Thermal Diffusivities Studied by Single-Particle Photothermal Deflection Microscopy

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Using a fixed pump beam and a steerable probe beam, we image the thermal lens generated by a harmonically heated gold nanoparticle using photothermal deflection. In combination with a simple geometric optics model, we extract thermal diffusivities. The measurement technique is applied to reveal the anisotropic thermal conductivity of a nematic liquid crystal. As the measurement is highly local, it paves the way for applications in heterogeneous and anisotropic nanoscale thermal transport studies in complex biological systems.