Time-resolved ellipsometry for studies of heat transfer at liquid/solid and gas/solid interfaces

Chang Ki Min, David G. Cahill, Steve Granick

Research output: Contribution to journalArticle

Abstract

We describe a sensitive method for measuring time-dependent changes in refractive index within ∼5 μm of an interface using off-null time-resolved ellipsometry and a dual-cavity femtosecond laser. The sensitivity to changes in refractive index is two orders of magnitude higher than conventional picosecond interferometry. A thin metal film on a sapphire substrate is heated by ∼10 K using an ultrafast optical pump pulse; the subsequent changes of the phase difference δ Δ between p and s polarized reflectivity are tracked using off-null ellipsometry using a time-delayed probe pulse. We demonstrate a sensitivity of δ Δ≈3× 10-7 deg/Hz using interfaces between Au and water, and Au and various gases including R134a, a common refrigerant. Our data for the damping rate of ≈200 MHz frequency acoustic waves in O2, N 2, and Ar at atmospheric pressure agree well with prior results obtained at much lower pressures and frequencies.

Original languageEnglish (US)
Article number074902
JournalReview of Scientific Instruments
Volume81
Issue number7
DOIs
StatePublished - Jul 1 2010

ASJC Scopus subject areas

  • Instrumentation

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