A laser amplifier includes a laser active slab with a source of pump power to amplify an input laser beam, the laser active slab including a block of laser active material having opposed lateral faces defining a wedge lateral dihedral angle specified to minimize parasitic amplified spontaneous emission. The laser amplifier may include one or more external mirrors highly reflecting at the lasing wavelength positioned and oriented to provide for zig-zag passes through the gain sheet for the input laser beam to yield a multi-pass-amplified laser beam. The source of pump power may be one or more laser diode bars and microlenses producing a gain sheet in the laser active slab.