High efficiency binary blazed grating coupler for perfectly-vertical and near-vertical coupling in chip level optical interconnections

The high-efficiency binary blazed grating couplers with perfectly vertical and nearly vertical coupling are proposed. The efficiencies of them are much higher than those of other types of grating couplers without bottom mirrors under vertical and oblique incidence respectively. For perfectly vertical coupler with transverse-electric polarized incident light, the coupling efficiency, which is defined as the ratio between the power coupled to the fundamental mode of the chip waveguide and that carried by the fundamental mode of the input optical fiber, is 75%, while the nearly vertical coupler with the incident angle of 10.2° has a coupling efficiency of 84%. Rigorous coupled-wave diffraction analysis and a complete optimization method have been used to make the optimal design valid and unique.