Spectrum smooth output system and method based on polarization-maintaining chirp fiber Bragg grating

Abstract

The invention relates to a spectrum smooth output system and method based on a polarization-maintaining chirp fiber bragg grating, and the system comprises a pumping source and a pumping isolator which are connected in sequence, and the pumping isolator is connected to a polarization-maintaining wavelength division multiplexer. The polarization-maintaining wavelength division multiplexer is connected to the saturable absorber through the polarization-maintaining chirp fiber Bragg grating and the polarization-maintaining gain fiber, and the polarization-maintaining wavelength division multiplexer is also connected with a polarization-maintaining isolator; the pumping source, the pumping isolator and the polarization-maintaining wavelength division multiplexer form an input end of the fiber laser, the polarization-maintaining chirp fiber bragg grating, the polarization-maintaining gain fiber and the saturable absorber form a resonant cavity of the fiber laser, and the polarization-maintaining wavelength division multiplexer and the polarization-maintaining isolator form an output end of the fiber laser. The polarization-maintaining chirp fiber bragg grating and the polarization-maintaining gain fiber are vertically welded, and the polarization-maintaining wavelength division multiplexer and the polarization-maintaining isolator are vertically welded. Compared with the prior art, the device can stably output a smooth seed spectrum, and has the advantages of being compact in structure and easy to integrate.

Description

Technical Field

[0001] The invention relates to the technical field of laser spectroscopy, and in particular to a spectrum smoothing output system based on a polarization-maintaining chirped Bragg fiber grating and a method thereof. Background Art

[0002] Ultrafast lasers, with their narrow pulse width and high peak power, can process high-precision materials without causing thermal damage. They are currently commonly used in the production of micro-mechanical components, circuit boards, etc. Solid-state ultrafast lasers are large in size, expensive, and require complex pump sources and cooling systems, which greatly increases the cost of industrial applications. All-fiber fiber lasers have many advantages, such as compact overall equipment structure, good stability, high energy conversion efficiency, relatively low cost, and simple maintenance. Therefore, they are widely used in skin treatment and precision processing in the aviation field.

[0003] High-power ultrafast lasers are mainly composed of mode-locked lasers and power amplifiers. Among them, mode-locked fiber lasers have the advantages of compact structure, no spatial light regulation, and strong stability. They can be used as pump light sources for two-photon Raman imaging technology, and can also be used as seed sources for laser amplification. Since the laser of the seed source needs to undergo energy amplification and pulse compression, the better the spectral linearity of the seed source, the better the quality of the final light source. In the prior art, some studies have used specially designed gradient refractive index composite fibers to achieve smoothing of ultrafast spectra. However, this special fiber is difficult to optimize and design, and its preparation process is complex. Other studies have introduced additional nonlinear optics / amplifying loop mirrors into ultrafast fiber laser amplifiers to achieve the purpose of smoothing the laser spectrum, but this approach also increases the complexity of the laser system. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and to provide a spectrum smoothing output system and method based on polarization-maintaining chirped fiber Bragg grating, which can stably output a smooth seed spectrum and has the advantages of compact structure and easy integration.

[0005] The object of the present invention can be achieved by the following technical scheme: a spectrum smoothing output system based on polarization-maintaining chirped Bragg fiber grating, comprising a pump source and a pump isolator connected in sequence, the pump isolator is connected to a polarization-maintaining wavelength division multiplexer, the polarization-maintaining wavelength division multiplexer is connected to a saturable absorber through a polarization-maintaining chirped Bragg fiber grating and a polarization-maintaining gain fiber, and the polarization-maintaining wavelength division multiplexer is also connected to a polarization-maintaining isolator;

[0006] The pump source, pump isolator and polarization-maintaining wavelength division multiplexer together constitute the input end of the fiber laser, the polarization-maintaining chirped fiber Bragg grating, polarization-maintaining gain fiber and saturable absorber together constitute the resonant cavity of the fiber laser, and the polarization-maintaining wavelength division multiplexer and polarization-maintaining isolator constitute the output end of the fiber laser.

[0007] Furthermore, the polarization-maintaining chirped fiber Bragg grating and the polarization-maintaining gain optical fiber are vertically fused.

[0008] Furthermore, the polarization-maintaining wavelength division multiplexer and the polarization-maintaining isolator are vertically fused.

[0009] Furthermore, the pump isolator is connected to a REF terminal of a polarization-maintaining wavelength division multiplexer.

[0010] Furthermore, the COM end of the polarization-maintaining wavelength division multiplexer is connected to a polarization-maintaining chirped fiber Bragg grating.

[0011] Furthermore, the PASS end of the polarization-maintaining wavelength division multiplexer is connected to a polarization-maintaining isolator.

[0012] Furthermore, the pump source is specifically a semiconductor laser, which is used to output pump light.

[0013] Furthermore, the polarization-maintaining gain optical fiber is specifically an optical fiber doped with ytterbium (Yb) rare ions.

[0014] A spectrum smoothing output method based on a polarization-maintaining chirped Bragg fiber grating, comprising:

[0015] The pump light output by the pump source is coupled into the polarization-maintaining chirped Bragg fiber grating through the pump isolator and the polarization-maintaining wavelength division multiplexer. The pump light is gain-amplified through the polarization-maintaining gain fiber to generate a new signal laser. The signal laser is transmitted to the saturable absorber through the polarization-maintaining gain fiber, reflected by the surface of the saturable absorber and amplified again through the polarization-maintaining gain fiber. A part of the amplified signal light oscillates in the resonant cavity formed between the polarization-maintaining chirped Bragg fiber grating and the saturable absorber, and the other part of the amplified signal light is transmitted to the polarization-maintaining wavelength division multiplexer along the original path, and is coupled to the polarization-maintaining isolator with fast-axis cutoff through the output of the polarization-maintaining wavelength division multiplexer. After filtering by the polarization-maintaining isolator, a smooth laser spectrum is output.

[0016] Furthermore, after the amplified signal light is dispersed through a polarization-maintaining chirped Bragg fiber grating, a part of the pulses returns to the resonant cavity through the reflection end of the polarization-maintaining chirped Bragg fiber grating to oscillate again; the other part of the pulses is output through the transmission end of the polarization-maintaining chirped Bragg fiber grating, and the output laser is transmitted from the COM end of the polarization-maintaining wavelength division multiplexer to the PASS end, and the laser spectrum is filtered and processed by the polarization-maintaining isolator to output a smooth laser spectrum.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] The fiber laser designed by the present invention includes a pump source, a pump isolator, a polarization-maintaining wavelength division multiplexer, a polarization-maintaining chirped Bragg fiber grating, a polarization-maintaining gain fiber, a saturable absorber, and a polarization-maintaining isolator, wherein the pump source, the pump isolator, and the polarization-maintaining wavelength division multiplexer constitute the input end of the fiber laser, the polarization-maintaining chirped Bragg fiber grating, the polarization-maintaining gain fiber, and the saturable absorber constitute the laser resonant cavity, and the polarization-maintaining wavelength division multiplexer and the polarization-maintaining isolator constitute the output end of the fiber laser. Thus, an all-fiber spectrum smoothing output system is realized, which has the advantages of compact structure and easy integration, adopts polarization-maintaining fiber as the gain medium, vertically fuses the polarization-maintaining chirped Bragg fiber grating and the polarization-maintaining gain fiber, and vertically fuses the polarization-maintaining wavelength division multiplexer and the polarization-maintaining isolator, which can stably output a smooth spectrum and avoid spectrum interference of signal light. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the system structure of the present invention;

[0020] Figure 2 Schematic diagram of vertical fusion of polarization-maintaining chirped fiber Bragg grating and polarization-maintaining gain fiber;

[0021] Explanation of the marks in the figure: 1. Pump source, 2. Pump isolator, 3. Polarization-maintaining wavelength division multiplexer, 4. Polarization-maintaining chirped fiber Bragg grating, 5. Polarization-maintaining gain fiber, 6. Saturable absorber, 7. Polarization-maintaining isolator. DETAILED DESCRIPTION

[0022] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] Example

[0024] like Figure 1 As shown, a spectrum smoothing output system based on polarization-maintaining chirped Bragg fiber grating includes a pump source 1, a pump isolator 2, a polarization-maintaining wavelength division multiplexer 3, a polarization-maintaining chirped Bragg fiber grating 4, a polarization-maintaining gain fiber 5, a saturable absorber 6 and a polarization-maintaining isolator 7. Figure 1 In the figure, pump is the pump source 1, ISO is the pump isolator 2, WDM is the polarization-maintaining wavelength division multiplexer 3, CFBG is the polarization-maintaining chirped fiber Bragg grating 4, PM:Yb is the polarization-maintaining gain fiber 6, SESAM is the saturable absorber 6, ISO(PM) is the polarization-maintaining isolator 7, REF is the input end of the polarization-maintaining wavelength division multiplexer 3, COM is the common end of the polarization-maintaining wavelength division multiplexer 3, and PASS is the output end of the polarization-maintaining wavelength division multiplexer 3.

[0025] In this embodiment, the pump source 1 is a semiconductor laser with a central wavelength of 976 nm, the polarization-maintaining chirped fiber Bragg grating 4 is a polarization-maintaining fiber with a pigtail of 6 / 125 type, and the polarization-maintaining gain fiber 5 is an optical fiber doped with ytterbium (Yb) ions.

[0026] Specifically, the optical fiber at the output end of the pump source 1 is fused with the optical fiber at the input end of the pump isolator 2, and the output end of the pump isolator 2 is connected to the REF end of the polarization-maintaining wavelength division multiplexer 3 to form the input end of the fiber laser. The COM end of the polarization-maintaining wavelength division multiplexer 3 is sequentially connected to the polarization-maintaining chirped Bragg fiber grating 4, the polarization-maintaining gain fiber 5, and the fiber jumper that fixes the saturable absorber 6 to form a laser resonant cavity, and the PASS end of the polarization-maintaining wavelength division multiplexer 3 is fused with the input end optical fiber of the polarization-maintaining isolator 7 to form the output end of the entire fiber laser. Among them, the input end of the polarization-maintaining chirped Bragg fiber grating 4 and the polarization-maintaining gain fiber 5 are fused together, and the internal structure thereof is as follows: Figure 2 As shown ( Figure 2 The left side shows the end face of the polarization-maintaining chirped Bragg fiber grating. Figure 2 The right side of the figure shows the end face of the polarization-maintaining gain fiber), that is, the internal structures of the two polarization-maintaining fibers are aligned perpendicular to each other. In addition, the PASS end of the polarization-maintaining wavelength division multiplexer 3 and the input end of the polarization-maintaining isolator 7 are also connected as shown in the figure. Figure 2 The method is to align the welds perpendicular to each other.

[0027] In practical applications, the pump light generated by the pump source 1 is transmitted to the REF end of the polarization-maintaining wavelength division multiplexer 3 through the pump isolator 2, and the light of the polarization-maintaining wavelength division multiplexer 3 is transmitted from the REF end to the COM end. The COM end of the polarization-maintaining wavelength division multiplexer 3 is fused with the polarization-maintaining chirped Bragg fiber grating 4, the polarization-maintaining gain fiber 5 and the optical fiber jumper with the fixed saturable absorber 6. The polarization-maintaining chirped Bragg fiber grating 4, the polarization-maintaining gain fiber 5 and the saturable absorber 6 constitute the resonant cavity of the fiber laser. A part of the light energy of the pump light will be gain-amplified by the polarization-maintaining chirped Bragg fiber grating 4, and the other part will be gain-amplified again by the polarization-maintaining gain fiber 5. The gain-amplified pulse is reflected by the saturable absorber 6, and then gain-amplified by the polarization-maintaining gain fiber 5 and the polarization-maintaining chirped Bragg fiber grating 4 in sequence. After the pulse is dispersed by the polarization-maintaining chirped Bragg fiber grating 4, a part of the pulse returns to the resonant cavity through the reflection end of the polarization-maintaining chirped Bragg fiber grating 4 to oscillate again; the other part of the pulse is output through the transmission end of the polarization-maintaining chirped Bragg fiber grating 4, and the amplified signal light is transmitted to the polarization-maintaining wavelength division multiplexer 3 by the original path, and is coupled to the fast-axis cutoff polarization-maintaining isolator 7 through the PASS end output of the polarization-maintaining wavelength division multiplexer 3, and is filtered by the polarization-maintaining isolator 7 to output a smooth laser spectrum.

[0028] In summary, this solution uses polarization-maintaining fiber as the gain medium, vertically fuses the polarization-maintaining chirped Bragg fiber grating and the polarization-maintaining gain fiber, and vertically fuses the polarization-maintaining wavelength division multiplexer and the polarization-maintaining isolator to achieve the function of spectral filtering and avoid spectral interference, and outputs a smooth seed spectrum, which is conducive to the subsequent construction of a femtosecond laser amplifier with femtosecond compression. The present invention has a compact and miniaturized design, high output stability and is easy to integrate.

Claims

1. A spectrum smoothing output system based on polarization-maintaining chirped fiber Bragg grating, characterized in that: The invention comprises a pump source (1) and a pump isolator (2) connected in sequence, wherein the pump isolator (2) is connected to a polarization-maintaining wavelength division multiplexer (3), the polarization-maintaining wavelength division multiplexer (3) is connected to a saturable absorber (6) via a polarization-maintaining chirped Bragg fiber grating (4) and a polarization-maintaining gain fiber (5), and the polarization-maintaining wavelength division multiplexer (3) is also connected to a polarization-maintaining isolator (7); The pump source (1), the pump isolator (2) and the polarization-maintaining wavelength division multiplexer (3) together constitute the input end of the fiber laser, the polarization-maintaining chirped Bragg fiber grating (4), the polarization-maintaining gain fiber (5) and the saturable absorber (6) together constitute the resonant cavity of the fiber laser, and the polarization-maintaining wavelength division multiplexer (3) and the polarization-maintaining isolator (7) constitute the output end of the fiber laser.

2. The spectrum smoothing output system based on polarization-maintaining chirped fiber Bragg grating according to claim 1, characterized in that: The polarization-maintaining chirped Bragg fiber grating (4) and the polarization-maintaining gain optical fiber (5) are vertically fused.

3. The spectrum smoothing output system based on polarization-maintaining chirped fiber Bragg grating according to claim 1, characterized in that: The polarization-maintaining wavelength division multiplexer (3) and the polarization-maintaining isolator (7) are vertically fused.

4. The spectrum smoothing output system based on polarization-maintaining chirped fiber Bragg grating according to claim 1, characterized in that: The pump isolator (2) is connected to the REF end of the polarization-maintaining wavelength division multiplexer (3).

5. The spectrum smoothing output system based on polarization-maintaining chirped fiber Bragg grating according to claim 1, characterized in that: The COM end of the polarization-maintaining wavelength division multiplexer (3) is connected to a polarization-maintaining chirped Bragg fiber grating (4).

6. The spectrum smoothing output system based on polarization-maintaining chirped fiber Bragg grating according to claim 1, characterized in that: The PASS end of the polarization-maintaining wavelength division multiplexer (3) is connected to a polarization-maintaining isolator (7).

7. The spectrum smoothing output system based on polarization-maintaining chirped fiber Bragg grating according to claim 1, characterized in that: The pump source (1) is specifically a semiconductor laser, which is used to output pump light.

8. The spectrum smoothing output system based on polarization-maintaining chirped fiber Bragg grating according to claim 1, characterized in that: The polarization-maintaining gain optical fiber (5) is specifically an optical fiber doped with ytterbium rare ions.

9. A spectrum smoothing output method based on a polarization-maintaining chirped Bragg fiber grating, applied to a spectrum smoothing output system based on a polarization-maintaining chirped Bragg fiber grating as claimed in claim 1, characterized in that: include: The pump light output by the pump source is coupled into the polarization-maintaining chirped Bragg fiber grating through the pump isolator and the polarization-maintaining wavelength division multiplexer. The pump light is gain-amplified through the polarization-maintaining gain fiber to generate a new signal laser. The signal laser is transmitted to the saturable absorber through the polarization-maintaining gain fiber, reflected by the surface of the saturable absorber and amplified again through the polarization-maintaining gain fiber. A part of the amplified signal light oscillates in the resonant cavity formed between the polarization-maintaining chirped Bragg fiber grating and the saturable absorber, and the other part of the amplified signal light is transmitted to the polarization-maintaining wavelength division multiplexer along the original path, and is coupled to the polarization-maintaining isolator with fast-axis cutoff through the output of the polarization-maintaining wavelength division multiplexer. After filtering by the polarization-maintaining isolator, a smooth laser spectrum is output.

10. The spectrum smoothing output method based on polarization-maintaining chirped Bragg fiber grating according to claim 9, characterized in that: Specifically, the amplified signal light is dispersed through a polarization-maintaining chirped Bragg fiber grating, and a portion of the pulses returns to the resonant cavity through the reflection end of the polarization-maintaining chirped Bragg fiber grating to oscillate again; the other portion of the pulses is output through the transmission end of the polarization-maintaining chirped Bragg fiber grating, and the output laser is transmitted from the COM end of the polarization-maintaining wavelength division multiplexer to the PASS end, and the laser spectrum is filtered and processed by the polarization-maintaining isolator, and a smooth laser spectrum is output.

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