Loss analysis of air-core photonic crystal fibers

Recently the use of Bragg ref lection to conf ine light in an air-core f iber has attracted considerable attention. Some advantages of air-core f ibers are their potential to achieve propagation losses of less than 0.2 dBkm (the current value of telecommunication f ibers) and to greatly increase the power threshold for the onset of nonlinear effects. The air-core f ibers considered in the literature can be generally classif ied into two types: photonic crystal f ibers (PCFs) and Bragg fibers. Some important advantages of PCFs are the excellent material properties of the silica glass and the compatibility of PCFs with the current optical f iber manufacturing technologies. Yet Bragg ref lection in an air-core PCF with a f inite number of cladding air holes always leads to some radiation leakage of light from the f iber core, which is diff icult to calculate owing to the structural complexity of the PCF. The method of plane-wave expansion in a supercell, because of an artif icially imposed periodic boundary condition, cannot give the propagation loss. Many other numerical approaches do not have the numerical precision to resolve propagation loss of the order of decibels per kilometer or less. In this Letter we use newly developed multipole moment approach to analyze the modal loss of an aircore PCF.

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