High double-refraction photonic crystal fiber (PCF)

Abstract

The invention discloses a high double-refraction photonic crystal fiber (PCF) comprising a fiber core and a cladding. Two small air holes are removed from the central part of an optical fiber so that an ellipse-like fiber core is formed; meanwhile, the structural arrangement of the air holes of the cladding is changed, and four pairs of large air holes and a pair of elliptic air holes are introduced to the cladding and connected to the fiber core, so that the optical fiber with the structure has double rotation symmetry, a cross-polarization mode is not degenerated again, and very high double-refraction is shown. Through changing the structure of the fiber core and adjusting the diameters of the large air holes and the ellipticities of the elliptic air holes within a certain range, the PCF is two orders of magnitudes higher than a common optical fiber due to the adoption of the mode of double refraction, and meanwhile, the optical fiber has a high nonlinear coefficient. The PCF provided by the invention has the advantages of simple structure, high double-refraction and high nonlinearity. The PCF with the structure can be used for manufacturing a polarization-preserving optical fiber and relevant optical fiber devices with proper nonlinearity or polarization characteristics.

Description

technical field [0001] The invention belongs to the field of optical fiber technology, in particular to a photonic crystal optical fiber. Background technique [0002] In an ideal situation, a single-mode fiber transmits two mutually orthogonal modes, which have the same propagation constant and are degenerate with each other, so they can be regarded as a single polarization electric vector. However, the actual optical fiber is somewhat imperfect, and the internal refractive index distribution is also uneven due to the uneven internal stress. This causes the change of the propagation constants of the two fundamental modes, which leads to the disturbance of the polarization state of the fundamental mode in the single-mode fiber, destroys the mutual degeneracy of the fundamental modes, and thus causes the mode birefringence. The polarization-maintaining fiber artificially introduces geometric anisotropy in the cross-section of the fiber, which reduces the coupling coefficient...

AI Technical Summary

Problems solved by technology

[0004] In order to overcome the deficiency of low birefringence in the prior art, the present invention proposes a simple and easy-to-fabricate photonic crystal fiber structure with high birefringence characteristics. The structure itself has double rotational symmetry, and can obtain Birefringent photonic crystal fiber has higher birefringence and higher nonlinear coefficient

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