The Beamlet laser is a full-scale, single-aperture scientific prototype of the frequency-tripled Nd:glass laser for the proposed National Ignition Facility. At aperture sizes of 30 cm x 30 cm and 34 cm x 34 cm using potassium dihydrogen phosphate crystals of 32 cm x 32 cm and 37 cm x 37 cm, respectively, the authors have obtained up to 8.3 kJ of third harmonic energy at 70%--80% whole beam conversion efficiency
