Changes in the reflection coefficient of a high-temperature superconducting ceramic NdCeCuO in the visible spectral range under the action of IR radiation pulses

An IBM PC/XT computer was used to develop an automated method for measuring the time dependence of the room-temperature reflection coefficient of a high-temperature superconducting ceramic Nd1.85Ce0.15CuO4-y observed within the focal spot formed by laser radiation, The Excitation was provided by an electric-discharge gasdynamic laser emitting in the wavelength range 16-18 mu m. The radius of the spot was similar to 0.5 mm, the pulse duration was similar to 0.12 s, and the power was similar to 1 W. Measurements of the reflection coefficient were made with the aid of an He-Ne laser generating linearly polarised light which was reflected at the Brewster angle from the ceramic at the centre of the spot illuminated by the gasdynamic laser. During an IR excitation laser pulse the reflection coefficient rose by similar to 4.5%. A comparison with the measured relative change in the reflection coefficient of the same ceramic caused by heating to 300 degrees C gave an estimate of the temperature of the sample which was reached at the focus of the laser spot. This temperature increased by 50 degrees C during one IR pulse, in agreement with the calculated value.