GHz femtosecond pulse laser generating device

Abstract

The utility model provides a GHz femtosecond pulse laser generating device which comprises a low-frequency femtosecond pulse laser generating assembly and at least two repetition frequency multiplication units. Each repetition frequency multiplication unit comprises a polarization beam splitter, an optical fiber delay line and a polarization beam combiner, input light of the repetition frequency multiplication units is divided into two paths of linearly polarized light through the polarization beam splitters, one path of linearly polarized light directly enters the polarization beam combiners, and the other path of linearly polarized light enters the polarization beam combiners through the optical fiber delay lines; and the two paths of linearly polarized light are output after being subjected to polarization beam combination in the polarization beam splitter. According to the utility model, by adopting an extra-cavity repetition frequency multiplication mode of polarization beam splitting and beam combination, the problems that the femtosecond GHz pulse directly output by the laser is difficult to weld due to too short optical fiber length and the stability of the solid laser is poor are solved, and the problems that the pulse is uneven due to cascade frequency multiplication through a coupler and the power is reduced due to the addition of an attenuator are solved; and low noise, high stability, long service life and all-fiber output of the GHz femtosecond laser are realized.

Description

Technical Field

[0001] The utility model belongs to the technical field of laser pulse signal control, and in particular relates to a GHz femtosecond pulse laser generating device. Background Art

[0002] Femtosecond lasers, with their ultrashort pulse width and extremely high peak intensity, can achieve cold processing by suppressing the heat-affected zone, opening up new avenues for material processing. They are currently widely used in polymer material processing and treatment, ceramic and polymer processing, semiconductor wafer processing, new energy material processing, and transparent material welding. However, their slow processing speed limits their industrial applications. GHz femtosecond lasers offer an excellent solution to this problem. GHz femtosecond lasers operating in burst mode can significantly improve processing efficiency without compromising processing quality. GHz femtosecond lasers combine the advantages of traditional femtosecond lasers with those of high repetition rates, further expanding their industrial application scenarios.

[0003] Currently, methods for obtaining high-repetition-rate GHz femtosecond pulses fall into two main categories. One is through passive mode locking. For a passively mode-locked laser to output GHz-repetition-rate pulses, the length of its resonant cavity must be very short (approximately less than 15 cm). Chinese patent CN112864785B discloses a high-power GHz-repetition-rate femtosecond laser generation system that uses a solid-state laser to produce GHz femtosecond pulses. However, this method suffers from poor output stability due to the solid-state resonant cavity mode locking, which is prone to loss of lock. Furthermore, the spatial output is difficult to use for fiber amplification. Another method is to achieve repetition rate multiplication through extracavity repetition rate multiplication. The common method is to achieve repetition rate multiplication through coupler splitting. However, the coupler method is prone to uneven output pulses due to different splitting ratios, resulting in different energies of single femtosecond laser pulses. Chinese patent CN116053918A discloses a GHz high-frequency femtosecond pulse generation device and method. In this patent, low-frequency femtosecond pulses are generated through passive mode locking of SESAM (saturable absorber mirror), cascaded couplers are used for frequency multiplication, and an attenuator is added to control the smoothness of the pulse. However, the attenuator will introduce extra loss, reducing the output power. At the same time, the SESAM is easily damaged during long-term use, resulting in a short service life of the entire laser. Utility Model Content

[0004] The purpose of the utility model is to provide a GHz femtosecond pulse laser generating device, which can at least solve some of the defects in the prior art.

[0005] In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0006] A GHz femtosecond pulse laser generating device comprises a low-frequency femtosecond pulse laser generating component and at least two repetition rate multiplication units arranged in sequence along the output light path of the low-frequency femtosecond pulse laser generating component; each of the repetition rate multiplication units comprises a polarization beam splitter, an optical fiber delay line and a polarization beam combiner; the input light of the repetition rate multiplication unit is split into two paths of polarized light by the polarization beam splitter, one path directly enters the polarization beam combiner, and the other path enters the polarization beam combiner through the optical fiber delay line; the two paths of polarized light are polarization-combined in the polarization beam combiner and then output.

[0007] Furthermore, the low-frequency femtosecond pulse laser generating assembly includes a polarization-maintaining fiber Bragg grating (FBG), a 1*2 polarization-maintaining coupler, a polarization-maintaining gain fiber, a polarization-maintaining wavelength division multiplexer (PMWDM), a semiconductor pump laser, and a polarization-maintaining phase shifter. The two arms on one side of the 1*2 PM coupler are sequentially connected to the polarization-maintaining gain fiber, the PM WDM, and the PM WDM to form a ring loop. The other side of the 1*2 PM coupler is connected to the polarization-maintaining fiber Bragg grating (FBG) to form a linear loop. The semiconductor pump laser is connected to the PM WDM, and the output end of the PM fiber Bragg grating is connected to the repetition rate multiplication unit.

[0008] Furthermore, the low-frequency femtosecond pulse laser generating component is a linearly polarized output femtosecond oscillator with a central wavelength of 1030nm or 1064nm, a repetition frequency of 30-250MHz, an output power of 1-300mW, and a pulse width of 100fs-15ps.

[0009] Furthermore, the two polarized lights separated by the polarization beam splitter are p-polarized light and s-polarized light that are perpendicular to each other.

[0010] Furthermore, the polarization beam splitter includes a first collimator, a first half-wave plate, a polarization beam splitting prism, a second collimator, and a third collimator. The input light of the repetition rate multiplication unit passes through the first collimator and the first half-wave plate in sequence and is then split into two paths by the polarization beam splitting prism, and is output after passing through the second collimator and the third collimator respectively.

[0011] Furthermore, a knob for adjusting the angle of the first half-wave plate inside the polarization beam splitter is provided outside the polarization beam splitter.

[0012] Furthermore, the polarization combiner includes a fourth collimator, a second half-wave plate, a polarization combining prism, a fifth collimator, and a sixth collimator. The output light of the polarization beam splitter and the optical fiber delay line passes through the fifth collimator and the sixth collimator respectively and then is combined by the polarization combining prism. The combined light passes through the second half-wave plate and the fourth collimator in sequence and is output.

[0013] Furthermore, a knob for adjusting the angle of the second half-wave plate inside the polarization beam combiner is provided outside the polarization beam combiner.

[0014] Furthermore, the optical fiber delay line is a single-mode polarization-maintaining optical fiber with an optical fiber mode field diameter of 6-10 μm.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] (1) The GHz femtosecond pulse laser generating device provided by the present invention solves the problem of the difficulty in directly outputting femtosecond GHz pulses due to the short length of the optical fiber and the poor stability of the solid laser by adopting the extracavity repetition frequency multiplication method of polarization splitting and combining. At the same time, it solves the problem of uneven pulses caused by cascading frequency doubling through a coupler and power reduction caused by adding an attenuator, thereby achieving low noise, high stability, long life and all-fiber output of the GHz femtosecond laser.

[0017] (2) The GHz femtosecond pulse laser generating device provided by the present invention can achieve higher repetition frequency pulse output by cascading more repetition frequency multiplication units. By utilizing polarization beam splitters and combiners, GHz output with highly consistent pulses can be achieved without causing additional damage. At the same time, the splitting ratio of the polarization beam splitter in the repetition frequency multiplication unit can be adjusted without changing the power to achieve lossless switching between high and low frequencies. Subsequently, optical fiber amplification is used to achieve high-power output while sharing multiple frequencies.

[0018] (3) The GHz femtosecond pulse laser generating device provided by the present invention adopts a passively mode-locked femtosecond oscillator based on a nonlinear amplifying ring mirror as a low-frequency pulse signal. This new all-fiber 9-shaped seed source based on nonlinear effects does not have a SESAM device and has the advantages of low noise, high stability, long life, and high repetition rate.

[0019] The present invention will be described in further detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic structural diagram of the GHz femtosecond pulse laser generating device of the present invention;

[0021] Figure 2 2 is a schematic structural diagram of a polarization beam splitter in an embodiment of the present utility model;

[0022] Figure 3 It is a structural schematic diagram of the polarization beam combiner in an embodiment of the present utility model.

[0023] Explanation of reference numerals: 1. low-frequency femtosecond pulse laser generating assembly; 2. first repetition rate multiplication unit; 3. second repetition rate multiplication unit; 110. polarization-maintaining fiber Bragg grating; 120. 1*2 polarization-maintaining coupler; 130. polarization-maintaining gain fiber; 140. polarization-maintaining wavelength division multiplexer; 150. semiconductor pump laser; 160. polarization-maintaining phase shifter; 210. first polarization beam splitter; 211. first collimator; 212. first half-wavelength multiplexer Plate; 213, polarization beam splitter prism; 214, second collimator; 215, third collimator; 220, first optical fiber delay line; 230, first polarization beam combiner; 231, fourth collimator; 232, second half-wave plate; 233, polarization beam combiner prism; 234, fifth collimator; 235, sixth collimator; 310, second polarization beam splitter; 320, second optical fiber delay line; 330, second polarization beam combiner. DETAILED DESCRIPTION

[0024] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0025] In the description of the present invention, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0026] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "install", "connect" and "connect" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, a conflicting connection or an integral connection. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0027] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the technical features indicated. Therefore, features specified as "first" or "second" may explicitly or implicitly include one or more of such features; and in the description of this utility model, unless otherwise specified, "plurality" means two or more.

[0028] like Figure 1 As shown, this embodiment provides a GHz femtosecond pulse laser generating device, comprising a low-frequency femtosecond pulse laser generating assembly 1, and at least two repetition rate multiplication units arranged in sequence along the output light path of the low-frequency femtosecond pulse laser generating assembly; each of the repetition rate multiplication units comprises a polarization beam splitter, an optical fiber delay line, and a polarization beam combiner. The input light of the repetition rate multiplication unit is divided into two polarized light paths by the polarization beam splitter, one of which directly enters the polarization beam combiner, and the other enters the polarization beam combiner through the optical fiber delay line. The two polarized light paths are polarization-combined in the polarization beam combiner before being output. This embodiment solves the problem of direct laser output of femtosecond GHz pulses, which is difficult to fuse due to the short length of the optical fiber, and the poor stability of the solid-state laser, by adopting an extracavity repetition rate multiplication method of polarization splitting and combining. It also solves the problem of uneven pulses caused by cascading frequency multiplication through a coupler and power reduction caused by adding an attenuator, thereby achieving low noise, high stability, long life, and all-fiber output of the GHz femtosecond laser.

[0029] Specifically, this embodiment is described by taking two repetition frequency multiplication units as an example, wherein the two repetition frequency multiplication units are respectively a first repetition frequency multiplication unit 2 and a second repetition frequency multiplication unit 3. The first repetition frequency multiplication unit 2 includes a first polarization beam splitter 210, a first optical fiber delay line 220 and a first polarization beam combiner 230, and the second repetition frequency multiplication unit 3 includes a second polarization beam splitter 310, a second optical fiber delay line 320 and a second polarization beam combiner 330. During operation, the low-frequency femtosecond pulse laser generating assembly 1 generates a femtosecond pulse signal which enters the first polarization beam splitter 210 and is divided into two mutually perpendicular polarized light paths of p and s. One path directly enters the first polarization beam combiner 230, and the other path passes through the first optical fiber delay line 220 and enters the first polarization beam combiner 230. The first optical fiber delay line 220 introduces a certain time delay, which is the pulse period corresponding to the pulse laser repetition frequency multiplication. The two paths of polarized light are polarized and combined in the first polarization beam combiner 230, and the repetition frequency of the femtosecond pulse signal is doubled. Then, the first The femtosecond pulse light signal output by the first polarization combiner 230 of the repetition rate multiplication unit 2 enters the second polarization beam splitter 310 and is divided into two mutually perpendicular polarized light paths, p and s. One path directly enters the second polarization combiner 330, and the other path passes through the second optical fiber delay line 320 and enters the second polarization combiner 330. Similarly, the second optical fiber delay line 320 introduces a certain time delay, which is the pulse period corresponding to the pulse laser repetition rate multiplication. The two paths of polarized light are polarized and combined in the second polarization combiner 330, and the repetition rate of the femtosecond pulse light signal is doubled again. For example, the low-frequency femtosecond pulse laser generating assembly 1 outputs a low-frequency pulse signal with a repetition rate of 250MHz. After passing through the repetition rate multiplication unit of the same principle twice in this embodiment, a 1GHz femtosecond pulse output is achieved. Similarly, this embodiment can also achieve a higher repetition rate pulse output by cascading more repetition rate multiplication units.

[0030] As a specific implementation method, Figure 1As shown, the low-frequency femtosecond pulse laser generating assembly 1 includes a polarization-maintaining fiber Bragg grating 110, a 1*2 polarization-maintaining coupler 120, a polarization-maintaining gain fiber 130, a polarization-maintaining wavelength division multiplexer 140, a semiconductor pump laser 150 and a polarization-maintaining phase shifter 160. The two arms on one side of the 1*2 polarization-maintaining coupler 120 are connected in sequence to the polarization-maintaining gain fiber 130, the polarization-maintaining wavelength division multiplexer 140 and the polarization-maintaining phase shifter 160 to form a ring loop. The other side of the 1*2 polarization-maintaining coupler 120 is connected to the polarization-maintaining fiber Bragg grating 110 to form a linear loop. The semiconductor pump laser 150 is connected to the polarization-maintaining wavelength division multiplexer 140, and the output end of the polarization-maintaining fiber Bragg grating 110 is connected to the input end of the repetition rate multiplication unit. In this embodiment, the ring loop and the linear loop are combined to form a laser oscillator, and passive mode locking is achieved by introducing a linear phase shift and an asymmetrically distributed nonlinear amplifying ring mirror, thereby achieving stable and reliable femtosecond pulse laser output; this low-frequency femtosecond pulse laser generating component of this embodiment is based on a new type of all-fiber 9-shaped seed source SESAM device based on nonlinear effects, and has the advantages of low noise, high stability, long life, and high repetition rate.

[0031] Specifically, the low-frequency femtosecond pulse laser generating component 1 is a linearly polarized output femtosecond oscillator with a central wavelength of 1030nm or 1064nm, a repetition frequency of 30-250MHz, an output power of 1-300mW, and a pulse width of 100fs-15ps.

[0032] As a specific implementation method, Figure 2 As shown, the polarization beam splitter includes a first collimator 211, a first half-wave plate 212, a polarization beam splitting prism 213, a second collimator 214, and a third collimator 215. The input light of the repetition rate multiplication unit passes through the first collimator 211 and the first half-wave plate 212 in sequence, and is then split into two paths by the polarization beam splitting prism 213. The two paths are respectively output after passing through the second collimator 214 and the third collimator 215, thereby realizing polarization beam splitting of the femtosecond pulse laser. Figure 3 As shown, the structure of the polarization beam combiner is the same as that of the polarization beam splitter, specifically including a fourth collimator 231, a second half-wave plate 232, a polarization beam combining prism 233, a fifth collimator 234, and a sixth collimator 235. The output light of the polarization beam splitter and the optical fiber delay line passes through the fifth collimator 234 and the sixth collimator 235 respectively and then is combined by the polarization beam combining prism 233. The combined light passes through the second half-wave plate 232 and the fourth collimator 231 in sequence and is then output, thereby realizing polarization combining of the femtosecond pulse laser.

[0033] Among them, the polarization beam splitter can control the power of two mutually perpendicular linear polarized lights p and s by adjusting the first half-wave plate 212, so as to achieve highly consistent light pulses and constant power without introducing additional attenuation; specifically, a knob is provided on the outside of the polarization beam splitter to adjust the angle of the first half-wave plate 212 inside it. Similarly, a knob is provided on the outside of the polarization beam combiner for adjusting the angle of the second half-wave plate 232 inside it. This embodiment utilizes polarization beam splitting and beam combiners to achieve GHz output with consistent pulse height without additional damage. At the same time, the splitting ratio of the polarization beam splitter in the repetition frequency multiplication unit can be adjusted without changing the power to achieve lossless switching between high and low frequencies. Fiber amplification is subsequently used to achieve high-power output while sharing multiple frequencies.

[0034] Optionally, the optical fiber delay line adopts a single-mode polarization-maintaining optical fiber with an optical fiber mode field diameter of 6-10 μm.

[0035] The above examples are merely illustrative of the present invention and do not limit the scope of protection of the present invention. Any design that is identical or similar to the present invention falls within the scope of protection of the present invention.

Claims

1. A GHz femtosecond pulse laser generating device, characterized in that: The invention comprises a low-frequency femtosecond pulse laser generating component and at least two repetition rate multiplication units arranged in sequence along the output light path of the low-frequency femtosecond pulse laser generating component; each of the repetition rate multiplication units comprises a polarization beam splitter, an optical fiber delay line and a polarization beam combiner; the input light of the repetition rate multiplication unit is divided into two paths of polarized light by the polarization beam splitter, one path directly enters the polarization beam combiner, and the other path enters the polarization beam combiner through the optical fiber delay line; the two paths of polarized light are polarized and combined in the polarization beam combiner before being output.

2. The GHz femtosecond pulse laser generator according to claim 1, wherein: The low-frequency femtosecond pulse laser generating assembly includes a polarization-maintaining fiber Bragg grating (FBG), a 1*2 polarization-maintaining coupler, a polarization-maintaining gain fiber, a polarization-maintaining wavelength division multiplexer (PMWDM), a semiconductor pump laser, and a polarization-maintaining phase shifter. The two arms on one side of the 1*2 PM coupler are sequentially connected to the polarization-maintaining gain fiber, the PM WDM, and the PM WDM to form a ring loop. The other side of the 1*2 PM coupler is connected to the polarization-maintaining fiber Bragg grating (FBG) to form a linear loop. The semiconductor pump laser is connected to the PM WDM, and the output end of the PM fiber Bragg grating is connected to the repetition rate multiplication unit.

3. The GHz femtosecond pulse laser generator according to claim 1 or 2, characterized in that: The low-frequency femtosecond pulse laser generating component is a linearly polarized output femtosecond oscillator with a central wavelength of 1030nm or 1064nm, a repetition frequency of 30-250MHz, an output power of 1-300mW, and a pulse width of 100fs-15ps.

4. The GHz femtosecond pulse laser generator according to claim 1, wherein: The two polarized lights separated by the polarization beam splitter are p-polarized light and s-polarized light that are perpendicular to each other.

5. The GHz femtosecond pulse laser generator according to claim 1, wherein: The polarization beam splitter includes a first collimator, a first half-wave plate, a polarization beam splitting prism, a second collimator, and a third collimator. The input light of the repetition rate multiplication unit passes through the first collimator and the first half-wave plate in sequence, and is then split into two paths by the polarization beam splitting prism, and is output after passing through the second collimator and the third collimator respectively.

6. The GHz femtosecond pulse laser generator according to claim 5, characterized in that: The polarization beam splitter is provided with a knob on the outside for adjusting the angle of the first half-wave plate inside the polarization beam splitter.

7. The GHz femtosecond pulse laser generator according to claim 1, wherein: The polarization beam combiner includes a fourth collimator, a second half-wave plate, a polarization beam combining prism, a fifth collimator, and a sixth collimator. The output light of the polarization beam splitter and the optical fiber delay line passes through the fifth collimator and the sixth collimator respectively and then is combined by the polarization beam combining prism. The combined light passes through the second half-wave plate and the fourth collimator in sequence and is then output.

8. The GHz femtosecond pulse laser generator according to claim 7, wherein: The polarization beam combiner is provided with a knob on the outside for adjusting the angle of the second half-wave plate inside the polarization beam combiner.

9. The GHz femtosecond pulse laser generator according to claim 1, wherein: The optical fiber delay line is a single-mode polarization-maintaining optical fiber with an optical fiber mode field diameter of 6-10 μm.

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