Frequency doubling of He-Ne laser radiation at 632.8 nm

Second harmonic generation (SHG) obtained using a potassium dihydrogen phosphate (KDP) nonlinear crystal from a CW He-Ne laser as a pump source, which emits at 632.8 nm, is reported. The SHG efficiency at the power of the He-Ne laser utilized (18 mW) and the fundamental beam waist available (0.1 mm), was evaluated theoretically; the same efficiency was measured experimentally obtaining a value of (3.7-0.1)×10-7, in good agreement with theoretical predictions.