Design of ultrahigh-quality-factor photonic crystal nanocylinder cavities

We propose and theoretically investigate a novel one-dimensional photonic crystal nanocylinder cavity (PCNC) that can support the second-order transverse-electric-like (TE₂) mode. Three-dimensional finite-difference time-domain simulations show that the TE₂ mode of the PCNC possesses an ultrahigh quality factor of 1.22 × 10⁸ and a small mode volume of $0.98(\lambda /n{)}^3$ when the PCNC is made of high-index material of silicon. For the PCNCs which are made of low-index materials, the corresponding quality factors of TE₂ modes reach the highest values relative to previously demonstrated PhC nanobeam cavities with the same low-index materials to the best of our knowledge. We believe the PCNC will be a highly promising candidate for low-threshold high-speed nanoscale lasers and cavity optomechanics. (letter)