Broadband tunable fiber laser device based on wavefront regulation and control

Abstract

The invention belongs to the field of spectral analysis, and provides a broadband tunable fiber laser device based on wavefront regulation, which comprises a pumping source 1, a fiber bragg grating 2, a first wavelength division multiplexer 3, a true wave fiber 4, a second wavelength division multiplexer 5, a dispersion shifted fiber 6, an isolator 7, a collimating lens 8, a digital micromirror device 9, a coupling objective lens 10, a multimode fiber 11 and a fiber coupler 12. According to the invention, the Rayleigh scattering effect in the optical fiber and the nonlinear effect of the true wave optical fiber are utilized to simultaneously generate the first-order broadband random laser and the first-order super-continuum laser as pumping sources of the super-continuum laser, so that the spectrum is rapidly broadened to generate the stable broadband super-continuum laser, and the generation of the second-order random laser is effectively inhibited; in addition, a digital micromirror device is used for carrying out wavefront modulation on the broadband super-continuous laser, and wavelength microsecond-level fast tuning is achieved; in addition, higher complexity is brought to randomness of the multi-mode optical fiber through the bent fixing device, and the length of the multi-mode optical fiber is effectively shortened.

Description

Technical Field

[0001] This invention belongs to the field of spectral analysis, specifically providing a broadband tunable fiber laser device based on wavefront modulation. Background Technology

[0002] Spectroscopic analysis technology refers to the technique of analyzing the composition and content of substances through spectral analysis. It is widely used in fields such as biomedicine, food testing, and materials science, including Raman spectroscopy, atomic spectroscopy, and fluorescence spectroscopy. In practical applications, different spectroscopic analysis techniques have different requirements for light sources. Generally, the light source for spectroscopic analysis techniques needs to meet requirements such as narrow linewidth, high brightness, and stability. Among these, the narrower the spectral linewidth of the light source, the higher the resolution of the substance's spectrum, and sufficient brightness is required to penetrate the substance or excite its fluorescence. At the same time, due to the real-time nature of biological tissue spectra, the light source must meet the requirements of stability and rapid wavelength tuning.

[0003] Supercontinuum laser technology is a technique that uses high-peak-power laser pulses to excite nonlinear effects in a medium, resulting in significant spectral broadening. Its generation depends on the synergistic effect of nonlinear effects and dispersion management. When a high-peak-power laser pulse propagates in the medium, nonlinear effects such as self-phase modulation, Raman scattering, four-wave mixing, and soliton dynamics dominate the spectral broadening. Currently, researchers are optimizing supercontinuum lasers in various aspects, including structure, pumping technology, and materials, and they are widely used in biomedical imaging, spectral analysis and sensing, optical communication and information processing, and industrial processing. Due to its wide spectral width and high brightness, supercontinuum lasers can be filtered to obtain a single-wavelength high-brightness laser source for spectral analysis. Based on this, this invention provides a broadband tunable fiber laser device based on wavefront modulation. Summary of the Invention

[0004] The purpose of this invention is to provide a broadband tunable fiber laser device based on wavefront modulation, which couples supercontinuum generated by fiber nonlinearity into a multimode fiber after wavefront modulation to produce a narrow linewidth laser output at a specific wavelength. The system has low complexity and can be applied to the field of spectral analysis.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A broadband tunable fiber laser device based on wavefront modulation, characterized in that it comprises: a pump source 1, a fiber Bragg grating 2, a first wavelength division multiplexer 3, a true-wavelength fiber 4, a second wavelength division multiplexer 5, a dispersion-shifting fiber 6, an isolator 7, a collimating lens 8, a digital micromirror device 9, a coupling objective lens 10, a multimode fiber 11, and a fiber coupler 12; wherein:

[0007] Pump source 1 emits Raman laser, which enters the true wave fiber 4 through the first wavelength division multiplexer 3 to generate forward first-order supercontinuum laser. At the same time, the true wave fiber 4 synchronously generates backward first-order random laser. The backward first-order random laser is reflected by the fiber Bragg grating 2 and then enters the dispersion-shifted fiber 6 together with the forward first-order supercontinuum laser through the second wavelength division multiplexer 5. The dispersion-shifted fiber 6 generates broadband supercontinuum laser.

[0008] After passing through isolator 7, broadband supercontinuum laser is irradiated onto digital micromirror device 9 by collimating lens 8. A predetermined modulation pattern is loaded onto digital micromirror device to perform wavefront modulation of broadband supercontinuum laser. After modulation, the beam is focused and injected into multimode fiber 11 after passing through coupling objective lens 10. The filtered beam is output from multimode fiber 11.

[0009] The filtered beam is transmitted to the second wavelength division multiplexer 5 via the high-power end of the fiber coupler 12 as feedback, forming a ring cavity. After resonance within the ring cavity, a narrow linewidth laser is formed, which is output from the low-power end of the fiber coupler 12.

[0010] Furthermore, the multimode fiber is placed in a bending fixture, so that the multimode fiber is arranged in a wavy line.

[0011] Furthermore, the optical aperture of the coupling objective is larger than the beam diameter of the modulated beam, and the numerical aperture of the coupling objective is smaller than or equal to the numerical aperture of the multimode fiber.

[0012] Furthermore, the pump source emits Raman laser light at a wavelength of 1455 nm.

[0013] Furthermore, the wavelength of the backward first-order random laser is 1550 nm.

[0014] Furthermore, a 10 / 90 fiber optic coupler is used.

[0015] Based on the above technical solution, the beneficial effect of the present invention is that it provides a tunable fiber laser device based on wavefront modulation, which has the following advantages:

[0016] 1. This invention utilizes the Rayleigh scattering effect in optical fiber and the nonlinear effect of true wave optical fiber to simultaneously generate first-order broadband random laser and first-order supercontinuum laser as pump sources for supercontinuum laser, enabling the spectrum to be rapidly broadened to generate stable broadband supercontinuum laser, while effectively suppressing the generation of second-order random laser.

[0017] 2. This invention utilizes the correspondence between the spatial mode of the incoming multimode fiber and the output spectrum, and by loading different modulation patterns onto a digital micromirror device, it can achieve microsecond-level rapid wavelength switching of the output laser.

[0018] 3. The present invention uses a bent fiber fixer to fix the multimode fiber, ensuring the overall time stability of the system; at the same time, the bent structure brings higher complexity to the randomness of the multimode fiber, effectively shortening the required length of the multimode fiber. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of the broadband tunable fiber laser device based on wavefront modulation in this invention; wherein, 1-pump source, 2-fiber Bragg grating, 3-first wavelength division multiplexer, 4-true wave fiber, 5-second wavelength division multiplexer, 6-dispersion shift fiber, 7-isolator, 8-collimating lens, 9-digital micromirror device, 10-coupled objective lens, 11-multimode fiber, 12-10 / 90 fiber coupler, 13-spectrum analyzer.

[0020] Figure 2 This is the laser spectrum output from the true wave fiber of the broadband tunable fiber laser device based on wavefront modulation in an embodiment of the present invention.

[0021] Figure 3 This is the laser spectrum output from the dispersion-shifted fiber of the broadband tunable fiber laser device based on wavefront modulation in this embodiment of the invention.

[0022] Figure 4 The output laser spectrum of the broadband tunable fiber laser device based on wavefront modulation in this embodiment of the invention is shown. Detailed Implementation

[0023] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0024] This embodiment provides a tunable fiber laser device based on wavefront modulation, such as... Figure 1 As shown, it specifically includes: a pump source 1, a fiber Bragg grating 2, a first wavelength division multiplexer 3, a true wave fiber 4, a second wavelength division multiplexer 5, a dispersion-shifting fiber 6, an isolator 7, a collimating lens 8, a digital micromirror device 9, a coupling objective 10, a multimode fiber 11, and a 10 / 90 fiber coupler 12; wherein:

[0025] Pump source 1 emits a 1455nm Raman laser, which enters a true-wavelength fiber 4 via a first wavelength division multiplexer 3 to generate a forward first-order supercontinuum laser. Simultaneously, due to the randomly distributed Rayleigh scattering in the true-wavelength fiber 4, a backward first-order random laser with a wavelength of 1550nm is generated. This backward first-order random laser is reflected by a fiber Bragg grating 2 and then enters a dispersion-shifted fiber 6 along with the forward first-order supercontinuum laser via a second wavelength division multiplexer 5. Under the combined effect of the nonlinearity of the dispersion-shifted fiber 6, the spectrum is significantly broadened, generating a broadband supercontinuum laser. The laser spectrum output from the kilometer-scale true-wavelength fiber 4 is as follows: Figure 2 As shown in the figure, a first-order random laser is excited at 1550 nm, and the first-order supercontinuum spectrum broadens to 1650 nm; the supercontinuum laser spectrum output from dispersion-shifted fiber 6 is as follows. Figure 3 As shown in the figure, the intensity of the spectrum remains stable between 1450nm and 1650nm. The first-order random laser and the first-order supercontinuum laser are coupled into the dispersion-shifted fiber as pump light through the second wavelength division multiplexer. Under the action of modulation instability, stimulated Raman scattering and four-wave mixing, the spectrum gradually broadens, and the spectrum is greatly broadened to generate a 200nm broadband supercontinuum laser.

[0026] After passing through isolator 7, the broadband supercontinuum laser is irradiated onto digital micromirror device 9 by collimating lens 8. A predetermined modulation pattern is loaded onto digital micromirror device to perform wavefront modulation on the broadband supercontinuum laser. After modulation, the beam is focused and injected into fixed multimode fiber 11 after passing through coupling objective lens 10. After random scattering in multimode fiber 11, a filtered beam with an advantageous wavelength is output.

[0027] The filtered beam is transmitted through the high-power end of the 10 / 90 fiber coupler 12 to the second wavelength division multiplexer 5 and re-enters the optical path to generate feedback, forming a ring cavity; the filtered beam resonates in the ring cavity to form a narrow linewidth laser, and is output through the low-power end of the fiber coupler 12.

[0028] The dot after multimode fiber 11 is the fusion splice point between multimode fiber and single-mode fiber. There is a mode field mismatch between multimode fiber and single-mode fiber. The spectral profile fed back to the active part is determined by the mode field overlap at the fusion splice point between multimode fiber and single-mode fiber. The output spectrum can be adjusted by changing the spatial mode field entering the multimode fiber, and by loading a large number of different modulation patterns onto the digital micromirror device, recording the output spectrum of the multimode fiber, selecting the modulation pattern corresponding to the desired wavelength and loading it onto the digital micromirror device in sequence to achieve wavelength scanning.

[0029] Furthermore, the multimode fiber 11 is placed in a bending fixture, so that the multimode fiber 11 is arranged in a wavy line shape; the bending fixture increases the optical field complexity in the multimode fiber, shortens the length of the multimode fiber required to achieve the above-mentioned correspondence between the spatial mode field and the output spectrum of the multimode fiber, and ensures the stability of the multimode fiber.

[0030] Furthermore, in order to ensure that the modulated beam of the digital micromirror device is coupled into the multimode fiber as much as possible, the aperture of the coupling objective needs to be larger than the beam diameter of the modulated beam, and the numerical aperture of the coupling objective needs to be smaller than or equal to the numerical aperture of the multimode fiber.

[0031] In this embodiment, a spectrometer 13 is used to collect and observe the output laser spectrum, such as... Figure 4The image shows the output laser spectrum of the wavefront-modulated tunable fiber laser device. The filtered spectrum, after being modulated by a digital micromirror device with a corresponding modulation pattern and then randomly scattered by a multimode fiber, is shown below. Figure 4 As shown in the left-middle figure, the triangular points represent the dominant longitudinal modes in the spectrum; after modulation, the beam resonates and feedbacks in the ring cavity. Due to mode competition, the final output is a single-wavelength, narrow-linewidth laser spectrum, as shown in the figure. Figure 4 As shown in the middle right figure.

[0032] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar features unless otherwise specified. All disclosed features, or steps in all methods or processes, may be combined in any way except for mutually exclusive features and / or steps.

Claims

1. A broadband tunable fiber laser device based on wavefront modulation, characterized in that, include: Pump source (1), fiber Bragg grating (2), first wavelength division multiplexer (3), true wave fiber (4), second wavelength division multiplexer (5), dispersion-shifting fiber (6), isolator (7), collimating lens (8), digital micromirror device (9), coupling objective (10), multimode fiber (11), and fiber coupler (12); wherein: The pump source (1) emits Raman laser, which enters the true wave fiber (4) through the first wavelength division multiplexer (3) to generate a forward first-order supercontinuum laser. At the same time, the true wave fiber (4) synchronously generates a backward first-order random laser. The backward first-order random laser is reflected by the fiber Bragg grating (2) and then enters the dispersion-shifted fiber (6) together with the forward first-order supercontinuum laser through the second wavelength division multiplexer (5). The dispersion-shifted fiber (6) generates a broadband supercontinuum laser. After passing through the isolator (7), the broadband supercontinuum laser is irradiated onto the digital micromirror device (9) by the collimating lens (8). A predetermined modulation pattern is loaded onto the digital micromirror device to perform wavefront modulation on the broadband supercontinuum laser. After modulation, the beam is focused and injected into the multimode fiber (11) after passing through the coupling objective (10). The filtered beam is output from the multimode fiber (11). The filtered beam is transmitted to the second wavelength division multiplexer (5) via the high-power end of the fiber coupler (12) as feedback to form a ring cavity. The filtered beam resonates in the ring cavity to form a narrow linewidth laser. The other low-power end of the fiber coupler (12) is used as the output of the narrow linewidth laser.

2. The broadband tunable fiber laser device based on wavefront modulation according to claim 1, characterized in that, The multimode fiber is placed in a bending fixture, so that the multimode fiber is arranged in a wavy line.

3. The broadband tunable fiber laser device based on wavefront modulation according to claim 1, characterized in that, The aperture of the multimode fiber placed in the bending coupling objective is larger than the beam diameter of the beam after adjustment, and the numerical aperture of the coupling objective is less than or equal to the numerical aperture of the multimode fiber.

4. The broadband tunable fiber laser device based on wavefront modulation according to claim 1, characterized in that, The multimode fiber is placed in a bending pump source to emit Raman laser light with a wavelength of 1455nm.

5. The broadband tunable fiber laser device based on wavefront modulation according to claim 1, characterized in that, The wavelength of the backward first-order random laser is 1550 nm.

6. The broadband tunable fiber laser device based on wavefront modulation according to claim 1, characterized in that, The fiber optic coupler is a 10 / 90 fiber optic coupler.

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