Roland Iännis, Ravaro Marco, Suffit Stéphan, Filloux Pascal, Lemaître Aristide, Favero Ivan, Leo Giuseppe
MPQ, Université de Paris & CNRS, 10 rue A. Domon et L. Duquet, 75013 Paris, France.
C2N, CNRS, Université Paris-Saclay, 10 boulevard T. Gobert, 91120 Palaiseau, France.
Micromachines (Basel). 2020 Feb 23;11(2):229. doi: 10.3390/mi11020229.
Due to adjustable modal birefringence, suspended AlGaAs optical waveguides with submicron transverse sections can support phase-matched frequency mixing in the whole material transparency range, even close to the material bandgap, by tuning the width-to-height ratio. Furthermore, their single-pass conversion efficiency is potentially huge, thanks to the extreme confinement of the interacting modes in the highly nonlinear and high-refractive-index core, with scattering losses lower than in selectively oxidized or quasi-phase-matched AlGaAs waveguides. Here we compare the performances of two types of suspended waveguides made of this material, designed for second-harmonic generation (SHG) in the telecom range: (a) a nanowire suspended in air by lateral tethers and (b) an ultrathin nanorib, made of a strip lying on a suspended membrane of the same material. Both devices have been fabricated from a 123 nm thick AlGaAs epitaxial layer and tested in terms of SHG efficiency, injection and propagation losses. Our results point out that the nanorib waveguide, which benefits from a far better mechanical robustness, performs comparably to the fully suspended nanowire and is well-suited for liquid sensing applications.
由于可调节的模态双折射，具有亚微米横向截面的悬浮式 AlGaAs 光波导可以通过调整宽高比，在整个材料透明范围内，甚至接近材料带隙时，支持相位匹配的频率混合。此外，由于相互作用模式在高度非线性和高折射率的纤芯中受到极度限制，其单通转换效率可能非常高，且散射损耗低于选择性氧化或准相位匹配的 AlGaAs 光波导。在此，我们比较了由这种材料制成的两种悬浮式光波导的性能，它们专为电信波段的二次谐波产生（SHG）而设计：（a）通过横向系绳悬浮在空气中的纳米线，以及（b）由位于相同材料的悬浮膜上的条带制成的超薄纳米带。这两种器件均由 123 nm 厚的 AlGaAs 外延层制成，并在 SHG 效率、注入和传播损耗方面进行了测试。我们的结果表明，得益于更好的机械鲁棒性，纳米带光波导的性能与完全悬浮的纳米线相当，非常适合液体传感应用。
