Highly Accurate Docking of a Photonic Crystal Nanolaser to a SiN_x Waveguide by Transfer Printing

We propose and demonstrate an improved method for transfer printing that allows for the accurate docking of a photonic crystal nanobeam (NB) laser onto a SiN_x waveguide. Our proposed method enables achieving much smaller transfer printing misalignments compared to the conventional approach based on visual alignment in experiments. We tested our method by docking a modified NB laser design with a theoretical unidirectional coupling efficiency of 64% to the SiN_x waveguide. The results show a mean rotational misalignment of only 0.08° and a mean displacement misalignment of 26 nm for 48 NB lasers docked at the SiN_x waveguides, demonstrating the high accuracy and excellent transfer printing reproducibility of our proposed method. Additionally, measurements indicated that over 97% of these highly accurate docked NB lasers exhibited uniform unidirectional coupling to specific waveguide output facets. We believe that the improved transfer printing steps presented in this study, along with the corresponding hybrid integration of docking NB lasers at the SiN_x waveguide, provide a highly promising method for accurately integrating nanowire-based light sources into silicon-based photonic integrated circuits.