Rigorous analysis of dielectric rod waveguides with flat cross-section

The mode-matching method is applied to the rigorous investigation of propagation characteristics of rod waveguides, such as an elliptically cored optical fibre or a rectangular waveguide with a flat cross-section, whose accurate analysis has been difficult so far. A high accuracy, to five significant figures, is achieved for the normalised propagation constant. Field distributions in several hybrid modes, as well as dispersion relations, are detailed. It is also confirmed that the hybrid mode analysis is not always necessary in the case of flat cross-section. The properties of higher-order mode cutoff and polarisation preservation in an elliptically cored fibre, whose investigation has not been always sufficient, are discussed more accurately. Through these analyses, it is also confirmed that the mode matching method is still a useful and reliable numerical method for rigorous analysis of the rodtype dielectric waveguide with an arbitrarily shaped cross-section