Wang Haochuan, Alismail Ayman, Barbiero Gaia, Wendl Maximilian, Fattahi Hanieh
Opt Lett. 2017 Jul 1;42(13):2595-2598. doi: 10.1364/OL.42.002595.
The generation of superoctave spectra from the interaction of intense ultrashort optical pulses and cubic nonlinearity is the result of interplay between the dispersion and nonlinearity of a material and various propagation effects. The cubic nonlinearity can be enhanced when it is combined with a quadratic-cascaded nonlinearity, relaxing the requirement on the laser's peak intensity for supercontinuum (SC) generation. In this Letter, we demonstrate and compare the generation of an SC driven from cubic and cascaded quadratic nonlinearities at an anomalous and zero dispersion wavelength (ZDW). We show the filament-free SC generation of femtosecond mid-infrared pulses by harvesting cascaded quadratic nonlinearity and, at ZDW, requires a lower threshold peak intensity and results in a higher power spectral density for the newly generated spectral components. The presented method is a suitable approach for generating multi-octave spectra from low peak-power, high average-power oscillators or a suitable seed for optical parametric amplifiers and multi-octave field synthesizers.
由强超短光脉冲与立方非线性相互作用产生的超倍频程光谱，是材料的色散和非线性以及各种传播效应之间相互作用的结果。当立方非线性与二次级联非线性相结合时，立方非线性可以得到增强，从而放宽了对产生超连续谱（SC）所需激光峰值强度的要求。在本信函中，我们展示并比较了在反常色散波长和零色散波长（ZDW）处由立方非线性和级联二次非线性驱动产生的超连续谱。我们通过利用级联二次非线性展示了飞秒中红外脉冲的无细丝超连续谱产生，并且在零色散波长处，所需的阈值峰值强度更低，新产生的光谱成分具有更高的功率谱密度。所提出的方法是一种从低峰值功率、高平均功率振荡器产生多倍频程光谱的合适方法，或者是用于光参量放大器和多倍频程场合成器的合适种子。
