TY - JOUR N2 - It is widely accepted that, on ensemble average, the transmission T of guided modes decays exponentially with the waveguide length L due to small imperfections, leading to the important figure of merit defined as the attenuation-rate coefficient alpha = -< ln(T)>/L. In this Letter, we evidence that the exponential-damping law is not valid in general for periodic monomode waveguides, especially as the group velocity decreases. This result, that contradicts common beliefs and experimental practices aiming at measuring alpha, is supported by a theoretical study of light transport in the limit of very small imperfections, and by numerical results obtained for two waveguide geometries that offer contrasted damping behaviors. KW - SLOW LIGHT KW - DISORDER A1 - Baron, A A1 - Mazoyer, S A1 - Smigaj, W A1 - Lalanne, P SN - 0031-9007 IS - 15 AV - public Y1 - 2011/10/05/ UR - http://dx.doi.org/10.1103/PhysRevLett.107.153901 ID - discovery1338436 N1 - © 2011 American Physical Society TI - Attenuation Coefficient of Single-Mode Periodic Waveguides VL - 107 JF - PHYS REV LETT PB - AMER PHYSICAL SOC ER -