Active and passive Q-switched Yb3 +-doped pulse fiber laser of semiconductor laser pump

Abstract

An active and passive Q-switched Yb < 3 + >-doped pulse fiber laser of a semiconductor laser pump comprises an FBG (fiber bragg grating), an acousto-optic Q switch with a tail fiber, a single-mode fiber, a fiber coupler and a gain fiber which are sequentially connected, a pump light input end of the fiber coupler is provided with an LD (laser diode) pump light source, and the tail end of the gain fiber serves as an output end of the whole pulse laser. The output end of the pulse laser serves as an output reflector of the resonant cavity and forms the resonant cavity of the laser with the FBG. According to the utility model, an all-fiber mode is realized, the coupling efficiency of each connection point is improved, the whole pulse laser is concise, the sensitivity of an optical path to alignment errors is greatly reduced, and the imbalance sensitivity of a system is relatively low. Especially on the Q-switching technology, active and passive Q-switching mechanisms are used, active Q-switching has the function of stabilizing pulses, passive Q-switching based on the SBS effect can narrow the pulse width, and therefore stable pulse output with stable repetition frequency and narrow pulse width is obtained.

Description

TECHNICAL FIELD

[0001] The utility model relates to laser technology field especially relates to a kind of main passive Q doped Yb 3+ Pulse fiber laser. BACKGROUND

[0002] Q fiber laser becomes very attractive laser light source due to its wide application, such as military, surgical operation, laser processing, laser marking, nonlinear frequency conversion, ranging, remote sensing and optical time domain reflectometer. Active Q all-fiber laser and passive Q all-fiber laser based on stimulated Brillouin scattering (SBS) effect have been reported, but the combination of the two is less studied. It is well known that the acousto-optic Q switch with a tail fiber is an active, efficient and fast fiber Q switch that combines traditional acousto-optic Q switch and modern fiber technology. This acousto-optic Q switch is an active Q switch, and all active Q switches can control the pulse repetition frequency to stabilize the pulse sequence.

[0003] Even so, for the tail fiber acousto-optic Q switch, there is still a limit to compressing the pulse width to nanosecond level. In this case, shortening the fiber length is a good way to compress the pulse width; but this may reduce the cavity energy, and the pulse energy and peak power will be reduced. If the doping concentration of the gain medium is increased, which is a remedy for the above problems, concentration quenching may occur due to excited state absorption. In addition, it is not allowed to dope ultra-high concentration of active ions in the fiber in terms of process.

[0004] At present, there is still a lack of corresponding solutions to this problem. INVENTION CONTENTS

[0005] The utility model aims at overcoming the prior art deficiencies, providing a kind of main passive Q doped Yb 3+ Pulse fiber laser.

[0006] The laser comprises an FBG fiber grating, a tail fiber acousto-optic Q switch, a single-mode fiber, an LD pumping light source, a fiber coupler and a gain fiber.

[0007] The FBG fiber grating, the tail fiber acousto-optic Q switch, the single-mode fiber, the fiber coupler and the gain fiber are sequentially connected.

[0008] The single mode optical fiber is connected with the left signal end of the fiber coupler, and the pump light input end of the fiber coupler is provided with an LD pump light source; the right signal end of the fiber coupler is connected with a gain optical fiber, and the tail end of the gain optical fiber is used as the output end of the whole pulse laser, and the output end of the pulse laser is used as the output mirror of the resonant cavity and forms the resonant cavity of the laser with the FBG optical fiber grating.

[0009] The utility model discloses the beneficial effects are:

[0010] 1. using FBG optical fiber grating instead of discrete cavity mirror, and the use of FBG makes the cavity mirror of resonant cavity realize fiber.

[0011] 2. simultaneously utilize the acoustooptic Q switch of tail fiber and the SBS effect of single mode optical fiber and realize the fiber of active and passive Q switch.

[0012] 3. using fiber coupler realizes the input of LD pump light and the oscillation of signal light, and the LD pump light source is the fiber coupling output, and is convenient and is directly fused with fiber coupler.

[0013] 4. the whole device realizes all fiber, improves the coupling efficiency of each connection point, makes the whole of pulse laser appear simple, greatly reduces the sensitivity of optical path alignment straight error, and the misadjustment sensitivity of system is relatively lower.

[0014] 5. on Q technique, use two kinds of active and passive Q mechanism, and active Q has the effect of stable pulse, and passive Q based on SBS effect can narrow pulse width, thereby obtaining stable pulse output with stable repetition frequency and narrow pulse width. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 It is a kind of semiconductor laser pumped active and passive Q doped Yb 3+ The structure diagram of pulse fiber laser;

[0016] Figure 2 It is a kind of semiconductor laser pumped active and passive Q doped Yb 3+ The pulse sequence diagram of the output of pulse fiber laser when working;

[0017] Figure 3 It is a kind of semiconductor laser pumped active and passive Q doped Yb 3+ The laser output spectrum diagram of the pulse fiber laser when working.

[0018] Reference signs:

[0019] 1-FBG fiber grating 2- with tail fiber acousto-optic Q switch 3- single mode optical fiber 4- LD pump light source 5- fiber coupler 6- gain fiber 7- pulse laser output end

[0020] The realization, functional features and advantages of the utility model will be further explained in combination with embodiments and with reference to the drawings. DETAILED DESCRIPTION

[0021] 1. Technical solution:

[0022] Referring to Figure 1 The utility model discloses a kind of main and passive Q-doped Yb 3+ Pulse fiber laser, including FBG fiber grating 1, with tail fiber acousto-optic Q switch 2, single mode optical fiber 3, LD pump light source 4, fiber coupler 5, gain fiber 6;

[0023] FBG fiber grating 1, with tail fiber acousto-optic Q switch 2, single mode optical fiber 3, fiber coupler 5 and gain fiber 6 are sequentially connected;

[0024] Single mode optical fiber 3 is connected with the left signal end of fiber coupler 5, and the pump light input end of fiber coupler 5 is provided with LD pump light source 4;Gain fiber 6 is connected to the right signal end of fiber coupler 5, and the tail end of gain fiber 6 is as the whole pulse laser output end 7, and the pulse laser output end 7 is simultaneously as the output mirror of resonant cavity, and forms the resonant cavity of laser with FBG fiber grating 1.

[0025] Further, the laser diode of LD pump light source 4 is fiber-coupled output semiconductor laser, and its parameters are fiber core diameter 200 μm, NA 0.22, center wavelength 975 nm, maximum output power 50W.

[0026] Further, the temperature of LD pump light source 4 is controlled by electrically cooled TEC system and air cooling system simultaneously, and its control precision is ±0.1 ℃.

[0027] The effect realized thereby is to avoid the shift of pump light wavelength.

[0028] Further, the pump light input end of fiber coupler 5 is directly fusedly connected with the laser diode output tail fiber of LD pump light source 4.

[0029] Further, the full reflection end of resonant cavity adopts FBG fiber grating 1, and the fiber grating is greater than 98% reflectivity at 1083nm, and the loss coefficient is less than 0.0015dB / m.

[0030] Further, the SBS effect in the single-mode optical fiber 3 and the acousto-optic Q-switch 2 with a tail fiber realizes both active and passive Q-switching mechanisms.

[0031] Further, the single-mode optical fiber 3 has a length of 1 km and a core diameter of 10 μm.

[0032] That is, there is a difference in the core size between the single-mode optical fiber 3 and the left signal end of the fiber coupler 5, and the fusion loss between them is slightly larger than that of other fusion points. The FBG optical fiber grating 1, the tail fiber of the acousto-optic Q-switch 2 with a tail fiber and the single-mode optical fiber 3 are well matched in size.

[0033] Further, the gain optical fiber 6 is an 11 m long Yb 3+ doped double-clad fiber with an absorption coefficient of 1.2 dB / m. The gain optical fiber 6 has a core size of 30 μm, an NA of 0.07 and a 350 / 400 μm D-shaped inner cladding, and has the characteristics of a large mode area (LMA).

[0034] The effect achieved thereby is that the system is easy to operate in a single-mode laser, and the output end of the entire all-fiber Q-switched laser has a Fresnel reflectivity (0.04).

[0035] 2. Experimental data

[0036] Referring to the drawings of the specification Figure 2 When the pump power is 30 W, the oscilloscope scanning time is 200 ns per grid, the laser pulse width is about 87 ns, the repetition frequency is about 1.33 MHz, and the time interval between two pulses is about 750 ns on average.

[0037] Referring to the drawings of the specification Figure 3 , the central wavelength of the output laser is 1083 nm, and the spectral width is about 2 nm. In addition, the light near 975 nm is residual pump light.

[0038] Based on the above, the output power is measured by a power meter, and it is found that the average power is 17.3 W. According to the above results and calculations, the laser pulse energy is 0.013 mJ, and the peak power is 149 W. In addition, within a certain range, if the pump power is appropriately reduced, it is found that the pulse width is slightly narrowed. Therefore, in this experiment, a relatively low pump power can make the pulse width narrower to a certain extent.

[0039] In this experiment, the acousto-optic Q-switch and the single-mode optical fiber both play a role in Q-switching. The active acousto-optic Q-switch makes the frequency stable, and the SBS effect in the single-mode optical fiber makes the pulse width narrower. This experiment also embodies the dual advantages of active and passive Q-switching methods.

[0040] 3. Experimental conclusion:

[0041] In this experiment, by using the acousto-optic Q-switch with fiber pigtail and single-mode fiber simultaneously, two kinds of Q-switching mode of Yb 3+ The all-fiber laser is operated experimentally and the pulse width of 87 ns is obtained at the repetition rate of 1.33 MHz. The laser output wavelength is 1083 nm, the pulse energy is 0.013 mJ and the peak power is 149 W. In this experiment, the Q-switching mechanism of high gain in cavity is provided by the acousto-optic Q-switch and SBS effect in single-mode fiber, and the pulse output with stable repetition rate and narrow pulse width is obtained. From the Q-switching mechanism, this method of obtaining pulse laser can be regarded as a special Q-switching technology that the narrow seed pulse generated by SBS effect is gradually amplified in the cavity.

[0042] The basic principle, main features and advantages of the present application are shown and described above, for those skilled in the art, it is obvious that the present application is not limited to the details of the above exemplary embodiments, and can be realized in other specific forms without departing from the spirit or basic characteristics of the present application. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting, the scope of the present application is defined by the appended claims rather than the above description, therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present application. Any reference signs in the claims should not be regarded as limiting and the claims.

[0043] In addition, it should be understood that although the present application is described in the form of embodiments, not every embodiment contains only one independent technical solution, and the description of the specification is only for the sake of clarity, those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that those skilled in the art can understand.

Claims

1. A kind of semiconductor laser pumped main passive Q-switched Yb 3+ Pulsed fiber laser, including FBG fiber grating, tail fiber acousto-optic Q switch, single-mode fiber, LD pump light source, fiber coupler, gain fiber, characterized in that: The FBG fiber grating, the acousto-optic Q-switch with tail fiber, the single-mode fiber, the fiber coupler and the gain fiber are sequentially connected. The single-mode fiber is connected with the left signal end of the fiber coupler, and the pump light input end of the fiber coupler is provided with an LD pump light source; the gain fiber is connected with the right signal end of the fiber coupler, and the tail end of the gain fiber serves as the output end of the whole pulse laser, which simultaneously serves as the output mirror of the resonant cavity and forms the resonant cavity of the laser with the FBG fiber grating.

2. A semiconductor laser-pumped, active-passive Q-switched Yb-doped fiber laser according to claim 1, wherein the active-passive Q-switching element is a semiconductor saturable absorber mirror (SESAM). 3+ A pulsed fiber laser, characterized in that The laser diode of the LD pump light source is a fiber-coupled output semiconductor laser, which has a fiber core diameter of 200 μm, an NA of 0.22, a central wavelength of 975 nm and a maximum output power of 50 W.

3. A semiconductor laser-pumped, passively Q-switched Yb-doped fiber laser as claimed in claim 1, wherein the semiconductor saturable absorber mirror is a semiconductor saturable absorber mirror with a bandgap of 1.0-1.2 μm. 3+ A pulsed fiber laser, characterized in that The temperature of the LD pump light source is simultaneously controlled by an electrically-cooled TEC system and an air-cooled system, and the control precision is ±0.1 ℃.

4. A semiconductor laser-pumped, active-passive Q-switched Yb-doped fiber laser according to claim 1, wherein the active-passive Q-switching element is a semiconductor saturable absorber mirror (SESAM). 3+ A pulsed fiber laser, characterized in that The pump light input end of the fiber coupler is directly fusedly connected with the output tail fiber of the LD pump light source.

5. A semiconductor laser-pumped, passively Q-switched Yb-doped fiber laser as claimed in claim 1, wherein the semiconductor saturable absorber mirror is a semiconductor saturable absorber mirror with a bandgap of 1.0-1.2 μm. 3+ A pulsed fiber laser, characterized in that The FBG fiber grating is used for the full reflection end of the resonant cavity, which has a reflectivity of more than 98% at 1083 nm and a loss coefficient of less than 0.0015 dB / m.

6. A semiconductor laser-pumped, passively Q-switched Yb-doped fiber laser as claimed in claim 1, wherein the semiconductor saturable absorber mirror is a semiconductor saturable absorber mirror with a bandgap of 1.0-1.2 μm. 3+ A pulsed fiber laser, characterized in that The SBS effect in the acousto-optic Q-switch with tail fiber and the single-mode fiber realizes the active and passive Q-switching working mechanisms.

7. A semiconductor laser-pumped, passively Q-switched Yb-doped fiber laser as claimed in claim 1, wherein the semiconductor saturable absorber mirror is a semiconductor saturable absorber mirror with a bandgap of 1.0-1.2 μm. 3+ A pulsed fiber laser, characterized in that The length of the single-mode fiber is 1 km, and the fiber core diameter is 10 μm.

8. A semiconductor laser-pumped, passively Q-switched Yb-doped fiber laser as claimed in claim 1, wherein the semiconductor saturable absorber mirror is a semiconductor saturable absorber mirror with a bandgap of 1.0-1.2 μm. 3+ A pulsed fiber laser, characterized in that The gain fiber is a 11 m long Yb-doped 3+ Double-clad fiber with an absorption coefficient of 1.2 dB / m; The gain fiber has a fiber core size of 30 μm, an NA of 0.07, a 350 / 400 μm D-shaped inner cladding and a large mode area (LMA) characteristic.

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