Polarization-maintaining all-fiber mode-locked laser with low repetition frequency

Abstract

The invention discloses a polarization-maintaining all-fiber mode-locked laser with the low repetition frequency. An optical fiber type semiconductor saturable absorption mirror, a polarization-maintaining optical fiber mode field adapter, a polarization-maintaining single mode optical fiber, a polarization-maintaining optical fiber wavelength division multiplexer, a polarization-maintaining ytterbium-doped gain optical fiber and a polarization-maintaining optical fiber grating are connected in sequence in the optical transmission direction. A pump optical transmission optical fiber is connected with the input end of the polarization-maintaining optical fiber wavelength division multiplexer, wherein the input end is located on one side of the polarization-maintaining ytterbium-doped gain optical fiber. The polarization-maintaining all-fiber mode-locked laser with the low repetition frequency is based on the semiconductor saturable absorption mirror, the optical fiber type semiconductor saturable absorption mirror and the polarization-maintaining optical fiber grating form a linear cavity structure, stable mode locking automatic start is achieved, unstable mode locking caused by external slight vibration cannot occur, the all-fiber structure is achieved, integration is easy, all optical fiber devices of the laser adopt polarization-maintaining optical fiber splicing, it is ensured that the laser can output linear polarized light, and the polarization-maintaining all-fiber mode-locked laser with the low repetition frequency is simple and compact in structure, and good in mode locking stability.

Description

technical field [0001] The invention relates to the preparation technology of an optical fiber mode-locked laser, in particular to a low repetition frequency polarization-maintaining all-optical fiber mode-locked laser. Background technique [0002] All-fiber mode-locked lasers are widely used in the fields of ultrafast optics, nonlinear optics, laser ranging and laser cold processing. The ultrashort pulse seed source has very important significance. [0003] In order to obtain high pulse energy, Q-switched lasers with low repetition rate or mode-locked lasers with high repetition rate (10-100MHz) and low pulse energy are usually used. The latter requires additional power amplification to increase pulse energy, and the coexistence of Q-switching and mode-locking The method also produces too high pulse energy; another way to increase the pulse energy is the cavity emptying technology. The cavity emptying technology is composed of a reflective cavity and a cavity emptying dev...

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Problems solved by technology

[0006] Literature [see Lian, et al., Low repetition-rate All-normal-Dispersion mode locking Laser Based on SESAM.ICEEOE2011.C0706] used the linear cavity all-fiber structure to realize the mode locking of the laser by using SESAM, but due to the fiber type The mode field area of ​​the spot on SESAM is small, and the surface energy density is too high, which leads to the unstable mode locking of the laser, and the situation of multi-pulse mode locking occurs.

[0007] In order to solve the above problems, SESAM can be coupled with an optical fiber with a core diameter greater than 6 microns (such as an optical fiber with a core diameter of 10 microns), which can reduce the energy density on the surface of the SESAM. They are all made of fibers with a core diameter of 6 microns, so if the core diameter of the SESAM coupled fiber is greater than 6 microns, the mode-locked pulse will lose most of its energy during the propagation from the thick fiber to the thin fiber. A very high energy loss is generated in the laser, which affects the stable mode-locking start of the laser. At this time, it is necessary to match the mode field area of ​​fibers with different core diameters. However, there is currently no mode field adapter product made of polarization-maintaining fibers in the domestic market.

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