Dual-wavelength mode-locked fiber laser capable of being switched and tuned and debugging method

Abstract

The invention discloses a dual-wavelength mode-locked fiber laser capable of being switched and tuned and a corresponding debugging method, and relates to the technical field of lasers. According to the dual-wavelength mode-locked fiber laser capable of being switched and tuned, two SESAMs and two output light paths are combined with the pump light gain medium, and proper dual-wavelength parameters and corresponding optical devices are selected, so that dual-wavelength ultra-short pulse mode-locked laser can be generated, and meanwhile, the dual-wavelength mode-locked fiber laser capable of being switched and tuned can be used as a dual-wavelength ultra-short pulse mode-locked laser. The dual-wavelength ultra-short pulse mode-locked laser is output in an adjustable manner by controlling the polarization controllers in the two output light paths, switching or simultaneous output of the dual-wavelength ultra-short pulse mode-locked laser is achieved, and the dual-wavelength ultra-short pulse mode-locked laser has the advantages of being simple in structure, convenient to operate and stable in output.

Description

Technical Field

[0001] The invention relates to the technical field of lasers, in particular to a switchable and tunable dual-wavelength mode-locked optical fiber laser and a corresponding debugging method. Background Art

[0002] Fiber lasers have rapidly emerged in the development of lasers due to their high efficiency, easy integration, and excellent beam quality, and have become a hot research topic in academia and industry. Among them, switchable and tunable mode-locked fiber lasers have been widely used in many fields, such as spectroscopy, photochemistry, medicine, biology, integrated optics, pollution monitoring, semiconductor material processing, information processing, and communications.

[0003] In order to obtain a switchable and tunable mode-locked fiber laser, there are mainly the following implementation methods in the existing technology. One is to use the tapered fiber solution, which uses the difference between the refractive indices of the media to cause phase difference, achieve mode interference, and generate filtering to achieve dual-wavelength mode-locked output effect; another is to use the eccentric insertion method of optical fiber jumpers to achieve adjustable loss in the resonant cavity and achieve the purpose of dual wavelength adjustment; another is to use ordinary optical fiber and special optical fiber to fuse, achieve mode interference to achieve wavelength adjustment, etc. However, the existing implementation schemes have the defects of difficult preparation and operation, poor stability, complex corresponding structure, and high preparation cost. Summary of the invention

[0004] The purpose of the present invention is to propose a switchable and tunable dual-wavelength mode-locked fiber laser, improve the mode-locking mechanism and switching mechanism of the dual-wavelength ultrashort pulse laser, so as to solve the problems mentioned in the background technology.

[0005] On the one hand, the present invention provides a switchable and tunable dual-wavelength mode-locked fiber laser, including a mode-locked oscillation subsystem and a mode-locked output subsystem, wherein the mode-locked oscillation subsystem includes a first SESAM1, a second SESAM2, a polarization-maintaining beam splitter 3, a pump source 4, a wavelength division multiplexer 5, and a gain medium 6, and is used to generate a dual-wavelength ultrashort pulse mode-locked laser; the mode-locked output subsystem includes two output optical paths for adjustable output of the dual-wavelength ultrashort pulse mode-locked laser, including a non-polarization-maintaining beam splitter 7, a first wavelength output optical path, and a second wavelength output optical path, and the switchable tuning of the dual-wavelength short pulse mode-locked laser is achieved by selecting appropriate dual-wavelength parameters and corresponding optical devices.

[0006] Furthermore, the first SESAM1 and the second SESAM2 are connected to the first port of the wavelength division multiplexer 5 through the polarization-maintaining beam splitter 3; the second port of the wavelength division multiplexer 5 is connected to the pump source 4, and the third port of the wavelength division multiplexer 5 is connected to the gain medium 6, which is used to introduce the pump light emitted by the pump source 4 into the gain medium 6, excite the gain medium 6 to achieve particle number inversion, and generate ultrashort laser pulses.

[0007] Furthermore, the first wavelength output optical path is formed by connecting the first polarization controller 8, the first analyzer 9, the first polarization-maintaining fiber grating 10 and the first polarization-maintaining isolator 11 in sequence in the optical path direction; the second wavelength output optical path is formed by connecting the second polarization controller 12, the second analyzer 13, the second polarization-maintaining fiber grating 14 and the second polarization-maintaining isolator 15 in sequence in the optical path direction; the first wavelength output optical path and the second wavelength output optical path are connected to the gain medium 6 through the non-polarization-maintaining beam splitter 7.

[0008] Furthermore, the wavelength parameters of the first SESAM1 and the first wavelength output optical path are both the first wavelength; the wavelength parameters of the second SESAM2 and the second wavelength output optical path are both the second wavelength; and the first wavelength and the second wavelength match the emission wavelength of the gain medium 6.

[0009] Furthermore, the present invention provides a dual-wavelength mode-locked fiber laser of 920nm and 1064nm, wherein the first wavelength and the second wavelength are selected as 920nm and 1064nm respectively, and Nd-doped gain fiber is used as the gain medium, so that mode-locked operation can be achieved simultaneously in the 920nm and 1064nm bands.

[0010] On the other hand, the present invention also provides a switchable tunable debugging method for a dual-wavelength mode-locked fiber laser, which controls the first polarization controller 8 and / or the second polarization controller 12 in the two output optical paths, thereby controlling the size of the laser transmission loss in the two laser resonant cavities, and obtaining controllable control of the two-way laser mode locking, and outputting the dual-wavelength ultrashort pulse mode-locked laser in an adjustable manner, thereby realizing switchable tunable separate mode-locked output or simultaneous mode-locked output, and completing dual-wavelength switching or simultaneous output.

[0011] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: The present invention provides an improved switchable and tunable dual-wavelength mode-locked fiber laser. By improving the mode-locking mechanism of ultrashort laser pulses, the dual-wavelength ultrashort pulse mode-locked laser can be generated and adjustable output can be performed on the dual-wavelength ultrashort pulse mode-locked laser at the same time, thereby realizing dual-wavelength switch switching or simultaneous output. The laser has the advantages of simple structure, convenient operation and stable output. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative work, among which: Figure 1 is a schematic diagram of the structure of a fiber laser provided by an embodiment of the present invention; Figure 2 This is a diagram of an output pulse sequence of a 920nm laser provided in an embodiment of the present invention; Figure 3 This is a graph showing the pulse width measurement results of a 920nm laser provided in an embodiment of the present invention; Figure 4 is a spectrum measurement result diagram of a 920nm laser provided by an embodiment of the present invention; Figure 5 is an output pulse sequence diagram of a 1060nm laser provided in an embodiment of the present invention; Figure 6 is a graph showing the pulse width measurement results of a 1060nm laser provided in an embodiment of the present invention; Figure 7 is a spectrum measurement result diagram of a 1060nm laser provided by an embodiment of the present invention; The descriptions of the numbers in the figure are as follows: 1. First SESAM; 2. Second SESAM; 3. Polarization-maintaining beam splitter; 4. Pump source; 5. Wavelength division multiplexer; 6. Gain medium; 7. Non-polarization-maintaining beam splitter; 8. First polarization controller; 9. First analyzer; 10. First polarization-maintaining fiber grating; 11. First polarization-maintaining isolator; 12. Second polarization controller; 13. Second analyzer; 14. Second polarization-maintaining fiber grating; 15. Second polarization-maintaining isolator. DETAILED DESCRIPTION

[0013] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, that is, the embodiments described are only part of the embodiments of the present invention, rather than all of the embodiments. The components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0014] It should be noted that relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprises" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "includes one / two ways..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0015] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0016] like Figure 1 The figure shows a switchable and tunable dual-wavelength mode-locked fiber laser, including a mode-locked oscillation subsystem and a mode-locked output subsystem.

[0017] Specifically, the mode-locked oscillation subsystem is used to generate dual-wavelength ultrashort pulse mode-locked laser, including a first SESAM1, a second SESAM2, a polarization-maintaining beam splitter 3, a pump source 4, a wavelength division multiplexer 5, and a gain medium 6. The first SESAM1 and the second SESAM2 are connected to the first port of the wavelength division multiplexer 5 through the polarization-maintaining beam splitter 3, and are used to achieve ultrashort pulse laser mode locking of the first wavelength and the second wavelength, respectively.

[0018] The second port of the wavelength division multiplexer 5 is connected to the pump source 4, and the third port of the wavelength division multiplexer 5 is connected to the gain medium 6, which is used to introduce the pump light emitted by the pump source 4 into the gain medium 6, excite the gain medium 6 to achieve particle number inversion, and generate ultrashort laser pulses.

[0019] The mode-locked output subsystem is used for adjustable output of dual-wavelength ultrashort pulse mode-locked laser, and comprises a non-polarization-maintaining beam splitter 7, a first wavelength output optical path and a second wavelength output optical path; wherein the first wavelength output optical path is formed by sequentially connecting a first polarization controller 8, a first polarization analyzer 9, a first polarization-maintaining fiber grating 10 and a first polarization-maintaining isolator 11 in the direction of the optical path; and the second wavelength output optical path is formed by sequentially connecting a second polarization controller 12, a second polarization analyzer 13, a second polarization-maintaining fiber grating 14 and a second polarization-maintaining isolator 15 in the direction of the optical path.

[0020] The first wavelength output optical path and the second wavelength output optical path are connected to the gain medium 6 via a non-polarization maintaining beam splitter 7. The non-polarization maintaining beam splitter 7 is used to realize parallel splitting of laser beams of different wavelengths and combine laser beams of different wavelengths into one beam.

[0021] It can be seen that the two SESAMs (the first SESAM1 / the second SESAM2) are connected in parallel to the wavelength division multiplexer 5 through the polarization-maintaining beam splitter 3, and the pump laser and the signal laser are merged into the gain medium 6 through the wavelength division multiplexer 5 to provide sufficient laser gain for the generation of ultrashort pulse lasers; and then connected to the non-polarization-maintaining beam splitter 7, and the other end of the non-polarization-maintaining beam splitter 7 is connected in parallel with two output optical paths (the first wavelength output optical path / the second wavelength output optical path).

[0022] In order to ensure the compatibility of the two SESAMs and the two output optical paths, it is necessary to make the wavelength parameters of the first SESAM1 and the first wavelength output optical path both the first wavelength and form a first laser resonant cavity; and the wavelength parameters of the second SESAM2 and the second wavelength output optical path both the second wavelength and form a second laser resonant cavity. At the same time, in order to ensure the normal light emission of the laser, it is necessary to make the first wavelength and the second wavelength match the emission wavelength of the gain medium 6.

[0023] This embodiment is a further explanation of the present invention.

[0024] This embodiment will take the first wavelength and the second wavelength of 920nm and 1064nm respectively as an example to explain in detail the aforementioned switchable and tunable dual-wavelength mode-locked fiber laser.

[0025] Accordingly, the specific selection of each optical element in the dual-wavelength mode-locked fiber laser in this embodiment is as follows: In the mode-locked oscillation subsystem, the first SESAM1 is a SESAM for 920nm band laser mode-locking, the second SESAM2 is a second SESAM2 for 1064nm band laser mode-locking, and the gain medium 6 is an Nd-doped gain fiber; In the first wavelength output optical path, the first polarization-maintaining fiber grating 10 is a 920nm polarization-maintaining fiber grating, the first polarization-maintaining isolator 11 is a 920nm polarization-maintaining isolator, and the first polarization controller 8 and the first analyzer 9 are optical devices required for the first wavelength; In the second wavelength output optical path, the second polarization-maintaining fiber grating 14 is a 1064nm polarization-maintaining fiber grating, the second polarization-maintaining isolator 15 is a 1064nm polarization-maintaining isolator, and the second polarization controller 12 and the second analyzer 13 are optical devices required for the first wavelength.

[0026] From the perspective of functional realization, it can be considered that the above dual-wavelength mode-locked fiber laser includes two lasers: a 920nm ultrashort pulse mode-locked laser and a 1064nm ultrashort pulse mode-locked laser. The 920nm ultrashort pulse mode-locked laser is composed of a 920nm first SESAM1, a polarization-maintaining beam splitter 3, a pump source 4, a wavelength division multiplexer 5, an Nd-doped gain fiber, a non-polarization-maintaining beam splitter 7, a first polarization controller 8, a first analyzer 9, a 920nm first polarization-maintaining fiber grating 10 and a 920nm first polarization-maintaining isolator 11, which are sequentially connected to form a linear first laser resonant cavity; the 1064nm ultrashort pulse mode-locked laser is composed of a 1064nm second SESAM2, a polarization-maintaining beam splitter 3, a pump source 4, a wavelength division multiplexer 5, an Nd-doped gain fiber, a non-polarization-maintaining beam splitter 7, a second polarization controller 12, a second analyzer 13, a 1064nm second polarization-maintaining fiber grating 14 and a 1064nm second polarization-maintaining isolator 15, which are sequentially connected to form a linear second laser resonant cavity.

[0027] On the other hand, Nd-doped gain fiber has a wide radiation characteristic of 800-1100 nm, and it has two typical emission peaks in the emission spectrum range of 800-1100 nm, corresponding to central wavelengths of ~920 nm and ~1064 nm, respectively. At present, Nd-doped gain fiber is an ideal medium for generating lasers in the 920 nm and 1064 nm bands. In laser operation, the 920 nm emission wavelength corresponds to the three-level radiation characteristics of Nd ions (4F3 / 2-4F9 / 2), while 1060 nm corresponds to the four-level radiation characteristics of Nd ions (4F3 / 2-4F11 / 2). The low threshold radiation characteristics of the four-level 4F3 / 2-4F11 / 2 at 1064 nm are very easy to produce laser oscillation. Therefore, it is inevitable that 1060 nm laser oscillation will be generated in the 920 nm band mode-locked laser and amplifier. Therefore, the present invention uses Nd-doped gain fiber to achieve mode-locked operation in both the 920 nm and 1064 nm bands.

[0028] As a preferred embodiment, the transmittance of the first polarization-maintaining fiber grating 10 at 920 nm is less than 80%, and the reflectivity is greater than 20%; the transmittance of the second polarization-maintaining fiber grating 14 at 1064 nm is less than 80%, and the reflectivity is greater than 20%.

[0029] When debugging the optical path of the switchable and tunable dual-wavelength mode-locked fiber laser in any of the aforementioned embodiments, the polarization controllers (first polarization controller 8 / second polarization controller 12) in the two output optical paths are adjusted respectively, and the birefringence of the optical fiber is changed by squeezing and deforming the optical fiber, thereby changing the birefringence effect of the optical fiber, so that the light passes through the optical fiber and generates an additional phase change. The polarization mode of the laser in the resonant cavity is subsequently analyzed by the analyzer (first polarization analyzer 9 / second polarization analyzer 13). If the polarization directions are consistent, the laser pulse passes through the analyzer (first polarization analyzer 9 / second polarization analyzer 13) and reaches the fiber grating (first polarization-maintaining fiber grating 10 / second polarization-maintaining fiber grating 14); at the same time, part of the light in this polarization mode returns to the resonant cavity and reaches the two SESAMs (first SESAM1 / second SESAM2) again, and then reflects multiple times between the fiber grating and the SESAM, and is amplified by the gain medium 6, so as to achieve mode locking and generate stable ultrashort pulse output. If the polarization is inconsistent, the laser pulse cannot pass through the polarization analyzer (the first polarization analyzer 9 / the second polarization analyzer 13), the loss is large, and mode locking cannot be achieved.

[0030] Therefore, the transmission loss of the laser pulse in the laser resonant cavity can be controlled by adjusting the polarization controller. By independently controlling the paddles of the two polarization controllers, the polarization phases of the oscillation modes in the two laser resonant cavities can be independently controlled, which is then converted into the laser transmission loss in the two laser resonant cavities. At the same time, SESAMs with different wavelengths (first wavelength / second wavelength) are used to achieve switching or simultaneous mode locking of the dual wavelengths. That is, by independently controlling the polarization controllers (first polarization controller 8 / second polarization controller 12), the laser transmission loss in the two laser resonant cavities can be independently controlled to obtain controllable control of the two laser mode locking, thereby achieving switchable and tunable separate mode locking output or simultaneous mode locking output.

[0031] like Figure 2-Figure 7 The figure shows that the dual-wavelength lasers of 920nm and 1060nm are outputted simultaneously by using the switchable and tunable dual-wavelength mode-locked fiber laser in any of the above-mentioned embodiments. Figure 2-Figure 4 They are the output pulse sequence, pulse width and spectrum measurement results of 920nm laser; Figure 5-Figure 7 The output pulse sequence, pulse width and spectrum measurement results of the 1060nm laser are shown in Figure 1. It can be seen that the improved switchable and tunable dual-wavelength mode-locked fiber laser of the present invention can simultaneously generate dual-wavelength ultrashort pulse mode-locked lasers.

[0032] Professionals may further appreciate that the units and method steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in the above description according to function. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application.

[0033] In summary, the present invention proposes a switchable tunable dual-wavelength mode-locked fiber laser and a Nd-doped switchable tunable 920nm and 1064nm dual-wavelength mode-locked fiber laser. The switchable tunable dual-wavelength mode-locked fiber laser can generate dual-wavelength ultra-short pulse mode-locked laser by using two SESAMs and two output optical paths combined with pump light gain medium, and at the same time, the dual-wavelength ultra-short pulse mode-locked laser can be outputted in an adjustable manner by controlling the polarization controllers in the two output optical paths, thereby realizing dual-wavelength switching or simultaneous output.

[0034] The above is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be thought of by a person skilled in the art within the technical scope disclosed by the present invention without creative work should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope defined in the claims.

Claims

1. A switchable and tunable dual-wavelength mode-locked fiber laser, characterized in that: The laser includes a mode-locked oscillation subsystem and a mode-locked output subsystem; The mode-locked oscillation subsystem is used to generate dual-wavelength ultrashort pulse mode-locked laser, comprising a first SESAM (1), a second SESAM (2), a polarization-maintaining beam splitter (3), a pump source (4), a wavelength division multiplexer (5), and a gain medium (6); the mode-locked output subsystem is used to output the dual-wavelength ultrashort pulse mode-locked laser in an adjustable manner, comprising a non-polarization-maintaining beam splitter (7), a first wavelength output optical path, and a second wavelength output optical path.

2. A switchable and tunable dual-wavelength mode-locked fiber laser according to claim 1, characterized in that: as stated; The first SESAM (1) and the second SESAM (2) are connected to a first port of a wavelength division multiplexer (5) via a polarization-maintaining beam splitter (3); the second port of the wavelength division multiplexer (5) is connected to a pump source (4), and the third port of the wavelength division multiplexer (5) is connected to a gain medium (6) for introducing pump light emitted by the pump source (4) into the gain medium (6), exciting the gain medium (6) to achieve population inversion, and generating ultrashort laser pulses.

3. The switchable and tunable dual-wavelength mode-locked fiber laser according to claim 2, characterized in that: The first wavelength output optical path is formed by connecting a first polarization controller (8), a first polarization analyzer (9), a first polarization-maintaining fiber grating (10) and a first polarization-maintaining isolator (11) in sequence in the direction of the optical path; the second wavelength output optical path is formed by connecting a second polarization controller (12), a second polarization analyzer (13), a second polarization-maintaining fiber grating (14) and a second polarization-maintaining isolator (15) in sequence in the direction of the optical path; and the first wavelength output optical path and the second wavelength output optical path are connected to the gain medium (6) via a non-polarization-maintaining beam splitter (7).

4. The switchable and tunable dual-wavelength mode-locked fiber laser according to claim 3, characterized in that: The wavelength parameters of the first SESAM (1) and the first wavelength output optical path are both the first wavelength; the wavelength parameters of the second SESAM (2) and the second wavelength output optical path are both the second wavelength; and the first wavelength and the second wavelength match the emission wavelength of the gain medium (6).

5. The switchable and tunable dual-wavelength mode-locked fiber laser according to claim 4, characterized in that: The first wavelength is 920 nm and the second wavelength is 1064 nm.

6. The switchable and tunable dual-wavelength mode-locked fiber laser according to claim 5, characterized in that: In the mode-locked oscillation subsystem, the first SESAM (1) is a SESAM for 920 nm laser mode-locking, the second SESAM (2) is a second SESAM (2) for 1064 nm laser mode-locking, and the gain medium (6) is an Nd-doped gain fiber.

7. The switchable and tunable dual-wavelength mode-locked fiber laser according to claim 6, characterized in that: In the first wavelength output optical path, the first polarization-maintaining fiber grating (10) is a 920 nm polarization-maintaining fiber grating, and the first polarization-maintaining isolator (11) is a 920 nm polarization-maintaining isolator; In the second wavelength output optical path, the second polarization-maintaining fiber grating (14) is a 1064 nm polarization-maintaining fiber grating, and the second polarization-maintaining isolator (15) is a 1064 nm polarization-maintaining isolator.

8. The switchable and tunable dual-wavelength mode-locked fiber laser according to claim 6, characterized in that: The transmittance of the first polarization-maintaining optical fiber grating (10) is less than 80%, and the reflectivity is greater than 20%; the transmittance of the second polarization-maintaining optical fiber grating (14) is less than 80%, and the reflectivity is greater than 20%.

9. A debugging method for a switchable and tunable dual-wavelength mode-locked fiber laser according to any one of claims 1 to 8, characterized in that: By independently controlling the first polarization controller (8) and / or the second polarization controller (12) in the two output optical paths, the magnitude of the laser transmission loss in the two laser resonant cavities is controlled, and controllable control of the two laser mode locking is obtained, thereby achieving switchable and tunable separate mode locking output or simultaneous mode locking output.

10. The debugging method of a switchable and tunable dual-wavelength mode-locked fiber laser according to claim 9, characterized in that: The first polarization controller (8) and / or the second polarization controller (12) are adjusted to change the birefringence of the optical fiber by squeezing and deforming the optical fiber, so that when the light passes through the optical fiber, an additional phase is generated to change the polarization mode of the laser in the resonant cavity, and then the first polarization analyzer (9) / the second polarization analyzer (13) performs polarization analysis; if the polarization directions are consistent, the laser pulse passes through the first polarization analyzer (9) / the second polarization analyzer (13) and reaches the first polarization-maintaining fiber grating (10) / the second polarization-maintaining fiber grating (14); at the same time, part of the light in this polarization mode returns to the resonant cavity and reaches the first SESAM (1) / the second SESAM (2) again, and then is reflected multiple times between the fiber grating and the SESAM, and is amplified by the gain medium (6), so as to achieve mode locking and generate stable ultrashort pulse output.

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