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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.


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Journal ArticleDOI
TL;DR: In this paper, the spontaneous emission spectrum is converted to a gain spectrum from which changes in the imaginary part of the refractive index can be calculated as the laser is excited from low current up to threshold.
Abstract: The refractive index change caused by changes in the absorption edge of GaAs is determined by analysis of the spontaneous emission spectrum of a buried heterostructure window laser. The spontaneous emission spectrum is converted to a gain spectrum from which changes in the imaginary part of the refractive index can be calculated as the laser is excited from low current up to threshold. The real change in refractive index is then determined by a Kramers‐Kronig transformation. The change in refractive index n′ of the GaAs active layer is slightly sublinear with minority carrier density nc. At the laser line, including the calculated contribution of free carriers, Δn′ = −0.025±0.005 and dn′/dnc = −(1.8±0.4)×10−20 cm3 in lasers with carrier densities at threshold estimated as 1.02×1018 cm−3. Near threshold, the ratio of the change in the real index to the change in the imaginary index is about 6.2.

311 citations

Journal ArticleDOI
TL;DR: In this article, a simple method is presented for finding the modes on those optical waveguides with a cladding refractive index that differs only slightly from the core, and the resulting modal fields and their progagation constants display the polarization properties of the waveguide contained within the ∇ ∊ term of the vector wave equation.
Abstract: A simple method is presented for finding the modes on those optical waveguides with a cladding refractive index that differs only slightly from the refractive index of the core. The method applies to waveguides of arbitrary refractive index profile, arbitrary number of propagating modes, and arbitrary cross section. The resulting modal fields and their progagation constants display the polarization properties of the waveguide contained within the ∇ ∊ term of the vector wave equation. Examples include modes on waveguides with circular symmetry and waveguides with two preferred axes of symmetry, e.g., an elliptical core. Only a minute amount of eccentricity is necessary for the well-known LP modes to be stable on an elliptical core, while the circle modes couple power among themselves.

285 citations

Journal ArticleDOI
TL;DR: It is shown that appropriate placing of optically pumped laser dyes (gain) into the metamaterial structure results in a frequency band where the nonbianisotropic meetamaterial becomes amplifying and the figure of merit diverges at two distinct frequency points.
Abstract: On the basis of a full-vectorial three-dimensional Maxwell-Bloch approach we investigate the possibility of using gain to overcome losses in a negative refractive index fishnet metamaterial. We show that appropriate placing of optically pumped laser dyes (gain) into the metamaterial structure results in a frequency band where the nonbianisotropic metamaterial becomes amplifying. In that region both the real and the imaginary part of the effective refractive index become simultaneously negative and the figure of merit diverges at two distinct frequency points.

270 citations

Journal ArticleDOI
TL;DR: The numerical and experimental investigation of the cladding modes re-organization in high refractive index (HRI) coated Long Period Gratings (LPGs) is reported, leading to relevant improvements in the SRI sensitivity in terms of wavelength shift and amplitude variations of the LPGs attenuation bands.
Abstract: In this work, the numerical and experimental investigation of the cladding modes re-organization in high refractive index (HRI) coated Long Period Gratings (LPGs) is reported. Moreover, the effects of the cladding modes re-organization on the sensitivity to the surrounding medium refractive index (SRI) have been outlined. When azimuthally symmetric nano-scale HRI coatings are deposited along LPGs devices, a significant modification of the cladding modes distribution occurs, depending on the layer features (refractive index and thickness) and on the SRI. In particular, if layer parameters are properly chosen, the transition of the lowest order cladding mode into an overlay mode occurs. As a consequence, a cladding modes re-organization can be observed leading to relevant improvements in the SRI sensitivity in terms of wavelength shift and amplitude variations of the LPGs attenuation bands.

253 citations

Journal ArticleDOI
D. Gloge1
TL;DR: Optical signals transmitted through cladded glass fibers are subject to delay distortion because of dispersion in the material, dispersion caused by the waveguide characteristic, and delay differences between modes.
Abstract: Optical signals transmitted through cladded glass fibers are subject to delay distortion because of (1) dispersion in the material, (2) dispersion caused by the waveguide characteristic, and (3) delay differences between modes. We isolate these effects and evaluate their significance for cases of practical interest. These concern fibers in which the refractive index of the cladding is only slightly lower than that of the core.

252 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202318
202236
20219
202011
201913
201814