Low threshold and highly efficient prismless diode-pumped femtosecond Yb:KYW laser

In this paper, we report a highly-efficient and compact passively mode-locked prism less Yb/sup 3+/:KY(WO/sub 4/)/sub 2/ (Yb:KYW) laser pumped by a single-mode laser diode and incorporating a pair of chirped mirrors for positive dispersion compensation. A slope efficiency of up to 62% has been achieved during femtosecond operation and near-transform limited pulses of 180 fs at 1038 nm were produced with an average output power in excess of 90 mW for an incident pump power of just 320 mW.