Multi-pass mini-slab (MPMS) Nd:YAG ceramic lasers with a single-mode output of 38 W is examined corresponding to an optical conversion efficiency of 47%. Although several characteristics of various ceramic samples are almost similar, such as transmission, emission and absorption spectra, cross section, and thermal conductivity, their optical conversion efficiencies can vary from 5% to 40%. We present a simple technique to on-line measure the influence of scattering loss of ceramic on laser perfo
