for the interaction between the pump light and the gain gas.

[0045] The tunable, narrow linewidth continuous pump light generated by the pump source 1 is collimated by the pump light collimating lens 2 into parallel light, and then transmitted to the pump light focusing lens 3 for focusing, so as to realize the mode matching of the pump laser and the core of the hollow core fiber 8. The pump laser is further transmitted through the dichroic mirror 4 and the output coupling mirror 6 in a low loss mode, and finally coupled into the core of the hollow core fiber 8. The output coupling mirror 6 has high transmittance to the pump light and partial transmittance to the laser wavelength band generated by the resonant cavity, so as to provide feedback for the resonant cavity, and at the same time, as a component of the input gas sealing cavity 7, the output coupling mirror 6 completes the sealing of the gain gas. The input gas sealing cavity 7 is used for sealing the input end of the hollow core fiber 8, and the gas filling and pumping device 13 is used for performing the vacuum pumping and gain gas filling operations on the hollow core fiber 8. The output coupling mirror 6, the input gas sealing cavity 7, the hollow core fiber 8, the saturable absorber mirror 10 and the output gas sealing cavity 11 constitute a resonant cavity structure. The laser 9 emitted from the output end of the hollow core fiber is transmitted in the output gas sealing cavity 11, and then incident on the saturable absorber mirror 10. As shown in Figure 3 the saturable absorber mirror 10 includes a saturable absorber 101, a mirror 102 and a substrate 103, and the saturable absorber 101 and the mirror 102 are sequentially grown on the substrate 103. The absorption coefficient of the saturable absorber to the incident laser light decreases with the increase of the intensity of the incident laser light. When the pump light output by the pump source begins to be injected into the core of the hollow core fiber 8, the initial laser intensity generated in the resonant cavity is small, and after the laser is incident on the saturable absorber mirror 10, the laser is strongly absorbed by the saturable absorber 101, and the resonant cavity loss is large, so that the laser amplification output cannot be realized. Under the continuous pumping of the pump light, the laser intensity generated in the resonant cavity gradually increases, and the absorption coefficient of the saturable absorber 101 decreases. At this time, the laser passes through the saturable absorber to the mirror 102 in a low loss mode, and further, after the laser is reflected by the mirror 102, the laser again passes through the saturable absorber 101 in a low loss mode. The reflected laser enters the hollow core fiber 8 and is transmitted to the output coupling mirror 6. Part of the laser passes through the output coupling mirror 6, is reflected by the dichroic mirror 4, and becomes the final output laser 5.

[0046] In an embodiment, based on the structure shown in Figure 2 a passive Q-modulated pulsed fiber gas laser is provided, which can realize simultaneous output of pulsed / continuous fiber gas laser and has more flexible working mode. As shown in Figure 2As shown, the passive Q-modulated pulsed fiber gas laser also comprises a pump source 1, a pump light coupling system, a dichroic mirror 4, an output coupling mirror 6, an input gas sealed cavity 7, a hollow core fiber 8, a gain gas, a saturable absorber mirror 10, an output gas sealed cavity 11, a window sheet 12, and a gas filling and pumping device 13. The pump wavelength of the pump source and the gain gas should satisfy: after the pump light enters the hollow core fiber, the gain gas absorbs the pump light energy to cause population inversion, and then generates output laser through energy level transition, and the output laser spectrum contains two wavelength components, i.e. first wavelength output laser and second wavelength output laser, the first wavelength is smaller than the second wavelength, by controlling the cutoff wavelength of the saturable absorber absorption bandwidth, pulsed fiber gas laser and continuous fiber gas laser are simultaneously output, when the saturable absorber absorption bandwidth is cut off to the first wavelength, the absorption of the second wavelength output laser at the second wavelength can be ignored, at this time, the first wavelength output laser realizes pulsed output by using the saturable absorber, and the saturable absorber always has high transmittance to the second wavelength output laser, so that the second wavelength output laser realizes continuous laser mode output.

[0047] In an embodiment, based on Figure 2 As shown in the structure, a passive Q-modulated pulsed fiber gas laser is provided, which can realize pulsed / continuous fiber gas laser simultaneous output, as shown in Figure 2 As shown, the passive Q-modulated pulsed fiber gas laser also comprises a pump source 1, a pump light coupling system, a dichroic mirror 4, an output coupling mirror 6, an input gas sealed cavity 7, a hollow core fiber 8, a gain gas, a saturable absorber mirror 10, an output gas sealed cavity 11, a window sheet 12, and a gas filling and pumping device 13. The pump wavelength of the pump source and the gain gas should satisfy: after the pump light enters the hollow core fiber, the gain gas absorbs the pump light energy to cause population inversion, and then generates output laser through energy level transition, and the output laser spectrum contains two wavelength components, i.e. first wavelength output laser and second wavelength output laser, the first wavelength is smaller than the second wavelength, by controlling the cutoff wavelength of the saturable absorber absorption bandwidth, pulsed fiber gas laser and continuous fiber gas laser are simultaneously output, when the saturable absorber absorption bandwidth is cut off to the first wavelength, the absorption of the second wavelength output laser at the second wavelength can be ignored, at this time, the first wavelength output laser realizes pulsed output by using the saturable absorber, and the saturable absorber always has high transmittance to the second wavelength output laser, so that the second wavelength output laser realizes continuous laser mode output. Figure 4 For the output spectrum diagram of the acetylene fiber gas laser, it can be seen that the output laser is in the 3 μm band and contains two different wavelength components. The absorption bandwidth of the saturable absorber 101 on the saturable absorber mirror 10 used in this embodiment can be adjusted to realize pulsed fiber gas laser output in different wavelength bands. And by controlling the cutoff wavelength of the saturable absorber 101 absorption bandwidth, pulsed / continuous fiber gas laser output can be realized. In combination with Figure 4When the absorption bandwidth of the saturable absorber 101 is cut off at 3150nm, i.e. the absorption at the wavelength of 3182.3nm can be ignored, at this time the laser with the wavelength of 3106.29nm can be pulsed by the saturable absorber 10, and the wavelength of 3182.3nm has high transmittance to the saturable absorber 10 all the time, and works in the continuous laser mode.

[0048] The details of the present application are known.

[0049] The technical features of the above embodiments can be combined arbitrarily, and for the sake of brevity, all possible combinations of the technical features in the above embodiments are not described, however, as long as the combinations of the technical features do not contradict, they should be considered as the scope of the present disclosure.

[0050] The above embodiments only express several embodiments of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the application. It should be pointed out that for ordinary skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

[0051] The above only describes the preferred embodiments of the present application, and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A passive Q-modulated pulsed fiber gas laser, characterized in that, The system includes a pump source, an output coupling mirror, an input gas sealed cavity, a hollow-core optical fiber, a gain gas, a saturable absorber mirror, and an output gas sealed cavity. The two ends of the hollow-core optical fiber are sealed by the input gas sealed cavity and the output gas sealed cavity, respectively, and the core of the hollow-core optical fiber is filled with gain gas. The output coupling mirror is disposed on one side wall of the input gas sealed cavity, and the saturable absorber mirror is disposed within the output gas sealed cavity. The output coupling mirror, the input gas sealed cavity, the hollow-core optical fiber, the saturable absorber mirror, and the output gas sealed cavity constitute a resonant cavity. A saturable absorber mirror is used as a passive Q-switching device. The saturable absorber mirror includes a saturable absorber, a reflector, and a substrate. The absorption coefficient of the absorber decreases as the incident light intensity increases. By adjusting the absorption bandwidth of the saturable absorber on the saturable absorber mirror, pulsed fiber gas laser output of different bands can be achieved. The saturable absorber and the reflector are grown sequentially on the substrate. When the laser intensity incident on the saturable absorber is less than a set threshold, the incident laser is absorbed by the saturable absorber and will not reach the reflector mirror. When the laser intensity incident on the saturable absorber is greater than or equal to the set threshold, the absorption of the incident laser by the saturable absorber is very small, and the laser will pass through the saturable absorber and be incident on the reflector mirror. After reflection by the reflector mirror, the reflected laser will pass through the saturable absorber mirror and return along the original path. After the pump light output from the pump source enters the hollow fiber, the gain gas absorbs the pump light energy and undergoes population inversion, thereby generating output laser through energy level transitions. The output laser spectrum contains two wavelength components: a first wavelength output laser and a second wavelength output laser. The first wavelength is shorter than the second wavelength. By controlling the cutoff wavelength of the absorption bandwidth of the saturable absorber, pulsed fiber gas laser and continuous fiber gas laser can be output simultaneously. When the absorption bandwidth of the saturable absorber is cut off to the first wavelength, the first wavelength output laser is pulsed using the saturable absorber. The saturable absorber always has high transmittance for the second wavelength output laser, so the second wavelength output laser achieves continuous laser mode output.

2. The passive Q-modulated pulsed fiber gas laser according to claim 1, characterized in that, It also includes a pump optical coupling system and a dichroic mirror, wherein the pump source, the pump optical coupling system, the dichroic mirror, and the output coupling mirror are arranged in sequence; The pump light coupling system is used to efficiently couple the pump light output from the pump source into the core of the hollow fiber; the dichroic mirror has high transmittance for the pump light and high reflectivity for the laser generated by the resonant cavity.

3. The passive Q-modulated pulsed fiber gas laser according to claim 2, characterized in that, The pump light coupling system includes a pump light collimating lens and a pump light focusing lens; the pump light collimating lens collimates the pump light emitted from the pump source into parallel light, and the pump light focusing lens efficiently couples the collimated pump light into the core of the hollow fiber.

4. The passive Q-modulated pulsed fiber gas laser according to claim 2, characterized in that, The output coupling mirror is a plane mirror with high transmittance for pump light and partial transmittance for laser light generated by the resonant cavity.

5. The passive Q-modulated pulsed fiber gas laser according to claim 3 or 4, characterized in that: When the pump light output from the pump source begins to be injected into the core of the hollow fiber, the laser intensity generated in the resonant cavity is less than the set threshold in the initial state. After the laser is incident on the saturable absorber, it is strongly absorbed by the saturable absorber, and the resonant cavity loss is very large, making it impossible to achieve laser amplification output. Under continuous pumping by the pump light, the intensity of the laser generated in the resonant cavity gradually increases, and the absorption coefficient of the saturable absorber decreases. At this time, the laser passes through the saturable absorber with low loss and reaches the reflector. Furthermore, after being reflected by the reflector, the laser will also pass through the saturable absorber again with low loss. The reflected laser enters the hollow fiber and is transmitted to the output coupling mirror. After passing through the output coupling mirror, part of the laser is reflected by the dichroic mirror to become the final output laser.

6. The passive Q-modulated pulsed fiber gas laser according to claim 1, 2, 3, or 4, characterized in that: It also includes a gas filling and evacuation device, used to evacuate the hollow fiber and fill it with gain gas through the input gas sealing cavity and the output gas sealing cavity.

7. The passive Q-modulated pulsed fiber gas laser according to claim 6, characterized in that: The pump source is a tunable, narrow-linewidth continuous laser source, and the output wavelength corresponds to the absorption peak of the gain gas used.

Images