Efficient femtosecond traveling-wave optical parametric amplification in periodically poled KTiOPO₄

Abstract

We report, for the first time to our knowledge, high-power femtosecond traveling-wave optical parametric amplification by use of periodically poled ${\mathrm{KTiOPO}}_4$. With a single pass through a 4-mm-long sample of 1.23-mm thickness we achieved 40% internal conversion efficiency and $5 \mathit{\mu }\mathrm{J}$ of single-pulse idler energy near $3.8 \mathit{\mu }\mathrm{m}$, using only $75 \mathit{\mu }\mathrm{J}$ of energy from the output of a conventional 1-kHz Ti:sapphire regenerative amplifier. The 210-fs-long idler pulses were almost transform limited. We discuss the specific problems encountered in high-power parametric conversion, such as unwanted quasi-phase-matched upconversion processes for polarization configurations that utilize the largest $\left(d_{33}\right)$ nonlinear coefficient and the related formation of color centers (gray tracking) in ${\mathrm{KTiOPO}}_4$.

© 1999 Optical Society of America