Impact of BaB 2 O 4 growth method on frequency conversion to the deep ultra-violet

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, 8ns green laser, the use of a CZ BBO led at best to a 40% increase in available average output power at 257 nm.