Laser amplification optical fiber for preventing self-convergence damage

Abstract

The invention relates to the technical field of optical fiber laser transmission, and in particular relates to a laser amplification optical fiber for preventing self-convergence damage, which comprises a hollow optical fiber and a gain optical fiber, wherein the rear end of the gain optical fiber is connected with the hollow optical fiber along the laser transmission direction. The gain optical fiber is connected with the hollow optical fiber so as to prevent optical fiber damage caused by optical field convergence due to a self-convergence effect generated during the process of transmitting, amplifying and oscillating the gain optical fiber, so that single fiber power amplification limit performance of the gain optical fiber is improved, and the obtained pulse energy is greatly improved.

Description

technical field [0001] The invention relates to the technical field of optical fiber laser transmission amplification, in particular to a laser amplifying optical fiber that prevents self-focusing damage. Background technique [0002] In the rare earth doped laser gain fiber medium, when the laser intensity exceeds a certain level, the Kerr effect in the medium will be induced, that is, the refractive index of the medium is linearly related to the light intensity, and the linear proportional coefficient is represented by the nonlinear refractive index coefficient . Since the fundamental mode light field distribution (approximately Gaussian distribution) is usually used in practical applications, in materials with a positive nonlinear refractive index coefficient, the refraction index experienced by the region with strong central light intensity is relatively large, and the refraction experienced by the surrounding areas with low light intensity When the convergence effect e...

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Problems solved by technology

Since the fundamental mode light field distribution (approximately Gaussian distribution) is usually used in practical applications, in materials with a positive nonlinear refractive index coefficient, the refraction index experienced by the region with strong central light intensity is relatively large, and the refraction experienced by the surrounding areas with low light intensity When the convergence effect exceeds the diffraction effect of the beam, self-focusing occurs, resulting in a large light intensity at the focal point, which induces photodamage of the material

For fused silica material, for 1 micron laser wavelength, the self-focusing threshold obtained by its typical nonlinear refractive index coefficient is about 4.3MW. In the fiber waveguide structure, although the refractive index guide will have a certain impact on the beam transmission, However, both numerical simulation and experimental results show that the self-focusing threshold power of the optical fiber is basically the same as that of the fused silica bulk material, which limits the pulse energy of at most 43mJ within 10ns pulse width in the fiber laser amplifier, compared with the solid-state laser There is still a considerable gap in the pulse peak power and energy that the system can obtain

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