Optically Probed Time Dynamics of χ(2) Grating Inscription in SiN Waveguides

Silicon Nitride (S13N4) waveguide platforms have seen significant interest in the recent years, motivated by several advantageous properties such as compatibility with CMOS fabrication standards, low propagation loss, high refractive index and optical nonlinearity suggesting multiple applications in integrated linear and nonlinear optics. Unfortunately, Si
₃
N
₄
does not exhibit second order nonlinear optical properties due to its amorphous nature. Yet, recently several groups showed a build-up in time of a second harmonic (SH) when a pulsed high power pump is coupled in an Si3N waveguide [1-3]. This phenomenon, referred to as all-optical poling, is explained by the growth of an harmonic space-charge modulated χ
⁽²⁾
grating which quasi-phase matches the pump and its SH [4].