Nonlinear phase shift adjustable optical fiber picosecond seed source and use method thereof

Abstract

The invention relates to the technical field of lasers, and discloses a nonlinear phase shift adjustable optical fiber picosecond seed source and a use method thereof.The nonlinear phase shift adjustable optical fiber picosecond seed source comprises an upper semi-annular cavity and a lower semi-annular cavity, the upper semi-annular cavity comprises a first semiconductor butterfly pump, and the first semiconductor butterfly pump is used for providing energy for the upper semi-annular cavity; the lower semi-annular cavity comprises a second semiconductor butterfly-shaped pump, the second semiconductor butterfly-shaped pump is used for providing energy for the lower semi-annular cavity, and the change of power distribution of the annular cavity is compensated by adjusting the pumping power ratio of the first semiconductor butterfly-shaped pump to the second semiconductor butterfly-shaped pump. When the device tolerance is large and the consistency is poor, the loss difference of the device causes the change of the power distribution of the annular cavity, and the change of the power distribution of the annular cavity is compensated by adjusting the pumping power of the first semiconductor butterfly pump and the second semiconductor butterfly pump, so that the production of a picosecond seed source is simplified, the optical fiber length of each part of the annular cavity does not need to be finely adjusted, and the production cost is reduced. And the consistency of the device is strictly controlled without spending a lot of energy.

Description

Technical Field

[0001] The invention relates to the technical field of lasers, in particular to an optical fiber picosecond seed source with adjustable nonlinear phase shift and a use method thereof. Background Art

[0002] In the field of ultrafast lasers, the picosecond seed source for mode locking is usually made based on the principle of nonlinear ring mirrors. However, this solution has high requirements on the consistency of devices. Device differences will affect the accumulation of nonlinear phase shift, thereby affecting mode locking. In order to maintain the yield of the picosecond seed source based on the principle of nonlinear ring mirrors, strict quality control and inspection of the device is required. When customizing the device, the specification tolerance needs to be reduced to ensure consistency, which undoubtedly increases the difficulty of production, the cost of the device and the labor cost of debugging and testing. Therefore, it is necessary to design a fiber picosecond seed source that can achieve adjustable nonlinear phase shift in the cavity, and change the gain distribution to affect the accumulation of nonlinear phase shift, so as to control the nonlinear phase shift in the cavity.

[0003] However, in current technology, the nonlinear phase shift of conventional nonlinear ring mirror mode-locking schemes cannot be adjusted. To adjust it, it is necessary to change the length distribution of the optical fiber in the cavity, which in turn requires a lot of effort to strictly control the consistency of the device. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides an optical fiber picosecond seed source with adjustable nonlinear phase shift, which solves the problem of the need to fine-tune the optical fiber length of each part of the ring cavity and the high time cost.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solutions: a nonlinear phase-shift adjustable optical fiber picosecond seed source, comprising an upper semi-annular cavity and a lower semi-annular cavity, wherein the upper semi-annular cavity comprises a first semiconductor butterfly pump, and the first semiconductor butterfly pump is used to provide energy to the upper semi-annular cavity, and the lower semi-annular cavity comprises a second semiconductor butterfly pump, and the second semiconductor butterfly pump is used to provide energy to the lower semi-annular cavity, and the change of the power distribution of the annular cavity is compensated by adjusting the pump power ratio of the first semiconductor butterfly pump to the second semiconductor butterfly pump.

[0006] Preferably, the first semiconductor butterfly pump is connected to a 980nm filter isolator via an optical fiber, and the 980nm filter isolator is used to protect the first semiconductor butterfly pump.

[0007] Preferably, the 980nm filter isolator optical fiber is connected to a wavelength division multiplexer to transmit the filtered and protected optical signal to the wavelength division multiplexer.

[0008] Preferably, the wavelength division multiplexer is connected to the single-mode ytterbium-doped optical fiber via an optical fiber. After the wavelength division multiplexer couples the 980nm pump light into the loop, it is connected to the single-mode ytterbium-doped optical fiber via the optical fiber, so that the pump light can be absorbed by the single-mode ytterbium-doped optical fiber and excited to generate 1064nm signal light.

[0009] Preferably, the single-mode ytterbium-doped optical fiber is connected to a 30:70 splitter, and the signal light generated by the single-mode ytterbium-doped optical fiber is transmitted to the 30:70 splitter, which plays a role of coherent mode locking in the ring cavity. The 30:70 splitter is connected to a chirped fiber grating through an optical fiber, and a portion of the light separated by the 30:70 splitter enters the chirped fiber grating. The chirped fiber grating limits the spectral range of the oscillator by reflecting light in a specific band, and the chirped fiber grating is on a branch path after the 30:70 splitter.

[0010] Preferably, the chirped fiber grating transmits the processed optical signal to a phase shifter, and the phase shifter is used to provide a phase shift difference for the optical signal to promote mode locking.

[0011] Preferably, the phase shifter is connected to a 10:90 optical splitter via an optical fiber, and the optical signal processed by the phase shifter is transmitted to the 10:90 optical splitter, and the 10:90 optical splitter is used to extract the ring cavity laser output.

[0012] Preferably, the 10:90 splitter is connected to the 1064nm filter isolator by optical fiber on one hand, and the 10:90 splitter is connected to the photoelectric probe at the same time, and on the other hand, a part of the optical signal is separated to continue to circulate in the annular cavity, and the optical signal for output separated by the 10:90 splitter is isolated and outputted through the 1064nm filter isolator to prevent the return light from interfering with the locking mode.

[0013] Preferably, the optical signal separated by the 10:90 optical splitter and continuing to circulate in the annular cavity is connected to a second semiconductor butterfly pump via an optical fiber, and the second semiconductor butterfly pump is used to receive the circulating light from the 10:90 optical splitter and provide energy for it.

[0014] A method for using an optical fiber picosecond seed source with adjustable nonlinear phase shift comprises the following steps:

[0015] S1. Optical fiber connection between optical fibers and devices: connecting various devices in sequence through optical fibers, and building a ring cavity based on optical fibers;

[0016] S2. Preliminary debugging: Turn on the first semiconductor butterfly pump and the second semiconductor butterfly pump, gradually increase the pump power, observe the response of the system, use the photoelectric probe to monitor the mode-locking state in the annular cavity, observe the electrical signal output by the photoelectric probe, and determine whether the system starts to generate light pulses. If the mode is not locked, appropriately adjust the pump power or other parameters to promote the start of mode locking;

[0017] S3: nonlinear phase shift adjustment: adjust the pump power of the first semiconductor butterfly pump and the second semiconductor butterfly pump with a small power step. According to the rule of change, the higher the power, the longer the optical fiber passes through, and the power distribution of the upper and lower half rings in the annular cavity is changed to adjust the nonlinear phase shift accumulation;

[0018] S4: Performance optimization: Based on the adjusted results, further optimize other device parameters in the fiber picosecond seed source to stabilize the mode locking.

[0019] The present invention provides an optical fiber picosecond seed source with adjustable nonlinear phase shift, which has the following beneficial effects:

[0020] 1. When the device tolerance is large and the consistency is poor, the device loss difference leads to a change in the power distribution of the annular cavity. The pump power of the first semiconductor butterfly pump and the second semiconductor butterfly pump are adjusted to compensate for the change in the power distribution of the annular cavity, thereby simplifying the production of picosecond seed sources, eliminating the need to fine-tune the optical fiber length of each part of the annular cavity and expending a lot of effort to strictly control the consistency of the device.

[0021] 2. When the phase shift of the phase shifter differs, causing the phase shift of the annular cavity to change and making it impossible to stabilize the mode locking, the present invention compensates for the difference caused by the phase shifter by adjusting the power ratio of the first semiconductor butterfly pump and the second semiconductor butterfly pump, thereby stabilizing the mode locking.

[0022] 3. The present invention optimizes each device to ensure that the light can achieve the best performance during the propagation and amplification process in the annular cavity without excessive loss or instability due to unreasonable distribution of optical fiber length, thereby achieving the effect of no need to adjust the optical fiber length distribution and quality control devices, facilitating production and reducing production time costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the optical path diagram of the optical fiber device of the optical fiber picosecond seed source with adjustable nonlinear phase shift of the present invention.

[0024] Among them, 1. the first semiconductor butterfly pump; 2. 980nm filter isolator; 3. wavelength division multiplexer; 4. single-mode ytterbium-doped optical fiber; 5. 30:70 splitter; 6. chirped fiber grating; 7. phase shifter; 8. 10:90 splitter; 9. 1064nm filter isolator; 10. photoelectric probe; 11. the second semiconductor butterfly pump. DETAILED DESCRIPTION

[0025] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] Please see attached Figure 1 An embodiment of the present invention provides a nonlinear phase-shift adjustable optical fiber picosecond seed source, comprising an upper semi-annular cavity and a lower semi-annular cavity, wherein the upper semi-annular cavity comprises a first semiconductor butterfly pump 1, and the first semiconductor butterfly pump 1 is used to provide energy to the upper semi-annular cavity, and the lower semi-annular cavity comprises a second semiconductor butterfly pump 11, and the second semiconductor butterfly pump 11 is used to provide energy to the lower semi-annular cavity, and the change of the power distribution of the annular cavity is compensated by adjusting the pump power ratio of the first semiconductor butterfly pump 1 to the second semiconductor butterfly pump 11.

[0027] Specifically, the first semiconductor butterfly pump 1 serves as the energy source for the upper semi-ring cavity, injects pump light into the optical path system of the upper semi-ring cavity, provides power for the optical process of the entire upper semi-ring cavity, ensures that the optical signal can effectively propagate and perform various optical conversions in this area, and ensures stable optical pulse output. The second semiconductor butterfly pump 11 provides energy for the lower semi-ring cavity, and maintains the optical power balance of the entire ring cavity together with the first semiconductor butterfly pump 1. In the process of the optical signal circulating in the ring cavity, the second semiconductor butterfly pump 11 ensures that the lower semi-ring cavity has enough energy to maintain optical processes such as light amplification and mode locking.

[0028] The first semiconductor butterfly pump 1 is connected to the 980nm filter isolator 2 via an optical fiber, and the 980nm filter isolator 2 is used to protect the first semiconductor butterfly pump 1 .

[0029] Specifically, the first semiconductor butterfly pump 1 can effectively inject pump light into the subsequent optical system by connecting to the optical fiber, start the optical process of the entire ring cavity, and is located at the starting end of the ring cavity, ensuring the first input of energy and providing a power source for the operation of subsequent devices.

[0030] The 980nm filter isolator 2 is connected to the wavelength division multiplexer 3 via an optical fiber, and transmits the filtered and protected optical signal to the wavelength division multiplexer 3 .

[0031] Specifically, the 980nm filter isolator 2 filters the optical signal from the first semiconductor butterfly pump 1, removes unnecessary wavelength components and stray light, ensures that only the pump light of the specific wavelength of 980nm can pass through and be transmitted to the wavelength division multiplexer 3, and at the same time protects the first semiconductor butterfly pump 1 to prevent possible reverse light from interfering with the pump source, and transmits the filtered and protected pure optical signal to the next device wavelength division multiplexer 3, which outputs an optical signal of a specific wavelength, so that the wavelength division multiplexer 3 can accurately identify and process the signal. The wavelength division multiplexer 3 requires light of different wavelengths for multiplexing operations, and the 980nm filter isolator 2 provides a specific wavelength light that meets its working requirements, thereby optimizing the wavelength division multiplexing effect.

[0032] The wavelength division multiplexer 3 is connected to the single-mode ytterbium-doped fiber 4 through an optical fiber. After the wavelength division multiplexer 3 couples the 980nm pump light into the loop, it is connected to the single-mode ytterbium-doped fiber 4 through an optical fiber, so that the pump light can be absorbed by the single-mode ytterbium-doped fiber 4 and excited to generate 1064nm signal light.

[0033] Specifically, the wavelength division multiplexer 3 couples the 980nm pump light into the loop, so that the pump light can enter the subsequent optical system, and is connected to the single-mode ytterbium-doped optical fiber 4 through the optical fiber, ensuring that the pump light is accurately transmitted to the single-mode ytterbium-doped optical fiber 4. After the single-mode ytterbium-doped optical fiber 4 receives the 980nm pump light from the wavelength division multiplexer 3, the ytterbium ions therein absorb the energy of the pump light. This absorption process excites the single-mode ytterbium-doped optical fiber 4 to generate 1064nm signal light. The single-mode ytterbium-doped optical fiber 4 is located in the middle part of the ring cavity, and plays a core optical conversion role, converting the pump light into the required signal light, providing a specific wavelength of light output for the entire optical fiber picosecond seed source, and achieving the effect of stable signal light generation.

[0034] The single-mode ytterbium-doped optical fiber 4 is connected to the 30:70 splitter 5. The signal light generated by the single-mode ytterbium-doped optical fiber 4 is transmitted to the 30:70 splitter 5. The 30:70 splitter 5 plays a role of coherent mode locking in the ring cavity. The 30:70 splitter 5 is connected to the chirped fiber grating 6 through the optical fiber. A part of the light separated by the 30:70 splitter 5 enters the chirped fiber grating 6. The chirped fiber grating 6 limits the spectral range of the oscillator by reflecting light in a specific band. The chirped fiber grating 6 is on a branch path after the 30:70 splitter 5.

[0035] Specifically, the signal light generated by the single-mode ytterbium-doped optical fiber 4 is transmitted to the 30:70 splitter 5, which distributes the optical signal according to a certain ratio. 30% of the light continues to be transmitted on the main path, and 70% of the light is used for coherent mode locking. The two-coherent mode locking function enables the system to generate a stable sequence of picosecond optical pulses, so that the splitting ratio can be adjusted according to system requirements to achieve flexible control of optical power on different paths. At the same time, a part of the light split by the 30:70 splitter 5 enters the chirped fiber grating 6. The chirped fiber grating 6 limits the spectral range of the oscillator by reflecting light in a specific band, thereby effectively controlling the spectral characteristics of the optical signal.

[0036] The chirped fiber grating 6 transmits the processed optical signal to the phase shifter 7, and the phase shifter 7 is used to provide a phase shift difference for the optical signal to promote mode locking.

[0037] Specifically, the optical signal processed by the chirped fiber grating 6 enters the phase shifter 7 to ensure the continuous transmission and further processing of the optical signal in the system. The phase shifter 7 is in the ring cavity and can promote the occurrence of the mode locking process by introducing a specific phase shift difference. The phase shifter 7 adjusts the phase relationship of the optical signal so that different modes of light can interfere with each other in the ring cavity and form a stable mode locking state.

[0038] The phase shifter 7 is connected to the 10:90 optical splitter 8 through an optical fiber, and the optical signal processed by the phase shifter 7 is transmitted to the 10:90 optical splitter 8, and the 10:90 optical splitter 8 is used to extract the ring cavity laser output.

[0039] Specifically, the optical signal processed by the phase shifter 7 is transmitted to the 10:90 splitter 8, which ensures the continuous transmission of the optical signal in the system, plays the role of optical signal distribution and control, and determines the laser output ratio extracted from the ring cavity. At the same time, the splitting ratio can be adjusted according to actual needs to achieve flexible control of the ring cavity laser output.

[0040] On the one hand, the 10:90 optical splitter 8 is connected to the 1064nm filter isolator 9 by optical fiber, and is also connected to the photoelectric probe 10. On the other hand, a part of the optical signal is separated to continue to circulate in the annular cavity. The optical signal for output separated by the 10:90 optical splitter 8 is isolated and outputted through the 1064nm filter isolator 9 to prevent the return light from interfering with the locking mode.

[0041] Specifically, by adjusting the splitting ratio, the output optical power and the optical power distribution in the ring cavity can be controlled to achieve flexible adjustment of the system output. At the same time, the 1064nm filter isolator 9 is the last device located at the output end of the ring cavity to isolate the optical signal separated for output. It can prevent reverse light from entering the ring cavity, prevent the return light from interfering with the locking process, and ensure that the output optical signal is pure and is not affected by the reverse light or stray light that may exist in the ring cavity. It improves the quality and stability of the output light and ensures that the system can continuously generate high-quality picosecond optical pulses. The photoelectric probe 10 can be used to detect the locking state of the ring cavity.

[0042] The optical signal separated by the 10:90 optical splitter 8 and continuing to circulate in the annular cavity is connected to the second semiconductor butterfly pump 11 through an optical fiber. The second semiconductor butterfly pump 11 is used to receive the circulating light from the 10:90 optical splitter 8 and provide energy for it.

[0043] Specifically, the second semiconductor butterfly pump 11 receives the optical signal that continues to circulate in the annular cavity from the 10:90 splitter 8, and plays a key role in the second half of the annular cavity, ensuring that the optical signal can continue to circulate in the annular cavity, realizing multiple utilization and enhancement of light. At the same time, by receiving the circulating light, the second semiconductor butterfly pump 11 provides a basis for the re-propagation and further processing of the optical signal, and the second semiconductor butterfly pump 11 provides energy for the circulating light to maintain the intensity and stability of the optical signal in the annular cavity. It works together with the first semiconductor butterfly pump 1 to provide energy support for the entire optical fiber picosecond seed source, ensuring that the system can operate normally and generate high-quality optical pulses. According to the needs of the system, the first semiconductor butterfly pump 1 and the second semiconductor butterfly pump 11 can adjust the power distribution to change the nonlinear accumulation, so as to make the phase relationship of the light in the annular cavity more stable and meet the phase requirements of the locking mode.

[0044] A method for using an optical fiber picosecond seed source with adjustable nonlinear phase shift, the method comprising the following steps:

[0045] S1. Optical fiber connection between optical fibers and devices: connecting various devices in sequence through optical fibers, and building a ring cavity based on optical fibers;

[0046] S2, preliminary debugging: turn on the first semiconductor butterfly pump 1 and the second semiconductor butterfly pump 11, gradually increase the pump power, observe the response of the system, use the photoelectric probe 10 to monitor the mode-locking state in the annular cavity, observe the electrical signal output by the photoelectric probe 10, and determine whether the system starts to generate light pulses. If the mode is not locked, appropriately adjust the pump power or other parameters to promote the start of mode locking;

[0047] S3: nonlinear phase shift adjustment: adjust the pump power of the first semiconductor butterfly pump 1 and the second semiconductor butterfly pump 11 with a small power step. According to the rule of change, the higher the power, the longer the optical fiber passes through, and the power distribution of the upper and lower half rings in the annular cavity is changed to adjust the nonlinear phase shift accumulation;

[0048] S4: Performance optimization: Based on the adjusted results, further optimize other device parameters in the fiber picosecond seed source to stabilize the mode locking.

[0049] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. Fiber picosecond seed source with adjustable nonlinear phase shift, characterized in that: The invention comprises an upper semi-annular cavity and a lower semi-annular cavity, wherein the upper semi-annular cavity comprises a first semiconductor butterfly pump (1), and the first semiconductor butterfly pump (1) is used to provide energy to the upper semi-annular cavity, and the lower semi-annular cavity comprises a second semiconductor butterfly pump (11), and the second semiconductor butterfly pump (11) is used to provide energy to the lower semi-annular cavity, and the change of the power distribution of the annular cavity is compensated by adjusting the pump power ratio of the first semiconductor butterfly pump (1) to the second semiconductor butterfly pump (11).

2. The optical fiber picosecond seed source with adjustable nonlinear phase shift according to claim 1, characterized in that: The first semiconductor butterfly pump (1) is connected to a 980nm filter isolator (2) via an optical fiber, and the 980nm filter isolator (2) is used to protect the first semiconductor butterfly pump (1).

3. The optical fiber picosecond seed source with adjustable nonlinear phase shift according to claim 2, characterized in that: The 980nm filter isolator (2) is connected to the wavelength division multiplexer (3) via an optical fiber, and transmits the filtered and protected optical signal to the wavelength division multiplexer (3).

4. The optical fiber picosecond seed source with adjustable nonlinear phase shift according to claim 3, characterized in that: The wavelength division multiplexer (3) is connected to the single-mode ytterbium-doped optical fiber (4) via an optical fiber. After the wavelength division multiplexer (3) couples 980nm pump light into a loop, it is connected to the single-mode ytterbium-doped optical fiber (4) via an optical fiber, so that the pump light can be absorbed by the single-mode ytterbium-doped optical fiber (4) and excited to generate 1064nm signal light.

5. The optical fiber picosecond seed source with adjustable nonlinear phase shift according to claim 4, characterized in that: The single-mode ytterbium-doped optical fiber (4) is connected to a 30:70 optical splitter (5); the signal light generated by the single-mode ytterbium-doped optical fiber (4) is transmitted to the 30:70 optical splitter (5); the 30:70 optical splitter (5) plays a role of coherent mode locking in the ring cavity; the 30:70 optical splitter (5) is connected to a chirped fiber grating (6) through an optical fiber; a portion of the light split by the 30:70 optical splitter (5) enters the chirped fiber grating (6); the chirped fiber grating (6) limits the spectral range of the oscillator by reflecting light in a specific wavelength band; the chirped fiber grating (6) is on a branch path after the 30:70 optical splitter (5).

6. The optical fiber picosecond seed source with adjustable nonlinear phase shift according to claim 5, characterized in that: The chirped fiber grating (6) transmits the processed optical signal to the phase shifter (7), and the phase shifter (7) is used to provide a phase shift difference for the optical signal to promote mode locking.

7. The optical fiber picosecond seed source with adjustable nonlinear phase shift according to claim 6, characterized in that: The phase shifter (7) is connected to a 10:90 optical splitter (8) via an optical fiber, and the optical signal processed by the phase shifter (7) is transmitted to the 10:90 optical splitter (8), and the 10:90 optical splitter (8) is used to extract the ring cavity laser output.

8. The optical fiber picosecond seed source with adjustable nonlinear phase shift according to claim 7, characterized in that: The 10:90 optical splitter (8) is connected to the 1064nm filter isolator (9) via an optical fiber. The 10:90 optical splitter (8) is also connected to the photoelectric probe (10). On the other hand, a portion of the optical signal is split to continue to circulate in the annular cavity. The optical signal for output split by the 10:90 optical splitter (8) is isolated and output through the 1064nm filter isolator (9) to prevent the return light from interfering with the locking mode.

9. The optical fiber picosecond seed source with adjustable nonlinear phase shift according to claim 8, characterized in that: The optical signal separated by the 10:90 optical splitter (8) and continuing to circulate in the annular cavity is connected to a second semiconductor butterfly pump (11) via an optical fiber. The second semiconductor butterfly pump (11) is used to receive the circulating light from the 10:90 optical splitter (8) and provide energy for it.

10. A method for using an optical fiber picosecond seed source with adjustable nonlinear phase shift, characterized in that: For the optical fiber picosecond seed source with adjustable nonlinear phase shift according to any one of claims 1 to 9, the method comprises the following steps: S1. Optical fiber connection between optical fibers and devices: connecting various devices in sequence through optical fibers, and building a ring cavity based on optical fibers; S2, preliminary debugging: start the first semiconductor butterfly pump (1) and the second semiconductor butterfly pump (11), gradually increase the pump power, observe the response of the system, use the photoelectric probe (10) to monitor the mode-locking state in the annular cavity, observe the electrical signal output by the photoelectric probe (10), and determine whether the system starts to generate optical pulses. If the mode is not locked, appropriately adjust the pump power or other parameters to promote the start of mode locking; S3: nonlinear phase shift adjustment: adjusting the pump power of the first semiconductor butterfly pump (1) and the second semiconductor butterfly pump (11) with a small power step, according to the rule that the higher the power, the longer the optical fiber, the power distribution of the upper half ring and the lower half ring in the annular cavity is changed, and the nonlinear phase shift accumulation is adjusted; S4: Performance optimization: Based on the adjusted results, further optimize other device parameters in the fiber picosecond seed source to stabilize the mode locking.

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