Microstructured single-mode lightguides based on the phenomenon of differential mode damping

This paper discusses the modal composition of radiation that propagates along microstructured lightguides with a large-diameter core and a special cladding structure. It is shown that all the designs of optical fibers represented here (lightguides with a displaced core, with a cyclic system of apertures, with C-3 nu symmetry) are distinguished from their traditional counterpart by increased stability of the fundamental mode against bending of the lightguide. The single-mode light-propagation regime is achieved in practice in the indicated structures by making the damping coefficients of the fundamental mode and the higher modes substantially different. It is experimentally established that the main advantage of lightguide structures that combine a large core diameter (20-40 mu m) with an increased amount of air contained in the cladding is an extended working spectral range. (C) 2012 Optical Society of America.