Optical frequency conversion in semiconductor nanophotonic devices usually imposes stringent requirements on fabrication accuracy and etch surface roughness. Here, we adopt the concept of bound-state-in-continuum (BIC) for waveguide frequency converter design, which obviates the limitations in nonlinear material nano-fabrication and requires to pattern only a low-refractive-index strip on the nonlinear slab. Taking gallium phosphide (GaP) as an example, we study second-harmonic generation using horizontally polarized pump light at 1.55 µm phase matching to vertically polarized BIC modes. A theoretical normalized frequency conversion efficiency of $1.1 \times {10^4}\% \;{{\rm{W}}^{- 1}}{\rm{c}}{{\rm{m}}^{- 2}}$ is obtained using the fundamental BIC mode, which is comparable to that of conventional GaP waveguides.

中文翻译：

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使用连续束缚态在纳米波导中进行频率转换

半导体纳米光子器件中的光频率转换通常对制造精度和蚀刻表面粗糙度提出了严格的要求。在这里，我们采用波导管变频器设计的连续状态约束（BIC）概念，从而消除了非线性材料纳米制造中的局限性，只需要在非线性平板上图案化低折射率带。以磷化镓（GaP）为例，我们研究了使用1.55 µm相位的水平偏振泵浦光与垂直偏振BIC模式匹配的二次谐波产生。理论归一化的频率转换效率为$ 1.1 \ times {10 ^ 4} \％\; {{\ rm {W}} ^ {-1}} {\ rm {c}} {{\ rm {m}} ^ { -2}} $ 使用基本的BIC模式可得到与传统GaP波导相当的频率。