Coherent Raman Scattering for Localized Thermal Mapping

Coherent Raman scattering (CRS) spectroscopy is explored as a tool for obtaining localized temperature measurements. A single femtosecond oscillator is used to pump a photonic crystal fiber to provide a broadband Stokes pulse. The CRS signals from the broad OH-stretching modes between 3000 and 3700 cm(-1) are recorded for water at different temperatures. The shapes of these two modes are shown to correlate with water temperature. As a multi-wave process, excitation is limited to only the focal volume giving inherent spatial resolution that allows for mapping of the thermal profile. The local variation of temperature may be mapped so that the localized thermal response from directed energy exposure can be obtained. As these exposures typically have some thermal component, it is important to have a means of specifically characterizing the thermal effects. The thermal portion can then be decoupled from the other effects of the directed energy source so that the non- thermal components are better characterized.