Impact of BaB2O4 growth method on frequency conversion to the deep ultra-violet

• For deep UV λ < 260 nm barium borate β-BBO is major optical non linear material.
• A high purity β-BBO crystals are grown, by Czochralsky technics in a supercool melt.
• At low power incident intensity, both materials have similar efficiency.
• At high power intensity the Czochralski BBO presents 40% more efficiency.
• The temperature dependance of the output power is connected to the non linear absorption.

In this article, we report how the growth method used for barium beta-borate β-BaB2O4 (BBO) impacts its high power second harmonic generation properties in the deep-UV. We compared a BBO crystal grown by flux (Top Seeded Solution Growth or TSSG) and a BBO crystal grown by the Czochralski (CZ) method. We first characterized their transparency properties, then we measured their single-pass second harmonic conversion efficiencies with both a low average power and a high average power nanosecond pulsed lasers. We show that both crystals have comparable linear absorption and conversion efficiencies at low power, whereas in a high power experiment, the CZ-grown BBO yields higher conversion efficiency than the TSSG grown BBO. With a 30 W, 150 kHz, 8 ns green laser, the use of a CZ BBO led at best to a 40% increase in available average output power at 257 nm.

Figure optionsDownload as PowerPoint slide