Departamento Ingeniería de Comunicaciones, ETSI Telecomunicación, Universidad de Málaga, 29071 Málaga, Spain.
Opt Lett. 2012 Sep 1;37(17):3663-5. doi: 10.1364/OL.37.003663.
Grating couplers are a promising approach to implement efficient fiber-chip coupling. However, their strong polarization dependence makes dual-polarization operation challenging. In this Letter we propose, for the first time, a polarization-independent grating coupler for thick rib silicon-on-insulator (SOI) waveguides. Coupling efficiency is optimized by designing the grating pitch and duty cycle, without varying the bottom oxide thickness, which significantly simplifies practical implementation. Directivity of the grating coupler is enhanced by a high reflectivity layer under the bottom oxide after the selective removal of the Si substrate. Dual-polarization coupling efficiency of -2.8 dB is shown.
光栅耦合器是实现高效光纤-芯片耦合的一种很有前途的方法。然而，它们强烈的偏振依赖性使得双偏振操作具有挑战性。在本信中，我们首次提出了一种用于厚脊硅-绝缘体（SOI）波导的偏振无关光栅耦合器。通过设计光栅节距和占空比来优化耦合效率，而不改变底部氧化物的厚度，这大大简化了实际实现。在选择性去除硅衬底后，在底部氧化物下增加一层高反射率层，提高了光栅耦合器的定向性。实验展示了双偏振耦合效率为-2.8dB。
