Diode-pumped few-optical-cycle laser based on an ytterbium-doped disordered strontium yttrium borate crystal

We report on a power-scalable, diode-pumped sub-20-fs mode-locked (ML) laser based on a multisite ytterbium-doped strontium yttrium borate crystal, Yb:Sr₃Y₂(BO₃)₄, exhibiting broadband spectral gain. Pumping with a low-power, spatially single-mode laser diode, the Yb:Sr₃Y₂(BO₃)₄ laser produces soliton pulses as short as 19 fs at 1073.1 nm via soft-aperture Kerr-lens mode locking. A record-high average output power of 131 mW for such pulse durations represents a sixfold increase compared to the previous work. Peak pulse powers as high as ∼140 kW were achieved, increasing the average output power to 328 mW at 1070.5 nm for a slightly longer pulse duration of 28 fs. This corresponds to an impressive laser efficiency of 30%. The results highlight the potential of diode-pumped ytterbium lasers operating in the few-optical-cycle regime for achieving simultaneously high average output power and laser efficiency.