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Minimization of Bending Loss in Materials for Integrated Optics
Mohammad Omari, Abdullah Ijjeh and Idrees S. Al-Kofahi

Materials for integrated optics are glasses, electro-optical crystals or some materials with nonlinear properties. Compared with fiber optics communication lines, integrated optics devices are short so which results in a reduction in the energy losses in direct waveguides. The high level of integration results in very sharp bending of the waveguides. Therefore, bending losses become the dominant ones. In the case of so called pure bending loss, which is the tunneling of the modal field to a propagation region outside the bend, the usual measures against this power transfer are offsetting, coherent coupling and the phase front acceleration. No one of them is perfect, but the last one could be the best. The difficulties in implementation of this method are high gradients in the index of refraction and very thin layers of gradient optics elements which are necessary for the wave front correction.We propose a simple technological solution which can help to reach minimum possible bending loss with relatively small gradient of the refraction index. The calculated optimized gradient is applied to the whole set of parallel waveguides in the bending instead of the individual phase front correction in every waveguide. The second half of the bending loss problem is the transient loss caused by radiation modes excited by sharp changes in the radius of curvature. For this case the best configuration of the waveguide bending is proposed and compared with other configurations. In both cases the theoretical minimum of the bending loss is defined.

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