CN105356212B - A kind of optical fiber laser including inside of optical fibre lattice structure optical fibre device - Google Patents

Abstract

The invention proposes a fiber laser using a fiber device with a lattice structure inside the fiber. The invention forms an optical fiber device with a built-in lattice structure through the lattice structure fabricated in the optical fiber, and realizes the selection of the output wavelength of the laser. By controlling the arrangement and distribution of the dot matrix and the size of the dot matrix, the wavelength selection characteristics of the dot matrix structure are adjusted. Compared with fiber gratings, optical fiber devices based on internal lattice structures can be more flexible in the design of wavelength selection methods. At the same time, the lattice structure is fabricated inside the fiber, making the structure of the fiber laser compact. After properly designing the distribution of the lattice structure, fiber lasers with some special properties can be obtained, such as multi-wavelength, single longitudinal mode, and single polarization.

Description

A fiber laser including a fiber optic device with a lattice structure inside the fiber

technical field

The invention belongs to the field of fiber lasers, and more specifically, the invention relates to a fiber laser in which a fiber device with a lattice structure is used in a laser resonator cavity.

Background technique

Due to its excellent beam quality, stable structure and easy to achieve high power output, fiber lasers have been more and more researched and applied. According to the composition of the laser, the structure of the fiber laser also includes three basic components of the laser: resonant cavity, gain medium and pump source.

In fiber lasers, commonly used gain media have a wide gain spectrum. In order to achieve a specific wavelength of laser output, it is often necessary to add wavelength-selective devices in the resonator, including optical filters, interferometers, and optical mirrors. and fiber grating etc.

Fiber gratings have been widely used in fiber lasers due to their good wavelength selection characteristics and easy fusion with gain fibers. In fiber lasers that use fiber gratings to form resonators, the wavelength selectivity and semi-transparent and semi-reflective properties of fiber gratings are mainly used. The resonant wavelength of the fiber grating determines the output wavelength of the fiber laser, and tuning the resonant wavelength of the fiber grating can realize the adjustment of the output wavelength of the laser. The introduction of fiber lasers with fiber gratings reduces the need for optomechanical devices, making fiber lasers more compact and well tunable. In common fiber lasers that use fiber gratings to form resonant cavities, some fiber gratings are fabricated on gain fibers, and some are fabricated on non-gain fibers, and then connected with gain fibers in other ways to form resonant cavities.

In the existing manufacturing technology of fiber gratings, the phase mask method and the double-beam interference method are common methods. However, in these preparation methods, the period of the fiber grating is determined by the period of the phase mask or the wavelength of the interfering light, and it is not easy to achieve arbitrary design, so the output wavelength tuning of the fiber laser is limited.

Contents of the invention

In view of the fact that the period of the fiber grating in the existing fiber laser technology is determined by the period of the phase mask or the wavelength of the interfering light, it is not easy to achieve any design problem. The present invention proposes a fiber optic device that uses a lattice structure inside the fiber laser.

The optical fiber device with a lattice structure inside the optical fiber of the present invention refers to a lattice formed by points with a refractive index different from that of the optical fiber inside the optical fiber. The refractive index of these points is different from that of the background material of the optical fiber. Periodically arranged, so that the refractive index inside the fiber changes according to the law of design, and the reflection and transmittance of light of different wavelengths are different according to the law of refractive index change. In this way, the wavelength selection characteristics of the optical fiber device are changed, thereby realizing The selection of the wavelength of light leads to the designed optical fiber device. By designing the structure and distribution of the internal lattice of the optical fiber, the wavelength selection characteristics of the device can be flexibly designed.

Based on the optical fiber device with a lattice structure inside the optical fiber, the technical solution of the fiber laser proposed by the present invention is:

A fiber laser, comprising a pump source, a gain fiber and a fiber optic device, is characterized in that the fiber optic device has a built-in lattice structure for realizing wavelength selection. points are arranged.

Further, in the fiber laser, the fiber device is obtained by changing the refractive index of the internal points of the fiber material to obtain a refractive index singularity, and the refractive index singularity is arranged periodically or quasi-periodically, and the built-in point formed together with the background fiber material Array-structured fiber optic devices.

Further, in the fiber laser, the fiber device material includes but not limited to silica fiber and polymer fiber.

In the present invention, the lattice structure inside the optical fiber can be directly fabricated in the gain optical fiber, or can be fabricated on the ordinary non-gain optical fiber, and then welded together with the gain optical fiber. Its specific plan is:

A fiber laser, comprising a pump source and a gain fiber, is characterized in that the gain fiber or the common non-gain fiber connected to the gain fiber has a built-in lattice structure, and the gain fiber has gain and frequency selection simultaneously Function; the lattice structure is formed by dots with different refractive index inside the optical fiber than that of the optical fiber material, and is used to realize wavelength selection.

Further, in the fiber laser, the diameter of each point in the lattice structure and/or the distance between points is set as required, and/or the points are spheres or other volumetric structures, and \ Or missing multiple adjacent local lattice planes on any plane, resulting in optical fiber devices with plane defects.

Further, in the fiber laser, one point of the lattice structure can be missing to form an optical fiber device with lattice defects, and\or a plurality of adjacent partial lattice lines can be missing to form an optical fiber device with line defects.

Further, in the fiber laser, the lattice structure can lack a plurality of adjacent local lattice planes on any plane, so that an optical fiber device with plane defects can be obtained.

Further, in the fiber laser, the points in the lattice structure can be arranged arbitrarily into lattice lines or lattice planes; and\or it has one or more lattice lines or lattice planes, and the lattice lines, points The distance between the fronts can be adjusted.

Further, in the fiber laser, the types of the gain fiber and the pumping source are selected according to actual needs.

Further, in the fiber laser, the point is formed by focusing the femtosecond laser beam and then using the femtosecond laser beam to interact with the fiber material to form a refractive index singularity with a different refractive index than the fiber material.

The invention adopts a specific distributed lattice structure in the fiber laser to realize the function of wavelength selection. Compared with other wavelength selective devices, the lattice structure can be directly fabricated inside the optical fiber, which has the advantage of compact structure. At the same time, when designing the wavelength selection characteristic, the distribution of the lattice structure can be designed arbitrarily, which makes the design of the wavelength selection characteristic of the lattice structure more flexible. Therefore, the laser output characteristics of the fiber laser can be more flexibly designed and tuned.

Description of drawings

Fig. 1 is a structural schematic diagram of a ring cavity structure fiber laser including a lattice structure inside an optical fiber;

Fig. 2 is a structural schematic diagram of a linear cavity structure fiber laser including a lattice structure inside an optical fiber;

Fig. 3 is a schematic diagram of a distributed feedback fiber laser including a lattice structure fiber device inside the fiber;

Throughout the drawings, the same reference numerals are used to designate the same elements or structures, wherein:

1-pump source, 2-wavelength division multiplexer, 3-gain fiber, 4-fiber circulator, 5-fiber device with lattice structure inside 1, 6-fiber coupler, 7-ring cavity laser output , 8-connecting optical fiber, 9-isolator, 10-fiber device with lattice structure inside 2, 11-output end of linear cavity laser, 12-fiber device with lattice structure inside 3, 13-fabricated in gain fiber On the dot matrix structure with a phase shift structure, 14 distributed feedback fiber laser output ports.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not constitute a conflict with each other.

The fiber laser involved in the present invention will be further described and introduced in conjunction with the accompanying drawings, but the content included in the present invention is not limited thereto.

Fig. 1 shows a schematic structural diagram of a fiber laser with a ring cavity structure including a lattice structure inside an optical fiber. A single point in the lattice can be obtained by focusing the femtosecond laser pulse beam with high peak power and interacting with the fiber material to change the refractive index of the fiber material. These points are replicated inside the fiber to obtain a lattice structure. Among them, 1 represents the pump source, 2 represents the wavelength division multiplexer, 3 represents the gain fiber, 4 represents the circulator, 5 represents the optical fiber device with a lattice structure inside, and 6 represents the Fiber coupler, 7 represents the output end of the laser, and 8 represents the non-gain fiber.

Figure 2 shows a schematic diagram of the structure of a linear cavity fiber laser including a fiber device with a lattice structure inside the fiber, where 1 represents the pump source, 9 represents the isolator, and 10 and 12 represent the internal lattice structure. In the optical fiber device, 3 represents the gain fiber, and 11 represents the output port of the laser.

Fig. 3 shows a schematic diagram of a distributed feedback fiber laser including a fiber optic device with a lattice structure inside the fiber. Among them, 1 represents the pump source, 2 represents the wavelength division multiplexer, 8 represents the optical fiber, 13 represents the lattice structure with a phase shift structure made on the gain fiber, and 14 represents the laser output terminal.

Implementation example 1

Embodiment 1 of the present invention is shown in FIG. 1 . First, a lattice structure that meets the requirements is fabricated on the optical fiber, and the pump light output from the pump source 1 shown in Figure 1 enters the ring cavity of the fiber laser through the wavelength division multiplexer indicated by 2 in Figure 1 to realize the The pumping by the gain fiber 3, the fiber circulator represented by 4 in Fig. 1 ensures that the light in the fiber laser resonator is transmitted along the same direction. The optical fiber device 5 with the internal lattice structure of the optical fiber is connected to the 2 ports of the optical fiber circulator represented by 4 in the figure to play the role of wavelength selection. The lattice structure 5 only achieves strong reflection for a specific wavelength, thereby determining the output wavelength of the fiber laser. The laser is used as an output port of the laser through a port of the fiber coupler represented by 6 in FIG. 1 , which is represented by 7 in FIG. 1 .

Implementation example 2

Embodiment 2 of the present invention is shown in FIG. 2 . Firstly, an optical fiber device containing a lattice structure is fabricated on the optical fiber, as shown by 10 and 12 in FIG. 2 . Then connect it to the gain fiber. The pump light output from the pump source shown in 1 in FIG. 2 passes through the fiber isolator and enters the fiber device 10 containing the lattice structure inside. The pump light can pass through 10 to pump the gain fiber 3 . Due to the selective reflection of specific wavelengths of devices 10 and 12, wherein 10 and 12 reflect the same wavelength, the resonant cavity of the fiber laser is formed. The generated laser is output through the port shown in Figure 11.

Implementation example 3

Embodiment 3 of the present invention is shown in FIG. 3 . First, a lattice structure with a phase shift distribution is produced on the gain fiber. The lattice structure of the phase shift distribution means that in this lattice structure, the distance between certain two lattice planes is different from that between other lattice planes. If the spacing is not equal, a phase jump occurs. As shown in Figure 13.

As shown in Figure 3. The pump light output by the pump source 1 shown in FIG. 3 enters the lattice structure region 13 fabricated on the gain fiber through the optical wavelength division multiplexer 2 shown in FIG. 3 and pumps it. Since the lattice structure is fabricated on the gain fiber and has a phase shift structure, it can form a resonant cavity and realize laser output. The generated laser is output through 14 shown in the figure.

The main advantage of the design of the present invention is that the laser uses an optical fiber device with a lattice structure inside to form a part of the laser resonator, and the fiber device with a lattice structure inside has a selective characteristic for the output wavelength of the laser. By making a periodically arranged lattice structure in the optical fiber, the refractive index inside the optical fiber changes periodically, thereby achieving strong reflection of light of a specific wavelength and realizing the wavelength selection function. By controlling the period of the lattice arrangement and the size of the lattice, the wavelength selection characteristic of the lattice structure can be tuned. Compared with fiber gratings, optical fiber devices based on internal lattice structures can be more flexible in the design of wavelength selection methods. At the same time, the lattice structure is fabricated inside the fiber, making the structure of the fiber laser compact. After properly designing the distribution of the lattice structure, fiber lasers with other special properties can be obtained, such as multi-wavelength, single longitudinal mode, and single polarization.

It is easy for those skilled in the art to understand that the above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, All should be included within the protection scope of the present invention.

Claims (13)

1. a kind of optical fiber laser, including pumping source, gain fibre and optical fibre device, which is characterized in that in the optical fibre device Lattice structure is set, for realizing wavelength selection, lattice structure is to be different from the point row of fiber optic materials by inside of optical fibre refractive index It arranges；

Specifically, the optical fibre device is to obtain refractive index singular point by changing the refractive index of point inside fiber optic materials, is reflected The optical fibre device of built-in lattice structure that rate singular point is formed together according to period or arrangement paracycle and background fiber optic materials.

2. optical fiber laser according to claim 1, which is characterized in that the optical fibre device material includes but not limited to two Silica optical fibre, polymer optical fiber.

3. optical fiber laser according to claim 1, including pumping source and gain fibre, which is characterized in that the gain There is built-in lattice structure, the gain fibre to have simultaneously in optical fiber or the common non-gain fibre being connect with the gain fibre There are gain and frequency-selecting function；The lattice structure is that obtain refractive index strange by changing the refractive index of point inside fiber optic materials Point, the singular point that fiber optic materials are different from by inside of optical fibre refractive index are arranged according to period or paracycle, for real Existing wavelength selection.

4. optical fiber laser according to claim 1 or 3, which is characterized in that in the lattice structure diameter of each point and Or distance between points is set as needed, and or the point be sphere.

5. optical fiber laser according to claim 1 or 3, which is characterized in that the lattice structure can lack one of them Point constitutes an optical fibre device with lattice defect, and or the multiple adjacent partial dot fronts of missing, constituting has line defect Optical fibre device.

6. the optical fiber laser as described in claim 1 or 3, which is characterized in that the lattice structure can lack on arbitrary plane Multiple adjacent local lattice plane, obtain the optical fibre device with planar defect.

7. the optical fiber laser as described in claim 1 or 3, which is characterized in that the point in the lattice structure can be arranged arbitrarily Arrange into front or lattice plane；He or its tool there are one front or lattice plane is put above, and described between front, lattice plane Distance can adjust.

8. the type of optical fiber laser according to claim 1 or 3, gain fibre and pumping source according to the actual needs into Row selection.

9. the optical fiber laser as described in any in claim 1-3, which is characterized in that the point is by by femtosecond laser It after device light beam focuses, is interacted using femtosecond laser beam and fiber optic materials, is different from fiber optic materials to form refractive index Refractive index singular point.

10. the optical fiber laser as described in any in claim 4, which is characterized in that the point is by by femtosecond laser It after device light beam focuses, is interacted using femtosecond laser beam and fiber optic materials, is different from fiber optic materials to form refractive index Refractive index singular point.

11. the optical fiber laser as described in any in claim 5, which is characterized in that the point is by by femtosecond laser It after device light beam focuses, is interacted using femtosecond laser beam and fiber optic materials, is different from fiber optic materials to form refractive index Refractive index singular point.

12. the optical fiber laser as described in any in claim 6, which is characterized in that the point is by by femtosecond laser It after device light beam focuses, is interacted using femtosecond laser beam and fiber optic materials, is different from fiber optic materials to form refractive index Refractive index singular point.

13. the optical fiber laser as described in any in claim 7, which is characterized in that the point is by by femtosecond laser It after device light beam focuses, is interacted using femtosecond laser beam and fiber optic materials, is different from fiber optic materials to form refractive index Refractive index singular point.