Direct generation of ultrashort few-optical-cycle pulses in various wavelength regions has attracted great attention in recent decades. In this paper, generation of less than five-optical-cycle pulses from a Kerr-lens mode-locked ${\rm Yb}{:}{\rm CaYAlO}_4$ laser is demonstrated. Pumped by a 976 nm fiber laser, stable near-Fourier-transform-limited ultrashort soliton pulses centered around 1080 nm with a repetition rate of ${\sim}{113.7}\;{\rm MHz}$ were obtained. The obtained pulses have a pulse duration as short as 17 fs if a ${{\rm Sech}^2}$-shaped pulse profile is assumed, corresponding to about 4.68 optical cycles. To the best of our knowledge, this is the shortest pulse directly generated from mode-locked rare-earth-doped solid-state oscillators.

中文翻译：

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Kerr透镜锁模Yb：CaYAlO ₄激光器产生的亚五光周期脉冲

在最近的几十年中，在各种波长范围内直接产生超短的少数光学周期脉冲引起了极大的关注。在本文中，演示了由Kerr透镜锁模的$ {\ rm Yb} {：} {\ rm CaYAlO} _4 $激光器产生的少于五个光学周期的脉冲。在976 nm光纤激光器的激励下，获得了稳定的，经过傅立叶变换限制的超短孤子脉冲，其中心频率约为1080 nm，重复率为$ {\ sim} {113.7} \; {\ rm MHz} $。如果假定具有{{{rm Sech} ^ 2} $形状的脉冲轮廓，则所获得的脉冲具有短至17 fs的脉冲持续时间，对应于大约4.68个光学周期。据我们所知，这是由锁模稀土掺杂固态振荡器直接产生的最短脉冲。