CN113285335B - Mixed gain semi-open cavity structure 2um optical fiber random laser - Google Patents

Abstract

The invention discloses a 2um fiber random laser with a mixed gain half-open cavity structure, comprising a pumping light source, a wavelength division multiplexer, a phosphorus-doped fiber, and a thulium-doped fiber, and a 1566 nm laser simultaneously pumps a passive phosphorus-doped fiber and an active thulium-doped fiber Fiber, taking full advantage of the fact that the Raman gain peak of phosphorus pentoxide (1320cm-1) of phosphorus-doped fiber coincides with the gain peak of thulium-doped fiber to obtain stimulated Raman scattering gain and active fiber gain in the 2-micron waveband. Rayleigh scattering semi-open cavity structure generates random fiber laser in 2-micron waveband, which solves the large loss of 2-micron waveband optical signal in long-distance passive optical fiber transmission, and obtains optical fiber random laser in semi-open cavity structure. The low noise characteristics provide a new idea for the optimization and performance improvement of fiber lasers in the mid-infrared band, and expand the emission wavelength of random fiber lasers to the mid-infrared band, which has important application value.

Description

A 2um fiber random laser with hybrid gain half-open cavity structure

technical field

The invention relates to the technical field of fiber lasers, in particular to a 2um fiber random laser with a hybrid gain half-open cavity structure.

Background technique

Mid-infrared fiber lasers have important application requirements in the fields of medicine, national defense, communication and industry, and have received extensive research and attention. In recent years, fiber random lasers based on open-cavity structures are expected to be widely used in imaging, communications and other fields due to their simple structure, easy realization of high-power/high-efficiency lasing, and extremely low noise characteristics. The generation of fiber random lasers relies on the distributed Rayleigh scattering feedback accumulated by long-distance fibers, and the great transmission loss of mid-infrared fibers in silicon-based fibers hinders the realization of this type of laser in the mid-infrared band.

According to the above, the present patent provides a semi-open structure using a mixed gain, making full use of the large Raman frequency shift of the phosphorus-doped fiber and the common absorption and emission bands of the thulium-doped fiber, and using a 1566 nm pump laser to stimulate the phosphorus-doped fiber. Raman scattering and active gain in thulium-doped fiber, common gain in 2um band, solving the large loss of 2-micron band optical signal in long-distance passive fiber transmission, and obtaining fiber random laser in semi-open cavity structure, the The laser has extremely low noise characteristics, which provides a new idea for the optimization and performance improvement of fiber lasers in the mid-infrared band, and expands the emission wavelength of random fiber lasers to the mid-infrared band, which has important application value.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide a novel distributed feedback random fiber laser structure with a working wavelength around 2 microns, so as to improve the light-to-optical conversion efficiency and output power.

In order to solve the above-mentioned technical problems, the technical scheme of the present invention is: a hybrid gain half-open cavity structure 2um fiber random laser, and the random fiber laser with the operating wavelength around 2 microns includes:

Pump light source: used to generate pump light; it consists of 1566nm HR FBG, 976nm LD, beam combiner, erbium-doped fiber, and 1566nm LR FBG;

1566nm HR FBG, which reflects the 1566nm light back into the laser cavity to prevent the generated 1566nm light from overflowing into the laser cavity and reduce the laser output;

976nmLD, used to generate 976nm light;

A beam combiner that couples the reflected light of the 1566nm HR FBG and the light generated by the 976nm LD to the fiber;

Erbium-doped fiber absorbs 976nm laser pumped by 976nm LD pump light source, performs active gain amplification, and generates 1566nm laser light;

1566nm LR FBG, the residual 976nm pump light after passing through the erbium-doped fiber passes through the high-return erbium-doped fiber, and continues to participate in active gain amplification, and transmits the 1566nm light generated by the active gain amplification after passing through the erbium-doped fiber. Then, let the 1566nm laser output from the laser;

A wavelength division multiplexer, the 1560 end of the wavelength division multiplexer is connected to the 1566nm LR FBG;

Phosphorus-doped fiber and thulium-doped fiber connected to the com end of the wavelength division multiplexer, the wavelength division multiplexer couples the pump light to the active fiber, and the active fiber couples the pump light source The generated laser is subjected to gain amplification; the 1974nm FBG written at the tail of the active fiber reflects the 1974nm light to the 1950 end of the wavelength division multiplexer for output;

Further, the wavelength of the pump light is 1566 nm.

Further, the optical fiber port is chamfered to prevent section feedback.

Further, the length of the phosphorus-doped fiber is 500m, and the length of the thulium-doped fiber is 3m.

Further, the reflectivity of the HR FBG is greater than 90%, and the reflectivity of the LR FBG is less than 10%. .

Compared with the prior art, the hybrid gain semi-open cavity structure 2um fiber random laser has the structural advantage of using 1566nm pumping, which can not only use the first-order stimulated Raman scattering gain of the phosphorus-doped fiber, but also use the The active gain of thulium-doped fiber, one pump simultaneously gains two nonlinear processes, and the generated wavelengths are overlapping, which can effectively improve the light conversion efficiency and output power.

Description of drawings

Figure 1 is a schematic structural diagram of a 2um fiber random laser with a hybrid gain half-open cavity structure.

Pump light source 1, wavelength division multiplexer 2, phosphorus-doped fiber 3, thulium-doped fiber 4.

The following specific embodiments will be further described with reference to the above drawings.

Detailed ways

In the following, various specific details are set forth in order to provide a thorough understanding of the concepts underlying the described embodiments, however, it will be apparent to those skilled in the art that the described embodiments may be described without these specific details In some or all cases, well-known processing steps are not described in detail.

In the description of the invention, it is to be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer" The orientation or positional relationship indicated by "" etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, a specific orientation, and a specific orientation. The orientation configuration and operation are therefore not to be construed as limitations on the invention.

As shown in Figure 1, a hybrid gain half-open cavity structure 2um fiber random laser, the distributed feedback random fiber laser includes a pump light source 1, a wavelength division multiplexer 2, a phosphorus-doped fiber 3, and a thulium-doped fiber 4.

In one embodiment, the pump light source 1 generates pump light that is 1566 nm.

In one embodiment, the wavelength division multiplexer (WDM) 2 includes a 1560 end, a 1950 end, and a com end. The 1560 end and the 1950 end are located on the same side of the wavelength division multiplexer 2, and the com end is located on the other side of the wavelength division multiplexer 2. The 1560 end of the wavelength division multiplexer 2 is connected to the pump light source 1 .

In one embodiment, the phosphorus-doped fiber 3 may be a single-mode fiber with different phosphorus ion doping concentrations, and the length of the phosphorus-doped fiber is 500 meters. The phosphorus-doped fiber 3 is connected to the com end of the wavelength division multiplexer 2 , and the wavelength division multiplexer 2 couples the pump light generated by the pump light source 1 to the phosphorus-doped fiber 3 . The phosphorous-doped fiber 3 amplifies the Raman gain generated by the stimulated Raman scattering effect on the pump light generated by the pump light source 1 .

In one embodiment, the length of the thulium-doped fiber 4 is 3 meters. The residual 1566 nm pump light after passing through the 500-meter phosphorous-doped fiber 3 passes through the thulium-doped fiber 4. Due to the active gain amplification of thulium ions, a 1974 nm stimulated emission laser will be generated.

In one embodiment, a high-reflection fiber Bragg grating with a reflectivity greater than 90% is written at the tail end of the thulium-doped fiber 4, and the high-reflection fiber Bragg grating pair passes through the 500-meter single-mode phosphorus-doped fiber 3 due to Rayleigh scattering feedback And the 1974nm distributed feedback random laser generated by stimulated Raman gain amplification and the 1974nm stimulated radiation laser that is amplified by the gain amplification in the 3m thulium-doped fiber 4 due to the population inversion are almost completely reflected, and the reflection enters the thulium-doped fiber. Fiber 4 and phosphorus-doped fiber 3 further amplify the required random laser. The high-reflection fiber Bragg grating will generate multiple reflections due to the backward Rayleigh scattering generated by the single-mode phosphorus-doped fiber 3, which greatly improves the gain.

Specifically, the 1566 nm pump light emitted by the pump light source 1 passes through the wavelength division multiplexer 2 and the single-mode phosphorus-doped fiber 3, and the 500-meter single-mode phosphorus-doped fiber is due to the uneven refractive index of the fiber core. The Rayleigh scattering caused by the distribution provides random distributed feedback. The weak Rayleigh scattering accumulates continuously over a distance of 500 meters, which greatly improves the random distributed feedback. At the same time, the single-mode phosphorus-doped fiber provides stimulated Raman gain amplification for pump light. For gain amplification, when the power of the pump light source exceeds the lasing threshold and the gain obtained in the fiber is greater than the loss, a stable distributed feedback random laser with a working wavelength of 1974 nm can be obtained. The residual 1566 nm pump light after passing through the 500-meter phosphorous-doped fiber passes through the thulium-doped fiber 4. Due to the active gain amplification of the thulium ions, a 1974 nm stimulated radiation laser will be generated, so that the pump light source 1 can be used to the greatest extent. The pump light provides enough gain to form the output of a 1974nm distributed feedback random laser. A 1974 nm distributed feedback random laser formed by phosphorus-doped fiber 3 and a 1974 nm stimulated radiation laser formed by thulium-doped fiber 4 are written through the tail end of thulium-doped fiber 4. A high-reflection fiber Bragg grating with a reflectivity greater than 90% , is almost completely reflected by the high-reflection fiber Bragg grating, and is reflected into the thulium-doped fiber 4 and the phosphorus-doped fiber 3 to further amplify the required random laser light. The high-reflection fiber Bragg grating will generate multiple reflections due to the backward Rayleigh scattering generated by the single-mode phosphorus-doped fiber 3, which greatly improves the gain. Finally, the 1974nm distributed feedback random laser and 1974nm stimulated radiation laser that have been amplified many times are fed back to the com port of the wavelength division multiplexer 2 to the wavelength division multiplexer 2, and the wavelength division multiplexer 2 converts the 1974nm feedback light from the 1950 terminal output.

Claims (3)

1. The utility model provides a 2um optic fibre random laser of mixed gain semi-open cavity structure which characterized in that distributed feedback optic fibre random laser includes:

the pump light source is used for generating 1566nm pump laser, 1566nm simultaneously corresponds to the pump absorption wavelength of the thulium-doped optical fiber, and has the pump wavelength of 1320cm-1 Raman frequency shift phosphorus-doped optical fiber at a 2-micron waveband, so that the pump light source can simultaneously provide stimulated Raman scattering gain for the phosphorus-doped optical fiber, provide active gain for the thulium-doped optical fiber, and realize the mixed gain of the 2-micron waveband;

the first end of the wavelength division multiplexer is connected with the pumping light source; the second end of the wavelength division multiplexer is connected with the output port;

the wavelength division multiplexer is used for coupling the pump light generated by the pump light source to the phosphorus-doped optical fiber, and the phosphorus-doped optical fiber is used for amplifying Raman gain generated by a stimulated Raman scattering effect on the pump light;

the thulium-doped optical fiber is connected with the other end of the phosphorus-doped optical fiber and is used for carrying out active gain amplification on residual pump light after passing through the phosphorus-doped optical fiber;

and the high-reflectivity optical fiber Bragg grating connected with the other end of the thulium-doped optical fiber selects and determines the laser wavelength of 2-micron waveband, and forms a semi-open cavity structure together with distributed Rayleigh scattering in the phosphorus-doped optical fiber.

2. The 2um fiber random laser with the hybrid gain semi-open cavity structure as claimed in claim 1, wherein the pump light source wavelength and the high reflectivity fiber bragg grating wavelength correspond to the raman frequency shift of the phosphorus doped fiber in 1320cm "1, and correspond to the absorption and gain bands of the thulium doped fiber, respectively.

3. The 2um optical fiber random laser with the hybrid gain semi-open cavity structure as claimed in claim 1, wherein the fiber tail end in the structure is a bevel fiber, so as to avoid generating end face feedback, and ensure that the feedback of the cavity is provided only by a point-type high-reflectivity fiber bragg grating and distributed rayleigh scattering, so as to satisfy the characteristics of random laser open cavity and no resonance, and ensure that the generated laser has the characteristics of no longitudinal mode structure and low noise.

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