Theoretical and Experimental Studies on Laser Beam Harmonic Production using Solid State Nonlinear Crystals

There is a real demand for a high power UV laser due to its applications in science and technology. Very few lasers are found in this region. The question of how to produce such an effective laser is to be solved. The answer regarding this problem is the nonlinear optical frequency mixing. This process is not efficient in producing higher harmonics. In the present work, for the first time, a model for producing harmonics based on cascading process is suggested. Theoretical relations are derived for the efficiency evaluation and optimization for the generation of second harmonic and its consequence cascading to produce the third, fourth and fifth harmonics. These relations can be applied to a wide class of nonlinear optical materials that meet the prerequisite of the process. Calculations are made for KTP and borate crystals for Nd-YAG laser with 1.064 m wavelength. Our model is tested experimentally where a case study is carried out. The case study involved producing the fourth harmonics at 250 nm in the absence of the fundamental beam. Experimental setup is configured involving a high power diode laser as pump source and a Nd- KTP crystal chip. A second harmonic is obtained with this set-up. The second harmonic beam in this work is fed to a borate crystal configured and placed in a calculated position. The experimental results obtained with this set- up, are consistent with the prediction of the theoretical work for the fourth harmonic. (Author)