Titanium carbide-based 1-micron narrow-bandwidth space-time mode-locked stress sensing optical fiber modulator

Abstract

The embodiment of the invention discloses a 1-micron narrow-bandwidth space-time mode-locked stress sensing optical fiber modulator based on titanium carbide, and belongs to the technical field of multimode optical fibers and engineering measurement. The fiber laser comprises a 976 nanometer laser pumping source, a pumping light beam combiner, an ytterbium-doped gain multimode fiber, a polarization independent isolator, an output coupler (7: 3), a single-ring polarization controller and a titanium carbide-based saturable absorber device which are sequentially connected through multimode fibers. According to the invention, the polarization state of intracavity energy and intracavity optical signals is controlled by adjusting the polarization controller and the pumping power, the adjustment of the central wavelength under mode locking is realized in the 1 [mu] m narrow-linewidth multimode laser by using the stress microfiber, and the Q-switch mode locking and fourth-order harmonic are realized by controlling the polarization state. And the dynamic change of the cylindrical vector light beam during the mode locking period is disclosed. According to the invention, the application feasibility of stress sensing in a multimode fiber laser is verified, and meanwhile, the research in the space-time mode locking field is expanded.

Description

Technical Field

[0001] The present application relates to the field of multimode optical fiber and engineering measurement technology, and in particular to a 1um narrow bandwidth spatiotemporal mode-locked stress sensing optical fiber modulator based on titanium carbide. Background Art

[0002] In the field of sensing, fiber optic sensors have attracted much attention due to their small size, light weight, and insusceptibility to external environmental influences. Researchers have used multimode optical fibers, polarization-maintaining optical fibers, photonic crystal fibers, and tapered optical fibers to achieve wavelength switching or tuning by taking advantage of their filtering effects at low pump powers. Among them, tapered optical fibers are particularly attractive sensors due to their low cost and simple design. Various spectral switching and tuning schemes are designed by changing the propagation of the physical size mutation field of the medium in the tapered optical fiber. At the same time, the design of the fiber optic sensing scheme must also make full use of the diversity of optical signals, such as spectral shape, wavelength position, and amplitude changes. In recent years, researchers have used saturable absorbers to generate ultrashort pulses with narrow pulse width and high repetition frequency in ultrafast fiber resonant cavities, and the nonlinear effects in the cavity are used to induce various soliton morphologies in the pulses. These rich soliton phenomenon changes and switching just meet the visualization and diversification needs of fiber optic sensing. As a new type of pulse light source, time-space mode-locked fiber lasers have recently attracted extensive research. Using time-space mode-locked fiber lasers, a spectrum with a narrow bandwidth can be achieved, thereby guiding fewer frequency components, which makes it easier to show better temporal coherence and can be better used in the fields of laser sensing, laser ranging, gravitational wave detection and lidar. Therefore, the research on sensing in mode-locked fiber devices deserves in-depth discussion. Therefore, the present invention provides a fiber laser with low cost and high precision, which can be used as a laser sensing force detection means by realizing adjustable wavelength of narrow bandwidth spectrum under sensing. Summary of the invention

[0003] In order to solve the above problems in the prior art, the present invention provides a 1um narrow bandwidth spatiotemporal mode-locked stress sensing optical fiber modulator based on titanium carbide, which can adjust the curvature of the microfiber from 0mm to -1 To 0.162mm -1 At this time, the narrow bandwidth pulse wavelength can be effectively tuned to 1028.7nm-1035.2nm using a spectrometer.

[0004] A 1um narrow bandwidth space-time mode-locked stress sensing optical fiber modulator based on titanium carbide, the specific scheme is: the laser includes a 980nm pump source, a (980nm / 1000nm) wavelength division multiplexer, a first multimode optical fiber, an ytterbium-doped gain multimode optical fiber, a second multimode optical fiber, a polarization-independent isolator, a third multimode optical fiber, a stress sensing modulator, a fourth multimode optical fiber, a mode selective coupler, a polarization controller, a fifth multimode optical fiber, a titanium carbide saturable absorber, a sixth multimode optical fiber, an optical coupler, a seventh multimode optical fiber, and an eighth multimode optical fiber.

[0005] Preferably, the 980nm pump source is connected by the 980nm guidance of the pump photosynthesizer, the output end of the wavelength division multiplexer is connected to the ytterbium-doped gain multimode fiber through the first multimode optical fiber, the ytterbium-doped gain multimode optical fiber is connected to the second multimode optical fiber and connected to the polarization-independent isolator, the isolator is connected to the third multimode optical fiber and then connected to the stress sensing modulator, the rear end of the stress sensing modulator is connected to the fourth multimode optical fiber and then connected to the front end of the mode selection coupler, the rear end of the mode selection coupler is placed with a polarization controller and then connected to the front end of the titanium carbide saturable absorber through the fifth multimode optical fiber, the other end of the titanium carbide saturable absorber is connected to the rear end of the optical coupler through the sixth multimode optical fiber, the 70% signal power end of the optical coupler is connected to the 1000nm port of the wavelength division multiplexer through the eighth multimode optical fiber, and the 30% signal power end of the optical coupler is output outside the cavity through the seventh multimode optical fiber.

[0006] Preferably, the lengths of the first multimode optical fiber, the gain multimode optical fiber, the second multimode optical fiber, the third multimode optical fiber, the fourth multimode optical fiber, the fifth multimode optical fiber, the sixth multimode optical fiber, the seventh multimode optical fiber, and the eighth multimode optical fiber are 1m, 1m, 1m, 2.5m, 1.5m, 1m, 1m, 1m, and 0.5m, respectively.

[0007] Preferably, the gain optical fiber is a highly doped ytterbium-doped gain multimode optical fiber;

[0008] Preferably, the saturable absorber is a titanium carbide film;

[0009] As a part of the 1um narrow bandwidth space-time mode-locked stress sensing optical fiber modulator based on titanium carbide described in the embodiment of the present application, wherein: the output port of the output coupler has an optical power intensity ratio of 70:30, wherein 70% of the output end is connected to the cavity, and 30% of the output end is used for signal data analysis.

[0010] As a part of the 1um narrow bandwidth space-time mode-locked stress sensing optical fiber modulator based on titanium carbide described in the embodiment of the present application, wherein: the mode selective coupler is composed of a single-mode optical fiber and a 10 / 125 few-mode optical fiber to achieve coupling of the fundamental mode with a specific high-order mode.

[0011] As a part of the 1um narrow bandwidth space-time mode-locked stress sensing optical fiber modulator based on titanium carbide described in the embodiment of the present application, wherein: the polarization-independent isolator can transmit pulses unidirectionally and generate stable mode-locked pulses by adjusting the pump power to 980mW output.

[0012] As a part of the 1um narrow bandwidth space-time locked mode stress sensing optical fiber modulator based on titanium carbide described in the embodiment of the present application, microfiber is used as a stress sensing modulator, and the periodic tuning of the narrow bandwidth space-time soliton wavelength is achieved by changing the bending curvature of the microfiber.

[0013] As a part of the 1um narrow bandwidth space-time locked stress sensing optical fiber modulator based on titanium carbide described in the embodiment of the present application, the stress sensing device is composed of a tapered microfiber made by flame brush technology, and the tapered area has a length of 3.6mm and a diameter of 63um.

[0014] The beneficial effects of the present invention are as follows: (1) Based on the titanium carbide saturable absorber, the polarization controller and the pump power are adjusted to control the intracavity energy and the polarization state of the intracavity optical signal, and Q-switch mode locking and fourth-order harmonics are realized in a 1um multimode fiber ring cavity, and the dynamic changes of the cylindrical vector beam (CVB) during mode locking are revealed. (2) Using microfibers as stress sensors, by changing the power, fiber polarization state and bending curvature of the microfibers, the stress microfibers are used to achieve tuning of the central wavelength under mode locking in a 1um narrow linewidth multimode laser.

[0015] This application embodiment will play an important role in the fields of space-time mode-locked ultrashort pulse research, optical fiber sensing, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more completely understand the technical solutions and the accompanying features in the embodiments of the present application, the following is a brief introduction to the drawings required for describing the embodiments. This figure is only for further understanding of this example, and for those skilled in the art, the schematic diagram does not constitute an improper limitation of this example.

[0017] Figure 1 This is a schematic diagram of the principle structure of a 1um narrow bandwidth space-time mode-locked stress sensing optical fiber modulator based on titanium carbide provided in an embodiment of the present application;

[0018] Figure 2 This is a schematic diagram of a narrow bandwidth mode-locked spectrum of a 1um narrow bandwidth spatiotemporal mode-locked fiber laser based on titanium carbide provided in an embodiment of the present application;

[0019] Figure 3 It is a schematic diagram of 1um narrow bandwidth space-time mode-locking Q switch mode locking and fourth-order harmonic pulse and spectrum based on titanium carbide provided in an embodiment of the present application;

[0020] Figure 4 This is a dynamic change diagram of a 1um narrow bandwidth spatiotemporal mode-locked cylindrical vector beam (CVB) based on titanium carbide during mode locking provided in an embodiment of the present application;

[0021] Figure 5 This is a schematic diagram of microfiber mode analysis of a 1um narrow bandwidth spatiotemporal mode-locked stress sensing optical fiber modulator based on titanium carbide provided in an embodiment of the present application;

[0022] Figure 6 This is a schematic diagram of microfiber modulation wavelength tuning of a 1um narrow bandwidth space-time mode-locked stress sensing optical fiber modulator based on titanium carbide provided in an embodiment of the present application;

[0023] The corresponding Chinese translation of the English words in the attached figure: MMF: multimode fiber, Wavelength: wavelength, fundamental mode: fundamental mode, cladding mode: cladding mode, state: stage, Frequency: frequency, Intensity: intensity, nm: nanometer; pm: picometer, curvature: mm -1 . DETAILED DESCRIPTION

[0024] In order to make the above-mentioned objects, features and advantages of the present invention more clearly understood, the specific implementation modes of the present invention are described in detail below in conjunction with the specification and the accompanying drawings.

[0025] Obviously, many specific details are set forth in the following description in order to fully understand the purpose, features and advantages of the present invention, but the present invention can also be implemented in other ways different from those described herein, and those skilled in the art can make similar explorations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0026] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0027] The terms "first", "second", etc. are for descriptive purposes only and should not be interpreted as a measure of relative weight or as an implicit indication of other technical parameters. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features.

[0028] Example 1

[0029] Reference Figure 1, as an embodiment of the present invention, provides a 1um narrow bandwidth space-time mode-locked stress sensing optical fiber modulator based on titanium carbide, the device includes: a pump source 1, a pump photosynthetic combiner 2, an ytterbium-doped gain optical fiber 3, a polarization-independent isolator 4, a stress sensing modulator 5, a mode selective coupler 6, a polarization controller 7, a titanium carbide saturable absorber 8, and an optical coupler 9.

[0030] The 980nm pump light source 1 is connected to the pump light combiner 2 through its 980nm inlet. The output end of the pump light combiner 2 is connected to the ytterbium-doped gain multimode fiber 3 through the first multimode fiber 21. The other end of the ytterbium-doped gain multimode fiber 3 is connected to the second multimode fiber 31 and connected to the polarization-independent isolator 4. The output end of the polarization-independent isolator 4 is connected to the microfiber stress sensing modulator 5 through the third multimode fiber 41. The output end of the microfiber stress sensing modulator 5 is connected to the fourth multimode fiber 51, and the other end of the fourth multimode fiber 51 is connected to the mode selective coupler 6. The output end of the mode selective coupler 6 is connected to the polarization controller 7 through the fifth multimode fiber 61, and the output end of the polarization controller 7 is then connected to the saturable absorber 8 and input to the optical coupler 9 through the sixth multimode fiber 81. The 70% signal power output end of the optical coupler 9 is connected to the eighth optical fiber 101, and is further connected to the 1000nm input end of the wavelength division multiplexer. The 30% signal power output end of the optical coupler 9 is connected to the signal analysis spectrometer through the seventh optical fiber 91 .

[0031] The laser cavity length is 10.1 meters, the gain fiber 3 is 1 meter, and when titanium carbide is inserted into the saturable absorber 8, a stable self-starting mode-locked pulse is obtained under the condition of a pump power of 980mW. The corresponding output spectrum is Figure 2 As shown, the central wavelength is 1030.1nm and the 3dB spectral bandwidth is 250pm; Figure 2 We observed that the spectral width is extremely narrow, which is consistent with a narrow-bandwidth spatiotemporally mode-locked fiber laser.

[0032] The pump power was increased to about 910 mW, while the polarization controller was carefully adjusted to induce Q-switched pulses with a pulse period of 6.6 μs. The pump power was further increased and the polarization controller was adjusted. At a pump power of 980 mW, self-starting mode locking in the resonant cavity began, and the power was further increased. When multiple pulses interact in the resonant cavity, the pulses attract and repel each other due to factors such as gain loss, recovery dynamics, and acoustic wave effects. Increasing the pump power to 1 W and adjusting the polarization state can promote the realization of harmonic mode locking. Figure 3 shown.

[0033] The polarization controller is fine-tuned to ensure mode-locked operation, while the intensity profile at the output of the mode-selective coupler is continuously monitored using a camera to verify the stable generation of cylindrical vector light. Figure 4The LP11 mode in the fiber observed at the output of the mode selective coupler is shown. The LP11 mode consists of four eigenvector mode components: radial polarization mode (TM01), azimuthal polarization mode (TE01), and mixed polarization modes (HE21 odd mode and HE21 even mode), all of which have similar propagation constants.

[0034] The bending curvature diagram of the stress sensing modulator 5 is shown in FIG. Figure 3 As shown. In this structure, the diameter of the tapered region is significantly reduced, and an air cladding surface is formed. This design allows the fundamental mode and cladding mode to propagate simultaneously. When the fiber transitions to the air cladding, both the fundamental mode and the cladding mode are excited and eventually recombine back to the fundamental mode. The tapered fiber has the function of a fiber filter interferometer, where the filter interference phenomenon depends on the phase difference between the modes passing through the tapered fiber. -1 To 0.162mm -1 At this time, the narrow bandwidth pulse wavelength can be effectively tuned to 1028.7nm-1035.2nm using a spectrometer.

[0035] The above is a detailed introduction to a 1um narrow bandwidth space-time mode-locked stress sensing optical fiber modulator based on titanium carbide provided in an embodiment of the present application. Specific examples are used in this article to explain in detail the phenomena and implementation methods of the present application. The description of the above embodiments is only used to help understand the purpose and advantages of the present application; at the same time, for technical personnel in this field, modifications or replacements based on the scheme of the present application will cause corresponding changes in actual operation and use areas, which are all covered within the scope of the requirements of this specification.

Claims

1. A 1um narrow bandwidth spatiotemporal mode-locked stress sensing optical fiber modulator based on titanium carbide, characterized in that A 976-nanometer pump source is connected to one end of the input end of the pumped optical combiner, the output end of the pumped optical combiner is connected to one end of the ytterbium-doped gain multimode fiber, the other end of the ytterbium-doped gain multimode fiber is connected to a polarization-independent isolator, the other end of the polarization-independent isolator is connected to one end of a stress sensing modulation device, the other end of the stress sensing device is connected to a mode selective coupler, the mode selective coupler is connected to a polarization controller and then connected to a saturable absorber and outputs laser light through an output coupler.

2. The 1um narrow bandwidth spatiotemporal mode-locked stress sensing optical fiber modulator based on titanium carbide according to claim 1 is characterized in that The main cavity length of the resonant cavity is 10.1 meters. The interval between adjacent pulses observed by the oscilloscope is 49.5ns, and the interval between adjacent spectra observed by the spectrum analyzer is 20.2MHz.

3. The 1um narrow bandwidth spatiotemporal mode-locked stress sensing optical fiber modulator based on titanium carbide according to claim 1 is characterized in that , the 976-nanometer pump source outputs laser after passing through the 980 / 1000-nanometer pump photosynthesizer. The polarization-independent isolator enables the laser to be transmitted unidirectionally in the optical ring cavity, thereby increasing the service life of the fiber laser; the stress-sensing modulator affects the fiber mode by applying bending stress, thereby changing the central wavelength; the polarization controller is used to adjust the polarization state of light during laser transmission; the saturable absorber composite film uses titanium carbide as a saturable absorber to achieve mode locking; the mode selective coupler uses the LP01 mode guided by a single-mode fiber to selectively couple to the LP11 mode in the four-mode step-refractive fiber according to the phase matching condition; the saturable absorber composite film uses titanium carbide as a saturable absorber to achieve mode locking; a 70:30 fiber coupler (OC) is used to divide it into a 7:3 power optical path, and we extract 30% of the signal output outside the laser.

4. The 1um narrow bandwidth spatiotemporal mode-locked stress sensing optical fiber modulator based on titanium carbide according to claim 1 is characterized in that The laser achieves mode locking by changing the polarization state through a pump source, a titanium carbide saturable absorber and a polarization controller to obtain a narrow-bandwidth mode-locked soliton state; the pulse output is observed through an oscilloscope, and the spectral changes of the frequency domain pulse are observed through a spectrometer; the pulse repetition frequency, pulse intensity and signal-to-noise ratio are observed through a spectrum analyzer.

5. The 1um narrow bandwidth space-time mode-locked stress sensing optical fiber modulator based on titanium carbide according to claim 1 is characterized in that: The stress modulator is a conical microfiber made by flame brush technology, with a conical area length of 3.6mm and a diameter of 63um. -1 To 0.162mm -1 At this time, the narrow bandwidth pulse wavelength can be tuned to 1028.7nm-1035.2nm using a spectrometer.

6. The 1um narrow bandwidth spatiotemporal mode-locked stress sensing optical fiber modulator based on titanium carbide according to claim 1 is characterized in that ,The sensing device is located between two optical fiber fixtures. The length of the modulator sensitive section is constant. The curvature radius is deduced using the bending coupling angle to effectively quantify the bending degree of the stress sensing modulator.

7. The 1um narrow bandwidth spatiotemporal mode-locked stress sensing optical fiber modulator based on titanium carbide according to claim 1 is characterized in that , the saturable absorber of titanium carbide, 1 gram of titanium aluminum carbide (Ti 3AlC2) powder is gradually added to the hydrogen fluoride aqueous solution, and the mixture is magnetically stirred at 300 rpm for 24 hours at room temperature. Subsequently, the mixture is centrifuged at a speed of 4000 rpm, and the upper turbid suspension is discarded. The precipitate is repeatedly centrifuged and washed with deionized water until the pH value of the supernatant is close. The precipitate is dried at 60°C under vacuum conditions for 48 hours.

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