Beetar John E, Nrisimhamurty M, Truong Tran-Chau, Nagar Garima C, Liu Yangyang, Nesper Jonathan, Suarez Omar, Rivas Federico, Wu Yi, Shim Bonggu, Chini Michael
Department of Physics, University of Central Florida, Orlando FL 32816, USA.
Department of Physics, Applied Physics and Astronomy, Binghamton University, Binghamton NY 13902, USA.
Sci Adv. 2020 Aug 21;6(34). doi: 10.1126/sciadv.abb5375. Print 2020 Aug.
The field of attosecond science was first enabled by nonlinear compression of intense laser pulses to a duration below two optical cycles. Twenty years later, creating such short pulses still requires state-of-the-art few-cycle laser amplifiers to most efficiently exploit "instantaneous" optical nonlinearities in noble gases for spectral broadening and parametric frequency conversion. Here, we show that nonlinear compression can be much more efficient when driven in molecular gases by pulses substantially longer than a few cycles because of enhanced optical nonlinearity associated with rotational alignment. We use 80-cycle pulses from an industrial-grade laser amplifier to simultaneously drive molecular alignment and supercontinuum generation in a gas-filled capillary, producing more than two octaves of coherent bandwidth and achieving >45-fold compression to a duration of 1.6 cycles. As the enhanced nonlinearity is linked to rotational motion, the dynamics can be exploited for long-wavelength frequency conversion and compressing picosecond lasers.
阿秒科学领域最初是通过将强激光脉冲非线性压缩至两个光学周期以下的持续时间而得以实现的。二十年后，要产生如此短的脉冲，仍需要最先进的少周期激光放大器，以便最有效地利用稀有气体中的“瞬时”光学非线性来实现光谱展宽和参量频率转换。在此，我们表明，当由比几个周期长得多的脉冲在分子气体中驱动时，由于与旋转取向相关的光学非线性增强，非线性压缩可以效率更高。我们使用工业级激光放大器产生的80周期脉冲，在充气毛细管中同时驱动分子取向和超连续谱产生，产生超过两个倍频程的相干带宽，并实现了>45倍的压缩，达到1.6个周期的持续时间。由于增强的非线性与旋转运动相关联，这种动力学可用于长波长频率转换和压缩皮秒激光。
