A high-repetition-rate all-fiber ultrashort pulse laser

Abstract

The present invention discloses a high-repetition-rate all-fiber ultrashort pulse laser, comprising: a pump source, a wavelength division multiplexer, an erbium-doped fiber, and a highly nonlinear fiber are connected in sequence by optical fibers downstream of the optical path of the pump source; a coupler is connected by an optical fiber downstream of the optical path of the highly nonlinear fiber; a mode-locking device is connected by an optical fiber downstream of the optical path of the coupler; the light inlet of a circulator is connected by an optical fiber downstream of the optical path of the mode-locking device; the first light outlet of the circulator is connected by an optical fiber along the optical path direction to a first fiber Bragg grating; the optical path downstream of the first fiber Bragg grating is connected by an optical fiber to a second fiber Bragg grating; a grating wavelength tuning device is connected to the second fiber Bragg grating; and the second light outlet of the circulator is connected by an optical fiber along the optical path direction to the light inlet of the wavelength division multiplexer. By means of the wavelength adjustment device, the present invention realizes the change of the center wavelength interval between the two gratings, and further realizes a high-repetition-rate ultrashort pulse laser with adjustable repetition frequency.

Description

Technical Field

[0001] The present invention relates to the technical field of lasers, and particularly to a high-repetition-rate all-fiber ultrashort pulse laser. Background Art

[0002] Fiber lasers have received extensive attention due to their advantages such as compact structure, low cost, good heat dissipation, and good beam quality. Generally, high-repetition-rate ultrashort pulse fiber lasers are limited by the cavity length structure of fiber lasers, and generally the output repetition rate is below 1 GHz. If higher-repetition-rate ultrashort pulses are required, non-linear effects such as harmonic mode locking or dissipative four-wave mixing are needed.

[0003] Researchers have added filtering devices such as F-P interferometers or phase-shifted fiber gratings and highly non-linear fibers to the laser, and used the dissipative four-wave mixing effect to achieve high-repetition-rate ultrashort pulse output. However, in terms of repetition rate tuning, generally, the polarization state of the fiber in the laser is changed, and this method cannot accurately obtain a specific repetition rate. In addition, some researchers have constructed an M-Z interferometer using a tunable fiber delay line in the cavity, and achieved precise tuning of the repetition rate by adjusting the fiber delay line. However, this scheme destroys the all-fiber structure of the fiber laser and is expensive. Summary of the Invention

[0004] Embodiments of the present invention provide a high-repetition-rate all-fiber ultrashort pulse laser to solve the problems in the prior art that the scheme of using the dissipative four-wave mixing effect to achieve high-repetition-rate ultrashort pulse output cannot accurately obtain a specific repetition rate, and the scheme of adjusting the fiber delay line destroys the all-fiber structure of the fiber laser and is expensive.

[0005] On the one hand, embodiments of the present invention provide a high-repetition-rate all-fiber ultrashort pulse laser, including:

[0006] A pump source, the optical path downstream of the pump source is connected to a wavelength division multiplexer through a fiber, the optical path downstream of the wavelength division multiplexer is connected to an erbium-doped fiber through a fiber, the optical path downstream of the erbium-doped fiber is connected to a highly non-linear fiber through a fiber, the optical path downstream of the highly non-linear fiber is connected to a coupler through a fiber, the optical path downstream of the coupler is connected to a mode-locking device through a fiber, the optical path downstream of the mode-locking device is connected to the light input port of a circulator through a fiber, the first light output port of the circulator is connected to a first Bragg fiber grating through a fiber along the optical path direction, the optical path downstream of the first Bragg fiber grating is connected to a second Bragg fiber grating through a fiber, a grating wavelength tuning device is connected to the second Bragg fiber grating, and the second light output port of the circulator is connected to the light input port of the wavelength division multiplexer through a fiber along the optical path direction.

[0007] In a possible implementation, the mode-locking device is a saturable absorber.

[0008] In a possible implementation, the grating wavelength tuning device is a temperature transducer or a pressure transducer.

[0009] In a possible implementation, the erbium-doped optical fiber is coiled, and the erbium-doped optical fiber is used to amplify the laser light source of the pump source.

[0010] In a possible implementation, the highly nonlinear optical fiber is coiled, and the highly nonlinear optical fiber is used to excite the four-wave mixing effect.

[0011] In a possible implementation, the saturable absorber is one of carbon nanotubes, SESAM, or graphene.

[0012] A high-repetition-rate all-fiber ultrashort pulse laser in the present invention has the following advantages:

[0013] By means of a device in which two fiber Bragg gratings are connected in series, and a wavelength tuning device is added to one of the gratings, a filtering device with a controllable wavelength interval is realized. The central wavelength of the fiber grating is accurately tuned by temperature or pressure, and thus the interval between the wavelengths of the two gratings is accurately controlled. A ultrashort pulse laser system with an accurately controllable repetition rate is realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0015] Figure 1 FIG. is a schematic structural diagram of a high-repetition-rate all-fiber ultrashort pulse laser provided by an embodiment of the present invention;

[0016] Figure 2 FIG. is a schematic diagram of the relationship between the output pulse repetition rate of a high-repetition-rate all-fiber ultrashort pulse laser provided by an embodiment of the present invention and the interval between the central wavelengths of two fiber gratings;

[0017] Figure 3 FIG. is a schematic diagram of the relationship between the output pulse width of a high-repetition-rate all-fiber ultrashort pulse laser provided by an embodiment of the present invention and the interval between the central wavelengths of two fiber gratings;

[0018] Figure 4 FIG. is a spectral output diagram of a high-repetition-rate all-fiber ultrashort pulse laser provided by an embodiment of the present invention with an intermediate wavelength interval of 2 nm between two fiber gratings;

[0019] Figure 5 Spectral output diagram with a wavelength interval of 8 nm between two fiber Bragg gratings of a high-repetition-rate all-fiber ultrashort pulse laser provided by an embodiment of the present invention;

[0020] Figure 6 Spectral output diagram with a wavelength interval of 16 nm between two fiber Bragg gratings of a high-repetition-rate all-fiber ultrashort pulse laser provided by an embodiment of the present invention.

[0021] Explanation of reference numerals in the figure: 1. Pump source; 2. Wavelength division multiplexer; 3. Erbium-doped fiber; 4. Highly nonlinear fiber; 5. Coupler; 6. Mode-locking device; 7. Circulator; 8. First fiber Bragg grating; 9. Second fiber Bragg grating; 10. Grating wavelength tuning device. Detailed implementation manners

[0022] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0023] Figure 1 Schematic structural diagram of a high-repetition-rate all-fiber ultrashort pulse laser provided by an embodiment of the present invention; An embodiment of the present invention provides a high-repetition-rate all-fiber ultrashort pulse laser, including:

[0024] A pump source 1, the downstream of the optical path of the pump source 1 is connected to a wavelength division multiplexer 2 through an optical fiber, the downstream of the optical path of the wavelength division multiplexer 2 is connected to an erbium-doped fiber 3 through an optical fiber, the downstream of the optical path of the erbium-doped fiber 3 is connected to a highly nonlinear fiber 4 through an optical fiber, the downstream of the optical path of the highly nonlinear fiber 4 is connected to a coupler 5 through an optical fiber, the downstream of the optical path of the coupler 5 is connected to a mode-locking device 6 through an optical fiber, the downstream of the optical path of the mode-locking device 6 is connected to the light input port of a circulator 7 through an optical fiber, the first light output port of the circulator 7 is connected to a first fiber Bragg grating 8 through an optical fiber along the optical path direction, the downstream of the optical path of the first fiber Bragg grating 8 is connected to a second fiber Bragg grating 9 through an optical fiber, a grating wavelength tuning device 10 is connected to the second fiber Bragg grating 9, and the second light output port of the circulator 7 is connected to the light input port of the wavelength division multiplexer 2 through an optical fiber along the optical path direction;

[0025] The mode-locking device 6 is a saturable absorber, and the saturable absorber is one of carbon nanotubes, SESAM or graphene;

[0026] The mode-locking device 6 is a saturable absorber, and the grating wavelength tuning device 10 is a temperature transducer or a pressure transducer;

[0027] The erbium-doped fiber 3 is wound, and the erbium-doped fiber 3 is used to amplify the laser light source of the pump source 1. The highly nonlinear fiber 4 is wound, and the highly nonlinear fiber 4 is used to excite the four-wave mixing effect.

[0028] Exemplarily, the pump source 1 is input into the resonant cavity through the wavelength division multiplexer 2 to pump the erbium-doped fiber 3, and the highly nonlinear fiber 4 is used to excite the four-wave mixing effect. The mode-locking device 6 can be a saturable absorber such as a carbon nanotube, SESAM (Semiconductor Saturable Absorber Mirror), graphene, etc., and the grating wavelength tuning device 10 can be a temperature transducer or a pressure transducer.

[0029] By changing the central wavelength of one of the Bragg fiber gratings through the grating wavelength tuning device 10, the distance between the central wavelengths of the first Bragg fiber grating 8 and the second Bragg fiber grating 9 is adjusted. The repetition frequency of the high-repetition-rate ultrashort pulse achieved by dissipating the four-wave mixing effect has a direct relationship with the distance between the central wavelengths of the first Bragg fiber grating 8 and the second Bragg fiber grating 9. Therefore, by adjusting the distance between the centers of the first Bragg fiber grating 8 and the second Bragg fiber grating 9, a high-repetition-rate ultrashort pulse output with a tunable repetition frequency can be achieved.

[0030] In a possible embodiment, Figure 2 and Figure 3 are the relationships between the repetition frequency of the output pulse, the width of the output pulse, and the change in the central wavelength interval of the first Bragg fiber grating 8 and the second Bragg fiber grating 9, respectively. It can be seen from the figure that when the central wavelength interval of the first Bragg fiber grating 8 and the second Bragg fiber grating 9 changes from 0.5 nm to 16 nm, the repetition frequency of the output pulse can be continuously tuned between 62.1 GHz and 2000 GHz. The pulse width can be continuously tuned between 8.1 ps and 0.24 ps, as Figure 4 、 5As shown in FIGS. 6(a) and (b), the pulse and spectrum outputs with intermediate wavelength intervals of 2 nm, FIGS. 6(c) and (d), 8 nm, and FIGS. 6(e) and (f), 16 nm, respectively, between the first Bragg fiber grating 8 and the second Bragg fiber grating 9. The pump 1 used is a 980 nm semiconductor laser. The length of the erbium-doped fiber 3 is 15 m, and the absorption coefficient is 6 dB / m @ 980 nm. The output ratio of the coupler 5 is 10%. The mode-locking device 6 is a carbon nanotube film with a modulation depth of 30% and a saturation power of 10 W. The 3-dB bandwidths of both the first Bragg fiber grating 8 and the second Bragg fiber grating 9 themselves are 0.1 nm. The highly nonlinear fiber 4 used has a length of 100 m and a third-order nonlinear coefficient of 11 W-1 km-1.

[0031] Although the preferred embodiments of the present invention have been described, additional changes and modifications can be made to these embodiments by those skilled in the art once they learn the basic creative concept. Therefore, the appended claims are intended to be construed to include the preferred embodiments as well as all changes and modifications that fall within the scope of the present invention.

[0032] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these modifications and variations.

Claims

1. A high repetition rate all-fiber ultrashort pulse laser, characterized in that: include: A pump source (1), wherein the optical path downstream of the pump source (1) is connected to a wavelength division multiplexer (2) through an optical fiber, the optical path downstream of the wavelength division multiplexer (2) is connected to an erbium-doped optical fiber (3) through an optical fiber, the optical path downstream of the erbium-doped optical fiber (3) is connected to a high nonlinear optical fiber (4) through an optical fiber, the optical path downstream of the high nonlinear optical fiber (4) is connected to a coupler (5) through an optical fiber, the optical path downstream of the coupler (5) is connected to a mode-locking device (6) through an optical fiber, the optical path downstream of the mode-locking device (6) is connected to a light inlet of a circulator (7) through an optical fiber, the first light outlet of the circulator (7) is connected to a first Bragg fiber grating (8) through an optical fiber along the optical path direction, the optical path downstream of the first Bragg fiber grating (8) is connected to a second Bragg fiber grating (9) through an optical fiber, the second Bragg fiber grating (9) is connected to a grating wavelength tuning device (10), and the second light outlet of the circulator (7) is connected to a light inlet of the wavelength division multiplexer (2) through an optical fiber along the optical path direction; The mode-locking device (6) is a saturated absorber; The grating wavelength tuning device (10) is a temperature converter or a pressure converter.

2. A high repetition rate all-fiber ultrashort pulse laser according to claim 1, characterized in that: The erbium-doped optical fiber (3) is arranged in a coiled state, and the erbium-doped optical fiber (3) is used to perform gain amplification on the laser light source of the pump source (1).

3. The high repetition rate all-fiber ultrashort pulse laser according to claim 1, characterized in that: The highly nonlinear optical fiber (4) is arranged in a coiled state, and the highly nonlinear optical fiber (4) is used to excite a four-wave mixing effect.

4. The high repetition rate all-fiber ultrashort pulse laser according to claim 1, characterized in that: The saturable absorber is one of carbon nanotubes, SESAM or graphene.

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