Optical response of single-crystal (La,Ca)MnOδ thin films

(La,Ca)MnOδ thin film can be used as a bolometer operated over a wide temperature range around its metal–semiconductor transition where its resistance (R) changes rapidly. This material has a high optical absorption coefficient over a broad wavelength range and is chemically stable in air. We measured the optical response of single-crystal (La,Ca)MnOδ thin films to a He–Ne laser (632.8 nm) as a function of temperature (T), light modulation frequency (f), bias current (I), and laser power (P). The temperature dependence of the measured signal follows the dR/dT curve and the signal depends linearly on I and P. These results indicate that the response is mainly bolometric. Room temperature operation is possible if the sample composition and oxygen stoichiometry are adjusted appropriately.