Reflection and transmission of waves in surface-disordered waveguides

The reflection and transmission amplitudes of waves in disordered multimode waveguides are studied by means of numerical simulations based on the inva riant embedding equations. In particular, we analyze the influence of surfa ce-type disorder on the behavior of the ensemble average and fluctuations o f the reflection and transmission coefficients, reflectance, transmittance, and conductance. Our results show anomalous effects stemming from the comb ination of mode dispersion and rough-surface scattering. For a given wavegu ide length, the larger the mode transverse momentum is, the more strongly i s the mode scattered. These effects manifest themselves in the mode selecti vity of the transmission coefficients, anomalous backscattering enhancement , and speckle pattern both in reflection and transmission, reflectance and transmittance, and also in the conductance and its universal fluctuations. It is shown that, in contrast to volume impurities, surface scattering in q uasi-one-dimensional structures (waveguides) gives rise to the coexistence of the ballistic, diffusive, and localized regimes within the same sample. [S0163-1829(99)09103-1].