Considering photoinduced second-harmonic generation as a DC Kerr optical parametric oscillation or amplification process
Xiyuan Lu, Kartik Srinivasan
Photo-induced second harmonic generation (SHG) in centro-symmetric materials like silica and silicon nitride has been commonly explained as an effective second-order (chi(2)) process mediated by a DC electric field and the medium's third-order (chi(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, this perspective is incomplete in that it does not provide quantitative predictions of the threshold power for photo-induced SHG, or the origin of amplification in this process. In this letter, we demonstrate how photo-induced SHG can be viewed within the framework of four-wave mixing involving degenerate pump, second harmonic signal, and DC electric field. This DC-Kerr optical parametric oscillation/amplification process explains the threshold behavior of photo-induced SHG, and moreover, predicts unconventional light amplification, both of which we verify by experiments in silicon nitride microresonators.
and Srinivasan, K.
Considering photoinduced second-harmonic generation as a DC Kerr optical parametric oscillation or amplification process, Physical Review Applied, [online], https://doi.org/10.1103/PhysRevApplied.16.014027 , https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=930754
(Accessed February 27, 2024)