Fiber laser pulse train generation module and fiber laser

Abstract

The present application discloses a fiber laser pulse train generation module and a fiber laser, which firstly adjusts the repetition frequency of the optical pulse signal emitted by the fiber laser seed source to a preset repetition frequency through a pulse selector, and then, through a pulse train generator, multi-stage splits the optical pulse signal to generate a pulse train with multiple sub-pulses, thereby reducing the energy of a single pulse, thereby reducing the nonlinear effect of the optical fiber and improving the transmission performance of the fiber laser beam. In addition, especially when the seed source repetition frequency is low and the number of sub-pulses in the pulse train is small, the pulse train generation is more convenient and effective because the repetition frequency needs to be reduced first and the number of sub-pulses is multiplied.

Description

Technical Field

[0001] The present application relates to the field of fiber laser pulse technology, and in particular to a fiber laser pulse train generation module and a fiber laser using the module. Background Art

[0002] At present, the pulse repetition frequency of general fiber laser seed sources is in the range of 10 to 40 MHz, while the frequency of a relatively effective ultrashort laser pulse signal train must reach a level of 1 to 10 GHz or above. In order to obtain a pulse train with such a high frequency, a pulse train generation module is required to split or copy each pulse.

[0003] In the prior art, the pulse train generation module is usually implemented as follows Figure 1 The basic method of the pulse train generation module shown is to evenly multiply the repetition frequency of the seed source signal step by step using the principle of pulse splitting, that is, if the repetition frequency of the seed source signal is 100Hz, the first step is to change the repetition frequency to 200Hz, and then multiply it to 400Hz, and so on. After the repetition frequency is multiplied to the required level, a pulse selector is used to select the required pulse train and then amplify it. Although it can have a higher efficiency for longer pulse trains, even when spanning two seed source signal pulses, it is limited in that the frequency within the pulse train can only be 2N times the seed source signal frequency. However, when the number of sub-pulses contained in the pulse train is not large (such as within a few dozen), this method makes it inflexible to reduce the energy of a single pulse, and the higher the energy of a single pulse, the higher the output high-energy pulse will increase the fiber nonlinear effect and affect the transmission of the fiber laser beam. Summary of the invention

[0004] The present application provides a fiber laser pulse train generation module and a fiber laser thereof, which are used to solve the technical problem in the prior art that reducing the energy of a single fiber pulse is not flexible enough.

[0005] In view of this, the first aspect of the present application provides a fiber laser pulse train generation module, comprising: a pulse selector and a pulse train generator arranged in sequence;

[0006] The pulse selector is used to receive the optical pulse signal output by the fiber laser seed source, and to obtain and output the optical pulse signal with a preset repetition frequency by adjusting the switching period of the pulse selector;

[0007] The pulse train generator includes m-level 2×2 beam splitters (m=1, 2, 3...M) and n-level delay optical fibers (n=1, 2, 3...N), wherein one input end of the first-level 2×2 beam splitter is connected to the output end of the pulse selector, for receiving the optical pulse signal output by the pulse selector and then performing the first beam splitting, one output end of the first-level 2×2 beam splitter is connected to one input end of the second-level 2×2 beam splitter through an optical fiber, the other output end of the first-level 2×2 beam splitter is connected to the other input end of the second-level 2×2 beam splitter through a first-level delay optical fiber, one output end of the second-level 2×2 beam splitter is connected to one input end of the third-level 2×2 beam splitter through an optical fiber, the other output end of the second-level 2×2 beam splitter is connected to the other input end of the third-level 2×2 beam splitter through a second-level delay optical fiber, and so on, until one output end of the last-level 2×2 beam splitter outputs an optical pulse signal, wherein the length of the n+1th-level delay optical fiber is twice that of the nth-level delay optical fiber.

[0008] Preferably, the other output end of the last stage 2×2 beam splitter is connected to a first idle optical fiber, and the first idle optical fiber is connected to a power meter for measuring the average power of the optical pulse signal output by the last stage 2×2 beam splitter.

[0009] Preferably, the other input end of the first-stage 2×2 beam splitter is connected to a second idle optical fiber.

[0010] Preferably, it further comprises a first preamplifier, which is connected to the input end of the pulse selector and is used to receive and amplify the optical pulse signal output by the fiber laser seed source.

[0011] Preferably, it further comprises a second preamplifier, which is connected to the output end of the last stage 2×2 beam splitter, and is used for receiving and amplifying the optical pulse signal.

[0012] Preferably, the second preamplifier comprises a fiber circulator, a gain fiber, a fiber grating and a pump laser source;

[0013] The optical fiber circulator is provided with an input end, a first output end and a second output end, and the input end of the optical fiber circulator is connected to the output end of the last stage 2×2 beam splitter, and is used to receive the optical pulse signal output by the last stage 2×2 beam splitter;

[0014] The gain optical fiber is connected to the first output end of the optical fiber circulator, and is used to perform gain amplification on the optical pulse signal when the optical pulse signal passes through the gain optical fiber for the first time;

[0015] The pump laser source is connected to the gain optical fiber, and the pump laser source is used to generate pump light and output it to the optical fiber circulator through the gain optical fiber;

[0016] The fiber Bragg grating is connected to the gain optical fiber, and the fiber Bragg grating is used to reflect the optical pulse signal whose wavelength meets the fiber Bragg grating condition and transmit the optical pulse signal of other wavelengths. At the same time, the optical pulse signal reflected by the fiber Bragg grating is again amplified by the gain optical fiber;

[0017] The second output end of the optical fiber circulator is used to output the optical pulse signal after the gain amplification by the gain optical fiber and the pump light.

[0018] On the other hand, the present application also provides a fiber laser, comprising the above-mentioned fiber laser pulse train generating module.

[0019] It can be seen from the above technical solutions that the embodiments of the present application have the following advantages:

[0020] The embodiment of the present application provides a fiber laser pulse train generation module, including a pulse selector and a pulse train generator arranged in sequence, which first adjusts the repetition frequency of the optical pulse signal emitted by the fiber laser seed source to a preset repetition frequency through the pulse selector, and then, through the pulse train generator, the optical pulse signal is multi-stage split to generate a pulse train with multiple sub-pulses, so that the energy of a single pulse is reduced, thereby reducing the nonlinear effect of the optical fiber and improving the transmission performance of the fiber laser beam. In addition, especially when the repetition frequency of the seed source is low and the number of sub-pulses in the pulse train is small, the pulse train generation is more convenient and effective because it is necessary to first reduce the repetition frequency and adopt a method of doubling the number of sub-pulses. A fiber laser provided in another embodiment of the present application uses the above-mentioned fiber laser pulse train generation module and has the same beneficial effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of the structure of a fiber laser pulse train generation module in the prior art of this application;

[0022] Figure 2 A schematic diagram of the structure of a fiber laser pulse train generation module provided in an embodiment of the present application;

[0023] Figure 3 A schematic structural diagram of a pulse train generator of a fiber laser pulse train generating module provided in an embodiment of the present application;

[0024] Figure 4 A schematic structural diagram of a second preamplifier of a fiber laser pulse train generating module provided in an embodiment of the present application. DETAILED DESCRIPTION

[0025] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0026] For easier understanding, see Figure 2 , the present application provides a fiber laser pulse train generation module, comprising: a pulse selector and a pulse train generator arranged in sequence;

[0027] Furthermore, the pulse selector is used to receive the optical pulse signal output by the fiber laser seed source, and to obtain and output the optical pulse signal with a preset repetition frequency by adjusting the switching cycle of the pulse selector;

[0028] It should be noted that the average power of a fiber laser is equal to the product of the pulse energy and the pulse repetition frequency. When the average power of the laser is limited, the pulse energy can only be increased by reducing the repetition frequency. The switching cycle of the pulse selector in this embodiment is adjustable, and the repetition frequency of the optical pulse signal can be adjusted to a preset repetition frequency through the switching cycle of the pulse selector, and the preset repetition frequency is set according to the customer's process requirements.

[0029] Furthermore, the pulse train generator includes m-level 2×2 beam splitters (m=1, 2, 3...M) and n-level delay optical fibers (n=1, 2, 3...N), wherein one input end of the first-level 2×2 beam splitter is connected to the output end of the pulse selector, for receiving the optical pulse signal output by the pulse selector and then performing the first beam splitting, one output end of the first-level 2×2 beam splitter is connected to one input end of the second-level 2×2 beam splitter through optical fiber, the other output end of the first-level 2×2 beam splitter is connected to another input end of the second-level 2×2 beam splitter through the first-level delay optical fiber, one output end of the second-level 2×2 beam splitter is connected to one input end of the third-level 2×2 beam splitter through optical fiber, the other output end of the second-level 2×2 beam splitter is connected to another input end of the third-level 2×2 beam splitter through the second-level delay optical fiber, and so on, until one output end of the last-level 2×2 beam splitter outputs the optical pulse signal, wherein the length of the n+1th-level delay optical fiber is twice that of the nth-level delay optical fiber.

[0030] It should be noted that each level of 2×2 beam splitter is defined as the mth level 2×2 beam splitter, and each level of delay fiber is defined as the nth level delay fiber. The optical pulse signal can be split by the 2×2 beam splitter, and one end is transmitted to the next level 2×2 beam splitter through ordinary optical fiber, and the other end is transmitted to the next level 2×2 beam splitter through delay optical fiber, and the length of the n+1th level delay optical fiber is twice that of the nth level delay optical fiber, so that 2n sub-pulses are generated when transmitted to the next level 2×2 beam splitter until the sub-pulses in the pulse train reach the predetermined number of sub-pulses, and the predetermined number of sub-pulses is related to the carrying performance of the optical fiber itself, and the carrying performance of the optical fiber itself is related to the diameter of the optical fiber. Finally, after reaching the predetermined number of sub-pulses, the energy of the single pulse is reduced, thereby reducing the nonlinear effect of the optical fiber and improving the transmission performance of the optical fiber.

[0031] In addition, the pulse train generator in this embodiment makes it possible to generate a pulse train within the repetition frequency of any number of sub-pulses, especially when the seed source repetition frequency is low and the number of sub-pulses required in the pulse train is small. Since it is necessary to reduce the repetition frequency and multiply the number of sub-pulses, the pulse train generation is more convenient and effective.

[0032] In another specific embodiment, referring to Figure 3 , the pulse train generator uses 5 levels of 2×2 beam splitters 11, 12, 13, 14, 15, and one of the output ends between each level of 2×2 beam splitters is connected to one input end through optical fiber 3, and the other output end is connected to the other input end through delay optical fiber 21, 22, 23, 24, and the delay optical fiber 21, 22, 23, 24 is provided with 4 levels of delay optical fiber, and at the same time, the length of the delay optical fiber 21, 22, 23, 24 is extended by twice the length of the delay optical fiber of the previous level according to the increase of the level. Finally, a pulse is output at one of the output ends of the 5th level 2×2 beam splitter 15, so that the mother pulse entering the 1st level 2×2 beam splitter 11 is split four times, and a total of 16 sub-pulses are separated, thereby reducing the energy of a single pulse.

[0033] Furthermore, the other output end of the last stage 2×2 beam splitter is connected to a first idle optical fiber 41, and the first idle optical fiber 41 is connected to a power meter for measuring the average power of the optical pulse signal output by the last stage 2×2 beam splitter.

[0034] Furthermore, the other input end of the first-stage 2×2 beam splitter is connected to a second idle optical fiber 40 .

[0035] Furthermore, the fiber laser pulse train generation module also includes a first preamplifier, which is connected to the input end of the pulse selector and is used to receive and amplify the optical pulse signal output by the fiber laser seed source.

[0036] Furthermore, the fiber laser pulse train generation module also includes a second preamplifier, which is connected to the output end of the last stage 2×2 beam splitter and is used to receive and amplify the optical pulse signal.

[0037] It should be noted that the pulse train generator is actually generated by splitting the mother pulse (initial pulse) through a multi-stage 2×2 beam splitter and a multi-stage delay optical fiber. Therefore, the energy of each sub-pulse will continue to decrease. At the same time, since the input optical pulse signal is divided into two signal lights, at least half of the power will be lost. Furthermore, each component will cause loss of the optical pulse signal. Therefore, the signal strength of the pulse train finally generated is much lower. Therefore, in this embodiment, a second preamplifier is used to amplify the optical pulse signal output by the last stage 2×2 beam splitter.

[0038] Further, refer to Figure 4 , the second preamplifier specifically includes a fiber circulator 5, a gain fiber 6, a fiber grating 7 and a pump laser source 8;

[0039] The optical fiber circulator 5 is provided with an input end 51, a first output end 52 and a second output end 53. The input end 51 of the optical fiber circulator 5 is connected to the output end of the last stage 2×2 beam splitter, and is used to receive the optical pulse signal output by the last stage 2×2 beam splitter.

[0040] The gain optical fiber 6 is connected to the first output end 52 of the optical fiber circulator 5, and is used to amplify the gain of the optical pulse signal when the optical pulse signal passes through the gain optical fiber 6 for the first time;

[0041] The pump laser source 8 is connected to the gain optical fiber 6, and the pump laser source 8 is used to generate pump light and output it to the optical fiber circulator 5 through the gain optical fiber 6;

[0042] The fiber Bragg grating 7 is connected to the gain fiber 6. The fiber Bragg grating 7 is used to reflect the optical pulse signal whose wavelength meets the fiber Bragg grating condition and transmit the optical pulse signal of other wavelengths. At the same time, the optical pulse signal reflected by the fiber Bragg grating 7 is again amplified by the gain fiber 6.

[0043] The second output end 53 of the optical fiber circulator 5 is used to output the optical pulse signal and the pump light after being gain-amplified again by the gain optical fiber 6 .

[0044] It should be noted that the specific working process of the optical pulse signal entering the second preamplifier for gain amplification is that after the optical pulse signal enters from the input end 51 of the optical fiber circulator 5, it passes through the first output end 52 and is amplified for the first time by the gain optical fiber 6. Then, the optical pulse signal after the first amplification enters the fiber grating 7. The fiber grating 7 transmits the optical pulse signal whose wavelength does not meet the fiber Bragg grating condition, so that the ASE signal in other wavelength regions is filtered out, and the optical pulse signal whose wavelength meets the fiber Bragg grating condition is reflected. The reflected optical pulse signal passes through the gain optical fiber 6 again to achieve the second gain amplification, and finally, it is output from the second output end 53. Thereby, the ASE signal can be effectively printed, and the signal-to-noise ratio of the optical pulse signal is improved. In addition, the pump light generated by the pump laser source 8 is synthesized and output with the optical pulse signal to achieve the amplification of the optical pulse signal.

[0045] The above embodiment provides a fiber laser pulse train generating module, and in another embodiment, a fiber laser is further provided, including the above fiber laser pulse train generating module.

[0046] In the several embodiments provided in the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0047] As described above, the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A fiber laser pulse train generation module, characterized in that: include: A pulse selector and a pulse train generator are arranged in sequence; The pulse selector is used to receive the optical pulse signal output by the fiber laser seed source, and to obtain and output the optical pulse signal with a preset repetition frequency by adjusting the switching period of the pulse selector; The pulse train generator includes m-level 2×2 beam splitters (m=1, 2, 3...M) and n-level delay optical fibers (n=1, 2, 3...N), wherein one input end of the first-level 2×2 beam splitter is connected to the output end of the pulse selector, for receiving the optical pulse signal output by the pulse selector and then performing the first beam splitting, one output end of the first-level 2×2 beam splitter is connected to one input end of the second-level 2×2 beam splitter through an optical fiber, the other output end of the first-level 2×2 beam splitter is connected to the other input end of the second-level 2×2 beam splitter through a first-level delay optical fiber, one output end of the second-level 2×2 beam splitter is connected to one input end of the third-level 2×2 beam splitter through an optical fiber, the other output end of the second-level 2×2 beam splitter is connected to the other input end of the third-level 2×2 beam splitter through a second-level delay optical fiber, and so on, until one output end of the last-level 2×2 beam splitter outputs an optical pulse signal, wherein the length of the n+1th-level delay optical fiber is twice that of the nth-level delay optical fiber.

2. The fiber laser pulse train generation module according to claim 1, characterized in that: The other output end of the last stage 2×2 beam splitter is connected to a first idle optical fiber, and the first idle optical fiber is connected to a power device for measuring the average power of the optical pulse signal output by the last stage 2×2 beam splitter.

3. The fiber laser pulse train generation module according to claim 2, characterized in that: The other input end of the first-stage 2×2 beam splitter is connected to a second idle optical fiber.

4. The fiber laser pulse train generation module according to claim 1, characterized in that: It also includes a first preamplifier, which is connected to the input end of the pulse selector and is used to receive and amplify the optical pulse signal output by the fiber laser seed source.

5. The fiber laser pulse train generation module according to claim 1 or 4, characterized in that: It also includes a second preamplifier, which is connected to the output end of the last stage 2×2 beam splitter and is used to receive and amplify the optical pulse signal output by the last stage 2×2 beam splitter.

6. The fiber laser pulse train generation module according to claim 5, characterized in that: The second preamplifier includes a fiber circulator, a gain fiber, a fiber grating and a pump laser source; The optical fiber circulator is provided with an input end, a first output end and a second output end, and the input end of the optical fiber circulator is connected to the output end of the last stage 2×2 beam splitter, and is used to receive the optical pulse signal output by the last stage 2×2 beam splitter; The gain optical fiber is connected to the first output end of the optical fiber circulator, and is used to perform gain amplification on the optical pulse signal when the optical pulse signal passes through the gain optical fiber for the first time; The pump laser source is connected to the gain optical fiber, and the pump laser source is used to generate pump light and output it to the optical fiber circulator through the gain optical fiber; The fiber Bragg grating is connected to the gain optical fiber, and the fiber Bragg grating is used to reflect the optical pulse signal whose wavelength meets the fiber Bragg grating condition and transmit the optical pulse signal of other wavelengths. At the same time, the optical pulse signal reflected by the fiber Bragg grating is again amplified by the gain optical fiber; The second output end of the optical fiber circulator is used to output the optical pulse signal after the gain amplification by the gain optical fiber and the pump light.

7. A fiber laser, characterized in that: The invention comprises a fiber laser pulse train generating module as claimed in any one of claims 1 to 6.

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