Step-index profile

About: Step-index profile is a research topic. Over the lifetime, 3104 publications have been published within this topic receiving 53199 citations.

Coupling of a laser diode to single mode circular core graded index fiber via hyperbolic microlens on the fiber tip and identification of the suitable refractive index profile with consideration for possible misalignments

Abstract: With an aim to explore the suitable refractive index profile for maximum coupling, we present a theoretical investigation of coupling optics involving a laser diode and single mode circular core graded index fiber via a hyperbolic microlens on the fiber tip in absence and presence of any possible transverse and angular misalignments. By employing Gaussian field distributions for both the source and the fiber and also ABCD matrix for hyperbolic microlens under paraxial approximation, we formulate analytical expressions for the concerned coupling efficiencies. The investigations are performed for two different light-emitting wavelengths of 1.3 and 1.5 μm for such fibers with different profile exponents in refractive index profile. Further, it is observed that out of the studied refractive index profiles, the triangular index profile having the dispersion-shifted merit comes out to be the most suitable profile to couple laser diode to single mode circular core graded index fiber for two wavelengths of practical interest. The analysis should find use in ongoing investigations for optimum launch optics for the design of hyperbolic microlens either directly on the graded index circular core single mode fiber tip or such fiber attached to single mode fiber to achieve a long working distance.

Optimization of Sensors Based on Multimode Interference in Single-Mode–Multimode–Single-Mode Structure

Abstract: By coating a single-mode-multimode-single-mode (SMS) structure with a complex refractive index thin-film the central wavelength of the transmission and attenuation bands of the optical spectrum can be shifted. By adequate selection of multimode segment length and diameter, the thin-film thickness and the thin-film refractive index, the sensitivity of the device to the surrounding medium refractive index, the thickness of the thin-film or the refractive index of the thin-film can be optimized. Experimental results are corroborated numerically with the transfer matrix method.

Mode-field converters and long-period gratings fabricated by thermo-diffusion in nitrogen-doped silica-core fibers

Abstract: Summary form only given Novel nitrogen-doped silica-core pure-silica-cladding fibers provide exceptional possibilities to achieve abrupt variations of the refractive-index profile by thermo-diffusion of nitrogen A high diffusion coefficient of nitrogen in silica makes it possible to create deep changes in refractive index by means of short-time heat action on a fiber section with a length comparable to the fiber diameter Thus, N-doped silica fibers are most appropriate for various fiber-optic devices produced by thermo-diffusion

A yttrium aluminosilicate glass fiber with graded refractive index fabricated by melt-in-tube method

Abstract: A graded-index fiber with yttrium aluminosilicate (YAS) glass core was fabricated by a “Melt-in-Tube” method. The refractive index and stress profiles of the fibers exhibit a highly symmetrical gradient tendency along the radial axis which is in accordance with the results of element migration. Based on the formation mechanism of YAS glass core, the relationships between the refractive index/stress profile and the spontaneous migration are discussed. A linear all-fiber laser based on the obtained fiber shows a laser output threshold of 11.48 mW and slope efficiency of 8.3%. The near-field beam intensity distribution of fiber laser with spectrum FWHM of 0.24nm indicates the good laser beam quality. The facile “Melt-in-tube” method was proved to be reliable in designing graded-index fiber through the dissolution and diffusion process, which is more advanced than commonly used “Rod-in-tube” method. This article is protected by copyright. All rights reserved.