Considering Photoinduced Second-Harmonic Generation as a dc Kerr Optical Parametric Oscillation or Amplification Process,Physical Review Applied

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Considering Photoinduced Second-Harmonic Generation as a dc Kerr Optical Parametric Oscillation or Amplification Process
Physical Review Applied ( IF 3.8 ) Pub Date : 2021-07-12 , DOI: 10.1103/physrevapplied.16.014027
Xiyuan Lu _{1,

2} , Kartik Srinivasan _{1,

3}

Affiliation

Photoinduced second-harmonic generation (SHG) in centrosymmetric materials like silica and silicon nitride has been commonly explained as an effective second-order (

χ^{(2)}

) process mediated by a dc electric field and the medium’s third-order (

χ^{(3)}

) nonlinearity. In this explanation, the coherent photogalvanic effect is the source of a dc electric field whose spatial periodicity naturally enables quasi-phase-matching. While successful in explaining many observations from experiment, the behavior at low input powers, and in particular, the apparent existence of a threshold for efficient photoinduced SHG observed in some experiments has largely been overlooked theoretically. In this Paper, we reconsider photoinduced SHG within the framework of four-wave mixing (FWM), involving degenerate pump, second-harmonic signal, and dc electric field. We propose a hypothesis that photoinduced SHG is a FWM-mediated dc Kerr optical parametric oscillation or amplification process. This hypothesis can explain the threshold behavior, and moreover, predicts unconventional light amplification, both of which we verify by experiments in silicon-nitride microresonators. Finally, we discuss the physical implications of our work in various platforms and future directions.

中文翻译：

将光致二次谐波产生视为直流克尔光学参数振荡或放大过程

二氧化硅和氮化硅等中心对称材料中的光致二次谐波（SHG）通常被解释为有效的二阶。

χ^{(2)}

) 由直流电场和介质的三阶 (

χ^{(3)}

) 非线性。在这个解释中，相干光电效应是直流电场的来源，其空间周期性自然能够实现准相位匹配。虽然成功地解释了实验中的许多观察结果，但在低输入功率下的行为，特别是在某些实验中观察到的有效光致 SHG 阈值的明显存在在理论上被很大程度上忽略了。在本文中，我们重新考虑了四波混频 (FWM) 框架内的光致 SHG，涉及简并泵浦、二次谐波信号和直流电场。我们提出了一个假设，即光致 SHG 是 FWM 介导的直流克尔光学参数振荡或放大过程。这个假设可以解释阈值行为，此外，还预测了非常规的光放大，我们通过在氮化硅微谐振器中的实验验证了这两者。最后，我们讨论了我们工作在各种平台和未来方向上的物理意义。

更新日期：2021-07-12

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