A high peak power high energy pulsed laser generating device and method

Abstract

The application discloses a high-peak-power high-energy pulse laser generating device and method, and belongs to the technical field of pulse lasers.The device comprises a high-reflectivity fiber grating, a forward pumping combiner, a gain fiber, an energy transmission fiber, a backward pumping combiner, a pumping module, a pumping source driving power supply, a low-reflectivity fiber grating and a fiber output end.The device for generating pulse lasers has simple structure and strong power expansion performance, and can be used for laser processing and laser cleaning.

Description

Technical Field

[0001] This invention belongs to the field of pulsed laser technology, and particularly relates to a device and method for generating high peak power and high energy pulsed lasers. Background Technology

[0002] High peak power fiber lasers have significant applications in industrial processing and scientific research. There are two main methods for generating high peak power lasers: Q-switching (Q value, the quality factor of an optical resonator) and mode-locking. Q-switching is typically used to achieve pulsed lasers with high peak power and high pulse energy.

[0003] Q-switching technology is divided into two types: active Q-switching and passive Q-switching. Active Q-switching offers flexible control but requires a matching control circuit. Moreover, the power handling capability of the Q-switching device is usually poor, and further optical amplification is needed to achieve higher power, resulting in a complex system structure. Passive Q-switching has a simpler structure and usually uses a saturable absorber for Q-switching. However, it has weaker pulse parameter control capability, and peak power, pulse width, and repetition rate are somewhat correlated, which limits its practical application.

[0004] Another type of passive Q-switching method utilizes nonlinearity for Q-switching, primarily leveraging the stimulated Brillouin scattering effect. Existing Q-switched fiber lasers have relatively low output pulse energies, with average powers in the tens of watts range, which cannot meet the needs of some laser applications requiring both high average power and high peak power. Summary of the Invention

[0005] To address the aforementioned technical problems, this patent proposes a high peak power, high energy pulsed laser generation device and method.

[0006] The first aspect of this invention discloses a high peak power, high energy pulsed laser generating device. The device includes: a high reflectivity fiber grating (1), a forward pump combiner (2), a gain fiber (3), a power transfer fiber (4), a backward pump combiner (5), a pump module (6), a pump source driving power supply (7), a low reflectivity fiber grating (8), and an optical fiber output end (9); wherein, an all-fiber structure fiber oscillator is formed by sequentially arranging the high reflectivity fiber grating (1), the forward pump combiner (2), the gain fiber (3), the backward pump combiner (5), and the low reflectivity fiber grating (8); wherein, the forward pump combiner (2) and the backward pump combiner (5) form an all-fiber structure fiber oscillator. Each of the bundlers (5) includes several pump modules (6), which are driven by the pump source driving power supply (7). The pump source driving power supply (7) is used to control the power of the pump module (6) and the timing of the pump laser. The fiber output end (9) is connected to the low reflectivity fiber grating (8). The energy transmission fiber (4) is located between the gain fiber (3) and the back pump bundler (5). The energy transmission fiber (4) is connected to the gain fiber (3) and the back pump bundler (5) respectively by fiber fusion splicing to generate stimulated Raman scattering effect.

[0007] According to the apparatus of the first aspect of the present invention, the gain fiber (3) is an optical fiber with a core-cladding size uniform along the longitudinal direction or an optical fiber with a core-cladding size varying along the longitudinal direction; and the gain fiber (3) is a rare earth ion-doped optical fiber, wherein the rare earth ions include ytterbium ions, erbium ions, thulium ions, and holmium ions.

[0008] According to the apparatus of the first aspect of the present invention, the power transmission fiber (4) is a non-rare earth doped fiber, and the core cladding size of its connection end is the same as the parameter of the connection end of the gain fiber (3), and is also the same as the parameter of the connection end of the backward pump combiner (5); the other positions of the power transmission fiber (4) are either fibers with a uniform core cladding size along the longitudinal direction or fibers with a varying core cladding size along the longitudinal direction; the length of the power transmission fiber (4) is controlled according to the design power and Raman threshold, and the length range is 3-30 meters.

[0009] According to the apparatus of the first aspect of the present invention, the center wavelength of the high reflectivity fiber grating (1) is located within the gain bandwidth of the gain fiber (3), the reflectivity of the high reflectivity fiber grating (1) is greater than 95%, the reflection bandwidth is >1nm, and its core and cladding diameters are the same as those of the connection end of the gain fiber (3).

[0010] According to the apparatus of the first aspect of the present invention, the center wavelength of the low reflectivity fiber grating (8) is the same as the center wavelength of the high reflectivity fiber grating (1), the reflectivity of the low reflectivity fiber grating (8) is in the range of 4%-50%, the reflectivity bandwidth is >0.1nm, and its core and cladding diameters are the same as those of the connection end of the gain fiber (3).

[0011] According to the apparatus of the first aspect of the present invention, the forward pump combiner (2) includes a signal end, a pump end and an output end, wherein the fiber core diameter of the signal end of the forward pump combiner (2) is the same as the fiber core diameter of the high reflectivity fiber grating (1), and the fiber core and cladding diameters of the output end of the forward pump combiner (2) are the same as the fiber core and cladding diameters of the gain fiber (3).

[0012] According to the apparatus of the first aspect of the present invention, the backward pump combiner (5) includes a signal end, a pump end and an output end, wherein the fiber core diameter of the signal end of the backward pump combiner (5) is the same as the core and cladding diameter of the gain fiber (3), and the fiber core diameter of the output end of the backward pump combiner (5) is the same as the core diameter of the low reflectivity fiber grating (8).

[0013] According to the apparatus of the first aspect of the present invention, the pump module (6) is connected to the optical fibers at the pump ends of the forward pump combiner (2) and the backward pump combiner (5), respectively, and the optical fibers at the pump ends of the forward pump combiner (2) and the backward pump combiner (5) have the same optical fiber size; the center wavelength of the pump module (6) is located within the absorption band of the gain fiber (3) and is located at a wavelength position where the wavelength absorption exceeds a first threshold; the pump source driving power supply (7) is a DC power supply used to control the output current and output power of the pump module (6), and the pump source driving power supply (7) is a continuous output current or a pulse modulation output, wherein the modulation current pulse has a controllable pulse width and a controllable repetition rate.

[0014] According to the apparatus of the first aspect of the present invention, the laser output module (9) includes a cladding optical filter and an optical fiber output cap, wherein the core diameter and numerical aperture of the optical fiber used by the laser output module (9) are not less than the size used by the backward pump combiner (5).

[0015] A second aspect of the present invention discloses a method for generating high peak power, high energy pulsed laser. The method generates the high peak power, high energy pulsed laser based on the apparatus described in the first aspect of the present invention.

[0016] The device includes: a high-reflectivity fiber grating (1), a forward-pumped combiner (2), a gain fiber (3), a power transfer fiber (4), a backward-pumped combiner (5), a pump module (6), a pump source drive power supply (7), a low-reflectivity fiber grating (8), and an optical fiber output end (9); wherein, the high-reflectivity fiber grating (1), the forward-pumped combiner (2), the gain fiber (3), the backward-pumped combiner (5), and the low-reflectivity fiber grating (8) are arranged sequentially to form an all-fiber structure fiber oscillator; wherein, the forward-pumped combiner (2) and the backward-pumped combiner (5) form an all-fiber structure fiber oscillator. Each of the bundlers (5) includes several pump modules (6), which are driven by the pump source driving power supply (7). The pump source driving power supply (7) is used to control the power of the pump module (6) and the timing of the pump laser. The fiber output end (9) is connected to the low reflectivity fiber grating (8). The energy transmission fiber (4) is located between the gain fiber (3) and the back pump bundler (5). The energy transmission fiber (4) is connected to the gain fiber (3) and the back pump bundler (5) respectively by fiber fusion splicing to generate stimulated Raman scattering effect.

[0017] The method specifically includes: the pump source driving power supply (7) generates a pulse width driving current to drive the pump module (6) to generate pump light. The pump light is injected into the resonant cavity via the forward pump combiner (2) and the backward pump combiner (5). After the gain fiber (3) absorbs the pump light, it generates quasi-continuous laser light under the action of the high reflectivity fiber grating (1) and the low reflectivity fiber grating (8). When the pump power exceeds a second threshold, stimulated Raman scattering occurs in the resonant cavity, thereby adjusting the Q value in the resonant cavity. The laser operating mode changes from the quasi-continuous laser state to the Q-switched state, thereby obtaining a high peak power pulsed laser output. The Q value is the quality factor of the resonant cavity.

[0018] According to the method of the second aspect of the present invention, the gain fiber (3) is an optical fiber with a uniform core-cladding size along the longitudinal direction or an optical fiber with a varying core-cladding size along the longitudinal direction; and the gain fiber (3) is a rare earth ion-doped optical fiber, wherein the rare earth ions include ytterbium ions, erbium ions, thulium ions, and holmium ions.

[0019] According to the method of the second aspect of the present invention, the power transmission fiber (4) is a non-rare earth doped fiber, and the core cladding size of its connection end is the same as the parameter of the connection end of the gain fiber (3), and is also the same as the parameter of the connection end of the backward pump combiner (5); the other positions of the power transmission fiber (4) are fibers with uniform core cladding size along the longitudinal direction or fibers with varying core cladding size along the longitudinal direction; the length of the power transmission fiber (4) is controlled according to the design power and Raman threshold, and the length range is 3-30 meters.

[0020] According to the method of the second aspect of the present invention, the center wavelength of the high reflectivity fiber grating (1) is located within the gain bandwidth of the gain fiber (3), the reflectivity of the high reflectivity fiber grating (1) is greater than 95%, the reflection bandwidth is >1nm, and its core and cladding diameters are the same as those of the connection end of the gain fiber (3).

[0021] According to the method of the second aspect of the present invention, the center wavelength of the low reflectivity fiber grating (8) is the same as the center wavelength of the high reflectivity fiber grating (1), the reflectivity of the low reflectivity fiber grating (8) is in the range of 4%-50%, the reflectivity bandwidth is >0.1nm, and its core and cladding diameters are the same as those of the connection end of the gain fiber (3).

[0022] According to the method of the second aspect of the present invention, the forward pump combiner (2) includes a signal end, a pump end and an output end, wherein the fiber core diameter of the signal end of the forward pump combiner (2) is the same as the fiber core diameter of the high reflectivity fiber grating (1), and the fiber core and cladding diameters of the output end of the forward pump combiner (2) are the same as the fiber core and cladding diameters of the gain fiber (3).

[0023] According to a second aspect of the present invention, the backward pump combiner (5) includes a signal end, a pump end and an output end, wherein the fiber core diameter of the signal end of the backward pump combiner (5) is the same as the core and cladding diameter of the gain fiber (3), and the fiber core diameter of the output end of the backward pump combiner (5) is the same as the core diameter of the low reflectivity fiber grating (8).

[0024] According to the method of the second aspect of the present invention, the pump module (6) is connected to the optical fibers at the pump ends of the forward pump combiner (2) and the backward pump combiner (5), respectively, and the optical fibers at the pump ends of the forward pump combiner (2) and the backward pump combiner (5) have the same optical fiber size; the center wavelength of the pump module (6) is located within the absorption band of the gain fiber (3) and is located at a wavelength position where the wavelength absorption exceeds a first threshold; the pump source driving power supply (7) is a DC power supply used to control the output current and output power of the pump module (6), and the pump source driving power supply (7) is a continuous output current or a pulse modulation output, wherein the modulation current pulse has a controllable pulse width and a controllable repetition rate.

[0025] According to the method of the second aspect of the present invention, the laser output module (9) includes a cladding optical filter and an optical fiber output cap, wherein the core diameter and numerical aperture of the optical fiber used in the laser output module (9) are not less than the size used in the backward pump combiner (5).

[0026] In summary, the technical solution provided by this invention is based on the high peak power pulse output achieved by relaxation oscillation caused by stimulated Raman scattering in the oscillator. Combined with the relaxation oscillation process of the oscillator, it achieves an effect similar to Q-switching. The pulsed laser generation method has a simple structure and strong power scalability, and can be used in laser processing, laser cleaning and other fields. Attached Figure Description

[0027] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0028] Figure 1 This is a first structural composition diagram of a high peak power high energy pulsed laser generating device according to an embodiment of the present invention;

[0029] Figure 2 This is a second structural diagram of a high peak power high energy pulsed laser generating device according to an embodiment of the present invention;

[0030] Figure 3 This is a third structural diagram of a high peak power, high energy pulsed laser generating device according to an embodiment of the present invention;

[0031] Figure 4 This is a schematic diagram of the pulse output of a high peak power high energy pulsed laser generator according to an embodiment of the present invention;

[0032] in,Figures 1-3 The reference numerals in the attached diagram are as follows: 1-High reflectivity fiber grating, 2-Forward pump combiner, 3-Gain fiber, 4-Power fiber, 5-Backward pump combiner, 6-Pump module, 7-Pump source drive power supply, 8-Low reflectivity fiber grating, 9-Fiber output end. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] The first aspect of this invention discloses a high peak power, high energy pulsed laser generation device. By designing stimulated Raman scattering in an optical fiber resonator and adjusting the signal light loss, combined with the relaxation oscillation process in the resonator, high peak power pulse output is achieved. The pulse energy and average power can be easily adjusted by controlling the length of the energy-transmitting optical fiber and the timing of the pump source drive power supply output current, representing a novel passive Q-switching scheme.

[0035] Figure 1 This is a first structural diagram of a high peak power, high energy pulsed laser generating device according to an embodiment of the present invention; as shown. Figure 1 As shown, its principle is based on the relaxation oscillation technique caused by stimulated Raman scattering. The structure of the pulsed laser generation method includes at least: a high reflectivity fiber grating (1), a forward pump combiner (2), a gain fiber (3), a power transfer fiber (4), a backward pump combiner (5), a pump module (6), a pump source driving power supply (7), a low reflectivity fiber grating (8), and a fiber output end (9); wherein the high reflectivity fiber grating (1), the forward pump combiner (2), the gain fiber (3), the backward pump combiner (5), and the low reflectivity fiber grating (8) form an all-fiber structure fiber oscillator; the power transfer fiber (4) is located after the gain fiber (3) and is connected to the gain fiber (3) and the backward pump combiner (5) by fiber fusion splicing to generate stimulated Raman scattering effect, thereby realizing a function similar to Q-switching; the gain fiber (3) is a rare earth ion-doped fiber; the pump source driving power supply (7) can control the power of the pump module (6) and also control the timing of the pump laser.

[0036] Furthermore, the gain fiber (3) can be a fiber with a uniform core-cladding size along the longitudinal direction, or a fiber with a varying core-cladding size along the longitudinal direction, such as a tapered fiber.

[0037] Furthermore, the rare earth ions include ytterbium ions, erbium ions, thulium ions, and holmium ions.

[0038] Furthermore, the power transmission fiber (4) is a non-rare earth doped fiber, and the core cladding size at its connection end is the same as the parameters at the connection end of the gain fiber (3) and the backward pump combiner (5). Other positions can be fibers with uniform core cladding size along the longitudinal direction, or fibers with varying core cladding size along the longitudinal direction, such as tapered fibers.

[0039] Furthermore, the length of the power transmission fiber (4) can be adjusted and controlled according to the designed power and Raman threshold, typically ranging from 3 to 30 meters.

[0040] Furthermore, the center wavelength of the high reflectivity fiber grating (1) is located within the gain bandwidth of the gain fiber (3), the reflectivity is >95%, the reflection bandwidth is >1nm, and the core and cladding diameters are the same as those of the connection end of the gain fiber (3).

[0041] Furthermore, the center wavelength of the low reflectivity fiber grating (8) is the same as that of the high reflectivity fiber grating (1), the reflectivity is 4%-50%, the reflection bandwidth is >0.1nm, and the core and cladding diameters are the same as those of the connection end of the gain fiber (3).

[0042] Furthermore, the forward pump combiner (2) includes a signal end, a pump end, and an output end, wherein the fiber core diameter of the signal end is the same as the fiber core diameter of the high reflectivity fiber grating (1), and the fiber core and cladding diameters of the output end are the same as the fiber core and cladding diameters of the gain fiber (3).

[0043] Furthermore, the backward pump combiner (5) includes a signal end, a pump end, and an output end, wherein the fiber core diameter of the signal end is the same as the core and cladding diameter of the gain fiber (3), and the fiber core diameter of the output end is the same as the core diameter of the low reflectivity fiber grating (8).

[0044] Furthermore, the pump module (6) is connected to the pump end optical fibers of the forward pump combiner (2) and the backward pump combiner (5), and the optical fibers of the two are of the same size.

[0045] Furthermore, the center wavelength of the pump module (6) is located within the absorption band of the gain fiber (3), typically at a wavelength with high absorption.

[0046] Furthermore, the pump source drive power supply (7) is a DC power supply used to control the output current of the pump module (6), thereby controlling its output power.

[0047] Furthermore, the pump source drive power supply (7) can be a continuous output current or a pulse-modulated output, and the pulse width and repetition frequency of the modulated current pulse are controllable.

[0048] Furthermore, the laser output module (9) includes a cladding light filter and an optical fiber output cap. The laser output module (9) uses an optical fiber whose core diameter and numerical aperture are not less than the corresponding optical parameters of the output fiber of the backward pump combiner (5).

[0049] Specifically, Figure 1 The structure is a bidirectional pump oscillator structure, including a high reflectivity fiber grating (1), a forward pump combiner (2), a gain fiber (3), a power transfer fiber (4), a backward pump combiner (5), a low reflectivity fiber grating (8), and an optical fiber output end (9) which are optically connected in sequence; the pump module (6) is optically connected to the pump ends of the forward pump combiner (2) and the backward pump combiner (5); the pump source drive power supply (7) is electrically connected to the pump module (6) to drive it to generate pump light output.

[0050] The high reflectivity fiber grating (1) has a center wavelength of 1080nm, a reflectivity of 99%, a reflection bandwidth of 3nm, and fiber parameters of 30 / 400μm.

[0051] The forward pump combiner (2) has a signal end fiber of 30 / 400μm, an output end fiber of 30 / 600μm, a pump end fiber of 135 / 155μm, and a signal end fiber core insertion loss of 0.1dB.

[0052] The gain fiber (3) is a 30 / 600μm ytterbium-doped fiber with a core numerical aperture of 0.06, an absorption coefficient of 1.2dB / m@976nm, and a length of 17 meters.

[0053] The power transmission fiber (4) is a 30 / 600μm germanium-doped fiber with a core numerical aperture of 0.06 and a length of 10 meters.

[0054] The backward pump combiner (5) has a signal end fiber of 30 / 400μm, an output end fiber of 30 / 600μm, a pump end fiber of 135 / 155μm, and a signal end fiber core insertion loss of 0.1dB.

[0055] The pump module (6) consists of 18 semiconductor pump sources with a center wavelength of 976nm. The output fiber size of each pump source is 135 / 155μm and the output power is 300W.

[0056] The pump source drive power supply (7) can output current continuously or pulsed current. When pulsed, the modulation frequency is 100Hz-10kHz, the pulse width can be as low as 10μs, and the duty cycle is adjustable.

[0057] The low reflectivity fiber grating (8) has a center wavelength of 1080nm, a reflectivity of 10%, a reflection bandwidth of 2nm, and fiber parameters of 30 / 400μm.

[0058] The optical fiber output end (9) includes a cladding optical filter and an output cap. The optical fiber is 50 / 400μm and 3 meters long.

[0059] During operation, the pump source driving power supply (7) generates a driving current with a pulse width of 50 μs and a repetition rate of 1 kHz, driving the pump module (6) to generate pump light, which is injected into the resonant cavity from the forward pump combiner (2) and the backward pump combiner (5). After the gain fiber (3) absorbs the pump light, it generates a quasi-continuous laser of 1080 nm under the action of the high reflectivity fiber grating (1) and the low reflectivity fiber grating (8). When the pump power is increased, stimulated Raman scattering is generated in the resonant cavity, thereby adjusting the Q value in the cavity. At this time, the laser working mode will change from the original quasi-continuous state to the Q-switched state, thereby obtaining a pulse with high peak power. Using this embodiment, a 1080 nm band pulsed laser output with an average power greater than 500 W and a peak power greater than 30 kW can be obtained.

[0060] Figure 2 This is a second structural diagram of a high peak power, high energy pulsed laser generating device according to an embodiment of the present invention; as shown. Figure 2 As shown, this is commonly referred to as a forward-pumped oscillator structure, and... Figure 1 Compared to the elimination of the backward pump combiner (5), its structure includes a high reflectivity fiber grating (1), a forward pump combiner (2), a gain fiber (3), a power transmission fiber (4), a low reflectivity fiber grating (8), and an optical fiber output end (9) connected in sequence optically; the pump module (6) is optically connected to the pump end of the forward pump combiner (2); the pump source drive power supply (7) is electrically connected to the pump module (6) to drive it to generate pump light output.

[0061] The high reflectivity fiber grating (1) has a center wavelength of 1080nm, a reflectivity of 99%, a reflection bandwidth of 3nm, and fiber parameters of 30 / 400μm.

[0062] The forward pump combiner (2) has a signal end fiber of 30 / 400μm, an output end fiber of 30 / 600μm, a pump end fiber of 135 / 155μm, and a signal end fiber core insertion loss of 0.1dB.

[0063] The gain fiber (3) is a 30 / 600μm ytterbium-doped fiber with a core numerical aperture of 0.06, an absorption coefficient of 1.2dB / m@976nm, and a length of 17 meters.

[0064] The power transmission fiber (4) is a 30 / 600μm germanium-doped fiber with a core numerical aperture of 0.06 and a length of 10 meters.

[0065] The pump module (6) consists of 18 semiconductor pump sources with a center wavelength of 976nm. The output fiber size of each pump source is 135 / 155μm and the output power is 300W.

[0066] The pump source drive power supply (7) can output current continuously or pulsed current. When pulsed, the modulation frequency is 100Hz-10kHz, the pulse width can be as low as 10μs, and the duty cycle is adjustable.

[0067] The low-reflectivity fiber grating (8) has a center wavelength of 1080nm, a reflectivity of 10%, a reflection bandwidth of 2nm, and fiber parameters of 30 / 600μm.

[0068] The optical fiber output end (9) includes a cladding optical filter and an output cap. The optical fiber is 50 / 600μm and 3 meters long.

[0069] During operation, the pump source driving power supply (7) generates a driving current with a pulse width of 50μs and a repetition rate of 1kHz, driving the pump module (6) to generate pump light, which is injected into the resonant cavity from the forward pump combiner (2). After the gain fiber (3) absorbs the pump light, it generates a quasi-continuous laser of 1080nm under the action of the high reflectivity fiber grating (1) and the low reflectivity fiber grating (8). When the pump power is increased, stimulated Raman scattering is generated in the resonant cavity, thereby adjusting the Q value in the cavity. At this time, the laser working mode will change from the original quasi-continuous state to the Q-switched state, thereby obtaining a pulse with high peak power. Using this embodiment, a 1080nm band pulsed laser output with an average power greater than 300W and a peak power greater than 20kW can be obtained.

[0070] Figure 3 This is a third structural diagram of a high peak power, high energy pulsed laser generating device according to an embodiment of the present invention; as shown. Figure 3 As shown, this is commonly referred to as a backward-pumped oscillator structure, and... Figure 1 Compared to the elimination of the forward pump combiner (2), its structure includes a high reflectivity fiber grating (1), a gain fiber (3), a power transmission fiber (4), a backward pump combiner (5), a low reflectivity fiber grating (8), and an optical fiber output end (9) connected in sequence optically; the pump module (6) is optically connected to the pump end of the backward pump combiner (5); the pump source drive power supply (7) is electrically connected to the pump module (6) to drive it to generate pump light output.

[0071] The high reflectivity fiber grating (1) has a center wavelength of 1080nm, a reflectivity of 99%, a reflection bandwidth of 3nm, and fiber parameters of 30 / 600μm.

[0072] The gain fiber (3) is a 30 / 600μm ytterbium-doped fiber with a core numerical aperture of 0.06, an absorption coefficient of 1.2dB / m@976nm, and a length of 17 meters.

[0073] The power transmission fiber (4) is a 30 / 600μm germanium-doped fiber with a core numerical aperture of 0.06 and a length of 10 meters.

[0074] The backward pump combiner (5) has a signal end fiber of 30 / 400μm, an output end fiber of 30 / 600μm, a pump end fiber of 135 / 155μm, and a signal end fiber core insertion loss of 0.1dB.

[0075] The pump module (6) consists of 18 semiconductor pump sources with a center wavelength of 976nm. The output fiber size of each pump source is 135 / 155μm and the output power is 300W.

[0076] The pump source drive power supply (7) can output current continuously or pulsed current. When pulsed, the modulation frequency is 100Hz-10kHz, the pulse width can be as low as 10μs, and the duty cycle is adjustable.

[0077] The low reflectivity fiber grating (8) has a center wavelength of 1080nm, a reflectivity of 10%, a reflection bandwidth of 2nm, and fiber parameters of 30 / 400μm.

[0078] The optical fiber output end (9) includes a cladding optical filter and an output cap. The optical fiber is 50 / 400μm and 3 meters long.

[0079] During operation, the pump source driving power supply (7) generates a driving current with a pulse width of 50 μs and a repetition rate of 1 kHz, driving the pump module (6) to generate pump light, which is injected into the resonant cavity from the back pump combiner (5). After the gain fiber (3) absorbs the pump light, it generates a quasi-continuous laser of 1080 nm under the action of the high reflectivity fiber grating (1) and the low reflectivity fiber grating (8). When the pump power is increased, stimulated Raman scattering is generated in the resonant cavity, thereby adjusting the Q value in the cavity. At this time, the laser working mode will change from the original quasi-continuous state to the Q-switched state, thereby obtaining a pulse with high peak power. Using this embodiment, a 1080 nm band pulsed laser output with an average power greater than 600 W and a peak power greater than 40 kW can be obtained.

[0080] Figure 4This is a schematic diagram of the pulse output of a high peak power, high energy pulsed laser generator according to an embodiment of the present invention; as shown. Figure 4 As shown, the pulse width of the quasi-continuous pulse is 50μs. When the Q-switched state is reached, the output laser changes from the quasi-continuous (lower peak power) state to the Q-switched (higher peak power) state, and the output pulse is stable.

[0081] A second aspect of the present invention discloses a method for generating high peak power, high energy pulsed laser. The method generates the high peak power, high energy pulsed laser based on the apparatus described in the first aspect of the present invention.

[0082] The device includes: a high-reflectivity fiber grating (1), a forward-pumped combiner (2), a gain fiber (3), a power transfer fiber (4), a backward-pumped combiner (5), a pump module (6), a pump source drive power supply (7), a low-reflectivity fiber grating (8), and an optical fiber output end (9); wherein, the high-reflectivity fiber grating (1), the forward-pumped combiner (2), the gain fiber (3), the backward-pumped combiner (5), and the low-reflectivity fiber grating (8) are arranged sequentially to form an all-fiber structure fiber oscillator; wherein, the forward-pumped combiner (2) and the backward-pumped combiner (5) form an all-fiber structure fiber oscillator. Each of the bundlers (5) includes several pump modules (6), which are driven by the pump source driving power supply (7). The pump source driving power supply (7) is used to control the power of the pump module (6) and the timing of the pump laser. The fiber output end (9) is connected to the low reflectivity fiber grating (8). The energy transmission fiber (4) is located between the gain fiber (3) and the back pump bundler (5). The energy transmission fiber (4) is connected to the gain fiber (3) and the back pump bundler (5) respectively by fiber fusion splicing to generate stimulated Raman scattering effect.

[0083] The method specifically includes: the pump source driving power supply (7) generates a pulse width driving current to drive the pump module (6) to generate pump light. The pump light is injected into the resonant cavity via the forward pump combiner (2) and the backward pump combiner (5). After the gain fiber (3) absorbs the pump light, it generates quasi-continuous laser light under the action of the high reflectivity fiber grating (1) and the low reflectivity fiber grating (8). When the pump power exceeds a second threshold, stimulated Raman scattering occurs in the resonant cavity, thereby adjusting the Q value in the resonant cavity. The laser operating mode changes from the quasi-continuous laser state to the Q-switched state, thereby obtaining a high peak power pulsed laser output. The Q value is the quality factor of the resonant cavity.

[0084] According to the method of the second aspect of the present invention, the gain fiber (3) is an optical fiber with a uniform core-cladding size along the longitudinal direction or an optical fiber with a varying core-cladding size along the longitudinal direction; and the gain fiber (3) is a rare earth ion-doped optical fiber, wherein the rare earth ions include ytterbium ions, erbium ions, thulium ions, and holmium ions.

[0085] According to the method of the second aspect of the present invention, the power transmission fiber (4) is a non-rare earth doped fiber, and the core cladding size of its connection end is the same as the parameter of the connection end of the gain fiber (3), and is also the same as the parameter of the connection end of the backward pump combiner (5); the other positions of the power transmission fiber (4) are fibers with uniform core cladding size along the longitudinal direction or fibers with varying core cladding size along the longitudinal direction; the length of the power transmission fiber (4) is controlled according to the design power and Raman threshold, and the length range is 3-30 meters.

[0086] According to the method of the second aspect of the present invention, the center wavelength of the high reflectivity fiber grating (1) is located within the gain bandwidth of the gain fiber (3), the reflectivity of the high reflectivity fiber grating (1) is greater than 95%, the reflection bandwidth is >1nm, and its core and cladding diameters are the same as those of the connection end of the gain fiber (3).

[0087] According to the method of the second aspect of the present invention, the center wavelength of the low reflectivity fiber grating (8) is the same as the center wavelength of the high reflectivity fiber grating (1), the reflectivity of the low reflectivity fiber grating (8) is in the range of 4%-50%, the reflectivity bandwidth is >0.1nm, and its core and cladding diameters are the same as those of the connection end of the gain fiber (3).

[0088] According to the method of the second aspect of the present invention, the forward pump combiner (2) includes a signal end, a pump end and an output end, wherein the fiber core diameter of the signal end of the forward pump combiner (2) is the same as the fiber core diameter of the high reflectivity fiber grating (1), and the fiber core and cladding diameters of the output end of the forward pump combiner (2) are the same as the fiber core and cladding diameters of the gain fiber (3).

[0089] According to a second aspect of the present invention, the backward pump combiner (5) includes a signal end, a pump end and an output end, wherein the fiber core diameter of the signal end of the backward pump combiner (5) is the same as the core and cladding diameter of the gain fiber (3), and the fiber core diameter of the output end of the backward pump combiner (5) is the same as the core diameter of the low reflectivity fiber grating (8).

[0090] According to the method of the second aspect of the present invention, the pump module (6) is connected to the optical fibers at the pump ends of the forward pump combiner (2) and the backward pump combiner (5), respectively, and the optical fibers at the pump ends of the forward pump combiner (2) and the backward pump combiner (5) have the same optical fiber size; the center wavelength of the pump module (6) is located within the absorption band of the gain fiber (3) and is located at a wavelength position where the wavelength absorption exceeds a first threshold; the pump source driving power supply (7) is a DC power supply used to control the output current and output power of the pump module (6), and the pump source driving power supply (7) is a continuous output current or a pulse modulation output, wherein the modulation current pulse has a controllable pulse width and a controllable repetition rate.

[0091] According to the method of the second aspect of the present invention, the laser output module (9) includes a cladding optical filter and an optical fiber output cap, wherein the core diameter and numerical aperture of the optical fiber used in the laser output module (9) are not less than the size used in the backward pump combiner (5).

[0092] In summary, the technical solution disclosed in this invention achieves modulation by designing stimulated Raman scattering in the fiber optic resonant cavity, similar to a passive Q-switching scheme. This method has a simple structure, high average power, and does not require further power amplification, making it suitable for applications requiring both high average power and high pulse peak power. Furthermore, by controlling the length of the power transmission fiber and controlling the pulse pump in the time domain of the pump source drive power supply, the average power and pulse energy can be further controlled, thereby flexibly achieving the desired pulse energy.

[0093] Please note that the technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments have been described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. The above embodiments only illustrate several implementation methods of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A high peak power, high energy pulsed laser generating device, characterized in that, The device includes: a high reflectivity fiber grating (1), a forward pump combiner (2), a gain fiber (3), a power transfer fiber (4), a backward pump combiner (5), a pump module (6), a pump source drive power supply (7), a low reflectivity fiber grating (8), and an optical fiber output end (9). The fiber oscillator is composed of an all-fiber structure, consisting of the high-reflectivity fiber grating (1), the forward pump combiner (2), the gain fiber (3), the backward pump combiner (5), and the low-reflectivity fiber grating (8) arranged in sequence. The forward pump combiner (2) and the backward pump combiner (5) each include a plurality of pump modules (6). The pump modules (6) are driven by the pump source driving power supply (7). The pump source driving power supply (7) is used to control the power of the pump modules (6) and the timing of the pump laser. The fiber output end (9) is connected to the low reflectivity fiber grating (8). The power transmission fiber (4) is located between the gain fiber (3) and the back pump combiner (5). The power transmission fiber (4) is connected to the gain fiber (3) and the back pump combiner (5) respectively by fiber fusion splicing to generate stimulated Raman scattering effect. The device is in operation as follows: The pump source driving power supply (7) generates a pulse width driving current to drive the pump module (6) to generate pump light. The pump light is injected into the resonant cavity via the forward pump combiner (2) and the backward pump combiner (5). After the gain fiber (3) absorbs the pump light, it generates quasi-continuous laser under the action of the high reflectivity fiber grating (1) and the low reflectivity fiber grating (8). When the pump power exceeds the second threshold, stimulated Raman scattering is generated in the resonant cavity, thereby adjusting the Q value in the resonant cavity. The laser operating mode changes from the quasi-continuous laser state to the Q-switched state, thereby obtaining a pulsed laser output with high peak power; the Q value is the quality factor of the resonant cavity.

2. The high peak power, high energy pulsed laser generating device according to claim 1, characterized in that: The gain fiber (3) is either a fiber with a uniform core-cladding size along the longitudinal direction or a fiber with a varying core-cladding size along the longitudinal direction; and The gain fiber (3) is a rare earth ion-doped fiber, and the rare earth ions include ytterbium ions, erbium ions, thulium ions, and holmium ions.

3. The high peak power, high energy pulsed laser generating device according to claim 1, characterized in that: The power transmission fiber (4) is a non-rare earth doped fiber, and the core cladding size of its connection end is the same as the parameters of the connection end of the gain fiber (3), and is also the same as the parameters of the connection end of the backward pump combiner (5). The fiber (4) is either a fiber with a uniform core-cladding size along the longitudinal direction or a fiber with a varying core-cladding size along the longitudinal direction at other locations besides the connection end. The length of the power transmission fiber (4) is controlled according to the design power and Raman threshold, and the length range is 3-30 meters.

4. The high peak power, high energy pulsed laser generating device according to claim 1, characterized in that: The center wavelength of the high reflectivity fiber grating (1) is located within the gain bandwidth of the gain fiber (3). The reflectivity of the high reflectivity fiber grating (1) is greater than 95%, the reflection bandwidth is >1nm, and its core and cladding diameters are the same as those of the connection end of the gain fiber (3).

5. The high peak power, high energy pulsed laser generating device according to claim 1, characterized in that: The center wavelength of the low reflectivity fiber grating (8) is the same as that of the high reflectivity fiber grating (1). The reflectivity of the low reflectivity fiber grating (8) is 4%-50%, and the reflection bandwidth is >0.1nm. Its core and cladding diameters are the same as those of the connection end of the gain fiber (3).

6. The high peak power, high energy pulsed laser generating device according to claim 1, characterized in that: The forward pump combiner (2) includes a signal end, a pump end and an output end. The fiber core diameter of the signal end of the forward pump combiner (2) is the same as the fiber core diameter of the high reflectivity fiber grating (1). The fiber core and cladding diameters of the output end of the forward pump combiner (2) are the same as the fiber core and cladding diameters of the gain fiber (3).

7. The high peak power, high energy pulsed laser generating device according to claim 1, characterized in that: The backward pump combiner (5) includes a signal end, a pump end and an output end. The fiber core diameter of the signal end of the backward pump combiner (5) is the same as the core and cladding diameter of the gain fiber (3). The fiber core diameter of the output end of the backward pump combiner (5) is the same as the core diameter of the low reflectivity fiber grating (8).

8. The high peak power, high energy pulsed laser generating device according to claim 1, characterized in that: The pump module (6) is connected to the optical fibers at the pump ends of the forward pump combiner (2) and the backward pump combiner (5), respectively. The optical fibers at the pump ends of the forward pump combiner (2) and the backward pump combiner (5) have the same optical fiber size. The center wavelength of the pump module (6) is located within the absorption band of the gain fiber (3) and at a wavelength position where the wavelength absorption exceeds the first threshold. The pump source drive power supply (7) is a DC power supply used to control the output current and output power of the pump module (6). The pump source drive power supply (7) is a continuous output current or a pulse modulation output. The modulation current pulse has a controllable pulse width and a controllable repetition frequency.

9. A high peak power, high energy pulsed laser generating device according to claim 1, characterized in that: The optical fiber output end (9) includes a cladding optical filter and an optical fiber output end cap. The fiber core diameter and numerical aperture of the optical fiber used in the optical fiber output end (9) are not less than the size used in the backward pump combiner (5).

10. A method for generating high peak power high energy pulsed laser, the method being based on a laser generating device to generate the high peak power high energy pulsed laser; characterized in that: The laser generating device includes: a high reflectivity fiber grating (1), a forward pump combiner (2), a gain fiber (3), a power transfer fiber (4), a backward pump combiner (5), a pump module (6), a pump source drive power supply (7), a low reflectivity fiber grating (8), and an optical fiber output end (9). The fiber oscillator is composed of an all-fiber structure, consisting of the high-reflectivity fiber grating (1), the forward pump combiner (2), the gain fiber (3), the backward pump combiner (5), and the low-reflectivity fiber grating (8) arranged in sequence. The forward pump combiner (2) and the backward pump combiner (5) each include a plurality of pump modules (6). The pump modules (6) are driven by the pump source driving power supply (7). The pump source driving power supply (7) is used to control the power of the pump modules (6) and the timing of the pump laser. The fiber output end (9) is connected to the low reflectivity fiber grating (8). The power transmission fiber (4) is located between the gain fiber (3) and the back pump combiner (5). The power transmission fiber (4) is connected to the gain fiber (3) and the back pump combiner (5) respectively by fiber fusion splicing to generate stimulated Raman scattering effect. The method specifically includes: The pump source driving power supply (7) generates a pulse width driving current to drive the pump module (6) to generate pump light. The pump light is injected into the resonant cavity via the forward pump combiner (2) and the backward pump combiner (5). After the gain fiber (3) absorbs the pump light, it generates quasi-continuous laser under the action of the high reflectivity fiber grating (1) and the low reflectivity fiber grating (8). When the pump power exceeds the second threshold, stimulated Raman scattering is generated in the resonant cavity, thereby adjusting the Q value in the resonant cavity. The laser operating mode changes from the quasi-continuous laser state to the Q-switched state, thereby obtaining a pulsed laser output with high peak power; the Q value is the quality factor of the resonant cavity.

Images