Pulse ns-level adjustable MOPA fiber laser based on acousto-optic modulator

Abstract

The utility model provides a pulse ns level adjustable MOPA fiber laser based on an acousto-optic modulator, the laser sequentially comprises a seed laser module, an acousto-optic ns level adjustable module and a cascade fiber amplification module, the seed laser module is used for generating pulse laser signals, the seed laser module comprises a seed laser and a first isolator, and the seed laser is used for generating pulse laser signals. The acousto-optic ns-level adjustable module is used for realizing ns-level adjustability of the pulse width of the pulse laser signal, the acousto-optic ns-level adjustable module comprises an acousto-optic ns-level adjustable unit and a pulse interval adjusting unit, the cascade optical fiber amplification module is used for performing power amplification on the pulse laser signal after the pulse width is adjusted, and the cascade optical fiber amplification module comprises a multi-level amplification unit. According to the laser, through sequential control of an acousto-optic modulator in the acousto-optic ns-level adjustable module, ns-level adjustability of the pulse width of a traditional MOPA optical fiber laser is achieved, pulses are output in a sub-pulse mode, the pulse duty ratio is effectively reduced, and ns-level adjustable high-peak-power stable laser output is obtained.

Description

Technical Field

[0001] The utility model relates to the technical field of laser pulse signal control, in particular to a pulsed ns-level adjustable MOPA fiber laser based on an acousto-optic modulator. Background Art

[0002] MOPA fiber lasers have been widely used in marking, drilling, cleaning, cutting, welding, ablation and other fields due to their low noise, good beam quality, high peak power, flexible parameter adjustment, and easy integration. With the further increase in power, MOPA pulse fiber lasers will also be more widely used in power battery and photovoltaic power generation fields such as tab cutting, pole piece cutting, battery module disassembly, and perovskite scribing.

[0003] With the deepening of MOPA fiber laser applications in the field of industrial processing, a higher peak value can make the material vaporize instantly, so that the thermal effect can be smaller in the processing technology, it is not easy to produce melt beads, the heat affected zone and burrs of the material are reduced, the processing efficiency is higher and the effect is better. Therefore, improving the peak power of MOPA fiber lasers has become an inevitable development trend in the field of industrial processing.

[0004] Peak power is equal to pulse energy divided by pulse width. Therefore, under the same energy conditions, shortening the pulse width can greatly increase the peak power. Under the same pulse width conditions, the pulse energy needs to be greatly increased. At a certain repetition frequency, increasing the pulse energy means adding more amplifier stages to increase the output power, which greatly increases the cost. When the output power is higher than a certain threshold, the output beam mode will show transverse mode instability. Continuing to increase the pump power will reduce the output power and the beam quality of the output laser, and also bring a great load to the amplifier, affecting the long-term stability and service life of the laser system. In addition, the pulse width of the seed laser is limited by the speed of circuit modulation and cannot be narrower. The narrowest pulse width can currently reach 1ns, and 1ns is transmitted and amplified in the optical fiber. There will be strong nonlinear effects in the process. Excessive nonlinearity will lead to adverse phenomena such as self-phase modulation, cross-phase modulation, modulation instability, four-wave mixing, self-focusing, stimulated Brillouin scattering and stimulated Raman scattering. Therefore, the pulse width of the common MOPA fiber laser is generally above 10ns. For the current MOPA fiber laser, in order to achieve high peak power output, the general method is to use the seed laser electrical modulation plus multi-stage fiber amplification structure. Taking the seed pulse width of 10ns as an example, if the conventional three-stage amplification structure is used, at a repetition frequency of 100kHz, the final output is 20W, and the peak power is 20kW. Therefore, it is very difficult to increase the peak power by reducing the pulse width, and due to hardware constraints, the existing MOPA fiber laser cannot achieve ns-level adjustable pulse width. Utility Model Content

[0005] The purpose of the utility model is to provide a MOPA fiber laser with adjustable pulse width at the nanosecond level based on an acousto-optic modulator, so as to solve the shortcomings of the prior art and achieve high peak power laser output with adjustable pulse width at the nanosecond level. The specific technical solution of the utility model is as follows:

[0006] A pulsed ns-level adjustable MOPA fiber laser based on an acousto-optic modulator, the laser comprising a seed laser module, an acousto-optic ns-level adjustable module and a cascade fiber amplification module, the output end of the seed laser module is connected to the input end of the acousto-optic ns-level adjustable module, the output end of the acousto-optic ns-level adjustable module is connected to the input end of the cascade fiber amplification module, the acousto-optic ns-level adjustable module comprises an acousto-optic ns-level adjustable unit and a pulse interval adjustment unit, and the cascade fiber amplification module comprises a multi-stage amplification unit.

[0007] Further, the acousto-optic ns-level adjustable unit includes a first acousto-optic modulator, a 50:50 coupler connected to the output end of the first acousto-optic modulator, a second acousto-optic modulator connected to the side end of the input end of the 50:50 coupler, a circulator connected to the side end of the output end of the 50:50 coupler, a first gain fiber connected to two ends of the circulator, a wavelength division multiplexer connected to the output end of the first gain fiber, a single-mode pump protector connected to the input end of the wavelength division multiplexer, a single-mode pump laser connected to the input end of the single-mode pump protector, and a third acousto-optic modulator connected to the output end of the 50:50 coupler; one end of the circulator is connected to the side end of the output end of the 50:50 coupler, and the three ends of the circulator are connected to the input end of the second acousto-optic modulator.

[0008] Furthermore, the pulse interval adjustment unit includes a 0-degree reflector and a fine-adjustment stepper motor platform, and the 0-degree reflector is installed above the fine-adjustment stepper motor platform and is arranged opposite to the output end of the wavelength division multiplexer.

[0009] Furthermore, the seed laser module includes a seed laser and a first isolator connected to an output end of the seed laser, and the output end of the first isolator is connected to an input end of the first acousto-optic modulator.

[0010] Furthermore, the cascaded optical fiber amplification module includes a first-stage pre-amplification unit, a second-stage power amplification unit and a third-stage power amplification unit.

[0011] Furthermore, the first-stage pre-amplification unit includes a first semiconductor pump laser group, a first combiner connected to the output ends of the first semiconductor pump laser group and the third acousto-optic modulator, a second gain fiber connected to the output end of the first combiner, and a second isolator connected to the output end of the second gain fiber.

[0012] Furthermore, the second-stage power amplification unit includes a second semiconductor pump laser group, a second combiner connected to the second semiconductor pump laser group and the output end of the second isolator, a third gain fiber connected to the output end of the second combiner, and a third isolator connected to the output end of the third gain fiber.

[0013] Furthermore, the third-stage power amplification unit includes a third semiconductor pump laser group, a third combiner connected to the third semiconductor pump laser group and the output end of the third isolator, a fourth gain fiber connected to the output end of the third combiner, and an output collimating isolator connected to the output end of the fourth gain fiber.

[0014] Furthermore, the seed laser is a DFB semiconductor laser, a solid laser or a mode-locked fiber laser.

[0015] Furthermore, the laser medium of the first semiconductor pump laser group, the second semiconductor pump laser group and the third semiconductor pump laser group is at least one of Nd:YAG, Nd:YVO4 or Yb:YAG.

[0016] The utility model provides a pulsed ns-level adjustable MOPA fiber laser based on an acousto-optic modulator, which has the following beneficial effects:

[0017] The utility model provides a pulsed MOPA fiber laser with ns-level adjustable pulses based on an acousto-optic modulator. Through the timing control of the acousto-optic modulator, the pulse width of a traditional MOPA laser can be adjusted to the ns level, and the pulse is output in the form of a sub-pulse, which effectively reduces the pulse duty cycle and can obtain a stable laser output with ns-level adjustable high peak power. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the structure of a pulsed ns-level adjustable MOPA fiber laser based on an acousto-optic modulator provided in an embodiment of the utility model;

[0019] Figure 2 It is a partial schematic diagram of a pulsed ns-level adjustable MOPA fiber laser based on an acousto-optic modulator provided by an embodiment of the utility model;

[0020] Figure 3It is a schematic diagram of the timing and output pulse of the acousto-optic modulator in the embodiment of the utility model;

[0021] Figure 4 It is a schematic diagram of light pulses provided by an embodiment of the utility model. DETAILED DESCRIPTION

[0022] The following will be combined with the accompanying drawings provided by the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. According to the following description, the advantages and features of the utility model will be clearer. It should be noted that the drawings are all in a very simplified form and are not in precise proportions, which are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the utility model.

[0023] In the description of the present invention, unless otherwise clearly specified and limited, the terms "connection" and "connected" should be interpreted in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integrated connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0024] In the description of the present invention, terms such as "upper", "lower", "left", "right", "front", "back", "center", "horizontal", "vertical", "top", "bottom", "inside" and "outside" and other orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of description and simplification of operation, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0025] Example:

[0026] See also Figures 1-2 As shown, this embodiment provides a pulsed ns-level adjustable MOPA fiber laser based on an acousto-optic modulator, the laser comprising a seed laser module, an acousto-optic ns-level adjustable module and a cascade fiber amplifier module, the output end of the seed laser module is connected to the input end of the acousto-optic ns-level adjustable module, and the output end of the acousto-optic ns-level adjustable module is connected to the input end of the cascade fiber amplifier module. The seed laser module is used to generate a pulsed laser signal, the acousto-optic ns-level adjustable module is used to achieve ns-level adjustment of the pulse width of the pulsed laser signal, and the cascade fiber amplifier module is used to power amplify the pulsed laser signal after adjusting the pulse width.

[0027] The utility model provides a pulsed MOPA fiber laser based on an acousto-optic modulator with ns-level adjustable pulses. The pulse width of a conventional MOPA fiber laser can be adjusted to the ns-level through the timing control of the acousto-optic modulator, and the pulse is output in the form of a sub-pulse, thereby effectively reducing the pulse duty cycle and obtaining a stable laser output with ns-level adjustable high peak power.

[0028] This embodiment provides a specific implementation of the seed laser module. Figure 1 As shown, the seed laser module includes a seed laser 1 and a first isolator 2 fused to the output end of the seed laser 1. The seed laser 1 is used to generate a pulse laser signal, and the pulse laser signal is output to the acousto-optic ns-level adjustable module 3 through the first isolator 2.

[0029] Optionally, the seed laser 1 is a DFB semiconductor laser, a solid laser or a mode-locked fiber laser.

[0030] This embodiment provides a specific implementation of the acousto-optic ns-level adjustable module 3, see Figure 2 As shown, the acousto-optic ns-level adjustable module 3 includes an acousto-optic ns-level adjustable unit and a pulse interval adjustment unit. The acousto-optic ns-level adjustable unit includes a first acousto-optic modulator 31, a 50:50 coupler 32, a second acousto-optic modulator 33, a circulator 34, a first gain fiber 35, a wavelength division multiplexer 36, a single-mode pump protector 37, a single-mode pump laser 38 and a third acousto-optic modulator 39. The input end of the first acousto-optic modulator 31 is fused to the output end of the first isolator 2, the output end of the first acousto-optic modulator 31 is fused to the a end of the 50:50 coupler 32, the b end of the 50:50 coupler is fused to the output end of the second acousto-optic modulator 33, the input end of the second acousto-optic modulator 33 is fused to the 3 end of the circulator 34, the d end of the 50:50 coupler 32 is fused to the 1 end of the circulator 34, the 2 end of the circulator 34 is fused to the first gain fiber 35, the first gain fiber 35 is fused to the input end of the wavelength division multiplexer 36, the output end of the single-mode pump laser 38 is fused to the input end of the single-mode pump protector 37, the output end of the single-mode pump protector 37 is fused to the input end of the wavelength division multiplexer 36, and the c end of the 50:50 coupler 32 is fused to the third acousto-optic modulator 39.

[0031] The pulse interval adjustment unit 310 includes a 0 degree reflector 311 and a fine adjustment stepper motor platform 312. The pulse interval adjustment unit 310 is arranged at one side of the output end of the wavelength division multiplexer 36, and the 0 degree reflector 311 is installed on the fine adjustment stepper motor platform 312 and arranged opposite to the output end of the wavelength division multiplexer 36.

[0032] Optionally, the wavelength division multiplexer 36 is a two-terminal device that reflects signal light and transmits pump light.

[0033] Among them, the first acousto-optic modulator 31 is used to select the repetition frequency f and the number of pulses n of the laser signal; the second acousto-optic modulator 32 controls the switching gate of the circulating pulses, and controls the number of sub-pulse trains n by adjusting the switching gate delay, thereby finely adjusting the pulse width; the third acousto-optic modulator 39 selects the number of the final stable circulating pulses output, and at the same time divides the frequency selected by the first acousto-optic modulator 31 for output.

[0034] The laser signal of the seed laser 1 enters the first acousto-optic modulator 31 through the first isolator 2. After acousto-optic frequency selection, the repetition frequency of the pulse is f 1 , period t 1 , the number of pulses is n, and the pulse interval is t 0 ,Then the laser signal enters the 50:50 coupler 32, and is divided into two paths along the output of the c end and the d end. The laser signal at the c end passes through the 1 end and the 2 end of the circulator 34, the first gain fiber 35 and the wavelength division multiplexer 36 in turn, and passes through the 1 end, the 2 end, the first gain fiber and the wavelength division multiplexer, and after being reflected by the wavelength division multiplexer 36, it passes through the first gain fiber 35 again, and passes through the 3 end of the circulator 34 and the second acousto-optic modulator 33 in turn, and then returns to the b end of the 50:50 coupler 32. The pump light generated by the single-mode pump laser 38 passes through the pump protector 37 and enters the wavelength division multiplexer. After passing through the wavelength division multiplexer, it is reflected back by the 0-degree reflector 311 to compensate for the loss of the ring loop. The optical path of the ring arm is longer than that of the linear arm by time t. The number of pulses passing through the first time is 1, and after time t 0 After that, the first pulse in the circular arm will fall behind the second pulse time interval t, and the two pulses with a pulse interval of t will enter the 50:50 coupler 32 again, and the first two pulses in the circular arm will fall behind the third pulse time interval t, and so on, until after n*t time, a sub-pulse train with n pulses and a time interval of t will be formed and outputted. The optical path difference can be adjusted by finely adjusting the stepping motor platform 312, and then the sub-pulse duty cycle and pulse train width can be finely adjusted, so as to achieve high peak power and ns-level pulse width adjustment.

[0035] Take the number of 5 sub-pulses as an example to explain the timing of the sound and light and the output of the laser signal in detail, see Figure 3 As shown, the first AOM 31 selects 5 pulses from the seed laser pulses, the opening time and repetition frequency of the second AOM 33 are consistent with the first AOM 31, and the closing time depends on the number of pulses. The pulses form an increasing arrangement with a time interval of the seed period t before entering the third AOM 39, and the third AOM 39 can select a sub-pulse sequence with a final number of 5.

[0036] This embodiment provides a specific implementation of the cascaded optical fiber amplifier module. Figure 1 As shown, the cascade fiber amplifier module includes a first stage pre-amplifier unit, a second stage power amplifier unit, and a third stage power amplifier unit. The first stage pre-amplifier unit includes a first semiconductor pump laser group 4, a first beam combiner 5, a second gain fiber 6, and a second isolator 7. The output end of the first semiconductor pump laser group 4 and the acousto-optic ns-level adjustable module is fused to the input end of the first beam combiner 5, the output end of the first beam combiner 5 is fused to the input end of the second gain fiber 6, and the output end of the second gain fiber 6 is fused to the input end of the second isolator 7; the second stage power amplifier unit includes a second semiconductor pump laser group 8, a second beam combiner 9, a third gain fiber 10, and a third isolator 11. The output ends of the second semiconductor pump laser group 8 and the second isolator 7 are fused. The input end of the second combiner 9 and the output end of the second combiner 9 are fused to the input end of the third gain fiber 10, and the output end of the third gain fiber 10 is fused to the input end of the third isolator 11; the third-stage power amplification unit includes a third semiconductor pump laser group 12, a third combiner 13, a fourth gain fiber 14 and an output collimation isolator 15, the output ends of the third semiconductor pump laser group 12 and the third isolator 11 are fused to the input end of the third combiner 13, the output end of the third combiner 13 is fused to the input end of the fourth gain fiber 14, and the output end of the fourth gain fiber 14 is fused to the input end of the output collimation isolator 15.

[0037] Optionally, the laser medium of the first semiconductor pump laser group 4, the second semiconductor pump laser group 8 and the third semiconductor pump laser group 12 is Nd:YAG, Nd:YVO4 or Yb:YAG or the like.

[0038] The three-stage amplification structure of the cascaded fiber amplifier module can effectively suppress the nonlinear effect without increasing the amplified output power, reduce the pulse duty cycle by using sub-pulses, improve the output peak power of the fiber laser, and achieve ns-level adjustable pulse width.

[0039] See also Figure 4 As shown, a comparison is made between the traditional 10ns pulse laser and the sub-pulse laser train after acousto-optic modulation. It is obvious that under the same pulse width and pulse energy of 10ns, the sub-pulse can reduce the duty cycle, thereby increasing the peak power. Taking the MOPA fiber laser as an example, at a repetition frequency of 100kHz, after three-stage amplification, the final output is 20W. Because the pulse width of the 5 sub-pulses is 1ns, the duty cycle is 50%. According to calculations, the peak power is doubled to 40kW. At the same time, the pulse duration can be adjusted at the ns level by adjusting the number of sub-pulses. By adding the pulse interval adjustment component 310, the optical path difference can be adjusted by the stepper motor, and then the sub-pulse duty cycle and pulse train width can be finely adjusted, thereby achieving high peak power and ns-level pulse width adjustment, which is of great significance to the field of industrial processing.

[0040] Those skilled in the art should understand that the present invention can be implemented in many other specific forms without departing from the spirit and scope of the present invention, and all other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

Claims

1. A pulsed ns-level tunable MOPA fiber laser based on an acousto-optic modulator, characterized in that: The laser comprises a seed laser module, an acousto-optic ns-level adjustable module and a cascade fiber amplification module, wherein the output end of the seed laser module is connected to the input end of the acousto-optic ns-level adjustable module, the output end of the acousto-optic ns-level adjustable module is connected to the input end of the cascade fiber amplification module, the acousto-optic ns-level adjustable module comprises an acousto-optic ns-level adjustable unit and a pulse interval adjustment unit, and the cascade fiber amplification module comprises a multi-stage amplification unit.

2. The pulsed ns-level adjustable MOPA fiber laser based on an acousto-optic modulator according to claim 1, characterized in that: The acousto-optic ns-level adjustable unit comprises a first acousto-optic modulator, a 50:50 coupler connected to the output end of the first acousto-optic modulator, a second acousto-optic modulator connected to the side end of the input end of the 50:50 coupler, a circulator connected to the side end of the output end of the 50:50 coupler, a first gain fiber connected to two ends of the circulator, a wavelength division multiplexer connected to the output end of the first gain fiber, a single-mode pump protector connected to the input end of the wavelength division multiplexer, a single-mode pump laser connected to the input end of the single-mode pump protector, and a third acousto-optic modulator connected to the output end of the 50:50 coupler; one end of the circulator is connected to the side end of the output end of the 50:50 coupler, and the three ends of the circulator are connected to the input end of the second acousto-optic modulator.

3. The pulsed ns-level adjustable MOPA fiber laser based on an acousto-optic modulator according to claim 2, characterized in that: The pulse interval adjustment unit comprises a 0-degree reflector and a fine-adjustment stepper motor platform. The 0-degree reflector is installed above the fine-adjustment stepper motor platform and is arranged opposite to the output end of the wavelength division multiplexer.

4. The pulsed ns-level adjustable MOPA fiber laser based on an acousto-optic modulator according to claim 2, characterized in that: The seed laser module includes a seed laser and a first isolator connected to an output end of the seed laser, and the output end of the first isolator is connected to an input end of the first acousto-optic modulator.

5. The pulsed ns-level adjustable MOPA fiber laser based on an acousto-optic modulator according to claim 2, characterized in that: The cascaded optical fiber amplification module comprises a first stage pre-amplification unit, a second stage power amplification unit and a third stage power amplification unit.

6. The pulsed ns-level tunable MOPA fiber laser based on an acousto-optic modulator according to claim 5, characterized in that: The first-stage pre-amplification unit includes a first semiconductor pump laser group, a first combiner connected to the first semiconductor pump laser group and the output end of the third acousto-optic modulator, a second gain fiber connected to the output end of the first combiner, and a second isolator connected to the output end of the second gain fiber.

7. The pulsed ns-level tunable MOPA fiber laser based on an acousto-optic modulator according to claim 6, characterized in that: The second-stage power amplification unit includes a second semiconductor pump laser group, a second combiner connected to the second semiconductor pump laser group and the output end of the second isolator, a third gain fiber connected to the output end of the second combiner, and a third isolator connected to the output end of the third gain fiber.

8. The pulsed ns-level tunable MOPA fiber laser based on an acousto-optic modulator according to claim 7, characterized in that: The third-stage power amplification unit includes a third semiconductor pump laser group, a third combiner connected to the third semiconductor pump laser group and the output end of the third isolator, a fourth gain fiber connected to the output end of the third combiner, and an output collimating isolator connected to the output end of the fourth gain fiber.

9. The pulsed ns-level tunable MOPA fiber laser based on an acousto-optic modulator according to claim 4, characterized in that: The seed laser is a DFB semiconductor laser, a solid laser or a mode-locked fiber laser.

10. The pulsed ns-level tunable MOPA fiber laser based on an acousto-optic modulator according to claim 8, characterized in that: The laser medium of the first semiconductor pump laser group, the second semiconductor pump laser group and the third semiconductor pump laser group is at least one of Nd:YAG, Nd:YVO4 or Yb:YAG.

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