In a solid state, optically end-pumped laser, the laser gain medium has a
tapered diameter to minimize the maximum path length of barrelling
amplified stimulated emission (ASE), and a roughened surface region at
one end to scatter barrelling ASE out of the gain medium; thereby
minimizing the negative effective of barrelling ASE's, and inhibiting the
trapping of rays with a large longitudinal component, but disallowing a
cyclic, i.e. repeated, pass path with specular reflections.