Leaky-mode Loss Research Articles

Radiating leaky-mode losses in single-mode lightguides with depressed-index claddings

Cutoff characteristics are calculated for the fundamental mode in a single-mode double-clad lightguide structure whose refractive index in the inner cladding is less than the index of the outer cladding. Results of this study indicate how to choose the proper depressed cladding width and depth in order to reduce long-wavelength losses that have been observed in experimental MCVD fibers with fluorine-doped phosphosilicate claddings.

Radiating Leaky-Mode Losses in Single-Mode Lightguides with Depressed-Index Claddings

Cutoff characteristics are calculated for the fundamental mode in a single-mode double-clad lightguide structure whose refractive index in the inner cladding is less than the index of the outer cladding. Results of this study indicate how to choose the proper depressed cladding width, depth in order to reduce long-wavelength losses that have been observed in experimental MCVD fibers with fluorine-doped phosphosilicate claddings.

Generalized WKB method for the analysis of light propagation in inhomogeneous anisotropic optical waveguides

The generalization of the WKB method for light propagation in planar uniaxially anisotropic inhomogeneous optical waveguides is presented. Both ordinary and extraordinary ray paths and phases along the rays in the medium inhomogeneous in the direction perpendicular to the optic axis are derived. These results are used to formulate the dispersion equations for graded-index anisotropic optical waveguides such as the LiNbO 3 :Ti waveguide. Analytical continuation from the real to the complex effective index of refraction enables one to include leaky modes into the analysis. A simple expression for the leaky-mode loss coefficient is given. Both the polarization conversion and energy leakage effects are well described by this method.

Comments on "Approximate calculation of leaky-mode loss coefficients for Ti-diffused LiNbO3waveguides"

The discrepancy between the results of geometric-optical [1] and WKB [3] analyses of the leaky-mode loss coefficient of LiNbO 3 :Ti anisotropic waveguide is discussed. It is shown that both methods, if correctly formulated, give essentially identical results.

Correction to "Approximate calculation of leaky-mode loss coefficients for Ti-diffused LiNbO3waveguides"

Correction to "Approximate calculation of leaky-mode loss coefficients for Ti-diffused LiNbO₃waveguides"

Effects of anisotropic and curvature losses on the operation of geodesic lenses in Ti:LiNbO_3 waveguides

The effects of curvature and anisotropy (leaky-mode) losses on the performance of geodesic lenses in Ti-diffused waveguides in LiNbO(3) are examined. A model for the lenses is developed that is equivalent to the usual Fraunhofer diffraction theory, modified to account for the path-dependent losses. Numerical calculations show that the curvature losses are dominant and require fabrication of waveguides having well-confined fundamental modes. Higher-order modes are effectively attenuated by the lenses. The leaky-mode losses have the beneficial effect of reducing the side-lobe intensity in the focal plane.

Approximate calculation of leaky-mode loss coefficients for Ti-diffused LiNbO3waveguides

A hybrid-mode model is developed which allows analytical calculation of the leaky-mode loss coefficient in Ti-diffused LiNbO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> waveguides. Field representations correspond to the approximation of geometrical optics. Hybrid-mode effective indexes are approximated utilizing the known anisotropy of LiNbO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> . For <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">X</tex> - or <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Y</tex> -cut waveguides the leaky mode is shown to be an extraordinary-like hybrid mode with a small ordinary field component which arises from extraordinary to ordinary power conversion at the abrupt index boundary. This ordinary index component is not bound by the graded index boundary, giving rise to the power loss. The theoretical dependence of the loss coefficient on propagation direction is in agreement with experiment.

Hollow dielectric waveguide for distributed feedback lasers

Hollow dielectric waveguides with gas-filled core and a dielectric tube seem promising as laser structures. The tube fulfills the dual role of a guidance structure for the electromagnetic radiation as well as that of a container for the plasma of the gas laser. Feedback for laser oscillation is achieved by providing coupling between forward- and backward-traveling modes by means of periodic ripples of the inner surface of the hollow dielectric tube. This paper is devoted to the derivation of the coupling coefficients between two guided modes that are coupled by ripples in the tube wall. The calculation is based on the model of a slab waveguide. Expressions for the leaky-mode losses and the scattering losses inevitably introduced by the coupling mechanism are also presented.