CN108565667A - A kind of feedback-enhanced erbium-doped nonlinear fiber grating accidental laser - Google Patents

Abstract

The invention discloses a feedback-enhanced erbium-doped fiber grating random laser, which includes a pump laser, a wavelength division multiplexer, a high-reflection fiber grating, and a weak-reflection erbium-doped fiber grating string. The fiber laser of the invention has the advantages of low threshold value, high conversion efficiency, etc., and belongs to the technical field of lasers. The invention provides weak distribution feedback by writing weak reflection fiber grating series on the erbium-doped optical fiber. The invention utilizes two high-reflection optical fiber gratings to increase feedback in the cavity and improve laser conversion efficiency and output power. The fiber laser of the present invention has great application potential in the fields of optical communication and the like.

Description

A feedback-enhanced erbium-doped fiber grating random laser

technical field

The invention belongs to the technical field of lasers, in particular to a feedback-enhanced erbium-doped fiber grating random laser.

Background technique

The random fiber laser is a new type of cavity-free structure laser based on the scattered light in the disordered medium that is continuously amplified during transmission. It has the advantages of good stability, small and simple structure (no cavity mirror required), and spatial incoherence. These characteristics make it have broad development prospects in many applications, such as long-distance optical fiber communication, photonic crystal light source, biomedical imaging, remote sensing, etc.

In 2010, the experiment confirmed that the random distributed feedback fiber laser fully utilizes the weak Rayleigh scattered light in the fiber as the feedback mechanism. Although the backscattering coefficient is small, it can be accumulated and continuously amplified in the ultra-long-distance fiber , when the gain is greater than the loss, a random laser output will be formed. Therefore, it opens up a new direction of fiber laser research, and drives continuous development and application research. Its special optical mechanism makes it have great advantages in many fields, shows strong competitiveness, and has become the mainstream of current research and development. However, due to the weak Rayleigh scattering caused in the fiber, this kind of fiber laser has the disadvantages of high threshold, low output power and low power conversion efficiency.

A fiber grating is an optical fiber device that forms a permanent periodic change in the refractive index in the fiber core by a certain method. Due to its selective reflection characteristics, it can be used in fiber lasers. Such lasers have the advantages of low cost, easy coupling with optical fibers, high stability, and easy wavelength tuning. With the deepening of scientific research, some researchers have proposed to write fiber gratings on special fibers and use them in fiber lasers, which can not only shorten the cavity length of fiber lasers, but also have the advantages of lowering the threshold.

On the basis of the above, the present invention writes a weak reflection fiber grating string on an erbium-doped fiber and combines it with two high reflection fiber gratings to propose a random fiber laser with a new structure, high conversion efficiency and stable output.

Contents of the invention

Aiming at the deficiencies of the prior art, the present invention proposes a feedback-enhanced erbium-doped fiber grating random laser, which provides weakly distributed feedback by writing weakly reflective fiber grating strings on the erbium-doped fiber, and uses two high-reflective fiber gratings to increase the intracavity Feedback to improve laser conversion efficiency and output power.

The technical solution adopted by the present invention to solve the technical problems is as follows:

A feedback-enhanced erbium-doped fiber grating random laser is characterized in that it consists of a pump laser 1, a wavelength division multiplexer 2, a first high-reflection fiber grating 3, a weakly-reflection erbium-doped fiber grating string 4, and a second high-reflection optical fiber Composed of grating 5; the pump laser 1 is connected to the input end of the wavelength division multiplexer 2, one end of the output of the wavelength division multiplexer 2 is connected to the first high-reflection fiber grating 3, and the other end of the output of the wavelength division multiplexer 2 is sequentially connected to Weakly reflective erbium-doped fiber grating series 4 and the second high reflective fiber grating 5, the other end of the second high reflective fiber grating 5 outputs laser light; wherein, the first high reflective fiber grating 3 remains on the same side as the pump laser 1, or Keep the same side with the weak reflection erbium-doped fiber grating string 4 and the second high reflection fiber grating 5 .

A kind of feedback-enhanced erbium-doped fiber grating random laser according to claim 1, characterized in that, each fiber grating spacing in the weak reflection erbium-doped fiber grating string 4 is randomly distributed within 1-100mm; The central wavelength and bandwidth of the first high reflection fiber grating 3, the second high reflection fiber grating 5 and the weak reflection erbium-doped fiber grating string 4 are consistent.

Working principle of the present invention is:

Turn on the pump laser 1, and the pump light is coupled into the linear cavity through the wavelength division multiplexer 2. In the weak reflection erbium-doped fiber grating string 4, after Er3+ absorbs the energy of the pump light, it transitions from the ground state to a high-level state, and Transition to the metastable energy level in a non-radiative way, Er3+ continuously absorbs the pump light energy and accumulates in the upper energy level, and finally realizes the inversion of the number of particles between the energy levels, thereby generating stimulated radiation, and performing optical gain amplification on the C-band light. At the same time, due to the Anderson localization phenomenon in the weakly reflective Erbium-doped fiber grating string 4, the light is weakly reflected multiple times in the weakly reflective Erbium-doped fiber grating string 4, resulting in a closed ring cavity similar to a resonant cavity. The reflected string is continuously amplified by the gain. Wherein, the backward and forward light respectively enters the first high-reflection fiber grating 3 and the second high-reflection fiber grating 5 after exiting from the weakly reflective erbium-doped fiber grating string 4, and is respectively reflected into the weakly reflective erbium-doped fiber grating string In 4, the gain is amplified again. Thus, lasing occurs when the gain in the cavity is greater than the loss.

The present invention has the following innovative advantages:

The fiber grating series used in the invention is written on the erbium-doped fiber and provides weak distribution feedback. Compared with the traditional distribution feedback provided by Rayleigh scattering, the use length of the fiber is greatly reduced and the threshold value of the laser is lowered. The invention adopts two high-reflection fiber gratings, which can increase the feedback in the cavity and greatly improve the conversion efficiency and output power of the laser.

Description of drawings

Fig. 1 is a schematic structural diagram of a feedback-enhanced erbium-doped fiber grating random laser.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments, but is not limited thereto.

A kind of feedback-enhanced erbium-doped fiber grating random laser, its structural schematic diagram is shown in Figure 1, comprises pumping laser 1, wavelength division multiplexer 2, first high reflection fiber grating 3, weak reflection erbium-doped fiber grating string 4 , the second high reflection fiber grating 5; the pump laser 1 is connected to the input end of the wavelength division multiplexer 2, and the output end of the wavelength division multiplexer 2 is connected to the first high reflection fiber grating 3, and the wavelength division multiplexer 2 The other end of the output is sequentially connected to the weak reflection erbium-doped fiber grating series 4 and the second high reflection fiber grating 5, and the other end of the second high reflection fiber grating 5 outputs laser light; wherein, the first high reflection fiber grating 3 remains connected to the pump laser 1 The same side, or the same side as the weak reflection erbium-doped fiber grating series 4 and the second high reflection fiber grating 5 . A spectrometer and an optical power meter are respectively connected at the laser output end to detect the output characteristics of the laser spectrum and power.

The weak reflection erbium-doped fiber grating series 4 of the present invention is completed by continuously writing the weak reflection fiber gratings on the erbium-doped optical fiber under the laser, and the distance between the weak reflection fiber gratings is randomly distributed within 1-100mm and the center wavelength is the same; the first A high-reflection fiber grating 3 and a second high-reflection fiber grating 5 are written on the single-mode fiber by using a laser and have the same central wavelength.

Claims (2)

1. a kind of feedback-enhanced erbium-doped nonlinear fiber grating accidental laser, it is characterised in that by pump laser 1, wavelength division multiplexer 2, the first high reflection fiber grating 3, weak reflection erbium-doped nonlinear fiber grating string 4, the second high reflection fiber grating 5 composition；Pumping laser Device 1 is connected with the input terminal of wavelength division multiplexer 2, and output one end of wavelength division multiplexer 2 connects the first high reflection fiber grating 3, wave The output other end of division multiplexer 2 is sequentially connected weak reflection erbium-doped nonlinear fiber grating string 4 and the second high reflection fiber grating 5, and second The other end of high reflection fiber grating 5 exports laser；Wherein, the first high reflection fiber grating 3 keeps same with pump laser 1 Side or itself and weak reflection erbium-doped nonlinear fiber grating string 4, the second high reflection fiber grating 5 keep homonymy.

2. a kind of feedback-enhanced erbium-doped nonlinear fiber grating accidental laser according to claim 1, which is characterized in that described Each fiber grating spacing random distribution in 1-100mm in weak reflection erbium-doped nonlinear fiber grating string 4；The first high reflection optical fiber Grating 3, the second high reflection fiber grating 5 are consistent with the centre wavelength of weak reflection erbium-doped nonlinear fiber grating string 4 and bandwidth.