[16a-F202-1~14] 3.11 Photonic structures and phenomena

[16a-F202-8] H1 photonic crystal nanocavity with an ultrahigh Q/V value

〇Eiichi Kuramochi^1,2, Jun-Ki Kim², Hideaki Taniyama^1,2, Akihiko Shinya^1,2, Shota Kita², Masaya Notomi^1,2 (1.NTT-NPC, 2.NTT-BRL)

Keywords:photonic crystal, optical cavity, silicon photonics

In this study, we explored a cavity design that can concentrate the electric field to one electric field antinode filling out a small slot. The H1 nanocavity is known to have a monopole mode with an antinode just on the center point defect. Here, we report on utilizing an H1 nanocavity with a narrow slot placed just at the center. We revealed that this design can focus the electronic field of the monopole-mode to an antinode sharing the short sub-wavelength air-slot. By employing the multi-hole-shifting, we can enhance Q factor to ~10⁶ with keeping mode volume (V) around 0.02 (λ/n)³ according to the FDTD simulation. We fabricated the Si H1 slot nanocavities using electron beam lithography as the design optimized by the simulation. The Q of the cavity modes was strongly dependent on the slot dimension that was also found in the simulation. No high-Q mode was found without the slot. By setting the slot size appropriately, we obtained loaded Q of the monopole mode higher than 2×10⁵ which is the highest Q factor in all slotted nanocavities. Assuming a theoretical value of V~0.02 (λ/n)³ obtained using FDTD, the Q/V was found to be over 1.0×10⁷, which is the highest value reported for 2D PhC cavities.