Kerr nonlinear index is a parameter in nonlinear optics that quantifies the intensity-dependent change in the refractive index of a material.
Pockels coefficient indicates linear change in the refractive index of certain materials when subjected to an external electric field.
Absorption rate
Qabs = ω/κab
Modulation Transfer Spectroscopy was used here. The pump laser modulates the system (through thermal effects, Kerr nonlinearity, or absorption), this modulation transfers to the probe laser which is phase-modulated and tuned near a different resonance frequency to detect the system's response.
At low-frequency, photothermal effect dominates, here heating caused by absorption induces changes in the refractive index and at high-frequency Kerr effect dominates.
BaTiO3 has a higher Kerr nonlinear index and Pockels coefficient r than SiO2, Si3N4, LiNbO3, material absorption-loss Qabs is lower comparative to other materials.
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