Large pulse delay and small group velocity achieved using ultrahigh-Q photonic crystal nanocavities

Takasumi Tanabe, Masaya Notomi, Eiichi Kuramochi, Hideaki Taniyama

Research output: Contribution to journalArticlepeer-review

49 Citations (Scopus)


We systematically studied the spectral and temporal characteristics of wavelength-sized ultrahigh-Q photonic crystal nanocavities based on width-modulated line defects. By employing accurate measurements, we confirmed that the cavity exhibits an ultra-sharp resonance width (1.23 pm), an ultrahigh-Q (1.28 × 106), and an ultra-long photon lifetime (1.12 ns). We discussed the correlation between the spectral and temporal measurements for various cavities, and obtained extremely good agreement. In addition, we demonstrated photon trapping for the side-coupling configuration by employing ring-down measurement, which sheds light on another interesting aspect of this phenomenon. Finally, we performed pulse propagation experiments for samples with different waveguide-cavity coupling configurations, and achieved a smallest group velocity of about 4.6 km/s for a novel configuration. These results show that we can effectively trap and delay light by using ultra-small cavities, which can potentially increase the packing density of optical buffers and bit-shifters if applied to coupled-cavity waveguides.

Original languageEnglish
Pages (from-to)7826-7828
Number of pages3
JournalOptics Express
Issue number12
Publication statusPublished - 2007 Jun 11
Externally publishedYes

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics


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