Micro-tapered fiber for producing ultra-narrow linewidth fiber laser, and laser

Abstract

The invention relates to a micro-tapered fiber for producing an ultra-narrow linewidth fiber laser. The micro-tapered fiber is produced by ordinary single-mode fibers through a tapering process. A plurality of tapering regions are formed on the ordinary single-mode fibers through multiple tapering operations, and the whole micro-tapered fiber is connected into the laser, so that the length of a resonant cavity of the laser is more than or equal to 80m; the tapering regions on the ordinary single-mode fibers can effectively suppress the Brillouin gain and ensure the stability of single-frequency operation of the laser, and meanwhile, the large-length resonant cavity can meet the requirement of vast accumulation of Rayleigh gain and improve the signal strength. The micro-tapered fiber provided by the invention has the beneficial technical effects that the single-frequency operation of the laser is ensured, and meanwhile, the accumulation of Rayleigh gain can be effectively realized, and the output signal strength is improved; the tuning range is unrelated to the matching of the pumping wavelength and the length of the laser cavity, and additional linewidth compression is not needed; and the structure is simple, the implementation is easy, and the fiber is a novel narrow-linewidth light source.

Description

technical field [0001] The invention relates to a laser, in particular to a micro tapered optical fiber and a laser for making an ultra-narrow linewidth fiber laser. Background technique [0002] Ultra-narrow linewidth fiber laser has become an important development direction of fiber lasers due to its unique low phase noise characteristics. It is widely used in distributed fiber optic sensing and interferometric fiber sensing systems to reduce noise and improve detection sensitivity. . [0003] At present, the methods for realizing single-frequency narrow linewidth output of fiber laser mainly include short-cavity method, ring-cavity method and stimulated scattering fiber laser. Among them, the short-cavity method generally uses an erbium-doped fiber with a length of several centimeters as the gain medium, and a narrow linewidth fiber grating as the laser cavity mirror. Although its structure is simple, it is very difficult to implement. First, the erbium-doped fiber ...

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Problems solved by technology

Among them, the short-cavity method generally uses an erbium-doped fiber with a length of several centimeters as the gain medium, and a narrow linewidth fiber grating as the laser cavity mirror. Although its structure is simple, it is very difficult to implement. First, the erbium-doped fiber The length of the fiber is very short, and its doping concentration is difficult to control. If the doping concentration is too low, the gain generated by the fiber is far from the gain required by the laser. If the doping concentration is too high, it is prone to quenching. In addition, the short cavity The method also requires the 3dB bandwidth of the fiber grating to be less than 0.03nm, which puts forward higher requirements on the processing technology of the fiber grating, and it is difficult to realize

When the ring cavity method is used, the output efficiency of the laser is low. In the prior art, the method of increasing the length of the doped fiber is used to increase the output power, but at the same time, the frequency stability of the laser is reduced.

The fiber laser based on Brillouin scattering has a frequency shift of 11GHz in its output laser, and because the Brillouin gain bandwidth in the fiber is wide (about 20MHz), the fiber cannot be too long, so as not to be in the range of the Brillouin gain spectrum (20MHz ) There are multiple laser modes in the cavity, which finally forms a random mode hopping phenomenon, and cannot achieve stable single-frequency operation. At the same time, due to the limitation of the length of the optical fiber, it is not easy to form gain accumulation in the resonator, and the signal is weak, which is not conducive to application.

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