III-V Photonic Crystal Nanobeam Lasers Side-Coupled to Silicon Waveguide by Transfer Printing

We employed a highly accurate transfer printing technique based on mechanically guided alignment to achieve side-coupled hybrid integration structures between different types of photonic crystal (PhC) nanobeam (NB) resonators and silicon waveguides. Both the nanocavity and band-edge resonators theoretically exhibit unidirectional in-plane optical leakages due to an asymmetric PhC lattice design, with nearly 90% theoretical unidirectional coupling efficiency when integrated with silicon waveguides in the side-coupling structure using additional tapered beams. In our measurements, we confirmed significant planar radiation resulting from the unidirectional coupling between both types of NB lasers and silicon waveguides. Furthermore, we investigated the wavelength-dependent coupling characteristics of NB cavity lasers with varying parameters within this integrated framework, as well as their planar lasing emission over long propagation distances when integrated with a U-bend waveguide. These experimental results demonstrate the applicability and feasibility of this side-coupling architecture for integrating nanoscale light sources into silicon-based integrated photonic circuits.