BBO crystals were grown by the top-seeded solution growth technique from a Na2-O melt-solution. Optimization of heating conditions and technological growth parameters allowed us to produce high-quality optic crystals. Their main morphological feature is the facing of a boule side surface. The area of hexagonal prism face {1120} can reach several square centimeters. Non-linear-optical elements which are produced from a crystal with well arranged faces have higher coefficients of laser radiation frequency conversion.
The BBO crystals were studied for linear and non-linear absorption. Linear absorption was measured with conventional spectroscopic method. The analysis of supplementary absorption spectra and thermally- stimulated luminescence behavior allowed us to suggest that Na atoms are a main spontaneous impurity in BBO crystals providing supplementary absorption in UV-region. We used the 4th and 5th harmonics of Nd-YAG laser to measure the non-linear absorption.
The selected optimized crystals were used in various optical schemes up to the 5th harmonic generation. Harmonic generation was studied by high performance original Nd-YAG laser (SLM-operation, D. L. output beam up to 100 Hz repetition rate, 1.8 ns pulse duration, 16 W output). Harmonic efficiency values are listed below. Several optical schemes for harmonic generation are discussed.
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