A 9-shaped cavity laser with programmable start-up mode

Abstract

The application discloses a 9-shaped cavity laser with a programmable starting mode, which adopts a 9-shaped cavity mode-locked fiber laser structure. The resonant cavity contains a wave plate which can rotate an angle. In the starting process of the laser, the parameter domain of the laser can be scanned by adjusting the wave plate angle. Meanwhile, the output power of the pump diode can be adjusted according to a specific time sequence in the starting process, and the output state of the laser is monitored in real time. By adjusting the wave plate angle in the starting process and cooperating with the programmed adjustment of the output power of the pump diode, the laser is self-started, and the adjustment process is stopped when the target mode-locked state is reached. Finally, the 9-shaped cavity laser with the programmable starting mode is realized. The application can significantly improve the self-starting performance of the 9-shaped cavity laser, and enable the 9-shaped cavity laser to enter the ideal mode-locked state stably and efficiently, and has wide application prospect and great development potential.

Description

Technical Field

[0001] This invention relates to a fiber mode-locked laser, specifically a 9-cavity laser with a programmable start-up mode, belonging to the field of fiber laser technology. Background Technology

[0002] Passive mode-locking is an effective method for generating ultrashort pulses. Due to their advantages such as low cost, high stability, and small size, passively mode-locked fiber lasers have received increasing attention in the field of ultrafast lasers in recent years.

[0003] There are three main techniques commonly used to achieve passive mode-locking in fiber lasers: 1. Passive mode-locking based on a real saturable absorber; 2. Nonlinear polarization rotation technique; and 3. Nonlinear amplifying ring mirror technique. Among these, passive mode-locking based on a real saturable absorber often suffers from poor reliability and short lifespan because the performance of the saturable absorber degrades over time and may be damaged due to excessive power during use. Nonlinear polarization rotation technique relies on the evolution of the laser's polarization state within the cavity to achieve mode-locking, making it difficult to achieve a polarization-maintaining structure. Therefore, it is sensitive to external interference and prone to losing mode-locking during operation, resulting in poor stability. In contrast, nonlinear amplifying ring mirror technique can achieve a fully polarization-maintaining structure, and its performance is not easily degraded over time. Therefore, it has excellent mode-locking stability and system reliability, and its inherent low-noise characteristics give it significant advantages and potential in passive mode-locking technology for fiber lasers.

[0004] While nonlinear amplifying ring mirror technology has significant advantages, its self-starting difficulty remains a major bottleneck in its development. To overcome this problem, a novel structure based on nonlinear amplifying ring mirror technology—the figure-9 cavity laser—has been proposed. This structure introduces a phase bias within the cavity by incorporating a non-reciprocal phase-shifting device, thereby greatly optimizing its self-starting characteristics. However, the encapsulated non-reciprocal phase-shifting device has a definite phase shift, which often leads to undesirable self-starting mode-locking states in the figure-9 cavity laser due to phase shift mismatch, such as multi-pulse mode-locking and undesirable spectral morphology. Adjustable phase-shifting non-reciprocal phase-shifting devices typically contain two or even more waveplates, thus offering a vast parameter space. Conventional laser startup methods involve fixing or locking the waveplate angle and only activating the pump diode to achieve mode-locking. However, factors such as optomechanical drift of the resonant cavity itself and device aging often make it difficult to find a self-starting operating point, and subsequent optimization of undesirable mode-locking states becomes challenging. Summary of the Invention

[0005] To address the above problems, the present invention aims to provide a 9-cavity laser with a programmable start-up mode, which is easy to assemble and can be optimized through program control to find the target mode-locking state. Using the 9-cavity laser provided by this invention, excellent self-starting performance and efficient entry into the ideal mode-locking state can be achieved.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: a 9-cavity laser with a programmable start-up mode, characterized in that the laser contains a rotatable waveplate, which can scan the parameter domain of the laser within a certain range during the laser start-up process; simultaneously, the output power of its pump diode can be adjusted according to a specific timing sequence during the start-up process; furthermore, the laser has a circuit structure that can determine the laser output pulse state in real time (by coupling part of the output light into a photodetector to convert it into an electrical signal), and the laser output state is monitored in real time during the start-up process. By adjusting the waveplate angle during the start-up process, and simultaneously coordinating with the programmed adjustment of the pump diode output power, the laser can be self-started, and the adjustment process stops when the target mode-locking state is reached; ultimately, a 9-cavity laser with a programmable start-up mode is realized, the structure of which includes a 9-cavity oscillator and a circuit structure for real-time determination of the oscillator output state.

[0007] The circuit structure for real-time determination of the oscillator output state includes a photodetector and a judgment circuit, which respectively detect the output signal of the figure-9 cavity oscillator and make real-time judgments on the output state. Based on the automatic judgment results controlled by the program, the subsequent adjustment process (including adjusting the waveplate angle and / or adjusting the output power of the pump diode) is controlled to more efficiently enable the laser to reach the ideal mode-locked state.

[0008] The programmable startup mode allows for scanning the laser's parameter domain by adjusting the waveplate angle during startup, specifically including any waveplate with a rotatable angle greater than or equal to 30°. By providing the waveplate with a wide adjustable angle range, the problem of difficulty in finding and optimizing the ideal mode-locking state can be overcome when the ideal mode-locking state is scattered or scarce in the parameter domain, thus ensuring that the laser can stably enter the ideal mode-locking state.

[0009] The pump diode is a laser diode, and the pump light enters the figure-9 cavity oscillator through the pump terminal of the wavelength division multiplexer.

[0010] Specifically, the programmable startup mode involves maintaining the pump diode at an initial set power during laser startup. Then, by continuously rotating the waveplate and programmatically adjusting the pump diode output power, the laser parameter domain is scanned while the laser output state is monitored in real-time, enabling the laser to self-start. The scanning process stops once the target mode-locked state is reached. This startup mode effectively overcomes the difficulties in self-starting 9-cavity lasers and optimizing the mode-locked state, ensuring that the 9-cavity laser can stably and efficiently enter the ideal mode-locked state during startup.

[0011] The output power of the pump diode can be adjusted according to the program design. Specifically, this includes adjusting the pump power appropriately to facilitate mode-locking when the laser experiences startup difficulties; continuing to rotate the waveplate and adjusting the pump power after mode-locking to achieve the ideal mode-locking state; and restoring mode-locking by adjusting the pump power when the laser loses mode-lock during optimization. This allows for various scenarios requiring pump power adjustment, such as programmably adjusting the pump diode output power. By programmatically adjusting the pump diode output power, the programmable startup mode can optimize the mode-locking state of the 9-cavity laser in more dimensions, significantly improving the speed and effectiveness of searching for the ideal mode-locking state.

[0012] The waveplates, which can be rotated during startup, include quarter-wave plates, first half-wave plates, and / or second half-wave plates. The waveplate angle control device includes electric and / or mechanical control, as well as various other control methods capable of rotating the waveplate angle. The type, quantity, and relative order of the waveplates used during startup can be adjusted according to actual needs, taking into account their arrangement with other spatial optical elements. The waveplates include all arrangements and combinations that can mode-lock the figure-9 cavity oscillator.

[0013] The figure-9 cavity oscillator includes a reflector, a polarizing beam splitter, a quarter-wave plate, a first half-wave plate, a first Faraday rotator, a polarizing beam combiner collimator, a gain fiber, a wavelength division multiplexer (WDM), and a laser diode. The common end of the WDM is connected to one end of the gain fiber, the other end of the gain fiber is connected to one end of the polarizing beam combiner collimator, the signal end of the WDM is connected to the other end of the polarizing beam combiner collimator, and the pump end of the WDM is connected to the laser diode. After the polarizing beam combiner converts the fiber light into spatial light, it passes sequentially through the first Faraday rotator, the first half-wave plate, the quarter-wave plate, the polarizing beam splitter, and the reflector. The reflecting surface of the polarizing beam splitter outputs the laser signal.

[0014] The position of the waveplate can be adjusted according to the needs of the figure-9 cavity laser structure. The structure includes cases where the waveplate is located on the linear arm, in the fiber ring mirror, or simultaneously on the linear arm and in the fiber ring mirror.

[0015] The figure-9 cavity oscillator includes a fiber mirror, a fiber coupler, a gain fiber, a wavelength division multiplexer (WDM), a laser diode, a first collimator, a first Faraday rotator, a first half-wave plate, a quarter-wave plate, a second half-wave plate, a second Faraday rotator, and a second collimator. The common end of the WDM is connected to one end of the gain fiber, and the other end of the gain fiber is connected to the first end of the fiber coupler. The signal end of the WDM is connected to the second collimator. The pump end of the WDM is connected to the laser diode. The second end of the fiber coupler is connected to the first collimator. The third end of the fiber coupler is connected to the fiber mirror. The first Faraday rotator, the first half-wave plate, the quarter-wave plate, the second half-wave plate, and the second Faraday rotator are arranged sequentially between the first and second collimators.

[0016] The fourth end of the fiber optic coupler outputs a laser signal, which is received by a photodetector, converted into an electrical signal, and then enters the judgment circuit.

[0017] The working process is as follows: During the laser startup process, the laser diode is kept in the output state at the set power value; the angles of the first half-wave plate, quarter-wave plate, and second half-wave plate are adjusted to scan the laser parameter domain within a certain range, and the output power of the laser diode is adjusted in a programmed manner. The output state is judged in real time by the judgment circuit, so that the figure-9 cavity laser starts automatically, and the adjustment process ends after entering the ideal mode-locked state.

[0018] The figure-9 cavity oscillator includes a reflector, a polarizing beam splitter, a second half-wave plate, a third collimator, an optical fiber coupler, a gain fiber, a wavelength division multiplexer (WDM), a laser diode, a first collimator, a first Faraday rotator, a first half-wave plate, a quarter-wave plate, a second Faraday rotator, and a second collimator. The common end of the WDM is connected to one end of the gain fiber, and the other end of the gain fiber is connected to the first end of the optical fiber coupler. The signal end of the WDM is connected to the second collimator. The pump end of the WDM is connected to the laser diode. The second end of the optical fiber coupler is connected to the first collimator. The third end of the optical fiber coupler is connected to the third collimator. The first Faraday rotator, the first half-wave plate, the quarter-wave plate, and the second Faraday rotator are arranged sequentially between the first and second collimators. After the third collimator, the second half-wave plate, the polarizing beam splitter, and the reflector are arranged sequentially. The fourth end of the optical fiber coupler outputs a laser signal. The output signal is received by a photodetector, converted into an electrical signal, and then enters the judgment circuit. The working process is as follows: During the laser startup process, the laser diode is kept in the output state at the set power value; the angles of the first half-wave plate, the second half-wave plate, and the quarter-wave plate are adjusted to scan the laser parameter domain within a certain range, and the output power of the laser diode is adjusted in a programmed manner. The output state is judged in real time by the judgment circuit, so that the figure-9 cavity laser starts automatically, and the adjustment process ends after entering the ideal mode-locked state.

[0019] Beneficial Effects: This invention provides a 9-cavity laser with a programmable startup mode. Compared with existing technologies, its significant advantage lies in overcoming the potential self-starting difficulties of 9-cavity lasers through a programmable startup mode, thus improving the self-starting performance. By introducing a real-time judgment circuit and using a programmable startup mode, the laser parameter domain is scanned within a certain range by rotating the waveplate during startup, and the target mode-locked state is found in conjunction with the programmable adjustment of the pump power. Compared to the conventional startup method of fixing or locking the waveplate angle and simply turning on the pump diode to enter the mode-locked state, the programmable startup mode overcomes the technical shortcomings of potentially unsatisfactory operating states and difficulty in optimization. This significantly improves the self-starting performance of the 9-cavity laser and ensures that it can stably and efficiently enter the ideal mode-locked state. The structure is simple in design, compact in size, highly reliable, and easy to operate, greatly improving the practicality of the 9-cavity laser. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a 9-cavity laser structure with a programmable start-up mode, in Example 1, where the waveplate is located on the linear arm.

[0021] Figure 2 This is a schematic diagram of a 9-cavity laser structure with a programmable start-up mode, in Example 2, where the waveplate is located in an optical fiber ring mirror.

[0022] Figure 3 This is a schematic diagram of a figure-9 cavity laser structure with a programmable start-up mode, in Embodiment 3, where the waveplate is simultaneously located on the linear arm and in the ray ring mirror.

[0023] In the diagram: 1. Polarizing beam splitter, 2. Polarizing beam splitter, 3. Quarter-wave plate, 4. First half-wave plate, 5. First Faraday rotator, 6. Polarizing beam combiner collimator, 7. Gain fiber, 8. Wavelength division multiplexer, 9. Laser diode, 10. Photodetector, 11. Decision circuit, 12. Fiber mirror, 13. Fiber coupler, 14. Second half-wave plate, 15. Second Faraday rotator, 16. First collimator, 17. Second collimator, 18. Third collimator. Detailed Implementation

[0024] To enhance understanding of the present invention, a more detailed description is provided below with reference to the accompanying drawings.

[0025] In the preferred embodiment, the waveplates used can be adjusted in type, quantity, and relative position to other spatial optical elements according to the actual needs of the cavity shape. This includes all waveplate arrangements that can enable the figure-9 cavity laser to enter mode-locked mode. Example 1: This embodiment provides a design scheme for a figure-9 cavity laser with a programmable start-up mode, where the waveplates are located on a linear arm. Combined with... Figure 1 As shown, the specific scheme is as follows: The laser includes a reflector 1, a polarizing beam splitter 2, a quarter-wave plate 3, a first half-wave plate 4, a first Faraday rotator 5, a polarizing beam combiner collimator 6, a gain fiber 7, a wavelength division multiplexer 8, a laser diode 9, a photodetector 10, and a judgment circuit 11. Specifically: the common end of the wavelength division multiplexer 8 is connected to one end of the gain fiber 7, the other end of the gain fiber 7 is connected to one end of the polarizing beam combiner collimator 6, and the signal end of the wavelength division multiplexer 8 is connected to the other end of the polarizing beam combiner collimator 6; the pump end of the wavelength division multiplexer 8 is connected to the laser diode 9. After the polarizing beam combiner collimator 6 converts the fiber light into spatial light, it passes sequentially through the Faraday rotator 5, the first half-wave plate 4, the quarter-wave plate 3, the polarizing beam splitter 2, and the reflector 1. The reflecting surface of the polarizing beam splitter 2 outputs a laser signal. The output signal is received by the photodetector 10, converted into an electrical signal, and then enters the judgment circuit 11. The working process is as follows: During the laser startup process, the laser diode 9 is kept in the output state at the set power value; the angles of the quarter-wave plate 3 and the first half-wave plate 4 are adjusted to scan the laser parameter domain within a certain range, and the output power of the laser diode 9 is adjusted in a programmed manner. The judgment circuit 11 judges its output state in real time, so that the 9-cavity laser starts up automatically, and the adjustment process ends after entering the ideal mode-locked state.

[0026] Example 2: This example provides a design scheme for a figure-9 cavity laser with a programmable start-up mode, where the waveplate is located in a fiber optic ring mirror. Combined with... Figure 2 As shown, the specific scheme is as follows: The laser includes a fiber mirror 12, a fiber coupler 13, a gain fiber 7, a wavelength division multiplexer 8, a laser diode 9, a first collimator 16, a first Faraday rotator 5, a first half-wave plate 4, a quarter-wave plate 3, a second half-wave plate 14, a second Faraday rotator 15, a second collimator 17, a photodetector 10, and a judgment circuit 11. Specifically: the common terminal of the wavelength division multiplexer 8 is connected to one end of the gain fiber 7, the other end of the gain fiber 7 is connected to the first end of the fiber coupler 13, the signal terminal of the wavelength division multiplexer 8 is connected to the second collimator 17, and the pump terminal of the wavelength division multiplexer 8 is connected to the laser diode 9. The second terminal of the fiber coupler 13 is connected to the first collimator 16, and the third terminal of the fiber coupler 13 is connected to the fiber mirror 12. The first collimator 16 and the second collimator 17 are arranged in sequence as follows: first Faraday rotator 5, first half-wave plate 4, quarter-wave plate 3, second half-wave plate 14, and second Faraday rotator 15. A laser signal is output from the fourth end of the fiber coupler 13. The output signal is received by the photodetector 10, converted into an electrical signal, and then enters the judgment circuit 11. The working process is as follows: During laser startup, the laser diode 9 is kept in an output state at a set power value; the angles of the first half-wave plate 4, quarter-wave plate 3, and second half-wave plate 14 are adjusted to scan the laser parameter domain within a certain range, and the output power of the laser diode 9 is adjusted programmatically. The judgment circuit 11 judges its output state in real time, causing the 9-cavity laser to start automatically. After entering the ideal mode-locked state, the adjustment process ends.

[0027] Example 3: See Figure 3 This embodiment provides a design scheme for a figure-9 cavity laser with a programmable start-up mode, in which the waveplate is simultaneously located on a linear arm and in a beam ring mirror. Combined with... Figure 3As shown, the specific scheme is as follows: The laser includes a reflector 1, a polarizing beam splitter 2, a second half-wave plate 14, a third collimator 18, an optical fiber coupler 13, a gain fiber 7, a wavelength division multiplexer 8, a laser diode 9, a first collimator 16, a first Faraday rotator 5, a first half-wave plate 4, a quarter-wave plate 3, a second Faraday rotator 15, a second collimator 17, a photodetector 10, and a judgment circuit 11. Specifically: the common terminal of the wavelength division multiplexer 8 is connected to one end of the gain fiber 7, the other end of the gain fiber 7 is connected to the first end of the optical fiber coupler 13, the signal terminal of the wavelength division multiplexer 8 is connected to the second collimator 17, and the pump terminal of the wavelength division multiplexer 8 is connected to the laser diode 9. The second terminal of the optical fiber coupler 13 is connected to the first collimator 16, and the third terminal of the optical fiber coupler 13 is connected to the third collimator 19. Between the first collimator 16 and the second collimator 17, the first Faraday rotator 5, the first half-wave plate 4, the quarter-wave plate 3, and the second Faraday rotator 15 are arranged in sequence. After the third collimator 18, the second half-wave plate 14, the polarizing beam splitter 2, and the reflector 1 are arranged in sequence. The fourth end of the fiber coupler 13 outputs a laser signal. The output signal is received by the photodetector 10, converted into an electrical signal, and then enters the judgment circuit 11. The working process is as follows: During the laser startup process, the laser diode 8 is kept in the output state at the set power value; the angles of the first half-wave plate 4, the second half-wave plate 14, and the quarter-wave plate 3 are adjusted to scan the laser parameter domain within a certain range, and the output power of the laser diode 9 is adjusted programmatically. The judgment circuit 11 judges its output state in real time, so that the 9-cavity laser starts automatically, and the adjustment process ends after entering the ideal mode-locked state.

[0028] It should be noted that the above embodiments are not intended to limit the scope of protection of the present invention. Equivalent transformations or substitutions made based on the above technical solutions all fall within the scope of protection of the claims of the present invention.

Claims

1. A 9-cavity laser with a programmable start-up mode, characterized in that, The laser contains a waveplate with a rotating angle, and the laser's parameter domain is scanned by adjusting the angle of the waveplate during laser startup. Simultaneously, during startup, the output power of its pump diode is adjusted according to timing. Furthermore, the laser has a circuit structure for real-time judgment of the laser output pulse state. During startup, the laser output state is monitored in real time. By adjusting the waveplate angle during startup, and simultaneously coordinating with the programmed adjustment of the pump diode output power, the laser self-starts and stops the adjustment process when the target mode-locking state is reached. Ultimately, a 9-cavity laser with a programmable startup mode is realized, its structure including a 9-cavity oscillator and a circuit structure for real-time judgment of the oscillator output state. The circuit structure for real-time determination of the oscillator output state includes a photodetector (10) and a judgment circuit (11), which respectively detect the output signal of the 9-cavity oscillator and make real-time judgments on the output state. The programmable startup mode scans the parameter domain of the laser by adjusting the waveplate angle during startup, specifically including any waveplate with a rotatable angle greater than or equal to 30°. The pump diode is a laser diode (9), and the pump light enters the 9-cavity oscillator through the pump end of the wavelength division multiplexer (8); The programmable startup mode is specifically a laser startup method in which, during the laser startup process, the pump diode is kept in the output state at the initial set power, and then the laser parameter domain is scanned by continuously rotating the waveplate and coordinating with the programmable adjustment of the pump diode output power, while the laser output state is judged in real time to enable the laser to start automatically, and the scanning process is stopped after entering the target mode-locked state. The waveplates that rotate during startup include a quarter-wave plate (3), a first half-wave plate (4), and / or a second half-wave plate (14); the waveplate angle control device includes electric control and / or mechanical control.

2. A 9-cavity laser with a programmable start-up mode according to claim 1, characterized in that, The figure-9 cavity oscillator includes a reflector (1), a polarization beam splitter (2), a quarter-wave plate (3), a first half-wave plate (4), a first Faraday rotator (5), a polarization beam combiner (6), a gain fiber (7), a wavelength division multiplexer (8), and a laser diode (9). The common end of the wavelength division multiplexer (8) is connected to one end of the gain fiber (7), the other end of the gain fiber (7) is connected to one end of the polarization beam combiner (6), the signal end of the wavelength division multiplexer (8) is connected to the other end of the polarization beam combiner (6), and the pump end of the wavelength division multiplexer (8) is connected to the laser diode (9). After the polarization beam combiner (6) converts the fiber light into spatial light, it passes sequentially through the first Faraday rotator (5), the first half-wave plate (4), the quarter-wave plate (3), the polarization beam splitter (2), and the reflector (1).

3. A 9-cavity laser with a programmable start-up mode according to claim 1, characterized in that, The figure-9 cavity oscillator includes a fiber mirror (12), a fiber coupler (13), a gain fiber (7), a wavelength division multiplexer (8), a laser diode (9), a first collimator (16), a first Faraday rotator (5), a first half-wave plate (4), a quarter-wave plate (3), a second half-wave plate (14), a second Faraday rotator (15), and a second collimator (17). The common end of the wavelength division multiplexer (8) is connected to one end of the gain fiber (7), and the other end of the gain fiber (7) is connected to the first end of the fiber coupler (13). The signal end of the wavelength division multiplexer (8) is connected to the second collimator (17); the pump end of the wavelength division multiplexer (8) is connected to the laser diode (9); the second end of the fiber coupler (13) is connected to the first collimator (16); the third end of the fiber coupler (13) is connected to the fiber mirror (12); and the first collimator (16) and the second collimator (17) are arranged in sequence with the first Faraday rotator (5), the first half-wave plate (4), the quarter-wave plate (3), the second half-wave plate (14), and the second Faraday rotator (15).

4. A 9-cavity laser with a programmable start-up mode according to claim 1, characterized in that, The figure-9 cavity oscillator includes a reflector (1), a polarizing beam splitter (2), a second half-wave plate (14), a third collimator (18), an optical fiber coupler (13), a gain fiber (7), a wavelength division multiplexer (8), a laser diode (9), a first collimator (16), a first Faraday rotator (5), a first half-wave plate (4), a quarter-wave plate (3), a second Faraday rotator (15), and a second collimator (17). The common end of the wavelength division multiplexer (8) is connected to one end of the gain fiber (7), and the other end of the gain fiber (7) is connected to the first end of the optical fiber coupler (13). The signal end of the device (8) is connected to the second collimator (17); the pump end of the wavelength division multiplexer (8) is connected to the laser diode (9); the second end of the fiber coupler (13) is connected to the first collimator (16); the third end of the fiber coupler (13) is connected to the third collimator (18); the first collimator (16) and the second collimator (17) are arranged in sequence as the first Faraday rotator (5), the first half-wave plate (4), the quarter-wave plate (3), and the second Faraday rotator (15); the second half-wave plate (14), the polarizing beam splitter (2), and the reflector (1) are arranged in sequence after the third collimator (18).

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