Measurements of the refractive indices and thermo-optic coefficients of Si3N4 and SiOx using microring resonances

Amir Arbabi, Lynford L Goddard

Research output: Contribution to journalArticle


We present a method for determining the core and cladding refractive indices of a microring resonator from its measured quasi-transverse electric and magnetic resonant modes. We use single wavelength reflective microrings to resolve the azimuthal order ambiguity of the measured resonances. We perform accurate electromagnetic simulations to model the dependence of the resonances on geometrical and material parameters. We linearize the model and use the singular value decomposition method to find the best fit parameters for the measured data. At 1550 nm, we determine nSi3N4 = 1.977 ± 0.003 for stoichiometric silicon nitride deposited using low-pressure chemical vapor deposition (LPCVD) technique and nSiOx = 1.428 ± 0.011 for plasma-enhanced chemical vapor deposition (PECVD) oxide. By measuring the temperature sensitivities of microring resonant modes with different polarizations, we find the thermo-optic coefficient of the stoichiometric silicon nitride to be dnSi3N4/dT = (2.45 ± 0.09) × 10-5 (RIU/°C) and the PECVD oxide to be dnSiOx/dT = (0.95 ± 0.10) × 10-5 (RIU/°C).

Original languageEnglish (US)
Pages (from-to)3878-3881
Number of pages4
JournalOptics Letters
Issue number19
StatePublished - Oct 1 2013

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics

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