A fiber-optic type pulse laser oscillator

Abstract

The application discloses a fiber type nonlinear amplification ring mirror mode-locked pulse oscillator, which forms two interference rings, namely a dissipative soliton interference ring and a dispersion management soliton interference ring, namely the oscillator comprises a dissipative soliton generating part and a dispersion management generating part; through an adjustable spatial light splitting part, the dissipative soliton interference ring is selectively enabled to output dissipative soliton pulses or the dispersion management soliton interference ring is enabled to output dispersion management pulses.

Description

Technical Field

[0001] This invention relates to an optical fiber pulsed laser oscillator. Background Technology

[0002] Fiber-based ultrafast pulsed lasers, characterized by high peak power, wide spectral range, and high temporal resolution, are widely used in cutting-edge sciences such as precision measurement, spectral imaging, and attosecond optics. The core component of an ultrafast pulsed fiber laser—the fiber-based pulse oscillator—is the seed source for pulsed laser generation, and its performance directly affects the optical path design, output parameters, and operational stability of the entire laser system. Currently, common fiber oscillators on the market include Q-switched pulse oscillators (electro-optic Q-switching, acousto-optic Q-switching, etc.) and mode-locked pulse oscillators (passive mode-locking, active mode-locking). Q-switched oscillators are limited by switching time and pulse settling time, typically resulting in pulse widths on the order of nanoseconds (ns). Mode-locked oscillators, relying on the rapid response of nonlinear devices to light intensity, have an advantage in generating ultrashort pulses on the order of ps to fs. Among the various types of mode-locked oscillators, those with nonlinear amplifying ring mirror mode-locking feature fast response speed, high stability, all-fiber operation, and narrow pulse width, making them ideal seed sources for ultrafast pulsed lasers.

[0003] Typically, we need pulse oscillators in the micrometer band, such as 1μm pulse oscillators based on mode-locking using nonlinear optical ring mirrors. In the 1μm band, some scenarios currently require the simultaneous use of two broadband short pulses: dissipative soliton pulses and dispersion-managed soliton pulses. Oscillators generate dissipative soliton pulses by introducing high positive dispersion. Since 1μm pulses propagate with positive dispersion in optical fibers, this type of cavity uses a large amount of single-mode fiber to accumulate positive dispersion. Furthermore, to achieve broadband pulsed light output, this type of cavity needs to establish mode-locking under high-power pumping. The pulse time and frequency domains are broadened under the combined effects of dispersion and nonlinearity, easily accumulating high nonlinear phase shift differences. Therefore, this type of cavity uses an "8"-shaped cavity. For 1μm dispersion-managed soliton mode-locking, a "9"-shaped cavity with dispersion compensation devices can be used. Optical devices with negative dispersion (spatial gratings, volume chirped gratings, fiber chirped gratings, etc.) are used to control the net dispersion within the cavity to near zero, resulting in short-pulse broadband seed light after mode-locking. This cavity type has lower output power and is less prone to accumulating nonlinear phase shifts, thus requiring an additional phase shifter. However, in some application scenarios, it is sometimes necessary to sequentially switch between the two types of pulsed light. For example, during the T1 time period, a dissipative soliton pulse needs to be output, while outside the T1 time period, a dispersion-managed soliton pulse is required. Therefore, it is essential to manufacture a pulse oscillator that can switch between outputting dissipative soliton pulses and dispersion-managed soliton pulses in a timely manner, while also hoping that it can be simple in structure and energy-efficient and miniaturized.

[0004] Existing technologies for outputting dispersion-managed soliton mode-locking often have complex structures, while technologies that simultaneously output multiple modes, such as CN1A17694B9A, mostly use saturable absorber mode-locking, which has low long-term stability, low output threshold, and low output pulse spectral width. In addition, they only output dissipative solitons and traditional solitons. Currently, there is no technology that can effectively switch between outputting the above two types of dissipative soliton pulses and dispersion-managed soliton pulses. Summary of the Invention

[0005] The purpose of this invention is to provide an optical fiber pulse oscillator capable of switchable output dissipative soliton and dispersion-managed soliton mode-locking.

[0006] To address the aforementioned problems, this invention provides a pulse oscillator with mode-locked fiber-optic nonlinear amplifying ring mirror.

[0007] The pulse oscillator of this invention is a fiber-optic nonlinear amplifying ring mirror mode-locked pulse oscillator. Preferably, the center wavelength range is 1000nm-1100nm; more preferably, it can generate a picosecond pulse seed source with a center wavelength of approximately 1030nm. This oscillator can form two interference rings: a dissipative soliton interference ring A and a dispersion-managed soliton interference ring B. That is, the oscillator includes a dissipative soliton generation section and a dispersion-managed generation section. Through an adjustable spatial beam splitter, the dissipative soliton interference ring A can be selectively activated to output dissipative soliton pulses, or the dispersion-managed soliton interference ring B can be activated to output dispersion-managed pulses. Preferably, by adjusting the half-wave plate angle, different types of mode-locked pulse outputs can be switched at the output coupler (i.e., the second fiber coupler).

[0008] Preferably, it includes a first fiber coupler, a second fiber coupler, a first power amplification section, an adjustable spatial light splitter section, a fiber isolator, a third fiber coupler, a fifth fiber coupler, and a fiber chirped grating.

[0009] Preferably, the dissipative soliton generation section includes: a first fiber coupler, which is a non-uniformly split optical coupler; a second fiber coupler, which is also a non-uniformly split optical coupler; a first port of the second fiber coupler is fused to the input port of the first power amplification section; the signal light generated by the first power amplification section is output to an adjustable spatial beam splitter; the adjustable spatial beam splitter is used to input the signal light generated by the first power amplification section into a fiber isolator during the dissipative soliton generation process; the fiber isolator is used to allow the signal light to flow unidirectionally into the third fiber coupler and isolate the reverse light; when the signal light emitted from the fiber isolator flows through the third fiber coupler, it is split into two beams of signal light, which enter the dissipative soliton interference loop from the two output ports of the third fiber coupler respectively, and each beam propagates in opposite directions and accumulates phase shift. Then they meet in the coupler. When the phase shift difference accumulates to a certain value, the two beams of signal light interfere in the third fiber coupler and then penetrate into the main loop, and output a dissipative soliton pulse through the pulse output port.

[0010] The dispersion-managed soliton generation section includes: a first fiber coupler, which is a non-uniformly split optical coupler; a second fiber coupler, which is also a non-uniformly split optical coupler, with its second port serving as a pulse output port; the first port of the second fiber coupler is fused to the input of the first power amplification section; the signal light generated by the first power amplification section is output to an adjustable spatial beam splitter; the adjustable spatial beam splitter, during the dispersion-managed soliton generation process, is used to input the signal light generated by the first power amplification section into a fifth fiber coupler; the signal light output from the adjustable spatial beam splitter is then fed into the fifth fiber coupler. The signal beam is losslessly coupled to a chirped fiber grating after the fiber coupler, then reflected back into the coupler and split into two beams. These beams enter the dispersion-managed soliton interference loop from the two output ports of the fifth fiber coupler, propagating in opposite directions and accumulating phase shifts. They then meet in the fifth fiber coupler. When the phase shift difference reaches a certain value, the two beams interfere within the fifth fiber coupler, forming a pulse. This pulse then enters the chirped fiber grating, where negative dispersion compensation is achieved. The pulse is compressed in the time domain, increasing its peak power and forming a dispersion-managed soliton. The soliton is reflected by the grating, passes through the fifth coupler into the interference loop, and is output by the second coupler. Preferably, the first power amplification section is used to generate the initial signal light, including a single-mode pump laser, a wavelength division multiplexer, and a single-mode polarization-maintaining gain fiber.

[0011] Preferably, it includes a second power amplification section, comprising a single-mode pump laser, a wavelength division multiplexer, and a single-mode polarization-maintaining gain fiber, for amplifying the signal light power split by the third fiber coupler, so that it rapidly accumulates phase shift difference within the interference loop.

[0012] Preferably, the fourth fiber coupler is a non-uniformly split optical coupler, and the first port of the fourth fiber coupler is a port with a large split ratio, which is used for pulse output and can output dissipative solitons.

[0013] Preferably, it includes a single-mode polarization-maintaining fiber, which serves to introduce a large amount of positive dispersion, thereby broadening the spectral width and pulse width of the signal light.

[0014] Preferably, it includes an optical fiber bandpass filter, which functions to filter noise in the signal light and modulate the spectrum of the signal light, and preferably uses a bandwidth ≤ 5nm.

[0015] Preferably, it includes an optical fiber phase shifter for introducing a -0.5π phase shift within the cavity to enhance the oscillator's self-locking capability.

[0016] Preferably, it includes an adjustable spatial light beam splitter for realizing the optical switch of the oscillator; it includes a first fiber collimator, a second fiber collimator, a third fiber collimator, a half-wave plate, and a polarizing beam splitter. By adjusting the angle of the half-wave plate, different types of mode-locked pulse outputs are switched in the second fiber coupler; adjusting the angle of the half-wave plate allows the signal light generated by the first power amplification section to be coupled to the second fiber collimator with the highest efficiency, thus activating the dissipative soliton mode-locked oscillator; adjusting the angle of the half-wave plate allows the signal light generated by the first power amplification section to be coupled to the third fiber collimator, thus activating the dispersion-managed soliton mode-locked oscillator.

[0017] Preferably, the first fiber coupler has a split ratio between 5:95 and 10:90, and more preferably, the first fiber coupler has a split ratio of 5:95; the second fiber coupler can be a split ratio coupler in the range of 1:9 to 2:8, with a 1:9 coupler being preferred; the third fiber coupler is an equal-splitting optical coupler; the fourth fiber coupler can be a split ratio fiber coupler with a split ratio of 2:8 to 4:6, with a 3:7 coupler being preferred; and the fifth fiber coupler is an equal-splitting optical coupler.

[0018] Preferably, at least some of the fiber optic devices use polarization-maintaining single-mode fiber for their pigtails.

[0019] Preferably, the pigtail of the single-mode pump laser in the first power amplification section can be made of ordinary single-mode fiber or polarization-maintaining fiber; preferably, the pigtail of the single-mode pump laser in the second power amplification section can be made of ordinary single-mode fiber or polarization-maintaining fiber.

[0020] Preferably, except for the pigtails of the single-mode pump lasers of the first and second power amplification sections, all other optical fibers and fiber optic devices of the pulsed laser oscillator use polarization-maintaining (single-mode) fiber. The various devices of the pulsed laser oscillator preferably include pigtails (though some pigtails may be omitted in some cases). Based on this, the specific optical components of the pulsed laser oscillator may include the following:

[0021] Preferably,

[0022] The beneficial effect of this invention is that it can switch between two types of soliton mode-locking, realizing a fiber pulse oscillator with switchable dissipative soliton and dispersion-managed soliton mode-locking, so as to solve the problem that existing 1-1.1μm fiber pulse oscillators are difficult to output two different types of ultrashort pulses.

[0023] The adjustable spatial beam splitter allows for switching the output pulse type by rotating the angle of the half-wave plate within this section.

[0024] Currently, other types of dual-type pulse outputs use saturable absorber mode-locking. This invention uses nonlinear amplifying ring mirror mode-locking, which prevents device performance degradation after long-term operation. Furthermore, saturable absorbers are limited by damage threshold and relaxation time, resulting in insufficient power for generating dissipative soliton pulses and insufficient spectral breadth for generating dispersion-managed soliton pulses. Using nonlinear amplifying ring mirror mode-locking can effectively improve these shortcomings.

[0025] This dual-type pulse output oscillator preferably uses a fully polarization-maintaining structure, which is not easily affected by external factors and has a high polarization extinction ratio of the output pulse light, which is beneficial for the amplification and compression of subsequent pulse light.

[0026] The preferred feature of full polarization maintenance is that all single-mode optical fibers and optical fiber devices use polarization-maintaining fibers (except for pump sources, whose polarization state does not affect the polarization of the output laser). In the spatial optical path, the polarization state of light does not easily change when it propagates in the air. When it is transmitted in a polarization beam splitter, the polarization change is negligible due to the short optical path. Therefore, the term "full polarization-maintaining structure" here refers to optical fiber devices, and the spatial optical path is assumed to be polarization-maintaining.

[0027] In particular, by using an adjustable spatial beam splitter as an optical switch, the light path is selected by adjusting the half-wave plate angle and utilizing a polarization beam splitter prism. This is a polarization-dependent optical switch, where different light polarization states correspond to dissipative soliton pulse mode-locking and dispersion-managed soliton mode-locking, respectively. It prominently achieves a fully polarization-maintaining structure for the entire pulse oscillator, significantly improving the polarization-maintaining characteristics of the entire system compared to other non-polarization-dependent optical switches. Since the optical coupling efficiency of polarization-dependent fiber-optic optical splitters is relatively low, this switch can significantly improve the beam coupling efficiency and the overall optical efficiency of the system compared to polarization-dependent fiber-optic optical switches. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of a preferred embodiment of the present invention.

[0029] Figure 2 This is a schematic diagram of the adjustable spatial light beam splitter.

[0030] Figure 3 This is a schematic diagram of Embodiment 1 of the present invention. Detailed Implementation

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

[0032] like Figure 1 As shown, the pulse oscillator of this invention is a fiber-optic nonlinear amplifying ring mirror mode-locked pulse oscillator, with a selectable center wavelength range of 1000nm-1100nm (achieved by adding a bandpass filter); in some embodiments, it can generate picosecond pulse seed sources with an approximate center wavelength of 1030nm. See also Figure 1 The oscillator can form two interference rings: a dissipative soliton interference ring A and a dispersion-managed soliton interference ring B. That is, the oscillator includes a dissipative soliton generation section and a dispersion-managed generation section. Through an adjustable spatial beam splitter, the dissipative soliton interference ring A can be selectively activated to output dissipative soliton pulses, or the dispersion-managed soliton interference ring B can be activated to output dispersion-managed pulses. Preferably, different types of mode-locked pulse outputs can be switched at the output coupler 2 (i.e., the second fiber coupler) by adjusting the half-wave plate angle.

[0033] The mode-locked pulse oscillator of the fiber-optic nonlinear amplifying ring mirror includes a first fiber coupler 1, a second fiber coupler 2 (as an output coupler), a first power amplification section 3, an adjustable spatial light beam splitter section 4, a fiber isolator 5, a third fiber coupler 6, a second power amplification section 7, a fourth fiber coupler 8, a fiber-optic bandpass filter 9, a single-mode polarization-maintaining fiber 10, a fifth fiber coupler 11, a fiber chirped grating 12, and a fiber phase shifter 13.

[0034] The components constituting the dissipative soliton generation section include: a first fiber coupler 1, preferably an unequal-ratio / non-uniform splitting fiber coupler; serving as the connection between the dissipative soliton ring and the main ring, and the dissipative soliton does not interfere in the main ring, but only transmits unidirectionally in the coupler, and can have a splitting ratio of 5:95 to 1:9. Since a smaller value can reduce the loss of dispersion management mode locking, it is preferably 5:95 (the selection of this splitting ratio is explained in the dispersion management soliton generation section below), and preferably has three ports, for example, a 1X2 coupler, namely the first port 1A of the first fiber coupler, the second port 1B of the first fiber coupler, and the third port 1C of the first fiber coupler, wherein the first port 1A of the first fiber coupler is a branch port with a larger splitting ratio, the second port 1B of the first fiber coupler is a branch port with a smaller splitting ratio, the first port 1A and the second port 1B of the first fiber coupler are on the first side of the first fiber coupler, and the third port 1C of the first fiber coupler is a combined port on the second side of the first fiber coupler corresponding to the above two branch ports 1A and 1B.

[0035] Preferably, since the second fiber coupler is capable of outputting two types of soliton pulses, it is essential to obtain the mode-locking state in the pulse oscillator in a timely manner. Preferably, an output port can be added to the first fiber coupler for monitoring mode-locking (since the first fiber coupler is located at the front end of the second fiber coupler). Preferably, the first fiber coupler can be a 2x2 fiber splitter, that is, it also includes the fourth port 1D of the first fiber coupler. The first port 1A and the second port 1B of the first fiber coupler are on the first side of the first fiber coupler, and the third port 1C and the fourth port 1D of the first fiber coupler are on the second side of the first fiber coupler. The fourth port 1D of the first fiber coupler can be used as an output port for monitoring mode-locking.

[0036] The second fiber coupler 2 is preferably an unequal split ratio / non-uniform splitting optical coupler. Since this coupler serves as the output port for both dissipative solitons and dispersion-managed soliton pulses, and the loss inside the dispersion-managed cavity is relatively high, it is not advisable to select a coupler with an excessively high splitting ratio to ensure output power. A splitting ratio coupler in the range of 1:9 to 2:8 can be selected, with a 1:9 coupler preferred. Preferably, it has three ports, such as a 1X2 coupler, namely the first port 2A, the second port 2B, and the third port 2C of the second fiber coupler. The first port 2A of the second fiber coupler is a branch port with a larger splitting ratio, and the second port 2B of the second fiber coupler is a branch port with a smaller splitting ratio, used as a pulse output port. Preferably, it can output dissipative solitons. The first port 2A and the second port 2B of the second fiber coupler are on the first side of the second fiber coupler, and the third port 2C of the second fiber coupler is a combined port on the second side of the second fiber coupler, corresponding to the above two branch ports 2A and 2B.

[0037] The third port 1C of the first fiber coupler is fused to the third port 2C of the second fiber coupler; the first port 2A of the second fiber coupler is fused to the input end of the first power amplification section 3. The function of the first power amplification section 3 is to generate the initial signal light. Preferably, the composition includes a single-mode pump laser, a wavelength division multiplexer, and a single-mode polarization-maintaining (ytterbium-doped) gain fiber. Preferably, the output center wavelength of the single-mode pump laser is approximately 976nm, and the output power is 600-900mW. Preferably, it has built-in fiber grating frequency stabilization and temperature monitoring. Preferably, the pump light output fiber is of type Hi1060 and is fused to the wavelength division multiplexer. A section of single-mode polarization-maintaining gain fiber is fused to the output end of the wavelength division multiplexer. Preferably, the single-mode polarization-maintaining gain fiber is a single-mode polarization-maintaining ytterbium-doped gain fiber. Preferably, the length of the gain fiber is 0.5-5m. Preferably, the length of the gain fiber is 2m, and the structural parameters are 5 / 125μm (core / cladding diameter).

[0038] Preferably, the first fiber coupler and the second fiber coupler can be two independent fiber couplers connected together by a pigtail, or they can be a 2x2 fiber coupler manufactured as a whole, having a 2x1 first fiber coupler functional part on the front side and a 1x2 second fiber coupler functional part on the rear side.

[0039] Adjustable spatial beam splitter 4 (see Figure 2The optical switch 6 acts as the optical switch for the oscillator. It includes a first fiber collimator 3.1, a second fiber collimator 3.4, a third fiber collimator 3.5, a half-wave plate 3.2, and a polarizing beam splitter (PBS) 3.3. Adjusting the angle of the half-wave plate 3.2 allows the signal light generated by the first power amplification section 3 to be coupled to the second collimator 3.4 with maximum efficiency, thus activating the dissipative soliton mode-locked oscillator. The fiber isolator 5 is used to allow the signal light to flow unidirectionally into the third fiber coupler 6 and to isolate the reverse light. The third fiber coupler 6 preferably adopts a fiber coupler with a basic 50:50 split ratio, and is preferably an equal-ratio / equal-splitting fiber coupler (the third fiber coupler preferably has four ports, for example, a 2X2 coupler, namely the first port 6A, the second port 6B, the third port 6C, and the fourth port 6D of the third fiber coupler; wherein, the first port 6A and the second port 6B of the third fiber coupler are two branch ports on the first side of the third fiber coupler; the third port 6C and the fourth port 6D of the third fiber coupler are two branch ports on the second side of the third fiber coupler). Thus, when the signal light emitted from the isolator flows through the third fiber coupler, it is split into two signal beams according to the power ratio. These beams enter the dissipative soliton interference loop from the two output ports of the coupler, propagating in opposite directions and accumulating phase shift. They are then combined in the coupler. When the phase shift difference accumulates to a certain value, the two signal beams interfere within the coupler to form a pulse, which is then transmitted into the main loop with low loss. Since dissipative solitons typically have high power, they can support simultaneous output from both ports (the fourth fiber coupler 8 and the second fiber coupler 2). Preferably, the fourth fiber coupler 8 can be a fiber coupler with a split ratio of 2:8 to 4:6, and more preferably a 3:7 coupler. The output power of this coupler will be higher than that of the second fiber coupler 2. This can significantly improve the output power of the dissipative soliton pulse. Compared to a single output channel where the dissipative soliton can only be output through the second fiber coupler 2, this can greatly improve the output capability of the dissipative soliton.

[0040] The second power amplification section 7 is used to amplify the signal light power split by the third fiber coupler, so that it can quickly accumulate phase shift difference in the interference loop. The basic structure of the second power amplification section 7 is similar to that of the first power amplification section. Preferably, it also includes a single-mode pump laser, a wavelength division multiplexer, and a single-mode polarization-maintaining (ytterbium-doped) gain fiber. The specific parameters can also be selected with similar values. The length of the gain fiber of the second power amplification section can be selected to be shorter, preferably 0.2-0.9m, and preferably 0.5m.

[0041] The fourth fiber coupler 8 is preferably a non-uniform splitting / non-uniform splitting optical coupler (the fourth fiber coupler 8 can be a fiber coupler with a splitting ratio of 2:8 to 4:6, preferably a 3:7 coupler), preferably having a splitting ratio of 30:70, and having a first port 8A, a second port 8B, and a third port 8C of the fourth fiber coupler. The first port 8A is a branch port with a larger splitting ratio, and the second port 8B is a branch port with a smaller splitting ratio. The first port 8A and the second port 8B are both located on the first side of the fourth fiber coupler. The third port 8C is a combined port on the second side of the fourth fiber coupler, corresponding to the two branch ports 8A and 8B. The first port 8A of the fourth fiber coupler serves as a pulse output port, preferably capable of outputting dissipative solitons; that is, preferably, the output port with a larger splitting ratio is the pulse output port, for example, the 70% port is the pulse output port. The second port 8B of the fourth fiber coupler couples the signal light into the main loop for cyclic amplification. The output power 101 of the first port of the fourth fiber coupler is higher than the output power 201 of the second port of the second fiber coupler. The fiber-type bandpass filter 9 filters noise from the signal light and modulates its spectrum; preferably, a bandwidth ≤ 5nm is used. The single-mode polarization-maintaining fiber 10 introduces a large amount of positive dispersion, broadening the spectral and pulse width of the signal light. The pulse light first enters the bandpass filter for filtering and noise reduction, limiting the spectrum within its bandwidth. Then, it passes through the single-mode polarization-maintaining fiber. Under the combined effects of dispersion and nonlinearity, the spectrum is broadened from a relatively narrow band due to nonlinear effects (mainly self-phase modulation). This process involves deep spectral modulation, while the pulse is broadened by positive dispersion. A certain amount of linear chirp is introduced during this process, making the seed source easier to amplify and withstand higher energy, resulting in a pulse light with higher peak power after compression. The output end connects to the branch port 1B of the first fiber coupler, which has a smaller splitting ratio. The broadened signal light then enters the main loop for cyclic amplification.

[0042] The components of dispersion-managed soliton generation include:

[0043] The first fiber coupler 1, preferably, can be a coupler with a beam ratio of 5:95 to 1:9, preferably a 5:95 coupler. This is because the first fiber coupler will act as a device in the dispersion-managed soliton interference loop, and the interference light that generates the dispersion-managed soliton will be transmitted bidirectionally in the coupler. To reduce the loss of optical power within the loop, a coupler with an extremely low beam ratio is preferred, preferably an unequal ratio / non-uniform beam splitting optical coupler, preferably having three ports, for example, a 1X2 coupler, namely the first port 1A, the second port 1B, and the third port 1C of the first fiber coupler. The first port 1A of the first fiber coupler is a branch port with a larger beam splitting ratio, and the second port 1B of the first fiber coupler is a branch port with a smaller beam splitting ratio. The first port 1A and the second port 1B of the first fiber coupler are on the first side of the first fiber coupler; the third port 1C of the first fiber coupler is a combined port on the second side of the first fiber coupler corresponding to the above two branch ports 1A and 1B. The first port 1A of the first fiber coupler is fused to the phase shifter 1C. The second fiber coupler, which can serve as the final output port for pulsed light, is used to ultimately output pulsed light; preferably, it can ultimately output dispersion-managed soliton pulses. Preferably, it has a 10:90 beam splitting ratio, is preferably an unequal ratio / non-uniform beam splitting coupler, and preferably has three ports, for example, a 1x2 coupler: the first port 2A, the second port 2B, and the third port 2C of the second fiber coupler. The first port 2A is a branch port with a larger beam splitting ratio, and the second port 2B is a branch port with a smaller beam splitting ratio. The second port 2B, as the branch port with the smaller beam splitting ratio, is used as the pulse output port, preferably outputting dispersion-managed soliton pulses; the third port 2C is the combined port corresponding to the two branch ports 2A and 2B. The first port 1A of the second fiber coupler is fused to the input terminal of the first power amplification section 3. The first power amplification section 3: its function is to generate the initial signal light and amplify the power. Adjustable spatial beam splitter 4 (participating) Figure 2 The optical switch (PSS) of the oscillator is composed of a first fiber collimator (3.1), a second fiber collimator (3.4), a third fiber collimator (3.5), a half-wave plate (3.2), and a polarizing beam splitter (PBS) (3.3).

[0044] Adjusting the half-wave plate angle, the signal light generated by the first power amplification section 3 is coupled to the third fiber collimator 3.5, activating the dispersion-managed soliton mode-locked oscillator. The fifth fiber coupler 11, preferably, is a fiber coupler with a basic 50:50 beam splitting ratio, preferably an equal-ratio / equal-ratio fiber coupler (the fifth fiber coupler preferably has three ports, for example, a 1x2 coupler, namely the first port 11A, the second port 11B, and the third port 11C of the fifth fiber coupler, wherein the first port 11A and the fifth fiber coupler 11B are branch ports, the first port 11A and the second port 11B are both on the first side of the fifth fiber coupler; the third port 11C is the branch port of the fifth fiber coupler). The signal light output from the adjustable spatial beam splitter is losslessly coupled to the fiber chirped grating 12 after passing through the fifth fiber coupler 11 (which can reflect laser light within the bandwidth, while laser light outside the bandwidth will be transmitted). Then, it is reflected back to the coupler by the grating and split into two signal beams according to the power ratio. These beams enter the dispersion-managed soliton interference loop from the two output ports of the fifth fiber coupler, and each beam propagates in opposite directions and accumulates phase shift. They then meet in the coupler. When the phase shift difference accumulates to a certain value, the two signal beams interfere in the coupler and are reflected into the fiber chirped grating 12 with low loss. Fiber chirped grating 12: Its function is to reflect the signal light in the cavity and introduce a certain amount of negative dispersion, so that the net dispersion in the cavity is close to zero; Fiber phase shifter 13: Due to the high loss in the interference loop, the nonlinear ring mirror mode-locking property makes it difficult to establish a mode-locked pulse under low pump conditions. By actively introducing a -0.5π phase shift in the cavity using a fiber phase shifter, it can obtain a linearly increasing light reflectivity under low pump conditions, improve the self-locking capability of the oscillator, and facilitate the mode-locking of the dispersion management loop.

[0045] The mode-locked pulse oscillator of the fiber optic nonlinear amplifying ring mirror can be implemented using Example 1 (refer to Example 1). Figure 3 The system includes: a first fiber optic coupler 1, a second fiber optic coupler 2 (as an output coupler), a first power amplification section 3, an adjustable spatial light beam splitter section 4, a fiber optic isolator 5, a third fiber optic coupler 6, a second power amplification section 7, a fifth fiber optic coupler 11, a fiber optic chirped grating 12, and a fiber optic phase shifter 13.

[0046] The second port 1B of the branch with a smaller splitting ratio of the first fiber coupler 1 is connected to the first port 6A of the branch of the third fiber coupler; the first port 1A of the branch with a larger splitting ratio of the first fiber coupler 1 is connected to the fiber phase shifter 13; the signal input terminal 2C of the second fiber coupler is connected to the third port 1C of the first fiber coupler 1; the second port 2B of the branch with a smaller splitting ratio of the second fiber coupler 2 serves as the pulse output port; the first port 2A of the branch with a larger splitting ratio of the second fiber coupler 2 is connected to the first power amplification section 3; the output section of the first power amplification section 3 is connected to the first collimator of the adjustable spatial beam splitter section 4. 3.1; The second fiber collimator 3.4 of the adjustable spatial light beam splitter 4 is connected to the fiber isolator 5; the fiber isolator 5 is connected to the second branch port 6B of the third fiber coupler; the first branch port 6A of the third fiber coupler is connected to the second branch port 1B of the first fiber coupler 1; the fourth branch port 6D of the third fiber coupler is connected to the second power amplification section 7, and the output of the second power amplification section 7 is connected to the third branch port 6C of the third fiber coupler; that is, the ring structure including the second power amplification section between the third branch port and the fourth branch port of the third fiber coupler serves as a dissipative soliton interference ring.

[0047] The third fiber collimator 3.5 of the adjustable spatial beam splitter 4 is connected to the first port 11A of one branch of the fifth fiber coupler 11. The second port 11B of the other branch of the fifth fiber coupler is connected to one end of the fiber phase shifter 13, and the other end of the fiber phase shifter is connected to the first port 1A of the first fiber coupler. The third port 11C of the fifth fiber coupler is connected to the fiber chirped grating 12. The fiber chirped grating 12 serves to reflect the signal light inside the cavity and simultaneously introduce a certain amount of negative dispersion, making the net dispersion inside the cavity close to zero.

[0048] Preferably, the adjustable spatial beam splitter allows for switching the output pulse type by rotating the angle of the half-wave plate in this section.

[0049] Alternatively, when dispersion management soliton pulses are not required, fiber chirped gratings can be replaced by spatial grating pairs. By controlling the spacing of the spatial grating pairs, the amount of negative dispersion introduced can be freely controlled.

[0050] For the pulse oscillator mode-locked by the entire fiber-optic nonlinear amplifying ring mirror, a preferred embodiment can also be implemented that includes at least one of the following three components: a fourth fiber coupler 8, a fiber-optic bandpass filter 9, and a single-mode polarization-maintaining fiber 10. For ease of explanation of the preferred embodiment, the following is a second preferred embodiment (refer to) including all three components (fourth fiber coupler 8, fiber-optic bandpass filter 9, and single-mode polarization-maintaining fiber 10). Figure 1The system includes: a first fiber coupler 1, a second fiber coupler 2 (as an output coupler), a first power amplification section 3, an adjustable spatial beam splitter section 4, a fiber isolator 5, a third fiber coupler 6, a second power amplification section 7, a fourth fiber coupler 8, a fiber bandpass filter 9, a single-mode polarization-maintaining fiber 10, a fifth fiber coupler 11, a fiber chirped grating 12, and a fiber phase shifter 13.

[0051] The second port 1B of the branch with a smaller splitting ratio of the first fiber coupler 1 is connected to the single-mode polarization-maintaining fiber 10; the first port 1A of the branch with a larger splitting ratio of the first fiber coupler 1 is connected to the fiber phase shifter 13; the signal input terminal 2C of the second fiber coupler is connected to the third port 1C of the first fiber coupler 1; the second port 2B of the branch with a smaller splitting ratio of the second fiber coupler 2 serves as the pulse output port; the first port 2A of the branch with a larger splitting ratio of the second fiber coupler 2 is connected to the first power amplification section 3; the output section of the first power amplification section 3 is connected to the first fiber collimator 3.1 of the adjustable spatial light beam splitter section 4; the second fiber collimator 3.4 of the adjustable spatial light beam splitter section 4 is connected to the fiber isolator 5; the fiber isolator 5 is connected to the third... The second branch port 6B of the fiber coupler; the first end of the single-mode polarization-maintaining fiber 10 is connected to the second branch port 1B of the first fiber coupler 1, and the second end of the single-mode polarization-maintaining fiber 10 is connected to the first end of the fiber-type bandpass filter 9; the second end of the fiber-type bandpass filter 9 is connected to the second branch port 8B of the fourth fiber coupler 8; the third port 8C of the fourth fiber coupler is connected to the first branch port 6A of the third fiber coupler; the fourth branch port 6D of the third fiber coupler is connected to the second power amplification section 7, and the output end of the second power amplification section 7 is connected to the third branch port 6C of the third fiber coupler; that is, the ring structure including the second power amplification section between the third branch port and the fourth branch port of the third fiber coupler serves as a dissipative soliton interference ring.

[0052] The third fiber collimator 3.5 of the adjustable spatial beam splitter 4 is connected to the first port 11A of one branch of the fifth fiber coupler 11. The second port 11B of the other branch of the fifth fiber coupler is connected to one end of the fiber phase shifter 13, and the other end of the fiber phase shifter is connected to the first port 1A of the first fiber coupler. The third port 11C of the fifth fiber coupler is connected to the fiber chirped grating 12. The fiber chirped grating 12 serves to reflect the signal light inside the cavity and simultaneously introduce a certain amount of negative dispersion, making the net dispersion inside the cavity close to zero.

[0053] Preferably, the adjustable spatial beam splitter allows for switching the output pulse type by rotating the angle of the half-wave plate in this section.

[0054] Alternatively, when dispersion management soliton pulses are not required, fiber chirped gratings can be replaced by spatial grating pairs. By controlling the spacing of the spatial grating pairs, the amount of negative dispersion introduced can be freely controlled.

[0055] Unless otherwise specified, the pigtails of optical fiber devices are preferably made of polarization-maintaining single-mode fiber, and preferably PM 980 single-mode fiber.

[0056] Preferably, the first fiber collimator of the adjustable spatial light beam splitter 4 is a polarization-maintaining fiber collimator, the second fiber collimator of the adjustable spatial light beam splitter 4 is a polarization-maintaining fiber collimator, and the third fiber collimator of the adjustable spatial light beam splitter 4 is a polarization-maintaining fiber collimator. In a spatial optical path, the polarization state of light does not easily change when it propagates in the air under normal circumstances.

[0057] Preferably, at least some of the fiber optic devices use polarization-maintaining single-mode fiber for their pigtails.

[0058] Preferably, the pigtail of the single-mode pump laser in the first power amplification section can be made of ordinary single-mode fiber or polarization-maintaining fiber; preferably, the pigtail of the single-mode pump laser in the second power amplification section can be made of ordinary single-mode fiber or polarization-maintaining fiber.

[0059] Except for the pigtails of the single-mode pump lasers in the first and second power amplification sections, all other optical fibers and fiber optic devices of the pulsed laser oscillator use polarization-maintaining (single-mode) fiber. Preferably, each component of the pulsed laser oscillator may include a pigtail (although in some cases, some pigtails may be omitted). Based on this, the specific optical components of the pulsed laser oscillator may include the following:

[0060] Preferably, the pigtail of the first fiber coupler 1 is made of polarization-maintaining single-mode fiber.

[0061] Preferably, the pigtail of the second fiber coupler 2 is made of polarization-maintaining single-mode fiber.

[0062] Preferably, the pigtail of the wavelength division multiplexer in the first power amplification section 3 can be a polarization-maintaining single-mode fiber.

[0063] Preferably, the pigtail of the first fiber collimator of the adjustable spatial light beam splitter 4 is made of polarization-maintaining single-mode fiber; preferably, the pigtail of the second fiber collimator of the adjustable spatial light beam splitter 4 is made of polarization-maintaining single-mode fiber; preferably, the pigtail of the third fiber collimator of the adjustable spatial light beam splitter 4 is made of polarization-maintaining single-mode fiber.

[0064] Preferably, the pigtail of the fiber optic isolator 5 is made of polarization-maintaining single-mode fiber.

[0065] Preferably, the pigtail of the third fiber coupler 6 is made of polarization-maintaining single-mode fiber.

[0066] Preferably, the pigtail of the wavelength division multiplexer in the second power amplification section 7 can be a polarization-maintaining single-mode fiber.

[0067] Preferably, the pigtail of the fourth fiber coupler 8 can be a polarization-maintaining single-mode fiber.

[0068] Preferably, the pigtail of the fiber-optic bandpass filter 9 can be made of polarization-maintaining single-mode fiber.

[0069] Preferably, the pigtail of the fifth fiber coupler 11 can be a polarization-maintaining single-mode fiber.

[0070] Preferably, the pigtail of the fiber chirped grating 12 can be made of polarization-maintaining single-mode fiber.

[0071] Preferably, the pigtail of the fiber phase shifter 13 can be made of polarization-maintaining single-mode fiber.

[0072] The pigtails of the various optical devices mentioned above, in addition to the pigtails that come with the devices themselves at the factory, can also be understood as transitional and connecting optical fibers used to connect (in some cases, fusion splicing) to the corresponding optical devices.

[0073] The technical principles of the present invention have been described above with reference to specific embodiments. These descriptions are merely for explaining the principles of the invention and should not be construed as limiting the scope of protection of the invention in any way. Based on this explanation, those skilled in the art can readily conceive of other specific embodiments of the invention without inventive effort, and these embodiments will all fall within the scope of protection of the present invention.

Claims

1. A fiber-optic pulsed laser oscillator, comprising two interference rings, namely a dissipative soliton interference ring and a dispersion-managed soliton interference ring, and an adjustable spatial beam splitter; the adjustable spatial beam splitter allows selective activation of either the dissipative soliton interference ring to output a dissipative soliton pulse or the dispersion-managed soliton interference ring to output a dispersion-managed pulse; the adjustable spatial beam splitter includes a first fiber collimator, a second fiber collimator, a third fiber collimator, a half-wave plate, and a polarizing beam splitter prism; by adjusting the angle of the half-wave plate, different types of mode-locked pulse outputs are switched at a second fiber coupler; adjusting the angle of the half-wave plate allows the signal light generated by the first power amplification section to be coupled to the second fiber collimator with maximum efficiency, activating the dissipative soliton mode-locked oscillator; adjusting the angle of the half-wave plate allows the signal light generated by the first power amplification section to be coupled to the third fiber collimator, activating the dispersion-managed soliton mode-locked oscillator.

2. The fiber-optic pulsed laser oscillator according to claim 1, comprising a first fiber coupler, a second fiber coupler, a first power amplification section, an adjustable spatial beam splitter section, a fiber isolator, a third fiber coupler, a fifth fiber coupler, and a fiber chirped grating. in, The dissipative soliton generation section includes: a first fiber coupler, which is a non-uniformly split optical coupler; a second fiber coupler, which is also a non-uniformly split optical coupler; the first port of the second fiber coupler is fused to the input port of the first power amplification section; the signal light generated by the first power amplification section is output to an adjustable spatial beam splitter; the adjustable spatial beam splitter is used to input the signal light generated by the first power amplification section into a fiber isolator during the dissipative soliton generation process; the fiber isolator is used to allow the signal light to flow unidirectionally into the third fiber coupler and isolate the reverse light; when the signal light emitted from the fiber isolator flows through the third fiber coupler, it is split into two beams of signal light, which enter the dissipative soliton interference loop from the two output ports of the third fiber coupler respectively, and each propagates in opposite directions and accumulates phase shift, and then meets in the coupler. When the phase shift difference accumulates to a certain value, the two beams of signal light interfere in the third fiber coupler, and then are transmitted into the main loop, and the dissipative soliton pulse is output through the pulse output port; The dispersion-managed soliton generation section includes: a first fiber coupler, which is a non-uniformly split optical coupler; a second fiber coupler, which is also a non-uniformly split optical coupler, with its second port serving as a pulse output port; the first port of the second fiber coupler is fused to the input of the first power amplification section; the signal light generated by the first power amplification section is output to an adjustable spatial beam splitter; the adjustable spatial beam splitter, during the dispersion-managed soliton generation process, is used to input the signal light generated by the first power amplification section into a fifth fiber coupler; the signal light output from the adjustable spatial beam splitter is then coupled to the fifth fiber coupler. After lossless coupling, the signal beams are fed into a chirped fiber grating and then reflected back into the coupler. They are then split into two beams and enter the dispersion-managed soliton interference loop from the two output ports of the fifth fiber coupler. They propagate in opposite directions and accumulate phase shifts, then are combined in the fifth fiber coupler. When the phase shift difference accumulates to a certain value, the two beams interfere within the fifth fiber coupler, forming a pulse. This pulse then enters the chirped fiber grating and receives negative dispersion compensation. The pulse is compressed in the time domain, increasing the peak power and forming a dispersion-managed soliton. The soliton is reflected by the grating, passes through the fifth fiber coupler into the interference loop, and is output from the second fiber coupler.

3. The fiber-optic pulsed laser oscillator according to claim 2, wherein the first power amplification section comprises a single-mode pump laser, a wavelength division multiplexer, and a single-mode polarization-maintaining gain fiber for generating initial signal light.

4. The fiber-optic pulsed laser oscillator according to claim 2 further includes a second power amplification section, which includes a single-mode pump laser, a wavelength division multiplexer, and a single-mode polarization-maintaining gain fiber, for amplifying the power of the signal light beam split by the third fiber coupler, so that it rapidly accumulates phase shift difference within the interference loop.

5. The fiber-optic pulsed laser oscillator according to claim 2, comprising a fiber-optic phase shifter for introducing a -0.5π phase shift within the cavity to enhance the oscillator's self-locking capability.

6. The fiber-optic pulsed laser oscillator according to claim 2, comprising: Single-mode polarization-maintaining fiber is used to introduce a large amount of positive dispersion, thereby broadening the spectral width and pulse width of the signal light.

7. The fiber-optic pulsed laser oscillator according to claim 2, comprising: Fiber optic bandpass filters are used to filter noise from signal light and modulate the spectrum of signal light, with a bandwidth of ≤5nm.

8. The fiber-optic pulsed laser oscillator according to claim 2, comprising: a fourth fiber-optic coupler, which is a non-uniformly splitting optical coupler, wherein the first port of the fourth fiber-optic coupler is a port with a large splitting ratio for pulse output, which can output dissipative solitons.

9. The fiber-optic pulsed laser oscillator according to claim 2, wherein the adjustable spatial beam splitter is used to realize the optical switch of the oscillator.

10. The fiber-optic pulsed laser oscillator according to claim 2, wherein the first fiber coupler has a beam splitting ratio between 5:95 and 10:90; the second fiber coupler has a beam splitting ratio between 1:9 and 2:8; the third fiber coupler is an equal-splitting optical coupler; the fourth fiber coupler has a beam splitting ratio between 2:8 and 4:6; the fifth fiber coupler is an equal-splitting optical coupler; and at least a portion of the fiber optic devices use polarization-maintaining single-mode fiber for their pigtails.

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