A broadband high-order Raman fiber random laser

Abstract

The present invention discloses a broadband high-order Raman fiber random laser, which includes a tunable ytterbium-doped fiber laser seed source, a diode pump source, a pump combiner, a ytterbium-doped fiber, a second optical fiber isolator, a first wavelength division multiplexer, a Raman fiber, a second wavelength division multiplexer, an optical fiber circulator, and a superluminescent light-emitting diode, which are connected in sequence; the tunable ytterbium-doped fiber laser seed source is used as a pump source for a cascaded Raman random laser after being amplified by the ytterbium-doped fiber, and a broadband fiber loop mirror and a first fiber bevel end face for laser output are connected to the first wavelength division multiplexer; the end face reflectivity of the first fiber bevel end face is adjustable; the superluminescent light-emitting diode is connected to the second wavelength division multiplexer through the optical fiber circulator; the present invention uses the tunable ytterbium-doped fiber laser to be power-amplified by the ytterbium-doped fiber amplifier to excite cascaded Raman random laser in the Raman fiber, injects the broadband seed backward, and adopts a fiber bevel end face with adjustable reflectivity at the output end to realize broadband high-order Raman random laser with low noise and controllable bandwidth, and solves the problems of large noise and difficult bandwidth regulation of high-order Raman random laser in the prior art.

Description

Technical Field

[0001] The present invention relates to the technical field of fiber lasers, and particularly relates to a broadband high-order Raman fiber random laser. Background Art

[0002] Laser sources with a bandwidth of dozens of nanometers have important applications in fiber optic communication, fiber optic sensing, and fiber optic gyroscopes. The three main existing broadband light sources include superluminescent fiber light sources, super-radiant light-emitting diodes, and supercontinuum light sources. However, due to the existence of nonlinear effects, the temporal stability of supercontinuum light sources is poor; the output band of superluminescent fiber light sources is limited by the energy level characteristics of doped ions, and the covered band is relatively narrow; although super-radiant light-emitting diodes can output broadband lasers in the visible and near-infrared bands, the output power is usually only a few milliwatts.

[0003] Fiber random lasers use the inherent random backward Rayleigh scattering in the fiber as a feedback mechanism to achieve laser oscillation, without the need for an optical resonator structure with very clear boundaries and parameters in traditional fiber lasers, reducing the requirements for cavity design, and having the advantages of low noise, simple structure, and high optical-optical conversion efficiency. Raman fiber random lasers use stimulated Raman scattering to provide gain. Compared with rare-earth ion-doped fiber lasers, special wavelength laser output can be obtained through the adjustment of pump wavelength and power and the cascaded Raman effect. It is a new type of fiber laser with flexible wavelength tunability.

[0004] By adopting a Raman fiber random laser with a semi-open cavity structure, the threshold of high-order Raman laser output can be greatly reduced. In the prior art, fiber gratings specially customized for each order of Stokes light are usually placed in the cavity or broadband mirrors are connected to provide point feedback for each order of Stokes light to construct a semi-open cavity structure. In the prior art, most cascaded Raman fiber random lasers usually use broadband mirrors and random Rayleigh feedback to achieve the output of forward-pumped high-order Raman random fiber lasers, but the generated high-order Raman random laser bandwidth is usually only a few nanometers, and the temporal intensity fluctuation is large and the relative intensity noise is high. Summary of the Invention

[0005] The purpose of the present invention is to provide a broadband high-order Raman fiber random laser, mainly by adding a broadband mirror at the pump end to construct a semi-open cavity structure to provide feedback for the Raman gain in dispersion-shifted fiber, reducing the laser oscillation threshold, and using a fiber bevel with adjustable reflectivity as the laser output port and the method of backward broadband seed injection to achieve a low-noise bandwidth-tunable broadband high-order Raman fiber random laser. This solution not only solves the problems of small bandwidth and poor temporal stability of high-order Raman random lasers in the prior art, but also solves the technical problems of limited power and non-tunable bandwidth of broadband light sources.

[0006] The technical solution adopted by the present invention is as follows:

[0007] A randomly tunable fiber laser with continuously tunable wavelength, comprising a diode pump source, a pump combiner, a ytterbium-doped fiber, a second fiber isolator, a first wavelength division multiplexer, a Raman fiber, a second wavelength division multiplexer, an optical fiber circulator, and a superluminescent light-emitting diode, which are connected in sequence; a tunable ytterbium-doped fiber laser seed source is connected to the signal end of the pump combiner through a first fiber isolator; a broadband fiber loop mirror and a first fiber bevel end face for laser output are connected to the first wavelength division multiplexer; a second fiber bevel end face for filtering residual pump light is connected to the second wavelength division multiplexer; a third fiber bevel end face is connected to the optical fiber circulator.

[0008] Furthermore, the tuning range of the tunable ytterbium-doped fiber laser seed source is 1040nm to 1090nm, the output power is greater than 500mW, and the output laser frequency has no longitudinal mode.

[0009] Furthermore, the laser diode pump source is a 976nm diode pump source.

[0010] Furthermore, the 1040nm to 1090nm ports of the first wavelength division multiplexer are connected to the amplified ytterbium-doped laser, the 1100nm to 1290nm ports are connected to the fiber loop mirror, the 1300nm to 1700nm ports are connected to the first fiber bevel end face for broadband Raman fiber laser output, and the common port is connected to the Raman fiber.

[0011] Furthermore, the Raman fiber is a dispersion-shifted fiber with a length less than 10km.

[0012] Furthermore, the 1000nm to 1290nm ports of the second wavelength division multiplexer are connected to the third fiber bevel end face for filtering residual pump light, the superluminescent light-emitting diode is connected to the 1300nm to 1700nm ports through the fiber loop mirror, and the common port is connected to the Raman fiber.

[0013] Furthermore, the reflectivity of the second fiber bevel end face and the third fiber bevel end face is less than 10 -6 .

[0014] Furthermore, the bandwidth of the superluminescent light-emitting diode is 50nm and the central wavelength is 1330nm.

[0015] Furthermore, one port of the optical fiber circulator is connected to the superluminescent light-emitting diode, the second port is connected to the second wavelength division multiplexer, and the third port is connected to the third fiber bevel end face.

[0016] Furthermore, the first fiber bevel end face is a fiber bevel end face with tunable reflectivity, and the tuning range of the end face reflectivity is controlled by the fiber end face bevel angle to be 10 -7 to 10 -2 .

[0017] The beneficial effects of the present invention are as follows:

[0018] (1) In the present invention, a broadband high-order Raman fiber random laser structure with backward broadband seed injection is adopted, which can reduce the transfer of pump noise to the broadband random laser, greatly reduce the relative noise intensity of the broadband high-order Raman fiber random laser, and a broadband high-order Raman fiber random laser with stable time domain can be obtained;

[0019] (2) In the present invention, the reflectivity of the fiber bevel end face is adjustable to control the intracavity feedback intensity, so as to realize the control of the bandwidth of the broadband random laser. Description of the Drawings

[0020] Figure 1 It is a schematic structural diagram of the broadband high-order Raman fiber random laser of the present invention.

[0021] Figure 2 It is a spectral evolution diagram of the broadband high-order Raman random laser in the embodiment of the present invention.

[0022] Figure 3 It is a wavelength tunable spectrogram of the broadband high-order Raman random laser in the embodiment of the present invention.

[0023] Figure 4 It is a time-domain fluctuation diagram of the broadband high-order Raman random laser in the embodiment of the present invention.

[0024] Figure 5 It is a numerical simulation diagram of the spectral evolution of the broadband high-order Raman fiber laser under different reflectivities of the first fiber bevel end face in the embodiment of the present invention.

[0025] In the figure: 1 - tunable ytterbium-doped fiber laser seed source, 2 - first fiber isolator, 3 - laser diode pump source, 4 - pump beam combiner, 5 - ytterbium-doped fiber, 6 - second fiber isolator, 7 - broadband fiber loop mirror, 8 - first fiber bevel end face, 9 - first wavelength division multiplexer, 10 - Raman fiber, 11 - second wavelength division multiplexer, 12 - second fiber bevel end face, 13 - fiber circulator, 14 - third fiber bevel end face, 15 - superluminescent light-emitting diode. Detailed Embodiments

[0026] The following further describes the present invention in conjunction with the drawings and specific embodiments.

[0027] As Figure 1As shown in the figure, a broadband high-order Raman fiber random laser includes a diode pump source 3, a pump combiner 4, a ytterbium-doped fiber 5, a second fiber isolator 6, a first wavelength division multiplexer 9, a Raman fiber 10, a second wavelength division multiplexer 11, an optical fiber circulator 13, and a superluminescent light-emitting diode 15, which are connected in sequence; a tunable ytterbium-doped fiber laser seed source 1 outputs ytterbium-doped fiber laser that can be continuously tuned from 1040 nm to 1090 nm, and is connected to the signal end of the pump combiner 4 through a first fiber isolator 2; the input ytterbium-doped fiber laser is amplified in the ytterbium-doped fiber 5, and sequentially passes through the second fiber isolator 6 and the first wavelength division multiplexer 9 to act as a pump source for high-order Raman random laser in the Raman fiber 10; a broadband fiber loop mirror 7 is connected through the first wavelength division multiplexer 9 at the pump end to provide point feedback for Stokes lights of all orders; a second fiber bevel end face 12 is connected to the second wavelength division multiplexer to filter out residual pump light; the second port of the optical fiber circulator 13 is connected to the second wavelength division multiplexer 11, and the third port is connected to a third fiber bevel end face 14 to prevent the random laser generated in the Raman fiber from damaging the superluminescent light-emitting diode 15; combining the Rayleigh scattering effect in the Raman fiber 10 and the broadband seed backward injection to achieve broadband high-order Raman random fiber laser output, and realizing the wavelength tuning of the broadband high-order Raman fiber random laser by tuning the wavelength of the tunable ytterbium-doped fiber laser; the first fiber bevel end face 8 at the laser output port is connected to the first wavelength division multiplexer 9, and the reflectivity value of the first fiber bevel end face 8 can be controlled by the fiber end face chamfer angle, and the bandwidth of the broadband random laser is regulated by regulating the intracavity feedback intensity for broadband random laser lasing.

[0028] Figure 2 It is the spectral evolution diagram of a broadband high-order Raman fiber random laser with a central wavelength of 1320 nm. As the pump power increases, the power of the broadband high-order Raman random laser gradually increases, and the spectral shape will become closer and closer to the Raman gain spectrum shape. When the pump power is large enough, under the combined action of Raman gain and random Rayleigh scattering in a 9-km Raman fiber, Raman random laser will be lasing, causing the spectral narrowing phenomenon of the broadband random laser. When the pump power reaches 9.38 W, the output broadband random laser power can reach up to 2.37 W at most, and the -3dB bandwidth is 11.8 nm.

[0029] Figure 3 It is the tunable spectrum diagram of a broadband high-order Raman fiber laser. Among them, the pump power is 9.38 W. By tuning the wavelength of the tunable ytterbium-doped fiber laser seed source, a continuously tunable broadband Raman random laser output with a central wavelength from 1315 nm to 1340 nm can be obtained, and the laser power and -3dB bandwidth fluctuate around 2 W and 10 nm respectively.

[0030] Figure 4It is the time-domain fluctuation diagram of a broadband high-order Raman fiber laser. The pump power is 9.38 W. Due to the structure of backward broadband seed injection, the walk-off effect between the signal light and the pump light in the fiber can reduce the transfer of pump noise in random laser to the output of broadband random laser, and a more stable laser output in the time domain can be obtained. As Figure 5 shown, the standard deviation divided by the average value calculated is 1.67%, indicating that this broadband high-order Raman random fiber laser has good short-term stability.

[0031] Figure 5 It is the numerical simulation diagram of the spectral evolution of a broadband high-order Raman fiber laser under different reflectivities of the first fiber inclined end face. As the pump power increases, the spectral bandwidth of the broadband high-order Raman fiber laser will gradually narrow, and there are differences in the spectral bandwidth under different end face reflectivities. When the pump power reaches 11 W, by adjusting the reflectivity of the first fiber inclined end face from 2×10 -4 to 5×10 -3 a broadband high-order Raman random laser output with a tunable bandwidth from 11.54 nm to 9.54 nm can be realized.

Claims

1. A broadband high-order Raman fiber random laser, characterized in that, It includes a tunable ytterbium-doped fiber laser seed source (1), a first fiber isolator (2), a pump combiner (4), a ytterbium-doped fiber (5), a second fiber isolator (6), a first wavelength division multiplexer (9), a Raman fiber (10), a second wavelength division multiplexer (11), an optical fiber circulator (13), and a superluminescent light-emitting diode (15) connected in sequence; the tunable ytterbium-doped fiber laser seed source (1) is connected to the signal end of the pump combiner (4) through the first fiber isolator (2); a laser diode pump source (3) is connected to the pump end of the pump combiner (4); the ytterbium-doped fiber (5) is connected to the output end of the pump combiner (4); the other end of the ytterbium-doped fiber (5) is connected to the second fiber isolator (6); the second fiber isolator (6) is connected to the first port of the first wavelength division multiplexer (9); a broadband fiber loop mirror (7) and a first fiber bevel end face (8) for laser output are respectively connected to the second port and the third port of the first wavelength division multiplexer (9); the end face reflectivity of the first fiber bevel end face (8) is tunable; the fourth port of the first wavelength division multiplexer (9) is connected to one end of the Raman fiber (10); a second fiber bevel end face (12) for filtering residual pump light is connected to the first port of the second wavelength division multiplexer (11); a third fiber bevel end face (14) is connected to the optical fiber circulator (13); the superluminescent light-emitting diode (15) is connected to the second port of the second wavelength division multiplexer (11) through the optical fiber circulator (13); the third port of the second wavelength division multiplexer (11) is connected to the other end of the Raman fiber (10).

2. The broadband high-order Raman fiber random laser according to claim 1, characterized in that, The tuning range of the tunable ytterbium-doped fiber laser seed source (1) is 1040 nm to 1090 nm, the output power is greater than 500 mW, and the output laser has no longitudinal mode.

3. The broadband high-order Raman fiber random laser according to claim 1, characterized in that The laser diode pump source (3) is a 976 nm diode pump source.

4. A broadband high-order Raman fiber random laser according to claim 1, wherein The first port of the first wavelength division multiplexer (9) conducts the 1040 nm to 1090 nm band; the second port conducts the 1100 nm to 1290 nm band, the third port conducts the 1300 nm to 1700 nm band, and the fourth port is the common end.

5. A broadband high-order Raman fiber random laser according to claim 1, characterized in that, The Raman fiber (10) is a dispersion-shifted fiber with a length less than 10 km.

6. The broadband high-order Raman fiber random laser according to claim 1, wherein, The first port of the second wavelength division multiplexer (11) conducts the 1000 nm to 1290 nm band, the second port conducts the 1300 nm to 1700 nm band, and the third port is the common end.

7. A broadband high-order Raman fiber random laser according to claim 1, characterized in that The reflectivities of the second optical fiber bevel end face (12) and the third optical fiber bevel end face (14) are less than 10 -6 .

8. A broadband high-order Raman fiber random laser according to claim 1, characterized in that, The first optical fiber beveled end face (8) is an optical fiber beveled end face with adjustable reflectivity. The reflectivity tuning range is controlled by the bevel angle of the optical fiber end face to be 10 -7 to 10 -2 .

9. A broadband high-order Raman fiber random laser according to claim 1, wherein The bandwidth of the superluminescent light-emitting diode (15) is 50 nm and the central wavelength is 1330 nm.

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