Abstract

Ti: sapphire-pumped noncritically-phase-matched optical parametric oscillators (OPOs) based on the new nonlinear crystal RbTiOAsO₄ (RTA) offer tuning in the 1.3µm wavelength region, which cannot be accessed by using KTP without resorting to critical phasematching or pump wavelengths longer than 900 nm. The only previously reported RTA femtosecond OPO¹ used noncollinear critical phasematching. By using a 2-mm-thick crystal configured in a type-II (→o+e) noncritical geometry, we avoid problems associated with Poynting-vector walkoff and maximize the available nonlinear coefficient. Using this crystal in an OPO configured without intracavity frequency doubling, we have already demonstrated low-threshold operation for average pump powers as low as 50 mW.²

© 1995 Optical Society of America