Ultrahigh-Q photonic crystal nanocavities realized by the local width modulation of a line defect

TLDR

The authors propose an ultrahigh‑Q photonic crystal slab nanocavity created by locally modulating the width of a line defect. The cavity is realized by widening the line defect within the photonic crystal slab. Numerical simulations predict an intrinsic Q up to 7×10⁷, and experimental measurements of fabricated Si nanocavities coupled to waveguides show a loaded Q of ~8×10⁵, confirming the ultrahigh‑Q performance and demonstrating that shifting two holes away from the defect suffices to achieve this high Q.

Abstract

We propose an ultrahigh quality factor (Q) photonic crystal slab nanocavity created by the local width modulation of a line defect. We show numerically that this nanocavity has an intrinsic Q value of up to 7×107. Transmission measurements for fabricated Si photonic-crystal-slab nanocavities directly coupled to input/output waveguides have exhibited a loaded Q value of ∼800000. These theoretical and experimental Q values are very high for photonic crystal nanocavities. In addition, we demonstrate that simply shifting two holes away from a line defect is sufficient to achieve an ultrahigh Q value both theoretically and experimentally.