Rectangular pulse light generator and method thereof

Abstract

The invention discloses a rectangular pulse optical generator and a method thereof, comprising a first pulse generating unit with a narrow line width, a second pulse generating unit, a first power regulating unit, a second power regulating unit, an optical path merging unit, an optical coupling unit, and a resonance unit. By setting a first pump light with a narrow line width to meet a coherence condition, and then coherently driving the first pump light with the second pump light, power oscillation in the resonance unit is realized, and the power steady state in the resonance cavity is ensured. Finally, the pulse in the resonance cavity generates a steady state and outputs a rectangular pulse. Further, by adjusting the power of the first pump light and the second pump light, the pulse width of the output rectangular pulse is regulated. In addition, the optical generator structure and the regulating principle are relatively simple, and the complexity and maintenance cost of the system are reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of rectangular pulse light generation, in particular to a rectangular pulse light generator and a method thereof. Background Art

[0002] Rectangular pulse light has important applications in all-optical square wave clock detection, laser micro-machining, distance measurement, sensing and other technical fields, and has become one of the research hotspots in laser physics.

[0003] At present, the common method of generating rectangular pulse light is to use the mode-locking technology to generate nanosecond-scale rectangular pulses through the fiber laser under specific resonant cavity parameter conditions. The rectangular pulse can increase its pulse width as the pump power increases while keeping its amplitude unchanged. There are two main implementation mechanisms: one is to obtain rectangular pulses using dissipative soliton resonance. The rectangular pulse formed is a single pulse with no fine structure inside the pulse and high coherence. The other is to obtain rectangular pulses using the peak power clamping effect of the laser cavity. The typical example is a rectangular noise-like pulse. Its pulse behavior is similar to that of the dissipative soliton resonance pulse. The difference is that it is a special pulse with partial coherence. It is essentially a chaotic wave packet composed of a large number of randomly changing small pulses and lacks time coherence.

[0004] When in use, the mode-locking technology requires the use of technologies or devices such as real saturable absorbers, nonlinear polarization rotation technology, "8"-shaped cavities, Mamyshev regenerators, and multimode fiber hybrid structures. The pulse shape is formed through modulation (such as external modulation or feedback control). Precision optical components and specific structures (such as modulators and filters) are also required, which will increase the overall complexity and maintenance costs of the system. In addition, due to the influence of nonlinear effects and gain saturation effects, the pulse width and intensity may fluctuate, resulting in poor stability and reliability of the pulse light source. At the same time, the energy distribution of the generated rectangular pulse is uneven, and the energy at the edge is low, which makes it difficult to maintain long-term stability of the rectangular pulse shape, and it is easily affected by environmental changes and intracavity losses, thereby affecting the consistency of the output quality.

[0005] The object of the present invention is to provide a rectangular pulse light generator and method thereof which can solve at least one of the above problems. Summary of the invention

[0006] In order to solve the above technical defects, the technical solution adopted by the present invention is to provide a rectangular pulse light generator, including a first pulse generating unit with a narrow line width, and a second pulse generating unit, a first power regulating unit, a second power regulating unit, an optical path merging unit, an optical coupling unit, and a resonance unit, wherein the first pulse generating unit is connected to the optical path merging unit via the first power regulating unit, and the second pulse generating unit is connected to the optical path merging unit via the second power regulating unit, and the optical path merging unit, the optical coupling unit and the resonance unit are arranged in sequence;

[0007] The first pulse generating unit generates a first pump light, and the second pulse generating unit generates a second pump light. The first pump light is adjusted in power within a first set power range by a first power regulating unit, and the second pump light is adjusted in power within a second set power range by a second power regulating unit. The first pump light and the second pump light are output to an optical path merging unit for beam combining, and the combined pump light is coupled to a resonance unit via an optical coupling unit to generate a rectangular pulse with a set pulse width.

[0008] Furthermore, the first pump light is a continuous laser, and the second pump light is a pulsed laser.

[0009] Furthermore, the first power adjustment unit increases the output power of the first pump light within a first set power range, and the second power adjustment unit increases the output power of the second pump light within a second set power range.

[0010] Furthermore, the first set power range is 2.46W-2.63W, the second set power range is 1W-17W, and the set pulse width is 1.11ps-9.49ps.

[0011] Further, the first pulse generating unit is one of a narrow linewidth fiber laser, a narrow linewidth semiconductor laser, and a narrow linewidth solid laser;

[0012] The second pulse generating unit is one of a fiber laser, a semiconductor laser, and a solid laser;

[0013] The first power adjustment unit is one of an optical fiber amplifier, a semiconductor optical amplifier, and a solid optical amplifier;

[0014] The second power adjustment unit is one of an optical fiber amplifier, a semiconductor optical amplifier, and a solid optical amplifier;

[0015] The optical path merging unit is one of a beam splitter, an optical fiber wavelength division multiplexer, a dichroic mirror, or any combination thereof;

[0016] The optical coupling unit is a fiber coupler or a beam splitter, or a combination thereof;

[0017] The resonance unit is a nonlinear optical fiber resonant cavity or a waveguide microcavity, or a combination thereof.

[0018] Furthermore, the first pulse generating unit is a continuous fiber laser with a central wavelength of 1555 nm and an output power of 2.46 W;

[0019] The second pulse generating unit is a short pulse fiber laser with a central wavelength of 1550 nm, a pulse width of 1.8 ps, and a peak power of 1 W;

[0020] The first power regulating unit and the second power regulating unit are both high-power erbium-doped fiber amplifiers;

[0021] The optical path merging unit is an optical fiber wavelength division multiplexer;

[0022] The optical coupling unit is a 2×2 type optical fiber coupler with a central wavelength of 1550nm and a coupling ratio of 50:50;

[0023] The resonance unit is composed of a high nonlinear optical fiber with a length of 100 m and an optical fiber isolator.

[0024] The present invention also provides a rectangular pulse light generating method, which is implemented by using the rectangular pulse light generator, and comprises the following steps:

[0025] The first pulse generating unit generates a first pump light;

[0026] The second pulse generating unit generates a second pump light;

[0027] adjusting the power of the first pump light by a first power adjustment unit, and adjusting the first pump light within a first set power range;

[0028] adjusting the power of the second pump light by a second power adjustment unit, and adjusting the second pump light within a second set power range;

[0029] Combining the first pump light with the second pump light into a light path merging unit for light path merging;

[0030] The pump light combined by the optical path is coupled into the resonance unit through the optical coupling unit;

[0031] The two pump lights are coherent in the resonant unit to generate rectangular pulses with different pulse widths.

[0032] Furthermore, the first pump light is a continuous laser, and the second pump light is a pulsed laser;

[0033] The method comprises the following steps: adjusting the power of the first pump light by a first power adjustment unit, and adjusting the first pump light within a first set power range; adjusting the power of the second pump light by a second power adjustment unit, and adjusting the second pump light within a second set power range.

[0034] First, the output power of the continuous laser is adjusted from the first set power to the second set power, and the peak power of the pulsed laser is kept at the third set power. At this time, the pulse width range of the rectangular pulse corresponds to the first set width to the second set width;

[0035] Then, when the output power of the continuous laser is the second set power, the peak power of the pulsed laser is adjusted from the third set power to the fourth set power. At this time, the pulse width range of the rectangular pulse corresponds to the second set width to the third set width.

[0036] Further, the first set power is 2.46W, the second set power is 2.63W, the third set power is 1W, the fourth set power is 17W, the first set width is 1.11ps, the second set width is 6.68ps, and the third set width is 9.49ps.

[0037] Compared with the prior art, the beneficial effects of the technical solution of the present invention are as follows:

[0038] The rectangular pulse optical generator and method provided by the present invention realize power oscillation in the resonance unit by setting a first pump light with a narrow line width to meet the coherence condition, and then coherently drive it with the second pump light to ensure the power steady state in the resonance cavity. Finally, the pulse of the resonance cavity generates a steady state and outputs a rectangular pulse. The pulse width of the output rectangular pulse is further adjusted by adjusting the power of the first pump light and the second pump light. The structure of the optical generator and the adjustment principle are relatively simple, which reduces the complexity and maintenance cost of the system.

[0039] In addition, there is no need to dynamically adjust the modulator and filter in the cavity to achieve the pulse shape formation, and stable rectangular pulse light can be generated. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0041] Figure 1 is a principle diagram of an optical path of a rectangular pulse light generator provided by an embodiment of the present invention;

[0042] Figure 2 It is a schematic diagram of the steps of a rectangular pulse light generating method provided by an embodiment of the present invention;

[0043] Figure 3 It is a schematic diagram of the relationship between the pulse width and peak power of a rectangular pulse;

[0044] Figure 4 It is a schematic diagram of the relationship between the output power of a continuous laser and the pulse width of a rectangular pulse;

[0045] Figure 5 It is a schematic diagram of the relationship between the peak power of the pulsed laser and the pulse width of the rectangular pulse;

[0046] Figure 6 This is a schematic diagram of the relationship between the output power of a continuous laser and the peak power of a rectangular pulse.

[0047] The reference numerals are as follows:

[0048] 1. A first pulse generating unit, 2. A second pulse generating unit, 3. A first power regulating unit, 4. A second power regulating unit, 5. An optical path merging unit, 6. An optical coupling unit, 7. A resonance unit. DETAILED DESCRIPTION

[0049] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0050] Example 1

[0051] See also Figure 1 As shown, the rectangular pulse optical generator provided by the present invention comprises a first pulse generating unit 1 with narrow line width, a second pulse generating unit 2, a first power regulating unit 3, a second power regulating unit 4, an optical path merging unit 5, an optical coupling unit 6, and a resonance unit 7. The first pulse generating unit 1 is connected to the optical path merging unit 5 via the first power regulating unit 3, and the second pulse generating unit 2 is connected to the optical path merging unit 5 via the second power regulating unit 4. The optical path merging unit 5, the optical coupling unit 6, and the resonance unit 7 are arranged in sequence. Among them, the left and right positions of the first pulse generating unit 1 and the second pulse generating unit 2 relative to the optical path merging unit 5 are only for illustration and are not intended to be limiting. The positions of the two may also be swapped.

[0052] The first pulse generating unit 1 generates a first pump light, i.e., a continuous laser, and the second pulse generating unit 2 generates a second pump light, i.e., a pulsed laser. The first pump light is adjusted in power within a first set power range by the first power adjusting unit 3, and the second pump light is adjusted in power within a second set power range by the second power adjusting unit 4. The first pump light and the second pump light are output to the optical path combining unit 5 for beam combining, and the combined pump light is coupled to the resonance unit 7 by the optical coupling unit 6 to generate a rectangular pulse with a set pulse width.

[0053] The first pulse generating unit 1 is one of a narrow-linewidth optical fiber laser, a narrow-linewidth semiconductor laser, and a narrow-linewidth solid-state laser; the second pulse generating unit 2 is one of an optical fiber laser, a semiconductor laser, and a solid-state laser; the first power regulating unit 3 and the second power regulating unit 4 are both one of an optical fiber amplifier, a semiconductor optical amplifier, and a solid-state optical amplifier, or any combination thereof; the optical path merging unit 5 is one of a beam splitter, an optical fiber wavelength division multiplexer, and a dichroic mirror, or any combination thereof; the optical coupling unit 6 is an optical fiber coupler or a beam splitter, or a combination of the two; the resonance unit 7 is a nonlinear optical fiber resonant cavity or a waveguide microcavity, or a combination of the two.

[0054] The first pulse generating unit 1 is a continuous fiber laser with a central wavelength of 1555 nm and an output power of 2.46 W; the second pulse generating unit 2 is a short pulse fiber laser with a central wavelength of 1550 nm, a pulse width of 1.8 ps, and a peak power of 1 W. The first power regulating unit 3 and the second power regulating unit 4 are both high-power erbium-doped fiber amplifiers; in actual use, the output power of the power regulating unit is higher than the input power of the corresponding pump light. Based on the input power, the power regulating unit can directly increase the input power of the pump light to the set value, or increase the power first and then reduce the power to the set value to meet the power adjustment requirements. The optical path merging unit 5 is a fiber wavelength division multiplexer; the optical coupling unit 6 is a 2×2 type fiber coupler with a central wavelength of 1550 nm and a coupling ratio of 50:50. The resonant unit 7 is composed of a 100m long high nonlinear optical fiber and an optical fiber isolator, which is used to convert the combined laser into a soliton pulse group. The soliton type is a dissipative soliton. The pump gain is balanced with the loss of the resonant unit 7. The laser beam enters the high nonlinear optical fiber, and a balance is achieved between dispersion and the nonlinear Kerr effect. The above units form a rectangular pulse light generator through optical fiber fusion or optical path construction. The generated rectangular pulses can theoretically exist stably in the nonlinear optical fiber resonant cavity for a long time.

[0055] In this embodiment, the first power adjustment unit 3 increases the output power of the first pump light within a first set power range, and the second power adjustment unit 4 increases the output power of the second pump light within a second set power range. The first set power range is 2.46W-2.63W, the second set power range is 1W-17W, and the set pulse width is 1.11ps-9.49ps.

[0056] When in use, the output power of the continuous laser is first increased linearly from 2.46W to 2.63W, the peak power of the pulsed laser is kept at 1W, and the set pulse width of the output rectangular pulse is 1.11ps-6.68ps; then when the output power of the continuous laser is 2.63W, the peak power of the pulsed laser is linearly increased from 1W to 17W, so that the set pulse width of the output rectangular pulse is 6.68ps-9.49ps.

[0057] like Figure 2 As shown, the present invention also provides a rectangular pulse light generating method, which is implemented by using the above-mentioned rectangular pulse light generator, and includes the following steps:

[0058] The first pulse generating unit 1 generates a first pump light, i.e., a continuous laser;

[0059] The second pulse generating unit 2 generates a second pump light, i.e., a pulse laser;

[0060] The power of the first pump light is adjusted by the first power adjustment unit 3, and the first pump light is adjusted within a first set power range;

[0061] The power of the second pump light is adjusted by the second power adjustment unit 4, and the second pump light is adjusted within a second set power range;

[0062] Combining the first pump light with the second pump light into a light path merging unit 5 for light path merging;

[0063] The pump light after optical path merging is coupled into the resonance unit 7 through the optical coupling unit 6;

[0064] The two pump lights are coherent in the resonance unit 7 to generate rectangular pulses with different pulse widths.

[0065] Preferably, the power of the first pump light is adjusted by the first power adjustment unit 3, and the first pump light is adjusted within a first set power range; the power of the second pump light is adjusted by the second power adjustment unit 4, and the second pump light is adjusted within a second set power range, including the following steps:

[0066] First, the output power of the continuous laser is linearly adjusted from the first set power to the second set power, and the peak power of the pulsed laser remains unchanged at the third set power. At this time, the pulse width range of the rectangular pulse corresponds to the first set width to the second set width.

[0067] In this embodiment, the first set power range includes the first set power, the second set power and the power value between the two. The first set power is 2.46W, and the second set power is 2.63W, that is, the first set power range is 2.46W-2.63W; the first set width is 1.11ps, and the second set width is 6.68ps. At this time, the corresponding pulse width range includes the first set width, the second set width and the width value between the two, that is, the corresponding pulse width range is 1.11ps-6.68ps.

[0068] The present invention utilizes coherent pumping to convert the increase of pump light power into an increase of the pulse width of rectangular pulses in the nonlinear optical fiber resonant cavity, which is similar to the phenomenon of dissipative soliton resonance of a laser in principle, but the pulse width control is different from that of the dissipative soliton resonance in the resonant cavity. Its pulse width does not change linearly, and the amplitude also changes.

[0069] Specific from Figure 3 It can be seen from the figure that the pulse width of the rectangular pulse increases slowly at first, and then increases rapidly around the time when the peak power reaches the equilibrium threshold. This is because although the coherent pumping forms a rectangular pulse in the nonlinear fiber resonant cavity, a part of the output power of the continuous laser will be converted into the background field of the continuous laser and cannot be completely converted into the output rectangular pulse, resulting in a slow increase in the pulse width of the rectangular pulse. When the background field of the continuous laser reaches the equilibrium threshold, the pulse width of the output rectangular pulse increases rapidly.

[0070] For ease of understanding, the rectangular pulses in the figure only select a few points where the pulse width changes before and after the background field of the continuous laser reaches the equilibrium threshold, and do not illustrate all rectangular pulses between 1.11ps-9.49ps.

[0071] The above situation Figure 4 This is also reflected in the figure. The output power of the continuous laser increases linearly at the beginning, while the pulse width of the rectangular pulse output from the nonlinear fiber resonant cavity does not increase linearly, and jumps occur. Among them, the output power variation range of the continuous laser is set to 0.01W, and the output power of the continuous laser specifically jumps between 2.62W and 2.63W. In order to more clearly reflect the actual situation of the jump, the output power variation range of the continuous laser is set to 0.001W in the figure indicated by the arrow.

[0072] When the background field of the continuous laser reaches the equilibrium threshold, the generated rectangular pulse tends to be stable. Then, when the output power of the continuous laser is the second set power, the peak power of the pulsed laser is linearly adjusted from the third set power to the fourth set power, and the pulse width range of the rectangular pulse corresponds to the second set width to the third set width.

[0073] In this embodiment, the second set power range includes the third set power, the fourth set power and the power value between the two. The third set power is 1W, and the fourth set power is 17W, that is, the second set power range is 1W-17W; the third set width is 9.49ps, and the corresponding pulse width range includes the second set width, the third set width and the width value between the two, that is, the corresponding pulse width range is 6.68ps-9.49ps.

[0074] like Figure 6 As shown in the figure, as the output power of the continuous laser increases, as the power of the background field increases linearly from 0.0375W to the equilibrium threshold, the output power of the continuous laser increases to 2.63W, and the corresponding peak power of the rectangular pulse is 0.052W, that is, the equilibrium threshold of the background field is 0.052W. If the output power of the continuous laser is increased at this time, the steady state of the rectangular pulse will be destroyed. Therefore, the peak power of the pulsed laser is increased at this time, as shown in the figure. Figure 5 It can be seen that when the peak power of the pulsed laser increases, it does not cause the power of the continuous light background field to increase, that is, the pulse width of the rectangular pulse does not jump. This is because the pulsed laser is a single pulse, and the average power of a single pulse is much smaller than that of a continuous laser, which will not destroy the steady state of the rectangular pulse. Therefore, as the output power of the continuous laser increases, the pulse width of the rectangular pulse increases rapidly before and after the background field of the continuous laser reaches the equilibrium threshold. As the peak power of the pulsed laser continues to increase, the increase in the pulse width of the rectangular pulse becomes slow.

[0075] The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A rectangular pulse light generator, characterized in that: The invention comprises a first pulse generating unit (1) with a narrow line width, a second pulse generating unit (2), a first power regulating unit (3), a second power regulating unit (4), an optical path merging unit (5), an optical coupling unit (6), and a resonance unit (7), wherein the first pulse generating unit (1) is connected to the optical path merging unit (5) via the first power regulating unit (3), and the second pulse generating unit (2) is connected to the optical path merging unit (5) via the second power regulating unit (4), and the optical path merging unit (5), the optical coupling unit (6), and the resonance unit (7) are arranged in sequence; The first pulse generating unit (1) generates a first pump light, and the second pulse generating unit (2) generates a second pump light. The first pump light is adjusted in power within a first set power range by a first power adjusting unit (3), and the second pump light is adjusted in power within a second set power range by a second power adjusting unit (4). The first pump light and the second pump light are output to an optical path combining unit (5) for beam combining. The combined pump light is coupled to a resonance unit (7) via an optical coupling unit (6) to generate a rectangular pulse with a set pulse width. The first pump light is a continuous laser, and the second pump light is a pulsed laser.

2. The rectangular pulse light generator according to claim 1, characterized in that: The first power adjustment unit (3) increases the output power of the first pump light within a first set power range, and the second power adjustment unit (4) increases the output power of the second pump light within a second set power range.

3. The rectangular pulse light generator according to claim 2, characterized in that: The first set power range is 2.46W-2.63W, the second set power range is 1W-17W, and the set pulse width is 1.11ps-9.49ps.

4. The rectangular pulse light generator according to any one of claims 1 to 3, characterized in that: The first pulse generating unit (1) is one of a narrow linewidth fiber laser, a narrow linewidth semiconductor laser, and a narrow linewidth solid-state laser; The second pulse generating unit (2) is one of a fiber laser, a semiconductor laser, and a solid-state laser; The first power adjustment unit (3) is one of an optical fiber amplifier, a semiconductor optical amplifier, and a solid optical amplifier; The second power adjustment unit (4) is one of an optical fiber amplifier, a semiconductor optical amplifier, and a solid optical amplifier; The optical path merging unit (5) is one of a beam splitter, an optical fiber wavelength division multiplexer, a dichroic mirror, or any combination thereof; The optical coupling unit (6) is a fiber coupler or a beam splitter, or a combination thereof; The resonance unit (7) is a nonlinear optical fiber resonant cavity or a waveguide microcavity, or a combination thereof.

5. The rectangular pulse light generator according to claim 4, characterized in that: The first pulse generating unit (1) is a continuous fiber laser with a central wavelength of 1555 nm and an output power of 2.46 W; The second pulse generating unit (2) is a short pulse fiber laser with a central wavelength of 1550 nm, a pulse width of 1.8 ps, and a peak power of 1 W; The first power adjustment unit (3) and the second power adjustment unit (4) are both high-power erbium-doped fiber amplifiers; The optical path merging unit (5) is an optical fiber wavelength division multiplexer; The optical coupling unit (6) is a 2×2 type optical fiber coupler with a central wavelength of 1550 nm and a coupling ratio of 50:50; The resonance unit (7) is composed of a high nonlinear optical fiber with a length of 100 m and an optical fiber isolator.

6. A rectangular pulse light generating method, which is implemented by using the rectangular pulse light generator according to any one of claims 1 to 5, characterized in that: The steps include: The first pulse generating unit (1) generates a first pump light; The second pulse generating unit (2) generates a second pump light; Adjusting the power of the first pump light through a first power adjustment unit (3), and adjusting the first pump light within a first set power range; The power of the second pump light is adjusted by a second power adjustment unit (4), and the second pump light is adjusted within a second set power range; Combining the first pump light with the second pump light into a light path merging unit (5) for light path merging; The pump light combined through the optical path is coupled into the resonance unit (7) through the optical coupling unit (6); The two pump lights are coherent in the resonance unit (7) to generate rectangular pulses with different pulse widths.

7. The rectangular pulse light generating method according to claim 6, characterized in that: The first pump light is a continuous laser, and the second pump light is a pulsed laser; The power of the first pump light is adjusted by a first power adjustment unit (3), and the first pump light is adjusted within a first set power range; the power of the second pump light is adjusted by a second power adjustment unit (4), and the second pump light is adjusted within a second set power range, comprising the following steps: First, the output power of the continuous laser is adjusted from the first set power to the second set power, and the peak power of the pulsed laser is kept at the third set power. At this time, the pulse width range of the rectangular pulse corresponds to the first set width to the second set width; Then, when the output power of the continuous laser is the second set power, the peak power of the pulsed laser is adjusted from the third set power to the fourth set power. At this time, the pulse width range of the rectangular pulse corresponds to the second set width to the third set width.

8. The rectangular pulse light generating method according to claim 7, characterized in that: The first set power is 2.46 W, the second set power is 2.63 W, the third set power is 1 W, the fourth set power is 17 W, the first set width is 1.11 ps, the second set width is 6.68 ps, and the third set width is 9.49 ps.

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