Study on the second-harmonic generation during the application of a low-Frequency AC field In KTiOPO₄ crystals

Abstract

Since there is birefringence, two linear polarization rays (e _l and e ₂) be generated for a given incident light. Here n^e₁ >n^e₂ . Although a second-harmonic beam corresponding to the refractive index n^e₁ (e^2ω ₁ ray) can not be generated in a biaxial crystal in usual conditions, it is observed in biaxial crystal of KTiOPO₄ when a low-frequency ac field is applied in the c-axis of the crystal. We measured the intensity of the e^2ω ₁ ray versus ac field frequency response. It is considered that this effect is induced by the quasi-one-dimensional ionic conductance in KTiOPO₄ crystals.