Advances in femtosecond single-crystal sum-frequency generating optical parametric oscillators

Reports on recent advances on the femtosecond single-crystal sum-frequency generating OPO. Our OPO is based on a KTP (KTiOPO/sub 4/) crystal that is cut for noncritical phase matching (NCPM), and synchronously-pumped by a Ti:sapphire laser operating at a wavelength of 828 nm. At this wavelength, the KTP crystal is phase matched for a signal wavelength of 1175 nm in a type-II geometry; the corresponding idler wavelength is 2.8 /spl mu/m. The KTP crystal is also phase matched for SFG of the pump and the signal beams to yield a blue output beam at 487 nm. However, a polarization rotation of the pump beam at the OPO input is necessary for this interaction to occur.