Optical properties of an EM1 IQCsSb bialkali photocathode

A measurement of the angular and polarisation dependence of the reflectance of an EM1 9124B KaCsSb bialkali photocathode, with the photomultiplier immersed in water, has allowed an unambiguous determination of the KzCsSb complex refractive index (2.7 f 0.1 + i( 1.5 f 0.1) at 442 nm wavelength) and thickness (23 f 2 nm) The wavelength dependence of the refractive index has been obtained from a m-analysis of “three intensities” data from Timan [H. Timan, Optical characteristics and constants of high efficiency photoemitters, Revue Technique Thomson-CSF 8 ( 1976) 491. A detailed study of KlCsSb optical properties (absorptance, reflectance and transmittance) has been performed using the above results as reference points.