Etching-free fabrication and integration of 45° micro-mirror for surface-compatible photonic packaging

we demonstrate how micro-mirrors can enable surface-normal coupling of light to a photonic integrated circuit (PIC) equipped with edge couplers. Most micro-mirrors are fabricated using etching techniques with a crystallographic direction dependency, long processing times, and high fabrication costs. This study fabricates a 45 ± 2° etching-free micro-mirror at the wafer level using dicing and e-beam metal evaporation methods. The root-mean-square (RMS) surface roughness of Au-deposited diced μ-mirror is as low as 9 ± 0.65 nm with an angular profile of 45 ± 2°, resulting in a 2.7 ± 0.2 dB reflectance loss. The diced micro-mirrors are integrated into a PIC with edge couplers for demonstrating the surface-compatible pluggable connection between the PIC and fiber array. Overall transmission loss from the laser source-PIC-lensed fiber array is -6.06 dB at 1550 nm with ultra-relaxed 1dB alignment tolerance of ±35 μm. The method described in this paper can be scaled to higher-volume manufacturing and wafer-level integration of the μ-mirror and μ-lens array onto a PIC.