Comparison of the photothermal sensitivity of an interferometric optical fiber probe with pulsed photothermal radiometry

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Abstract
An interferometric optical fiber probe for making photothermal measurements of tissue optical and thermal properties is compared to pulsed photothermal radiometry in terms of its overall thermal sensitivity, linearity, and response time. The principles of operation of the probe are described and its performance as a low finesse Fabry–Perot interferometer is discussed. A probe with a 12 μm sensing film is characterized by a thermal noise floor of 50 mK and a response time of 850 μs. The sensitivities to the optical and thermal coefficients of the two techniques have been analyzed. As a result of the different source geometries, the optical fiber probe was found to be more sensitive to the thermal coefficients of tissue than the optical coefficients while pulsed photothermal radiometry provided maximum sensitivity to the optical coefficients.