Opt Lett. 2019 Mar 15;44(6):1343-1346. doi: 10.1364/OL.44.001343.
We experimentally study filamentation and supercontinuum generation in bulk silicon crystal using femtosecond mid-infrared pulses with carrier wavelengths in the range of 3.25-4.7 μm, in the presence of three-, four-, and five-photon absorption. Spectral measurements show a fairly stable blueshifted cutoff in the 2.5-2.7 μm range and gradual increase of the long-wave extent with increasing wavelength of the incident pulses, eventually yielding an octave-spanning supercontinuum, covering the wavelength range from 2.5 to 5.8 μm with the input pulses at 4.7 μm. The recorded spatiotemporal intensity distributions of a single filament revealed pulse splitting after the nonlinear focus, in line with the pulse-splitting-based filamentation scenario inherent to normally dispersive dielectric nonlinear media.
我们使用载波波长在 3.25-4.7μm 范围内的飞秒中红外脉冲在存在三、四和五光子吸收的情况下在体硅晶体中实验研究了细丝化和超连续谱产生。光谱测量显示在 2.5-2.7μm 范围内相当稳定的蓝移截止，并且随着入射脉冲波长的增加，长波范围逐渐增加，最终产生了一个覆盖波长范围从 2.5μm 到 5.8μm 的倍频程超连续谱，输入脉冲在 4.7μm 时。单个细丝的记录时空强度分布显示出非线性焦点后的脉冲分裂，这与正常色散介电非线性介质固有的基于脉冲分裂的细丝化场景一致。
