CN105161968B - A kind of middle infrared double-wave length based on graphene is the same as repetition pulse optical fiber - Google Patents

Abstract

The invention discloses a kind of middle infrared double-wave length based on graphene with repetition pulse optical fiber, belong to pulse optical fiber field.A kind of middle infrared double-wave length based on graphene of the present invention is the same as repetition pulse optical fiber, speculum including being covered with graphene film layer, the speculum same level position is equipped with dichroic mirror one, the dichroic mirror one tilts 45 ° of arrangements relative to horizontal direction, relatively parallel dichroic mirror two is equipped with directly over the dichroic mirror one, the top of dichroic mirror two is double-wavelength pulse output terminal；Planoconvex lens four is equipped between the dichroic mirror one and speculum, light beam can be focused to speculum by the planoconvex lens four；The dichroic mirror one is in 3 μm of optical cavities, and the dichroic mirror two is in 2 μm of optical cavities, and two dichroic mirror has direction guiding effect at the same time to 2 μm and 3 μm of light.The present invention is ingenious in design, and infrared double-wave length for conventional method, has simple in structure, small volume, low, easy to operate, the advantage being easily integrated is lost with repetition high-power laser pulse in can obtaining.

Description

A graphene-based mid-infrared dual-wavelength co-repetition frequency pulsed fiber laser

technical field

The invention relates to a pulse fiber laser, in particular to a graphene-based mid-infrared dual-wavelength pulse fiber laser with the same repetition frequency.

Background technique

Fiber lasers have the advantages of high conversion efficiency, small size, excellent output beam quality, low laser threshold, easy integration, and good heat dissipation. Dual-wavelength fiber lasers are defined according to the number of output laser wavelength channels. It is used as the initial light source in the research of differential interference ranging, optical sensing, microwave radio frequency signal and high repetition rate ultrashort pulse generation. 2-5μm mid-infrared pulsed laser has broad application prospects in national defense, military, medical treatment, communication, etc. , For example, water molecules have strong absorption peaks in the 2μm and 3μm bands, which can be used in a new generation of laser surgery to make blood coagulate quickly, with small surgical wounds and good hemostasis.

At present, the mid-infrared pulsed fiber laser of the existing technology is mainly focused on realizing single-wavelength pulses, which cannot meet actual needs, and the traditional method is difficult to realize mid-infrared dual-wavelength laser pulses. In the prior art, mid-infrared dual-wavelength pulse output is realized through active Q-switching and active Q-switching guided gain modulation. The structure is too complicated, which makes fiber lasers lose their inherent advantages of compactness, flexibility, and small size.

Contents of the invention

The purpose of the present invention is to: aim at the above-mentioned problems, to provide a stable same-repetition-frequency dual-wavelength Q-switched pulse output of 2 μm and 3 μm by passive Q-switching using graphene’s saturable absorption characteristics, which has a simple structure and a small volume. Low loss, easy to operate, easy to integrate mid-infrared dual-wavelength co-repetition frequency pulsed fiber laser.

The technical scheme that the present invention adopts is as follows:

A method for emitting mid-infrared dual-wavelength pulses with the same repetition frequency of the present invention comprises the following steps:

Step 1: Turn on the pump source 2. The 1150nm light emitted by the pump source 2 is focused by the plano-convex mirror 1 onto the coating layer of the input end of the holmium-spectrum co-doped ZBLAN fiber, and 3 μm light is generated from the holmium-spectrum co-doped ZBLAN fiber. Output at the output end, the 3μm light passes through the plano-convex mirror three collimation and propagates to the dichromatic mirror 1, the 3μm light passes through the dichroic mirror 1, and transmits to the plano-convex mirror 4, and propagates through the plano-convex mirror 4 to the graphene-coated On the reflector of the thin film layer; 3μm light is reflected by the reflector and propagates back and forth in the second resonant cavity, and the number density of inversion particles of the upper energy level accumulates in large quantities; adjust the power of the pump source 2 to make the co-doped ZBLAN fiber from the holmium-spectrum The output 3μm optical power is low (it cannot saturate the graphene), and the graphene film is in a state of high loss (that is, in a low Q value);

Step 2: Keep the pump source 2 working, turn on the pump source 1, the 1550nm light emitted by the pump source 1 passes through the fiber Bragg grating and the thulium-holmium co-doped fiber to generate 2μm light, and the 2μm light is reflected by the second dichroic mirror After arriving at the dichroic mirror 1, it is reflected to the plano-convex mirror 4, and through the plano-convex mirror 4, it is focused and transmitted to the mirror covered with a graphene film layer; the 2 μm light is reflected by the mirror and propagates back and forth in the first resonant cavity, and the gain fiber The number of inversion particles is accumulated;

Step 3: Gradually increase the output power of the pump source 1, and the 2 μm amplified spontaneous emission light gradually increases; with the accumulation of the number of particle inversion particles in the holmium-spectrum co-doped ZBLAN fiber, the light intensity in the resonant cavity gradually increases. As the intensity of spontaneous emission increases, the saturation absorption coefficient of the graphene film decreases. Continue to increase the intensity of spontaneous emission, so that the absorption of the graphene film reaches saturation, the Q value in the resonant cavity increases sharply, and the accumulated number of inversion particles is It is rapidly consumed in a short period of time to generate laser oscillation and simultaneously output 2μm and 3μm pulses with high peak power from the output end;

Step 4: Keep the output power of pump source 1 and pump source 2. When the number of inversion particles is exhausted, the graphene film returns to a high loss state within the relaxation time. In this working state, the number of inversion particles in the two gain fibers is accumulated again, the 2μm light with higher power saturates the graphene again, and the output 2μm and 3μm pulses return to the high loss state again, and so on, so as to achieve the same repetition frequency 2µm and 3µm Q-switched pulses.

A graphene-based mid-infrared dual-wavelength pulsed fiber laser with the same repetition frequency of the present invention comprises a reflector coated with a graphene film layer, the reflector is provided with a dichroic mirror 1 on the same level, and the dichroic Mirror one is arranged at an inclination of 45° relative to the horizontal direction, and a relatively parallel dichroic mirror two is arranged directly above said dichroic mirror two, and a pulse output terminal is arranged above said dichroic mirror two; said dichroic mirror one and reflection A plano-convex mirror 4 is arranged between the mirrors, and the plano-convex mirror 4 can focus the light beam to the reflector; the first dichroic mirror has a 3 μm light generation route, and the second dichroic mirror has a 2 μm light generation route, so The 3 μm light generation route is parallel to the 2 μm light generation route.

Due to the adoption of the above structure, dichroic mirror 2 is located directly above dichroic mirror 1, and both dichroic mirror 2 and dichroic mirror 1 are arranged at an angle of 45° relative to the horizontal direction. After the light is reflected by dichroic mirror 2, it can be vertically The same light can be vertically transmitted to the second dichroic mirror after being reflected by the first dichroic mirror; the reflecting mirror and the first dichroic mirror are on the same horizontal position, and the plano-convex mirror four and the dichroic mirror The mirror one and the reflecting mirror are located on the same horizontal position, the convex surface of the plano-convex mirror four faces the reflecting mirror, and the light irradiated horizontally from the dichroic mirror one to the plano-convex mirror four can be focused onto the reflecting mirror; the reflecting mirror can direct the light Horizontal reflection to plano-convex mirror 4, plano-convex mirror 4 collimates and projects the light on dichroic mirror 1; dichroic mirror 2 is located on the 2 μm light generation route, dichroic mirror 1 is located on 3 μm light generation route, the light of two wavelengths The propagation paths are all horizontal or vertical. The first dichroic mirror is located in the 3 μm optical resonant cavity, and the second dichroic mirror is located in the 2 μm optical resonant cavity, and both of the two dichromatic mirrors have direction guiding functions for both 2 μm and 3 μm light. Multiple optical paths are formed between the first dichroic mirror, the second dichromatic mirror and the mirror, and the 2 μm light and the 3 μm light can propagate along a specific axis among the multiple optical paths. The 2 μm light can be combined with the 3 μm light after being reflected by the dichromatic mirror and then focused on the mirror covered with the graphene film layer. When the 2 μm light and the 3 μm light propagate along a specific axis, the number of inversion particles is continuously accumulated ; Graphene film has the characteristic of saturable absorption. As the intensity of spontaneous emission increases, the saturated absorption coefficient of graphene decreases, and the graphene film will suddenly be "bleached" and the absorption coefficient will drop to the minimum. At this time The Q value in the cavity increases sharply, and the laser oscillator outputs Q-switched pulses.

A graphene-based mid-infrared dual-wavelength pulse fiber laser with the same repetition frequency of the present invention, the 2 μm light generation route includes sequentially connected pump source one, optical Bragg grating and thulium-holmium co-doped optical fiber, the thulium - There is a plano-convex mirror 2 between the holmium co-doped fiber and the dichroic mirror 2, and the plano-convex mirror 2 can collimate the light output from the thulium-holmium co-doped fiber; first resonator.

Due to the above structure, the pump source 1 can continuously and stably output the light source. After the light source passes through the fiber Bragg grating, it passes through the thulium-holmium co-doped fiber to generate 2μm light. When the 2μm light passes through the plano-convex mirror 2, it propagates horizontally to the dichroic mirror. On the second, since the second dichroic mirror is placed at an angle of 45° relative to the horizontal direction, the light is reflected by the second dichroic mirror and propagates vertically to the first dichroic mirror, then reaches the mirror, and then returns to the fiber Bragg grating from the mirror, Thus, a first resonant cavity of 2 μm light is formed, and the 2 μm light propagates back and forth in the first resonant cavity, and the number density of inverted particles of the upper energy level is continuously accumulated. Through pump source 1, fiber Bragg grating and thulium-holmium co-doped fiber, 2μm light can be continuously and stably emitted, and a stable first resonant cavity can be formed by combining dichroic mirror 2, dichroic mirror 1 and reflector, with a simple structure , cleverly designed.

A graphene-based mid-infrared dual-wavelength pulse fiber laser with the same repetition frequency of the present invention, the 3 μm light generation route includes pump source two, plano-convex mirror one and holmium-praseodymium co-doped fluoride ZBLAN fiber, the plano-convex mirror One can focus the light emitted by the pump source two to the input end of the holmium-praseodymium co-doped fluoride ZBLAN fiber, and the input end face of the holmium-praseodymium co-doped fluoride ZBLAN fiber is provided with a coating layer; the holmium-praseodymium co-doped fluoride ZBLAN fiber is provided with a coating layer; A plano-convex mirror three is arranged between the co-doped fluoride ZBLAN fiber and the dichromatic mirror one, and the plano-convex mirror three can collimate the light output from the holmium-praseodymium co-doped fluoride ZBLAN fiber; A second resonant cavity is formed between them.

Due to the adoption of the above structure, the pump source 2 can continuously and stably output the light source. After the light source is focused on the coating layer at the input end of the holmium-praseodymium co-doped fluoride ZBLAN fiber, 3 μm light is generated, and the 3 μm light propagates horizontally to the dichromatic mirror 1. Pass through the dichroic mirror one to the reflector, and the reflector reflects the 3 μm light to the dichroic mirror one along the horizontal direction, because the dichroic mirror one is placed at an angle of 45° relative to the horizontal direction, a part of the 3 μm light is vertically reflected on the dichroic mirror one On mirror two, a part of 3μm light continues to pass through dichroic mirror one along the horizontal direction, and is projected to the coating layer, thereby forming a second resonant cavity of 3μm light, and the 3μm light propagates back and forth in the second resonant cavity, and the reflection of the upper energy level The number density of rotating particles is constantly accumulating. Through pump source 2, plano-convex mirror 1 and holmium-praseodymium co-doped fluoride ZBLAN fiber, 3μm light can be continuously and stably emitted, and a stable second resonance can be formed by combining dichroic mirror 2, dichroic mirror 1 and reflector Cavity, simple structure, ingenious design.

In the graphene-based mid-infrared dual-wavelength pulsed fiber laser with the same repetition rate of the present invention, the first pumping source is a 1550nm continuous laser diode, and the second pumping source is a 1150nm continuous laser diode.

A graphene-based mid-infrared dual-wavelength pulsed fiber laser with the same repetition frequency of the present invention, the fiber Bragg grating has a transmittance of >99% to 1550nm light, and a reflectivity of >99% to 2 μm light; The transmittance of 1150nm light is >99%, and the reflectance of 3μm light is >99%.

Due to the above structure, the 1550nm light emitted from the pump source 1 can pass through the fiber Bragg grating with a very high transmittance, and the 2μm light reflected from the mirror can be reflected again by the fiber Bragg grating with a high reflectivity back, thereby improving the working efficiency of the first resonant cavity and greatly reducing the loss; the 1150nm light emitted from the second pump source can pass through the coating layer with a very high transmittance, while the light reflected from the mirror The 3μm light can be reflected back again by the coating layer with high reflectivity, thereby improving the working efficiency of the second resonant cavity and greatly reducing the loss.

A graphene-based mid-infrared dual-wavelength pulsed fiber laser with the same repetition frequency according to the present invention, a pair of dichromatic mirrors have a light transmittance of >99% at 1150nm, and a reflectance of both 1550nm light and 2 μm light >99%, and 3 μm light. The light reflectance and transmittance are both 50%; the reflectance of the dichroic mirror 2 is >99% for 1550nm light, the reflectance for 2 μm light is 80%, the transmittance is 20%, and the transmittance for 3 μm light is >99% .

Due to the adoption of the above structure, when the 1550nm light and the 2μm light reach the first dichromatic mirror, they can be reflected to the second dichromatic mirror with high reflectivity; On the second dichroic mirror, 1150nm light can hardly pass through the second dichromatic mirror; when 1550nm light and 3μm light reach the second dichromatic mirror, they can be reflected to the first dichroic mirror with high reflectivity, and 2μm light reaches the dichromatic mirror At the second time, 80% of the 2μm light is reflected, and 20% of the 2μm light is transmitted through the dichroic mirror 2, forming a stable optical path accurately.

A graphene-based mid-infrared dual-wavelength pulsed fiber laser with the same repetition frequency of the present invention, the input end of the thulium-holmium co-doped fiber is set as a straight section, and the output end of the thulium-holmium co-doped fiber is set as 8 ° oblique section.

Due to the adoption of the above structure, the output power of 2 μm light is increased and the loss is reduced.

In summary, owing to adopting above-mentioned technical scheme, the beneficial effect of the present invention is:

1. A graphene-based mid-infrared dual-wavelength co-repetition frequency pulsed fiber laser of the present invention has an ingenious design, and the components are closely matched to each other, compact and flexible, small in size, and easy to integrate.

2. A graphene-based mid-infrared dual-wavelength co-repetition frequency pulsed fiber laser of the present invention has low loss, can form a stable optical path accurately and efficiently, has high work efficiency, and is easy to operate.

Description of drawings

Fig. 1 is a structural schematic diagram of a graphene-based mid-infrared dual-wavelength pulsed fiber laser with the same repetition rate;

Fig. 2 is a graph showing the relationship between the signal intensity of two pulses and the absorption coefficient of graphene.

Marks in the figure: 1 is pump source 1, 2 is fiber Bragg grating, 3 is thulium-holmium co-doped fiber, 4 is plano-convex mirror 2, 5 is pump source 2, 6 is plano-convex mirror 1, 7 is coating 8 is the holmium-praseodymium co-doped fluoride ZBLAN fiber, 9 is the third plano-convex mirror, 10 is the first dichroic mirror, 11 is the fourth plano-convex mirror, 12 is the graphene film layer, 13 is the mirror, and 14 is the second Color mirror two, 15 is the output end.

Detailed ways

Below in conjunction with accompanying drawing, the present invention is described in detail.

In order to make the object, technical solution and advantages of the invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

Example 1

As shown in Figure 1, a graphene-based mid-infrared dual-wavelength pulsed fiber laser with the same repetition frequency includes a reflector 13 covered with a graphene film layer 12. From the perspective of a top view: reflector 13 is provided with Dichroic mirror 1 10, dichroic mirror 1 10 is arranged with an inclination of 45° relative to the horizontal direction, dichroic mirror 1 10 is provided with a relatively parallel dichroic mirror 2 14, and dichroic mirror 2 14 is provided with a pulse output terminal 15 ; A plano-convex mirror 11 is arranged between the dichroic mirror 10 and the reflecting mirror 1), and the plano-convex mirror 4 11 can focus the light beam to the reflecting mirror 13; Two 14 companies have 2 μm light generation routes, 3 μm light generation routes are parallel to 2 μm light generation routes. The dichroic mirror two 14 is positioned at the top of the dichroic mirror one 10, and the center point of the dichroic mirror two 14 and the center point of the dichroic mirror one 10 are located on the same vertical straight line, and the dichroic mirror two 14 and the dichroic mirror two Mirror one 10 is all arranged with an inclination of 45° with respect to the horizontal direction. After light is reflected by dichroic mirror two 14, it is vertically irradiated on dichroic mirror one 10; On mirror two 14; reflecting mirror 13 is on the same horizontal position as dichroic mirror one 10, and plano-convex mirror four 11 is on the same horizontal position as dichroic mirror one 10 and reflecting mirror 13, and the convex surface of plano-convex mirror four 11 faces reflection Mirror 13 focuses the light that is horizontally irradiated onto the plano-convex mirror 4 11 from the dichromatic mirror 10 onto the reflector 13; The collimated projection is on the first dichroic mirror 10; the second dichroic mirror 14 is located on the 2 μm light generating route, and the dichroic mirror 1 10 is located on the 3 μm light generating route, ensuring that the light propagation route remains horizontal or vertical. Multiple optical paths are formed between the first dichroic mirror 10 , the second dichromatic mirror 14 and the reflective mirror 13 , and the 2 μm light and the 3 μm light propagate along a specific axis among the multiple optical paths. The 2 μm light is reflected by the dichromatic mirror 2 14 and merged with the 3 μm light, and then focused to the reflector 13 covered with the graphene film layer 12. When the 2 μm light and the 3 μm light propagate along a specific axis, the number of reversed particles is constant The accumulation of graphene film has the characteristics of saturable absorption. As the intensity of spontaneous emission increases, the saturated absorption coefficient of graphene decreases, and the graphene film will suddenly be "bleached" and the absorption coefficient will drop to the minimum. At this time At this time, the Q value in the cavity increases sharply, and the laser oscillation output Q-switched pulse is generated.

The 2 μm light generation route includes a sequentially connected pump source 1, fiber Bragg grating 2 and thulium-holmium co-doped fiber 3, and a plano-convex mirror 2 4 is arranged between the thulium-holmium co-doped fiber 3 and the dichroic mirror 2 14 , the plano-convex mirror 2 4 can collimate the light output by the thulium-holmium co-doped optical fiber 3; the first resonant cavity is formed between the fiber Bragg grating 2 and the mirror 13; the input end of the thulium-holmium co-doped optical fiber 3 is set as straight As for the cutting plane, the output end of the thulium-holmium co-doped optical fiber 3 is set as an oblique cutting plane of 8°. The pumping source 1 is a 1550nm continuous laser diode. The pumping source 1 continuously and stably outputs the light source. After the light passes through the fiber Bragg grating 2, it passes through the thulium-holmium co-doped fiber 3 to generate 2 μm light, and the 2 μm light passes through the plano-convex mirror 2 4 , the horizontal transmission to the dichroic mirror two 14, because the dichroic mirror two 14 is placed with an inclination of 45° relative to the horizontal direction, the light propagates vertically to the dichroic mirror one 10 after being reflected by the dichroic mirror two 14, and then reaches the reflection The mirror 13 returns to the fiber Bragg grating 2 from the mirror 13 to form the first resonant cavity of 2 μm light. The 2 μm light propagates back and forth in the first resonant cavity, and the number density of inverted particles of the upper energy level is continuously accumulated. Continuously and stably emit 2 μm light through pump source one 1, fiber Bragg grating 2 and thulium-holmium co-doped fiber 3, and combine dichroic mirror two 14, dichroic mirror one 10 and mirror 13 to form a stable first resonant cavity.

The 3μm light generation route includes pump source 2 5, plano-convex mirror 1 6 and holmium-praseodymium co-doped fluoride ZBLAN fiber 8, plano-convex mirror 1 6 focuses the light emitted by pump source 2 5 to holmium-praseodymium co-doped fluorine The input end of the compound ZBLAN fiber 8, the input end face of the holmium-praseodymium co-doped fluoride ZBLAN fiber 8 is provided with a coating layer 7; between the holmium-praseodymium co-doped fluoride ZBLAN fiber 8 and the dichroic mirror 10 is provided with a plano-convex Mirror three 9, plano-convex mirror three 9 collimate the light output from the holmium-praseodymium co-doped fluoride ZBLAN fiber 8; the second resonant cavity is formed between the coating layer 7 and the mirror 13. The pump source 2 5 is a 1150nm continuous laser diode. The pump source 2 5 continuously and stably outputs the light source. After the light is focused to the coating layer 7 at the input end of the holmium-praseodymium co-doped fluoride ZBLAN fiber 8, 3 μm light is generated, and the 3 μm light propagates horizontally On the dichromatic mirror 10, through the dichromatic mirror 10 to reach the reflector 13, the reflector reflects the 3 μm light to the dichromatic mirror 10 along the horizontal direction, because the dichromatic mirror 10 is inclined 45° relative to the horizontal direction Placed, a part of the 3 μm light is vertically reflected on the dichromatic mirror 2 14, and a part of the 3 μm light continues to pass through the dichromatic mirror 1 10 in the horizontal direction, and is projected to the coating layer 7, thereby forming a second resonant cavity of 3 μm light, 3 μm Light travels back and forth in the second resonant cavity, and the number density of inversion particles at the upper energy level accumulates in large quantities. Through pumping source 2 5, plano-convex mirror 1 6 and holmium-praseodymium co-doped fluoride ZBLAN fiber 8, 3 μm light can be continuously and stably emitted, combined with dichroic mirror 2 14, dichroic mirror 1 10 and reflector 13. A stable second resonant cavity is formed.

The transmittance of fiber Bragg grating 2 to 1550nm light is >99%, and the reflectivity to 2μm light is >99%; the transmittance of coating layer 7 to 1150nm light is >99%, and the reflectivity to 3μm light is >99%. The 1550nm light emitted from the pump source 1 passes through the fiber Bragg grating 2 with a very high transmittance, and the 2 μm light reflected from the mirror 13 is reflected back again by the fiber Bragg grating 2 with a high reflectivity, thereby improving The working efficiency of the first resonant cavity is improved, and the loss is greatly reduced; the 1150nm light emitted from the pump source 2 5 passes through the coating layer 7 with a very high transmittance, while the 3μm light reflected from the mirror is The coating layer 7 is reflected back again with high reflectivity, thereby improving the working efficiency of the second resonant cavity and greatly reducing loss.

Dichroic mirror 10 has a transmittance of >99% for 1150nm light, >99% for 1550nm light and 2μm light reflectance, and 50% for 3μm light; Dichroic mirror 214 has a reflection rate of 1550nm light Rate>99%, 2μm light reflectance=80%, transmittance=20%, 3μm light transmittance>99%. When 1550nm light and 2 μm light reach dichromatic mirror 1 10, they are all reflected on dichromatic mirror 1 14 with high reflectivity; On dichroic mirror 2 14, 1150nm light can hardly pass through dichroic mirror 2 14; when 1550nm light and 3 μm light reach dichromatic mirror 2 14, they are all reflected to dichroic mirror 1 10 with high reflectivity, and 2 μm light reaches dichroic mirror 2 When the dichromatic mirror 2 is 14, 80% of the 2 μm light is reflected, and 20% of the 2 μm light is transmitted through the dichromatic mirror 2 14, forming a stable optical path accurately.

Example 2

As shown in Figures 1 and 2, the pumping source 2 5 is turned on, and the 1150nm light emitted by the pumping source 2 5 is focused on the coating layer 7 of the input end of the holmium-spectrum co-doped ZBLAN optical fiber 8 through the plano-convex mirror 16 to generate The 3 μm light is output from the output end of the holmium-spectrum co-doped ZBLAN fiber 8, the 3 μm light is collimated by the plano-convex mirror 3 9 and propagates to the dichroic mirror 1 10, the 3 μm light passes through the dichroic mirror 1 10, and is transmitted to the plano-convex Mirror 4 11 is focused and propagated by plano-convex mirror 4 11 to the reflector 13 covered with graphene film layer 12; 3 μm light is reflected by reflector 13 and propagates back and forth in the second resonant cavity, and the number of reversed particles in the upper energy level A large amount of density is accumulated; adjusting the power of the pump source 2 5 makes the 3 μm optical power output from the holmium-spectrum co-doped ZBLAN fiber 8 lower, so that the graphene cannot reach a saturated state, and the graphene film is at high loss (that is, at a low Q value ) state; keep the pump source 2 5 in working state, turn on the pump source 1, the 1550nm light emitted by the pump source 1 passes through the fiber Bragg grating 2 and the thulium-holmium co-doped fiber to generate 2μm light, and the 2μm light passes through the second After the color mirror two 14 is reflected to the dichroic mirror one 10, it is reflected to the plano-convex mirror four 11, and the plano-convex mirror four 11 is focused and transmitted to the reflector 13 covered with the graphene film layer 12; 2 μm light is reflected by the reflector 13 Propagating back and forth in the first resonant cavity, the number density of inversion particles of the upper energy level accumulates in large quantities; gradually increasing the output power of the pump source 1, the 2μm amplified spontaneous emission light gradually increases; with the fiber Bragg grating 2 and holmium- The accumulation of particle inversion particle number in spectrum co-doped ZBLAN fiber 8, the light intensity in the resonant cavity gradually increases, with the increase of spontaneous emission light intensity, the saturated absorption coefficient of graphene film decreases, and the spontaneous emission light intensity continues to increase , when the amplified spontaneous emission light intensity is compared with the saturation absorption light intensity of the graphene film, the graphene film absorption reaches the saturation value, is suddenly "bleached" and the absorption coefficient drops to the lowest, and the stable output of the 2μm Q-switched pulsed fiber laser is typical The value pulse width is 490ns, and the repetition frequency is 80kHz. When the signal light of 2μm "bleachs" the graphene film to make its absorption coefficient drop to the minimum rapidly, the number of inverted particles accumulated at 2μm and 3μm is rapidly consumed in a short time, and the two resonances The Q value in the cavity increases sharply to generate laser oscillation while outputting 2μm and 3μm short pulses with high peak power. By adjusting the power of the pump source 1, the control of the repetition frequency of the dual-wavelength pulse can be realized, and the pump source 1 can be increased. The power of the dual-wavelength pulse repetition frequency is increased synchronously; the power of the pump source 1 is reduced, and the dual-wavelength pulse repetition frequency is synchronously decreased.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention. within range.

Claims (7)

1. A method for emitting mid-infrared dual-wavelength pulses with the same repetition frequency, characterized in that it may further comprise the steps: Step 1: Turn on the pump source 2 (5), and the 1150nm light emitted by the pump source 2 (5) is focused by the plano-convex mirror 1 (6) to the coating layer of the input end of the holmium-praseodymium co-doped fluoride ZBLAN fiber (8) On (7), the 3 μm light is output from the output end of the holmium-praseodymium co-doped fluoride ZBLAN fiber (8), and the 3 μm light is collimated by the plano-convex mirror three (9) and propagated to the dichroic mirror one (10), 3 μm The light passes through the dichroic mirror one (10), and transmits to the plano-convex mirror four (11), and is focused and propagated through the plano-convex mirror four (11) to the reflector (13) covered with the graphene film layer (12); The 3μm light is reflected by the mirror (13) and propagates back and forth in the second resonant cavity, and the number density of the upper-level inversion particles accumulates in large quantities; the power of the pump source 2 (5) is adjusted so that the holmium-praseodymium co-doped fluoride ZBLAN The 3 μm optical power output by the optical fiber (8) is low, and the graphene film is in a state of high loss (that is, in a low Q value); Step 2: Keep pump source 2 (5) in working condition, turn on pump source 1 (1), the 1550nm light emitted by pump source 1 (1) passes through fiber Bragg grating (2) and thulium-holmium co-doped fiber Generate 2μm light, the 2μm light is reflected by dichroic mirror 2 (14) to dichroic mirror 1 (10), then reflected to plano-convex mirror 4 (11), focused and propagated to graphene-coated by plano-convex mirror 4 (11) On the reflector (13) of the film layer (12); 2 μm light is reflected by the reflector (13) and travels back and forth in the first resonant cavity, and the number density of reversed particles of the upper energy level accumulates in large quantities; Step 3: Gradually increase the output power of the pump source 1 (1) to amplify the 2 μm spontaneous emission light; with the inversion of the number of particles in the fiber Bragg grating (2) and holmium-praseodymium co-doped fluoride ZBLAN fiber (8) Accumulation, the light intensity in the resonant cavity gradually increases. With the increase of the spontaneous emission light intensity, the saturated absorption coefficient of the graphene film decreases, and the continuous increase of the spontaneous emission light intensity makes the absorption of the graphene film reach saturation. The number of rotating particles is rapidly consumed in a short period of time, the Q value in the resonant cavity increases sharply, laser oscillation is generated, and 2 μm and 3 μm pulses with higher peak power are simultaneously output from the output terminal (15); Step 4: Keep the working state of pump source 1 (1) and pump source 2 (5) at this time. After the number of inversion particles is exhausted, the graphene film returns to a high loss state within the relaxation time. In the working state of pump source 1 (1) and pump source 2 (5), the number of inversion particles in the two gain fibers is accumulated again, reaching the saturation value of graphene, and outputting dual-wavelength pulses again, repeating this to achieve the same Repeated 2μm and 3μm Q-switched pulses. 2. A graphene-based mid-infrared dual-wavelength pulsed fiber laser with the same repetition rate as the method for implementing claim 1, characterized in that: it includes a reflector (13) covered with a graphene film layer (12), the reflector A dichroic mirror one (10) is provided on the same level as the mirror (13), and the dichroic mirror one (10) is arranged at an angle of 45° relative to the horizontal direction. Parallel dichroic mirror two (14), a pulse output terminal (15) is provided above the dichroic mirror two (14); plano-convex is provided between the dichroic mirror one (10) and the reflector (13) Mirror four (11), the plano-convex mirror four (11) can focus the light beam to the mirror (13); the dichroic mirror one (10) is connected with a 3 μm light generation route, and the dichroic mirror two (14 ) is connected with a 2 μm light generation route, and the 3 μm light generation route is parallel to the 2 μm light generation route. 3. A graphene-based mid-infrared dual-wavelength co-repetition frequency pulsed fiber laser as claimed in claim 2, characterized in that: the 2 μm light generation route includes sequentially connected pump sources one (1), optical fiber Bragg grating (2) and thulium-holmium co-doped fiber (3), a plano-convex mirror (4) is arranged between the thulium-holmium co-doped fiber (3) and dichroic mirror 2 (14), and the plano-convex mirror 2 (4) is arranged between the The second convex mirror (4) can collimate the light output from the thulium-holmium co-doped fiber (3); the first resonant cavity is formed between the fiber Bragg grating (2) and the mirror (13); the 3μm light generates The route includes pumping source two (5), plano-convex mirror one (6) and holmium-praseodymium co-doped fluoride ZBLAN fiber (8), and the plano-convex mirror one (6) can launch pumping source two (5) The light of the holmium-praseodymium co-doped fluoride ZBLAN fiber (8) is focused to the input end of the holmium-praseodymium co-doped fluoride ZBLAN fiber (8), and the input end face of the holmium-praseodymium co-doped fluoride ZBLAN fiber (8) is provided with a coating layer (7); A plano-convex mirror three (9) is arranged between the praseodymium co-doped fluoride ZBLAN fiber (8) and the dichroic mirror one (10), and the plano-convex mirror three (9) can convert the holmium-praseodymium co-doped fluoride ZBLAN fiber (8) The output light is collimated; a second resonant cavity is formed between the coating layer (7) and the mirror (13). 4. A graphene-based mid-infrared dual-wavelength co-repetition frequency pulsed fiber laser as claimed in claim 3, characterized in that: the pumping source one (1) is a 1550nm continuous laser diode, and the pumping source Two (5) are 1150nm CW laser diodes. 5. A graphene-based mid-infrared dual-wavelength co-repetition frequency pulsed fiber laser as claimed in claim 4, characterized in that: the transmittance of the fiber Bragg grating (2) to 1550nm light is >99%, and to 2μm The reflectance of light is >99%; the transmittance of the coating layer (7) to 1150nm light is >99%, and the reflectance of 3 μm light is >99%. 6. A graphene-based mid-infrared dual-wavelength co-repetition frequency pulsed fiber laser as claimed in claim 4 or 5, characterized in that: said dichroic mirror one (10) has a transmittance of >99% for 1150nm light, Both the reflectance of 1550nm light and 2μm light are >99%, the reflectivity and transmittance of 3μm light are both 50%; =80%, transmittance=20%, and the transmittance of 3μm light is >99%. 7. A graphene-based mid-infrared dual-wavelength co-repetition frequency pulsed fiber laser as claimed in claim 3, characterized in that: the input end of the thulium-holmium co-doped fiber (3) is set as a straight cut surface, and the The output end of the thulium-holmium co-doped optical fiber (3) is set to be inclined at 8°.