CN211508173U - Multi-wavelength fiber laser based on multi-granularity quantum dot doping - Google Patents

Abstract

The embodiment of the present utility model discloses a multi-wavelength fiber laser based on multi-granularity quantum dot doping, comprising a gain fiber, a first single-mode fiber and a first single-mode fiber connected at both ends of the gain fiber, the first single-mode fiber. The core of the single-mode fiber is engraved with a first composite fiber grating, the core of the second single-mode fiber is engraved with a second composite fiber grating, and the first composite fiber grating and the second composite fiber grating are combined into an optical fiber The grating pair forms the laser feedback cavity mirror. The utility model utilizes the multi-particle quantum dot doped optical fiber as the gain medium, and completes the preparation of the multi-wavelength composite cavity mirror by means of ultra-fast light first laser writing, thereby realizing the multi-wavelength fiber laser.

Description

A multi-wavelength fiber laser based on multi-grain quantum dot doping

technical field

The embodiments of the utility model belong to the field of fiber optics engineering, and particularly relate to a multi-wavelength fiber laser based on multi-granularity quantum dot doping.

Background technique

At present, the mature high-power fiber lasers that account for more than half of the market share and are used for optical communication, the output wavelengths are mainly concentrated in the vicinity of 1060nm and 1550nm. The simplification of the output wavelength limits the application of fiber lasers in more fields, especially the important wavelength band-visible light band. In recent years, lasers in the visible light band have developed rapidly, and are used in biomedical optics (such as laser eye surgery, vascular disease treatment, super-resolution fluorescence imaging, etc.), optical storage, laser color display, laser precision machining, and as an optical parametric oscillator. It has a wide range of applications in terms of pumping sources. In particular, the current research on laser illumination and visible light communication (LiFi) is also attracting more forces to join the research of visible light lasers. For fiber lasers, it is difficult to directly obtain visible light output due to the limitation of doping rare earth elements in the gain fiber. With the advancement of fiber technology and the development of material science, it has been found that fiber lasers can achieve near-infrared and visible light band laser output through high-power pumping and frequency up-conversion effects. In addition to the traditional quartz active fibers, fluoride rare earth doped fibers are widely used in the research of visible light fiber lasers. Through the doping of different elements (Er, Ti, Pr, Nd, etc.), the fiber laser based on fluoride fiber can realize the output of various wavelengths from 400nm to 800nm, and the maximum output power can reach 1W. Although the visible light output of optical fiber can be realized by frequency up-conversion, there are many problems, such as low optical power conversion efficiency (<20%), high power and wavelength requirements of the pump source, limited output wavelength selection, fluoride compounds It is difficult to prepare fiber grating cavity mirrors on optical fibers, and it is difficult to splicing with ordinary single-mode fibers, etc., and further research and solutions are needed.

Utility model content

In view of this, the embodiment of the present invention provides a multi-wavelength fiber laser based on multi-granularity quantum dot doping, which solves the limited output wavelength selection and the difficulty in preparing fiber grating cavity mirrors on fluoride fibers in the related art, which is incompatible with ordinary single-mode fibers. Difficulty welding, etc.

The technical scheme adopted in the embodiment of the present utility model is as follows:

The embodiment of the present invention provides a multi-wavelength fiber laser based on multi-granularity quantum dot doping, comprising a gain fiber, a first single-mode fiber and a first single-mode fiber connected at both ends of the gain fiber, and the first single-mode fiber is The core of the mode fiber is engraved with a first composite fiber grating, the core of the second single-mode fiber is engraved with a second composite fiber grating, and the first composite fiber grating and the second composite fiber grating are combined into a fiber grating Yes, form a laser feedback cavity mirror.

Further, the core of the gain fiber is doped with quantum dots.

Further, the quantum dots are quantum dots subjected to Q frequency shift processing.

Further, the quantum dots have different particle sizes.

Further, the first composite fiber grating has fiber gratings with different periods.

Further, the second composite fiber grating has fiber gratings with different periods.

The embodiments of the present utility model have the following beneficial effects:

1. The embodiment of the present utility model utilizes quantum dot gain fiber to cooperate with fiber grating cavity mirror preparation technology to realize the scheme of fiber laser output. In terms of preparation means, it overcomes the difficulty of splicing fluoride fiber and ordinary single-mode fiber, and it is difficult to directly connect it to the fiber laser. It is difficult to realize the preparation of fiber grating cavity mirror.

2. Enriched the output band of the fiber laser. Due to the limitation of the fluorescence spectrum of the gain medium, traditional fiber lasers require frequency up-conversion to achieve visible light laser output. There are problems such as low optical power conversion efficiency, high requirements for the power and wavelength of the pump source, and limited output wavelength selection. The embodiment of the present invention utilizes quantum dots as gain medium to realize visible light quantum dot fiber laser. By adjusting the size of the doped quantum dots and cooperating with the corresponding cavity mirror, the laser output of any wavelength in the visible light region can be realized, which greatly broadens the working wavelength of the fiber laser.

3. In the example of the present utility model, it is proposed to use quantum dots of different sizes processed by Q-translation technology for co-doping preparation, and with the corresponding composite cavity mirror, the simultaneous output of multiple wavelengths can be realized. In particular, the output of three wavelengths of red, green and blue can realize a quasi-white fiber laser. Compared with the current generation of primary color synthetic white light laser output by several independent lasers, the unnecessary bulky device is reduced, the difficulty of coaxial light is avoided, the structure is compact, the electromagnetic interference resistance is low, and the cost is low.

Description of drawings

The accompanying drawings described here are used to provide a further understanding of the present utility model and constitute a part of the present utility model. The schematic embodiments of the present utility model and their descriptions are used to explain the present utility model and do not constitute an improper limitation to the present utility model. . In the attached image:

1 is a schematic structural diagram of a multi-wavelength fiber laser based on multi-granularity quantum dot doping provided by an embodiment of the present invention;

Fig. 2 is a schematic cross-sectional view at the first composite fiber grating in Fig. 1;

FIG. 3 is a schematic diagram of a preparation process of a multi-wavelength fiber laser provided by an embodiment of the present invention.

Detailed ways

In order to make the purposes, technical solutions and advantages of the embodiments of the present utility model clearer, the technical solutions of the embodiments of the present utility model will be clearly and completely described below with reference to the specific examples of the embodiments of the present utility model and the corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments in the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the embodiments of the present invention.

1 is a schematic structural diagram of a multi-wavelength fiber laser based on multi-granularity quantum dot doping provided by an embodiment of the present utility model; FIG. 2 is a cross-sectional view at the first composite fiber grating in FIG. 1; an embodiment of the present utility model provides a A multi-wavelength fiber laser based on multi-granularity quantum dot doping, comprising a gain fiber 4 and a first single-mode fiber 1 and a first single-mode fiber 7 connected at both ends of the gain fiber 4, the first single-mode fiber 1 The first composite fiber grating 3 is engraved at the core 2 of the second single-mode fiber 7, and the second composite fiber grating 6 is engraved at the core 8 of the second single-mode fiber 7. The first composite fiber grating 3 and the second composite fiber grating 6 are combined into fiber grating pairs to form a laser feedback cavity mirror.

A further technical solution is that the core 5 of the gain fiber 4 is doped with quantum dots.

A further technical solution is that the quantum dots are quantum dots that have undergone Q frequency shift processing to ensure that the emission peak and the absorption peak do not overlap, and secondary absorption does not occur; the quantum dots have different particle sizes, which satisfy the laser output wavelength and gain. Full coverage.

A further technical solution is that the first composite fiber grating 3 has fiber gratings with different periods; the second composite fiber grating 6 has fiber gratings with different periods.

3 is a schematic diagram of a multi-wavelength fiber laser preparation process provided by an embodiment of the present invention; the design method includes:

(1) According to the required laser output wavelength requirements (wavelength number i, wavelength λ _i , i=1, 2, 3...), select fibers doped with quantum dots of different particle sizes as gain fibers to ensure that the gain bandwidth covers the output wavelength The frequency band where it is located; the gain fiber is the basic component of the fiber laser and completes the amplification of the laser.

In particular, in the quantum dot-doped gain fiber 4, the quantum dots doped in the core region 5 of the quantum dots have undergone Q-shift processing, so that the fluorescence emission peak and the absorption peak do not overlap, so as to avoid secondary absorption; At the same time, according to the number of output wavelengths, the corresponding fluorescence peaks of different particle sizes, that is, quantum of different sizes, match the desired output wavelengths one by one.

(2) Determine the length L of the gain fiber according to the requirements of the output power P and the longitudinal mode interval Δυ of the laser operation, and splicing the first single-mode fiber 1 and the second single-mode fiber 7 at both ends of the gain fiber respectively;

Among them, the output power of the fiber P∝L, and the longitudinal mode interval Δυ is expressed as follows:

where c is the speed of light, n is the effective refractive index of the laser transmitted in the fiber, and _Leff is the equivalent cavity length introduced by the fiber grating pair. Combined with the power output power P and the laser operating longitudinal mode interval Δυ requirements, determine the gain fiber length L, which needs to meet the output power P>P _out and the longitudinal mode output Δυ>υ _FBG single longitudinal mode or Δυ<υ _FBG multi-longitudinal mode requirements, where , P _out is the laser output power index, υ _FBG is the bandwidth of the above-mentioned fiber grating pair.

(3) According to the laser output wavelength, write corresponding fiber grating pairs FBGP _k (k=1, 2, 3...) with different resonance wavelengths on the first single-mode fiber 1 and the second single-mode fiber 7 to form a laser Feedback cavity mirror, and finally complete the design of multi-wavelength fiber laser.

The laser cavity mirror is another basic component of the fiber laser, providing optical signal feedback for the laser. The cavity mirror of the multi-wavelength laser needs to meet the requirements of the resonance of signals of different wavelengths, and the utility model proposes a design to realize the preparation of the single-mode fiber core-layer composite cavity mirror by using the ultrafast laser processing technology.

Specifically, the manufacturing process of the fiber grating for FBGP _k is as follows: using a rotating fixture to fix the above-mentioned welded fiber sample, using a femtosecond ultrafast laser to pass through the optical system, focus the laser 9 to the first single-mode fiber 1 core 2 In the upper part, the low-reflection fiber grating is prepared, and the laser is moved to the position of the dotted line in the figure through the electric displacement platform, and it is still focused on the upper part of the second single-mode fiber 7 core 8 to prepare the high-reflection fiber grating, and the fiber grating pair 10 is completed. preparation.

角度，重复上述过程，在两侧单模光纤上分别制备高低反射率的光纤光栅，形成光纤光栅对11；依次按上述过程制备完成光纤光栅对FBGP_k。Fiber Holder Rotation

Angle, repeat the above process, respectively prepare high and low reflectivity fiber gratings on the single-mode fibers on both sides to form a fiber grating pair 11; follow the above process to prepare a fiber grating pair FBGP _k in turn.

In the preparation process, the grating period Λ _k and the refractive index modulation depth δ _k are controlled to ensure that the resonant wavelength λ _k matches the required output wavelength λ _i of the laser, that is, λ _k =λ _i , k=i;

Finally, the writing of the composite multi-wavelength fiber grating cavity mirror is completed on both sides of the single-mode fiber core, and the realization of the fiber laser design is completed.

It can be seen that the scheme of utilizing quantum dot gain fiber and fiber grating cavity mirror preparation technology to realize fiber laser output proposed by the present invention overcomes the difficulty of splicing fluoride fiber and ordinary single-mode fiber in terms of preparation methods, and it is difficult to directly It is difficult to realize the preparation of fiber grating cavity mirror on it.

At the same time, combined with the characteristics of quantum dot material fluorescence spectrum covering a wide spectral range, flexible preparation of fiber grating cavity mirrors, etc., by adjusting the size of the doped quantum dots and matching the fiber grating pair cavity mirror with the corresponding reflection wavelength, any wavelength in the visible light region can be realized. The laser output greatly broadens the working wavelength of the fiber laser.

The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited to this. Replacement should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims (6)

1. a multi-wavelength fiber laser based on multi-granularity quantum dot doping is characterized in that, comprising gain fiber and the first single-mode fiber and the second single-mode fiber connected at both ends of the gain fiber, the first single-mode fiber is The core of the mode fiber is engraved with a first composite fiber grating, the core of the second single-mode fiber is engraved with a second composite fiber grating, and the first composite fiber grating and the second composite fiber grating are combined into a fiber grating Yes, form a laser feedback cavity mirror. 2 . The multi-wavelength fiber laser based on multi-granularity quantum dot doping according to claim 1 , wherein the core of the gain fiber is doped with quantum dots. 3 . 3 . The multi-wavelength fiber laser based on multi-granularity quantum dot doping according to claim 1 , wherein the quantum dots are Q-shift processed quantum dots. 4 . 4 . The multi-wavelength fiber laser doped with multi-granularity quantum dots according to claim 1 or 3 , wherein the quantum dots have different granularities. 5 . 5 . The multi-wavelength fiber laser based on multi-granularity quantum dot doping according to claim 1 , wherein the first composite fiber grating has fiber gratings with different periods. 6 . 6 . The multi-wavelength fiber laser based on multi-granularity quantum dot doping according to claim 1 , wherein the second composite fiber grating has fiber gratings with different periods. 7 .

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