THEORETICAL AND EXPERIMENTAL STUDIES OF PHOTOTHERMAL DIELECTRIC SPECTROSCOPIC MICROSCOPE

A new photothermal technique is proposed. This is based on the tempera ture characteristic of the dielectric constant of light-irradiated mat erial. When a dielectric material is illuminated with chopped light, a lternating variation of capacitance is caused by the heat produced due to light absorption, and this variation is detectable with sufficient dynamic range and sensitivity. First, quantitative derivations are pr esented for the alternating capacitance variation in terms of the opti cal, thermal, dielectric and geometric parameters of the system. Next, some fundamental experiments on the photothermal dielectric spectrosc opic microscope (PTDSM) to confirm the validity of this theoretically predicted photothermal dielectric signal are performed, and it is show n that the observed signals agree with the theoretical ones very well. Finally, a highly sensitive PTDSM using the coaxial cavity resonator with operating frequency of microwave range is developed. Using this m icroscope, the temperature characteristics of the dielectric materials for microwave application are successfully measured.