Ng Jason C, Herman Peter R, Qian Li
Opt Lett. 2017 Jan 15;42(2):195-198. doi: 10.1364/OL.42.000195.
Second harmonic generation (SHG) is demonstrated in femtosecond laser written waveguides in fused silica through a combination of thermal poling and laser-based quasi-phase-matching (QPM) techniques. Quasi-phase-matching was controlled by the periodic erasure of induced nonlinearity through femtosecond laser erasure. A maximum SHG conversion efficiency of 6.6±0.5×10%/W is reported for the fundamental wavelength of 1552.8 nm with a phase-matching bandwidth of 4.4 nm for a 10.0 mm long waveguide. For a shorter sample, an effective second-order nonlinearity of χ=0.012±0.001 pm/V was measured. Chirped QPM structures for wider SHG bandwidths also were demonstrated. Such periodically poled waveguides are promising for introducing nonlinear optical components within the 3D passive optical circuits that can be flexibly formed in fused silica by femtosecond laser writing.
通过热极化和基于激光的准相位匹配（QPM）技术相结合，在飞秒激光写入的熔融石英波导中实现了二次谐波产生（SHG）。通过飞秒激光擦除诱导非线性的周期性擦除来控制准相位匹配。对于10.0毫米长的波导，在1552.8纳米的基波波长下，报道的最大SHG转换效率为6.6±0.5×10%/W，相位匹配带宽为4.4纳米。对于较短的样品，测量到有效二阶非线性系数χ=0.012±0.001 pm/V。还展示了用于更宽SHG带宽的啁啾QPM结构。这种周期性极化波导有望在三维无源光电路中引入非线性光学元件，这些电路可以通过飞秒激光写入在熔融石英中灵活形成。
