CN108270142A - A kind of optical fiber random laser device of inside of optical fibre refractive index mutation dot matrix random distribution - Google Patents

Abstract

The invention discloses an optical fiber random laser which provides random feedback by relying on the random distribution of a refractive index mutation lattice made inside an optical fiber, and belongs to the technical field of optical fiber lasers. The laser in the invention includes a pump source, a wavelength division multiplexer, a fiber reflector, a gain fiber and a fiber isolator. The present invention provides random feedback by making randomly distributed dot matrix with sudden change in refractive index in the optical fiber, and realizes laser oscillation output through the random dot matrix itself or its combination with fiber optic reflectors to form a resonant cavity structure of the laser. The optical fiber random laser has the characteristics of compact structure, high manufacturing efficiency, low process cost, reduced threshold power of the random laser, enhanced stability of the output laser of the random laser, and the like.

Description

A fiber stochastic laser with random distribution of abrupt refractive index lattices inside the fiber

technical field

The invention belongs to the field of lasers, and more specifically relates to a random fiber laser.

Background technique

As a new type of light source, random fiber laser can achieve stable and low spatial coherence continuous laser output, which makes it unique in many applications such as fiber optic sensing, high-power fiber laser output, and optical imaging. The advantages. Most of the random fiber lasers reported in the original research provide random feedback by utilizing the random Rayleigh scattering caused by the inhomogeneity defects of the refractive index distribution introduced during the fiber drawing process. Since the Rayleigh scattering coefficient in the optical fiber is very low, in order to obtain a sufficiently strong feedback, a long-distance optical fiber is often required to provide sufficient intensity of feedback. Using a longer fiber to provide random feedback complicates the system of fiber random lasers and increases the threshold of the laser. In the subsequent research on random fiber lasers, a large part of the research content focused on how to obtain random feedback with sufficient intensity in the fiber. In order to achieve strong random feedback in optical fibers, many existing research reports have proposed a number of schemes to enhance the random feedback strength of random fiber lasers by fabricating artificial random structures inside the optical fiber. The commonly used method is to provide random feedback by writing multiple randomly distributed FBGs in the fiber, or by writing FBGs with random phase shift distribution. In fiber random lasers based on these schemes, it is often necessary to write a longer-distance fiber grating, which has higher requirements on the fiber grating manufacturing system and manufacturing process, and is more time-consuming. At the same time, providing random feedback by writing fiber gratings in the fiber can only provide random feedback in one dimension along the fiber axis, which limits the random characteristics of the output random fiber laser to a certain extent.

Contents of the invention

Aiming at the above-mentioned problems existing in fiber random lasers, the present invention proposes a novel random fiber laser with a compact structure and simple manufacture to provide a random feedback mechanism by making a randomly distributed lattice structure inside the optical fiber, in order to achieve improved random characteristics and increase The purpose of improving the production efficiency, reducing the process cost, reducing the threshold power of the random laser, and enhancing the stability of the output laser of the random laser.

The technical scheme that the present invention takes is:

Disclosed is a fiber random laser with randomly distributed refractive index mutation lattices inside the fiber. The reflection mirror of the fiber laser is made of refractive index mutation lattices randomly distributed inside the fiber.

Further, the random lattice of abrupt refractive index points is set in the core region of the optical fiber, or in the core and cladding of the optical fiber.

Further, the random lattice is made in the gain fiber, or made on the non-gain fiber and then connected with the gain fiber. Furthermore, the randomly distributed lattice composed of the abrupt refractive index points distributed inside the optical fiber described in the present invention can be directly fabricated on the gain fiber as required, or can be fabricated on the passive fiber, and then passed through the gain fiber welded or otherwise connected.

Further, in the random lattice formed by the abrupt refractive index points, the feedback intensity of the lattice region can be performed by changing the size of the abrupt refractive index points, the amount of change in the refractive index, and the number of lattices.

Further, the gain fiber is a single-mode doped gain fiber, a large-mode field double-clad gain fiber or other types of gain fiber.

Furthermore, in addition to using doped fiber to generate gain under the action of pump light, there are many other types of nonlinear gain in the fiber that can also be used as the gain of random lasers, such as stimulated Raman scattering, stimulated Stimulated Brillouin scattering, etc.

Further, the cavity structure of the laser includes a linear cavity structure provided by a random lattice structure and a ring cavity provided by a random lattice structure.

Furthermore, the type of gain fiber used is selected according to actual needs, for example: different ion-doped gain fibers, different geometric dimensions, single-mode or multi-mode fiber, etc., and the type of gain fiber is selected to match with it The matching pump source and pumping method can realize fiber lasers in different wavelength ranges and different power ranges.

Furthermore, the present invention proposes a fiber random laser based on the random distribution of the refractive index mutation lattice inside the fiber, including a pump source (1), a wavelength division multiplexer (2), a fiber mirror (3), a gain fiber ( 4), a random lattice (5) composed of sudden changes in the refractive index, an optical fiber isolator (6), and a laser output port (7); where:

The pumping source (1) is connected to the pumping light input end (2-1) of the wavelength division multiplexer;

The input end (2-2) of the wavelength division multiplexer (2) is connected to the fiber mirror (3) forming one end of the fiber resonator cavity, and the output end (2-3) is connected to one end of the gain fiber (4). for pumping the gain fiber;

Described refractive index mutation lattice area (5) is connected with the input end of fiber isolator (6), and fiber isolator (6) is used for eliminating the impact of the end face reflection of the output light port of laser on laser performance; Fiber isolator ( 6) is the output end of the laser.

When working, the (2-2) port of the wavelength division multiplexer, the fiber mirror (3), the fiber mirror (3) and the random lattice structure (5) together form the resonant cavity of the fiber laser; when the pump light enters After the fiber gain fiber, the gain fiber is pumped to generate gain, and when the gain in the laser is greater than the loss, laser oscillation is formed to realize laser output, and the generated random laser is output through the output port (7) of the laser.

The randomly distributed points of sudden change in refractive index inside the optical fiber mentioned in the present invention refer to the singularity of refractive index produced in a uniform region inside the optical fiber. The positions of the sudden changes in the refractive index are randomly arranged in the optical fiber, thereby forming a randomly arranged lattice. The size of each point, the amount of change in the refractive index, and the total number of sudden changes in the refractive index in each of the randomly distributed lattices can be designed according to actual needs, thereby generating random feedback with different intensities.

Compared with existing schemes, the scheme of random fiber laser proposed in the present invention has the following advantages:

The random feedback is provided by using the random arrangement of points with sudden changes in the refractive index inside the fiber to provide random feedback. Compared with the random feedback provided by the inhomogeneity introduced directly during the fiber manufacturing process, the random distribution of the dot matrix improves the performance of the optical fiber. The strength of the internal random feedback lowers the threshold of random laser output. At the same time, the lattice structure is directly fabricated inside the fiber, which makes the fiber laser compact and easy to manufacture.

Description of drawings

Figure 1 is a schematic diagram of the structure of a fiber random laser based on the random distribution of abrupt refractive index points inside the fiber.

Fig. 2 is a schematic diagram of a randomly distributed lattice structure inside the optical fiber;

What Fig. 3 shows is the random fiber laser that provides random feedback by making the random lattice structure in the gain fiber;

What Fig. 4 represented is a kind of structural diagram of the random lattice structure in the single-mode optical fiber that the fiber core diameter is 8um, and the fiber diameter is 125um;

What Fig. 5 represented is a kind of structural diagram of the random lattice structure that is made in the multimode optical fiber with core diameter 62.5um, fiber diameter 125um;

Figure 6 shows a randomly distributed lattice structure fabricated in a double-clad doped fiber with a core diameter of 10um and a fiber diameter of 130um.

Among them: 1-first pumping source, 2-fiber wavelength division multiplexer, 3-represents fiber optic mirror, 4-gain fiber, 5-fiber region with randomly distributed lattice structure inside, 6-fiber isolator , 7-the output port of the laser, 8-the core of the fiber, 9-the cladding structure of the fiber, 10-the random lattice inside the fiber, 11-the second pump source, 12-the wavelength division multiplexer, 13- The gain fiber with dot matrix structure is made internally, 14-the output end of the laser, and 15-the output end of the laser.

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.

Implementation Case 1

After focusing the beam output by the high-power femtosecond laser, it acts on the inside of the doped gain fiber. Due to the interaction between the high-power femtosecond laser and the optical fiber, the refractive index of the spot action area changes, thus obtaining a single abrupt change point of the refractive index. Then move the beam of the femtosecond laser to make other abrupt refraction points. The distances between the individual refractive index mutation points are randomly arranged. Feedback is provided by the reflection and scattering of light as it travels through these lattice structures due to the difference between the refractive index and that of the fiber material. These random lattice structures combined with the feedback provided by the fiber mirror 3 can form a resonant cavity structure.

The pump light output from the pump source connected to the port of the wavelength division multiplexer 1 enters the gain fiber 4 through the wavelength division multiplexer 2 to pump the gain fiber. The gain fiber used may be a single-mode erbium-doped fiber, or a doped multi-mode fiber or other fiber that can provide gain. The type of pump source is selected according to the type of gain fiber used.

When the gain fiber 4 absorbs the pump light, spontaneous emission light will be generated. The spontaneous emission light will be reflected back and forth between the fiber mirror 3 and the manufactured random lattice structure region 5 , and will be continuously amplified when passing through the gain fiber 4 . When the gain is greater than the loss in the laser resonator, laser lasing can be generated. The generated random laser can be output through port 7.

Implementation Case 2

In the same manner as in Example 1, randomly distributed dot matrixes are made in the gain fiber, as shown by 13 in FIG. 6 . Then the dot matrix area that is made is connected to the 12-3 port of the wavelength division multiplexer 12 by welding, and the pump light sent by the pump source 11 enters the point through the 12-1 port of the wavelength division multiplexer 12. The array area pumps the lattice area. Spontaneous emission occurs when the gain fiber is subjected to pump light. Since the dot matrix structures are made in the gain fiber, these dot matrix structures can generate feedback to the generated spontaneous emission light, and under the action of the feedback, when the gain is greater than the loss, laser lasing can be generated. The generated laser light can be output through port 14 or 15 in FIG. 6 .

The present invention adopts random dot matrix to provide random feedback to realize the output of random laser. The random laser thus obtained has the advantage of compact structure, and the output laser also has the advantages of narrow line width and low spatial coherence. The above-mentioned embodiments are only preferred solutions in the solutions of the present invention, and other random fiber laser solutions that use random lattice structures to provide random feedback mechanisms all fall within the protection scope of the present invention. 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 (9)

1. A kind of 1. optical fiber random laser device of inside of optical fibre refractive index mutation dot matrix random distribution, which is characterized in that optical-fiber laser The speculum of device is the refractive index mutation dot matrix for being produced on inside of optical fibre random distribution.
2. 2. optical fiber random laser device as described in claim 1, which is characterized in that the random dot matrix of refractive index catastrophe point is located at The core region of optical fiber or the fibre core and covering for being located at optical fiber.
3. 3. optical fiber random laser device as described in claim 1, which is characterized in that the random dot matrix of refractive index catastrophe point is produced on It is connected in gain fibre or after being produced on non-gain fibre with gain fibre.
4. 4. optical fiber random laser device as described in claim 1, which is characterized in that the random dot matrix that the refractive index catastrophe point is formed In, it can be to dot matrix region by changing the size of refractive index catastrophe point and the quantity of the knots modification of refractive index and dot matrix Feedback intensity carry out.
5. 5. optical fiber random laser device as described in claim 1, which is characterized in that the gain fibre is that the doping of single mode increases Beneficial optical fiber, the double clad gain fibre of large mode field or other types of gain fibre.
6. 6. optical fiber random laser device as described in claim 1, which is characterized in that the laser provides increasing with doped fiber Benefit provides gain with the stimulated raman scattering or stimulated Brillouin scattering of optical fiber.
7. 7. optical fiber random laser device as described in claim 1, which is characterized in that the cavity configuration of the laser includes random Lattice structure provides the linear cavity configuration of feedback and the ring cavity structure of feedback is provided comprising random lattice structure.
8. 8. optical fiber random laser device as described in claim 1, which is characterized in that by the increasing for selecting different Doped ions Beneficial optical fiber, the optical fiber of different geometrical size, single mode or multimode fibre etc., while selected therewith according to the type of gain fibre Matched pumping source and pump mode, realizing has different power, the optical fiber laser of different output wavelengths.
9. 9. it is a kind of based on inside of optical fibre refractive index mutation dot matrix random distribution optical fiber random laser device, include pumping source (1), Wavelength division multiplexer (2), fiber reflector (3), gain fibre (4), refractive index catastrophe point form random dot matrix (5), optical fiber every From device (6), laser output (7)；Wherein：

   The pumping source (1) is connected with the pumping light input end (2-1) of wavelength division multiplexer；

   Wavelength division multiplexer (2) input terminal (2-2) is connected with forming the fiber reflector (3) of fiber resonance cavity one end, exports End (2-3) is connected with one end of gain fibre (4), for being pumped to gain fibre；Another termination of the gain fibre Refractive index is mutated dot matrix area domain (5)；

   The other end of refractive index mutation dot matrix area domain (5) is connected with the input terminal of fibre optic isolater (6), fibre optic isolater (6) for eliminating influence of the end face reflection to laser performance of the output optical port of laser；The output of fibre optic isolater (6) Hold the output terminal for laser.

   During work, input terminal (2-2), fiber reflector (3), fiber reflector (3) and the random lattice structure of wavelength division multiplexer (5) resonator of optical fiber laser is formed together；After pump light enters fiber gain optical fiber, pumping production is carried out to gain fibre Frequency selection is realized in raw gain, refractive index mutation dot matrix area domain (5)；Laser is formed when the gain in laser is more than loss to shake It swings and realizes laser output, the Random Laser of generation is exported by the output terminal (7) of laser.