Linearly polarized laser amplification device and method based on non-polarization maintaining gain fiber

Abstract

The application relates to the field of laser technology and provides a linear polarization laser amplification device and method based on a non-polarization-maintaining gain optical fiber, which comprises a laser seed source, a polarization beam splitter, a 1 / 4 wave plate, a fiber collimator, a gain optical fiber, a fiber end face dichroic mirror and a pump source; horizontal polarization laser emitted by the laser seed source is changed into circular polarization laser after passing through the polarization beam splitter and the 1 / 4 wave plate; the circular polarization laser is coupled to the non-polarization-maintaining gain optical fiber through the fiber collimator to perform first power amplification, is reflected back to the non-polarization-maintaining gain optical fiber through the fiber end face dichroic mirror to perform second power amplification, is collimated through the fiber collimator, is changed into vertical polarization light through the 1 / 4 wave plate, is reflected and output through the polarization beam splitter, and linear polarization laser power is improved, so that the technical blank of amplifying linear polarization laser power by using the non-polarization-maintaining gain optical fiber is filled, the application has the advantages of simplicity, reliability, easy operation and easy application, and is especially suitable for power improvement of visible light band linear polarization laser.

Description

Technical Field

[0001] This invention relates primarily to the field of laser technology, and in particular to a linearly polarized laser amplification device and method based on non-polarization-maintaining gain fiber. Background Technology

[0002] In the field of laser technology, high-power linearly polarized visible lasers have attracted widespread attention due to their important roles in applications such as special processing, biomedical imaging, precision measurement, and remote sensing. However, traditional methods for generating visible linearly polarized lasers mainly rely on the nonlinear frequency conversion of near-infrared polarized lasers. This process is not only complex and costly, but also has low conversion efficiency and poor beam quality. These limitations restrict its wider application.

[0003] Polarization-maintaining fiber laser amplifiers in the visible light band are considered one of the ideal solutions for achieving efficient, high-power linearly polarized laser output due to the inherent advantages of optical fibers, such as high efficiency, high power output, and good beam quality. However, obtaining high-power linearly polarized fiber laser output usually requires the use of expensive polarization-maintaining gain fibers to ensure that the polarization state is not affected by external disturbances during amplification. But in the visible light band, especially at specific wavelengths such as deep red light, the selection of high-performance, large-mode-area polarization-maintaining gain fibers is extremely limited. Since polarization-maintaining gain fibers in the visible light band have not yet been developed, or even exist, traditional polarization-maintaining fiber amplifier solutions still face significant challenges in the visible light band. Summary of the Invention

[0004] To address the limitations of existing technologies, this invention proposes a linearly polarized laser amplification device and method based on non-polarization-maintaining gain fiber. This invention ingeniously combines laser polarization control with visible light non-polarization-maintaining fiber laser amplification technology, enabling the direct generation of efficient, high-power linearly polarized laser output in the visible light band. This technology is expected to overcome the limitations of existing technologies, promote the development of high-power visible light band linearly polarized lasers, and bring new application opportunities to related fields.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: On one hand, the present invention provides a linearly polarized laser amplification device based on a non-polarization-maintaining gain fiber, comprising a laser seed source, a polarization beam splitter, a quarter-wave plate, a fiber collimator, a non-polarization-maintaining gain fiber, a fiber end-face dichroic mirror, and a pump source; the laser seed source is used to emit horizontally polarized laser in the visible light band; the polarization beam splitter and the quarter-wave plate are arranged sequentially, the fiber collimator is connected to one end of the non-polarization-maintaining gain fiber, the other end of the non-polarization-maintaining gain fiber is connected to the fiber end-face dichroic mirror through a ceramic sleeve, and the output pigtail of the pump source is fused to the pigtail of the fiber end-face dichroic mirror to couple the pump light into the non-polarization-maintaining gain fiber.

[0006] Furthermore, the wavelength range of the laser seed source is the visible light band of 380nm-780nm.

[0007] Furthermore, the linearly polarized laser is either a continuous wave or a pulsed linearly polarized laser, wherein the pulse width of the pulsed linearly polarized laser is femtosecond, picosecond, or nanosecond.

[0008] Furthermore, the polarization beam splitter operates in the visible light band and has a polarization extinction ratio greater than 1000:1.

[0009] Furthermore, the pump source is a semiconductor laser, and the laser wavelength of the semiconductor laser is between 440nm and 455nm.

[0010] Furthermore, the non-polarization-maintaining gain fiber is a non-polarization-maintaining rare-earth-doped fluoride fiber.

[0011] Furthermore, the dopant ion of the double-clad rare-earth-doped fluoride optical fiber is praseodymium (Pr). 3+ ) or holmium (Ho) 3+ Ions, with a concentration range of 1000 ppm-10000 ppm.

[0012] Furthermore, the fiber end face dichroic mirror is a fiber end face dielectric film mirror with high signal light reflectivity and high pump light transmittance.

[0013] Furthermore, the pigtail of the optical fiber end face dielectric film mirror is a multimode optical fiber with a core / cladding diameter of 105 / 125 μm, and the core / cladding diameter of the optical fiber pigtail of the pump source is 105 / 125 μm.

[0014] On the other hand, the linear polarization laser amplification method based on the above-mentioned linear polarization laser amplification device using non-polarization-maintaining gain fiber includes the following steps: The horizontally polarized laser in the visible light band emitted by the laser seed source is converted into a circularly polarized laser after passing through a polarization beam splitter and a quarter-wave plate. The circularly polarized laser is coupled to the non-polarization-maintaining gain fiber via an optical fiber collimator for primary power amplification, and then reflected back to the non-polarization-maintaining gain fiber via a dichroic mirror at the fiber end face for secondary power amplification. After secondary power amplification, the circularly polarized laser is collimated by the fiber collimator and then converted into vertically polarized light by a quarter-wave plate. Finally, it is reflected and output by a polarization beam splitter, thereby achieving power enhancement of the linearly polarized laser in the visible light band.

[0015] Compared with the prior art, the technical effects of the present invention are as follows: This invention presents a visible-light polarized laser output scheme that cleverly avoids the need for polarization-maintaining gain fibers, directly employing standard, lower-cost, more readily available, and more widely selectable non-polarization-maintaining gain fibers. The laser seed source in this invention emits horizontally polarized laser light in the visible light band. A polarization beam splitter and a quarter-wave plate convert the horizontally polarized seed laser into a circularly polarized laser. After efficient fiber laser power amplification, it is then converted into a vertically polarized laser output, thereby achieving power enhancement of linearly polarized laser based on a non-polarization-maintaining fiber laser amplification system. This invention involves a horizontally polarized seed laser → circularly polarized laser amplification → vertically polarized laser output. Circularly polarized light has no fixed polarization direction during transmission, fundamentally avoiding the birefringence disturbance problem of non-polarization-maintaining fibers and completely circumventing the polarization degradation problem caused by random birefringence in traditional linearly polarized amplification. Utilizing the high photon energy and strong nonlinear effects of the visible light band, the circular polarization state suppresses polarization-related nonlinear effects during amplification. The amplified circularly polarized light undergoes a second conversion via a λ / 4 waveplate to generate high-purity vertically polarized light. This invention not only avoids the polarization disturbance problem of non-polarization-maintaining fibers but also achieves polarization direction reversal in the output. It cleverly combines laser polarization control with visible light non-polarization-maintaining fiber laser amplification technology, directly achieving efficient, high-power linearly polarized laser output in the visible light band. This technological breakthrough is expected to overcome the limitations of existing technologies, promote the development of high-power visible light band linearly polarized lasers, and bring new application opportunities to related fields. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0017] Figure 1 A schematic diagram of a linearly polarized laser amplification device based on a non-polarization-maintaining gain fiber, provided as an embodiment; Figure 2 Here is a picosecond laser seed source spectrum in one embodiment; Figure 3 Here is an autocorrelation trace of a picosecond laser seed source pulse in one embodiment; Figure 4 This is a diagram showing the output power and pulse energy of a deep red polarized picosecond laser after power amplification in one embodiment. Figure 5 This is a spectrum and pulse autocorrelation trace of a deep-red polarized picosecond laser after power amplification in one embodiment, wherein... Figure 5 (a) is the spectrum of the deep red polarized picosecond laser after power amplification. Figure 5 (b) is the pulse autocorrelation trace of a deep red polarized picosecond laser after power amplification.

[0018] Numbering on the map: 1. Laser seed source; 2. Polarization beam splitter; 3. Quarter wave plate; 4. Fiber collimator; 5. Non-polarization-maintaining gain fiber; 6. Fiber end face dichroic mirror; 7. Pump source. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] In one embodiment, such as Figure 1 As shown, the present invention provides a linearly polarized laser amplification device based on non-polarization-maintaining gain fiber, including a laser seed source 1, a polarization beam splitter 2, a quarter-wave plate 3, an optical fiber collimator 4, a non-polarization-maintaining gain fiber 5, an optical fiber end face dichroic mirror 6, and a pump source 7.

[0021] The laser seed source 1 is used to emit horizontally polarized laser light in the visible light band; the polarization beam splitter 2 and the quarter-wave plate 3 are arranged in sequence; the fiber collimator 4 is connected to one end of the non-polarization-maintaining gain fiber 5; the other end of the non-polarization-maintaining gain fiber 5 is connected to the fiber end face dichroic mirror 6 through a ceramic sleeve; the output pigtail of the pump source 7 is fused to the output pigtail of the fiber end face dichroic mirror 6 to couple the pump light into the non-polarization-maintaining gain fiber 5.

[0022] The linear polarization laser amplification method based on the non-polarization-maintaining gain fiber in the above-mentioned linear polarization laser amplification device includes: the horizontally polarized laser (p-light) in the visible light band emitted by the laser seed source 1 is converted into circularly polarized laser after passing through the polarization beam splitter 2 and the quarter-wave plate 3; the circularly polarized laser is coupled into the non-polarization-maintaining gain fiber 5 through the fiber collimator 4, during which the circularly polarized laser undergoes a power amplification; then it is reflected back to the non-polarization-maintaining gain fiber 5 through the fiber end face dichroic mirror 6 for a second power amplification; after the second power amplification, the circularly polarized laser is collimated by the fiber collimator 4 and then incident on the quarter-wave plate 3 to be converted into vertically polarized laser (s-light); finally, it is reflected and output through the polarization beam splitter 2, thereby realizing the power enhancement of the linearly polarized laser in the visible light band.

[0023] Furthermore, the horizontally polarized laser provided by the laser seed source has a wavelength range of 380-780 nm in the visible light band, and the linearly polarized laser can be a continuous-wave linearly polarized laser or a pulsed linearly polarized laser. The pulse width of the pulsed linearly polarized laser can be femtosecond, picosecond, or nanosecond.

[0024] The polarization beam splitter operates in the visible light band and has a polarization extinction ratio greater than 1000:1. The quarter-wave plate can realize the polarization characteristic conversion of linearly polarized lasers. The quarter-wave plate and the polarization beam splitter can form an isolator to isolate backlight damage and protect the laser seed source.

[0025] The gain fiber is a non-polarity-maintaining double-clad rare-earth-doped fluoride fiber, and the doped rare-earth ions can be praseodymium (Pr). 3+ ) or holmium (Ho) 3+ Ions, with a concentration range of 1000ppm-10000ppm.

[0026] The fiber end-face dichroic mirror is a fiber end-face dielectric film mirror made by depositing multiple dielectric films on the end face of a multimode fiber. It has high reflectivity for signal light and high transmittance for pump light. The core / cladding diameter of the multimode fiber is 105 / 125 μm. The pump source is a semiconductor laser output from a multimode fiber pigtail, with a laser wavelength of 440 nm-455 nm blue light. The fiber core / cladding diameter is also 105 / 125 μm.

[0027] To demonstrate the effectiveness of the present invention, in one embodiment, based on Figure 1 The structure of the linearly polarized laser amplification device based on non-polarization-maintaining gain fiber shown is configured as follows: In this embodiment, the laser seed source 1 is a deep red mode-locked fiber laser, which can output horizontally polarized laser (p-light) with a pulse width on the order of picoseconds. Its spectrum and pulse autocorrelation trace are as follows: Figure 2 and Figure 3 As shown, its center wavelength is 716.6 nm, its spectral bandwidth is 6.45 nm, and its pulse width is 7.11 ps. Furthermore, the repetition frequency of the laser pulse is approximately 75 MHz, and the output power is approximately ~100 mW.

[0028] In this embodiment, the non-polarity-maintaining gain fiber 5 is a double-clad praseodymium-doped fiber, with the following specific parameters: Pr 3+ The doping concentration is 8000 ppm, the core NA is 0.08, the core diameter is 7.5 μm, and the inner cladding (double D-type) dimensions are as follows: .

[0029] In this embodiment, the pump source 7 is a blue semiconductor laser whose wavelength matches the absorption spectrum of the non-polarization-maintaining gain fiber, with an output laser center wavelength of 443 nm and an output pigtail core diameter / cladding diameter of 105 / 125 μm.

[0030] In this embodiment, the fiber end face dichroic mirror 6 has a high transmittance of >95% in the blue light band and a high reflectance of >99.5% in the deep red light band.

[0031] For the reverse secondary amplified output laser, the quarter-wave plate 3 and the polarization beam splitter 2 in this embodiment together constitute an isolator to isolate possible backlight damage and protect the laser seed source.

[0032] In this embodiment, the circularly polarized laser, after being amplified twice, is collimated by the fiber collimator 4 and then incident on the quarter-wave plate 3 to be converted into a vertically polarized laser (S-beam), which is then reflected and output by the polarization beam splitter 2.

[0033] In this embodiment, the output power and pulse energy of the deep red polarized picosecond laser after power amplification are as follows: Figure 4 As shown. By Figure 4 It can be seen that when the pump power increases from 0 W to 6.9 W, the output power of the amplified deep-red polarized picosecond laser increases from 0.091 W to 1.17 W, while the pulse energy increases from 1.2 nJ to 15.6 nJ, representing an order of magnitude increase in both power and pulse energy. Furthermore, in this embodiment, if the pump power is further increased, there is a possibility that the amplified picosecond laser may damage the dichroic mirror at the fiber end face.

[0034] In this embodiment, the output spectrum and pulse autocorrelation trace of the deep red polarized picosecond laser after power amplification are as follows: Figure 5 As shown, where Figure 5 (a) is the spectrum of the deep red polarized picosecond laser after power amplification. Figure 5 (b) is the pulse autocorrelation trace of a deep-red polarized picosecond laser after power amplification. Figure 5 It can be seen that as the pump power increases, the 3 dB bandwidth and pulse width of the deep red light-polarized picosecond laser output spectrum both become narrower.

[0035] Traditional high-power linearly polarized fiber lasers typically use polarization-maintaining fibers because non-polarization-maintaining fibers are easily disturbed during amplification, leading to polarization instability. However, polarization-maintaining fibers are expensive, have limited selection in the visible light band, and are particularly lacking in suitable polarization-maintaining gain fibers for deep red light. This invention proposes a linearly polarized laser amplification device and method based on non-polarization-maintaining gain fibers. This method fully utilizes the laser polarization characteristics and, combined with non-polarization-maintaining fiber laser amplification technology, directly achieves high-power linearly polarized deep red picosecond laser output in the visible light band.

[0036] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0037] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these modifications and improvements all fall within the protection scope of this application.

[0038] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A linearly polarized laser amplification device based on non-polarization-maintaining gain fiber, characterized in that, The system includes a laser seed source, a polarization beam splitter, a quarter-wave plate, an optical fiber collimator, a non-polarization-maintaining gain fiber, an optical fiber end-face dichroic mirror, and a pump source. The laser seed source is used to emit horizontally polarized laser light in the visible light band. The polarization beam splitter and the quarter-wave plate are arranged sequentially. The optical fiber collimator is connected to one end of the non-polarization-maintaining gain fiber, and the other end of the non-polarization-maintaining gain fiber is connected to the optical fiber end-face dichroic mirror through a ceramic sleeve. The output pigtail of the pump source is fused to the pigtail of the optical fiber end-face dichroic mirror to couple the pump light into the non-polarization-maintaining gain fiber.

2. The linearly polarized laser amplification device based on non-polarization-maintaining gain fiber according to claim 1, characterized in that, The wavelength range of the laser seed source is 380nm-780nm in the visible light band.

3. The linearly polarized laser amplification device based on non-polarization-maintaining gain fiber according to claim 2, characterized in that, Linearly polarized lasers can be either continuous wave or pulsed linearly polarized lasers, with pulse widths of femtoseconds, picoseconds, or nanoseconds.

4. The linearly polarized laser amplification device based on non-polarization-maintaining gain fiber according to claim 2, characterized in that, The polarization beam splitter operates in the visible light band and has a polarization extinction ratio greater than 1000:

1.

5. The linearly polarized laser amplification device based on non-polarization-maintaining gain fiber according to any one of claims 2 to 4, characterized in that, The pump source is a semiconductor laser, and the laser wavelength of the semiconductor laser is between 440 nm and 455 nm.

6. The linearly polarized laser amplification device based on non-polarization-maintaining gain fiber according to claim 5, characterized in that, The non-polarization-maintaining gain fiber is a non-polarization-maintaining rare-earth-doped fluoride fiber.

7. The linearly polarized laser amplification device based on non-polarization-maintaining gain fiber according to claim 6, characterized in that, The dopant ion of the double-clad rare-earth-doped fluoride optical fiber is Pr. 3+ Ions or Ho 3+ Ions, with a concentration range of 1000ppm-10000ppm.

8. The linearly polarized laser amplification device based on non-polarization-maintaining gain fiber according to claim 6, characterized in that, The fiber end face dichroic mirror is a fiber end face dielectric film mirror with high reflectivity for signal light and high transmittance for pump light.

9. The linearly polarized laser amplification device based on non-polarization-maintaining gain fiber according to claim 6, characterized in that, The fiber end face dielectric film mirror has a multimode fiber pigtail with a core / cladding diameter of 105 / 125 μm, and the pump source has a fiber pigtail with a core / cladding diameter of 105 / 125 μm.

10. The linear polarization laser amplification method based on a non-polarization-maintaining gain fiber linear polarization laser amplification device as described in claim 1, characterized in that, Includes the following steps: The horizontally polarized laser in the visible light band emitted by the laser seed source is converted into a circularly polarized laser after passing through a polarization beam splitter and a quarter-wave plate. The circularly polarized laser is coupled to the non-polarization-maintaining gain fiber via an optical fiber collimator for a first power amplification, and then reflected back to the non-polarization-maintaining gain fiber via a dichroic mirror at the fiber end face for a second power amplification. After secondary power amplification, the circularly polarized laser is collimated by the fiber collimator and then converted into vertically polarized light by a quarter-wave plate. Finally, it is reflected and output by a polarization beam splitter, thereby achieving power enhancement of linearly polarized laser in the visible light band.

Images