Concave refractive index optical fiber for shaping Gaussian beam into flat-topped beam

Abstract

The invention discloses a concave refractive index optical fiber for shaping a Gaussian beam into a flat-topped beam, and belongs to the field of laser beam shaping. The concave refractive index optical fiber for shaping the Gaussian beam into the flat-topped beam can shape the Gaussian beam into the flat-topped beam and comprises a fiber core and a cladding, the fiber core is arranged in the cladding, and the refractive index of the fiber core is larger than that of the cladding; the refractive index of the fiber core is concave refractive index structure distribution; and the concave refractive index structure distribution satisfies the following functional relationship: n<core>=ns*sqrt(1+2delta*(r / a)<2>), wherein n<core> is the refractive index distribution of the fiber core area, ns isthe refractive index value of the lowest concave point of the fiber core area, r is the radial variable of the fiber core under polar coordinates, a is the radius of the fiber core of the optical fiber, the relative refractive index difference delta is equal to (n2<2>-ns<2>) / 2 / ns<2>, wherein n2 is the maximum refractive index value of the fiber core area. The concave refractive index optical fiber has the advantages of being simple and stable in structure, easy to manufacture, convenient to use, low in cost, good in shaping effect, adjustable, capable of reducing light intensity, convenient to combine with an optical system and the like.

Description

technical field [0001] The invention designs a concave refractive index optical fiber for shaping a Gaussian beam into a flat-top beam, and belongs to the field of laser beam shaping. Background technique [0002] Flat-hat beam refers to the beam whose light intensity is uniformly distributed in the cross-section of the beam transmission direction. Due to the uniform energy distribution, it has important applications in the fields of display, holography, laser processing, and laser medical treatment. Since the light intensity of the laser beam generally obeys the Gaussian distribution, it is necessary to shape the Gaussian beam in order to obtain a flat-hat beam with good uniformity. In 1994, Gori et al. proposed another model called flat Gaussian beam, whose mode field can be described as a superposition of finite Laguerre-Gaussian modes or Hermitian-Gaussian modes; Li also proposed a new The theoretical model is used to describe circular or non-circular flat-hat beams, an...

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Problems solved by technology

For graded fiber, the refractive index from the center of the fiber core to the cladding is gradually reduced, which can make the light of the high-order mode propagate in a sinusoidal form, reduce inter-mode dispersion, increase the fiber width, and increase the transmission distance, but its cost is higher. , the current multimode fiber is mostly graded fiber, its cladding refractive index is uniform, the central refractive index of the fiber core is the largest, and gradually decreases along the direction of the core radius

[0007] However, neither of the above two forms of fiber can shape a Gaussian beam into a flat-hat beam.

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