Fast, spatially resolved thermometry of Si and GaP crystals using pump-probe two-photon absorption

Chang Ki Min, Ji Yong Park, David G. Cahill, Steve Granick

Research output: Contribution to journalArticle

Abstract

Noncontact thermometry with micron-scale lateral spatial resolution and fast time resolution is shown to be enabled by measuring the temperature dependence of two-photon absorption (TPA) on crystalline semiconductors. In the proof-of-concept experiments reported here, for studies of Si, an Er:fiber laser at λ=1.56 μm is split into pump and probe beams; where they overlap, the large TPA signal changes strongly with temperature because the two-photon energy lies between the indirect and direct bandgaps of Si. We show that the TPA coefficient increases by a factor of 2 when the temperature increases from 30 to 300 °C. For studies of GaP, we use instead a Ti:sapphire laser at 790 nm to achieve two-photon excitation above the direct bandgap. In GaP, contributions to the TPA from the dominant direct transition show less temperature dependence than for Si but the additional contribution of the indirect transition gives a similar magnitude as the temperature dependence of TPA on Si. In the current implementation using Si, the spatial resolution of the thermometry is 6×6×50 μ m3 and the sensitivity is 0.6 K in a 1 kHz bandwidth.

Original languageEnglish (US)
Article number013102
JournalJournal of Applied Physics
Volume106
Issue number1
DOIs
StatePublished - Jul 24 2009

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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