Diffused waveguides in LiNbO₃and electro-optic modulation of light in such waveguides

Abstract

Motivated also by recent revival of interest about metastable string states (as cosmic strings or in accelerator physics), we study the decay, in presence of dimensional compactification, of a particular superstring state, which was proven to be remarkably longlived in the flat uncompactified scenario. We compute the decay rate by an exact numerical evaluation of the imaginary part of the one-loop propagator. For large radii of compactification, the result tends to the fully uncompactified one (lifetime T ≡ const. g −2 s M 5 ), as expected, the string mainly decaying by massless radiation. For small radii, the features of the decay (emitted states, initial mass dependence, . . . ) change, depending on how the string wraps on the compact dimensions.