High-energy and short-period mode-locked pulse fiber laser and transmitting method

Abstract

The invention discloses a high-energy and short-period mode-locked pulse fiber laser and an emission method, and relates to the technical field of lasers, the high-energy and short-period mode-locked pulse fiber laser comprises a high-power isolator, and an erbium-doped mode-locked fiber laser and a thulium-doped fiber amplifier which are respectively arranged at two sides of the high-power isolator, the erbium-doped mode-locked fiber laser is connected with the high-power isolator through a high-nonlinearity optical fiber, the thulium-doped fiber amplifier comprises a first signal pumping beam combiner, a second signal pumping beam combiner, a first pumping source and a second pumping source, the first signal pumping beam combiner is connected with the second signal pumping beam combiner through a thulium-doped optical fiber, and the second pumping source is connected with the erbium-doped mode-locked fiber laser through a thulium-doped optical fiber. The erbium-doped mode-locked fiber laser, the high-power isolator, the first signal pumping beam combiner and the second signal pumping beam combiner are arranged on the same straight line, so that the ultra-wide spectrum is provided, the structure of the laser is simplified, amplification of specific wavelengths with few periods and high energy is realized, diversified application requirements are met, and the application range is widened. And the flexibility and multifunctionality of the laser are improved.

Description

[0001] Field of the method

[0002] The present invention relates to the technical field of lasers, and particularly relates to a mode-locked pulsed fiber laser with high energy and few cycles and an emission method thereof.

[0003] Background method

[0004] As an indispensable tool in modern science and technology and industry, high-energy fiber lasers have shown important applications in fields such as communication, medical treatment, material processing, and scientific research. However, traditional fiber amplifiers have limitations in aspects such as output pulse energy and output pulse width, restricting their applications in high-energy output. Therefore, mode-locked pulsed fiber lasers with high energy, wide spectrum, and few cycles have important research value.

[0005] The emergence of supercontinuum technology provides a new solution for this. It can achieve a wide wavelength coverage range and high tunability, making it an ideal choice for mode-locked pulsed fiber lasers with high energy and few cycles. However, existing fiber amplifiers include erbium-doped fiber amplifiers, thulium-doped fiber amplifiers, Raman fiber amplifiers, etc. Existing fiber amplifiers have low energy utilization efficiency and complex structures, making it difficult to process supercontinuum and achieve high-energy pulse output with few cycles.

[0006] Therefore, a mode-locked pulsed fiber laser with high energy and few cycles and an emission method thereof are provided to solve the above problems. Summary of the invention

[0007] The purpose of the present invention is to provide a mode-locked pulsed fiber laser with high energy and few cycles and an emission method thereof, simplify the structure of the laser, improve the energy utilization efficiency, and finally achieve high-energy and few-cycle mode-locked pulse laser output to solve the problems of low energy utilization efficiency, complex structure, and difficulty in achieving high-energy pulse output with few cycles of traditional fiber amplifiers.

[0008] To achieve the above purpose, the present invention provides a mode-locked pulsed fiber laser with high energy and few cycles, including a high-power isolator and an erbium-doped mode-locked fiber laser and a thulium-doped fiber amplifier respectively arranged on both sides of the high-power isolator. The erbium-doped mode-locked fiber laser is connected to the high-power isolator through a highly nonlinear fiber. The thulium-doped fiber amplifier includes a first signal pump combiner, a second signal pump combiner, a first pump source, and a second pump source. The first pump source is arranged below the first signal pump combiner, the second pump source is arranged below the second signal pump combiner, the first signal pump combiner and the second signal pump combiner are connected through a thulium-doped fiber, and the erbium-doped mode-locked fiber laser, the high-power isolator, the first signal pump combiner, and the second signal pump combiner are arranged on the same straight line.

[0009] Preferably, both the first pump source and the second pump source adopt LD pump sources. The wavelength of the LD pump source is set to 793 nm, and the maximum pump power of the LD pump source is set to 100 W.

[0010] Preferably, the erbium-doped mode-locked fiber laser adopts a high-energy femtosecond erbium-doped mode-locked fiber laser. The central wavelength of the high-energy femtosecond erbium-doped mode-locked fiber laser is set to 1550 nm, the output pulse width is set to 300 fs, the average output power is set to 1 W, the repetition rate is set to 40 MHz, and the single-pulse energy is set to 25 nJ.

[0011] Preferably, the highly nonlinear fiber adopts an M-class highly nonlinear fiber. The nonlinear coefficient of the M-class highly nonlinear fiber is set to 20 W -1 km -1 , the zero-dispersion wavelength of the M-class highly nonlinear fiber is set to 2000 nm, and the length of the M-class highly nonlinear fiber is set to 40 cm.

[0012] Preferably, the central wavelength of the high-power isolator is set to 2 μm, and the bandwidth coverage range is set to 800 nm - 3200 nm to ensure unidirectional transmission.

[0013] Preferably, the core diameter of the thulium-doped fiber is set to 10 μm, and the length of the thulium-doped fiber is set to 1 m.

[0014] Preferably, a method for emitting a high-energy few-cycle mode-locked pulse fiber laser includes the following steps:

[0015] S1: The erbium-doped mode-locked fiber laser utilizes the absorption characteristic of erbium ions for 980-nm light and the emission characteristic for 1550-nm light to output a high-energy pulse signal with a pulse width of 300 fs and a central wavelength of 1550 nm;

[0016] S2: The high-energy pulse signal excites the M-class highly nonlinear fiber. The M-class highly nonlinear fiber utilizes the Raman effect and the self-phase modulation effect to broaden the high-pulse signal into an ultra-broadband continuum. The wavelength coverage range of the ultra-broadband continuum is 800 nm - 3200 nm. The ultra-broadband continuum passes through the high-power isolator and the first signal pump beam combiner and enters the thulium-doped fiber;

[0017] S3: The first pump source and the second pump source emit semiconductor lasers with a wavelength of 793 nm. The first signal pump beam combiner and the second signal pump beam combiner couple the semiconductor lasers into the thulium-doped fiber;

[0018] S4: The semiconductor lasers pump the ultra-broadband continuum in the thulium-doped fiber to output a few-cycle high-energy pulse signal with a central wavelength of 2 μm, an output pulse width less than 20 fs, and a spectral width of several hundred nm.

[0019] Preferably, in step S4, semiconductor laser pumps supercontinuum spectrum in thulium-doped fiber, which specifically includes the following steps:

[0020] S41: Utilize the absorption characteristic of thulium ions in thulium-doped fiber for 793 nm light and the emission characteristic for 2 μm light to amplify the light with a wavelength of 2 μm;

[0021] S42: Utilize the characteristics of low intensity of the supercontinuum spectrum itself and the loss of thulium-doped fiber to loss the light with a wavelength greater than 2 μm and the light with a wavelength less than 2 μm as noise, and filter out the noise.

[0022] Preferably, in step S1, replace the erbium-doped mode-locked fiber laser with a ytterbium-doped mode-locked fiber laser, and the excitation effect on the M-level highly nonlinear fiber remains unchanged.

[0023] Preferably, in step S4, replace the thulium-doped fiber with a holmium-doped fiber or a thulium-holmium co-doped fiber, and the wavelength of the output few-cycle high-energy pulse signal remains unchanged. Replace the thulium-doped fiber with a ytterbium-doped fiber, and the wavelength of the output few-cycle high-energy pulse signal is 1 μm.

[0024] Therefore, the mode-locked pulse fiber laser and emission method with high energy and few cycles adopting the above structure in the present invention have the following beneficial effects:

[0025] (1) Use the supercontinuum spectrum as the seed source, and amplify the light with a specific wavelength by a doped fiber amplifier to achieve high-energy, wide-spectrum, and few-cycle pulse output;

[0026] (2) By changing other types of doped fiber amplifiers, the tunability of the central wavelength can be realized;

[0027] (3) While realizing providing an ultra-wide spectrum and simplifying the laser structure, it meets the diverse application requirements and improves the flexibility and versatility of the laser.

[0028] The method solution of the present invention will be further described in detail below with reference to the drawings and embodiments. Brief Description of the Drawings

[0029] Figure 1 It is a structural diagram of a mode-locked pulse fiber laser with high energy and few cycles of the present invention.

[0030] Wherein: 1. Erbium-doped mode-locked fiber laser; 2. M-level highly nonlinear fiber; 3. High-power isolator; 4. First pump source; 5. Second pump source; 6. First signal pump combiner; 7. Thulium-doped fiber; 8. Second signal pump combiner; 9. Thulium-doped fiber amplifier. Detailed Embodiments

[0031] The method solution of the present invention will be further described below with reference to the drawings and embodiments.

[0032] Unless otherwise defined, the method terms or scientific terms used in the present invention shall have the ordinary meanings understood by those of ordinary skill in the art to which the present invention pertains.

[0033] The terms such as "comprising" or "including" used in the present invention mean that the elements before the term cover the elements listed after the term, and do not exclude the possibility of also covering other elements. The orientation or positional relationship indicated by terms such as "inside", "outside", "above", "below", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be construed as a limitation on the present invention. When the absolute position of the object being described changes, the relative positional relationship may also change accordingly. In the present invention, unless otherwise clearly specified and defined, terms such as "attached" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be directly connected, or indirectly connected through an intermediate medium, and can be the communication inside two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0034] Embodiment

[0035] As Figure 1 As shown, the present invention provides a mode-locked pulsed fiber laser with high energy and few cycles, including a high-power isolator 3, an erbium-doped mode-locked fiber laser 1 and a thulium-doped fiber amplifier 9 respectively arranged on both sides of the high-power isolator 3. The erbium-doped mode-locked fiber laser 1 is connected to the high-power isolator 3 through a highly nonlinear fiber. The thulium-doped fiber amplifier 9 includes a first signal pump combiner 6, a second signal pump combiner 8, a first pump source 4 and a second pump source 5. The first pump source 4 is arranged below the first signal pump combiner 6, and the second pump source 5 is arranged below the second signal pump combiner 8. The first signal pump combiner 6 and the second signal pump combiner 8 are connected through a thulium-doped fiber 7. The erbium-doped mode-locked fiber laser 1, the high-power isolator 3, the first signal pump combiner 6 and the second signal pump combiner 8 are arranged on the same straight line.

[0036] Both the first pump source 4 and the second pump source 5 adopt LD pump sources. The wavelength of the LD pump source is set to 793 nm, and the maximum pump power of the LD pump source is set to 100 W.

[0037] The erbium-doped mode-locked fiber laser 1 uses a high-energy femtosecond erbium-doped mode-locked fiber laser. The high energy can make the Raman effect and self-phase modulation effect stronger, so that the spectral broadening of the pump light of the high-energy femtosecond erbium-doped mode-locked fiber laser passing through the M-level highly nonlinear fiber 2 is more obvious, and finally an ultra-broadband spectrum with a larger wavelength range is obtained, providing a larger wavelength selection range for subsequent wavelength tuning.

[0038] The central wavelength of the high-energy femtosecond erbium-doped mode-locked fiber laser is set to 1550 nm, the output pulse width is set to 300 fs, the average output power is set to 1 W, the repetition rate is set to 40 MHz, and the single-pulse energy is set to 25 nJ. The NPR mode-locking method is adopted, and by adjusting the angle of the vibrating plate and the power of the LD pump source in the high-energy femtosecond erbium-doped mode-locked fiber laser, a high-energy mode-locked pulse output in the order of hundreds of femtoseconds with a central wavelength of 1550 nm is realized.

[0039] To obtain an ultra-broadband spectrum output with a large wavelength range and a flat top, the high-energy femtosecond ultrashort pulses emitted by the erbium-doped fiber laser 1 are used as the pump light and injected into the M-level highly nonlinear fiber 2 with a length of 40 cm and a zero-dispersion wavelength of 2000 nm. Finally, an ultra-broadband spectrum output with a flat top and a wavelength coverage bandwidth of up to 2400 nm is obtained.

[0040] The highly nonlinear fiber uses the M-level highly nonlinear fiber 2, and the nonlinear coefficient of the M-level highly nonlinear fiber 2 is set to 20 W -1 km -1 , the zero-dispersion wavelength of the M-level highly nonlinear fiber 2 is set to 2000 nm, and the length of the M-level highly nonlinear fiber 2 is set to 40 cm.

[0041] The central wavelength of the high-power isolator 3 is set to 2 μm, and the bandwidth coverage range is set to 800 nm - 3200 nm to ensure unidirectional transmission.

[0042] The core diameter of the thulium-doped fiber 7 is set to 10 μm, the length of the thulium-doped fiber 7 is set to 1 m, the absorption peak of the thulium-doped fiber 7 is set to 790 nm - 800 nm, and the emission peak of the thulium-doped fiber 7 is set to 1800 nm - 2100 nm.

[0043] A method for emitting a high-energy few-cycle mode-locked pulse fiber laser includes the following steps:

[0044] S1: The erbium-doped mode-locked fiber laser 1 utilizes the absorption characteristics of erbium ions for 980-nm light and the emission characteristics for 1550-nm light to output a high-energy pulse signal with a pulse width of 300 fs and a central wavelength of 1550 nm;

[0045] S2: The high-energy pulse signal excites the M-level highly nonlinear optical fiber 2. The M-level highly nonlinear optical fiber 2 broadens the high pulse signal into an ultra-continuous spectrum by using the Raman effect and the self-phase modulation effect. The wavelength coverage range of the ultra-continuous spectrum is 800 nm - 3200 nm. The ultra-continuous spectrum passes through the high-power isolator 3 and the first signal-pump beam combiner 6 and enters the thulium-doped fiber 7;

[0046] S3: The first pump source 4 and the second pump source 5 emit semiconductor lasers with a wavelength of 793 nm. The first signal-pump beam combiner 6 and the second signal-pump beam combiner 8 couple the semiconductor lasers into the thulium-doped fiber 7;

[0047] S4: The semiconductor lasers pump the ultra-continuous spectrum in the thulium-doped fiber 7, and output a few-cycle high-energy pulse signal with a central wavelength of 2 μm, a pulse width less than 20 fs, and a spectral width of several hundred nm.

[0048] In step S4, the semiconductor lasers pump the ultra-continuous spectrum in the thulium-doped fiber 7, which specifically includes the following steps:

[0049] S41: Since the emission band of the thulium-doped gain medium covers 2-μm light, by using the absorption characteristic of thulium ions in the thulium-doped fiber 7 for 793-nm light and the emission characteristic for 2-μm light, the light with a wavelength of 2 μm is amplified;

[0050] S42: By using the characteristics of the low intensity of the ultra-continuous spectrum itself and the loss of the thulium-doped fiber 7, the light with a wavelength greater than 2 μm and the light with a wavelength less than 2 μm are lost as noise, and the noise is filtered out.

[0051] In step S1, the erbium-doped mode-locked fiber laser 1 is replaced with a ytterbium-doped mode-locked fiber laser, and the excitation effect generated by the M-level highly nonlinear optical fiber 2 remains unchanged.

[0052] In step S4, when the thulium-doped fiber 7 is replaced with a holmium-doped fiber or a thulium-holmium co-doped fiber, the wavelength of the output few-cycle high-energy pulse signal remains unchanged. When the thulium-doped fiber 7 is replaced with a ytterbium-doped fiber, the wavelength of the output few-cycle high-energy pulse signal is 1 μm.

[0053] Therefore, the present invention adopts the above-mentioned mode-locked pulse fiber laser with high energy and few cycles and the emission method. A femtosecond erbium-doped mode-locked fiber laser is used to pump a highly nonlinear optical fiber, and then the ultra-continuous light generated by nonlinear effects such as the Raman effect and the self-phase modulation is used as a seed source and injected into a thulium-doped fiber amplifier to achieve the output of tunable few-cycle high-energy pulses. Finally, each parameter of the laser is optimized to achieve the precise output of few-cycle high-energy pulses of 2 μm.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the method of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify or equivalently replace the method of the present invention, and these modifications or equivalent replacements cannot make the modified method deviate from the spirit and scope of the method of the present invention.

Claims

1. A high-energy, low-cycle mode-locked pulsed fiber laser, characterized in that: It includes a high-power isolator and an erbium-doped mode-locked fiber laser and a thulium-doped fiber amplifier respectively arranged on both sides of the high-power isolator. The erbium-doped mode-locked fiber laser and the high-power isolator are connected through a high nonlinear optical fiber. The thulium-doped fiber amplifier includes a first signal pump combiner, a second signal pump combiner, a first pump source and a second pump source. The first pump source is arranged below the first signal pump combiner, and the second pump source is arranged below the second signal pump combiner. The first signal pump combiner and the second signal pump combiner are connected through a thulium-doped optical fiber. The erbium-doped mode-locked fiber laser, the high-power isolator, the first signal pump combiner and the second signal pump combiner are arranged on the same straight line.

2. A high-energy, low-cycle mode-locked pulse fiber laser according to claim 1, characterized in that: The first pump source and the second pump source both use LD pump sources, the wavelength of the LD pump source is set to 793 nm, and the maximum pump power of the LD pump source is set to 100 W.

3. A high-energy, low-cycle mode-locked pulse fiber laser according to claim 1, characterized in that: The erbium-doped mode-locked fiber laser uses a high-energy femtosecond erbium-doped mode-locked fiber laser. The central wavelength of the high-energy femtosecond erbium-doped mode-locked fiber laser is set to 1550nm, the output pulse width is set to 300fs, the average output power is set to 1W, the repetition rate is set to 40MHz, and the single pulse energy is set to 25nJ.

4. A high-energy, low-cycle mode-locked pulse fiber laser according to claim 1, characterized in that: The high nonlinear optical fiber adopts M-level high nonlinear optical fiber, and the nonlinear coefficient of M-level high nonlinear optical fiber is set to 20W -1 km -1 , the zero dispersion wavelength of the M-level high nonlinear optical fiber is set to 2000 nm, and the length of the M-level high nonlinear optical fiber is set to 40 cm.

5. A high-energy, low-cycle mode-locked pulse fiber laser according to claim 1, characterized in that: The central wavelength of the high-power isolator is set to 2μm, and the bandwidth coverage is set to 800nm-3200nm to ensure unidirectional transmission.

6. A high-energy, low-cycle mode-locked pulse fiber laser according to claim 1, characterized in that: The core diameter of the thulium-doped optical fiber is set to 10 μm, and the length of the thulium-doped optical fiber is set to 1 m.

7. A method for emitting a high-energy, low-cycle mode-locked pulsed fiber laser according to any one of claims 1 to 6, characterized in that: The steps include: S1: Erbium-doped mode-locked fiber laser uses the absorption characteristics of erbium ions for 980nm light and the emission characteristics for 1550nm light to output high-energy pulse signals with a pulse width of 300fs and a central wavelength of 1550nm; S2: The high-energy pulse signal excites the M-level high nonlinear fiber. The M-level high nonlinear fiber uses the Raman effect and self-phase modulation effect to broaden the high pulse signal into a supercontinuum spectrum. The wavelength coverage range of the supercontinuum spectrum is 800nm-3200nm. The supercontinuum spectrum passes through the high-power isolator and the first signal pump combiner into the thulium-doped fiber; S3: the first pump source and the second pump source emit a semiconductor laser with a wavelength of 793 nm, and the first signal pump combiner and the second signal pump combiner couple the semiconductor laser into the thulium-doped optical fiber; S4: Semiconductor laser pumps supercontinuum in thulium-doped fiber, outputting a short-cycle high-energy pulse signal with a central wavelength of 2μm, a pulse width of less than 20fs, and a spectral width of hundreds of nm.

8. A method for emitting a high-energy, low-cycle mode-locked pulsed fiber laser according to claim 7, characterized in that: In step S4, a semiconductor laser pumps a supercontinuum in a thulium-doped optical fiber, which specifically includes the following steps: S41: Utilizing the absorption characteristics of thulium ions in thulium-doped optical fiber for 793nm light and the emission characteristics for 2μm light, light with a wavelength of 2μm is amplified; S42: Taking advantage of the low intensity of the supercontinuum spectrum and the loss characteristics of thulium-doped optical fiber, the light with a wavelength greater than 2μm and the light with a wavelength less than 2μm are lost as noise and the noise is filtered out.

9. A method for emitting a high-energy, low-cycle mode-locked pulsed fiber laser according to claim 7, characterized in that: In step S1, the erbium-doped mode-locked fiber laser is replaced with an ytterbium-doped mode-locked fiber laser, and the excitation effect on the M-class high nonlinear fiber remains unchanged.

10. A method for emitting a high-energy, low-cycle mode-locked pulsed fiber laser according to claim 7, characterized in that: In step S4, the thulium-doped fiber is replaced with holmium-doped fiber or thulium-holmium co-doped fiber, and the wavelength of the output short-cycle high-energy pulse signal remains unchanged; the thulium-doped fiber is replaced with ytterbium-doped fiber, and the wavelength of the output short-cycle high-energy pulse signal is 1 μm.

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