As devices utilizing femtosecond-duration laser pulses become more commonplace, there is a need for next-generation nonlinear-photonics technologies that enable low-energy femtosecond pulses to be converted from one wavelength to another with high efficiency. However, designing nonlinear materials to operate with femtosecond pulses is challenging, because it is necessary to match both the phase velocities and group velocities of the light. Here, we show that femtosecond laser pulses can generate self-organized nonlinear gratings in nanophotonic waveguides, thereby providing a nonlinear optical device with both quasi-phase-matching and group-velocity matching for second-harmonic generation. We use nonlinear microscopy to uniquely characterize the self-organized nonlinear gratings and demonstrate that these waveguides enable simultaneous χ⁽²⁾ and χ⁽³⁾ nonlinear processes for laser-frequency-comb stabilization. Finally, we derive the equations that govern self-organized grating formation for femtosecond pulses and uncover the crucial role of group-velocity matching. In the future, nanophotonics with self-organized gratings could enable scalable, reconfigurable nonlinear photonics.

随着使用飞秒持续时间激光脉冲的设备变得越来越普遍，需要下一代非线性光子学技术，该技术能够将低能量的飞秒脉冲从一个波长高效转换为另一个波长。但是，设计非线性材料以使用飞秒脉冲工作是一项挑战，因为必须使光的相速度和群速度都匹配。在这里，我们表明飞秒激光脉冲可以在纳米光子波导中生成自组织的非线性光栅，从而为二次谐波生成提供了一种具有准相位匹配和群速度匹配的非线性光学器件。我们使用非线性显微镜来唯一表征自组织的非线性光栅，并证明这些波导能够实现同步激光频率梳稳定的χ ^（2）和χ ^（3）非线性过程。最后，我们推导了控制飞秒脉冲自组织光栅形成的方程式，并揭示了群速度匹配的关键作用。将来，具有自组织光栅的纳米光子学可以实现可扩展，可重构的非线性光子学。