PHOTOTHERMAL DIELECTRIC SPECTROSCOPIC MICROSCOPE

A new photothermal technique is proposed. It is based on the temperatu re characteristic of the dielectric constant of light-irradiated mater ial. When chopped light is absorbed in a dielectric material, an alter nating variation of capacitance is caused by the heat produced due to light absorption and is detected by using a frequency demodulation tec hnique. A quantitative derivation is presented for the alternating cap acitance variation in terms of the optical, thermal, dielectric, and g eometric parameters of the system. The experimental results for lead z irconate titanate ceramics, barium titanate single-crystal, TiO2-Bi2Ti 4O11 ceramics, and ethyl alcohol are shown, where the observed signals agree with theoretical ones very well. (C) 1996 American Institute of Physics.