Akinari Fujita | Searcharxiv

arXiv2026

Quantum dot single photon source on SiN integrated with coupled crossover waveguides

Hybrid integration of InAs/GaAs quantum dot (QD) single-photon sources (SPSs) is a promising approach for introducing quantum light into SiN photonic integrated circuits. However, the large refractive-index mismatch between GaAs and SiN poses a challenge for efficient optical coupling. Here, we propose and experimentally demonstrate hybrid integration of an InAs/GaAs QD-SPS on SiN using a coupled crossover waveguide structure. A photonic crystal nanocavity is employed for coupling QD emission into a GaAs waveguide, which efficiently transfers photons to a SiN waveguide at the crossover section. We observed Purcell-enhanced single-photon emission, on-chip propagation, and outcoupling through a SiN grating coupler.

physics.optics↗

arXiv2023

High-Q two-dimensional photonic crystal nanocavity on glass with an upper glass thin film

We numerically analyze two-dimensional photonic crystal (PhC) nanocavities on glass with a thin glass film on top of the structure. We investigated a multi-step heterostructure GaAs PhC nanocavity located on glass. We found that covering the structure even with a very-thin glass film efficiently suppresses unwanted polarization mode conversion occurring due to the asymmetric refractive index environment around the PhC. We also uncovered that the glass-covered structure can exhibit a higher Q factor than that observed in the structure symmetrically cladded with thick glass. We point out that the mode mismatch between the PhC nanocavity and modes in the upper glass film largely contributed to the observed Q-factor enhancement. These observations were further analyzed through the comparison among different types of on-glass PhC nanocavites covered with thin glass films. We also discuss that the in-plane structure of the upper glass film is important for additionally enhancing Q factor of the nanocavity.

physics.optics↗