A new photothermal technique is proposed. This is based on the temperature characteristic of the dielectric constant of light-irradiated material. When a dielectric material is illuminated with chopped light, alternating 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 presented for the alternating capacitance variation in terms of the optical, thermal, dielectric and geometric parameters of the system. Next, some fundamental experiments on the photothermal dielectric spectroscopic microscope (PTDSM) to confirm the validity of this theoretically predicted photothermal dielectric signal are performed, and it is shown 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 microscope, the temperature characteristics of the dielectric materials for microwave application are successfully measured.
ASJC Scopus subject areas
- Physics and Astronomy(all)