A slab laser amplifier with parasitic oscillation suppression has a plurality of angled pump faces related to one another in order to decrease likelihood of parasitic oscillations, with internal beam incidence angles at total internal reflection that alleviate need for reflective coatings. No polished surfaces of gain material comprising the amplifier are parallel to one another. A beam path within the gain material is such that all incident angles of the beam path upon the two main faces and the common end face are greater than a critical angle required for total internal reflection, thereby alleviating need for reflective coatings. Based on an index of refraction of the gain material, and based on a diameter of the laser beam, dimensions of the gain material are selected to maximize beam overlap in a pumped volume of the gain material.