In this paper, we report experimental evidence of forward optical parametric oscillations (OPOs) with multi frequencies conversion processes in a spectral range of 400 nm–1700 nm using nonlinear photonic crystals of periodically poled LiTaO₃ without external mirrors. The highly polished end-facets of the samples act as a Fabry–Perot cavity mirrors making the device simple and compact. Oscillation thresholds were found of 97.6 MW cm⁻² and 160 MW cm⁻² for the 1D and 2D samples, respectively. Moreover, at pump energies above the threshold, optical oscillations of multiple frequencies due to cascaded interactions established within the samples are obtained. In particular, we point-out the generation of two pairs of signal and idler (OPO1 and OPO2) in the same nonlinear photonic crystal. It is found that the second pair OPO2 appears with different quasi-phase matching conditions induced by a local refractive index variation. Our analysis indicates that this index variation results from a competing effect between quadratic cascading and electro-optic induced refractive index changes.

在本文中，我们报告了使用周期性极化 LiTaO ₃非线性光子晶体在 400 nm–1700 nm 光谱范围内进行多频率转换过程的前向光学参量振荡 (OPO) 的实验证据，而无需外部反射镜。样品的高度抛光端面充当 Fabry-Perot 腔镜，使设备简单紧凑。发现振荡阈值为 97.6 MW cm ^-2和 160 MW cm ^-2分别用于一维和二维样本。此外，在高于阈值的泵浦能量下，由于在样品内建立的级联相互作用，可以获得多个频率的光学振荡。我们特别指出在同一个非线性光子晶体中产生两对信号和惰轮（OPO1 和 OPO2）。发现第二对 OPO2 出现在由局部折射率变化引起的不同准相位匹配条件下。我们的分析表明，这种折射率变化源于二次级联和电光诱导折射率变化之间的竞争效应。