Picosecond Pulse Fiber Amplifiers and Lasers

Abstract

This specification discloses a picosecond pulse fiber amplifier and laser, and relates to the field of fiber laser amplification technology. The picosecond pulse fiber amplifier includes a polarization-maintaining fiber picosecond mode-locked oscillator, a first fiber circulator, a first polarization-maintaining fiber polarization beam splitter, a fiber Faraday rotation structure, a fiber grating, a second polarization-maintaining fiber polarization beam splitter, and a second fiber circulator connected in sequence through optical fibers, and also includes an amplification frequency modulation component connected to the first fiber circulator and the second fiber circulator through optical fibers. It can be seen that the picosecond pulse fiber amplifier separates the signal light and the stray light transmitted from the fiber grating by controlling the polarization state of the laser, and can complete the pulse broadening and compression of the laser only through a fiber grating, reducing the nonlinear effect generated in the pulse amplification process, thereby obtaining a high-energy pulse equivalent to the input signal light pulse width in the all-fiber structure, with a simple structure and easy integration.

Description

Technical Field

[0001] The present invention relates to the field of fiber laser amplification technology, and in particular to a picosecond pulse fiber amplifier and laser. Background Art

[0002] Pulse lasers of a few picoseconds to tens of picoseconds are widely used in cutting, high-precision marking, and drilling of glass, sapphire, wafer dicing, and display panels. Usually, picosecond pulse lasers can be obtained through mode locking technology, but the pulse energy is very limited, usually at the pJ level, which is difficult to meet the needs of the above applications.

[0003] In fiber lasers, master oscillator power amplification and chirped pulse amplification techniques are usually used to increase pulse energy.

[0004] However, the transmission of high-energy narrow pulses of the picosecond level in optical fibers will produce strong nonlinear effects. The use of master oscillator power amplification technology will involve multimode optical fibers or photonic crystal fibers with large core diameters, which have special structures, are difficult to handle, and are expensive. When using traditional chirped pulse amplification technology to amplify picosecond laser pulses, fiber gratings or diffraction gratings with positive dispersion are usually used for pulse broadening, and diffraction gratings, hollow-core photonic crystal fibers with negative dispersion, or volume chirped Bragg gratings are used for pulse compression, which involves some expensive dispersion components and complex spatial optical paths, is costly, and is not easy to integrate. Summary of the invention

[0005] This specification provides a picosecond pulse fiber amplifier and a laser to at least partially solve the above-mentioned problems existing in the prior art.

[0006] This manual adopts the following technical solutions:

[0007] This specification provides a picosecond pulse fiber amplifier, including a polarization-maintaining fiber picosecond mode-locked oscillator, a first fiber circulator, a first polarization-maintaining fiber polarization beam splitter, a fiber Faraday rotation structure, a second polarization-maintaining fiber polarization beam splitter, a second fiber circulator, a fiber grating, and an amplification frequency modulation component;

[0008] The first optical fiber circulator is configured with an A end, a B end, and a C end, and the light input from the A end is output from the B end, and the light input from the B end is output from the C end; the second optical fiber circulator is configured with a D end, an E end, and an F end, and the light input from the D end is output from the E end, and the light input from the E end is output from the F end;

[0009] The polarization-maintaining fiber picosecond mode-locked oscillator, the first fiber circulator, the first polarization-maintaining fiber polarization beam splitter, the fiber Faraday rotation structure, the fiber grating, the second polarization-maintaining fiber polarization beam splitter and the second fiber circulator are connected in sequence through optical fibers; and the first fiber circulator, the amplifying frequency modulation component and the second fiber circulator are connected in sequence through optical fibers; wherein the A end, the B end and the C end of the first fiber circulator are respectively connected to the polarization-maintaining fiber picosecond mode-locked oscillator, the first polarization-maintaining fiber polarization beam splitter and the amplifying frequency modulation component; and the D end and the E end of the second fiber circulator are respectively connected to the amplifying frequency modulation component and the second polarization-maintaining fiber polarization beam splitter.

[0010] Preferably, the initial laser output by the polarization-maintaining optical fiber picosecond mode-locked oscillator is a picosecond-level pulsed laser.

[0011] Preferably, the initial laser is linearly polarized light, and the polarization direction is horizontal polarization direction;

[0012] The first polarization-maintaining optical fiber polarization beam splitter can transmit the component of the incident light with a horizontal polarization direction to the optical fiber Faraday rotation structure, and can transmit the component of the incident light with a vertical polarization direction to the first failure direction; the vertical polarization direction is perpendicular to the horizontal polarization direction;

[0013] The second polarization-maintaining optical fiber polarization beam splitter can transmit the component of the incident light with a horizontal polarization direction to the optical fiber grating, and can transmit the component of the incident light with a vertical polarization direction to a preset second failure direction;

[0014] The optical fiber Faraday rotation structure can deflect the polarization direction of light passing through it by 90 degrees.

[0015] Preferably, the initial laser light emitted by the polarization-maintaining fiber picosecond mode-locked oscillator with the horizontal polarization direction can be transmitted along the first fiber circulator, the first polarization-maintaining fiber polarization beam splitter, the fiber Faraday rotation structure, the fiber grating, the fiber Faraday rotation structure, the first polarization-maintaining fiber polarization beam splitter, the first fiber circulator, the amplification frequency modulation component, the second fiber circulator, the second polarization-maintaining fiber polarization beam splitter, the fiber grating, the second polarization-maintaining fiber polarization beam splitter, and the second fiber circulator, and output through the F end of the second fiber circulator;

[0016] The fiber grating is used to perform pulse broadening on the incident light transmitted from the direction of the fiber Faraday rotation structure, and reflect the light that has completed pulse broadening to the fiber Faraday rotation structure; the fiber grating is also used to perform pulse compression on the incident light transmitted from the direction of the second polarization-maintaining fiber polarization beam splitter, and reflect the light that has completed pulse compression to the second polarization-maintaining fiber polarization beam splitter.

[0017] Preferably, the amplification and frequency modulation component comprises a single-mode fiber amplifier stage, a fiber acousto-optic modulator and a double-clad fiber amplifier stage which are sequentially connected via optical fibers.

[0018] Preferably, both the A end and the C end of the first optical fiber circulator are polarization-maintaining single-mode optical fibers;

[0019] The B end of the first fiber circulator and / or the fiber grating and / or the D end of the second fiber circulator and / or the E end of the second fiber circulator and / or the second polarization-maintaining fiber polarization beam splitter and / or the optical fiber of the double-clad fiber amplifier stage use polarization-maintaining passive optical fibers with the same core diameter, and the core diameter of the polarization-maintaining optical fiber is between 10µm and 30µm.

[0020] Preferably, the fiber grating is a chirped grating, which can provide positive dispersion for forward incident light and negative dispersion for reverse incident light;

[0021] The light incident from the direction of the optical fiber Faraday rotation structure is forward incident light; the light incident from the direction of the second polarization-maintaining optical fiber polarization beam splitter is reverse incident light.

[0022] Preferably, the reflectivity of the fiber grating is greater than or equal to 70%.

[0023] Preferably, the single-mode optical fiber amplifier stage is a single-stage or multi-stage single-mode optical fiber amplifier structure, and the pumping mode is forward core pumping or backward core pumping;

[0024] The double-clad optical fiber amplifier stage is multi-mode semiconductor laser cladding pumped, and the gain optical fiber is a double-clad optical fiber with a core diameter of 10µm-30µm.

[0025] On the other hand, the present specification provides a laser, which includes the picosecond pulse fiber amplifier provided by any one of the above aspects.

[0026] At least one of the above technical solutions adopted in this specification can achieve the following beneficial effects:

[0027] According to the above content, the picosecond pulse fiber amplifier includes a polarization-maintaining fiber picosecond mode-locked oscillator, a first fiber circulator, a first polarization-maintaining fiber polarization beam splitter, a fiber Faraday rotation structure, a second polarization-maintaining fiber polarization beam splitter, a second fiber circulator, a fiber grating, and an amplification frequency modulation component. Among them, the polarization-maintaining fiber picosecond mode-locked oscillator, the first fiber circulator, the first polarization-maintaining fiber polarization beam splitter, the fiber Faraday rotation structure, the fiber grating, the second polarization-maintaining fiber polarization beam splitter, and the second fiber circulator are connected in sequence through optical fibers. And the first fiber circulator, the amplification frequency modulation component, and the second fiber circulator are connected in sequence through optical fibers. The A end, the B end, and the C end of the first fiber circulator are respectively connected to the polarization-maintaining fiber picosecond mode-locked oscillator, the first polarization-maintaining fiber polarization beam splitter, and the amplification frequency modulation component. The D end and the E end of the second fiber circulator are respectively connected to the amplification frequency modulation component and the second polarization-maintaining fiber polarization beam splitter.

[0028] It can be seen that the picosecond pulse fiber amplifier separates the signal light and the stray light transmitted from the fiber grating by controlling the laser polarization state through the first polarization-maintaining fiber polarization beam splitter, the first circulator and other components. The laser pulse can be broadened and compressed only by a fiber grating, which effectively reduces the nonlinear effect produced in the pulse amplification process, thereby obtaining a high-energy pulse with a pulse width equivalent to that of the input signal light in the all-fiber structure. The structure is simple, easy to integrate, reduces the cost, reduces the size of the equipment, and improves the practicability of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The drawings described herein are used to provide a further understanding of this specification and constitute a part of this specification. The illustrative embodiments and descriptions of this specification are used to explain this specification and do not constitute an improper limitation on this specification. In the drawings:

[0030] Figure 1 This is a schematic diagram of the structure of a picosecond pulse fiber amplifier in this specification;

[0031] Figure 2 A schematic diagram of the optical path of the working process of a picosecond pulse fiber amplifier provided in one embodiment of the present specification;

[0032] Figure 3 A schematic diagram of the optical path of the working process of a picosecond pulse fiber amplifier provided in one embodiment of the present specification;

[0033] Figure 4 A schematic diagram of the optical path of the working process of a picosecond pulse fiber amplifier provided in one embodiment of the present specification;

[0034] Figure 5A schematic diagram of the polarization direction of an optical fiber during the operation of a picosecond pulse optical fiber amplifier provided in one embodiment of the present specification;

[0035] Figure 6 A schematic diagram of the polarization direction of an optical fiber during the operation of a picosecond pulse optical fiber amplifier provided in one embodiment of the present specification;

[0036] Figure 7 A schematic diagram of the polarization direction of an optical fiber during the operation of a picosecond pulse optical fiber amplifier provided in one embodiment of the present specification;

[0037] Figure 8 A schematic diagram of the optical path of the working process of a picosecond pulse fiber amplifier provided in one embodiment of the present specification;

[0038] Fig. 9 A schematic diagram of the optical path of a picosecond pulse fiber amplifier provided for one embodiment of the present specification.

[0039] Description of reference numerals:

[0040] Polarization-maintaining fiber picosecond mode-locked oscillator 1; first fiber circulator 21; first polarization-maintaining fiber polarization beam splitter 31; fiber Faraday rotation structure 4; second polarization-maintaining fiber polarization beam splitter 32; second fiber circulator 22; fiber grating 5; amplification frequency modulation component 6; polarization state marker 7; single-mode fiber amplifier stage 61; fiber acousto-optic modulator 62; double-clad fiber amplifier stage 63; first Faraday rotator 41; second Faraday rotator 42. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solutions and advantages of this specification more clear, the technical solutions of this specification will be clearly and completely described below in combination with the specific embodiments of this specification and the corresponding drawings. Obviously, the described embodiments are only part of the embodiments of this specification, not all of the embodiments. Based on the embodiments in this specification, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0042] In the description of the present invention, it should be noted that the term "or" is generally used in a meaning including "and / or", unless the content clearly indicates otherwise.

[0043] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense. In addition, in the description of the present application, the terms "first", "second" and the like are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0044] Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0045] The technical solutions provided by the embodiments of this specification are described in detail below in conjunction with the accompanying drawings.

[0046] Figure 1 is a schematic diagram of the structure of a picosecond pulse fiber amplifier in this specification, such as Figure 1 As shown, the picosecond pulse fiber amplifier includes a polarization-maintaining fiber picosecond mode-locked oscillator 1, a first fiber circulator 21, a first polarization-maintaining fiber polarization beam splitter 31, a fiber Faraday rotation structure 4, a second polarization-maintaining fiber polarization beam splitter 32, a second fiber circulator 22, a fiber grating 5 and an amplification frequency modulation component 6.

[0047] Preferably, the polarization-maintaining optical fiber picosecond mode-locked oscillator 1 is used to output an initial laser. Further preferably, the polarization state of the initial laser output by the polarization-maintaining optical fiber picosecond mode-locked oscillator 1 is a horizontal polarization state.

[0048] Preferably, the initial laser light is linearly polarized light, and the polarization direction of the initial laser light is horizontal polarization direction.

[0049] Preferably, the initial laser is a pulsed laser, and the pulse width is in the order of picoseconds.

[0050] Preferably, the pulse width of the initial laser is 1-99 picoseconds.

[0051] Preferably, the above devices are all connected via optical fibers.

[0052] Preferably, the optical fiber connected to the above-mentioned device is a polarization-maintaining optical fiber, which can maintain the polarization state of the initial laser unchanged during the transmission of the initial laser.

[0053] Preferably, when the optical signal is transmitted in the polarization-maintaining optical fiber, it propagates along the slow axis of the polarization-maintaining optical fiber.

[0054] Preferably, the core diameter of the polarization-maintaining optical fiber is less than or equal to 30 μm.

[0055] Preferably, the polarization-maintaining optical fiber is a double-clad polarization-maintaining optical fiber or a single-clad polarization-maintaining optical fiber.

[0056] Therefore, in a preferred embodiment of the present specification, the first optical fiber circulator 21 is configured with an A end, a B end, and a C end, and the light input from the A end is output from the B end, and the light input from the B end is output from the C end. In addition, the second optical fiber circulator 22 is configured with a D end, an E end, and an F end, and the light input from the D end is output from the E end, and the light input from the E end is output from the F end.

[0057] Preferably, the F end is of the same optical fiber type as the pigtail at the D end or the E end or is a spatial output.

[0058] Preferably, the first polarization-maintaining fiber polarization beam splitter 31 can transmit the component of the incident light with a horizontal polarization direction to the fiber Faraday rotation structure 4, and can transmit the component of the incident light with a vertical polarization direction to the first failure direction.

[0059] Preferably, the vertical polarization direction is perpendicular to the horizontal polarization direction.

[0060] Preferably, the second polarization-maintaining fiber polarization beam splitter 32 can transmit the component of the incident light with a horizontal polarization direction to the fiber grating 5, and can transmit the component of the incident light with a vertical polarization direction to the preset second failure direction.

[0061] Preferably, the first failure direction and the second failure direction are both preset, and the lasers transmitted to the first failure direction and the second failure direction are consumed, absorbed or wasted, and will not affect the components of the picosecond pulse fiber amplifier and the transmission of the initial laser.

[0062] It should be noted that, in this specification, the laser component transmitted to the fiber Faraday rotation structure 4 through the first polarization-maintaining fiber beam splitter is referred to as the first laser component, and the laser component transmitted to the fiber grating 5 through the second polarization-maintaining fiber polarization beam splitter 32 is referred to as the second laser component.

[0063] Preferably, the optical fiber Faraday rotation structure 4 can deflect the polarization direction of the light passing through it by 90 degrees. That is to say, the optical fiber Faraday rotation structure 4 can deflect the polarization direction of the first laser component with a horizontal polarization direction by 90 degrees to form a first deflected laser. The polarization direction of the first deflected laser is a vertical polarization direction.

[0064] Preferably, the fiber grating 5 can reflect light of a specific wavelength, and the specific wavelength can be adjusted.

[0065] Preferably, the wavelength of the initial laser is a preset value, and the structure of the fiber grating 5 is adapted to the wavelength of the initial laser, so that the fiber grating 5 can reflect the initial laser. Moreover, the wavelength of the initial laser does not change when passing through the components of the picosecond pulse fiber amplifier. In other words, the first deflected laser, the first laser component, the second laser component, etc. formed by the initial laser can all be reflected after being irradiated to the fiber grating 5.

[0066] Preferably, the fiber grating 5 can perform pulse broadening on the incident light transmitted from the direction of the fiber Faraday rotation structure 4, and reflect the light after pulse broadening to the fiber Faraday rotation structure 4. In addition, the fiber grating 5 can also perform pulse compression on the incident light transmitted from the direction of the second polarization-maintaining fiber polarization beam splitter 32, and reflect the optical signal after pulse compression to the second polarization-maintaining fiber polarization beam splitter 32.

[0067] That is, the first deflected laser light transmitted from the fiber Faraday rotation structure 4 to the fiber Bragg grating 5 forms a first stretched laser light after being pulse stretched by the fiber Bragg grating 5 , and is reflected by the fiber Bragg grating 5 to the fiber Faraday rotation structure 4 .

[0068] Preferably, when the first broadened laser passes through the optical fiber Faraday rotation structure 4, its polarization direction can be deflected by 90 degrees by the optical fiber Faraday rotation structure 4 to form a second deflected laser with a horizontal polarization direction, and is transmitted by the optical fiber Faraday rotation structure 4 to the first polarization-maintaining optical fiber polarization beam splitter 31.

[0069] Preferably, the first polarization-maintaining fiber polarization beam splitter 31 is a single-sided polarization beam splitter, which can only split the light signal incident from the direction of the fiber Faraday rotation structure 4, and for the light signal incident from the direction of the first fiber circulator 21, the first polarization-maintaining fiber polarization beam splitter 31 allows it to be completely transmitted to the fiber Faraday rotation structure 4. Similarly, the second polarization-maintaining fiber beam splitter can also only split the light incident from the direction of the fiber grating 5, and for the light signal incident from the direction of the second fiber circulator 22, the second polarization-maintaining fiber polarization beam splitter 32 allows it to be completely transmitted to the fiber grating 5.

[0070] Of course, the first polarization-maintaining fiber polarization beam splitter 31 and the second polarization-maintaining fiber polarization beam splitter 32 may also be double-sided polarization beam splitters, but it should be emphasized that if the first polarization-maintaining fiber polarization beam splitter 31 is a double-sided polarization beam splitter, the polarization direction of the laser component transmitted to the first invalid direction is the same regardless of which side the laser is incident from. Similarly, if the second polarization-maintaining fiber polarization beam splitter 32 is a double-sided polarization beam splitter, the polarization direction of the laser component transmitted to the second invalid direction is the same regardless of which side the laser is incident from.

[0071] Preferably, after being transmitted to the B end of the first optical fiber circulator 21 via the first polarization-maintaining optical fiber polarization beam splitter 31 , the second deflected laser can be emitted from the C end of the first optical fiber circulator 21 and transmitted to the amplifying frequency modulation component 6 .

[0072] Preferably, the amplifying and frequency modulating component 6 is used to amplify and frequency modulate the second deflected laser to form an amplified laser. The amplifying and frequency modulating component 6 is also used to transmit the amplified laser to the D end of the second optical fiber circulator 22 .

[0073] Preferably, after being transmitted to the D end of the second optical fiber circulator 22 , the amplified laser can be emitted from the E end of the second optical fiber circulator 22 and transmitted to the second polarization-maintaining optical fiber polarization beam splitter 32 .

[0074] Preferably, the second polarization-maintaining fiber polarization beam splitter 32 can transmit the component of the amplified laser with a horizontal polarization direction to the fiber grating 5, and transmit the component of the amplified laser with a vertical polarization direction to the preset second failure direction.

[0075] Preferably, the component transmitted to the fiber grating 5 by the second polarization-maintaining fiber polarization beam splitter 32 is the second laser component.

[0076] Preferably, the fiber grating 5 is also used to perform pulse compression on the second laser component to form compressed laser light, and reflect the compressed laser light to the second polarization-maintaining fiber polarization beam splitter 32 .

[0077] Preferably, the second polarization-maintaining fiber polarization beam splitter 32 can transmit the compressed laser to the E end of the second fiber circulator 22 .

[0078] Preferably, the second optical fiber circulator 22 can output the compressed laser from the F end.

[0079] Preferably, the polarization-maintaining fiber picosecond mode-locked oscillator 1, the first fiber circulator 21, the first polarization-maintaining fiber polarization beam splitter 31, the fiber Faraday rotation structure 4, the fiber grating, the second polarization-maintaining fiber polarization beam splitter 32 and the second fiber circulator 22 are connected in sequence through optical fibers.

[0080] Further preferably, the first fiber optic circulator 21, the amplifying frequency modulation component 6 and the second fiber optic circulator 22 are connected in sequence through optical fibers.

[0081] The A end, B end and C end of the first optical fiber circulator 21 are respectively connected to the polarization-maintaining optical fiber picosecond mode-locked oscillator 1, the first polarization-maintaining optical fiber polarization beam splitter 31 and the amplification frequency modulation component 6. The D end and E end of the second optical fiber circulator 22 are respectively connected to the amplification frequency modulation component 6 and the second polarization-maintaining optical fiber polarization beam splitter 32. The F end of the second optical fiber circulator 22 is an output end for outputting compressed laser light. The compressed laser light is obtained after the initial laser light is processed by the picosecond pulse optical fiber amplifier.

[0082] Figure 2 as well as Figure 3All of them are optical path schematic diagrams of the working process of the picosecond pulse fiber amplifier provided by an embodiment of this specification, such as Figure 2 as well as Figure 3 As shown, the fiber Bragg grating 5 mainly plays the role of pulse broadening, pulse compression and reflection, and the optical signal transmitted from the fiber Bragg grating 5 is output from the idle ends of the first polarization-maintaining fiber polarization beam splitter 31 and the second polarization-maintaining fiber polarization beam splitter 32. The idle end of the first polarization-maintaining fiber polarization beam splitter 31 corresponds to the first failure direction, and the idle end of the second polarization-maintaining fiber polarization beam splitter 32 corresponds to the second failure direction.

[0083] Figure 4 A schematic diagram of the optical path of the working process of the picosecond pulse fiber amplifier provided in one embodiment of the present specification, and compared with Figure 2 as well as Figure 3 , Figure 4 The lasers traveling back and forth between the two optical elements are shown separately, as shown in the figure. Figure 4 As shown, different line segment types identify different types of rays.

[0084] Figure 5 , Figure 6 as well as Figure 7 All of them are schematic diagrams of the polarization direction of the optical fiber during the working process of the picosecond pulse optical fiber amplifier provided by an embodiment of the present specification, such as Figure 5 , Figure 6 as well as Figure 7 As shown, different polarization directions are indicated by lines with double-headed arrows pointing to different configurations. Figure 5 In the example, for a light path with two round-trip light beams, the line segment marker located above the optical element matches the light path marker located relatively above, and the line segment marker located below the optical element matches the light path marker located relatively below. Figure 6 as well as Figure 7 In the figure, the line segment mark located above the optical element represents the polarization direction of the light when it passes through for the first time, and the line segment mark located above the optical element represents the polarization direction of the light when it passes through for the second time.

[0085] According to the above embodiment, the picosecond pulse fiber amplifier includes a polarization-maintaining fiber picosecond mode-locked oscillator 1, a first fiber circulator 21, a first polarization-maintaining fiber polarization beam splitter 31, a fiber Faraday rotation structure 4, a second polarization-maintaining fiber polarization beam splitter 32, a second fiber circulator 22, a fiber grating 5, and an amplification frequency modulation component 6. Among them, the polarization-maintaining fiber picosecond mode-locked oscillator 1, the first fiber circulator 21, the first polarization-maintaining fiber polarization beam splitter 31, the fiber Faraday rotation structure 4, the fiber grating, the second polarization-maintaining fiber polarization beam splitter 32, and the second fiber circulator 22 are connected in sequence through optical fibers. And the first fiber circulator 21, the amplification frequency modulation component 6, and the second fiber circulator 22 are connected in sequence through optical fibers. The A end, the B end, and the C end of the first fiber circulator 21 are respectively connected to the polarization-maintaining fiber picosecond mode-locked oscillator 1, the first polarization-maintaining fiber polarization beam splitter 31, and the amplification frequency modulation component 6. The D end and the E end of the second optical fiber circulator 22 are connected to the amplifying frequency modulation component 6 and the second polarization-maintaining optical fiber polarization beam splitter 32 respectively.

[0086] It can be seen from the above content that the picosecond pulse fiber amplifier controls the transmission direction of the laser based on the polarization direction of the laser through the first polarization-maintaining fiber polarization beam splitter 31, the first circulator and other components, so that the laser passes through the fiber grating 5 twice during the transmission process, and the pulse broadening and compression of the laser are completed only through one fiber grating 5. In the process of pulse amplification, the nonlinear effect in the optical fiber transmission process is reduced, the cost is reduced, the size of the equipment is reduced, and the practicability of the equipment is improved.

[0087] Preferably, the amplification and frequency modulation component 6 includes a single-mode fiber amplifier stage 61, a fiber acousto-optic modulator 62 and a double-clad fiber amplifier stage 63 which are sequentially connected via optical fibers.

[0088] Figure 8 A schematic diagram of the optical path of the working process of a picosecond pulse fiber amplifier provided in one embodiment of the present specification is shown in FIG. Figure 8 As shown, the amplification and frequency modulation component 6 includes a single-mode fiber amplifier stage 61, a fiber acousto-optic modulator 62, and a double-clad fiber amplifier stage 63 which are sequentially connected through optical fibers.

[0089] Preferably, the picosecond pulse fiber amplifier also includes a heat dissipation component.

[0090] Preferably, the heat dissipation component is used to dissipate heat for the fiber grating 5.

[0091] Preferably, the optical fiber Faraday rotation structure 4 includes a first Faraday rotator 41 and a second Faraday rotator 42 connected in sequence. The first Faraday rotator 41 and the second Faraday rotator 42 are both capable of rotating the polarization direction of the incident light by 45 degrees, and the first Faraday rotator 41 and the second Faraday rotator 42 rotate the polarization direction in the same direction. That is, the first Faraday rotator 41 and the second Faraday rotator 42 both rotate the polarization direction of the incident light in a clockwise direction, or the first Faraday rotator 41 and the second Faraday rotator 42 both rotate the polarization direction of the incident light in a counterclockwise direction.

[0092] Preferably, the pulse width of the initial laser is 1 picosecond to 100 picoseconds.

[0093] Preferably, the polarization direction is a horizontal polarization direction, that is, the polarization state is in a horizontal polarization state.

[0094] Preferably, the polarization direction is a vertical polarization direction, that is, the polarization state is in a vertical polarization state.

[0095] Preferably, the pigtails of the first polarization-maintaining fiber polarization beam splitter 31 and / or the second polarization-maintaining fiber polarization beam splitter 32 and / or the double-clad fiber amplifier stage 63 and / or the polarization-maintaining fiber picosecond mode-locked oscillator 1 and / or the first fiber circulator 21 and / or the fiber Faraday rotation structure 4 and / or the second fiber circulator 22 and / or the single-mode fiber amplifier stage 61 and / or the fiber acousto-optic modulator 62 are all polarization-maintaining fibers with the same core diameter, and the lengths of the pigtails in the optical path are all less than a preset pigtail length threshold.

[0096] Preferably, the lengths of the pigtails of the first polarization-maintaining fiber polarization beam splitter 31 and / or the second polarization-maintaining fiber polarization beam splitter 32 and / or the double-clad fiber amplifier stage 63 and / or the polarization-maintaining fiber picosecond mode-locked oscillator 1 and / or the first fiber circulator 21 and / or the fiber Faraday rotation structure 4 and / or the second fiber circulator 22 and / or the single-mode fiber amplifier stage 61 and / or the fiber acousto-optic modulator 62 are all the shortest lengths that can maintain the normal operation of the picosecond pulse fiber amplifier.

[0097] Preferably, the reflectivity of the fiber grating 5 is greater than or equal to 70%.

[0098] Preferably, the single-mode optical fiber amplifier stage 61 is a single-stage or multi-stage single-mode optical fiber amplifier stage 61, and the pumping mode is forward core pumping or backward core pumping.

[0099] Preferably, the double-clad fiber amplifier stage 63 is a double-clad fiber amplifier stage 63 pumped by a multi-mode semiconductor laser, which can be a single-stage or multi-stage amplification, and the fiber core diameter is between 10µm and 30µm.

[0100] Preferably, the power of the laser pulse of the compressed laser is in the order of hundreds of nJ to µJ. The picosecond pulse fiber amplifier uses all fiber components that are easy to integrate, and does not use complex space devices, thereby improving the stability of the device.

[0101] Preferably, the polarization-maintaining fiber picosecond mode-locked oscillator 1 outputs the initial laser to the A end of the first fiber circulator 21, and the initial laser is output from the B end of the first fiber circulator 21 to the first polarization-maintaining fiber polarization beam splitter 31, wherein the first laser component in the horizontal polarization state is transmitted to the first Faraday rotator 41 and the second Faraday rotator 42. The second laser component in the vertical polarization state is transmitted to the first failure direction from the idle end of the first polarization-maintaining fiber polarization beam splitter 31. After the first laser component is deflected by the first Faraday rotator 41 and the second Faraday rotator 42, a first deflected laser in the vertical polarization state is formed, and the first deflected laser is output to the fiber grating 5 by the second Faraday rotator 42. The fiber grating 5 can perform pulse broadening on the first deflected laser, and reflect most of the optical signal of the first deflected laser (i.e., the first broadened laser) back to the second Faraday rotator 42 and the first Faraday rotator 41, and a small part of the optical signal can be transmitted from the fiber grating 5, but because the polarization state of this part of the optical signal is a vertical polarization state, after being transmitted to the second polarization-maintaining fiber polarization beam splitter 32 via the fiber grating 5, this part of the optical signal will be output from the idle end of the second polarization-maintaining fiber polarization beam splitter 32 to the second failure direction. The first broadened laser reflected by the fiber grating 5 will be deflected again by the second Faraday rotator 42 and the first Faraday rotator 41 to form a second deflected laser with a horizontal polarization direction, and transmitted to the first polarization-maintaining fiber polarization beam splitter 31 by the fiber Faraday rotator structure 4. The first polarization-maintaining fiber polarization beam splitter 31 can transmit the second deflected laser to the B end of the first fiber circulator 21. The second deflected laser can be output from the C end of the first fiber circulator 21 to the single-mode fiber amplifier stage 61, the fiber acousto-optic modulator 62 and the double-clad fiber amplifier stage 63. After being amplified by the single-mode fiber amplifier stage 61, the frequency modulation processing of the fiber acousto-optic modulator 62 and the amplification of the double-clad fiber amplifier stage 63, an amplified laser is formed, and is output by the double-clad fiber amplifier stage 63 to the D end of the second fiber circulator 22, and is output from the E end of the second fiber circulator 22 to the second polarization-maintaining fiber polarization beam splitter 32. Since the amplified laser is still in the horizontal polarization direction, the second polarization-maintaining fiber polarization beam splitter 32 can transmit all the amplified second laser components to the fiber grating 5. The second laser component is in the horizontal polarization direction. The fiber grating 5 can reflect most of the optical signals of the second laser component to form a compressed laser, and transmit the compressed laser to the second polarization-maintaining fiber polarization beam splitter 32. Correspondingly, part of the optical signal of the second laser component passes through the fiber grating 5 and is deflected by the second Faraday rotator 42 and the first Faraday rotator 41 to become a laser with a vertical polarization direction, and then is transmitted from the idle end of the first polarization-maintaining fiber polarization beam splitter 31 to the first failure direction.The second polarization-maintaining fiber polarization beam splitter 32 can output the reflected compressed laser to the E end of the second fiber circulator 22. Finally, the compressed laser can be output from the F end of the second fiber circulator 22.

[0102] Fig. 9 A schematic diagram of the optical path of a picosecond pulse fiber amplifier provided in one embodiment of this specification is shown in FIG. Fig. 9 As shown, the dashed line in the form of a line segment represents the optical path from which the initial laser is processed into a compressed laser and output, and the dotted dashed line represents the optical signal output from the idle end.

[0103] Preferably, the B end of the first fiber circulator and / or the fiber grating and / or the D end of the second fiber circulator and / or the E end of the second fiber circulator and / or the second polarization-maintaining fiber polarization beam splitter and / or the optical fiber of the double-clad fiber amplifier stage use polarization-maintaining fibers with the same core diameter, and the core diameter of the polarization-maintaining fibers is between 10µm and 30µm.

[0104] Preferably, the fiber grating is a chirped grating, which can provide positive dispersion for forward incident light and negative dispersion for reverse incident light. The light incident from the direction of the fiber Faraday rotation structure is forward incident light, and the light incident from the direction of the second polarization-maintaining fiber polarization beam splitter is reverse incident light.

[0105] The following is an example description of the parameters of the various components of the picosecond pulse fiber amplifier: The polarization-maintaining fiber picosecond mode-locked oscillator 1 can provide an initial laser with a pulse width of 15 ps, a wide spectrum bandwidth of 0.3 nm, a repetition rate of 20 MHz, and a power of 20 mW. The pulse energy of the initial laser is 1 nJ, and the polarization state is a horizontal polarization state.

[0106] The parameters of the fiber grating 5 are D=1200ps / nm, reflectivity 85%, bandwidth 2nm, and the pigtail is a PM 14 / 125 double-clad passive fiber. The extended pulse width of the second deflected laser detected from the C end of the first fiber circulator 21 is 360ps, and 15% of the optical signal transmitted from the fiber grating 5 is output from the idle end of the second polarization-maintaining fiber polarization beam splitter 32 to the second failure direction.

[0107] The single-mode fiber amplifier stage 61 is a first-stage polarization-maintaining single-mode amplifier, and the gain fiber is a 10 / 125 single-clad gain fiber, which can amplify the power of the second deflected laser to 250 mW, and the pulse energy is 12.5 nJ.

[0108] The fiber acousto-optic modulator 62 can reduce the repetition rate of the second deflected laser to 200 kHz and the power to 1.25 mW.

[0109] The double-clad fiber amplifier stage 63 is a PM 14 / 125 double-clad pump fiber amplifier, which can amplify the power of the second deflected laser to 250 mW and the pulse energy to 1.25 µJ to form an amplified laser.

[0110] Due to the insertion loss of the fiber Bragg grating 5, the second fiber circulator 22, and the second polarization-maintaining fiber polarization beam splitter 32, the signal energy of the compressed laser finally output is 1µJ, the pulse width is 22ps, and the pulse energy is significantly increased from the initial 1nJ to 1µJ.

[0111] Preferably, a fiber Bragg grating 5, a double-clad fiber amplifier stage 63, a second fiber circulator 22, and a second polarization-maintaining fiber polarization beam splitter 32 with larger dispersion parameters can be selected, and a double-clad fiber with a larger core diameter (such as a double-clad fiber with a diameter of 20µm) can be used to further improve the pulse energy of the compressed laser.

[0112] Preferably, the picosecond pulse fiber amplifier can be applied to the 1064 nm band.

[0113] Of course, the picosecond pulse fiber amplifier is also applicable to other wavelength bands emitted by ytterbium-doped optical fibers (such as 1030 nm) and other wavelength bands generated by fiber lasers doped with erbium, thulium, holmium, neodymium, etc. This specification does not limit the wavelength of the initial laser.

[0114] The above is a picosecond pulse fiber amplifier provided in one or more embodiments of this specification. Based on the same idea, this specification also provides a corresponding laser.

[0115] Preferably, the laser includes the picosecond pulse fiber amplifier provided by any one of the above embodiments.

[0116] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0117] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.

[0118] The above description is only an embodiment of this specification and is not intended to limit this specification. For those skilled in the art, this specification may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this specification should be included in the scope of the claims of this application.

Claims

1. A picosecond pulse fiber amplifier, characterized in that: It includes a polarization-maintaining fiber picosecond mode-locked oscillator, a first fiber circulator, a first polarization-maintaining fiber polarization beam splitter, a fiber Faraday rotation structure, a second polarization-maintaining fiber polarization beam splitter, a second fiber circulator, a fiber Bragg grating, and an amplification frequency modulation component; The first optical fiber circulator is configured with an A end, a B end and a C end, and the light input from the A end is output from the B end, and the light input from the B end is output from the C end; The second optical fiber circulator is configured with a D end, an E end and an F end, and the light input from the D end is output from the E end, and the light input from the E end is output from the F end; The polarization-maintaining fiber picosecond mode-locked oscillator, the first fiber circulator, the first polarization-maintaining fiber polarization beam splitter, the fiber Faraday rotation structure, the fiber grating, the second polarization-maintaining fiber polarization beam splitter and the second fiber circulator are connected in sequence through optical fibers; and the first fiber circulator, the amplifying frequency modulation component and the second fiber circulator are connected in sequence through optical fibers; wherein the A end, the B end and the C end of the first fiber circulator are respectively connected to the polarization-maintaining fiber picosecond mode-locked oscillator, the first polarization-maintaining fiber polarization beam splitter and the amplifying frequency modulation component; and the D end and the E end of the second fiber circulator are respectively connected to the amplifying frequency modulation component and the second polarization-maintaining fiber polarization beam splitter.

2. The picosecond pulse fiber amplifier according to claim 1, characterized in that: The initial laser output by the polarization-maintaining optical fiber picosecond mode-locked oscillator is a picosecond-level pulsed laser.

3. The picosecond pulse fiber amplifier according to claim 2, characterized in that: The initial laser is linearly polarized light, and the polarization direction is horizontal polarization direction; The first polarization-maintaining optical fiber polarization beam splitter can transmit the component of the incident light with a horizontal polarization direction to the optical fiber Faraday rotation structure, and can transmit the component of the incident light with a vertical polarization direction to the first failure direction; the vertical polarization direction is perpendicular to the horizontal polarization direction; The second polarization-maintaining optical fiber polarization beam splitter can transmit the component of the incident light with a horizontal polarization direction to the optical fiber grating, and can transmit the component of the incident light with a vertical polarization direction to a preset second failure direction; The optical fiber Faraday rotation structure can deflect the polarization direction of light passing through it by 90 degrees.

4. The picosecond pulse fiber amplifier according to claim 3, characterized in that: The initial laser light emitted by the polarization-maintaining fiber picosecond mode-locked oscillator with a horizontal polarization direction can be transmitted along the first fiber circulator, the first polarization-maintaining fiber polarization beam splitter, the fiber Faraday rotation structure, the fiber grating, the fiber Faraday rotation structure, the first polarization-maintaining fiber polarization beam splitter, the first fiber circulator, the amplification frequency modulation component, the second fiber circulator, the second polarization-maintaining fiber polarization beam splitter, the fiber grating, the second polarization-maintaining fiber polarization beam splitter, and the second fiber circulator, and outputted through the F end of the second fiber circulator; The fiber grating is used to perform pulse broadening on the incident light transmitted from the direction of the fiber Faraday rotation structure, and reflect the light that has completed pulse broadening to the fiber Faraday rotation structure; the fiber grating is also used to perform pulse compression on the incident light transmitted from the direction of the second polarization-maintaining fiber polarization beam splitter, and reflect the light that has completed pulse compression to the second polarization-maintaining fiber polarization beam splitter.

5. The picosecond pulse fiber amplifier according to any one of claims 1 to 4, characterized in that: The amplification frequency modulation component comprises a single-mode fiber amplifier stage, a fiber acousto-optic modulator and a double-clad fiber amplifier stage which are sequentially connected via optical fibers.

6. The picosecond pulse fiber amplifier according to claim 5, characterized in that: The A end and the C end of the first optical fiber circulator are both polarization-maintaining single-mode optical fibers; The B end of the first fiber circulator and / or the fiber grating and / or the D end of the second fiber circulator and / or the E end of the second fiber circulator and / or the second polarization-maintaining fiber polarization beam splitter and / or the optical fiber of the double-clad fiber amplifier stage use polarization-maintaining passive optical fibers with the same core diameter, and the core diameter of the polarization-maintaining optical fiber is between 10µm and 30µm.

7. The picosecond pulse fiber amplifier according to any one of claims 1 to 4, characterized in that: The fiber grating is a chirped grating, which can provide positive dispersion for forward incident light and negative dispersion for reverse incident light; The light incident from the direction of the optical fiber Faraday rotation structure is forward incident light; the light incident from the direction of the second polarization-maintaining optical fiber polarization beam splitter is reverse incident light.

8. The picosecond pulse fiber amplifier according to any one of claims 1 to 4, characterized in that: The reflectivity of the fiber grating is greater than or equal to 70%.

9. The picosecond pulse fiber amplifier according to claim 5, characterized in that: The single-mode optical fiber amplifier stage is a single-stage or multi-stage single-mode optical fiber amplifier structure, and the pumping mode is forward core pumping or backward core pumping; The double-clad optical fiber amplifier stage is multi-mode semiconductor laser cladding pumped, and the gain optical fiber is a double-clad optical fiber with a core diameter of 10µm-30µm.

10. A laser, characterized in that: The laser comprises the picosecond pulse fiber amplifier according to any one of claims 1 to 9.

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