Random laser based on biconical fiber and multi-wavelength laser output method

Abstract

The invention belongs to the technical field of optical fiber lasers, and particularly relates to a random laser based on a biconical optical fiber and a multi-wavelength laser output method. The random laser based on the single-mode biconical optical fiber comprises an optical fiber reflector, a biconical optical fiber, an optical fiber coupler, a wavelength division multiplexer, an erbium-doped optical fiber, an optical fiber random Rayleigh scattering feedback unit and an optical fiber 8-degree chamfer which are connected in sequence. A signal light port of the wavelength division multiplexer is connected with an input port of the optical fiber coupler, a public port of the wavelength division multiplexer is connected with an input port of the erbium-doped optical fiber, and a pump light port of the wavelength division multiplexer is connected with an output port of the 980nm laser. According to the invention, multi-wavelength selection in the random laser is realized by using the comb filtering function of the biconical fiber; random Rayleigh scattering in the optical fiber random Rayleigh scattering feedback unit is used as optical feedback, and the random Rayleigh scattering feedback unit and the reflector form a laser cavity. And multi-wavelength laser output is formed.

Description

Technical Field

[0001] The present invention belongs to the technical field of fiber lasers, and more specifically, relates to a random laser based on dual-core fiber and a multi-wavelength laser output method. Background Art

[0002] As a new type of laser device, the random laser has the advantages of simple structure, easy preparation, and low cost. However, there are still many challenges in the optical feedback mechanism, pump efficiency, and laser output stability of traditional random lasers. Therefore, developing a new type of random laser system to improve the stability and efficiency of laser output has become an important topic in the current laser technology field.

[0003] In the field of random fiber lasers, in 2010, Turitsyn et al. [Turitsyn S K, Babin S A, El-Taher A E, et al. Random distributed feedback fibre laser[J]. Naturephotonics, 2010, 4(4): 231-235.] first realized a random laser based on optical fiber as a random medium, and since then, random lasers have attracted extensive research. In the prior literature [El-Taher A E, Harper P, Babin S A, et al. Effect of Rayleigh-scattering distributed feedback on multiwavelength Ramanfiber laser generation[J]. Optics letters, 2011, 36(2): 130-132.], a resonant cavity was formed by using an array of 22 fiber Bragg gratings with different central wavelengths and the random distributed feedback provided by the Rayleigh scattering of a long optical fiber, achieving the output of 22 stable wavelengths. In the prior patent [2015, China Jiliang University, A random fiber laser based on a random phase-shifted fiber grating, CN104577678A], random feedback was provided by using a first random phase-shifted fiber grating and a second random phase-shifted fiber grating to achieve laser oscillation. In the prior literature [Wang Z, Wu H, Fan M, et al. Third-order randomlasing via Raman gain and Rayleigh feedback within a half-open cavity[J].Optics express, 2013, 21(17): 20090-20095.], third-order random laser output at 1670 nm was achieved by using a G.652 optical fiber and an optical fiber loop mirror. In the prior literature [Ahmad H, Zulkifli M Z, Jemangin M H, etal. Distributed feedback multimode Brillouin-Raman random fiber laser in theS-band[J]. Laser Physics Letters, 2013, 10(5): 055102.], stable multi-wavelength output of five Stokes orders was achieved by using dispersion compensation fiber through an all-open cavity structure.In the prior literature

Wu H, Wang Z, Jia X, et al. Flat amplitude multiwavelength Brillouin–Raman random fiber laser with a half-open cavity[J]. Applied Physics B, 2013, 112: 467-471.

Wang Z, Wu H, Fan M, et al. Broadband flat-amplitude multiwavelength Brillouin-Raman fiber laser with spectral reshaping by Rayleigh scattering[J]. Optics express, 2013, 21(24): 29358-29363.

Huang C, Dong X, Zhang N, et al. Multiwavelength Brillouin-erbium random fiber laser incorporating a chirped fiber Bragg grating[J]. IEEE Journal of Selected Topics in Quantum Electronics, 2014, 20(5): 294-298.

Sugavanam S, Yan Z, Kamynin V, et al. Multiwavelength generation in a random distributed feedback fiber laser using an all fiber Lyot filter[J]. Optics express, 2014, 22(3): 2839-2844.

[0004] The present invention is proposed to improve the mode control ability of a random laser and optimize the wavelength selection mechanism in the cavity. Its purpose is to achieve efficient multi-wavelength random laser output by utilizing the comb filtering ability of dual-core fiber.

[0005] The present invention adopts the following technical solutions: A random laser based on a single-mode biconical fiber, comprising a fiber mirror, a biconical fiber, a fiber coupler, a wavelength division multiplexer, an erbium-doped fiber, a fiber random Rayleigh scattering feedback unit, and an 8° angled fiber end, which are connected in sequence; specifically: the fiber mirror is connected to the biconical fiber, the other end of the biconical fiber is connected to the main output port of the fiber coupler, the input port of the fiber coupler is connected to the signal light port of the wavelength division multiplexer, the pump light port of the wavelength division multiplexer is connected to a 980 nm laser, the common port of the wavelength division multiplexer is connected to the input port of the erbium-doped fiber, the other end of the erbium-doped fiber is connected to the fiber random Rayleigh scattering feedback unit, and the other end of the fiber random Rayleigh scattering feedback unit is connected to the end face of the 8° angled fiber.

[0006] In the above technical solution, the first port of the fiber mirror of the fiber mirror is connected to the first port of the biconical fiber of the biconical fiber. The fiber mirror is used to provide optical feedback to ensure stable oscillation of the laser in the resonant cavity.

[0007] In the above technical solution, the biconical fiber includes two conical structures, and the conical structure includes a lower cone region, a waist region, and an upper cone region. In the lower cone region and the upper cone region, the diameters of the cladding and the core of the fiber gradually change, while in the waist region, the diameter of the cladding of the fiber is reduced to a certain extent, so that light can leak into the cladding and excite higher-order mode light therein. The biconical fiber has a comb-shaped filtering function.

[0008] In the above technical solution, in the conical structure, in its lower cone region, the diameters of the fiber cladding and the core gradually decrease; in its waist region, the diameter of the fiber cladding is about 20 μm or smaller, and the diameter of the fiber core is thin enough to be negligible; in its upper cone region, the diameters of the fiber cladding and the core gradually increase. When light is transmitted in the lower cone region, the light in the core gradually leaks into the cladding as the core diameter decreases; when it is transmitted to the waist region, a new refractive index difference is formed between the cladding and the environment outside the cladding, and more higher-order mode light is excited in the cladding; when light is transmitted in the upper cone region, the light in the waist region is gradually transmitted into the core as the core diameter of the core increases, and finally completely enters the core. The fundamental mode and the higher-order modes interfere with each other to form a comb-shaped output spectrum, presenting a filtering effect.

[0009] In the above technical solution, the fiber coupler is a 1:9 fiber coupler.

[0010] In the above technical solution, the fiber coupler has two output ports, namely a 90% main output port and a 10% output and monitoring port. The 90% main output port of the fiber coupler is connected to the biconical fiber.

[0011] In the above technical solution, the second port of the biconical fiber of the biconical fiber is connected to the 90% main output port of the fiber coupler, and the input port of the fiber coupler of the fiber coupler is connected to the signal light port of the wavelength division multiplexer.

[0012] In the above technical solution, the pump light port of the wavelength division multiplexer is connected to the first port of the 980 nm laser of the 980 nm laser, and the common port of the wavelength division multiplexer is connected to the first port of the erbium-doped fiber of the erbium-doped fiber.

[0013] In the above technical solution, the wavelength division multiplexer is a 980 / 1550 three-port wavelength division multiplexer.

[0014] In the above technical solution, the 980 nm laser is a pump light source.

[0015] In the above technical solution, the second port of the erbium-doped fiber of the erbium-doped fiber is connected to the first port of the fiber random Rayleigh scattering feedback unit of the fiber random Rayleigh scattering feedback unit.

[0016] In the above technical solution, the erbium-doped fiber is a 10 m long erbium-doped fiber.

[0017] In the above technical solution, further, the fiber random Rayleigh scattering feedback unit is a long-distance single-mode fiber or a random fiber grating (array), which provides random Rayleigh scattering feedback, and forms a laser cavity with a fiber mirror.

[0018] In the above technical solution, the second port of the fiber random Rayleigh scattering feedback unit of the fiber random Rayleigh scattering feedback unit is connected to the port of the 8° cut angle (fiber connector) of the fiber.

[0019] In the above technical solution, the 8° cut angle fiber end face is an FC / APC fiber connector or the bare fiber end face is directly polished into an 8° angle.

[0020] The second object of the present invention is to provide a multi-wavelength laser output method for a random laser based on a single-mode biconical fiber. The 980 nm laser 4 is used as a pump source and is connected to the erbium-doped fiber 6 through a wavelength division multiplexer 5 to form an erbium-doped fiber amplifier. The random Rayleigh scattering in the fiber random Rayleigh scattering feedback unit 7 provides random optical feedback and forms a random laser oscillation cavity together with the fiber mirror 1. Lights of multiple wavelengths oscillate in the laser oscillation cavity and are amplified by the erbium-doped fiber amplifier, and finally stable multi-wavelength laser is formed. The laser is output through the 10% port of the fiber coupler.

[0021] Combining all the above technical solutions, the advantages and positive effects of the present invention are as follows: The present invention utilizes the comb filtering function of the biconical fiber to realize multi-wavelength selection in the random laser; uses the random Rayleigh scattering in the fiber random Rayleigh scattering feedback unit as optical feedback and forms a laser cavity with a mirror; and forms multi-wavelength laser output. Description of the Drawings

[0022] The accompanying drawings here are incorporated into the specification and form a part of this specification, showing embodiments in accordance with the present disclosure, and are used together with the specification to explain the principles of the present disclosure; Figure 1 is a schematic structural diagram of a random laser based on a dual - cone fiber; Figure 2 is the comb - filter spectrum diagram of the dual - cone fiber; Figure 3 is the output spectrum diagram of the random laser; Figure 4 is the threshold and conversion efficiency diagram of the random laser.

[0023] Wherein: 1 Fiber mirror; 2 Dual - cone fiber; 3 Fiber coupler; 4 980nm laser; 5 Wavelength - division multiplexer; 6 Er - doped fiber; 7 Fiber random Rayleigh scattering feedback unit; 8 8° fiber cut - angle; 11 First port of the fiber mirror; 21 First port of the dual - cone fiber; 22 Second port of the dual - cone fiber; 31 90% main output port; 32 10% output and monitoring port; 33 Input port of the fiber coupler; 41 First port of the 980nm laser; 51 Signal - light port; 52 Common port; 53 Pump - light port; 61 First port of the Er - doped fiber; 62 Second port of the Er - doped fiber; 71 First port of the fiber random Rayleigh scattering feedback unit; 72 Second port of the fiber random Rayleigh scattering feedback unit; 81 8° fiber cut - angle port. Detailed implementation manners

[0024] To make the above objects, features, and advantages of the present invention more apparent and understandable, the following provides a detailed description of the specific embodiments of the present invention with reference to the accompanying drawings. A lot of specific details are set forth in the following description to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the spirit of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0025] The following further elaborates on the present invention with specific embodiments. It should be understood that the specific embodiments described herein are merely for explaining the present invention and are not used to limit the present invention.

[0026] As Figure 1 shown, a random laser based on a single-mode biconical fiber includes a fiber mirror 1, where the fiber mirror 1 is connected to one end of a single-mode biconical fiber 2, the other end of the single-mode biconical fiber 2 is connected to the main output port of a fiber coupler 3, the input port of the fiber coupler 3 is connected to the signal light port of a wavelength division multiplexer 5, the pump light port of the wavelength division multiplexer 5 is connected to a 980 nm laser 4, the common end of the wavelength division multiplexer 5 is connected to an erbium-doped fiber 6, the other end of the erbium-doped fiber 6 is connected to a fiber random Rayleigh scattering feedback unit 7, and the other end of the fiber random Rayleigh scattering feedback unit 7 is connected to an 8° fiber angle 8.

[0027] Furthermore, it can also be considered in this embodiment that the reflectivity of the fiber mirror 1 > 99%, and the pigtail length is 0.5 m.

[0028] Furthermore, it can also be considered in this embodiment that the first port 11 of the fiber mirror 1 of the fiber mirror is connected to the first port 21 of the biconical fiber 2 of the biconical fiber.

[0029] Furthermore, it can also be considered in this embodiment that the biconical fiber 2 includes two conical structures (lower cone region, waist region, and upper cone region). In the lower cone region, the diameters of the fiber cladding and core gradually decrease; in the waist region, the diameter of the fiber cladding is approximately 20 μm or less, and the diameter of the fiber core is thin enough to be negligible; in the upper cone region, the diameters of the fiber cladding and core gradually increase. When light is transmitted in the lower cone region, the light in the core gradually leaks into the cladding as the core diameter decreases; when it is transmitted to the waist region, a new refractive index difference is formed between the cladding and the environment outside the cladding, and more high-order mode light is excited in the cladding; when light is transmitted in the upper cone region, the light in the waist region gradually enters the core as the core diameter of the core increases and finally completely enters the core. The fundamental mode and high-order modes interfere with each other to form a comb-shaped output spectrum, presenting a filtering effect. It has a wavelength selection function in the laser cavity of the fiber laser.

[0030] Furthermore, it can also be considered in this embodiment that the dual-taper fiber 2 can be fabricated by a fiber taper machine or high-voltage arc discharge. The two tapers included are the same, and the upper taper region and the lower taper region of each taper are symmetric. As Figure 2 shown, the extinction ratio of the dual-taper filter spectrum is 10 dB, and the free spectral range is 3.7 nm.

[0031] Furthermore, it can also be considered in this embodiment that the second port 22 of the dual-taper fiber of the dual-taper fiber 2 is connected to the 90% main output port 31 of the fiber coupler 3. The splitting ratio between the 90% main output port 31 and the 10% output and monitoring port 32 is 9:1, and 10% of the laser is used as the output of the entire random fiber laser.

[0032] Furthermore, it can also be considered in this embodiment that the fiber coupler input port 33 of the fiber coupler 3 is connected to the signal light port 51 of the wavelength division multiplexer 5. The pump light port 53 of the wavelength division multiplexer 5 is connected to the output port of the 980 nm laser 4, that is, the first port 41 of the 980 nm laser. The output optical power of the 980 nm pump laser 4 is adjustable between 0 mw and 1000 mw.

[0033] Furthermore, it can also be considered in this embodiment that the common port 52 of the wavelength division multiplexer 5 is connected to the first port 61 of the erbium-doped fiber 6 of the erbium-doped fiber.

[0034] Furthermore, it can also be considered in this embodiment that the length of the erbium-doped fiber is 10 m.

[0035] Furthermore, it can also be considered in this embodiment that the second port 62 of the erbium-doped fiber of the erbium-doped fiber 6 is connected to the input port of the fiber random Rayleigh scattering feedback unit 7, that is, the first port 71 of the fiber random Rayleigh scattering feedback unit.

[0036] Furthermore, it can also be considered in this embodiment that the fiber random Rayleigh scattering feedback unit 7 is a long-distance single-mode fiber that provides random Rayleigh scattering, and the length is 2 Km.

[0037] Furthermore, it can also be considered in this embodiment that the output port of the fiber random Rayleigh scattering feedback unit 7, that is, the second port 72 of the fiber random Rayleigh scattering feedback unit, is connected to the fiber 8° cut angle port 81 of the fiber 8° cut angle 8.

[0038] Furthermore, it can also be considered in this embodiment that the fiber 8° cut angle 8 uses an FC / APC fiber connector.

[0039] Taking this embodiment as an example, the random laser based on a single-mode biconical fiber has a linear laser structure, and its cavity includes a fiber mirror 1, a biconical fiber 2, a fiber coupler 3, a wavelength division multiplexer 5, an erbium-doped fiber 6, and a fiber random Rayleigh scattering feedback unit 7. Among them, a 980 nm laser 4 serves as a pump source and is connected to the erbium-doped fiber 6 through the wavelength division multiplexer 5 to form an erbium-doped fiber amplifier; the biconical fiber has a comb filtering function and can perform wavelength selection on the optical signals oscillating in the cavity; the random Rayleigh scattering in the fiber random Rayleigh scattering feedback unit 7 provides random optical feedback and, together with the fiber mirror 1, forms a random laser oscillation cavity. Lights of multiple wavelengths oscillate in the laser cavity and are amplified by the erbium-doped fiber amplifier, and finally stable multi-wavelength laser is formed. The laser is output through the 10% port of the fiber coupler.

[0040] The present invention utilizes the comb filtering function of the biconical fiber to achieve multi-wavelength selection in the random laser; uses the random Rayleigh scattering in the fiber random Rayleigh scattering feedback unit as optical feedback and forms a laser cavity with the mirror; and forms a multi-wavelength laser output.

[0041] The above are only the preferred embodiments of the present invention. It should be understood that the described embodiments are a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention. The present invention is not limited to the form disclosed herein, should not be regarded as excluding other embodiments, and can be used in various other combinations, modifications, and environments. Changes and alterations made by those skilled in the art without departing from the spirit and scope of the present invention shall fall within the scope of protection of the appended claims of the present invention.

Claims

1. A random laser based on a single-mode biconical fiber, characterized in that: It includes a fiber optic mirror (1), a biconical fiber (2), a fiber optic coupler (3), a wavelength division multiplexer (5), an erbium-doped fiber (6), a fiber random Rayleigh scattering feedback unit (7), and an 8° fiber optic chamfer (8) connected in sequence. The signal light port (51) of the wavelength division multiplexer (5) is connected to the input port of the fiber optic coupler (3), the common port (52) of the wavelength division multiplexer (5) is connected to the input port of the erbium-doped fiber (6), and the pump light port (53) of the wavelength division multiplexer (5) is connected to the output port of a 980 nm laser (4).

2. The random laser based on a single-mode biconical fiber according to claim 1, wherein: The first fiber optic mirror port (11) of the fiber optic mirror (1) is connected to the first biconical fiber port (21) of the biconical fiber (2).

3. A random laser based on a single-mode biconical fiber according to claim 1, characterized in that: The biconical fiber (2) includes two conical structures, and each conical structure includes a lower cone region, a waist region, and an upper cone region.

4. A random laser based on a single-mode biconical fiber according to claim 3, characterized in that: In the conical structure, in its lower cone region, the diameters of the fiber cladding and the fiber core gradually decrease; in its waist region, the diameter of the fiber cladding is about 20 μm or less, and the diameter of the fiber core is thin enough to be negligible; in its upper cone region, the diameters of the fiber cladding and the fiber core gradually increase.

5. The random laser based on a single-mode biconical fiber according to claim 1, wherein: The fiber optic coupler (3) has two output ports, namely a 90% main output port (31) and a 10% output and monitoring port (32). The 90% main output port (31) of the fiber optic coupler (3) is connected to the biconical fiber (2), and the fiber optic coupler input port (33) of the fiber optic coupler (3) is connected to the signal light port (51) of the wavelength division multiplexer (5).

6. The random laser based on a single-mode biconical fiber according to claim 1, characterized in that: The pump light port (53) of the wavelength division multiplexer (5) is connected to the first 980 nm laser port (41) of the 980 nm laser (4), and the common port (52) of the wavelength division multiplexer (5) is connected to the first erbium-doped fiber port (61) of the erbium-doped fiber (6).

7. The random laser based on a single-mode biconical fiber according to claim 1, wherein: The second erbium-doped fiber port (62) of the erbium-doped fiber (6) is connected to the input port of the fiber random Rayleigh scattering feedback unit (7).

8. A random laser based on a single-mode biconical fiber according to claim 1, characterized in that: The random Rayleigh scattering feedback unit (7) is a long-distance optical fiber or a random fiber grating.

9. The random laser based on a single-mode biconical fiber according to claim 1, wherein: The output port of the fiber random Rayleigh scattering feedback unit (7) is connected to the port of the 8° fiber optic chamfer (8).

10. A multi-wavelength laser output method for a random laser based on a single-mode biconical fiber, characterized in that: The output method is as follows: The 980 nm laser 4 serves as a pump source and is connected to the erbium-doped fiber 6 through the wavelength division multiplexer 5 to form an erbium-doped fiber amplifier. The random Rayleigh scattering in the fiber random Rayleigh scattering feedback unit 7 provides random optical feedback and, together with the fiber optic mirror 1, forms a random laser oscillation cavity. Lights of multiple wavelengths oscillate in the laser oscillation cavity and are amplified by the erbium-doped fiber amplifier, and finally, stable multi-wavelength laser is formed. The laser is output through the 10% port of the fiber optic coupler.

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