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

(La,Ca)MnOdelta 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)MnOdelta 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. (C) 1996 American Institute of Physics.