Passive Q modulation pulse optical fiber gas laser

Abstract

The invention provides a passive Q modulation pulse optical fiber gas laser aiming at the current situation that in a traditional optical fiber gas laser, pulse output needs to be obtained through a high-cost pulse pumping source or through an active Q modulation technology. Comprising a pumping source, an output coupling mirror, an input gas sealing cavity, a hollow-core optical fiber, gain gas, a saturable absorption mirror and an output gas sealing cavity, passive Q-switching is realized by combining an optical fiber gas laser and the saturable absorption mirror, pulse generation is automatically realized by utilizing the nonlinear optical characteristic of the saturable absorption mirror, the structure is simple, external driving is not needed, and the power consumption is low. The method is suitable for miniaturization and integration.

Description

Technical Field

[0001] The present invention mainly relates to the field of fiber laser technology, and in particular to a passive Q-switched pulsed fiber gas laser. Background Art

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

[0003] Regarding pulsed fiber lasers, they have the characteristic of high peak power and have specific application scenarios in fields such as precision cutting, laser surgery, tissue cutting, and optoelectronic countermeasure. However, at present, the means of realizing pulsed output for fiber gas lasers are very limited. One method is to rely on a pulsed output laser as the pump source to achieve pulsed output. This technical means completely depends on the performance of the pump source, and it is impossible to flexibly adjust the output repetition frequency and pulse width. Moreover, the peak power output by the pulsed fiber gas laser is limited, lower than the peak power 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 the active Q-switching technology, which realizes a pulsed fiber gas laser by using active Q-switching devices such as acousto-optic crystals, electro-optic crystals, and choppers. However, this technical method depends on complex external modulators, the system volume is large, realizing pulsed output requires the aid of active devices, so the cost is high, the system is mostly spatial optical paths, the active devices increase the system complexity, the device is cumbersome, and it is easily affected by the environment. Summary of the Invention

[0004] Aiming at the technical problems existing in the prior art, the present invention proposes a passive Q-switched pulsed fiber gas laser. The passive Q-switched pulsed fiber gas laser proposed by the present invention utilizes the nonlinear optical characteristics of the saturable absorber mirror to automatically achieve pulsed output, with a simple structure, no external drive, and is suitable for miniaturization and integration.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows: A passive Q - switched pulsed fiber gas laser, comprising a pump source, an output coupling mirror, an input gas sealing cavity, a hollow fiber, gain gas, a saturable absorber mirror, and an output gas sealing cavity; both ends of the hollow fiber are sealed by the input gas sealing cavity and the output gas sealing cavity respectively, and the core of the hollow fiber is filled with gain gas; the output coupling mirror, the input gas sealing cavity, the hollow fiber, the saturable absorber mirror, and the output gas sealing cavity form a resonant cavity, and a saturable absorber mirror is used as a passive Q - switching device. The saturable absorber mirror includes a saturable absorber, a mirror, and a substrate. The absorption coefficient of the saturable absorber decreases with the increase of the incident light intensity. By adjusting the absorption bandwidth of the saturable absorber on the saturable absorber mirror, pulsed fiber gas laser output in different bands can be realized.

[0006] Further, the saturable absorber and the mirror are sequentially grown on the substrate. When the laser intensity incident on the saturable absorber is less than the set threshold, the incident laser is absorbed by the saturable absorber and does not reach the mirror; when the laser intensity incident on the saturable absorber is greater than or equal to the set threshold, the absorption of the saturable absorber for the incident laser is very small, the laser will pass through the saturable absorber and be incident on the mirror, and after being reflected by the mirror, the reflected laser will pass through the saturable absorber and return along the original path.

[0007] Preferably, after the pump light enters the hollow fiber, the gain gas absorbs the pump light energy to generate population inversion, and then output laser is generated through energy level transition. The laser spectrum of the output laser contains two wavelength components, namely the first - wavelength output laser and the second - wavelength output laser, where the first wavelength is less than the second wavelength. By controlling the cut - off 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 at 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 uses the saturable absorber to achieve pulsed output, and the saturable absorber always has a high transmittance for the second - wavelength output laser, so the second - wavelength output laser realizes continuous laser mode output. Thus, the present invention realizes the simultaneous output of pulsed / continuous fiber gas laser.

[0008] Further, the present invention also includes a pump light coupling system and a dichroic mirror. The pump source, the pump light coupling system, the dichroic mirror, and the output coupling mirror are sequentially arranged; The pump light coupling system is used to efficiently couple the pump light output by the pump source into the core of the hollow fiber; the dichroic mirror has a high transmittance for the pump light and a high reflectivity for the laser generated in the resonant cavity.

[0009] Further, 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 by the pump source into parallel light, and the pump light focusing lens efficiently couples and injects the collimated pump light into the core of the hollow fiber.

[0010] Further, the output coupling mirror is a plane mirror, which has a high transmittance to the pump light and a partial transmittance to the laser generated by the resonant cavity.

[0011] Further, the output coupling mirror is arranged on one side wall of the input gas sealed cavity, and the saturable absorber mirror is arranged in the output gas sealed cavity.

[0012] Further, when the pump light output by the pump source starts to be injected into the core of the hollow fiber, in the initial state, the laser intensity generated in the resonant cavity is small. After the laser is incident on the saturable absorber mirror, it is strongly absorbed by the saturable absorber, and the loss of the resonant cavity is very large and 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 decreases. At this time, the laser passes through the saturable absorber to the mirror with low loss. Further, after the laser is reflected by the mirror, it 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. Part of the laser passes through the output coupling mirror and then is reflected by the dichroic mirror to become the final output laser.

[0013] Further, the present invention further includes an inflation and evacuation device for evacuating the hollow fiber and filling it with gain gas through the input gas sealed cavity and the output gas sealed cavity.

[0014] Further, the hollow fiber has low transmission loss for both the pump light laser band and the laser band generated by the resonant cavity.

[0015] Further, 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.

[0016] Aiming at the problems existing in the prior art fiber gas lasers, such as completely depending on the performance of the pump source, being unable to flexibly adjust the output repetition frequency and pulse width, the peak power of the pulse output finally obtained by the fiber gas laser cannot exceed the peak power of the pump source, the problem of the complexity and tediousness of the system caused by the external driving device in the actively Q-switched pulsed fiber gas laser, and the problem that the fiber gas laser cannot realize the simultaneous output of pulsed / continuous fiber gas laser, the present invention provides a passive Q-switched pulsed fiber gas laser. Compared with the prior art, the technical effects of the present invention are as follows: The Q-Switching technology is a method to generate high peak power pulses by periodically changing the Q value (quality factor) of the laser resonator. The principle is as follows: during the pumping stage, laser oscillation is actively suppressed (low Q value, and energy is stored in the gain medium). After the energy accumulates to the saturation threshold, the high Q value is suddenly restored, enabling the stored energy to be released in an extremely short time, forming a giant pulse with a nanosecond-level and megawatt-level peak power. In traditional fiber gas lasers, obtaining pulsed output requires relying on a high-cost pulsed pump source or achieving it through active Q-switching technology. Fiber gas lasers have the characteristic of flexible output wavelengths. The present invention combines a fiber gas laser and a saturable absorber mirror to achieve passive Q-switching, and proposes a technology for obtaining pulsed lasers applicable in multiple bands.

[0017] The present invention adopts an oscillator structure and uses a saturable absorber mirror as a passive Q-switching device. By adjusting the Q value of the resonator, pulsed output is obtained. The saturable absorber mirror realizes passive Q-switching, which belongs to a kind of passive Q-switching technology. It can also be replaced by other passive devices to achieve passive Q-switching, such as organic dyes.

[0018] The passive Q-switching technology of the present invention realizes pulsed output without relying on external modulation devices. The pump source can use a continuous-wave output laser light source, with less dependence on the performance of the pump source, reducing the requirements for the pump, reducing the system complexity, and decreasing the cost.

[0019] The passive Q-switching technology proposed by the present invention can flexibly adjust the repetition frequency and pulse width of pulsed lasers by changing the magnitude of the pump power or the parameters of the passive Q-switching device.

[0020] The present invention realizes the simultaneous output of pulsed / continuous fiber gas lasers by designing the absorption bandwidth of the saturable absorber, and the working mode is more flexible.

[0021] The present invention can obtain pulsed output without a pulsed pump source and an additional driving device, reducing the system cost and lowering the device complexity. The Q-switching technology adopted by the present invention is not affected by the output wavelength and can be used in multiple bands, having a wider applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following-described drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0023] Figure 1 It is a schematic structural diagram of a passive Q-modulated pulsed fiber gas laser in an embodiment; Figure 2 Schematic diagram of the structure of a passive Q-switched pulsed fiber gas laser in an embodiment; Figure 3 Schematic diagram of the composition of the saturable absorber mirror; Figure 4 Output spectrum diagram of the acetylene fiber gas laser; Reference numerals in the figure: 1 is a pump source; 2 is a pump collimating lens; 3 is a pump focusing lens; 4 is a dichroic mirror; 5 is the output laser; 6 is an output coupling mirror; 7 is an input gas sealing cavity; 8 is a hollow fiber; 9 is the laser emitted from the output end of the hollow fiber; 10 is a saturable absorber mirror; 11 is an output gas sealing cavity; 12 is a window plate; 13 is an inflation and evacuation device; 101 is a saturable absorber; 102 is a mirror; 103 is a substrate. Specific implementation mode

[0024] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0025] Refer to Figure 1 , which is a schematic diagram of the structure of a passive Q-switched pulsed fiber gas laser in an embodiment, including a pump source, an output coupling mirror 6, an input gas sealing cavity 7, a hollow fiber 8, a gain gas, a saturable absorber mirror 10, and an output gas sealing cavity 11. The input gas sealing cavity 7 and the output gas sealing cavity 11 are connected with an inflation and evacuation device 13, and the inflation and evacuation device 13 is used to perform vacuum pumping and filling of the gain gas on the hollow fiber 8 through the input gas sealing cavity 7 and the output gas sealing cavity 11. The inflation and evacuation device 13 includes a vacuum pump, a gas cylinder, a barometer, etc., and can perform operations of vacuum pumping and inflation on the hollow fiber 8, and can also adjust and detect the gas pressure of the gain gas in the hollow fiber. The input gas sealing cavity 7 and the output gas sealing cavity 11 are located at both ends of the hollow fiber 8 and are used to seal gas molecules in the hollow fiber 8; the hollow fiber 8 can effectively confine the pump light in the core of the hollow fiber 8 and provide an effective interaction distance between the pump light and the gain gas; the inflation and evacuation device 13 evacuates the hollow fiber 8 through the input gas sealing cavity 7 and the output gas sealing cavity 11 and then fills it with the gain gas at an appropriate gas pressure.

[0026] The pump source is a tunable, narrow-linewidth continuous laser light source, and the output wavelength corresponds to the absorption peak of the used gain gas.

[0027] Both ends of the hollow-core optical fiber 8 are sealed by an input gas sealing cavity 7 and an output gas sealing cavity 11 respectively, and the core of the hollow-core optical fiber 8 is filled with a gain gas; the output coupling mirror 6, the input gas sealing cavity 7, the hollow-core optical fiber 8, the saturable absorber mirror 10 and the output gas sealing cavity 11 form a resonant cavity, and the saturable absorber mirror 10 is used as a Q-switching device to generate pulsed laser. The hollow-core optical fiber 8 has low transmission loss for both the pump laser band and the laser band generated by the resonant cavity. The type of the gain gas is not limited, such as C2H2, CO, HBr, etc.

[0028] The output coupling mirror 6 is arranged on a side wall of the input gas sealing cavity 7. The output coupling mirror 6 is a plane mirror, which has a high transmittance for the pump light and a partial transmittance for the laser generated by the resonant cavity. The saturable absorber mirror 10 is arranged in the output gas sealing cavity 11, and the output gas sealing cavity 11 is sealed by a window plate 12. The window plate 12 is a plane lens, and the window plate 12 is a component of the output gas sealing cavity 11 and is used to fixedly arrange the saturable absorber mirror 10 at the same time.

[0029] The saturable absorber mirror 10 is a passive device, including a saturable absorber and a mirror. The absorption coefficient of the saturable absorber for light decreases with the increase of the incident light intensity, and its absorption bandwidth can be adjusted. The mirror has a high reflectivity for the laser band (including the pump laser band and the laser band generated by the resonant cavity). By adjusting the absorption bandwidth of the saturable absorber on the saturable absorber mirror, pulsed fiber gas laser output in different bands can be realized. By controlling the cut-off wavelength of the absorption bandwidth of the saturable absorber, pulsed fiber gas laser and continuous fiber gas laser can be output simultaneously.

[0030] The saturable absorber mirror 10 is as Figure 3 shown, including a saturable absorber 101, a mirror 102 and a substrate 103. The saturable absorber 101 and the mirror 102 are sequentially grown on the substrate 103. The saturable absorber 101 is an optical nonlinear material, and its absorption coefficient will decrease with the increase of the incident light intensity and finally reach a "saturated" state (that is, the absorption ability is significantly weakened or hardly absorbs). 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 will not reach the mirror 102; when the laser intensity incident on the saturable absorber 101 is strong enough, the absorption of the saturable absorber 101 for the incident laser is very small, and the laser will pass through the saturable absorber 101 and be incident on the mirror 102. After being reflected by the mirror 102, the reflected laser will pass through the saturable absorber 101 and return along the original path.

[0031] When the pump light output by the pump source starts to be injected into the core of the hollow-core fiber 8, the laser intensity generated in the resonant cavity is small in the initial state. After the laser is incident on the saturable absorber mirror 10, it is strongly absorbed by the saturable absorber 101, and the loss of the resonant cavity is so large that laser amplification output cannot be achieved. 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 with low loss and reaches the mirror 102. 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 fiber 8 and is transmitted to the output coupling mirror 6, and part of the laser is output after passing through the output coupling mirror 6.

[0032] Refer to Figure 2 , which is a schematic structural diagram of a passive Q-switched pulsed fiber gas laser in an embodiment, including a pump source 1, a pump light coupling system, a dichroic mirror 4, an output coupling mirror 6, an input gas sealing cavity 7, a hollow-core fiber 8, a gain gas, a saturable absorber mirror 10, an output gas sealing cavity 11, a window plate 12, and an air filling and pumping device 13. The pump light coupling system is used to efficiently couple the pump light output by the pump source into the core of the hollow-core fiber. The dichroic mirror 4 is a dichroic mirror, which has a high transmittance to the pump light and a high reflectivity to the laser generated in the resonant cavity, so as to realize the separation of the pump light and the final output laser 5. The pump light coupling system includes a pump light collimating lens 2 and a pump light focusing lens 3; the pump light collimating lens 2 collimates the pump light emitted by the pump source 1 into parallel light, and the pump light focusing lens 3 efficiently couples the collimated pump light into the core of the hollow-core fiber 8. 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 arrangement and functions of the output coupling mirror 6, the input gas sealing cavity 7, the hollow-core fiber 8, the gain gas, the saturable absorber mirror 10, the output gas sealing cavity 11, the window plate 12, and the air filling and pumping device 13 are exactly the same as those in the previous embodiment and will not be elaborated here.

[0033] The pump source 1 outputs a wavelength corresponding to the absorption peak of the gain gas molecules. The pump light collimating lens 2 changes 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 a high transmittance to the pump light and a high reflectivity to the laser generated in the resonant cavity. The output coupling mirror 6 has a high transmittance to the pump laser and a partial transmittance to the laser 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.

[0034] The tunable and narrow linewidth continuous pump light generated by the pump source 1 is collimated by the pump light collimating lens 2 to become parallel light, and further the parallel light is transmitted to the pump light focusing lens 3 for focusing to achieve mode matching between the pump laser and the core of the hollow fiber 8. Further, the pump laser passes through the dichroic mirror 4 and the output coupling mirror 6 with low loss, and finally is coupled into the core of the hollow fiber 8. The output coupling mirror 6 has a high transmittance to the pump light and a partial transmittance to the laser band generated by the resonant cavity, provides feedback for the resonant cavity, and at the same time completes the sealing of the gain gas as a part of the input gas sealing cavity 7. The input gas sealing cavity 7 is used for sealing the pump incident end of the hollow fiber 8, and the gas charging and pumping device 13 is used for performing vacuum pumping and gain gas filling operations on the hollow fiber 8. The output coupling mirror 6, the input gas sealing cavity 7, the hollow fiber 8, the saturable absorber mirror 10 and the output gas sealing cavity 11 form a resonant cavity structure. The laser 9 emitted from the output end of the hollow fiber is transmitted in the output gas sealing cavity 11 and further incident on the saturable absorber mirror 10. The saturable absorber mirror 10 is as Figure 3 shown, and includes a saturable absorber 101, a mirror 102 and a substrate 103. The saturable absorber 101 and the mirror 102 are sequentially grown on the substrate 103, and the absorption coefficient of the saturable absorber for the incident laser decreases as the intensity of the incident laser increases. When the pump light output by the pump source starts to be injected into the core of the hollow fiber 8, in the initial state, the laser intensity generated in the resonant cavity is small. After the laser is incident on the saturable absorber mirror 10, it is strongly absorbed by the saturable absorber 101, and the loss of the resonant cavity is so large that laser amplification output cannot be achieved. 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 reach 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 fiber 8 and is transmitted to the output coupling mirror 6. Part of the laser passes through the output coupling mirror 6 and then is reflected by the dichroic mirror 4 to become the final output laser 5.

[0035] In one embodiment, based on the Figure 2 structure shown, a passive Q-switched pulsed fiber gas laser is provided, which can realize the simultaneous output of pulsed / continuous fiber gas lasers, and the working mode is more flexible. As Figure 2As shown, the passive Q-switched pulsed fiber gas laser also includes 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 fiber 8, a gain gas, a saturable absorber mirror 10, an output gas sealed cavity 11, a window plate 12, and an inflation and evacuation device 13. The pump wavelength of the pump source and the gain gas should satisfy the following: after the pump light enters the hollow fiber, the gain gas absorbs the energy of the pump light and undergoes population inversion, and then generates output laser through energy level transition. Moreover, the laser spectrum of the output laser contains two wavelength components, namely the first wavelength output laser and the second wavelength output laser, with the first wavelength being less than the second wavelength. By controlling the cut-off wavelength of the absorption bandwidth of the saturable absorber, the pulsed fiber gas laser and the continuous fiber gas laser can be output simultaneously. When the absorption bandwidth of the saturable absorber is cut off at 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 uses the saturable absorber to achieve pulsed output, and the saturable absorber always has a high transmittance for the second wavelength output laser, so the second wavelength output laser achieves continuous laser mode output.

[0036] In a specific embodiment, based on Figure 2 the structure shown, a passive Q-switched pulsed fiber gas laser is provided, which can achieve the simultaneous output of pulsed / continuous fiber gas lasers. As Figure 2 shown, the passive Q-switched pulsed fiber gas laser also includes 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 fiber 8, a gain gas, a saturable absorber mirror 10, an output gas sealed cavity 11, a window plate 12, and an inflation and evacuation device 13. Among them, the pump source 1 is used to generate pump light in the 1.5 μm band, and the gain gas filled in the core of the hollow fiber 8 is acetylene. After the pump light in the 1.5 μm band enters the hollow fiber 8, the acetylene gas absorbs the energy of the pump light and undergoes population inversion, and then generates laser output in the 3 μm band through energy level transition. Moreover, the laser spectrum of the output laser contains two wavelength components. Referring to Figure 4 , which is 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 at the same time. The absorption bandwidth of the saturable absorber 101 on the saturable absorber mirror 10 used in this embodiment can be adjusted to achieve pulsed fiber gas laser output in different bands. And by controlling the cut-off wavelength of the absorption bandwidth of the saturable absorber 101, the pulsed / continuous fiber gas laser output can be achieved. Combining Figure 4, when the absorption bandwidth of the saturable absorber 101 is cut off at 3150 nm, that is, the absorption at a wavelength of 3182.3 nm can be ignored. At this time, the laser with a wavelength of 3106.29 nm can use the saturable absorber 10 to achieve pulsed output, while the wavelength of 3182.3 nm always has a high transmittance for the saturable absorber 10 and operates in the continuous laser mode.

[0037] Matters not covered by this invention are well-known techniques.

[0038] The technical features of the above embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0039] The above-described embodiments merely represent several implementation manners of this application. The description is relatively specific and detailed, but it should not be construed as a limitation to the scope of the invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of this application, several modifications and improvements can be made, and these all belong to the protection scope of this application. Therefore, the protection scope of this application should be subject to the appended claims.

[0040] The above is only the preferred embodiment of the present invention and is not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. Passive Q-modulated pulsed fiber gas laser, characterized in that: The invention comprises a pump source, an output coupling mirror, an input gas sealed cavity, a hollow-core optical fiber, a gain gas, a saturable absorption 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 a gain gas; the output coupling mirror, the input gas sealed cavity, the hollow-core optical fiber, the saturable absorption mirror and the output gas sealed cavity constitute a resonant cavity, and the saturable absorption mirror is used as a passive Q-switching device, and the saturable absorption mirror comprises a saturable absorber, a reflector and a substrate, and the absorption coefficient of the saturable absorber decreases with the increase of the incident light intensity, and the absorption bandwidth of the saturable absorber on the saturable absorption mirror is adjusted to realize the output of pulsed optical fiber gas lasers of different wavelength bands.

2. The passive Q-modulated pulse fiber gas laser according to claim 1, characterized in that: The saturable absorber and the reflector are grown on the substrate in sequence. When the intensity of the laser incident on the saturable absorber is less than a set threshold, the incident laser is absorbed by the saturable absorber and does not reach the reflector. When the intensity of the laser incident on the saturable absorber is greater than or equal to the set threshold, the saturable absorber absorbs very little of the incident laser, and the laser passes through the saturable absorber and is incident on the reflector. After being reflected by the reflector, the reflected laser passes through the saturable absorber and returns along the original path.

3. The passive Q-modulated pulse fiber gas laser according to claim 2, characterized in that: After the pump light output by the pump source enters the hollow-core optical fiber, the gain gas absorbs the energy of the pump light to cause a population inversion, and then generates an output laser through energy level transition, and the laser spectrum of the output laser contains two wavelength components, namely, a first wavelength output laser and a second wavelength output laser, the first wavelength is smaller than the second wavelength, and by controlling the cutoff wavelength of the absorption bandwidth of the saturable absorber, the pulse fiber gas laser and the continuous fiber gas laser are output simultaneously, and when the absorption bandwidth of the saturable absorber is cutoff to the first wavelength, the first wavelength output laser uses the saturable absorber to realize pulse output, and the saturable absorber always has a high transmittance to the second wavelength output laser, and the second wavelength output laser realizes continuous laser mode output.

4. The passive Q-modulated pulse fiber gas laser according to claim 1, 2 or 3, characterized in that: It also includes a pump light coupling system and a dichroic mirror, wherein the pump source, the pump light 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 by the pump source into the core of the hollow-core optical fiber; the dichroic mirror has high transmittance to the pump light and high reflectivity to the laser generated by the resonant cavity.

5. The passive Q-modulated pulse fiber gas laser according to claim 4, characterized in that: 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 and injects the collimated pump light into the core of the hollow core optical fiber.

6. The passive Q-modulated pulse fiber gas laser according to claim 4, characterized in that: The output coupling mirror is a plane mirror, which has high transmittance to the pump light and partial transmittance to the laser light generated by the resonant cavity.

7. The passive Q-modulated pulse fiber gas laser according to claim 6, characterized in that: The output coupling mirror is arranged on a side wall of the input gas sealing cavity, and the saturable absorption mirror is arranged in the output gas sealing cavity.

8. The passive Q-modulated pulse fiber gas laser according to claim 5, 6 or 7, characterized in that: When the pump light output by the pump source begins to be injected into the core of the hollow-core optical 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 mirror, it is strongly absorbed by the saturable absorber. The resonant cavity loss is very large and the laser amplification output cannot be achieved. 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 with low loss to reach the reflector. Further, after the laser is reflected by the reflector, it will also pass through the saturable absorber again with low loss. The reflected laser enters the hollow-core optical 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.

9. The passive Q-modulated pulse fiber gas laser according to claim 1 or 2 or 3 or 5 or 6 or 7, characterized in that: It also includes a gas filling and exhausting device, which is used to evacuate the hollow core optical fiber and fill it with gain gas through the input gas sealing cavity and the output gas sealing cavity.

10. The passive Q-modulated pulse fiber gas laser according to claim 9, characterized in that: The pump source is a tunable, narrow-linewidth continuous laser light source, and the output wavelength corresponds to the absorption peak of the gain gas used.

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